Communication Control Method

Abstract

To provide an early data transmission method and a system that transmit data using a predetermined message during a random access procedure for wireless terminals targeted for machine type communication (MTC) and Internet of things (IoT) to perform efficient communication.SOLUTION: A communication control method comprises a step in which a base station eNB transmits to user equipment UE a first timer value for a random access procedure without early data transmission and a second timer value for a random access procedure with early data transmission, a step in which the user equipment selects the second timer value in response to determining that early data transmission will be performed, and a step in which the user equipment starts a timer set to the second timer value when transmitting uplink data by early data transmission.SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] The present invention relates to a communication control method in a mobile communication system. [Background technology]

[0002] In recent years, wireless terminals for MTC (Machine Type Communication) and IoT (Internet of Things) services, which communicate without human intervention, have been attracting attention. These wireless terminals are required to achieve low cost, extended coverage, and low power consumption. For this reason, 3GPP (3rd Generation Partnership Project) (registered trademark; the same applies hereinafter) has specified a new category of wireless terminals whose transmission and reception bandwidths are limited to only a portion of the system transmission and reception bandwidth. Summary of the Invention

[0003] A communication control method according to one embodiment is a method for a mobile communication system, and includes the steps of: a base station transmitting a system information block (SIB) indicating an allowable data amount allowed to be transmitted in an early data transmission for transmitting uplink user data using a message 3 during a random access procedure; a radio terminal in an RRC idle mode receiving the SIB; and the radio terminal determining to perform the early data transmission when an amount of data to be transmitted to the base station is equal to or less than the allowable data amount indicated by the SIB.

[0004] The communication control method may further include a step in which, after determining to perform the early data transmission, the radio terminal selects a PRACH resource to be used for transmitting a random access preamble from among the PRACH resources for the early data transmission, and a step in which the radio terminal transmits the random access preamble to the base station using the selected PRACH resource.

[0005] In the communication control method, the PRACH resource for early data transmission may be provided for each extended coverage level, and the selecting step may include a step of selecting a PRACH resource corresponding to the extended coverage level applied to the wireless terminal.

[0006] The communication control method may further include a step in which the base station transmits a random access response including an uplink grant to the wireless terminal in response to receiving the random access preamble, and the random access response may include information indicating whether the uplink grant is for the early data transmission.

[0007] The communication control method may further include a step in which the wireless terminal receives the random access response from the base station, and a step in which the wireless terminal cancels the early data transmission if the uplink grant included in the random access response is not for the early data transmission.

[0008] A communication control method according to one embodiment is a communication control method for controlling early data transmission, which is transmission of uplink user data from a base station to a radio terminal during a random access procedure. The communication control method includes the steps of: (A) transmitting, by the base station, to the radio terminal, a first timer value for the random access procedure without the early data transmission and a second timer value for the random access procedure with the early data transmission; (B) selecting, by the radio terminal, the second timer value in response to the radio terminal determining to perform the early data transmission; and (C) starting, by the radio terminal, a timer set to the second timer value when the radio terminal transmits the uplink data through the early data transmission.

[0009] A communication control method according to one embodiment is a communication control method for controlling early data transmission, in which downlink user data is transmitted from a base station to a wireless terminal during a random access procedure. The communication control method includes the steps of: (A) transmitting, by the base station, information regarding a data volume condition for the early data transmission to the wireless terminal; (B) receiving, by the wireless terminal, the information regarding the data volume condition from the base station; (C) estimating, by the wireless terminal, an amount of downlink user data to be received from the base station in the early data transmission; and (D) starting, by the wireless terminal, the early data transmission if the estimated amount of downlink user data satisfies the data volume condition.

[0010] A communication control method according to one embodiment is a communication control method for controlling early data transmission in which a radio terminal transmits or receives user data in an amount equal to or less than a maximum user data amount set by a base station during a random access procedure, the communication control method comprising: a step A in which the radio terminal determines the maximum user data amount recommended by the radio terminal; and a step B in which the radio terminal in an RRC connected mode transmits, to the base station, information indicating the maximum user data amount recommended by the radio terminal. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a configuration of an LTE system (mobile communication system) according to an embodiment. [Figure 2] 1 is a diagram illustrating a configuration of a UE (wireless terminal) according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating a configuration of an eNB (base station) according to the embodiment. [Figure 4] FIG. 1 is a diagram illustrating a protocol stack of a radio interface in an LTE system according to an embodiment. [Figure 5] 1 is a diagram illustrating a configuration of a radio frame of an LTE system according to an embodiment. [Figure 6]FIG. 1 is a diagram showing frequency channels handled by eMTC UE and NB-IoT UE. [Figure 7] A diagram showing a random access procedure for eMTC UE and NB-IoT UE. [Figure 8] FIG. 2 is a diagram showing an operation pattern 1 according to the first embodiment. [Figure 9] FIG. 10 is a diagram showing an operation pattern 2 according to the first embodiment. [Figure 10] FIG. 10 is a diagram showing an operation pattern 3 according to the first embodiment. [Figure 11] FIG. 10 is a diagram showing an operation pattern 4 according to the first embodiment. [Figure 12] FIG. 12 is a diagram showing a modification of the sequence of FIG. 11. [Figure 13] FIG. 10 is a diagram showing a first modification of the first embodiment. [Figure 14] FIG. 10 is a diagram illustrating an example of a PRACH resource configuration according to a first modification of the first embodiment. [Figure 15] FIG. 10 is a diagram showing a second modification of the first embodiment. [Figure 16] FIG. 13 is a diagram illustrating an example of a MAC PDU according to an eighth modification of the first embodiment. [Figure 17] FIG. 20 is a diagram illustrating an example of the operation of the fourteenth modification of the first embodiment. [Figure 18] FIG. 13 is a diagram illustrating another example of the operation of the fourteenth modification of the first embodiment. [Figure 19] FIG. 20 is a diagram illustrating an example of the operation of the fifteenth modification of the first embodiment. [Figure 20] FIG. 20 is a diagram illustrating an example of the operation of Modification 17 of the first embodiment. [Figure 21] FIG. 20 is a diagram illustrating an example of the operation of Modification 18 of the first embodiment. [Figure 22] FIG. 10 is a diagram showing an example of an operation pattern 1 according to the second embodiment. [Figure 23] FIG. 10 is a diagram showing an example of an operation pattern 2 according to the second embodiment. [Figure 24] FIG. 10 is a diagram showing an example of an operation pattern 3 according to the second embodiment. [Figure 25] FIG. [Figure 26] FIG. [Figure 27] FIG. [Figure 28] FIG. [Figure 29] FIG. [Figure 30] FIG. [Figure 31] FIG. [Figure 32] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First embodiment] (Outline of the first embodiment) Compared with general wireless terminals, wireless terminals for MTC and IoT have a smaller amount of data to transmit and receive, and transmit and receive data less frequently. Therefore, in order for wireless terminals for MTC and IoT to communicate efficiently, early data transmission, which transmits data using a predetermined message during a random access procedure, has been considered. However, current mobile communication systems do not assume that data will be transmitted during a random access procedure, and no mechanism exists that enables early data transmission.

[0013] Therefore, an object of the present disclosure is to provide a communication control method that enables early data transmission.

[0014] A communication control method according to a first embodiment is a method for a mobile communication system. The communication control method includes step A in which a first wireless communication device transmits information regarding whether or not to perform early data transmission, which transmits data using a predetermined message during a random access procedure, to a second wireless communication device, and step B in which, after the second wireless communication device receives the information, the second wireless communication device determines whether or not to perform the early data transmission based on the received information. The first wireless communication device is one of a wireless terminal and a base station, and the second wireless communication device is the other of the wireless terminal and the base station. Step A is performed before the transmission timing of the predetermined message.

[0015] (Mobile communication system) The configuration of a mobile communication system according to the first embodiment will be described. Fig. 1 is a diagram showing the configuration of an LTE (Long Term Evolution) system, which is the mobile communication system according to the first embodiment. The LTE system is a mobile communication system based on the 3GPP standard.

[0016] The LTE system includes a radio terminal (UE: User Equipment) 100, a radio access network (E-UTRAN: Evolved-UMTS Terrestrial Radio Access Network) 10, and a core network (EPC: Evolved Packet Core) 20.

[0017] The UE 100 is a mobile communication device that performs wireless communication with the eNB 200 that manages a cell (serving cell) in which the UE 100 is located.

[0018] E-UTRAN 10 includes base stations (eNBs: evolved Node-Bs) 200. eNBs 200 are connected to each other via an X2 interface. Each eNB 200 manages one or more cells. Each eNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. Each eNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, and the like. "Cell" is used as a term indicating the smallest unit of a wireless communication area. "Cell" is also used as a term indicating a function or resource for performing wireless communication with a UE 100. One cell belongs to one carrier frequency.

[0019] The EPC 20 includes a mobility management entity (MME) and a serving gateway (S-GW) 300. The MME performs various mobility controls for the UE 100. The MME manages information about the tracking area (TA) in which the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. A tracking area is an area consisting of multiple cells. The S-GW controls data forwarding. The MME and S-GW are connected to the eNB 200 via an S1 interface.

[0020] 2 is a diagram showing the configuration of the UE 100 (wireless terminal). The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit .

[0021] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0022] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0023] The control unit 130 performs various controls in the UE 100. The control unit 130 includes at least one processor and a memory. The memory stores programs executed by the processor and information used in the processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor executes the processing described below.

[0024] 3 is a diagram showing the configuration of the eNB 200 (base station). The eNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0025] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0026] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0027] The control unit 230 performs various controls in the eNB 200. The control unit 230 includes at least one processor and a memory. The memory stores programs executed by the processor and information used in the processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor executes the processes described below.

[0028] The backhaul communication unit 240 is connected to neighboring eNBs via an X2 interface. The backhaul communication unit 240 is connected to the MME / S-GW 300 via an S1 interface. The backhaul communication unit 240 is used for communication over the X2 interface and communication over the S1 interface.

[0029] Fig. 4 is a diagram showing the configuration of a protocol stack of a radio interface in an LTE system. As shown in Fig. 4, the radio interface protocol is divided into the first to third layers of the OSI reference model. The first layer is the physical (PHY) layer. The second layer includes a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer. The third layer includes a radio resource control (RRC) layer. The PHY layer, MAC layer, RLC layer, PDCP layer, and RRC layer constitute an access stratum (AS) layer.

[0030] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the eNB 200 via a physical channel.

[0031] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of eNB 200 via a transport channel. The MAC layer of eNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE 100.

[0032] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the eNB 200 via logical channels.

[0033] The PDCP layer performs header compression / decompression and encryption / decryption.

[0034] The RRC layer is defined only in the control plane that handles control information. RRC signaling for various settings is transmitted between the RRC layer of UE 100 and the RRC layer of eNB 200. The RRC layer controls logical channels, transport channels, and physical channels in accordance with the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE 100 and the RRC of eNB 200, UE 100 is in RRC connected mode. When there is no connection (RRC connection) between the RRC of UE 100 and the RRC of eNB 200, UE 100 is in RRC idle mode.

[0035] The NAS layer, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the MME 300C. The UE 100 has functions such as an application layer in addition to the radio interface protocol.

[0036] FIG. 5 is a diagram showing the configuration of a radio frame used in an LTE system. A radio frame is made up of 10 subframes on the time axis. Each subframe is made up of two slots on the time axis. The length of each subframe is 1 ms. The length of each slot is 0.5 ms. Each subframe includes multiple resource blocks (RBs) on the frequency axis. Each subframe includes multiple symbols on the time axis. Each resource block includes multiple subcarriers on the frequency axis. Specifically, one RB is made up of 12 subcarriers and one slot. One symbol and one subcarrier make up one resource element (RE). Of the radio resources (time-frequency resources) allocated to UE 100, frequency resources can be identified by resource blocks, and time resources can be identified by subframes (or slots).

[0037] In the downlink, the first few symbols of each subframe are used as a Physical Downlink Control Channel (PDCCH) for transmitting downlink control information, and the remaining part of each subframe is used as a Physical Downlink Shared Channel (PDSCH) for transmitting downlink data.

[0038] In the uplink, both ends of each subframe in the frequency direction are regions that are mainly used as a Physical Uplink Control Channel (PUCCH) for transmitting uplink control information, and the remaining part of each subframe is a region that is mainly used as a Physical Uplink Shared Channel (PUSCH) for transmitting uplink data.

[0039] (Overview of eMTC and NB-IoT) An overview of eMTC and NB-IoT will be described. In the first embodiment, a scenario is assumed in which a new category of UE 100 exists that targets MTC and IoT services. The new category of UE 100 is a UE 100 whose transmission and reception bandwidth is limited to only a part of the system transmission and reception bandwidth (LTE transmission and reception bandwidth). The new UE categories are called, for example, category M1 and category NB (Narrow Band)-IoT. Category M1 is a category to which eMTC (enhanced Machine Type Communications) UEs belong. Category NB-IoT (category NB1) is a category to which NB-IoT UEs belong. Category M1 is a category to which UE 100 (eMTC Category NB-IoT (Category NB1) limits the transmission and reception bandwidth of UE 100 (NB-IoT UE) to, for example, 1.08 MHz (i.e., a bandwidth of six resource blocks). Category NB-IoT (Category NB1) further limits the transmission and reception bandwidth of UE 100 (NB-IoT UE) to 180 kHz (i.e., a bandwidth of one resource block). Such narrowbanding makes it possible to achieve the low cost and low power consumption required for eMTC UE and NB-IoT UE.

[0040] FIG. 6 is a diagram showing frequency channels handled by eMTC UE and NB-IoT UE. As shown in FIG. 6, the frequency bandwidth of the system frequency band of an LTE system may be 10 MHz. The bandwidth of the system transmission / reception band is, for example, 50 resource blocks = 9 MHz. The bandwidth of the frequency channel that an eMTC UE can support is within 6 resource blocks = 1.08 MHz. A frequency channel of 6 resource blocks or less that an eMTC UE can support is called a "narrow band (NB)." The bandwidth of the frequency channel that an NB-IoT UE can support is 1 resource block = 180 kHz. A frequency channel of 1 resource block that an NB-IoT UE can support is called a "carrier."

[0041] The eMTC UE operates within the LTE transmission and reception bandwidth, while the NB-IoT UE supports operation within the LTE transmission and reception bandwidth, operation in a guard band outside the LTE transmission and reception bandwidth, and operation in a frequency band dedicated to NB-IoT.

[0042] To achieve coverage extension, eMTC UE and NB-IoT UE support an enhanced coverage (EC) function that uses repeat transmission, etc. The enhanced coverage function may include repeat transmission, which repeatedly transmits the same signal using multiple subframes. The more repeat transmissions, the more coverage can be extended. The enhanced coverage function may also include power boosting, which increases the power density of the transmission signal. For example, power density is increased by narrowband transmission, which narrows the frequency bandwidth of the transmission signal. The higher the power density of the transmission signal, the more coverage can be extended. The enhanced coverage function may also include lower MCS transmission, which lowers the MCS used for the transmission signal. Coverage can be extended by transmitting using an MCS with a low data rate and high error resilience.

[0043] (Random Access Procedure Overview) Figure 7 shows a random access procedure for eMTC UE and NB-IoT UE. In the initial state, the UE 100 is in RRC idle mode. The UE 100 executes the random access procedure to transition to RRC connected mode. This case is called initial access from RRC_IDLE. During initial access, a contention-based random access procedure is applied.

[0044] UE 100 selects the cell of eNB 200 as a serving cell. UE 100 may determine that it is in enhanced coverage if a first cell selection criterion (first S-criteria) for normal coverage is not satisfied and a second cell selection criterion (second S-criteria) for enhanced coverage is satisfied. "UE in enhanced coverage" refers to a UE that is required to use an enhanced coverage function (enhanced coverage mode) to access a cell. Note that eMTC UEs are required to use the enhanced coverage mode. Here, the following description will be given assuming that UE 100 is in enhanced coverage.

[0045] In step S1001, the eNB 200 transmits PRACH (Physical Random Access Channel) related information by broadcast signaling (for example, SIB). The PRACH related information includes various parameters provided for each enhanced coverage level. As an example, a total of four enhanced coverage levels, enhanced coverage levels 0 to 3, are defined. The various parameters include an RSRP (Reference Signal Received Power) threshold, a PRACH resource, and a maximum number of preamble transmissions. The PRACH resource includes radio resources (time-frequency resources) and signal sequences (preamble sequences). The UE 100 stores the received PRACH related information.

[0046] In step S1002, the UE 100 measures the RSRP based on the reference signal transmitted from the eNB 200.

[0047] In step S1003, the UE 100 determines its own enhanced coverage level (CE level) by comparing the measured RSRP with an RSRP threshold for each enhanced coverage level. The enhanced coverage level indicates the degree of enhanced coverage required for the UE 100. The enhanced coverage level is related to at least the number of transmissions in repeated transmissions (i.e., the number of repetitions).

[0048] In step S1004, the UE 100 selects a PRACH resource corresponding to its enhanced coverage level.

[0049] Steps S1005 to S1008 constitute a random access procedure. In step S1005, the UE 100 transmits Msg1 (random access preamble) to the eNB 200 using the selected PRACH resource. Note that "Msg" is an abbreviation for message. The eNB 200 identifies the enhanced coverage level of the UE 100 based on the PRACH resource used for the received Msg1.

[0050] In step S1006, eNB 200 transmits Msg2 (random access response) including scheduling information indicating the PUSCH resource allocated to UE 100 to UE 100. UE 100 may transmit Msg1 multiple times up to the maximum preamble transmission number corresponding to its own enhanced coverage level until it successfully receives Msg2.

[0051] In step S1007, based on the scheduling information, the UE 100 transmits Msg3 to the eNB 200. Msg3 may be an RRC connection request message.

[0052] In step S1008, the eNB 200 transmits Msg4 to the UE 100. Msg4 may be an RRC Connection Setup message.

[0053] In step S1009, UE 100 transitions to the RRC connected mode in response to receiving Msg 4. At this time, UE 100 may transmit Msg 5: RRC Connection Setup Complete message to eNB 200. Thereafter, eNB 200 controls repeated transmission to UE 100, etc., based on the identified enhanced coverage level.

[0054] (Operations related to early data transmission) An operation relating to early data transmission according to the first embodiment will be described.

[0055] Early data transmission is a transmission method for transmitting data (user data) using a predetermined message during a random access procedure. The predetermined message is at least one of Msg1 (random access preamble), Msg2 (random access response), Msg3 (e.g., an RRC connection request message), Msg4 (RRC connection establishment message), and Msg5 (RRC connection establishment complete message). Note that "transmitting data using a predetermined message" means at least one of transmitting data included in the predetermined message, transmitting data added to the predetermined message, and transmitting data associated with the predetermined message.

[0056] Early data transmission may be applied to a UE in an RRC suspended state. The RRC suspended state is a special state of the RRC idle mode in which the UE context is retained in the network. In the random access procedure for a UE in an RRC suspended state to recover to an RRC connected mode, Msg 3 is an RRC connection resume request message, Msg 4 is an RRC connection resume message, and Msg 5 is an RRC connection recovery complete message.

[0057] The communication control method according to the first embodiment includes step A in which a first wireless communication device transmits information regarding whether or not to perform early data transmission, which transmits data using a predetermined message during a random access procedure, to a second wireless communication device, and step B in which, after the second wireless communication device receives the information, the second wireless communication device determines whether or not to perform early data transmission based on the received information. The first wireless communication device is one of UE 100 and eNB 200, and the second wireless communication device is the other of UE 100 and eNB 200. Step A is performed before the transmission timing of the predetermined message.

[0058] An overview of operation patterns 1 to 4 according to the first embodiment will be described. Operation patterns 1 to 4 can be combined with at least some of the operations in the "Outline of the Random Access Procedure" (see FIG. 7) described above.

[0059] In operation pattern 1 according to the first embodiment, step A includes a step in which UE 100 selects resources to be applied to transmission of a random access preamble based on whether or not early data transmission is to be performed, and a step in which UE 100 transmits the random access preamble to which the selected resources are applied. In step B, eNB 200 determines whether or not early data transmission is to be performed based on the resources applied to the random access preamble.

[0060] In operation pattern 2 according to the first embodiment, in step A, UE 100 transmits a notification indicating that early data transmission will be performed to eNB 200 while UE 100 is in connected mode. Operation pattern 2 further includes a step of UE 100 transitioning from connected mode to idle mode after transmitting the notification, and a step of eNB 200 or an upper network device retaining the notification while UE 100 is in idle mode. In step B, eNB 200 determines whether to perform early data transmission based on the retained notification during a random access procedure.

[0061] In operation pattern 3 according to the first embodiment, in step A, eNB200 transmits a notification indicating whether or not to perform early data transmission to UE100 by at least one of a paging message, DCI (Downlink Control Information), and PDSCH (Physical Downlink Shared Channel) before the random access procedure is started. In step B, UE100 determines whether or not to perform early data transmission based on the notification from eNB200.

[0062] In operation pattern 4 according to the first embodiment, in step A, eNB200 transmits information indicating the amount of data that is permitted to be transmitted by early data transmission to UE100 before starting the random access procedure. In step B, UE100 determines whether to perform early data transmission based on the amount of data notified by eNB200 and the amount of data that UE100 transmits to eNB200.

[0063] (1) Operation pattern 1 8 is a diagram showing operation pattern 1 according to the first embodiment. Differences from the operation in the above-mentioned "Outline of the Random Access Procedure" will be mainly explained.

[0064] 8, in step S101, the eNB 200 transmits (broadcasts) PRACH resource information indicating PRACH resources (PRACH resource pool) that are available for transmitting a random access preamble, using system information (SIB). The PRACH resources include radio resources (time-frequency resources) and / or signal sequences (preamble sequences).

[0065] The PRACH resources include a first resource group (PRACH resource pool) indicating that early data transmission is to be performed (intent to perform early data transmission) and a second resource group (PRACH resource pool) indicating that early data transmission is not to be performed. The PRACH resources divided into the first resource group and the second resource group may be radio resources (time-frequency resources). The PRACH resources divided into the first resource group and the second resource group may be signal sequences (preamble sequences).

[0066] The eNB 200 includes information indicating the first resource group and information indicating the second resource group in the SIB. The second resource group may be the same PRACH resources as in the past. The first resource group may be PRACH resources reserved separately from the past PRACH resources.

[0067] The first resource group may include a first resource subgroup indicating that uplink data is transmitted by early data transmission and a second resource subgroup indicating that downlink data is received by early data transmission. Furthermore, the first resource group may include a third resource subgroup indicating that both uplink data is transmitted and downlink data is received by early data transmission. The eNB 200 may include information indicating at least one of the multiple resource subgroups (the first resource subgroup, the second resource subgroup, and the third resource subgroup) in the SIB.

[0068] The UE 100 in the RRC idle mode receives an SIB from the eNB 200. The UE 100 in the RRC idle mode determines that it is necessary to establish an RRC connection, and starts preparation for a random access procedure. Here, the UE 100 may determine that it is necessary to establish an RRC connection in order to transmit uplink data in response to uplink data being generated in the UE 100. The UE 100 may determine that it is necessary to establish an RRC connection in order to receive downlink data in response to receiving a paging message addressed to the UE 100 from the eNB 200.

[0069] In step S102, UE 100 in RRC idle mode selects resources to be applied to the transmission of a random access preamble from among the PRACH resources notified in the SIB. If UE 100 performs early data transmission, it selects resources in the first resource group. On the other hand, if UE 100 does not perform early data transmission, it selects resources in the second resource group. Whether or not to perform early data transmission is determined based on at least one of the following criteria 1) to 7): 1) The capability of UE 100, i.e., whether or not UE 100 has the capability to perform early data transmission; 2) The priority (e.g., QoS) of data to be transmitted or received by UE 100; 3) The power state (e.g., remaining battery capacity) of UE 100; and 4) Whether or not data delay reduction is necessary (e.g., the need for early TCP ACK transmission). ) 5) User preference (for example, manual setting). 6) Instruction from the network (for example, based on functional restrictions by the MME or the like or authentication results). 7) Instruction from the eNB (for example, based on whether the eNB has early data transmission / reception capability). Note that "performing early data transmission" may mean that UE 100 wants to perform early data transmission, or may mean whether early data transmission is permitted, or may mean whether early data transmission is possible.

