Method and apparatus for robust small data transmission in wireless network

Abstract

The present disclosure relates to a method, apparatus and user equipment for receiving small data transmissions terminated by a mobile terminal in a wireless communication network. The method comprises the steps of: receiving (203), in an inactive state, a paging notification (202) from a base station, the paging notification (202) comprising at least an indication that downlink small data is available for transmission and a priority flag (PF) associated with said downlink small data; determining (204) at least one synchronization signal reference signal received power; and deferring (205) downlink data reception until a next paging cycle when the priority flag (PF) indicates low priority downlink data and all of the at least one synchronization signal reference signal received power (SSB RSRP) is below a threshold. The disclosure also relates to a method and apparatus for performing small data transmission by a base station.

Description

Technical Field

[0001] The present application relates generally to wireless communications, and more particularly to apparatus and methods for improving Mobile Terminated Small Data Transfer (MT-SDT) in a Radio Resource Control (RRC) inactive state. Background Art

[0002] Because the transition from the RRC inactive or RRC idle state to the RRC connected state may cause overhead to the user equipment (UE) when only a small amount of data is to be transmitted, the 3rd Generation Partnership Project (3GPP) has introduced techniques for optimizing the transmission of such small packets. In practice, the UE needs to exchange multiple control signals to initiate and maintain a connection with the network. When the payload size is relatively small compared to the amount of control signals required, establishing a connection becomes a concern for both the network and the UE due to the control signaling overhead.

[0003] Small Data Transfer (SDT) in RRC Inactive state has been introduced in 3GPP Release 17 for 5G NR to reduce the signaling overhead and UE power consumption for infrequent data transmission. This allows the UE to transmit sporadic small amounts of data in RRC Inactive state without the need for RRC state transition.

[0004] The RRC inactive state is introduced to maintain the AS (Access Stratum) context at the base station and the UE, with the aim of reducing energy consumption and the number of messages exchanged between the user equipment and the base station. In the RRC inactive state, the user equipment and the base station suspend their radio connection, but the AS context is retained in the user equipment and the base station.

[0005] Depending on how the radio resources are configured, 3GPP defines two types of SDT: SDT using random access (RA-SDT) and SDT using pre-configured grants (CG-SDT). RACH (Random Access Channel)-based SDT allows SDT to be performed using an uplink grant for SDT received via a random access procedure. CG-based SDT allows SDT to be performed using a configured grant in an RRC inactive state without performing a random access procedure.

[0006] Small data transmission using preconfigured radio resources is referred to as transmission via PUR (preconfigured uplink resources) in the LTE standard and as transmission via CG-SDT (configuration grant-based SDT) in the 5G NR standard. The base station configures the radio resources when the user equipment transitions from RRC connected to RRC inactive state, for example with an RRC release message including the radio resource configuration of PUR for CG-SDT.

[0007] Small data transmission using random access is called EDT (Early Data Transfer) in the LTE standard and RA-SDT (Random Access-based SDT) in the 5G NR (New Radio) standard. Data is transmitted using shared radio resources using a random access procedure.

[0008] Basically, when the base station needs to send a small amount of data to a user equipment in the RRC inactive state, the base station sends a paging notification to the user equipment. Such paging messages are sent in SSB (Signal Synchronization Block) using QPSK (Quadrature Phase Shift Keying) modulation for the Physical Downlink Control Channel (PDCCH), so that the user equipment can decode the message even under low RSRP (Reference Signal Received Power) conditions. However, the actual downlink data transmission cannot be carried by QPSK modulation under low RSRP conditions and may suffer from errors, resulting in packet retransmissions and overhead.

[0009] In addition, the UE may receive a paging notification indicating SDT in RRC_INACTIVE when the RSRP of the SSB is not above the preconfigured threshold. In such a situation, downlink SDT retransmission may occur, which will result in more power consumption and signaling overhead.