[0070] The UE 100 may determine whether to perform early data transmission separately for uplink and downlink. When transmitting uplink data by early data transmission, the UE 100 may select resources in the first resource subgroup. When receiving downlink data by early data transmission, the UE 100 may select resources in the second resource subgroup.

[0071] In step S103, the UE 100 transmits Msg1 (random access preamble) to which the resource selected in step S102 is applied.

[0072] In step S104, the eNB200 determines whether to perform early data transmission based on the resources applied to the received random access preamble. For example, if the resources in the first resource group are applied to the random access preamble, the eNB200 determines to perform early data transmission for the source UE 100. Furthermore, the eNB200 may determine whether to perform uplink early data transmission or downlink early data transmission based on the resource subgroup. On the other hand, if the resources in the second resource group are applied to the random access preamble, the eNB200 determines not to perform early data transmission for the source UE 100.

[0073] In operation pattern 1, the cases of dividing time-frequency resources and dividing signal sequence resources have been described, but the time-frequency resources and signal sequence resources may be divided in combination. For example, the time-frequency resources may be divided into a first resource group and a second resource group, and the signal sequence resources may be divided into resource subgroups in the first resource group. Alternatively, the signal sequence resources may be divided into a first resource group and a second resource group, and the time-frequency resources in the first resource group may be divided into resource subgroups.

[0074] Furthermore, as will be described later, uplink early data transmission may be used in combination with downlink early data transmission. For example, UE 100 transmits uplink data by uplink early data transmission using Msg3, and receives response data (such as TCP ACK) for the data by downlink early data transmission using Msg4. Therefore, the condition that enables notification of the intention of early data transmission by Msg1 may include the condition that "UE 100 is capable of both uplink early data transmission and downlink early data transmission." In other words, UE 100 that does not have the capability of at least one of uplink early data transmission and downlink early data transmission may be prohibited from notifying the intention of early data transmission by Msg1.

[0075] Furthermore, it is preferable that the new PRACH resource pool (time-frequency resources) used to notify the intention of early data transmission is defined as a resource pool separate from the conventional PRACH resource pool (time-frequency resources). In this case, the eNB 200 may determine whether to configure the new PRACH resource pool and the conventional PRACH resource pool so as not to overlap each other or to configure the new PRACH resource pool and the conventional PRACH resource pool so as to at least partially overlap each other, and may notify the UE 100 of each PRACH resource pool (for example, by an SIB).

[0076] (2) Operation pattern 2 FIG. 9 is a diagram showing operation pattern 2 according to the first embodiment. Differences from the operation in the "Outline of Random Access Procedure" described above will be mainly explained. Also, explanations that overlap with operation pattern 1 will be omitted. Operation pattern 2 may be applied to uplink early data transmission, or may be applied to downlink early data transmission.

[0077] As shown in FIG. 9 , in step S201, UE 100 in RRC connected mode transmits a notification to eNB 200 indicating that early data transmission will be performed. For example, UE 100 notifies eNB 200 that early data transmission will be performed when RRC connection is established next time. UE 100 stores the content of the notification (notification information) sent to eNB 200. A notification indicating that uplink early data transmission will be performed and a notification indicating that downlink early data transmission will be performed may be defined separately. The notification may include capability information of UE 100 (capability related to early data transmission). eNB 200 stores the notification from UE 100. eNB 200 may forward the notification to a higher-level device (e.g., MME 300).

[0078] In step S202, eNB 200 transmits an RRC connection release message to UE 100. The RRC connection release message may include information indicating that UE 100 is set to an RRC suspended state. The RRC connection release message may also include information indicating that UE 100 may (or must) perform early data transmission. The RRC connection release message may also include information indicating that UE 100 must not perform early data transmission.

[0079] In step S203, the UE 100 releases the RRC connection in response to the RRC connection release message, and transitions from the RRC connected mode to the RRC idle mode. The UE 100 may be in an RRC suspended state. The UE 100 holds the notification information while the UE 100 is in the idle mode.

[0080] In step S204, eNB200 retains the notification information while UE100 is in idle mode. In other words, eNB200 retains information indicating that early data transmission will be performed for UE100 when an RRC connection is established next time. In addition to eNB200, or instead of eNB200, an upper device of eNB200 (e.g., MME300) may retain the notification information. The information retained by eNB200 and / or MME300 may include capability information of UE100 (capability related to early data transmission). UE100 and eNB200 may cancel (discard) the notification information when UE100 decides not to perform early data transmission (when conventional PRACH resources are used in Msg1).

[0081] In step S205, the UE 100 transmits Msg1 (random access preamble) to the eNB 200. Although details will be described later, the UE 100 may transmit the random access preamble by applying a dedicated preamble sequence (dedicated preamble) assigned individually to the UE by the eNB 200. The eNB 200 receives the random access preamble from the UE 100.

[0082] The eNB 200 may receive a paging message addressed to the UE 100 in the idle mode from a higher-level device (e.g., the MME 300). The paging message may include a combination of an identifier of the destination UE and notification information held by the higher-level device. The eNB 200 may use the information included in the paging message to determine whether to perform early data transmission for the UE 100.

[0083] If a dedicated preamble sequence is applied, in step S206, eNB200 identifies UE100 based on the preamble sequence. Then, eNB200 determines whether to perform early data transmission based on the notification information stored in step S204. Specifically, if notification information corresponding to the identified UE100 is stored, eNB200 determines to perform early data transmission. On the other hand, if notification information corresponding to the identified UE100 is not stored, eNB200 determines not to perform early data transmission.

[0084] In step S207, the eNB 200 transmits an Msg2 (random access response) to the UE 100.

[0085] In step S208, the UE 100 transmits the Msg3 to the eNB 200.

[0086] If a dedicated preamble sequence is not applied, in step S209, the eNB 200 identifies the UE 100 based on Msg 3. Then, the eNB 200 determines whether to perform early data transmission based on the notification information stored in step S204.

[0087] (3) Operation pattern 3 Fig. 10 is a diagram showing operation pattern 3 according to the first embodiment. Differences from the operation in the "Outline of Random Access Procedure" described above will be mainly explained. Also, explanations that overlap with operation patterns 1 and 2 will be omitted. Operation pattern 3 is applied to downlink early data transmission.

[0088] In operation pattern 3, UE 100 performing the random access procedure is in RRC idle mode or RRC connected mode. UE 100 in RRC idle mode performs a contention-based random access procedure. On the other hand, UE 100 in RRC connected mode can perform a non-contention based random access procedure. In the non-contention based random access procedure, a dedicated preamble sequence is assigned to each UE by eNB 200 using DCI (Downlink Control Information) or dedicated RRC signaling. The non-contention based random access procedure is applied during handover, uplink timing adjustment, etc.

[0089] As shown in FIG. 10, in step S301, before the random access procedure is started, eNB200 transmits a notification indicating whether or not to perform early data transmission to UE100 by at least one of a paging message, DCI, and PDSCH.

[0090] When a paging message is used, a contention-based random access procedure may be applied. The eNB 200 transmits a paging message including a combination of a destination UE identifier and information indicating whether to perform early data transmission. Such a paging message may be generated by the MME 300 and transmitted from the MME 300 to the UE 100 via the eNB 200.

[0091] When DCI or PDSCH is used, UE 100 may be in RRC connected mode. When DCI or PDSCH is used, a non-contention based random access procedure may be applied. eNB 200 includes information indicating whether or not to perform early data transmission in DCI or PDSCH addressed to UE 100. eNB 200 may transmit DCI including information indicating whether or not to perform early data transmission to UE 100 at a paging occasion, which is a timing when UE 100 performing discontinuous reception (DRX) operation monitors a PDCCH.

[0092] When the predetermined message used for early data transmission is Msg1 (random access preamble), the eNB 200 may notify the UE 100 of PRACH resources for early data transmission when notifying the UE 100 of whether to perform early data transmission. The notification is performed by at least one of a paging message, DCI, and PDSCH. The eNB 200 may broadcast some PRACH resources (and a list including their indexes) in advance by an SIB. The eNB 200 may notify the UE 100 of the indexes of the PRACH resources by at least one of a paging message, DCI, and PDSCH.

[0093] In step S302, UE 100 determines whether to perform early data transmission based on the notification from eNB 200 in step S301. If it has been notified that early data transmission will be performed, UE 100 may determine to perform early data transmission. Alternatively, even if it has been notified that early data transmission will be performed, UE 100 may determine not to perform early data transmission. In this case, UE 100 may notify eNB 200 that it will not perform early data transmission, for example, by using Msg1 (random access preamble) or Msg3 (e.g., an RRC connection request message) during the random access procedure.

[0094] When the random access procedure is started, in step S303, the UE 100 transmits Msg1 (random access preamble) to the eNB 200. When performing early data transmission, the eNB 200 transmits downlink data to the UE 100 during the random access procedure, for example, by Msg2 (random access response) or Msg4 (for example, an RRC connection establishment message).

[0095] Alternatively, the eNB 200 may notify the UE 100 of the intention to perform downlink early data transmission during the random access procedure. For example, the eNB 200 may transmit, by Msg2, information indicating that downlink data will be transmitted to the UE 100 by Msg4.

[0096] (4) Operation pattern 4 FIG. 11 is a diagram showing operation pattern 4 according to the first embodiment. Differences from the operation in the above-mentioned "Outline of Random Access Procedure" will be mainly explained. Also, explanations that overlap with operation patterns 1 to 3 will be omitted. Operation pattern 4 is applied to uplink early data transmission.

[0097] As shown in FIG. 11 , in step S401, before starting the random access procedure, eNB200 transmits to UE100 information indicating the amount of data that is permitted to be transmitted by early data transmission (allowable data amount). The information indicating the allowable data amount for early data transmission may be a threshold indicating the allowable data amount. eNB200 may broadcast the information indicating the allowable data amount for early data transmission by SIB. eNB200 may transmit the information indicating the allowable data amount for early data transmission to each UE individually by a unicast message (e.g., an RRC Connection Release message). UE100 receives the information indicating the allowable data amount for early data transmission. UE100 may be in RRC idle mode.

[0098] The allowable data amount notified by the eNB200 to the UE100 may be one or more. In the case of more than one, a list may be configured consisting of multiple combinations of the allowable data amount and its index. The eNB200 may change the contents of the list (the number of records) based on the load status of the cell, etc. The UE100 may indicate to the eNB200 the amount of data to be transmitted by early data transmission by notifying the eNB200 of an index corresponding to the amount of uplink data to be transmitted to the eNB200 by Msg1 based on the list.

[0099] In step S402, the UE 100 determines whether to perform early data transmission based on the allowable data amount notified by the eNB 200 and the amount of data that the UE 100 transmits to the eNB 200. The amount of data that the UE 100 transmits to the eNB 200 may be the amount of uplink data accumulated in an uplink buffer in the UE 100.

[0100] The entity making such a determination may be the access layer (AS) of UE 100 or an upper layer of UE 100. As described above, the access layer (AS) is a layer consisting of a PHY layer, a MAC layer, an RLC layer, a PDCP layer, and an RRC layer. The access layer (AS) is a layer for performing wireless communication with eNB 200. The upper layer is a layer consisting of an NAS layer, an application layer, etc., and is positioned higher than the access layer. Data to be transmitted to eNB 200 (i.e., uplink data) is generated in the upper layer.

[0101] When the decision is made by the access layer (AS) of UE 100, an upper layer of UE 100 may notify the access layer (AS) of UE 100 of the amount of data to be transmitted to eNB 200 by uplink early data transmission. The amount of data to be transmitted to eNB 200 may be the size of a data packet or the total amount of multiple data packets. The data packet may be a PDCP SDU (i.e., an IP packet) or a NAS PDU including a NAS header. For example, the access layer (AS) of UE 100 determines whether to perform early data transmission based on the allowable data amount notified by eNB 200 via an SIB and the size of the data packet notified by the upper layer.

[0102] On the other hand, when the decision is made by the upper layer of the UE 100, the access layer notifies the upper layer of the allowable data amount notified by the eNB 200. The upper layer determines whether to perform early data transmission based on the allowable data amount notified by the access layer and the size of the data packet to be transmitted to the eNB 200.

[0103] UE 100 may determine to perform early data transmission when the amount of data to be transmitted to eNB 200 is equal to or less than the allowable data amount. In this case, UE 100 may terminate the random access procedure without transitioning to the RRC connected mode when the transmission of uplink data by early data transmission during the random access procedure is completed. Such an operation will be described in Modification 4 of the first embodiment.

[0104] The UE 100 may determine to perform early data transmission even when the amount of data to be transmitted to the eNB 200 exceeds the allowable data amount. In this case, the UE 100 may transmit uplink data by early data transmission during the random access procedure, and after transitioning to the RRC connected mode, transmit the remaining uplink data to the eNB 200.

[0105] When the random access procedure is started, in step S403, the UE 100 transmits Msg1 (random access preamble) to the eNB 200. When performing early data transmission, the UE 100 transmits uplink data to the eNB 200 during the random access procedure, for example, by using Msg1 (random access preamble) or Msg3 (for example, an RRC connection request message).

[0106] 11, an example has been described in which, when the amount of data (i.e., uplink data) to be transmitted to eNB200 exceeds the allowable data amount, UE100 transmits the uplink data by early data transmission, transitions to the RRC connected mode, and then transmits the remaining uplink data to eNB200. However, because UE100 must transition to the RRC connected mode even when the amount of uplink data exceeds the allowable data amount by a small amount, this is inefficient and undesirable in terms of power consumption of UE100, etc.

[0107] Therefore, UE 100 may transmit Msg3 multiple times when the amount of data to be transmitted to eNB 200 is greater than the allowable data amount notified by eNB 200 through broadcast information (SIB). Each of the multiple Msg3 transmissions involves data transmission. For example, UE 100 transmits uplink data up to the allowable data amount in the first Msg3 transmission, and transmits the remaining uplink data in the second Msg3 transmission. This allows the transmission of uplink data to be completed by early data transmission, eliminating the need for UE 100 to transition to the RRC connected mode.

[0108] Fig. 12 is a diagram showing a modified example of the sequence of Fig. 11. Here, differences from the sequence of Fig. 11 will be mainly explained.

[0109] 12, in step S411, eNB200 transmits broadcast information (SIB) indicating the amount of data (allowable data amount) that is allowed to be transmitted by early data transmission to UE 100. UE 100 determines whether to perform uplink early data transmission based on the allowable data amount notified by eNB200 and the amount of data (uplink data) that UE 100 transmits to eNB 200. Here, UE 100 determines that although the amount of uplink data is greater than the allowable data amount, it can complete the transmission of uplink data by transmitting Msg3 multiple times, and determines to perform uplink early data transmission.

[0110] When the random access procedure is started, in step S412, UE 100 transmits Msg1 (random access preamble) to eNB 200. UE 100 may notify eNB 200 of its intention to transmit more data than the allowable data amount by using the random access preamble. For example, similar to operation pattern 1, PRACH resources are divided, and resources for indicating an intention to transmit more data than the allowable data amount are defined in the PRACH resources. UE 100 selects resources for indicating an intention to transmit more data than the allowable data amount, and transmits the random access preamble using the selected resources. eNB 200 recognizes the resources used for preamble transmission and determines that UE 100 intends to transmit more data than the allowable data amount.

[0111] In step S413, the eNB200 transmits Msg2 (random access response) to the UE100. The eNB200 may transmit information for transmitting Msg3 multiple times to the UE100 by using Msg2. Such information may be semi-persistent scheduling (SPS) configuration information and / or an activation instruction. For example, the eNB200 transmits to the UE100 configuration information including an SPS period indicating an uplink transmission period. The eNB200 also transmits, by using Msg2, an uplink grant indicating uplink resources (time-frequency resources) allocated to the UE100. The SPS configuration information may be notified to the UE100 by the eNB200 in step S411. Alternatively, the SPS configuration information may be defined in a specification and configured in advance in the UE100.

[0112] In step S414, UE 100 transmits Msg3 with data to eNB 200 using the time-frequency resource indicated in the uplink grant. Here, UE 100 may transmit uplink data to eNB 200 up to the allowable data amount notified by eNB 200. UE 100 includes the uplink data in an RRC message (e.g., RRC Connection Request). Alternatively, UE 100 does not include the uplink data in the RRC message, but multiplexes the uplink data (DTCH) and the RRC message (CCCH) in the MAC layer and transmits the multiplexed data.

[0113] In step S415, UE 100 transmits Msg3 for the second time when a time equivalent to an SPS cycle has elapsed since the timing of step S414. UE 100 transmits Msg3 including data to eNB 200 using the time-frequency resource indicated in the uplink grant. The transmitted Msg3 may include uplink data without including an RRC message.

[0114] The UE 100 transmits Msg3 with data to the eNB 200 multiple times in accordance with the SPS configuration until the transmission of uplink data is completed. The UE 100 may transmit information indicating the completion of the transmission of uplink data (for example, an end marker) in the final transmission of Msg3. The UE 100 may use "BSR=0" to indicate the completion of the transmission of uplink data. Details of "BSR=0" will be described in Modification 8. The eNB 200 recognizes the final transmission of Msg3 by the UE 100.

[0115] In step S416, the eNB 200 transmits Msg4 to the UE 100. The eNB 200 may use Msg4 to terminate SPS transmission. For example, the eNB 200 may transmit a 1-bit indicator indicating the termination of SPS transmission to the UE 100 by Msg4. The UE 100 may terminate the SPS transmission (and discard the SPS configuration) in response to receiving the Msg4. Then, the UE 100 may terminate the random access procedure without transitioning to the RRC connected mode.

[0116] The eNB 200 may explicitly notify the UE 100 by Msg 4 that the random access procedure will be terminated without transitioning to the RRC connected mode. In this case, the transmission of Msg 4 may include the transmission of an RRC Connection Release message or an RRC Connection Reject message.

[0117] Alternatively, the eNB 200 may explicitly notify the UE 100 of the transition to the RRC connected mode by Msg 4. In this case, the transmission of Msg 4 may include the transmission of an RRC Connection Setup message or an RRC Connection Resume message.

[0118] In the sequence of FIG. 12, an example has been described in which the intention to transmit more data than the allowable data amount is notified to the eNB 200 by a random access preamble, and the eNB 200 instructs the UE 100 to transmit an SPS.

[0119] However, in response to receiving the random access preamble, the eNB 200 may transmit an uplink grant that enables transmission of a larger amount of data than the allowable data amount to the UE 100 by using Msg2. The eNB 200 may transmit the uplink grant to the UE 100 when there is a surplus in uplink resources at the time of receiving the random access preamble. When the UE 100 receives from the eNB 200 an uplink grant that enables transmission of a larger amount of data than the allowable data amount, the UE 100 may complete transmission of the uplink data by transmitting Msg3 once.

[0120] Alternatively, when there is no spare uplink resource when receiving the random access preamble, the eNB 200 may not transmit a random access response (Msg2) in response to the random access preamble, or may notify the UE 100 of Reject in Msg4.

[0121] (Summary of the first embodiment) The communication control method according to the first embodiment includes step A in which a first wireless communication device transmits information to a second wireless communication device regarding whether or not to perform early data transmission, which transmits data using a predetermined message during a random access procedure, and step B in which, after the second wireless communication device receives the information, the second wireless communication device determines whether or not to perform early data transmission based on the received information. The first wireless communication device is one of the UE 100 and the eNB 200, and the second wireless communication device is the other of the UE 100 and the eNB 200. Step A is performed before the transmission timing of the predetermined message. According to this communication control method, the second wireless communication device can determine in advance whether or not to perform early data transmission before the transmission timing of the predetermined message (i.e., the timing available for early data transmission) based on the information received from the first wireless communication device. For example, the first wireless communication device and the second wireless communication device can determine in advance whether or not to perform early data transmission. Therefore, early data transmission can be realized.

[0122] (Change example 1) 13 is a diagram illustrating a first modification of the first embodiment. In the first modification of the first embodiment, the UE 100 notifies the eNB 200 of the amount of data (uplink data) to be transmitted by early data transmission using a random access preamble. Differences from the operation in the first embodiment described above will be mainly described.

[0123] 13, in step S501, the eNB 200 broadcasts, by SIB, at least one of information indicating a correspondence relationship between data amounts and PRACH resources (e.g., preamble sequences) and information indicating a minimum guaranteed resource amount for early data transmission. A paging message may be used instead of the SIB.

[0124] In step S502, UE 100 may select resources to be applied to the transmission of the random access preamble based on the amount of data (uplink data) to be transmitted by early data transmission. For example, UE 100 selects a preamble sequence corresponding to the amount of data (uplink data) to be transmitted by early data transmission based on the correspondence relationship notified by eNB 200.

[0125] UE 100 may determine whether to notify eNB 200 of the amount of data (uplink data) to be transmitted by early data transmission, based on the amount of minimum guaranteed resources notified by eNB 200. For example, UE 100 may determine not to notify eNB 200 of the amount of data to be transmitted by early data transmission when the amount of minimum guaranteed resources is sufficient. UE 100 may determine to notify eNB 200 of the amount of data to be transmitted by early data transmission when the amount of minimum guaranteed resources is insufficient.

[0126] In step S503, UE 100 transmits Msg1 (random access preamble) to eNB 200. UE 100 may transmit the random access preamble by applying a PRACH resource (e.g., a preamble sequence) corresponding to the amount of data to be transmitted by early data transmission. Alternatively, UE 100 may add information indicating the amount of data to be transmitted by early data transmission to the random access preamble and transmit the random access preamble.

[0127] In step S504, the eNB 200 determines the amount of uplink radio resources (e.g., PUSCH resources) to be allocated to the UE 100 based on the amount of data notified by the random access preamble. The uplink radio resources may be radio resources used for transmitting Msg3. Information on the uplink radio resources to be allocated to the UE 100 by the eNB 200 is notified to the UE 100 by Msg2.

[0128] In the above description, an example has been described in which the eNB 200 notifies the UE 100 of the amount of minimum guaranteed resources. However, instead of such notification, the eNB 200 may configure the UE 100 as to whether the UE 100 should notify the amount of uplink data by using a random access preamble. This configuration may be performed by using an SIB.

[0129] Alternatively, the notification of the intention to perform uplink early data transmission may have the meaning of implicit notification of the uplink data amount. eNB200 may interpret the notification of the intention to perform uplink early data transmission as meaning that the UL grant size is left to the discretion of the eNB, or that the data amount is equal to the broadcasted UL grant size (which may be the maximum allowable UL grant size), or that the data amount related to the early data transmission requires the broadcasted UL grant size.

[0130] In the operation pattern 1 of the first embodiment, an example has been described in which the UE 100 notifies the eNB 200 of its intention to perform early data transmission using the PRACH resource. Such notification may need to be performed for each CE level. In addition, in this modified example, the amount of uplink data is notified to the eNB 200 using the PRACH resource. When these operations are used together, the number of divisions of the PRACH resource needs to be increased. Furthermore, since one resource pool reserved for the PRACH is finite, increasing the number of divisions of the PRACH resource reduces the size of each divided resource group. As a result, even if the UE 100 randomly selects resources within each resource group, the probability that multiple UEs select the same resource, i.e., the probability of resource collision, increases.

[0131] Therefore, the UE 100 may transmit a random access preamble multiple times before the timing of receiving the random access response. In each of the multiple random access preamble transmissions, the UE 100 selects a resource to be applied to the transmission of the random access preamble based on information to be notified to the eNB 200. This allows multiple PRACH resource pools to be secured in the time direction, thereby increasing the amount of available PRACH resources.

[0132] Fig. 14 is a diagram showing an example of a PRACH resource configuration. In the example shown in Fig. 14, UE 100 transmits preambles twice within a predetermined time period. The predetermined time period may be the time period of one subframe or one radio frame. Two PRACH resource pools #1 and #2 corresponding to the two preamble transmissions are provided. PRACH resource pool #1 and PRACH resource pool #2 may be provided on the same frequency. Each PRACH resource pool is divided in the frequency direction and segmented into a plurality of resource groups. Each PRACH resource pool may also be divided in the time direction.

[0133] In the first preamble transmission, UE 100 selects resources from PRACH resource pool #1. PRACH resource pool #1 is divided into three resource groups, which correspond to CE levels #1 to #3. For example, UE 100 intending to perform uplink early data transmission identifies a resource group corresponding to its own CE level, randomly selects resources from the identified resource group, and transmits a random access preamble using the selected resources. eNB 200 identifies a resource group corresponding to the random access preamble received from UE 100, and determines the CE level of UE 100.

[0134] In the second preamble transmission, UE 100 selects resources from PRACH resource pool #2. PRACH resource pool #2 is divided into four resource groups, and the four resource groups correspond to uplink data amounts #1 to #4. Each of data amounts #1 to #4 is an index indicating a range of the data amount. For example, The UE 100 intends to perform uplink early data transmission, identifies a resource group corresponding to its own uplink data volume, randomly selects resources from the identified resource group, and transmits a random access preamble using the selected resources. The eNB 200 identifies a resource group corresponding to the random access preamble received from the UE 100, and grasps the uplink data volume of the UE 100.

[0135] UE100 may apply the same preamble sequence (signal sequence) to the first preamble transmission and the second preamble transmission. In this case, eNB200 associates the UE that performed the first preamble transmission with the UE that performed the second preamble transmission based on the preamble sequence. Alternatively, for the first preamble transmission and the second preamble transmission, resources may be selected from a resource group according to a predetermined pattern (for example, a frequency hopping pattern). In this case, eNB200 associates the UE that performed the first preamble transmission with the UE that performed the second preamble transmission based on a resource selection pattern.

[0136] When the eNB200 receives the random access preamble transmitted by the second preamble transmission from the UE100, the eNB200 may transmit to the UE100 a random access response corresponding to the random access preamble transmitted by the first preamble transmission. That is, the eNB200 does not transmit a random access response corresponding to the random access preamble transmitted by the second preamble transmission. This makes it possible to ensure backward compatibility. Alternatively, when the eNB200 receives the random access preamble transmitted by the second preamble transmission from the UE100, the eNB200 may transmit to the UE100 a random access response corresponding to the random access preamble transmitted by the second preamble transmission. That is, the eNB200 does not transmit a random access response corresponding to the random access preamble transmitted by the first preamble transmission.

[0137] The eNB 200 may notify the UE 100 of information about each PRACH resource pool by using an SIB. The information about each PRACH resource pool includes at least one of the following: a type of information associated with each PRACH resource pool and each resource group; information indicating the time-frequency range of resources constituting the PRACH resource pool; and information indicating the time-frequency range of each resource group in the PRACH resource pool. The eNB 200 may notify the UE 100 of such information as an individual information element (e.g., RACH-config) for each PRACH resource pool. Each information element may include the corresponding information type (CE level or uplink data volume), or the corresponding information type may be represented by the name of the information element.

[0138] In the example of FIG. 14, an example has been described in which the CE level and the uplink data amount are notified to the eNB200 by preamble transmission, but information other than the CE level and the uplink data amount (for example, the UE category, or a timer value in Modification 14 described later) may be notified to the eNB200 by preamble transmission. Also, the number of consecutive preamble transmissions is not limited to two, and may be three or more. For example, the UE100 may notify the eNB200 of the CE level by transmitting a first random access preamble, notify the eNB200 of its intention to perform early data transmission by transmitting a second random access preamble, and notify the eNB200 of the uplink data amount (i.e., the amount of uplink grant desired by the UE100) by transmitting a third random access preamble. Alternatively, the PRACH resource pool for the first random access preamble transmission may be set to 0. The PRACH resource pool #1 for the first random access preamble transmission may be separated from the PRACH resource pool #2 for the second random access preamble transmission, and the PRACH resource pool #2 may be divided into two resource groups. One resource group of the PRACH resource pool #2 may be reserved for notification of an intention to perform early data transmission, and the other resource group of the PRACH resource pool #2 may be reserved for notification of the uplink data amount. In this case, the eNB 200 may consider the UE 100 that has notified the eNB 200 of the uplink data amount using resources in the resource group for notifying the uplink data amount as a UE that intends to perform early data transmission. Furthermore, the notification of the intention to perform early data transmission may be considered to leave the UL grant size to the discretion of the eNB, or to indicate that the data amount is equal to the broadcasted UL grant size (which may be the maximum allowable UL grant size), or to indicate that the data amount related to the early data transmission requires the broadcasted UL grant size.

[0139] In the example of FIG. 14, an example in which multiple PRACH resource pools are provided in the time direction has been described, but multiple PRACH resource pools may also be provided in the frequency direction.

[0140] Also, an example has been described in which the first preamble transmission and the second preamble transmission are linked by applying the same preamble sequence (signal sequence) to the first preamble transmission and the second preamble transmission. However, the linking is not limited to the case of linking based on the preamble sequence, and the linking may also be based on time-frequency resources. For example, as shown in FIG. 14, assume that PRACH resource pool #1 for the first random access preamble transmission and PRACH resource pool #2 for the second random access preamble transmission each include multiple resource groups, and each resource group is defined as a rectangle. In this case, a specific one of the four vertices of the rectangle is defined as a reference point. UE 100 selects a resource at a predetermined time-frequency position in the resource group for the first random access preamble transmission, using the reference point as a reference. Then, UE 100 selects a resource at the same time-frequency position as in the first random access preamble transmission, using the reference point as a reference, in the resource group for the second random access preamble transmission. In this way, by aligning the relative positions of the time-frequency resources in each of the first and second random access preamble transmissions, eNB200 can link the first preamble transmission with the second preamble transmission.

[0141] Furthermore, in the example of FIG. 14, an example has been described in which the PRACH resource pool is configured with time-frequency resources, but the PRACH resource pool may also be configured with preamble sequence (signal sequence) resources.

[0142] Next, a case where eNB200 fails to receive a preamble at least once among multiple random access preamble transmissions will be described. Here, it is assumed that UE100 notifies eNB200 of its CE level by transmitting a first random access preamble, and notifies eNB200 of its intention to perform early data transmission (particularly, its intention to perform uplink early data transmission) by transmitting a second random access preamble. As shown in Table 1, there are cases 1 to 3 where at least one of the first random access preamble transmission (First PRACH) and the second random access preamble transmission (Second PRACH) fails to be transmitted.

[0143] [Table 1]

[0144] Case 1 is a case where both the first random access preamble transmission and the second random access preamble transmission are successful. In case 1, eNB 200 understands UE 100's intention to transmit early data, allocates uplink resources to UE 100 in an amount greater than a normal uplink grant (i.e., an uplink grant that does not take into account the amount of data transmitted by early data transmission), and notifies UE 100 of the allocation in Msg2. UE 100 transmits data by early data transmission in Msg3.

[0145] Case 2 is a case where the first random access preamble transmission is successful but the second random access preamble transmission fails. In case 2, eNB 200 recognizes that it has received a normal random access preamble and notifies UE 100 of a normal uplink grant by Msg 2. UE 100 determines that no uplink resources available for data transmission have been allocated and transmits Msg 3 containing no data to eNB 200.

[0146] Case 3 is a case where the first random access preamble transmission fails and the second random access preamble transmission is successful. In case 3, the eNB 200 does not receive the first random access preamble, and therefore does not transmit the corresponding Msg2 even when it receives the second random access preamble. Since the UE 100 does not receive the Msg2 from the eNB 200, it starts the random access procedure again from the beginning.

[0147] In case 3, the eNB200 may identify the UE 100 that transmitted the second random access preamble based on the second random access preamble, and may transmit Msg2 to the identified UE 100. For example, the eNB200 may identify the UE 100 based on the preamble sequence and / or hopping pattern applied to the second random access preamble. However, since the eNB200 has not received the first random access preamble, the eNB200 cannot determine the CE level of the UE 100 based on the first random access preamble. In this case, the eNB200 considers that the UE 100 is in normal coverage (i.e., not in extended coverage), and does not perform repeated transmission when transmitting Msg2. Alternatively, the eNB200 may estimate the CE level based on the second random access preamble. Specifically, when repeat transmission is applied to the second preamble transmission, the eNB 200 can count the number of times the preamble transmission is successfully received and estimate the CE level from the count value. The eNB 200 performs repeat transmission when transmitting Msg2 based on the estimated CE level.

[0148] In addition, regardless of whether or not a random access preamble is transmitted multiple times, a UE 100 that has notified eNB 200 of its intention to perform uplink early data transmission by transmitting a preamble may be restricted to transmit a normal Msg3 (Msg3 that does not contain data) to eNB 200 if uplink resources that can be used for data transmission are not allocated.

[0149] Alternatively, the UE 100, which has notified the eNB 200 of its intention to perform uplink early data transmission by transmitting a preamble, may redo the random access procedure if uplink resources usable for data transmission are not allocated. When redoing the random access procedure, the UE 100 transmits a preamble again and notifies the eNB 200 of its intention to perform uplink early data transmission by transmitting the preamble again. The UE 100 may perform such redo of the random access procedure only when permitted by the eNB 200. In other words, the UE 100 is prohibited from redoing the random access procedure when not permitted by the eNB 200. Information indicating such permission may be broadcast from the eNB 200 by an SIB or may be set to the UE 100 by the MME.

[0150] (Change example 2) 15 is a diagram showing a second modification of the first embodiment. Differences in operation from the first embodiment will be mainly described.

[0151] As shown in Fig. 15, in step S601, the UE 100 transmits data together with Msg1 (random access preamble) to the eNB 200 by early data transmission. For example, the UE 100 transmits the data using a new data channel following the random access preamble. However, the amount of data transmitted together with the random access preamble may be small. The UE 100 holds the data transmitted in step S601.

[0152] In step S602, when the eNB 200 receives the data transmitted together with the random access preamble, the eNB 200 returns at least a part of the received data to the UE 100 by using Msg2 (random access response). The eNB 200 may return all of the received data to the UE 100.

[0153] In step S603, UE 100 compares the data transmitted in step S601 with the data returned from eNB 200. If the comparison results in a match, UE 100 determines that the transmission is successful (ACK), and if they do not match, UE 100 determines that the transmission is unsuccessful (NACK). If it determines that the transmission is unsuccessful (NACK), UE 100 retransmits the data whose transmission failed at the next uplink transmission (at the time of PUSCH transmission). Furthermore, UE 100 may notify eNB 200 of the determination result (ACK or NACK) by Msg3. UE 100 may notify eNB 200 of the NACK only when the determination result is NACK.

[0154] (Change example 3) The UE 100 according to the third modification of the first embodiment transmits data to the eNB 200 by early data transmission in the RRC idle mode. After that, the UE 100 in the RRC idle mode receives, from the eNB 200, an ACK or NACK corresponding to the data transmitted by early data transmission by monitoring a PHICH (Physical channel Hybrid ARQ Indicator Channel).

[0155] Generally, UE 100 monitors the PHICH only in the RRC connected mode. However, it is assumed that eNB 200 notifies ACK / NACK for uplink early data transmission through the PHICH. Therefore, even if UE 100 is in the RRC idle mode, it is possible to know whether the early data transmission has been successful by monitoring the PHICH.

[0156] (Change example 4) In a fourth modification of the first embodiment, the UE 100 or the eNB 200 determines whether data transmission is completed by early data transmission. If it is determined that data transmission is completed by early data transmission, the UE 100 ends the random access procedure without transitioning from the RRC idle mode to the RRC connected mode. This enables efficient data transmission.

[0157] For example, in the case of uplink early data transmission, when the UE 100 receives Msg4 (e.g., an RRC Connection Setup message) from the eNB 200, the UE 100 can terminate the random access procedure by transmitting a message indicating failure or rejection (a failure message) to the eNB 200. The message indicating failure or rejection may include information indicating the reason for the failure or rejection (e.g., early data transmission completed).

[0158] In the case of downlink early data transmission, the eNB 200 can notify the UE 100 by Msg4 (for example, an RRC Connection Setup message) that the random access procedure is to be terminated (i.e., there is no need to complete it), and can terminate the random access procedure. Alternatively, the eNB 200 may transmit an RRC Connection Release message as Msg4.

[0159] In the case of downlink early data transmission, eNB200 may notify UE100 that downlink transmission is of a small packet (a small amount of data) by transmitting a special paging message to UE100 before the random access procedure. The special paging message may be generated by MME300 and transmitted from MME300 to UE100 via eNB200. The special paging message may include a combination of an identifier of UE100 and information indicating small packet transmission. When UE100 receives the special paging message, UE100 ends the random access procedure without transitioning to the RRC connected mode after completing data transmission by early data transmission.

[0160] (Change example 5) In the fifth modification of the first embodiment, the eNB 200 transmits a preamble index indicating a preamble sequence to be applied to the random access preamble by using a paging message to the UE 100. For example, the paging message may include a combination of an identifier of the UE 100 and the preamble index.

[0161] Prior to this operation, MME 300 may notify eNB 200 of "application of non-contention based random access procedure" together with the UE identifier (UE ID) in an S1 paging message transmitted to eNB 200 via the S1 interface. MME 300 may also notify eNB 200 of "application of early data transmission" together with the UE ID in the S1 paging message. Alternatively, eNB 200 may notify MME 300 of (multiple) preamble indexes in advance, and MME 300 may notify eNB 200 of an index selected (as needed) from these indexes in an S1 message.

[0162] The UE 100 (for example, a UE in RRC idle mode) receives a paging message from the eNB 200 and transmits a random access preamble to which the preamble sequence indicated by the preamble index is applied to the eNB 200. The eNB 200 can identify the UE 100 that is the source of the random access preamble, based on the preamble sequence applied to the random access preamble.

[0163] This allows a non-contention-based random access procedure to be performed in a situation where a contention-based random access procedure would normally be performed (e.g., during initial connection), thereby eliminating the need for contention resolution, which is required for a contention-based random access procedure.

[0164] (Change example 6) In a sixth modification of the first embodiment, the UE 100 or the eNB 200 transmits data by early data transmission. The data transmitted by early data transmission does not require transmission of an ACK or NACK corresponding to the data, and a repeated transmission is performed in which the data is repeatedly transmitted a predetermined number of times. This improves the reliability of data transmission even when an ACK or NACK is not used.

[0165] UE100 or eNB200 applies repeated transmission to data transmitted by early data transmission even when UE100 is not in enhanced coverage (i.e., when UE100 is in normal coverage). Generally, repeated transmission is not applied when UE100 is in normal coverage. On the other hand, in Modification 6 of the first embodiment, regardless of whether UE100 is in enhanced coverage or not, transmission of ACK or NACK is not applied to data transmitted by early data transmission, and repeated transmission is applied in which the data is repeatedly transmitted a predetermined number of times.

[0166] For example, in the case of uplink early data transmission, even if the eNB 200 receives uplink data through the early data transmission, it does not transmit an ACK / NACK to the UE 100. However, the UE 100 repeatedly transmits the same signal in a lower layer a number of times that is predetermined in the specifications or a number of times that is set by the eNB 200.

[0167] In the case of downlink early data transmission, even if the UE 100 receives downlink data by early data transmission, the UE 100 does not transmit an ACK / NACK to the eNB 200. However, the eNB 200 repeatedly transmits the same signal in a lower layer a number of times that is predetermined in the specifications or a number of times that is notified to the UE 100.

[0168] (Change example 7) In Modifications 7 to 10 of the first embodiment, a scenario is assumed in which the predetermined message used for data transmission in early data transmission is Msg3. That is, the early data transmission in Modifications 7 to 10 of the first embodiment is early data transmission in uplink. As described above, Msg3 is a message transmitted from UE 100 to eNB 200, and is a message used to request UE 100 to transition from idle mode to connected mode. In early data transmission, data (packets) transmitted by Msg3 may be encapsulated in Msg3. For example, UE 100 transmits an RRC connection request message including a data PDU. Alternatively, the data (packets) transmitted by Msg3 may be transmitted as a message different from Msg3, in combination with Msg3 (continuously). For example, UE 100 may transmit one MAC PDU including a message including data (packets) and Msg3. The UE 100 may include the message including the data (packet) and the Msg3 in separate MAC PDUs, and transmit the separate MAC PDUs simultaneously or consecutively.

[0169] In the following explanation of Modifications 7 to 11, an example will be described in which Msg3 is an RRC connection request message, but Msg3 may be an RRC connection reestablishment request message.

[0170] In modification example 7, the above-mentioned step A (i.e., the step of transmitting information regarding whether or not to perform early data transmission) includes a step of instructing the execution of early data transmission in the uplink by means of a MAC RAR (MAC Random Access Response) constituting a random access response (Msg2) transmitted from eNB200 to UE100.

[0171] A typical random access response is configured as a MAC RAR, and includes a timing advance (Timing Advance Command) determined by eNB200 based on the random access preamble, allocation information (UL grant) regarding uplink resources allocated by eNB200 to UE100 for transmitting an RRC connection request message, and a temporary C-RNTI (Temporary C-RNTI) allocated by eNB200 to UE100.

[0172] In Modification 7, upon receiving a random access preamble from UE 100, eNB200 determines whether to cause UE 100 to perform uplink early data transmission (i.e., data transmission using an RRC connection request message) by the method according to the first embodiment or its modification described above. If it is determined that UE 100 should perform early data transmission, eNB200 instructs the execution of uplink early data transmission by means of a MAC RAR constituting a random access response. For example, when a new field is provided in the MAC RAR, eNB200 includes in the new field a flag (permission bit) indicating that data transmission using an RRC connection request message should be performed. If data transmission using an RRC connection request message should not be performed, eNB200 does not include in the new field a flag indicating that data transmission using an RRC connection request message should be performed (or includes the flag as a zero).

[0173] Alternatively, the eNB 200 may notify the UE 100 of whether or not to cause the UE 100 to perform early data transmission by using a MAC CE different from the MAC RAR constituting the random access response. The different MAC CE may be referred to as, for example, an "Early Data Transmission RAR." In this case, the eNB 200 may include an identifier indicating early data transmission in the uplink and / or downlink in the Early Data Transmission RAR.

[0174] As described in Modification 1, UE 100 may notify eNB 200 of the amount of data (uplink data) to be transmitted by early data transmission using a random access preamble. eNB 200 determines the amount of uplink radio resources to be allocated to UE 100 based on the amount of uplink data notified from UE 100, and includes information indicating the determined uplink radio resources in a UL grant in a random access response (MAC RAR).

[0175] (Change example 8) In the above-described modification example 4, when it is determined that data transmission is completed by early data transmission, the UE 100 ends the random access procedure without transitioning from the RRC idle mode to the RRC connected mode. Modification example 8 relates to an example of operation in the case of early data transmission in downlink.

[0176] In the eighth modification, when data transmission is completed by the RRC connection request message, the UE 100 transmits an RRC connection request message including a flag indicating that there is no need to transition to the connected mode (i.e., there is no need to establish an RRC connection) from the UE 100 to the eNB 200. The flag is configured by one bit.

[0177] For example, when the amount of data to be transmitted to eNB200 is equal to or less than the maximum amount of data that can be carried by the RRC connection request message, UE100 determines that data transmission is completed by the RRC connection request message. In this case, when transmitting data by the RRC connection request message, UE100 includes a flag indicating that it is not necessary to transition to connected mode in the RRC connection request message. As a result, the RRC connection request message includes data to be transmitted by early data transmission and a flag indicating that it is not necessary to transition to connected mode. On the other hand, when the amount of data to be transmitted to eNB200 exceeds the maximum amount of data that can be carried by the RRC connection request message, UE100 determines that data transmission is not completed by the RRC connection request message. In this case, when transmitting data by the RRC connection request message, UE100 does not include a flag indicating that it is not necessary to transition to connected mode in the RRC connection request message (or includes the flag as a zero value).

[0178] The eNB 200 receives an RRC connection request message including data and a flag from the UE 100. Here, a reception error (data decoding failure) of data included in the RRC connection request message may occur in the eNB 200 due to a radio state, a collision of RRC connection request messages, or the like.

[0179] If eNB200 has successfully received the data included in the RRC connection request message, the flag included in the RRC connection request message indicates that it is not necessary to establish an RRC connection, and therefore eNB200 does not transmit Msg4 to UE 100, or transmits an RRC connection release message to UE 100. On the other hand, if a reception error occurs in eNB200 for the data included in the RRC connection request message, eNB200 continues the random access procedure to establish an RRC connection, for example, by transmitting Msg4 to UE 100. UE 100 determines whether transmission of data via the RRC connection request message was successful, based on the status of the response from eNB200 to the RRC connection request message.

[0180] Here, a description will be given of the operation of UE 100 when a reception error occurs in data included in the RRC connection request message at eNB 200. When UE 100 determines that transmission of data via the RRC connection request message has failed, it performs one of the following operations 0) to 4).

[0181] 0) The random access procedure is restarted from the transmission of the random access preamble (Msg1). Specifically, the procedure may be restarted from the selection of the preamble sequence. Then, the data may be retransmitted in Msg3.

[0182] 1) Retransmitting the RRC connection request message including the data In this case, the UE 100 includes a flag indicating that it is not necessary to transition to the connected mode in the RRC connection request message.

[0183] 2) Retransmitting the RRC connection request message without the data. In this case, the UE 100 does not include a flag indicating that it is not necessary to transition to the connected mode in the RRC connection request message. The UE 100 transmits (retransmits) the data after transitioning to the connected mode.

[0184] 3) The data is transmitted by Msg5, which is a message transmitted from UE 100 to eNB 200 and is used to notify completion of transition to connected mode. In this case, UE 100 may transition to connected mode. Alternatively, UE 100 may transmit data to eNB 200 instead of transmitting Msg5. eNB 200 may notify UE 100 by Msg6 whether or not data reception from UE 100 has been successful.

[0185] 4) Transition to connected mode.

[0186] In Modification 8, UE 100 may transmit an RRC connection request message including information indicating that it is not necessary to transition to the connected mode, instead of an RRC connection request message including a flag indicating that it is not necessary to transition to the connected mode (i.e., it is not necessary to establish an RRC connection). UE 100 may transmit a MAC CE including information indicating that it is not necessary to transition to the connected mode. For example, the MAC CE is a buffer status report (BSR). The BSR is a MAC CE indicating the amount of data that UE 100 has available for uplink transmission (i.e., the amount of data waiting to be transmitted on the uplink).

[0187] Fig. 16 is a diagram showing an example of a MAC Protocol Data Unit (MAC PDU) generated by the MAC layer. As shown in Fig. 16, the MAC PDU includes a MAC Service Data Unit (MAC SDU) provided to the MAC layer from a layer higher than the MAC layer. RRC messages such as an RRC connection request message and an RRC connection recovery request message are generated by the RRC layer and provided to the MAC layer as MAC SDUs. Uplink data transmitted by early data transmission is provided to the MAC layer as MAC SDUs through the PDCP layer and the RLC layer. The uplink data may be provided to the MAC layer as MAC SDUs without passing through the PDCP layer and the RLC layer.