[0010] Therefore, there is a need for an efficient way to transmit small data in the RRC inactive state. Summary of the invention

[0011] In one aspect, a method for receiving a small data transmission by a user equipment connected to a wireless communication network is provided. The method comprises the following steps:

[0012] receiving a paging notification from a base station in an inactive state, the paging notification including at least: an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data,

[0013] determining at least one synchronization signal reference signal received power, and

[0014] When the priority flag indicates low priority downlink data and the at least one synchronization signal reference signal received power is lower than a threshold, downlink data reception is postponed until a next paging cycle.

[0015] Therefore, it is envisaged that the paging notification sent by the base station serving the user equipment to notify that downlink small data is available includes an indication of the priority of the downlink data. The priority indication can be a binary flag indicating whether the available small data has a high priority. In the case where none of the RSRP (synchronization signal reference signal received power SS-RSRP) of the SSB is higher than a preconfigured threshold (i.e., when the user equipment is experiencing poor radio conditions), the user equipment may decide to postpone the reception of the small data to the next paging cycle.

[0016] This avoids the transmission of non-urgent small data when experiencing poor network conditions, thus avoiding packet retransmissions and signaling overhead while reducing power consumption.

[0017] In this application, the terms "send" and "transmit" are equivalent and interchangeable.

[0018] According to an embodiment, when the priority flag indicates high priority downlink data and the at least one synchronization signal reference signal received power is lower than a threshold, the method comprises the following steps:

[0019] A paging response is sent that includes at least a flag indicating that the at least one synchronization signal reference signal received power is below a threshold, and downlink data is received from a base station, the downlink data being transmitted using a low modulation scheme selected by the base station based on the indication that all of these at least one synchronization signal reference signal received power are below the threshold.

[0020] Therefore, it is proposed that the user equipment sends a flag indicating that the RSRP of all SSBs is below a threshold in response to a paging notification.Such an arrangement allows the serving base station to adapt its behavior to the signal quality experienced by the user equipment, for example by transmitting small data to be processed using a low MCS (Modulation Coding Scheme).

[0021] In some examples, the user equipment transmits the indication to the base station via a 2-step RACH (Random Access Channel), a 4-step RACH, or a CG (Pre-Configured Grant).

[0022] According to an embodiment, when the priority flag indicates high priority downlink data and the at least one synchronization signal reference signal received power is lower than a threshold, the method comprises the following steps:

[0023] A paging response is sent, the paging response including at least a quality flag indicating that all of the at least one synchronization signal reference signal received power are below a threshold, and an instruction to skip downlink data is received.

[0024] Therefore, it is proposed that the user equipment sends a flag indicating that the RSRP of all SSBs is below a threshold in response to a paging notification. Such an arrangement allows the serving base station to adapt its behavior according to the signal quality experienced by the user equipment, for example by skipping a small data transmission and scheduling it in the next paging cycle. In this case, the small data transmission can be rescheduled and transmitted in one of the following paging cycles. That is, the transmission can be rescheduled.

[0025] According to an embodiment, the steps of sending a paging response and receiving an instruction to skip downlink data until the next paging cycle are repeatedly performed, the paging response comprising at least a flag indicating that all of the at least one synchronization signal reference signal received power are below a threshold; and if a stop criterion occurs, the step of receiving downlink data from the base station is performed, the downlink data being transmitted using a low modulation scheme selected by the base station.

[0026] In other words, a combination of the two measures (i.e., receiving small data transmitted in a low modulation scheme and skipping or rescheduling) is possible. That is, for example, if the rescheduling is unsuccessful because the radio conditions have not improved, the base station may select a low modulation scheme for transmission, which may then be received by the user equipment. A stopping criterion may be defined for stopping the rescheduling and switching to the selected low modulation scheme.

[0027] According to an embodiment, the stopping criterion is one of a preconfigured number of repetitions, another flag in the paging message, another flag in the paging response message, or detected static or degraded radio conditions.

[0028] According to an embodiment, the preconfigured number of repetitions is configured in the base station and / or the user equipment.