[0188] In addition to the MAC SDU, the MAC PDU includes a MAC header and a MAC Control Element (MAC CE) generated by the MAC layer. The MAC PDU may further include padding to fill up empty areas in the MAC PDU. While FIG. 16 illustrates an example in which the MAC PDU includes two MAC CEs, the number of MAC CEs may be one or three or more. The MAC CE constituting the BSR includes a buffer size field that stores a value (index) indicating the amount of data available for uplink transmission. The UE 100 includes a value indicating that the amount of data available for uplink transmission is zero in the buffer size field, as information indicating that there is no need to transition to the connected mode. Such a BSR may be referred to as Release Assistance Information (RAI).

[0189] In early data transmission, when data transmission is completed by an RRC connection request message (Msg3), the UE 100 may transmit one or more MAC SDUs including uplink data and the RRC connection request message, and a MAC CE including information indicating that there is no need to transition to the connected mode (BSR=0), all together in one MAC PDU to the eNB 200. Alternatively, the UE 100 may transmit one or more MAC SDUs including the uplink data and the RRC connection request message, and a MAC CE including information indicating that there is no need to transition to the connected mode (BSR=0), consecutively to the eNB 200 in separate MAC PDUs. The eNB 200 determines that there is no need to transition the UE 100 to the connected mode, based on "BSR=0" accompanying the RRC connection request message.

[0190] (Change example 9) Modifications 9 to 12 of the first embodiment assume a scenario in which the predetermined message used for data transmission in early data transmission is Msg4. That is, the early data transmission in Modifications 9 to 11 of the first embodiment is early data transmission in downlink. Note that, as described above, Msg4 is a message transmitted from eNB200 to UE100, and is a message used to transition UE100 from idle mode to connected mode.

[0191] In the following description of Modifications 9 to 12, an example will be described in which Msg4 is an RRC connection establishment message, but Msg4 may be an RRC connection reestablishment message.

[0192] In the ninth modification, the UE 100 in the idle mode initiates a random access procedure. While the UE 100 is in the idle mode, the eNB 200 may not retain the context information of the UE 100 (including information about the capability of the UE 100). In this case, the eNB 200 does not know whether the UE 100 has the capability to handle early data transmission in the downlink, and it is difficult for the eNB 200 to determine whether to perform early data transmission in the downlink.

[0193] Therefore, in Modification 9, UE 100 notifies eNB 200 whether or not it supports downlink early data transmission by using either a random access preamble (Msg1) or an RRC connection request message. For example, UE 100 capable of performing downlink early data transmission transmits information (identifier) ​​indicating that it has the capability of performing downlink early data transmission to eNB 200 by using either the random access preamble (Msg1) or an RRC connection request message. In the case where the random access preamble (Msg1) is used, the method of operation pattern 1 of the first embodiment described above can be used. Based on the notification from UE 100, eNB 200 determines whether UE 100 supports downlink early data transmission. Here, "UE100 supports early data transmission in the downlink" and "UE100 has the capability to perform early data transmission in the downlink" may mean that UE100 has the capability (function) to "receive" data transmitted from eNB200 by early data transmission in the downlink.

[0194] Note that UE 100 may notify eNB 200 of its capability of downlink early data transmission by using a random access preamble only when UE 100 has received from eNB 200 a paging message indicating that downlink early data transmission will be performed (see operation pattern 3 according to the first embodiment described above). The paging message may include information explicitly indicating that downlink early data transmission will be performed. The paging message may also include information implicitly indicating that downlink early data transmission will be performed (for example, information about a PRACH resource used to transmit a random access preamble indicating that UE 100 has the capability of downlink early data transmission).

[0195] Furthermore, UE 100 may notify eNB 200 of its capability for downlink early data transmission by using an RRC connection request message only when UE 100 has received Msg2 (see Modification 7 described above) instructing downlink early data transmission from eNB 200. Msg2 may include information explicitly indicating that downlink early data transmission will be performed. Msg2 may also include information implicitly indicating that downlink early data transmission will be performed.

[0196] (Change example 10) In the ninth modification, an example has been described in which the UE 100 notifies the eNB 200 of whether or not the UE 100 supports downlink early data transmission. However, a mobility management device (MME 300) provided in the core network (EPC 20) may notify the eNB 200 of whether or not the UE 100 has the capability to perform downlink early data transmission. Prior to this operation, the UE 100 may notify the MME 300 of information indicating that the UE 100 has the capability to perform downlink early data transmission, and the MME 300 may hold a UE context including the information for a certain period (for example, while the UE 100 is in an EMM Registered state).

[0197] MME 300 may notify eNB 200 of the capability by a paging message (S1 paging message) or by an INITIAL CONTEXT SETUP message. MME 300 may notify eNB 200 of the capability by NAS signaling or an S1 message when transmitting data to UE 100 by NAS signaling.

[0198] (Change Example 11) In the above-described modification example 4, when it is determined that data transmission is completed by early data transmission, the UE 100 ends the random access procedure without transitioning from the RRC idle mode to the RRC connected mode. Modification example 8 relates to an example of operation in the case of early data transmission in downlink.

[0199] In Modification 11, eNB200 determines, based on the amount of data to be transmitted to UE100 by early data transmission in downlink, either a first message or a second message as a message (predetermined message) to be used for transmitting the data. The first message is an RRC connection establishment message used to transition UE100 from idle mode to connected mode. The second message is a message used to maintain UE100 in idle mode. Although an example in which an RRC connection release message is used as the second message will be described, the second message may be a new message.

[0200] For example, when the amount of data to be transmitted to UE 100 is equal to or less than the maximum amount of data that can be carried by the RRC connection release message, eNB200 determines that data transmission is completed by the RRC connection release message. In this case, eNB200 transmits an RRC connection release message including the data to UE 100 instead of transmitting an RRC connection establishment message. This can stop the random access procedure midway and prevent UE 100 from transitioning to connected mode. On the other hand, when the amount of data to be transmitted to UE 100 exceeds the maximum amount of data that can be carried by the RRC connection release message, eNB200 determines that data transmission is not completed by the RRC connection release message. In this case, eNB200 transmits an RRC connection establishment message including the data to UE 100. This can allow UE 100 to continue the random access procedure.

[0201] Alternatively, instead of using different messages, the eNB 200 may notify the UE 100 of the end of data transmission by an RRC connection establishment message. For example, when the amount of data to be transmitted to the UE 100 is equal to or less than the maximum amount of data that can be carried by the RRC connection establishment message, the eNB 200 determines that the data transmission is completed by the RRC connection establishment message. In this case, the eNB 200 transmits to the UE 100 an RRC connection establishment message including the data and information indicating the end of the data transmission (a so-called end marker). This can interrupt the random access procedure midway and prevent the UE 100 from transitioning to the connected mode. On the other hand, when the amount of data to be transmitted to the UE 100 exceeds the maximum amount of data that can be carried by the RRC connection establishment message, the eNB 200 determines that the data transmission is not completed by the RRC connection establishment message. In this case, the eNB 200 transmits to the UE 100 an RRC connection establishment message including the data but not the end marker. This allows the UE 100 to continue the random access procedure.

[0202] (Change Example 12) In the above-described eighth modification, an example has been described in which, when UE 100 determines that transmission of data by the RRC connection request message (Msg3) has failed, UE 100 retransmits the RRC connection request message including the data.

[0203] Such a retransmission operation is also applicable to early data transmission in downlink. In Modification 9, eNB200 transmits an RRC connection establishment message (Msg4) including data to UE100 by early data transmission, and then determines whether the transmission of the data by the RRC connection establishment message has been successful. eNB200 may make such a determination, for example, based on HARQ ACK or HARQ NACK in the MAC layer. If eNB200 determines that the transmission of data by Msg4 has failed, it retransmits Msg4 including the data. If downlink early data transmission is configured and UE100 fails to receive Msg4, it determines that the data will also be retransmitted in the retransmission of Msg4. Then, UE100 (for example, a layer higher than the MAC layer of UE100 (such as the RRC layer)) waits so as to be able to receive both the RRC message (RRC Connection Reconfiguration) constituting Msg4 and the data.

[0204] (Change Example 13) Modification 13 is an embodiment related to both uplink early data transmission and downlink early data transmission.

[0205] In Modification 13, UE 100 and / or eNB 200 determines not to perform early data transmission in either uplink or downlink for a random access procedure in which early data transmission is performed in either uplink or downlink. This makes it possible for one UE 100 to perform only one of early data transmission in uplink and early data transmission in downlink in one random access procedure.

[0206] If both uplink early data transmission and downlink early data transmission are enabled in one random access procedure, there is a concern that control related to early data transmission may become complicated. Furthermore, the following problem may arise. For example, after transmitting data using an RRC connection request message (Msg3), UE 100 must wait for response data (e.g., TCP ACK) corresponding to the data to be transmitted using an RRC connection establishment message (Msg4). Because such response data is affected by delays in the network, it is not desirable for UE 100 to continue waiting for the response data to be transmitted using the RRC connection establishment message (Msg4). Therefore, by enabling only one of uplink early data transmission and downlink early data transmission in one random access procedure, such a problem can be avoided.

[0207] In Modification 13, when transmitting data using an RRC connection request message (Msg3), UE 100 determines not to receive data using an RRC connection establishment message (Msg4). In other words, UE 100 determines not to perform downlink early data transmission using Msg4 for a random access procedure in which uplink early data transmission using Msg3 is performed. For example, assume that UE 100 is notified by a paging message that downlink early data transmission using Msg4 will be performed (see Operation Pattern 3 of the first embodiment), or is notified by a random access response that downlink early data transmission using Msg4 will be performed (see Modification 7). Even in such a case, UE 100 may determine that it is not necessary to receive data using an RRC connection establishment message (Msg4) when transmitting data using an RRC connection request message (Msg3). Furthermore, when data reception is performed using the RRC connection request message (Msg3), the eNB 200 may determine not to transmit data using the RRC connection establishment message (Msg4).

[0208] In Modification 13, when UE 100 receives data using an RRC connection establishment message (Msg4), UE 100 determines not to transmit data using an RRC connection request message (Msg3). In other words, UE 100 determines not to transmit uplink early data using Msg3 for a random access procedure in which downlink early data transmission using Msg4 is performed. For example, assume that UE 100 is notified by a paging message that downlink early data transmission using Msg4 will be performed (see Operation Pattern 3 of the first embodiment), or is notified by a random access response (Msg2) that downlink early data transmission using Msg4 will be performed (see Modification 7). In such cases, even if UE 100 has uplink transmission data, UE 100 may determine to transmit downlink early data using Msg4 and not to transmit uplink data using Msg3.

[0209] In Modification Example 13, a scenario is assumed in which UE100, which has the capability to perform early data transmission, transmits a notification (identifier) ​​indicating that it has the capability to perform early data transmission to eNB200 via either a random access preamble (Msg1) or an RRC connection request message (Msg3) (see Modification Example 9).

[0210] In such a scenario, if information indicating that downlink early data transmission will be performed is transmitted from eNB200 to UE100 by a paging message or Msg2, when eNB200 receives a notification from UE100 indicating that it has the capability to perform early data transmission, it interprets the notification as indicating the capability to perform downlink early data transmission. UE100 that has the capability and / or intention to perform downlink early data transmission, when it receives information indicating that downlink early data transmission will be performed from eNB200, notifies eNB200 of its capability and / or intention to perform downlink early data transmission by transmitting a notification to eNB200 indicating that it has the capability to perform early data transmission.

[0211] On the other hand, if information indicating that early data transmission will be performed in downlink is not transmitted from eNB200 to UE100 by a paging message or Msg2, when eNB200 receives a notification from UE100 indicating that it has the capability to perform early data transmission, it interprets the notification as indicating the capability and / or intention to perform early data transmission in uplink.If UE100 has the capability and / or intention to perform early data transmission in uplink, when it has not received information indicating that early data transmission will be performed from eNB200, UE100 notifies eNB200 of its capability and / or intention to perform early data transmission in uplink by transmitting a notification to eNB200 indicating that it has the capability to perform early data transmission.

[0212] In this way, the meaning of the notification is changed depending on whether or not information indicating that downlink early data transmission is to be performed is transmitted, allowing one type of notification (for example, one information element) to fulfill two roles.

[0213] (Change Example 14) Unlike Modification 13, Modification 14 assumes a scenario in which both uplink early data transmission and downlink early data transmission can be performed in one random access procedure.

[0214] In a typical random access procedure, when UE 100 transmits Msg3 without data, UE 100 starts a first timer at the time of transmitting Msg3, which timer determines a waiting time for receiving Msg4 transmitted from eNB 200. Such a first timer may be referred to as a Contention Resolution Timer. The first timer is set in UE 100 by an SIB from eNB 200. When the first timer expires without UE 100 receiving Msg4, UE 100 stops processing for receiving Msg4 (e.g., monitoring the PDCCH) and resumes the random access procedure from transmitting Msg1.

[0215] However, as described above, after transmitting data by an RRC connection request message (Msg3), when response data corresponding to the data (e.g., TCP ACK) is transmitted by an RRC connection establishment message (Msg4), the first timer may not have enough waiting time. Therefore, in Modification 14, a second timer for early data transmission is introduced in addition to the first timer. UE 100, in which both the first timer and the second timer are set, selects the first timer when Msg3 transmission does not involve data transmission, and selects the second timer when Msg3 transmission involves data transmission.

[0216] In Modification 14, when UE 100 transmits Msg3 with data by early data transmission, UE 100 starts a second timer that determines a waiting time for reception of Msg4 transmitted from eNB 200 with data. The length of the waiting time corresponding to the second timer is different from the length of the waiting time corresponding to the first timer. For example, the waiting time set in the second timer can be longer than the waiting time set in the first timer. For example, the maximum waiting time that can be set in the second timer is longer than the maximum waiting time that can be set in the first timer. The second timer is set in UE 100 by an SIB from eNB 200. Alternatively, since context information for UE 100 in an RRC suspended state is retained in the network (and UE 100), the second timer may be set in UE 100 by a dedicated RRC message while UE 100 is in connected mode, the setting of the second timer may be retained in the network while UE 100 is in connected mode, and the retained setting may be used during the random access procedure. When the second timer expires without receiving Msg4 with data, UE 100 stops processing for receiving Msg4 (e.g., monitoring the PDCCH) and resumes the random access procedure from transmitting Msg1.

[0217] Alternatively, assuming that early data transmission is applied to eMTC UE and NB-IoT UE, priority may be given to power saving of the UE 100. Therefore, the waiting time set in the second timer may be shorter than the waiting time set in the first timer. This allows the process for receiving Msg4 to be terminated early.

[0218] Each of the first timer and the second timer may be a timer managed in the RRC layer or a timer managed in the MAC layer. The first timer managed in the RRC layer may be referred to as "T300". The first timer managed in the MAC layer may be referred to as "Contention Resolution timer".

[0219] The timer value of the second timer (i.e., the waiting time of Msg4) is not limited to being determined by eNB200 and set in UE100, but may also be determined by UE100. A round trip time, which is the time from when UE100 transmits uplink data until an ACK (e.g., TCP ACK) of an upper layer is returned to UE100, can be estimated in the upper layer of UE100. Therefore, by UE100 determining the timer value of the second timer, a more appropriate timer value can be determined. UE100 may determine the timer value to be set in the second timer and notify eNB200 of the determined timer value. The timer value is notified by Msg3. The timer value may also be notified by Msg1 (preamble transmission).

[0220] Fig. 17 is a diagram illustrating an example of the operation of Modification 14. In Fig. 17, server 50 is provided in a network (e.g., the Internet) higher than the core network (EPC). Also, in Fig. 17, network entities (e.g., S-GW) between eNB 200 and server 50 are omitted from illustration.

[0221] 17, in step S701, the UE 100 determines a timer value to be set in a second timer. The UE 100 may determine the timer value of the second timer based on an estimated value of the round trip time.

[0222] In step S702, the UE 100 transmits Msg3 with data to the eNB 200 by uplink early data transmission. The UE 100 notifies the eNB 200 of the determined timer value by Msg3. The eNB 200 can grasp the Msg4 waiting time in the UE 100 by this notification.

[0223] UE 100 may notify eNB 200 by Msg1 (preamble transmission) that the second timer will be used. Then, UE 100 may use the second timer only when notified by eNB 200 of permission to use the second timer by Msg2, and may notify eNB 200 of the timer value by Msg3.

[0224] The eNB 200 may broadcast (for example, transmit by SIB) timer value candidates (a list including an index for each range of timer values). In this case, the UE 100 may notify the eNB 200 of the index of the timer value in Msg3.

[0225] The eNB200 may broadcast (for example, transmit by SIB) a default timer value of the second timer. In this case, the UE100 basically uses the default timer value. The UE100 may autonomously determine a timer value only when it wants to overwrite the default timer value, and may notify the eNB200 of the determined timer value by Msg3. The value of "T300" may be the default timer value, or the value of the "Contention Resolution timer" may be the default timer value. Furthermore, when the UE100 determines the timer value of the second timer, there may be a restriction that the UE100 must determine a timer value equal to or greater than the default timer value.

[0226] eNB200 may broadcast (for example, transmit by SIB) the maximum timer value that UE100 can set. UE100 determines a timer value that is equal to or less than the maximum value broadcasted by eNB200, and notifies eNB200 of the determined timer value. However, if UE100 determines the maximum value broadcasted by eNB200 as the timer value, it may not need to notify eNB200 of the determined timer value. If a timer value is not notified by UE100, eNB200 may assume that UE100 has determined the maximum value. Note that, if a maximum value is not specified by eNB200 by broadcast, UE100 may use a predefined default maximum value to determine a timer value that is equal to or less than the default maximum value.

[0227] eNB200 may broadcast (for example, transmit by SIB) the minimum value of the timer value that UE100 can set. UE100 determines a timer value that is equal to or greater than the minimum value broadcasted by eNB200, and notifies eNB200 of the determined timer value. However, if UE100 determines the minimum value broadcasted by eNB200 as the timer value, it may not need to notify eNB200 of the determined timer value. If a timer value is not notified by UE100, eNB200 may assume that UE100 has determined the minimum value. Note that, if a minimum value is not specified by eNB200 by broadcast, UE100 may use a predefined default minimum value to determine a timer value that is equal to or greater than the default minimum value.

[0228] In step S703, the UE 100 activates (starts) a second timer to which the determined timer value is set when transmitting Msg3.

[0229] In step S704, the eNB 200 transfers the data received from the UE 100 by Msg3 to the server 50.

[0230] In step S705, the server 50 transmits response data (TCP ACK) to the eNB 200.

[0231] In step S706, the eNB 200 transmits Msg4 including response data (TCP ACK) to the UE 100 by downlink early data transmission.

[0232] The sequence in FIG. 17 assumes a case where Msg3 transmission is successful. However, a case where Msg3 transmission fails, a HARQ NACK (retransmission request) is transmitted from eNB 200 to UE 100, and UE 100 retransmits Msg3 by HARQ is also assumed. After activating the second timer, UE 100 may continue to operate the second timer without restarting (rebooting) it when retransmitting Msg3 by HARQ. This can avoid inconsistency between the TCP ACK waiting time set by the upper layer based on the round trip time and the Msg4 waiting time set by the access layer. Alternatively, after activating the second timer, UE 100 may restart (reboot) the second timer when retransmitting Msg3 by HARQ.

[0233] In the operation of the above-described modification 14, it is assumed that the first timer is "T300" or "Contention Resolution timer" and the second timer is a new timer for early data transmission. That is, it is assumed that the first timer for the random access procedure with early data transmission and the second timer for the random access procedure without early data transmission are specified as separate timers.

[0234] Here, "T300" is a timer that specifies the maximum waiting time from when UE 100 transmits Msg3 in the random access procedure (or RRC Connection Establishment Procedure) until it receives Msg4 (specifically, an RRC message), and is managed in the RRC layer. "Contention Resolution timer" is a timer that specifies the maximum waiting time from when UE 100 transmits Msg3 in the random access procedure until it receives Msg4 (specifically, a MAC CE), and is managed in the MAC layer.

[0235] However, instead of introducing such a new timer (second timer), it is possible to realize an operation similar to that of the above-described modification 14 by specifying two types of timer values ​​as timer values ​​to be set in the first timer ("T300" or "Contention Resolution timer"). This makes it possible to reduce the impact of a change in the system specifications compared to the case where a new timer is introduced. Also, instead of setting two timers (first timer and second timer), it is only necessary to set one timer (first timer), which reduces the processing load on the UE 100.

[0236] In the following modified example 14, an operation when two types of timer values ​​are defined as timer values ​​to be set in the first timer will be described. Here, "T300" is exemplified as the first timer, but the first timer may also be a "Contention Resolution timer."

[0237] In this case, the eNB 200 transmits a first timer value for the random access procedure without early data transmission and a second timer value for the random access procedure with early data transmission to the UE 100. The second timer value is a value greater than the first timer value. Alternatively, the second timer value may be a value smaller than the first timer value.

[0238] The eNB200 broadcasts the first timer value and the second timer value. For example, the eNB200 transmits, via the SIB, "T300" (first timer value), which is an existing information element in the SIB, and "T300-EDT", which is a new information element in the SIB. The eNB200 may include the first timer value and the second timer value in the same SIB, or may include the first timer value and the second timer value in different SIBs.

[0239] In response to determining to perform early data transmission, UE 100 selects the second timer value from the first timer value and the second timer value and sets the selected value in the first timer. Then, when transmitting uplink data by early data transmission, UE 100 starts the timer (first timer) to which the second timer value is set. Transmitting uplink data by early data transmission specifically means that UE 100 transmits uplink user data when transmitting Msg3.

[0240] FIG. 18 is a diagram showing the operation when two types of timer values ​​are defined.

[0241] 18, in step S751, the eNB 200 broadcasts the first timer value and the second timer value. The eNB 200 transmits the first timer value and the second timer value at a predetermined cycle.

[0242] In step S752, the UE 100 in the RRC idle mode detects that uplink data to be transmitted to the network has occurred, and determines that it is necessary to start a random access procedure.

[0243] In step S753, UE 100 determines whether to perform early data transmission (EDT). For example, UE 100 determines to perform EDT when the amount of uplink data to be transmitted is equal to or less than the maximum amount of uplink data (transport block size) broadcast by eNB 200.

[0244] If it is determined that the normal random access procedure is to be performed without performing early data transmission (step S753: NO), in step S754, the UE 100 selects a first timer value and sets the first timer value in a timer (first timer). Then, in step S755, the UE 100 starts the normal random access procedure.

[0245] On the other hand, if it is determined that early data transmission is to be performed (step S753: YES), in step S756, UE 100 selects a second timer value and sets the second timer value in the timer (first timer). Then, in step S757, UE 100 starts a random access procedure involving early data transmission.

[0246] When the random access procedure is started, in step S758, the UE 100 and the eNB 200 transmit and receive Msg1 and Msg2. Note that the UE 100 and the eNB 200 may change the contents of Msg1 and Msg2 depending on whether early data transmission is involved.

[0247] In step S759, the UE 100 transmits Msg3 to the eNB 200. When performing early data transmission, the UE 100 transmits uplink data to the eNB 200 in conjunction with the transmission of Msg3. The UE 100 starts a timer (first timer) when transmitting Msg3.

[0248] In step S760, UE 100 determines whether or not Msg4 has been successfully received from eNB 200. If Msg4 has been successfully received from eNB 200 (step S760: YES), in step S761, UE 100 stops the timer (first timer) and terminates the random access procedure or terminates the random access procedure after transmitting an RRC Connection Complete message. If UE 100 has performed a normal random access procedure, it transitions to RRC connected mode. On the other hand, if early data transmission has been performed, UE 100 maintains RRC idle mode without transitioning to RRC connected mode. Note that UE 100 successfully receiving Msg4 from eNB 200 may mean that UE 100 has decoded Msg4 addressed to UE 100 received from eNB 200 and has acquired the contents of Msg4.

[0249] On the other hand, if the timer (first timer) expires without successfully receiving Msg4 from eNB200 (step S760: NO, step S762: YES), in step S763, UE100 restarts (restarts) the random access procedure from the beginning or terminates the random access procedure.

[0250] 18, UE 100 determines whether to perform early data transmission (step S753) before starting the random access procedure. However, UE 100 may determine to perform (or perform) early data transmission when it transmits EDT (Early Data Transmission) Indication in Msg1 or transmits using a PRACH (Physical Random Access Channel) setting for early data transmission (EDT), and is permitted to perform early data transmission (EDT) in Msg2, receives an EDT Grant including resources related to early data transmission in Msg2, receives DCI for early data transmission (EDT), or receives a UL Grant including uplink resources sufficient to perform early data transmission (EDT), and then performs uplink early data transmission (UL EDT) in Msg3 (transmits user data together with Msg3). In this case, the UE 100 does not set a timer value in the timer (first timer) until it receives Msg2, and sets a timer value in the timer (first timer) after it receives Msg2.

[0251] Note that UE 100 may determine to perform early data transmission in any of the above cases. That is, in the above cases, UE 100 may determine to perform (or is performing) early data transmission when Msg1 is transmitted, when Msg2 is received, or when Msg3 is transmitted.

[0252] (Change Example 15) In the above-described modification 14, an example has been described in which the ACK of the higher layer is transmitted from the eNB 200 to the UE 100 by the Msg4. In this case, after transmitting the Msg3, the UE 100 must continue to monitor the PDCCH for each subframe until it receives the Msg4 (or until the second timer expires). In particular, if the ACK of the higher layer is delayed, there is a concern that the power consumption will increase if the UE 100 continues to monitor the PDCCH.

[0253] In Modification 15, eNB200 transmits Msg4 to UE100 without waiting for the arrival of an ACK from the higher layer, thereby enabling UE100 to discontinue continuous monitoring of the PDCCH. Furthermore, eNB200 notifies UE100 by Msg4 that it plans to transmit data (ACK from the higher layer) to UE100 after transmitting Msg4. This Mg4 transmission may include transmission of information indicating that UE100 is to be maintained in RRC idle mode. This allows UE100 to wait for reception of downlink data while maintaining RRC idle mode. That is, upon receiving Msg4, UE100 waits for downlink data (ACK from the higher layer) without transitioning to RRC connected mode. While waiting for downlink data, UE100 may intermittently monitor the PDCCH in discontinuous subframes by DRX (Discontinues Reception).

[0254] Fig. 19 is a diagram illustrating an example of the operation of Modification 15. In Fig. 19, the server 50 is provided in a network (e.g., the Internet) higher than the core network (EPC). Also, in Fig. 19, network entities (e.g., S-GW) between the eNB 200 and the server 50 are omitted from the illustration.

[0255] As shown in FIG. 19, in step S711, the UE 100 transmits Msg3 with data to the eNB 200 by uplink early data transmission.

[0256] In step S712, the eNB 200 transfers the data received from the UE 100 by Msg3 to the server 50.

[0257] In step S713, eNB200 transmits Msg4 to UE 100. eNB200 transmits, to UE 100, information to the effect that UE 100 is to be maintained in RRC idle mode and advance notice to the effect that downlink data transmission (i.e., downlink early data transmission) is scheduled to be performed after transmission of Msg4, by Msg4. eNB200 determines whether or not to perform downlink early data transmission, for example, by using any of the following methods 1) to 3).

[0258] 1) The eNB 200 learns past traffic patterns and the like, and determines whether to perform downlink early data transmission based on the learning results.

[0259] 2) The MME notifies the eNB 200 of its intention to transmit downlink early data, and the eNB 200 determines whether to transmit downlink early data based on the notification from the MME.

[0260] 3) In Msg3, UE100 notifies eNB200 of the possibility of downlink early data transmission (whether or not there is an upper layer ACK), and eNB200 determines whether or not to perform downlink early data transmission based on the notification from UE100.

[0261] The advance notification transmitted from eNB 200 to UE 100 by Msg4 may include information indicating an expected timing (for example, 10 seconds later) of downlink early data transmission. The advance notification may be included in a MAC CE or an RRC message.

[0262] In step S714, the UE 100 that has received Msg4 may start a timer that specifies a waiting time for receiving downlink data. The timer value (threshold) of the timer may be set by the eNB 200 to the UE 100 via the SIB, Msg4, or Msg2. When the timer expires without receiving downlink data, the UE 100 may end the standby for downlink data.

[0263] In step S715, the UE 100 starts DRX and discontinuously monitors the PDCCH. The DRX setting information may be notified from the eNB 200 to the UE 100 by the SIB or Msg 4. This DRX operation may be an operation based on the DRX in the RRC connected mode or an operation based on the DRX in the RRC idle mode.

[0264] An operation conforming to DRX in RRC connected mode will be described. The DRX cycle set by the eNB 200 to the UE 100 in DRX started in step S715 is preferably longer than the DRX cycle that can be set in DRX in RRC connected mode. Currently, the maximum value of the DRX cycle in RRC connected mode is a time equivalent to 1024 radio frames (i.e., 10.24 seconds). To set a DRX cycle longer than 10.24 seconds, the mechanism of eDRX (extended DRX) can be applied, and either of the following methods a) and b) can be used. In eDRX, a hyperframe is introduced. A hyperframe is a time unit having a time length equivalent to 1024 radio frames. The current hyperframe number (H-SFN) is broadcast by the eNB 200 via the SIB.

[0265] a) UE 100 determines an H-SFN that satisfies "H-SFN mod m = 0" as the reception H-SFN. eNB 200 sets the value of "m" in this calculation formula to UE 100. UE 100 performs a conventional RRC connected mode DRX operation within the determined reception H-SFN. Specifically, UE 100 wakes up at the set DRX cycle and monitors the PDCCH in the wake-up state. UE 100 can maintain a sleep state (i.e., a state in which the PDCCH is not monitored) in an H-SFN that does not satisfy "H-SFN mod m = 0".

[0266] b) UE 100 uses two consecutive hyperframes as one set to support a DRX cycle longer than 1024 radio frames. One hyperframe consists of 1024 radio frames having radio frame numbers (SFNs) ranging from 0 to 1023. UE 100 counts the SFN from 0 to 1023 in the first hyperframe (e.g., an even-numbered hyperframe) constituting one set, then counts the first radio frame of the second hyperframe (e.g., an odd-numbered hyperframe) constituting the set as SFN=1024, and counts the second radio frame of the second hyperframe as SFN=1025. In this way, UE 100 continues counting by continuing the SFN count value in the first hyperframe in the second hyperframe. This allows UE 100 to perform DRX operation using a DRX cycle longer than the time equivalent to 1024 radio frames (i.e., 10.24 seconds).

[0267] Next, a case where an operation conforming to DRX in RRC idle mode will be described. Conventionally, DRX in RRC idle mode is determined using the DRX cycle and the IMSI (International Mobile Subscriber Identity) of the UE 100. The IMSI is used to distribute paging occasions (i.e., timing of PDCCH monitoring) among multiple UEs. However, it is assumed that the eNB 200 has not yet acquired the IMSI of the UE 100 during the random access procedure. Meanwhile, since Msg3 includes an SAE Temporary Mobile Subscriber Identity (S-TMSI) or a Resume ID, the eNB 200 can acquire the S-TMSI or Resume ID of the UE 100 during the random access procedure. Therefore, the eNB 200 and the UE 100 determine the paging occasion using the S-TMSI or Resume ID instead of the IMSI.

[0268] In step S716, the server 50 transmits response data (TCP ACK) to the eNB 200.

[0269] In step S717, the eNB 200 transmits response data (TCP ACK) to the UE 100 by downlink early data transmission. The UE 100 receives the downlink data.

[0270] When UE 100 receives TCP NACK as downlink data, UE 100 may start a random access procedure and perform uplink early data transmission.

[0271] 19, from when UE 100 transmits Msg3 with data (step S711) until it receives a notice of downlink data transmission (step S713), UE 100 operates a "T300" timer managed in the RRC layer and / or a "Contention Resolution timer" managed in the MAC layer, and continuously monitors the PDCCH. Then, UE 100 starts a timer in response to reception of the notice of downlink data transmission (step S713) (step S714), and performs DRX operation while this timer is operating (step S715).

[0272] Even if no advance notice of data transmission is introduced, it is possible to switch the reception operation using such a two-stage timer.

[0273] The operation includes the steps of: UE 100 transmitting an RRC message (Msg3) to eNB 200 during a random access procedure and performing early data transmission to transmit user data; UE 100 starting a first timer in response to the execution of the early data transmission; UE 100 performing a first reception operation in which UE 100 continuously monitors a downlink control channel (PDCCH) while the first timer is operating; UE 100 starting a second timer in response to expiration of the first timer; and UE 100 performing a second reception operation different from the first reception operation while the second timer is operating. The second reception operation is a reception operation that monitors the downlink control channel less frequently than the first reception operation. For example, the second reception operation is a discontinuous reception (DRX) operation that discontinuously monitors the downlink control channel (PDCCH).

[0274] Here, the first timer may be a "T300" timer managed in the RRC layer or a "Contention Resolution timer" managed in the MAC layer. Normally, when the "T300" timer or the "Contention Resolution timer" expires without receiving a response (e.g., Msg4) from the eNB 200, the UE 100 determines that the random access procedure has failed (such as a contention resolution failure) and restarts the random access procedure. However, when early data transmission is performed, the UE 100 continues the random access procedure without determining that the random access procedure has failed, even if the first timer (the "T300" timer or the "Contention Resolution timer") expires.

[0275] Alternatively, the first timer may be a new timer different from the "T300" timer and the "Contention Resolution timer." When performing early data transmission, the UE 100 starts the new timer without starting the "T300" timer and the "Contention Resolution timer" (see Modification 14).

[0276] On the other hand, when a notice of downlink data transmission is introduced, after receiving an RRC message and user data from the UE 100, the eNB 200 transmits a notice of downlink data transmission (a predetermined message) to the UE 100 (step S713). In response to receiving the predetermined message while the first timer is operating, the UE 100 stops the first timer and stops the first reception operation. In response to stopping the first timer (stopping the first reception operation), the UE 100 starts a second timer.

[0277] As the predetermined message, a Contention Resolution of the MAC layer in Msg4 may be used. A flag (one-bit identifier) ​​indicating a notice of data transmission may be added to this Contention Resolution. Then, when transmitting downlink data (step S717), the eNB 200 transmits an RRC Connection Setup of the RRC layer in Msg4 to the UE 100 together with the downlink data.

[0278] (Change Example 16) Modified Example 16 is a modified example related to Modified Examples 14 and 15. Modified Example 16 will be described mainly focusing on the differences from Modified Examples 14 and 15.

[0279] In Modification 16, UE 100 performs uplink early data transmission using Msg3. In response to the execution of the early data transmission, UE 100 starts a timer that determines a waiting time for receiving a response transmitted from eNB 200. The "timer" may be the first timer or the second timer according to Modification 14, or may be the timer according to Modification 15. The "response transmitted from eNB 200" may be Msg4 transmitted from eNB 200 with data or Msg4 transmitted from eNB 200 without data (see Modification 14), or may be data transmitted from eNB 200 after transmitting Msg4 (annual notification) (see Modification 15).

[0280] Then, UE 100 omits monitoring the PDCCH until a PDCCH monitoring timing determined based on the end timing of the waiting time corresponding to the timer. For example, UE 100 monitors the PDCCH only in the subframe at which the timer expires. This allows the receiver of UE 100 to be turned off while the timer is running, thereby reducing power consumption of UE 100.

[0281] Instead of the subframe at which the timer expires, the UE 100 may monitor the PDCCH only in the subframe immediately after the timer expires (i.e., the subframe next to the subframe at which the timer expires), or in the subframe after a specified time has elapsed since the timer expires. Alternatively, instead of the subframe at which the timer expires, the UE 100 may monitor the PDCCH only in the subframe immediately before the timer expires (i.e., the subframe immediately before the subframe at which the timer expires), or in the subframe a specified time before the subframe at which the timer expires.

[0282] Alternatively, UE 100 may monitor the PDCCH only at a plurality of timings (a plurality of subframes) determined based on the time when the timer expires. For example, UE 100 may monitor the PDCCH only in the subframe when the timer expires, and the subframe immediately after the timer expires, or the subframe after a specified time has elapsed since the timer expires. UE 100 may monitor the PDCCH only in the subframe when the timer expires, and the subframe immediately before the timer expires, or the subframe a specified time before the subframe when the timer expires.

[0283] Note that the eNB 200 knows the timer value set in the UE 100 and can estimate the PDCCH monitoring timing in the UE 100. When the eNB 200 transmits a response (for example, Msg4 with data) to the UE 100 at the PDCCH monitoring timing, the UE 100 can receive the response at the PDCCH monitoring timing.

[0284] The UE 100 may perform the operation according to the modified example 16 only when at least one of the following conditions is satisfied. Such a condition may be applied only when a conventional timer (T300, Contention resolution timer) is used.

[0285] Condition 1: Msg1 indicates the intent to transmit early data (EDT Indication). Condition 2: An uplink grant for early data transmission (larger in size than a general uplink grant) is received in Msg2. Condition 3: Early data transmission (data transmission) was performed using Msg3

[0286] (Change Example 17) In the above-described first embodiment, an example has been described in which the eNB 200 sets the maximum amount of data that the UE 100 can transmit in uplink early data transmission to the UE 100. This enables the UE 100 to determine whether or not all of its own uplink data can be transmitted by uplink early data transmission, and to start early data transmission if it is determined that transmission is possible, and not to start early data transmission if it is not determined that transmission is possible.

[0287] As described above, when uplink early data transmission using Msg3 is followed by downlink early data transmission using Msg4, the early data transmission may be applied only when data transmission and reception can be completed using only one set of uplink (Msg3) and downlink (Msg4). Therefore, the UE 100 may also determine whether all of its own downlink data can be received by downlink early data transmission, and may start early data transmission only when it determines that reception is possible.

[0288] In Modification 17, an example will be mainly described in which eNB 200 sets to UE 100 the maximum amount of data that UE 100 can receive in downlink early data transmission. Also, in Modification 17, it is assumed that uplink early data transmission is performed using Msg3 and downlink early data transmission is performed using Msg4.

[0289] In Modification 17, the eNB 200 transmits information on the data amount condition in early data transmission to the UE 100 by a broadcast message (SIB). For example, the eNB 200 transmits, as the information on the data amount condition, the maximum value of the amount of downlink data that the eNB 200 can transmit in early data transmission (maximum transport block size Note that, by the eNB 200 transmitting a broadcast message (SIB) including information regarding the data amount condition, even the UE 100 in the RRC idle mode can receive the broadcast message.

[0290] The UE 100 receives information on the data amount condition from the eNB 200. The UE 100 also estimates the amount of downlink user data to be received from the eNB 200 in early data transmission. For example, the UE 100 estimates the amount of downlink user data to be received from the eNB 200 based on the type of application executed by the UE 100, etc. Specifically, the UE 100 estimates the amount of downlink user data based on the protocol configuration of the application that can use early data transmission. For example, in the case of an application that uses the TCP layer, the UE 100 estimates the amount of TCP ACK data as the amount of downlink user data. In addition, in the case where a response indicating data reception completion is received from the server in the application layer, the UE 100 adds the amount of response data to the amount of downlink user data. Such estimation may be performed in the application layer, and the amount of downlink user data may be notified from the application layer to the NAS layer and / or AS layer. Alternatively, when the estimation is performed in the NAS layer and / or AS layer, it is also possible to estimate the amount of downlink user data from past behaviors included in a history of application layer behaviors stored in the history.

[0291] Then, UE 100 starts early data transmission when the estimated amount of downlink user data satisfies the data amount condition. For example, UE 100 starts early data transmission when the estimated amount of downlink user data is equal to or less than the maximum downlink data amount set by eNB 200. On the other hand, when the estimated amount of downlink user data exceeds the maximum downlink data amount transmitted and set by eNB 200, UE 100 starts a normal random access procedure without starting early data transmission.

[0292] The eNB 200 may transmit, as information regarding the data amount condition, a minimum value of the amount of downlink data that the eNB 200 can transmit in early data transmission (minimum transport block size ) may be transmitted. The UE 100 starts early data transmission when the estimated amount of downlink user data is equal to or greater than the minimum downlink data amount set by the eNB 200. On the other hand, when the estimated amount of downlink user data is less than the minimum downlink data amount set by the eNB 200, the UE 100 starts a normal random access procedure without starting early data transmission. As will be described in detail in a second embodiment, a small amount of data increases padding bits, resulting in poor efficiency. Therefore, the eNB 200 allocates the minimum necessary resources to the UE 100 after transitioning to the RRC connected mode, thereby suppressing an increase in padding bits. Furthermore, transitioning to the RRC connected mode enables, for example, advanced processing such as multiplexing data of multiple UEs into one resource or transport block, and processing such as transmitting data together with other signaling from a single UE.

[0293] Alternatively, if the estimated amount of downlink user data is less than the minimum downlink data amount set by the eNB 200, the UE 100 may maintain the RRC idle mode without initiating the random access procedure.

[0294] FIG. 20 is a diagram showing an example of the operation of the seventeenth modification.

[0295] 20 , in step S771, the eNB 200 broadcasts maximum downlink data amount information indicating the maximum downlink data amount in early data transmission. The UE 100 in the RRC idle mode receives the maximum downlink data amount information from the eNB 200.

[0296] The eNB 200 may further broadcast maximum uplink data amount information indicating the maximum uplink data amount in the early data transmission. The UE 100 in the RRC idle mode receives the maximum uplink data amount information from the eNB 200.

[0297] In step S772, the UE 100 detects a trigger for starting the random access procedure. The trigger for starting the procedure is, for example, occurrence of uplink data to be transmitted in the UE 100, or reception of a paging message by the UE 100, or the like.

[0298] In step S773, the UE 100 estimates the amount of downlink user data to be received in the early data transmission from the eNB 200. Specifically, the UE 100 estimates the amount of downlink user data to be transmitted to the UE 100 from the eNB 200 when transmitting Msg4.

[0299] In step S774, the UE 100 determines whether the estimated downlink user data amount is equal to or less than the maximum downlink data amount set by the eNB 200. If the estimated downlink user data amount is equal to or less than the maximum downlink data amount (step S774: YES), the UE 100 starts a random access procedure involving early data transmission in step S775. On the other hand, if the estimated downlink user data amount exceeds the maximum downlink data amount (step S774: NO), the UE 100 starts a normal random access procedure without early data transmission in step S776.

[0300] In step S774, the UE 100 may further determine whether the amount of uplink user data to be transmitted is equal to or less than the maximum uplink data amount set by the eNB 200. The UE 100 starts the random access procedure involving early data transmission when the estimated downlink user data amount is equal to or less than the maximum downlink data amount and the estimated uplink user data amount is equal to or less than the maximum uplink data amount. Otherwise, the UE 100 starts a normal random access procedure without early data transmission.

[0301] Note that, when it is specified that the maximum uplink data amount and the maximum downlink data amount in early data transmission are the same, eNB 200 does not need to notify UE 100 of the maximum downlink data amount. In this case, UE 100 may determine that early data transmission is possible when the estimated downlink data amount is equal to or less than the maximum uplink data amount set by eNB 200.

[0302] 20, an example has been described in which the eNB 200 broadcasts the maximum downlink data amount information indicating the maximum downlink data amount in early data transmission. However, the eNB 200 may also unicast the maximum downlink data amount information. When transmitting such a unicast message, the eNB 200 can set a data amount condition for each UE individually.

[0303] For example, when the UE 100 is in the RRC connected mode, the eNB 200 transmits an RRC Connection Release message including maximum downlink data volume information to the UE 100. In response to receiving the RRC Connection Release message, the UE 100 transitions to the RRC idle mode and stores the maximum downlink data volume information. Here, the eNB 200 may transition the UE 100 to a suspended state, which is a sub-state of the RRC idle mode. In the suspended state, the context information of the UE 100 is maintained in the eNB 200.

[0304] Then, UE 100 starts a random access procedure in RRC idle mode. When UE 100 is in a suspended state, eNB 200 refers to the context information of UE 100 during the random access procedure and recognizes that a maximum downlink data amount is set for UE 100. On the other hand, when UE 100 is not in a suspended state, eNB 200 does not have the context information of UE 100, and therefore, UE 100 notifies eNB 200 that a maximum downlink data amount is set and / or the set maximum downlink data amount during the random access procedure (for example, when transmitting Msg3).

[0305] (Change Example 18) As described above, when eNB200 sets the maximum data amount (maximum transport block size) for early data transmission to UE100, it is difficult for eNB200 to determine an optimal maximum data amount. Specifically, the amount of data (transport block size) that UE100 transmits and receives through early data transmission varies depending on the type and status of the application executed by UE100. If the maximum data amount for early data transmission is set too large, resources may be wasted. On the other hand, if the maximum data amount for early data transmission is set too small, UE100 that wants to transmit or receive data that exceeds this maximum transport block size cannot use early data transmission, thereby compromising the effects of reducing power consumption and delay achieved by early data transmission.

[0306] In Modification 18, UE 100 determines the amount of user data to be transmitted and received in early data transmission. For example, UE 100 determines the amount of uplink data that UE 100 wishes to transmit through uplink early data transmission. In addition to or instead of such determination, UE 100 may determine the amount of downlink data that UE 100 wishes to receive through downlink early data transmission. Then, when UE 100 is in RRC connected mode, UE 100 transmits, to eNB 200, information indicating a maximum data amount (maximum transport block size) recommended by UE 100 based on the determined amount of user data. The recommended maximum data amount may be the recommended maximum data amount for uplink or may be the recommended maximum data amount for downlink.

[0307] The notification of the maximum data amount may be made only by the UE 100 that has the capability to perform early data transmission. In this case, the eNB 200 may store the notification from the UE 100 in the UE context as UE capability information.

[0308] The eNB200 collects information on the recommended maximum data amount for early data transmission from a large number of UEs 100 and performs statistical processing on the collected information to determine an optimal maximum data amount for early data transmission. For example, the eNB200 collects information on the recommended maximum data amount for uplink early data transmission and determines an optimal maximum data amount for uplink early data transmission based on the collected information. The eNB200 may also collect information on the recommended maximum data amount for downlink early data transmission and determine an optimal maximum data amount for downlink early data transmission based on the collected information. After determining the optimal maximum data amount, the eNB200 sets the determined maximum data amount to the UEs 100. For example, the eNB200 broadcasts information indicating the determined maximum data amount to set the maximum data amount to the UEs 100 within the cell of the eNB200.

[0309] 21 is a diagram showing an example of the operation of Modification 18. Here, an example will be described in which UE 100 notifies eNB 200 of the recommended maximum uplink data amount in early data transmission using Msg3. Note that the following example will be described using the recommended maximum uplink data amount as an example, but it can also be applied if replaced with the recommended maximum downlink data amount.

[0310] As shown in FIG. 21 , in step S781, the eNB 200 transmits, to the UE 100, information requesting or configuring transmission of a notification of the recommended maximum uplink data amount in early data transmission. The eNB 200 may include such information in an Msg4 (RRC Connection Setup message) in the random access procedure, a Measurement Configuration message which is a unicast message, a UE Information Request message, and / or a Minimization of Drive Test (MDT) configuration message. Alternatively, the eNB 200 may notify the UE 100 of information permitting or requesting the notification by a broadcast message. However, step S781 is not essential and can be omitted.

[0311] In step S782, UE 100 determines a recommended maximum uplink data amount for early data transmission. For example, UE 100 stores the amount of uplink data when performing a random access procedure in response to generation of uplink data, and determines the stored amount of uplink data as the recommended maximum uplink data amount.