[0029] The present disclosure also contemplates an apparatus for receiving a small data transmission (SDT) from a base station in a wireless communication network, the apparatus comprising a processor coupled to a memory having computer program instructions stored therein, the instructions configured to implement the following steps:

[0030] receiving a paging notification from a base station in an inactive state, the paging notification including at least: an indication that downlink data is available for transmission and a priority flag associated with the downlink data,

[0031] determining at least one synchronization signal reference signal received power, and

[0032] When the priority flag indicates low priority downlink data and the at least one synchronization signal reference signal received power is below a threshold, downlink data reception is postponed until at least a next paging cycle.

[0033] According to an embodiment, the device further includes a scheduler unit configured to postpone downlink data reception until at least the next paging cycle when the priority flag received by the communication unit indicates low priority downlink data and when the channel quality sensor determines that the RSRP of all SSBs measured are lower than the threshold.

[0034] The scheduler unit may be configured to determine the data cycle for transmission of small data that has not yet been sent according to one of different algorithms. Such an algorithm may be to select the next paging cycle, to select a fixed number or a varying number (such as a random number) or to increase or decrease the paging cycles to be skipped, or the algorithm may even take into account measured radio conditions. Other criteria or any mixture of these criteria may be applied.

[0035] Further envisaged is a user equipment comprising an apparatus for receiving a small data transmission as described above.

[0036] The present disclosure also relates to a method for sending a small data transmission by a base station in a wireless communication network, wherein the method comprises:

[0037] transmitting a paging notification to a user equipment in an inactive state, the paging notification comprising at least: an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data,

[0038] receiving a paging response including at least an indication that all of at least one synchronization signal reference signal received power are below a threshold, and

[0039] Downlink data is transmitted using a modulation scheme selected based on the received synchronization signal reference signal received power indication.

[0040] According to an embodiment, in a case where the priority flag indicates high priority downlink data, the step of transmitting downlink data using a modulation scheme selected based on the received synchronization signal reference signal received power indication is preceded by the step of receiving a paging response and transmitting an instruction for skipping the downlink data until the next paging cycle, the paging response including at least a flag indicating that all of these at least one synchronization signal reference signal received powers are below a threshold.

[0041] In an embodiment, the base station serving the user equipment can therefore send an indication of the priority associated with the available downlink small data in the paging notification. The priority indication can be a binary flag indicating whether the available small data has a high priority. Such an indicator enables the user equipment to adapt its behavior in the case of a low-quality radio signal. For example, the user equipment can skip downlink data transmission until the next or another paging cycle. In some embodiments, the user equipment can send a response containing a signal quality indicator (for example, an indication of the fact that the RSRP of all SSBs is lower than a threshold), and the base station can use the response to select a robust MCS to transmit the pending small data. The measurement of skipping small data transmission can be repeatedly performed, and the measurement can be optionally stopped when the stop criterion is met, and then the small data is transmitted using a low modulation scheme. The stop criterion can be, for example, one of a preconfigured number of repetitions, another flag in a paging message, another flag in a paging response message, or a detected static or degraded radio condition. Preferably, if low priority data is to be transmitted, the download is skipped or rescheduled, and if high priority data is to be transmitted, a low modulation scheme is used. Alternatively, if high priority data is to be transmitted, the download is performed in the next cycle. The combination may be performed accordingly for low priority data (where transmission is postponed first) or high priority data (where transmission is performed first in the next paging cycle), i.e., the base station attempts to send the data in the following paging cycle and then transmits the data with a low modulation scheme. An apparatus for performing small data transmission in a wireless communication network is also contemplated, the apparatus comprising a wireless transceiver and a processor coupled to a memory having computer program instructions stored therein, the instructions being configured to implement the following steps:

[0042] transmitting a paging notification to a user equipment in an inactive state, the paging notification comprising at least: an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data,

[0043] receiving a paging response, the paging response including at least one indication that a synchronization signal reference signal received power is below a threshold, and

[0044] Downlink data is transmitted using a modulation scheme selected based on the received synchronization signal reference signal received power indication.