[0312] In step S783, the UE 100 transmits information indicating the determined recommended maximum uplink data amount to the eNB 200. The UE 100 may include such information in a measurement report, or may include such information in Msg5 (RRC Connection Setup Complete or RRC Connection Resume Complete) of the random access procedure or a UE Information Response message. Note that the RRC Connection Setup Complete and the RRC Connection Resume Complete may be positioned as messages transmitted from the UE 100 to the eNB 200 immediately after the random access procedure.

[0313] Note that, when the amount of uplink data generated in the UE 100 in the RRC idle mode exceeds the maximum uplink data amount set by the eNB 200, the UE 100 may start a normal random access procedure not involving early data transmission and may store the amount of uplink data. Then, after transitioning to the RRC connected mode by the normal random access procedure, the UE 100 may notify the eNB 200 of the amount of uplink data that it has stored as a recommended maximum uplink data amount.

[0314] In step S784, eNB200 determines an optimal maximum uplink data amount based on the recommended maximum uplink data amount notified by UE 100. After determining the optimal maximum uplink data amount, eNB200 broadcasts the determined maximum uplink data amount, thereby setting the maximum uplink data amount to UE 100 within the cell of eNB200.

[0315] Alternatively, eNB200 may set the maximum data amount (maximum uplink data amount) to UE 100 by unicast (for example, RRC Connection Release) instead of setting the maximum data amount to UE 100 by broadcast. In such a case, eNB200 determines the optimum maximum data amount for UE 100 based on the recommended maximum data amount notified from UE 100, and sets the determined maximum data amount to UE 100 by unicast.

[0316] In this modified example, an example has been described in which eNB200 determines the maximum uplink data amount to be set for UE100 based on the recommended maximum uplink data amount notified by UE100. However, as will be described in detail in a second embodiment, multiple blind decoding thresholds may be set for UE100 within the range of the maximum uplink data amount. Specifically, UE100 identifies the smallest blind decoding threshold that is larger than the amount of user data that it transmits, and fills in any shortfall with padding data compared to the identified blind decoding threshold. Therefore, in order to reduce the padding data, eNB200 may determine the blind decoding threshold to be set for UE100 based on the recommended maximum uplink data amount notified by UE100.

[0317] [Second embodiment] The second embodiment will be described mainly focusing on differences from the first embodiment. In the second embodiment, it is assumed that uplink early data transmission is performed using Msg3 during a random access procedure. During the random access procedure, the UE 100 transmits user data to the eNB 200 in addition to transmitting an RRC message (an RRC Connection Request message or an RRC Connection Resume Request message).

[0318] During the random access procedure, the eNB200 transmits to the UE100 Msg2 (random access response) including an uplink grant for allocating uplink radio resources. When the UE100 transmits user data accompanying an RRC message (Msg3) to the eNB200, it is desirable that the allocated data size (i.e., transport block size) corresponding to the uplink radio resources allocated to the UE100 matches the total size of the RRC message and the user data. Note that the transport block size is determined by the amount of uplink radio resources allocated by the uplink grant (e.g., the number of resource blocks) and the MCS. The eNB200 performs decoding processing assuming the transport block size allocated to the UE100.

[0319] However, the transport block size allocated to the UE 100 does not necessarily match the total size of the RRC message and the user data. When the transport block size allocated to the UE 100 is larger than the total size of the RRC message and the user data, the UE 100 needs to transmit padding data in the extra uplink radio resources allocated to the UE 100 so that the eNB 200 can appropriately perform the decoding process. Here, when the extra uplink radio resources allocated are large, the UE 100 needs to transmit a large amount of padding data, which causes a problem of increasing the power consumption of the UE 100 to transmit the padding data. The second embodiment is an embodiment for solving such a problem.

[0320] (1) Operation pattern 1 In operation pattern 1 of the second embodiment, the eNB 200 transmits an uplink grant that allocates periodic uplink radio resources to the UE 100 during a random access procedure. Such resource allocation is sometimes referred to as semi-persistent scheduling (SPS). However, conventional SPS is not applied during the random access procedure.

[0321] In the SPS according to the operation pattern 1 of the second embodiment, the SPS configuration information (for example, an uplink transmission period) is included in the SIB transmitted by the eNB 200 to the UE 100. Also, in the operation pattern 1, the uplink grant transmitted to the UE 100 by the Msg2 includes information on the uplink radio resources (resource blocks) to be allocated to the UE 100 and activates the SPS. That is, the uplink grant allocates periodic uplink radio resources to the UE 100.

[0322] In response to receiving the uplink grant, the UE 100 performs uplink transmission multiple times using periodic uplink radio resources during the random access procedure. Specifically, the UE 100 performs uplink transmission using the uplink radio resources allocated by the uplink grant at an uplink transmission period according to the SPS configuration information.

[0323] In this way, by performing multiple uplink transmissions by the UE 100, it is possible to reduce the amount of uplink radio resources used for one uplink transmission. Also, the UE 100 can transmit an RRC message and user data at different timings (different subframes). For example, in multiple uplink transmissions, the UE 100 transmits at least an RRC message in the first uplink transmission and transmits at least a part of the user data in the second uplink transmission. Therefore, the UE 100 does not need to transmit a lot of padding data.

[0324] In operation pattern 1 of the second embodiment, the eNB 200 transmits, to the UE 100, information for setting the maximum number of uplink transmissions using periodic uplink radio resources. This allows the eNB 200 to properly grasp the number of times that decoding processing of uplink data should be performed. The eNB 200 may transmit the information for setting the maximum number of transmissions by an SIB or by an uplink grant (Msg2). The UE 100 performs uplink transmission multiple times within a range that does not exceed the set maximum number of transmissions.

[0325] 22 is a diagram showing an example of operation pattern 1 of the second embodiment. In an initial state, the UE 100 may be in the RRC idle mode.

[0326] As shown in FIG. 22 , in step S801, the eNB 200 transmits SPS setting information by SIB. The UE 100 receives and stores the SPS setting information. The eNB 200 may transmit information for setting the maximum number of transmissions by SIB. Here, the description will proceed assuming that the maximum number of transmissions is three.

[0327] In step S802, the UE 100 transmits a random access preamble (Msg1) to the eNB 200.

[0328] In step S803, the eNB 200 transmits a random access response (Msg2) including an uplink grant for activating SPS to the UE 100. The uplink grant includes information on uplink radio resources (resource blocks) to be used for one uplink transmission. Here, the resource allocation size for one transmission (transport block size) may match the size of the RRC message. The eNB 200 may transmit information for setting the maximum number of transmissions (three times) using Msg2.

[0329] In step S804 (first uplink transmission), in response to the reception of the uplink grant, the UE 100 transmits an RRC message (Msg3) to the eNB 200 by using the allocated uplink radio resource (resource block).

[0330] In step S805 (second uplink transmission), the UE 100 transmits part of the user data to the eNB 200 by using the allocated uplink radio resource (resource block) in the subframe according to the SPS transmission cycle.

[0331] In step S806 (third uplink transmission), UE 100 transmits remaining user data to eNB 200 using the allocated uplink radio resources (resource blocks) in subframes according to the SPS transmission cycle. Here, since the number of uplink transmissions has reached the maximum number of transmissions, UE 100 deactivates SPS. UE 100 may also discard the SPS setting information.

[0332] If the transmission of user data is completed before the maximum number of transmissions is reached (for example, if all user data is transmitted in step S805), the UE 100 may not perform uplink transmission in the subframe according to the SPS transmission cycle (the timing of step S806). Alternatively, the UE 100 may transmit information indicating the end of data transmission to the eNB 200 at the time of the final uplink transmission (the timing of step S806). Such information (end marker) may be transmitted by the MAC CE.

[0333] In step S807, the eNB 200 transmits Msg4 to the UE 100. The eNB 200 may notify the UE 100, by using Msg4, of which uplink transmissions have been successfully received and / or which uplink transmissions have failed to be received, among multiple uplink transmissions. For example, the eNB 200 may notify the UE 100 that reception was successful only the first time, or that reception was successful from the second time onwards.

[0334] In this operation pattern, an example has been described in which UE 100 transmits user data after transmitting an RRC message (MAC PDU containing an RRC Connection Request), but UE 100 may transmit the user data first and then transmit the RRC message after the data transmission has been completed. In this case, eNB 200 can recognize that the transmission of the user data has been completed by receiving this RRC message.

[0335] (2) Operation pattern 2 In the operation pattern 2 of the second embodiment, the eNB 200 transmits an uplink grant for allocating an uplink radio resource to the UE 100 by using Msg2 during the random access procedure.

[0336] In response to receiving the uplink grant, the UE 100 repeatedly transmits an RRC message (Msg3) using uplink radio resources during the random access procedure. This provides redundancy to the RRC message, thereby increasing the probability that the eNB 200 will successfully receive (decode) the RRC message. The UE 100 may also repeatedly transmit user data, in addition to repeatedly transmitting the RRC message, using the uplink radio resources allocated by the uplink grant. This allows redundancy to be provided to the user data as well.

[0337] In the decoding process, the eNB 200 performs soft combining of the repeatedly transmitted RRC messages and soft combining of the repeatedly transmitted user data. In this way, in the operation pattern 2 of the second embodiment, by performing redundant transmission instead of transmitting padding data, it is possible to effectively utilize the uplink radio resources allocated by the uplink grant.

[0338] HARQ redundancy version In the repeated transmission of the RRC message, the UE 100 may transmit an RRC message having a different HARQ redundancy version (i.e., a redundancy configuration). Also, in the repeated transmission of the user data, the UE 100 may transmit user data having a different HARQ redundancy version. This can further increase the decoding success rate in the eNB 200.

[0339] For example, the UE 100 stores multiple RRC messages (or multiple user data) in different MAC PDUs and transmits a set of multiple MAC PDUs with different HARQ redundancy versions. The MAC PDU includes a MAC header, a MAC CE, and a MAC SDU (see FIG. 16). The RRC messages (or user data) correspond to the MAC SDUs.

[0340] As a first example of redundant transmission, only the MAC SDU may be made redundant, and multiple MAC SDUs may be stored and transmitted in one MAC PDU. In this case, while there is only one redundancy version, a gain due to redundancy can be obtained by the following method. Specifically, when generating a bit string before rate matching, UE 100 generates it from a bit length (TBS size 1) corresponding to the size of the RRC message and user data. Then, when UE 100 retrieves a bit string to be transmitted from a circular buffer during rate matching processing, it retrieves a bit length according to the resources and MCS allocated by eNB 200. As a result, although there is only one redundancy version, a gain due to redundancy can be obtained compared to when the same part of the circular buffer is repeated. When performing brute force decoding (blind decoding), eNB200 defines TBS size 1 (unknown to eNB200) in a predetermined ratio, such as 3 / 4 of TBS size 2, 1 / 2 of TBS size 2, or 1 / 4 of TBS size 2, depending on the bit length corresponding to the resource / MCS allocated by eNB200 (TBS size 2, known to eNB200). This enables blind decoding.

[0341] As a second example of redundant transmission, the MAC header may also be made redundant, and multiple MAC PDUs with different HARQ redundancy versions may be transmitted.

[0342] Transmission power When repeat transmission (redundant transmission) is performed, UE 100 may reduce the transmission power compared to when repeat transmission is not performed, thereby reducing the power consumption of UE 100.

[0343] The UE 100 adjusts the transmission power according to the number of repeated transmissions. The UE 100 may reduce the transmission power as the number of repeated transmissions increases. For example, when the UE 100 redundantly transmits three MAC PDUs, the transmission power may be one-third of that when transmitting one MAC PDU. Note that even if the transmission power is reduced, it is possible to compensate for it by using a soft combining gain in the eNB 200.

[0344] Example of soft blending 1 When performing repeated transmission, the UE 100 may notify the eNB 200 that the repeated transmission will be performed (and / or the number of repeated transmissions), thereby enabling the eNB 200 to perform appropriate soft combining.

[0345] As a specific example of such notification, UE 100 may perform the notification using the pattern of an uplink demodulation reference signal (DMRS) in Msg 3. The DMRS pattern may be a DMRS signal sequence or a DMRS resource allocation pattern (for example, an allocation pattern of resource elements).

[0346] The UE 100 may change the DMRS pattern depending on whether or not repeated transmission is performed. The UE 100 may change the DMRS pattern depending on the number of repeated transmissions.

[0347] Example of soft compositing 2 Instead of transmitting a notification of the repeated transmission, the eNB 200 may attempt the reception process (decoding process) the number of times equal to the number of candidates for the number of repeated transmissions, where the candidates for the number of repeated transmissions include zero (i.e., no repeated transmission is performed).

[0348] In this way, the eNB 200 decodes the repeatedly transmitted RRC message (and the repeatedly transmitted user data) in a round-robin manner by blind decoding, which allows the eNB 200 to perform appropriate soft combining even without notification of the repeated transmission.

[0349] In order for the eNB 200 to decode the repeatedly transmitted RRC message (and the repeatedly transmitted user data) by blind decoding, the following method is applied. Figures 23A and 23B are diagrams showing an example of a repeated transmission method according to operation pattern 2 of the second embodiment.

[0350] When the total size of the RRC message (RRC Connection Request) and user data (Data) is larger than the allocated data size, the UE 100 performs repeated transmission according to a predetermined repeated transmission pattern as shown in Fig. 23A. The eNB 200 performs blind decoding according to the predetermined repeated transmission pattern.

[0351] In the example of FIG. 23A, the allocation data size allocated by the uplink grant (UL grant) is larger than twice the total size of the RRC message (RRC Connection Request) and user data (Data). In this case, half the size of the allocation data size is defined as one unit, and transmission is repeated for each of these units. Furthermore, padding data is allocated to the portion of the allocation data that is less than half the size. The eNB 200 performs blind decoding for each unit, which is half the size of the allocation data.

[0352] Alternatively, when the total size of the RRC message (RRC Connection Request) and user data (Data) is larger than the allocated data size, the UE 100 may repeatedly transmit only the RRC message. Since the data size of the RRC message is known, the eNB 200 performs blind decoding on the assumption that only the RRC message is repeatedly transmitted.

[0353] On the other hand, when the total size of the RRC message (RRC Connection Request) and user data (Data) is smaller than the allocated data size, the UE 100 performs repeated transmission according to a predetermined repeated transmission pattern, as shown in Fig. 23B. For example, when the allocated data size is twice or more the data size of the RRC message, the UE 100 performs repeated transmission of the RRC message. The UE 100 arranges padding data in the remaining part. The eNB 200 performs blind decoding, assuming that only the RRC message is repeatedly transmitted.

[0354] When the total size of the RRC message (RRC Connection Request) and user data (Data) is smaller than the allocated data size, eNB200 may attempt decoding for each of three patterns: a case where only the RRC message is repeatedly transmitted, a case where only the RRC message is transmitted, and a case where user data is transmitted together with the RRC message.

[0355] The UE 100 may notify the eNB 200 of information indicating which repetitive transmission pattern to apply, by using a MAC header or MAC CE attached to the RRC message.

[0356] (3) Operation pattern 3 In operation pattern 3 of the second embodiment, the eNB 200 broadcasts, for example, by an SIB, information indicating multiple resource pools available for transmitting user data in early data transmission. The multiple resource pools have different amounts of available radio resources (i.e., available transport block sizes).

[0357] When performing early data transmission in response to receiving an uplink grant from the eNB 200, the UE 100 transmits user data using a resource pool selected from multiple resource pools. This allows the UE 100 to select a resource pool appropriate for the amount (size) of user data that the UE 100 wishes to transmit, thereby eliminating or reducing padding data to be transmitted. Note that the eNB 200 attempts to receive (decode) the user data in each resource pool and receives (decodes) the user data in one of the resource pools.

[0358] The UE 100 may transmit the user data and the RRC message together using the selected resource pool, or may transmit the RRC message using the uplink radio resource allocated by the uplink grant, and then transmit the user data using the selected resource pool.

[0359] The UE 100 may select a resource pool to be used for transmitting user data from among a plurality of resource pools based on the amount of user data. For example, the UE 100 compares the amount (data size) of user data to be transmitted to the eNB 200 with the transport block size corresponding to each resource pool, and selects an optimal resource pool.

[0360] The UE 100 may select a resource pool taking into consideration the priority of user data. For example, when uplink radio resources (resource blocks) to be used for transmission can be selected from the selected resource pool, the larger the resource pool, the lower the possibility of interference caused by resource collision between the UEs 100. Therefore, the UE 100 may select a larger resource pool when the priority is high. Alternatively, the eNB 200 may notify available priority information for each resource pool. Note that in the UE 100, the priority may be identified in a higher layer (e.g., an application layer) and notified from the higher layer to an AS (e.g., an RRC layer or a MAC layer). The priority may be set in advance in the UE 100 by an application server, or may be authenticated by an MME or the like and set in the UE 100. Furthermore, the resource pool may be provided for each CE level.

[0361] Fig. 24 is a diagram showing an example of operation pattern 3 of the second embodiment. In Fig. 24, one section in the time direction corresponds to one subframe, and the time direction corresponds to an uplink frequency band.

[0362] First, UE 100 grasps a resource pool for user data and a resource pool for a random access preamble (Msg1) by receiving the SIB. Then, as shown in FIG. 24, UE 100 selects one resource pool from a plurality of resource pools for random access preambles in subframe SFa and transmits the random access preamble using the selected resource pool. In the example of FIG. 24, resource pool #1 for random access preambles is associated with resource pool #1 for user data (for example, a size of 1000 bits), and resource pool #2 for random access preambles is associated with resource pool #2 for user data (for example, a size of 100 bits). However, there may be only one resource pool for random access preambles, and the resource pool for random access preambles and the resource pool for user data may not be associated with each other.

[0363] Next, eNB200 receives the random access preamble in one of the resource pools, and if use of this resource pool is permitted, transmits a random access response (Msg2) to UE100. Msg2 includes a temporary identifier (Temporary C-RNTI) assigned by eNB200 to UE100. When UE100 receives Msg2, UE100 considers that early data transmission is permitted. Then, in subframe SFb, UE100 transmits an RRC message (Msg3) to eNB200 using the uplink radio resource assigned by the uplink grant in the random access response. UE100 transmits the RRC message including the temporary identifier (Temporary C-RNTI).

[0364] Next, in the subframe SFc, the UE 100 transmits user data by using the selected resource pool to the eNB 200. The UE 100 transmits the user data by including a temporary identifier (Temporary C-RNTI) in the user data.

[0365] (4) Operation pattern 4 In operation pattern 4 of the second embodiment, the eNB 200 transmits an uplink grant that allocates uplink radio resources to the UE 100 during a random access procedure. When the allocated data size corresponding to the uplink grant is larger than the total size of the RRC message and user data, the UE 100 determines whether to perform early data transmission using the uplink radio resources or to transmit only the RRC message using the uplink radio resources. The UE 100 makes such a determination based on the amount of padding data required for early data transmission. The eNB 200 attempts reception processing (decoding processing) for both the case where the UE 100 transmits only the RRC message and the case where the UE 100 performs early data transmission.

[0366] When transmitting only the RRC message, the eNB 200 can grasp the data size of the RRC message, and therefore, the UE 100 does not need to transmit padding data. On the other hand, when performing early data transmission, that is, when transmitting user data together with the RRC message, the eNB 200 does not grasp the amount of user data. Therefore, the UE 100 may need to transmit padding data in order to transmit at the allocated data size.

[0367] For example, the UE 100 determines the amount of padding data required for early data transmission based on the allocated data size. If the determined amount of padding data is greater than a threshold, the UE 100 determines that the power consumption due to the transmission of the padding data is large, and transmits only an RRC message without performing early data transmission. This makes it possible to avoid an increase in the power consumption of the UE 100 due to the transmission of the padding data.

[0368] [Other embodiments] The second embodiment may be implemented in combination with the first embodiment and its modifications, or two or more modifications of the first embodiment 1 to 15 may be implemented in combination. Furthermore, modifications 1 to 15 of the first embodiment may be implemented independently of the operations according to the modifications, without relying on the operations according to the first embodiment.

[0369] In the above-described embodiment and its modifications, no particular distinction is made between a CP (Control Plane) solution and a UP (User Plane) solution, but the operations according to the embodiment and its modifications can be applied to both the CP solution and the UP solution. In the CP solution, in early data transmission, data is included in an RRC message. In the UP solution, in early data transmission, data is not included in an RRC message, but data (DTCH) and an RRC message (CCCH) are multiplexed and transmitted in the MAC layer.

[0370] In the UP solution, the RRC message corresponding to Msg3 is an RRC Connection Resume Request message, and the RRC message corresponding to Msg4 is an RRC Connection Resume message. Normally, when UE 100 receives RRC Connection Resume, it establishes (re-establishes) a PDCP entity. However, when performing early data transmission, it is considered that UE 100 has already established (re-established) a PDCP entity for data transmission before receiving RRC Connection Resume. Therefore, after UE 100 establishes (re-establishes) a PDCP entity for performing early data transmission, UE 100 may receive an instruction (RRC Connection Resume) to transition from idle mode to connected mode from eNB 200. In this case, UE 100 may skip the establishment (re-establishment) of the PDCP entity and maintain the already established PDCP entity.

[0371] In the above-described embodiment, an example has been described in which radio terminals (eMTC UE and NB-IoT UE) for MTC and IoT are used. However, the present disclosure is not limited to eMTC UE and NB-IoT UE. The operation according to the above-described embodiment may be applied to a general UE.

[0372] In the embodiments, the RRC idle, suspended, and connected modes have been mainly described as examples, but the present invention is not limited to these. The present invention may also be applied to the RRC light connection and inactive modes. The RRC light connection is one state of the RRC connected mode, and is a special state in which some of the RRC idle mode procedures are applied. The inactive mode is expected to be introduced in the fifth generation mobile communication system, and is an RRC state different from the RRC connected mode and the RRC idle mode. The "RRC idle mode" in the above-described embodiments may be read as the "inactive mode."

[0373] Although the embodiment has been described using an example of a UE located in an enhanced coverage area, the present invention is not limited to this. The operation according to the above-described embodiment may be applied to a UE located in a normal coverage area. Specifically, in the RACH procedure, it is not necessary to determine the CE level based on RSRP measurement.

[0374] In the above-described embodiment, the LTE system is exemplified as a mobile communication system. However, the present disclosure is not limited to the LTE system. The operations according to the above-described embodiment may be applied to mobile communication systems other than the LTE system (for example, a fifth-generation mobile communication system).

[0375] A program that causes a computer to execute each process performed by the UE 100 and the eNB 200 may be provided. The program may also be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. A chipset may also be provided, which is configured by a memory that stores a program for executing each process performed by the UE 100 and the eNB 200 and a processor that executes the program stored in the memory.

[0376] [Appendix 1] (1. Introduction) A new work item for further enhanced MTC for LTE (eFeMTC) was approved in RAN#75, and WID has identified several goals for RAN2 to consider as the lead WG. The objective is to specify the following improvements for machine type communication for BL / CE UE: [...] Improved latency: [...] Supports early data transmission [RAN2 led, RAN1, RAN3] · Evaluation of power consumption / latency gains on dedicated resources during the random access procedure (after PRACH transmission and before RRC connection setup is complete) and specification of the required support for DL / UL data transmission, at least in the case of RRC suspend / resume.

[0377] This appendix discusses these improvement considerations.

[0378] (2. Consideration) (2.1. Improved Latency - Early Data Transmission) The WID clearly states that "Evaluate the power consumption / latency gain on dedicated resources during the random access procedure (after PRACH transmission and before RRC connection setup is completed), at least in the RRC suspend / resume case, and specify the required support for DL / UL data transmission." The latency performance improvement provided by early data transmission may lead to additional power consumption, taking into account various MTC device implementations. If additional power consumption is required for some MTC implementations, the UE should be allowed to select legacy RACH procedures, i.e., non-early data transmission modes, to avoid burdening legacy use cases.

[0379] Proposal 1: The solution for early data transmission should minimize additional power consumption. For example, the UE should be allowed to select the legacy RACH procedure, i.e., the "non-early data transmission mode."

[0380] The WID also states that early data transmission should be performed after Msg1 and before Msg5, i.e., candidates for extension are Msg2, Msg3, and Msg4. On the other hand, it is expected that some control signaling can be sent before Msg2 or even after Msg4.

[0381] Proposal 2: It is not necessary that control signaling related to early data transmission be required to be sent in message 2, message 3, and message 4.

[0382] The WID does not identify whether data for early transmission is assumed to be small packets, large data, and / or both. For example, if only small data is assumed, it may be better for the UE to transition to RRC IDLE as soon as data transmission is completed, even within the RACH procedure. The solution may differ depending on the data size for early transmission. Therefore, RAN2 should first consider and determine the assumed data size.

[0383] Proposal 3: RAN2 should consider the assumed data size (i.e., small packets, large packets, or both) for early transmission.

[0384] The WID does not explicitly state whether early data transmission can be initiated only in the contention-based RACH procedure, the contention-free RACH procedure, or both. The solution assumptions differ between the two procedures, for example, whether a PDCCH command can be assumed. Therefore, RAN2 should clarify which RACH procedure is assumed for early data transmission.

[0385] Proposal 4: RAN2 should consider whether early data transmission is applicable to contention-based RACH procedures, contention-free RACH procedures, or both.

[0386] Figure 25 shows the general RACH procedure (contention-based / free).

[0387] (2.2. Improving Power Consumption - Relaxed Monitoring for Cell Reselection) WID states that "(Re)configuration enables relaxed UE monitoring for cell (re)selection." Regardless of the need for (re)configuration, stationary UEs should be allowed to perform relaxed monitoring because cell reselection is rare. If (re)configuration is required as intended in WID, some UE assistant information, such as the number of cell reselection reports and stationary UE indication, may be required because the network cannot know whether an IDLE mode UE will perform cell reselection.

[0388] Proposal 5: It should be configurable whether a stationary UE is allowed to operate under relaxed monitoring for cell reselection.

[0389] [Appendix 2] (1. Introduction) RAN2#99 has started to study more advanced MTC for LTE (eFeMTC) and agreement on early data transmission capabilities has been reached as follows:

[0390] Agreement Supports early UL data transmission in Msg3 for control plane and user plane CIoTEPS optimization.

[0391] Supports early DL data transmission in Msg4 for control plane and user plane CIoTEPS optimization.

[0392] Agreement The early data transmission feature is considered when AS security is not established to only transmit data using the CP.

[0393] The early data transfer function is considered when AS security is established to transmit data using CP and / or UP.

[0394] This appendix provides details of the extensions required for early data transmission.

[0395] (2. Consideration) In the following sections, for simplicity, we will describe early UL data transmission and early DL data transmission separately, and take the existing random access procedure as the baseline.

[0396] (2.1. Early UL Data Transmission) (2.1.1. Clarification of Email Discussion) If the UE intends to perform an early UL data transmission in Msg 3, the SIB provides the specific preamble to be used in Msg 1. In other words, if the SIB does not include such an indication with a specific preamble, the early UL data transmission is not allowed.

[0397] Msg1 contains the UE's intention with a specific preamble whether or not early UL data transmission is in this random access procedure.

[0398] Msg2 indicates whether the UE's intention is acceptable in addition to the existing random access response.

[0399] Msg3 contains data and an enhanced RRC connection (resume) request to inform the eNB whether data transmission within this random access procedure is completed, i.e. whether the UE needs to transition to RRC Connected.

[0400] Msg4 can be either an RRC Connection Setup / Resume or an RRC Connection Release, i.e. the network responds with Msg4 and confirms that receipt of Msg3 completes contention resolution and includes a NAS PDU if necessary.

[0401] From the eNB's perspective, it is necessary for the SIB to indicate whether early UL data transmission is permitted, i.e., a minimum of SIB indications such as Up-CIoT-EPS-Optimized are required. The UE can then include a specific preamble in Message 1 to indicate its intention to use early UL data transmission to the eNB. However, even if the UE includes a specific preamble in Msg1, the eNB should still have the option to decide whether to accept the early UL data transmission, as there may be other reasons why the eNB needs to reject the early UL data transmission. This may be conveyed to the UE via Msg2. Therefore, two stages of authorization are required before early UL data transmission is authorized.

[0402] Proposal 1: It should be agreed that RAN2 will send a specific preamble provided in the SIB to Msg1 to inform the eNB that it will perform an early data transmission in Msg3, and the eNB will indicate in Msg2 whether early data transmission is acceptable or not.

[0403] Since one of the main purposes of early data transmission is to reduce the UE's power consumption, the UE should be released to IDLE as soon as the data transmission is completed. The Release Assistance Indication (RAI) can be reused for this purpose. On the other hand, if the data packet to be transmitted is small and can be transmitted completely within the limited size of Msg3, it is assumed that the UE does not need to transition to an RRC connection. If the UE is allowed to request such a connectionless data transmission, the request should be conveyed to the eNB using one of the following options:

[0404] Option 1a: Set spare1 to the Establishment Cause of the RRC Connection Request and / or Resume Cause of the RRC Connection Resume Request.

[0405] Option 1b: There is a spare IE in the RRC connection request and / or the RRC connection reestablishment request.

[0406] Option 1c: Specify RAI (i.e., BSR=0) in Msg3.

[0407] Option 1d: A new RRC message, e.g., RRC Connection-less Request.

[0408] Options 1a-1c have less impact on the specification than Option 1d. From the perspective of signaling overhead, Options 1a and 1b are the same as Option 1c, but are superior to Option 1. From a technical standpoint, Option 1b is more flexible than Option 1a, especially considering potential needs in future releases, since early UL data transmission is generally not related to establishment / resumption causes. Therefore, Option 1b is preferred.

[0409] Proposal 2: RAN2 should agree to include a 1-bit indication in the RRC Connection (Resume) Request to inform the eNB whether the UL data transmission is completed in Msg3.

[0410] (2.1.2.Retransmission method) WID states that early data transmission will be carried out on dedicated resources.

[0411] It should be further considered whether RAN2's current agreement for early UL data transmission is actually supported by dedicated resources. RAN2 agreed to "Early UL Data Transmission in Msg3" where Msg3 resources are allocated by a dedicated UL grant in Msg2. The current Msg3 carries either an RRC connection request or an RRC connection resumption request via the CCCH logical channel, which is ultimately mapped to the PUSCH via the UL-SCH, but the contention for physical resources between UEs remains unresolved. Early UL data transmission is only supported for IDLE UEs, i.e., with a contention-based random access procedure.

[0412] Observation 1: In Msg3, the conflict is not resolved based on the RACH procedure.

[0413] In Msg3, more UL interference from multiple UEs is expected because contention is not resolved. In other words, reception errors of early UL data in Msg3 may occur. If the early UL data transmission is not successfully received, it is still unclear what the UE should do, i.e., how to retransmit the UL data that was not successfully received by the eNB.

[0414] Proposal 3: RAN2 should consider how the UE should retransmit early UL data if the data is not successfully received by the eNB.

[0415] If proposal 3 is acceptable, four options for the retransmission scheme are considered:

[0416] Option 2a: The UE restarts the random access procedure from Msg1, i.e. the previous procedure is canceled.

[0417] Option 2b: The UE may retransmit the failed data, ie, Msg3 with "Early UL Data Retransmission in Msg3".

[0418] Option 2c: The UE can retransmit the failed data in Msg5, i.e., if only the data fails.

[0419] Option 2d: The UE is allowed to retransmit failed data only after an RRC connection is established.

[0420] Option 2a is aligned with the current specification, i.e., flushing the Msg3 buffer and restarting from random access resource selection. Using Option 2a, it is unclear whether legacy or new backoff times are applied for early UL data retransmissions, and whether there is a limit on the number of retransmissions. Option 2b can follow Option 2a, i.e., the UE includes the failed data in the next Mg3 timing. Option 2c is a rare case, since it is unlikely that no data was received while the RRC connection (resume) request was successfully received, assuming the same MCS is applied. Option 2d is consistent with the current specification, except that retransmission of failed data is allowed.

[0421] Proposal 4: RAN2 should agree that if the Early UL data transmission fails, the UE should be allowed to restart the random access procedure (as it does now) and retransmit the data for the next Msg3.

[0422] In any case, the UE should maintain the data for early transmission until successful reception is confirmed, even if the Msg3 buffer is flushed.

[0423] (2.2. DL Early Data Transmission) (2.2.1. Consideration of email discussion) The email discussions jointly considered both early DL and early UL data transmissions, so DL aspects may not have been considered in detail. The next section provides such details.

[0424] (2.2.2. UE Support for Early DL Data Transmission) RAN2 has agreed to support Early DL data transmission in Msg4, which requires receiving data in Msg4 in addition to RRC Connection Setup / Resume / Release. However, it is questionable whether the eNB can always know whether the UE is capable of Early DL data reception, especially for UEs that are not suspended but are not suspended. Considering a unified solution for both CIoTEPSCP / UP optimization, the UE can inform the NW, i.e., eNB or MME, whether it can receive Early DL data.

[0425] Proposal 5: RAN2 should agree that the UE should inform the NW whether it supports early DL data reception.

[0426] From the eNB's perspective, there are two options for conveying the UE's capabilities to the NW, i.e., MME or UE. If the MME notifies the eNB, it is clear that some S1 messages need to be enhanced, such as PAGING or INITIAL CONTEXT SETUP REQUEST, and RAN2 should discuss with RAN3. On the other hand, if the UE notifies the eNB, several options are possible:

[0427] Option 3a: A new IE is added for UE capability of early DL data reception.

[0428] Option 3b: If the UE supports early DL data reception, an indication is sent in Msg1 or Msg3.

[0429] Option 3a is a simple way to provide the UE capability to the eNB, but the eNB needs to keep the context even if the UE is no longer connected or suspended, since the UE is forwarded after Msg4. Option 3b is a kind of "handshake", so the UE needs to know whether early DL data reception is intended before DL data reception starts, i.e., in paging or Msg2.

[0430] Proposal 6: RAN2 should consider whether the UE supports early DL data reception, i.e. how the eNB is informed by the UE or MME.

[0431] Regardless of Proposal 6, the UE needs to know whether it needs to set up early DL data reception before that happens.

[0432] Proposal 7: RAN2 should agree that the UE should be informed by paging or Msg2 whether early DL data reception is required.

[0433] (2.2.3.Retransmission method) Assume that early DL data transmission is performed on dedicated / non-contention resources, i.e., Msg4. However, reception errors can occur even on such resources, so the UE's behavior needs to be clarified. If early DL data transmission is indicated by paging or Msg2, i.e., proposal 7, it is straightforward for the UE to monitor the data transmitted on Msg4. As in proposal 4, a means of retransmission of DL data is required if the DL data is not received by the UE.

[0434] Proposal 8: RAN2 should agree that if Msg4 is not received, an early DL data retransmission is performed for Msg4.

[0435] (2.2.4. Simultaneous Early UL / DL Data Transmission) It remains unclear whether early data transmission should be supported simultaneously on both UL and DL within a single random access procedure. Generally, UL data transmission requires higher layer acknowledgment for the next DL, and vice versa, e.g., TCP ACK. After the UE decides to send a UL data transmission in Msg3, it may be possible to send an acknowledgment as DL data reception in Msg4 within one random access procedure. The DL data transmission in Msg4 cannot be followed by Mg3 in the same procedure. The higher layer acknowledgment as the UL data transmission must be sent in the next Msg3 occurring in the next random access procedure, or the UE could transition to an RRC connection, which would negate the purpose of sending early DL data.

[0436] However, it is unclear how much delay is required for such higher layer acknowledgment. If a higher layer round trip occurs within the random access procedure and the higher layer acknowledgment is delayed, the UE may continue to monitor Msg4 for a long time after transmitting Msg3, which will cause unnecessary power consumption in the UE. Therefore, it is reasonable to support early UL data transmission or early DL data transmission in a single random access procedure.

[0437] Proposal 9: RAN2 should agree that one random access procedure supports only one early data transmission, i.e., either early UL data transmission or early DL data transmission.

[0438] [Appendix 3] (1. Introduction) RAN2#99bis achieved significant progress in Early Data Transmission (EDT) capabilities with many agreements, including:

[0439] Agreement PRACH partitioning is used to indicate the UE's intention to use early data transmission in Msg3. Backward compatibility is maintained. Further study required: Details regarding PRACH pool, e.g. preamble / time / frequency / carrier domain for PRACH partitioning.

[0440] For CP during UL EDT procedure, if the UE receives a grant for which the data does not fit, the UE will not send data in Msg3. For UP solution, if the grant is smaller than the UL data size, further consideration is needed as to whether the EDT grant can be used for UL data.

[0441] -Further consideration is needed as to whether an authentication mechanism needs to be introduced.

[0442] The maximum grant size for Msg3 is broadcast per CE. Whether the UE indicates the required grant size for Msg3 via PRACH partitioning needs further study.

[0443] ·LS to RAN1, indicating that it is assumed that the conventional TBS table for PUSCH transmission is used for EDT.

[0444] Msg4 determines whether the UE transitions to RRC connected mode or RRC idle mode. The content of Msg4 in EDT needs further study.

[0445] The intention of using EDT is not for data, i.e. NAS signaling.

[0446] Send LS to RAN3 / SA2 / CT1 to determine whether any of the following parameters included in Msg5 of the legacy procedure should be included in Msg3 for EDT: selected PLMN-Identity, registered MME, gummei-Type, attach Without PDN-Connectivity, up-CIoT-EPS-optimized, cp-CIoT-EPS-optimized, dcn-ID.

[0447] RAN2 assumes that S-TMSI for CP, resumeID and shortResumeMAC-1 for UP solution are sufficient to identify the UE at MME and eNB, respectively. We apply this assumption to LS.toRAN3, SA2, SA3, and CT1.

[0448] For the CP solution, the NAS PDU for data is encapsulated in an RRC message sent in Msg3 and transmitted as a CCCH SDU.

[0449] For UP solutions, SRB0 is used to send RRC messages in Msg3.

[0450] In the UP solution, CCCH (RRC message) and DTCH (UP data) are multiplexed on the MAC of Msg3.

[0451] In the UP case, AS security is resumed before sending Msg3, and the data sent in Msg3 is protected by AS security.

[0452] For the CP solution, the NASPDU data in DL is encapsulated in an RRC message sent in Msg4 and sent as CCCHSDU.

[0453] For UP solutions, DL data can be arbitrarily multiplexed onto MAC within Msg4, i.e. DCCH (RRC messages) and DTCH (UP data).

[0454] Further consideration is needed: For UP solution: Fixed connection case, i.e. CCCH (RRC Connection Resume Req) + DCCH (NAS PDU for fixed connection)

[0455] This appendix discusses the remaining tasks to complete the basic functionality of EDT.

[0456] (2. Consideration) (2.1. Use Cases) During the discussion, there appears to be a common understanding that the EDT procedure is initiated by, for example, a UL EDT for upper layer sensor data and terminated by a DL EDT for the corresponding upper layer ACK, i.e., the upper layer round trip occurs within the EDT procedure.

[0457] On the other hand, UL-only EDT procedures and / or DL-only EDT procedures may also be useful in some cases. (See FIG. 26 for more comparisons. FIG. 26 shows EDT procedures.)

[0458] UDP type data transmission, i.e., without higher layer ACK.

[0459] · The upper layer round trip delay is long, i.e., the upper layer ACK requires a certain time before it responds.

[0460] Commands from the application server to the device, i.e., communication, are triggered by DL.

[0461] It is agreed that "For the CP solution, NAS PDU data in DL can be encapsulated in an RRC message sent in Msg4 and sent as a CCCH SDU," and "For the UP solution, DL data can be optionally multiplexed into MAC, i.e., DCCH (RRC message) and DTCH (UP data), in Msg4. That is, the UE can receive Msg4 without data." Therefore, it is considered that the UL-only EDT procedure is supported.

[0462] Observation 1: The current agreement supports UL-only EDT procedures.

[0463] On the other hand, the support for DL-only EDT procedures remains unclear in the current agreement. The availability of DL-EDT transmission cannot be known from the UE's perspective until Msg4 is received, and the ability to receive DL EDT is not possible. Therefore, if a UL EDT-capable UE also supports DL EDT, it will be notified without UL EDT from the eNB's perspective. Therefore, if DL-only EDT procedures are supported, further studies should address some extensions, such as notification in paging.

[0464] Note: It is assumed that a UE capable of UL EDT functionality is also capable of DL EDT functionality.

[0465] Proposal 1: RAN2 should consider whether DL-only EDT procedures are supported.

[0466] (2.2. Details of EDT Indication) In RAN2#99bis, it was agreed that "PRACH partitioning is used to indicate the UE's intention to use early data transmission in Msg3. Backward compatibility is maintained. Further study is needed: details about the PRACH pool such as preamble / time / frequency / carrier domain for PRACH partitioning" and "The maximum possible grant size for Msg3 is broadcast per CE. If the UE indicates the required grant size for Msg3 via PRACH partitioning, it needs further study."

[0467] The email discussion highlighted the need for further consideration, namely additional information on Msg1 and PRACH partitioning details. Regarding additional information on Msg1, the majority of the opinion seems to be that EDT indication is set per CE, but UE category is not required. There is no consensus on EDT indication, but this may be a future extension.

[0468] Proposal 2: RAN2 should agree that the EDT indication in Msg1 should be set per CE and that the grant size indication in Msg1 should be considered for future expansion.

[0469] Regarding the details of PRACH partitioning, two directions have been suggested: soft partitioning (or non-dedicated PRACH resources) and hard partitioning (or dedicated PRACH resources). In particular, the question is whether PRACH fragmentation is acceptable, since it may cause PRACH performance degradation in the case of limited resources in some NB-IoT deployment scenarios.

[0470] For example, sharing PRACH resources with soft partitioning in a non-optimized network has some advantages, but the number of partitions is the same as with hard partitioning. For example, with hard partitioning, six partitions are required for the PRACH resources due to the three legacy CE levels and the three EDT CE levels. With soft partitioning, six PRACH spaces (three CE levels x two different preambles) are also required. This means that there is no physical overstepping, i.e., the difference is in how UEs are separated.

[0471] Note: Hard partitioning allows for shared PRACH resources if the eNB configures legacy PRACH resources and EDT Indication PRACH resources with overlapping resources.

[0472] Therefore, in our view, regardless of the partitioning method (e.g., soft or hard), and regardless of whether dedicated or non-dedicated resources, the PRACH performance is ultimately similar in an optimized NW.

[0473] Observation 2: The performance of PRACH is ultimately similar among the solutions proposed in the email discussion.

[0474] An alternative solution not previously discussed in this paper is to define multiple PRACH transmissions from the UE to distinguish between legacy and UL-EDT PRACHs. For example, the UE could transmit one PRACH for legacy purposes (i.e., determining the CE level) and a second PRACH for EDT indication (i.e., only UEs requesting EDT transmit the second one). The eNB could perform blind decoding on the two PRACH spaces for each PRACH shot (see Figure 27, which illustrates EDT indication with multiple PRACH transmissions). The two PRACHs could be transmitted in the same subframe. With this approach, legacy UEs would only transmit the first PRACH as they do currently, requiring four PRACH resources (three CE levels for the first PRACH and one EDT indication for the second). However, the drawback of this solution is that it obviously requires the UE to transmit an additional PRACH, which incurs additional power consumption, which may be similar to the power consumption due to PRACH performance degradation (eg, collisions).

[0475] Proposal 3: RAN2 should consider whether multiple PRACH transmissions with one additional PRACH space would be useful for EDT indication.

[0476] Proposal 4: Once Proposal 2 and Proposal 3 reach an agreement, RAN2 should consider later whether grant size indication can be mapped to additional PRACH space.

[0477] (2.3. Examples of EDT failures) (2.3.1.UL Grant Failure (Msg1 / Msg2)) RAN2 agreed that "For CP during the ULEDT procedure, if the UE receives a grant that does not fit the data, the UE will not send data in Msg3. For the UP solution, if the grant is smaller than the UL data size, further consideration is needed if the EDT grant can be used for UL data." At least for the CP solution, even if the UE sends an EDT indication in Msg1, the eNB may reject the EDT procedure with a legacy size UL grant in Msg2. This can be considered a failure case from the perspective of the EDT procedure.

[0478] Observation 3: At least for the CP solution, the EDT procedure fails if the UL grant does not fit the data size.

[0479] The current agreement only states whether data can be transmitted on Msg3, i.e., does not mention what the UE should do if the UL grant is smaller than expected. Therefore, the UE behavior in case of failure should be specified, e.g., for testing. Some options need to be considered:

[0480] Option 1: The UE sends a legacy Msg3 (ie, no data).

[0481] Option 2: The UE may retry the EDT procedure (ie, starting from Msg1).

[0482] Option 1 may be a baseline based on our impressions during the study. Option 2 differs somewhat from the current behavior, i.e., the UE skips PUSCH transmission even if it receives a corresponding UL grant. However, since EDT is a new feature, it is worth considering introducing Option 2 as an option only if the eNB allows this feature, for example, to minimize unnecessary UE power consumption and transition to an RRC connection.

[0483] Proposal 5: RAN2 should agree that, at least for the CP solution, the UE will send legacy Msg3 if the UL grant size is not sufficient for the UL EDT.

[0484] Proposal 6: RAN2 should consider whether the UE is allowed to arbitrarily retransmit the EDT indication if the UL grant size is not large enough.

[0485] (2.3.2. Reception failed (Msg3 / Msg4)) There is no discussion on how to handle failure to receive data in the EDT procedure.

[0486] In the previous discussion of UL EDT, the UE behavior was assumed only when the UE receives Msg4, but it is not yet clear what happens if the UE does not receive Msg4. Several options have been considered, but it may be easier for the UE to follow the current random access procedure, i.e., restart from random access resource selection, so that UL EDT is also retried.

[0487] Proposal 7: RAN2 should agree that the UE restarts the random access procedure (and UL EDT procedure) from random access resource selection if contention resolution is deemed unsuccessful, as is the case currently.

[0488] Since the HARQ buffer is currently flushed when contention resolution is deemed unsuccessful, consideration should be given to where the data for retransmission is stored. From the perspective of the CP solution, traffic data is encapsulated as a NAS PDU within an RRC message. It is possible to encapsulate the traffic data at the RRC layer until data transmission is successfully completed. On the other hand, from the perspective of the UP solution, since the traffic data on the DTCH is multiplexed at the MAC layer, the traffic data is not stored at the RRC layer but at one of the user plane layers. Even if contention resolution is deemed unsuccessful, in order to have common UE behavior for CP and UP, the MAC layer should not flush the HARQ buffer.

[0489] Observation 4: In the RRT or MAC, it is unknown in which layer the data is stored until the UL EDT is successfully completed.

[0490] Proposal 8: RAN2 should agree that the MAC layer handles data retransmission in UL EDT.

[0491] In DL EDT, the failure to receive Msg4 is indicated by the HARQ feedback, so the data retransmission can simply follow the current HARQ retransmission.

[0492] Proposal 9: RAN2 should agree that DL EDT retransmissions are performed via Msg4 HARQ retransmissions, as is the case today.

[0493] (2.3.3.T300 and Contention Resolution Timer Failure (Msg3 / Msg4) In the current specification, there are two timers between RRC Msg3 and Msg4: T300 and MAC mac-Contention Resolution Timer. The value of T300 is between 100 ms and 2000 ms for LTE and between 2500 ms and 60000 ms for NB-IoT. The value of mac-Contention Resolution Timer is between sf8 and sf64 for LTE and between pp1 and pp64 for NB-IoT. When these timers expire, the UE considers that the RRC connection establishment / resumption or contention resolution, respectively, has not been successful.