[0045] A base station is further envisaged, the base station comprising an apparatus for performing a small data transmission as described above.

[0046] The present disclosure further relates to a wireless communication system, the wireless communication system comprising a base station and a user equipment, the wireless communication system for performing a small data transmission from the base station to the user equipment, wherein the base station comprises a processor coupled to a memory having computer program instructions stored therein, the instructions being configured to implement the following steps:

[0047] Transmitting a paging notification to a user equipment in an inactive state, the paging notification comprising at least: an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data, wherein the user equipment comprises a processor coupled to a memory having computer program instructions stored therein, the instructions being configured to implement the following steps:

[0048] receiving the paging notification from the base station in an inactive state, the paging notification comprising at least: an indication that downlink data is available for transmission and a priority flag associated with the downlink data,

[0049] determining at least one synchronization signal reference signal received power, and

[0050] When the priority flag indicates low priority downlink data and all of the at least one synchronization signal reference signal received power are below a threshold, downlink data reception is postponed until at least a next paging cycle.

[0051] In some embodiments, the various steps of the method for receiving a small data transmission by a user equipment and / or the method for sending a small data transmission by a base station are determined by instructions of a computer program.

[0052] Therefore, the present disclosure further contemplates computer programs on an information medium, which are suitable for implementation in a user equipment and a base station, respectively, or more generally in a computer, which programs respectively include instructions adapted to implement the steps of the wireless communication method disclosed herein, which is supported by the user equipment and performed by the base station, respectively.

[0053] These programs may use any programming language and may be in the form of source code, object code, or an intermediate code between source code and object code, such as partially compiled form or any other desired form.

[0054] On the other hand, an information medium readable by a computer is envisaged, which information medium comprises instructions of a computer program such as mentioned above.

[0055] The information medium may be any entity or device capable of storing a program. For example, the medium may include a storage device such as a ROM (read-only memory) (e.g., a CD ROM or a microelectronic circuit ROM), an EEPROM (electrically erasable programmable read-only memory), a FLASH memory, or any magnetic recording device (e.g., a hard disk drive).

[0056] Furthermore, the information medium may be a transmissible medium such as an electric signal or an optical signal that can be transmitted via an electric or optical cable by radio or by other means.The program according to the embodiment of the present invention may be downloaded from a network.

[0057] Alternatively, the information medium may be an integrated circuit in which the program is embodied, the circuit being arranged to execute or to be used for executing the method in question.

[0058] The advantages of the device, user equipment, base station, system, corresponding computer program and information medium are the same as those of the device, user equipment, base station, system, corresponding computer program and information medium presented in relation to the method for receiving small data and the method for executing small data according to any one of the embodiments mentioned above. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Other advantages and characteristics of the invention will become more apparent on reading the following description, given by way of simple illustrative and non-limiting examples, and the accompanying drawings, in which:

[0060] Figure 1 A wireless system including user equipment and a base station in which aspects of the present disclosure may be practiced is presented.

[0061] Figure 2 is a simplified diagram showing an example of low priority small data transmission terminated by a UE in an RRC inactive state according to an embodiment,

[0062] Figure 3a is a simplified diagram showing an example of high priority small data transmission terminated by a UE in an RRC inactive state according to an embodiment,

[0063] Figure 3b is a simplified diagram showing an example of high priority small data transmission terminated by a UE in an RRC inactive state according to an embodiment,

[0064] Figure 4 is a flow chart depicting the main steps of a state machine suitable for implementing a method for receiving a small data transmission by a user equipment according to an embodiment,

[0065] Figure 5 is a flow chart showing the main steps of a state machine suitable for implementing a method for performing small data transmission by a base station according to an embodiment,

[0066] Figure 6 is a flow chart depicting the main steps of a state machine suitable for implementing a method for receiving a small data transmission by a user equipment according to another embodiment,

[0067] Figure 7 is a flow chart showing the main steps of a state machine suitable for implementing a method for performing small data transmission by a base station according to another embodiment,

[0068] Figure 8 is a block diagram showing a schematic architecture of an apparatus suitable for implementing a wireless communication method for receiving a small data transmission (SDT) from a base station according to an embodiment, and

[0069] Fig. 9 is a block diagram showing a schematic architecture of an apparatus suitable for implementing a wireless communication method for small data transmission (SDT) to a user equipment according to an embodiment. DETAILED DESCRIPTION

[0070] The specific embodiments described below with reference to the accompanying drawings are intended as descriptions of various configurations and are not intended to represent the only configurations in which the concepts described herein may be practiced. The specific embodiments include specific details to provide a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In particular, although terminology from 3GPP 5G NR may be used in this disclosure to illustrate the embodiments herein, this should not be viewed as limiting the scope of the invention.

[0071] Figure 1 An exemplary 5G New Radio (NR) wireless communication system 100 including user equipment 101 and base station 102 in which aspects of the present disclosure may be practiced is shown. Wireless network 100 may be an LTE network or some other wireless network, such as an LTE, 5G, or NR network. Wireless network 100 may include one or more base stations 102. Depending on the wireless standard implemented, base station 102 may be referred to as a BS, NB, eNodeB (or eNB), gNodeB (or gNB), access point, etc. Base station 102 provides radio communication coverage for a specific geographic area called a "cell".

[0072] The user device 101 may be referred to as a mobile station, a wireless terminal, etc. In some examples, the user device 101 may be a cellular phone, a wireless modem, a wireless communication device, a handheld device, a laptop computer, etc. The user device 101 may also be an IoT (Internet of Things) device like a wireless camera, a smart sensor or smart meter, a vehicle, a global positioning system device, or any other device configured to communicate over a wireless network.

[0073] The user equipment 101 may support various communication modes, such as a connected mode (RRC connected), an inactive mode (RRC inactive), or an idle mode (RRC idle) defined by 3GPP. When operating in the RRC connected mode, the user equipment 101 is active and communicates with the base station 102. The user equipment 101 may transition from one communication mode to another using various commands and messages received from the base station 102. For example, the user equipment 101 may switch from the RRC connected state to the RRC inactive state upon receiving an RRC release message including a suspendConfig parameter.

[0074] When there is no traffic, the user equipment 101 can enter the RRC inactive state without completely releasing radio resources so as to quickly switch back to the RRC connected state when necessary. In this case, the user equipment and the base station can store a context (e.g., an access layer (AS) context) for the user equipment so as to apply the stored context when transitioning from the RRC inactive state to the RRC connected state, thereby reducing latency and signaling overhead. Such context may include radio configuration parameters such as uplink grants, RNTI (Radio Network Temporary Identifier), MCS, etc.

[0075] However, while the user equipment 101 is in the RRC inactive state, the radio conditions may have changed. For example, the user equipment 101 may have moved to another location, so the channel quality changes.

[0076] Figure 2 is a simplified diagram showing an example of low priority small data transmission terminated by a UE in an RRC inactive state according to an embodiment.

[0077] During preliminary step 200, the user equipment 101 may switch to the RRC inactive state in response to an RRC release message with a suspendConfig parameter. An I-RNTI (Inactive Radio Network Temporary Identifier) ​​may be allocated to the user equipment 101 as part of the suspendConfig parameter within such RRC release message.

[0078] When the user equipment 101 is in the RRC inactive state, the base station 102 may receive small downlink data destined for the user equipment 101 at step 201. The downlink data may include small amounts of data such as keep-alive packets, sensor data, push notifications, location data, etc. The base station 102 may transmit a paging notification 202 to the user equipment 101 to inform the user equipment 101 of the available downlink data, the paging notification including at least an identifier associated with the user equipment 101, such as an I-RNTI.