[0494] If UL EDT is for sensor data transmission and DL EDT is for TCP ACK ("Full EDT procedure" in Figure 26), Msg4 transmission in the EDT procedure is likely to be delayed compared to conventional Msg4 due to the round trip time at the upper layer. Therefore, it is easy to define a longer timer value to prevent unnecessary errors.

[0495] Proposal 10: RAN2 should define a longer value for the timer that runs between UL EDT on Msg3 and DL EDT on Msg4.

[0496] However, this may cause additional UE power consumption due to continuous PDCCH monitoring until reception of Msg4. Therefore, a DRT-like reception mode needs to be introduced into the EDT procedure.

[0497] Proposal 11: RAN2 should consider whether discontinuous reception is acceptable in the EDT procedure (i.e., between sending Msg3 and receiving Msg4).

[0498] Furthermore, it is questionable how the eNB sets the timer value, because it does not know when the TCP ACK will be returned for the upper layer message. As it is assumed that there are many UEs in the cell that implement various applications, it seems difficult to set appropriate timer values ​​for all UEs.

[0499] One possibility is to configure Msg2 by itself, but it is still difficult to determine the timer value without knowledge of the application layer. On the other hand, the UE can help to set the appropriate timer value based on the timeout configuration in higher layers. For example, the UE can notify the eNB of its self-configured timer value in Msg3.

[0500] Proposal 12: RAN2 should consider whether the UE is allowed to notify the eNB of the self-configuration timer value on Msg3.

[0501] If any of Proposal 10 to Proposal 12 is preferred, the timer concept for EDT will be different from the legacy timer. Also, it is possible that an EDT-capable UE initiates a legacy RRC connection establishment / resumption, e.g., for larger packet transmissions, and thus the legacy timers are applicable in this case. Therefore, it is worth considering whether the timers for EDT should reuse the legacy timers or define new timers.

[0502] Proposal 13: RAN2 should consider whether the timer for EDT should reuse a legacy timer or define a new timer.

[0503] FIG. 28 shows the delay due to the round trip time of the upper layer.

[0504] (2.4. Authorization Mechanism) The chair's memo stated that "further consideration is needed as to whether an approval mechanism should be put in place." Such an approval mechanism was out of scope for the email discussions.

[0505] Our understanding is that EDT is an AS functionality and does not incur costs for the NW or UE (unlike CE). Furthermore, the NW can always disable the EDT functionality by removing the PRACH splitting parameters and / or the maximum possible grant size from the SIB. Therefore, there is no technical reason to introduce an authentication mechanism.

[0506] Proposal 14: RAN2 should agree that an authentication mechanism for EDT is not required.

[0507] [Appendix 4] (1. Introduction) RAN2#100 reviewed the details of the Early Data Transmission (EDT) indication on Msg1 and reached the following agreement:

[0508] Agreement ·The UE starts EDT with Msg1 if the size of Msg3 containing user data that the UE intends to transmit is equal to or smaller than the maximum possible TBS size of Msg3 broadcast per CE.

[0509] For each extended coverage level, a PRACH partitioning for EDT indication is configured.

[0510] · Working assumptions: Supporting segmentation in this case is not a priority.

[0511] · Operational assumption: PRACH resource partitioning is not supported to indicate intended data size other than legacy or maximum TBS broadcast per CE.

[0512] How to solve padding issues in Msg3

[0513] · UE category is not indicated in Msg1.

[0514] For EDT indication, PRACH resources can be configured like legacy eMTC or NB-IoT in terms of physical layer resources, preamble / subcarriers.

[0515] · The PRACH resource pool for EDACH indication, i.e. physical layer resources, preambles / subcarriers, is separate from the PRACH resource pool for legacy RACH procedures.

[0516] It was recognized that further study was needed on how to address the padding issue, which occurs when the UL grant for the ULEDT does not match the data size the UE is trying to send. The details of the issue are detailed in the corresponding email discussion.

[0517] This appendix provides additional context for the email discussion.

[0518] (2. Consideration) A solution to the padding problem was proposed and summarized in an email discussion as follows:

[0519] The following solutions to the above padding problem were presented:

[0520] 1. (N)PRACH Partitioning, where the UE indicates the intended data size / TBS for EDT Msg3 using Msg1.

[0521] 2. The network provides multiple transport block sizes and combinations of UL grant information: RU, PRB, and repetition count in the RAR message for the UE to select considering the intended data transmission in Msg3.

[0522] 3. The network provides double (or more) grants for sending Msg3.

[0523] 4. Combination of data size representation with Msg1 and flexible grant of RAR.

[0524] 5. Repetition of MAC SDUs or PDUs in padding areas (the details of this solution are unclear, but will be explained in detail for better understanding)

[0525] 6. Implicit allocation such as multiple common UL resource pools for Msg3 transmissions related to multiple "Max TBS broadcasts per CE" (the details of this solution are unclear but will be explained in detail for better understanding).

[0526] 7.UP only: Segmentation to avoid padding for legacy Msg3 transmissions.

[0527] (2.1. Solution 5 (MAC PDU Repetition)) This solution uses padding areas as redundancy opportunities. In other words, the existing repetition scheme on subframes is performed within the transmission. Examples are shown in Figures 29 and 30. Figure 29 shows the case where the UL grant is larger than the intended data size. Figure 30 shows the case where the UL grant is smaller than the intended data size.

[0528] One possibility is the physical layer, but which entity in that layer performs the additional redundancy process requires further study. For example, the UE generates a bit string from the MAC PDU, stores it in a circular buffer, and transmits the bits according to the UL grant size.

[0529] The expected advantages and disadvantages are as follows:

[0530] Advantages: Possibility of Rx soft combining gain and / or Tx power reduction to compensate for repetition compared to transmitting padding bits.

[0531] Disadvantages: There may be RAN1 impact if repetition is handled at the physical layer.

[0532] (2.2. Solution 6 (Common UL Resource Pool)) This solution provides a common UL resource pool for EDT, so that the resource pool is similar to the Mode 2 / Type 1 sidelink transmission, i.e., the common resources used by multiple UEs. Legacy Msg3 resources (as they are currently) are ) can be assumed to always be provided by the UL grant, but the UE can transmit the data portion using a common resource pool with the same temporary C-RNTI used in the legacy Msg3. The configuration of the common resource pool is provided in the SIB. This solution can be seen as a "semi-static" version of the multiple UL grant solution, whereby the second grant resource intended for data is shared by multiple UEs.

[0533] Figure 31 shows a common resource pool for UL transmission.

[0534] The advantages and disadvantages can be considered as follows:

[0535] Advantages: No changes to Msg2 are required. The UE can transmit data without padding (as long as the size does not exceed the common resources), assuming a sidelink-like transmission. Considering that EDT is an IDLE mode procedure, the use of common resources also makes sense, as is the case with Mode2 / Type1 resources. This means that resources can be allocated without dedicated signaling, which again emphasizes the idea that Msg2 does not need to be changed.

[0536] Disadvantages: Using common resources can lead to conflicts.

[0537] [Appendix 5] (1. Introduction) RAN2#100 has been accomplished to form a perspective on EDT function, but many details still need further study, one of which is as follows:

[0538] Agreement CP Solution [...] Further consideration is needed to determine whether changes to T300 and mac-contention Resolution Timer are necessary.

[0539] Further consideration of timer aspects is considered in this appendix.

[0540] (2. Consideration) (2.1.Premise) During the discussion, it appears to be a common understanding that the EDT procedure begins with a UL EDT, e.g., upper layer sensor data, and ends with a DL EDT, e.g., a corresponding upper layer ACK, i.e., an upper layer round trip, within the EDT procedure (i.e., see "Full EDT Procedure" in Figure 26).

[0541] Observation 1: Common EDT procedures include UL EDT and DL EDT (in the random access procedure).

[0542] On the other hand, the UL-only EDT procedure and / or the DL-only EDT procedure is also useful in the following cases (see FIG. 26).

[0543] UDP type data transmission, i.e., no upper layer ACK.

[0544] Longer delays in upper layer round trips, i.e., upper layer ACKs require a certain amount of time before being responded to.

[0545] Commands, i.e., communications, from the application server to the device are triggered by the DL.

[0546] The DL data of Msg4 is transmitted as CCCH SDUs, regardless of CP / UP, since in the case of CP solution, NAS PDU data in DL may be encapsulated or optionally encapsulated in the RRC message transmitted in Msg4, and in the case of UP solution, DL data can be optionally multiplexed with MAC of Msg4 (i.e. DCCH (RRC message) and DTCH (UP data)).

[0547] Observation 2: UL-only EDT procedures are supported under current agreements.

[0548] On the other hand, for DL-EDT transmission, the UE does not know whether DL EDT transmission will occur until it receives Msg4, and the eNB does not know the UE's DL EDT capability, so based on the current agreement, support for DL-only EDT procedures is still unknown.

[0549] Proposal 1: RAN2 should consider whether DL-only EDT procedures are supported.

[0550] (2.2.T300 and contention resolution timers) (2.2.1. Msg4 delay issue) In the current specification, there are two timers between Msg3 and Msg4 in RRC: T300 and MAC mac-Contention Resolution Timer. The value of T300 is 100 ms to 2000 ms in LTE and 2500 ms to 60000 ms in NB-IoT. The value of mac-ContentionResolutionTimer is sf8 to sf64 in LTE and pp1 to pp64 in NB-IoT. When these timers expire, the UE considers that the RRC connection establishment / resumption or contention resolution, respectively, has not been successful. It is still to be determined how the UE should behave when these existing timers expire under EDT, but it is also true that the current random access procedure is the baseline for EDT procedures. Therefore, further consideration regarding the timers is required.

[0551] If sensor data is sent via UL EDT and the corresponding TCP ACK is sent via DL EDT (i.e., see "Full EDT Procedure" in Figure 26), the Msg4 transmission in the EDT procedure will likely be different from the traditional Msg4 that depends on the round trip time from upper layers.

[0552] Observation 3: The duration between Msg3 and Msg4 is likely to exceed the maximum legacy timer due to the round trip time from the upper layer.

[0553] Therefore, it is easy to define a longer timer value to prevent unnecessary failures.

[0554] Proposal 2: RAN2 should define a longer value for the timer running between UL EDT on Msg3 and DL EDT on Msg4 for the Full EDT procedure.

[0555] (2.2.2.DRX for receiving Msg4) If Proposal 2 is convincing, it would be straightforward to extend the existing T300 and mac-Contention Resolution Timer timer values. However, this would cause additional UE power consumption due to continuous PDCCH monitoring until reception of Msg4, which may be delayed in EDT as described in the previous section. To avoid such unnecessary power consumption, some kind of DRX-like reception mode should be introduced into the EDT procedure.

[0556] For example, for a simple solution, the UE could monitor the PDCCH only in the subframe immediately before the timer expires, i.e., "one-shot" monitoring, which may work better than continuous monitoring for some MTC / NB-IoT use cases, such as high-latency communications.

[0557] Proposal 3: RAN2 should consider whether discontinuous reception is acceptable in the EDT procedure (i.e., between the transmission of Msg3 and the reception of Msg4).

[0558] (2.2.3. Setting the timer value) Furthermore, it is questionable how the eNB sets the timer value, because the time when the TCP ACK arrives from the upper layer message is unknown to the eNB. Assuming that there are many UEs implementing various applications in a cell, it is difficult for the eNB to set appropriate timer values ​​for all UEs.

[0559] Observation 4: Considering that different UEs may use different applications, it is difficult to set an appropriate timer value.

[0560] One possibility is to configure the timer using dedicated signaling in Msg2, but it is still difficult for the eNB to determine the timer value without knowledge of the application layer. On the other hand, the UE can help to set an appropriate timer value based on its timeout configuration in higher layers. For example, the UE can inform the eNB of its self-configured timer value on Msg3.

[0561] Proposal 4: RAN2 should consider whether the UE is allowed to notify the eNB of the self-configuration timer value on Msg3.

[0562] (2.2.4. Timer definition) If one or more of the above proposals (Proposal 2 to Proposal 4) are convincing, the concept of timers for EDT differs from traditional timers. Also, it is possible that an EDT-capable UE initiates a legacy RRC connection establishment / resumption, e.g., for larger packet transmissions, and thus legacy timers are applicable in this case. In this sense, it is easier to keep the existing timers as they are and define new timers specific to EDT instead of extending them.

[0563] Proposal 5: RAN2 should agree to define a new timer that operates between UL EDT (Msg3 and above) and DL EDT (Msg4 and above) instead of the legacy timer.

[0564] [Appendix 6] (1. Introduction) RAN2#100 has been accomplished to form a perspective on EDT function, but many details still need further study, one of which is as follows:

[0565] Agreement CP Solution [...] Further consideration is needed to determine whether changes to T300 and mac-contention Resolution Timer are necessary.

[0566] Further consideration of timer aspects is considered in this appendix.

[0567] (2. Consideration) (2.1.Premise) Proposal 1: RAN2 should consider whether DL-only EDT procedures are supported.

[0568] (2.2.T300 and contention resolution timers) (2.2.1. Msg4 delay issue) Observation 1: The duration between Msg3 and Msg4 in EDT is longer than conventional due to the round trip time from the upper layer.

[0569] Regarding the mac-Contention Resolution Timer, early contention resolution could be used to prevent the timer from expiring. For NB-IoTUE, it was agreed that Rel-14 and later will support early contention resolution, but whether it is an option requires further study.

[0570] Proposal 2: If early contention resolution is supported by EDT-capable NB-IoT UEs, RAN2 should agree that no changes to the mac-Contention Resolution Timer are required.

[0571] Regarding T300, it is directly affected by the round trip time from the upper layer. It is proposed to extend the timer value to take into account the retransmission and retransmission of CE mode B.

[0572] Therefore, it is easy to define a longer timer value to prevent unnecessary failures due to T300 expiry.

[0573] Proposal 3: RAN2 should define a longer value for the timer running between ULEDT on Msg3 and DLEDT on Msg4 to prevent unnecessary failures due to the expiration of T300.

[0574] (2.2.2.DRX for receiving Msg4) If Proposal 3 is convincing, it would be easy to extend the existing T300 timer value. However, this would cause additional UE power consumption due to continuous PDCCH monitoring until reception of Msg4, which may be delayed in EDT as described in the previous section. To avoid such unnecessary power consumption, some kind of DRX-like receive mode should be introduced into the EDT procedure.

[0575] For example, as a simple solution, the UE could monitor the PDCCH only in the subframe immediately before the timer expires, i.e., "one-shot" monitoring, which may work better than continuous monitoring for some MTC / NB-IoT use cases, such as high-latency communications

[10] .

[0576] Proposal 4: RAN2 should consider whether discontinuous reception is acceptable in the EDT procedure (i.e., between the transmission of Msg3 and the reception of Msg4).

[0577] (2.2.3. Setting the timer value) Furthermore, it is questionable how the eNB sets the timer value, since the time when the TCPACK arrives from the higher layer message is unknown to the eNB. Assuming that there are many UEs in a cell that implement various applications, it is difficult for the eNB to set appropriate timer values ​​for all UEs.

[0578] Observation 2: Considering that different UEs may use different applications, it is difficult to set an appropriate timer value.

[0579] One possibility is to set the timer using dedicated signaling in Msg2, but it is still difficult for the eNB to determine the timer value without knowledge of the application layer. On the other hand, the UE can help to set the appropriate timer value based on its timeout configuration in higher layers. For example, the UE can notify the eNB of its self-configured timer value on Msg3.

[0580] Proposal 5: RAN2 should consider whether the UE is allowed to notify the eNB of the self-configuration timer value on Msg3.

[0581] (2.2.4. Timer definition) If one or more of the above proposals (Proposal 3 to Proposal 5) are agreeable, the concept of timers for EDT differs from traditional timers. It is also possible that an EDT-capable UE initiates a legacy RRC connection establishment / resumption, e.g., for larger packet transmissions, and thus legacy timers are applicable in this case. In this sense, it is easier to keep the existing timers as they are and define new EDT-specific timers instead of extending them.

[0582] Proposal 6: RAN2 should agree to define a new timer that operates between UL EDT (Msg3 and above) and DL EDT (Msg4 and above) instead of the legacy timer.

[0583] [Appendix 7] (1. Introduction) RAN2#101 agreed on the following solution to the UL EDT padding issue:

[0584] Agreement ·EDT UL grants shall always allow the maximum TB size broadcasted in the system information, unless the provided UL grant is a legacy Msg3 one.

[0585] The EDT UL grant allows the UE to select an appropriate TB size, MCS, repetition count, and RU (for NB-IoT) from a set of provided TB sizes based on UL data. How the set of possible TB sizes, MCS, repetition count, and RU (for NB-IoT) is provided (e.g., hard-coded in the specification) needs further study. This is a pending RAN1 confirmation.

[0586] RAN2 assumes eight possible values ​​of maximum TB size broadcast in the system information. For each maximum TB size broadcast, RAN2 assumes that up to four possible TB sizes, i.e., blind decoding options, are allowed.

[0587] For eMTC, the reserved bits in MAC RAR can be used for the EDT function of eMTC only if necessary.

[0588] Capture the above agreement, including the agreement on the maximum and minimum possible TB sizes, and send the LS to RAN1, asking for confirmation from RAN1.

[0589] This appendix explores further how the solution works.

[0590] (2. Consideration) The TBS association in the solution under the current assumptions can be expressed as shown in Figure 32. Figure 32 shows the UL grant size and actual UL transmission for EDT.

[0591] From the UE's perspective, the UL grant for EDT with four blind decoding options allows the UE to select a TBS that minimizes the required padding bits. However, if the granted UL data size for EDT does not "fit" (at least for the CP solution), the UE may initiate legacy procedures and transition to RRC Connected. Therefore, from the UE's perspective, the maximum TBS and the number of blind decoding options should be set as high as possible.

[0592] Observation 1: The UE may initiate EDT if the maximum TBS and / or blind decoding options are a good "fit" for its UL data size.

[0593] In contrast, from the perspective of the network, the maximum TBS should be set as low as practically possible to minimize resource waste. Therefore, some implementations tend to set the maximum TBS value more conservatively. However, this setting has a direct impact on how many UEs utilize EDT, i.e., whether the network supports low-power operation of UEs. Since the network may not be aware of the required UL data sizes of UEs with various MTC applications, it is still unclear whether the network implementation has appropriate means to optimize the maximum TBS and blind decoding options.

[0594] Consideration 2: The usefulness of EDT depends on the optimal maximum TBS setting.

[0595] Observation 3: The settings of the maximum TBS and blind decoding options should be based on the UL data size requirements of the MTC application.

[0596] Taking the above observations into account, it should be considered whether the UE needs to provide feedback about its intended application (especially UL data size) as part of the network optimization.

[0597] Before the UE returns to RRC IDLE (e.g., sends RAI), the UE may have the opportunity to inform the eNB of its preferred TBS for EDT as assistance information. Assistance information is meaningful in the following cases:

[0598] Case 1: Similar to BSR, the information can be used as the expected data size of the next EDT, which can then be used as a reference for modifying the SIB settings.

[0599] Case 2: Similar to UE capabilities, the information may be used to determine whether an NCC should be provided to the UE for the next EDT possibility.

[0600] · Case 3: Similar to MDT, the information can be used for statistical analysis and network optimization.

[0601] Therefore, supporting information related to the operation of EDT should be introduced.

[0602] Proposal 1: RAN2 should agree to allow the UE to transmit assistance information for TBS configuration optimization, e.g., its preferred TBS.

[0603] Furthermore, if the UE falls back to legacy, i.e., after sending an EDT indication for Msg1 and receiving an UL grant for EDT, the UE may still send legacy Msg3, for example because additional UL data has been generated by the application. If that case needs to be taken into account, the EDT UL grant should always allow the blind decoding option for the legacy Msg3 size in addition to the four agreed options.

[0604] Proposal 2: RAN2 should consider whether EDT UL grants should always allow a legacy Msg3-sized blind decode option in addition to the four agreed-upon options.

[0605] [CROSS REFERENCE] This application claims priority to U.S. Provisional Application No. 62 / 543,469, filed August 10, 2017, U.S. Provisional Application No. 62 / 560,775, filed September 20, 2017, U.S. Provisional Application No. 62 / 564,430, filed September 28, 2017, U.S. Provisional Application No. 62 / 586,981, filed November 16, 2017, U.S. Provisional Application No. 62 / 627,313, filed February 7, 2018, U.S. Provisional Application No. 62 / 630,915, filed February 15, 2018, and U.S. Provisional Application No. 62 / 652,436, filed April 4, 2018, the contents of which are incorporated herein in their entireties.

Claims

1. 1. A communication method comprising: a user equipment being in a predetermined RRC state in which a UE context is maintained in a network, transmitting, during a random access procedure, a first message to a network node for transmitting uplink user data as a predetermined data transmission during the random access procedure; receiving, by the user equipment after transmitting the first message, information to stop the predetermined data transmission together with a second message to maintain the user equipment in the predetermined RRC state from the network node; performing the predetermined data transmission at least once by the user device after sending the first message and before receiving the second message. Communication method.

2. receiving, by the user equipment, a message including information regarding the predetermined data transmission, the message being for transitioning the user equipment from an RRC connected state to the predetermined RRC state; The user equipment transitions from the RRC connected state to the predetermined RRC state in response to receiving the message; and determining whether to execute the predetermined data transmission based on the information included in the message. The communication method according to claim 1 .

3. A user device, a transmitter configured to transmit, during a random access procedure, a first message to a network node, when the user equipment is in a predetermined RRC state in which a UE context is maintained in a network; and a receiving unit configured to receive, after transmitting the first message, information for stopping the predetermined data transmission from the network node together with a second message for maintaining the user equipment in the predetermined RRC state; a control unit that performs the predetermined data transmission at least once after transmitting the first message and before receiving the second message. User equipment.

4. A chipset for controlling a user device, comprising: transmitting, during a random access procedure, a first message to a network node, when the user equipment is in a predetermined RRC state in which a UE context is maintained in a network; and transmitting uplink user data as a predetermined data transmission during the random access procedure. receiving, after transmitting the first message, information to stop the predetermined data transmission from the network node together with a second message to maintain the user equipment in the predetermined RRC state; performing the predetermined data transmission at least once after transmitting the first message and before receiving the second message; Chipset.

5. a network node, a receiving unit configured to receive, during a random access procedure, from a user equipment in a predetermined RRC state in which a UE context is maintained in a network, a first message for transmitting uplink user data as a predetermined data transmission during the random access procedure; a transmitter configured to, after receiving the first message, transmit to the user equipment a second message for maintaining the user equipment in the predetermined RRC state and information for stopping the predetermined data transmission; The receiver receives the predetermined data transmission at least once after receiving the first message and before transmitting the second message. Network node.

6. To the user device, transmitting, during a random access procedure, a first message to a network node, when the user equipment is in a predetermined RRC state in which a UE context is maintained in a network; and transmitting uplink user data as a predetermined data transmission during the random access procedure. receiving, after transmitting the first message, information to stop the predetermined data transmission from the network node together with a second message to maintain the user equipment in the predetermined RRC state; and executing a process of performing the predetermined data transmission at least once after transmitting the first message and before receiving the second message. program.

7. A system comprising a user equipment and a network node, The user device When the user equipment is in a predetermined RRC state in which a UE context is maintained in a network, during a random access procedure, sending a first message to the network node for transmitting uplink user data as a predetermined data transmission during the random access procedure; receiving, after transmitting the first message, information to stop the predetermined data transmission from the network node together with a second message to maintain the user equipment in the predetermined RRC state; After transmitting the first message and before receiving the second message, the predetermined data transmission is performed at least once. system.

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