[0079] In some embodiments, the paging notification includes an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data. The priority flag can be a one-bit binary flag set by the base station 102 when the received data has a high priority. The high priority flag can be set according to many factors such as data priority, data volume threshold, traffic pattern, etc. In some examples, the paging notification message can include a one-bit PagingDLdataInformation field in the PagingUE-Identity data structure defined by the 3GPPTS38.331 specification.

[0080] The user equipment 101 receives the paging notification 202 at step 203 and decodes the priority flag set by the base station 102 .

[0081] At step 204, the user equipment 101 may measure the signal quality and determine at least one synchronization signal reference signal received power.

[0082] According to an embodiment, if the user equipment receives "0" (i.e., low priority data) in the paging message 202, and if the RSRP of all SSBs determined at step 204 is lower than the preconfigured threshold, it can skip the random access (RA) process at step 205 and return to sleep mode and wake up in the next paging cycle. The threshold can be an RSRP threshold defined by 3GPP. Therefore, small data reception is skipped in this cycle, and in one of the following cycles, if the RSRP of at least one SSB is higher than the preconfigured threshold, small data reception can be performed.

[0083] Figure 3a is a simplified diagram showing an example of high priority small data transmission terminated by a UE in an RRC inactive state according to an embodiment.

[0084] During preliminary step 300, user equipment 101 may switch to RRC inactive state in response to an RRC release message with a suspendConfig parameter. An I-RNTI (Inactive Radio Network Temporary Identifier) ​​may be allocated to user equipment 101 as part of the suspendConfig parameter within such RRC release message.

[0085] When the user equipment 101 is in the RRC inactive state, the base station 102 may receive small downlink data destined for the user equipment 101 at step 301. The downlink data may include small amounts of data such as keep-alive packets, sensor data, push notifications, location data, etc. The base station 102 may transmit a paging notification 302 to the user equipment 101 to inform the user equipment 101 of the available downlink data, the paging notification including at least an identifier associated with the user equipment 101, such as an I-RNTI.

[0086] In some embodiments, the paging notification 302 may include an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data. In some examples, the priority flag may be a one-bit PagingDLdataInformation field included in the PagingUE-Identity data structure defined by the 3GPP TS 38.331 specification.

[0087] The priority flag may be a one-bit binary flag set by the base station 102 if the received data has a high priority. The high priority flag may be set based on many factors like data priority, data volume threshold, traffic pattern, etc. Figure 3a In the example of , the paging notification 302 includes a priority flag set to "1", which indicates that high priority data is pending.

[0088] The user equipment 101 receives the paging notification 302 at step 303 and decodes the priority flag set by the base station 102 .

[0089] At step 304, the user equipment 101 may determine at least one synchronization signal reference signal received power (SSBRSRP). Figure 3a In the example of , it is considered that the RSRP of all SSBs is below the threshold (ie, experiencing poor radio quality).

[0090] If the user equipment 101 receives a "1" in the paging notification message, meaning that high priority data is pending, the user equipment may trigger the RA-SDT or CG-SDT process at step 305, and inform the base station 102 that the RSRP result of the SSB is below the threshold via 2-step RACH / 4-step RACH / CG. The base station 102 may be informed that the RSRP of the SSB is below the threshold in the paging response message 306. In some examples, a radio quality flag (e.g., a bit or a CQI index) may be set in the message 306 to indicate that the RSRP of the SSB determined at step 304 is below the threshold.

[0091] According to an embodiment, the base station 102 may receive the paging response 306 at step 307, and based on the received flag, it may select a lower / more robust modulation scheme to transmit data to the user equipment 101. At step 308, the base station 102 may send the small data in a message 309 using the MCS selected at step 307. In this way, in the event that the user equipment 101 experiences poor radio conditions, the user equipment 101 may receive urgent data at step 311 while limiting retransmission risk, signaling overhead, and power consumption.

[0092] according to Figure 3b In the embodiment shown in FIG. 3 , instead of selecting a low MCS based on the received quality flag at step 307 and sending small data at step 308, the base station 102 may take a skip decision at step 311 and schedule the DL SDT in the next paging cycle when the quality flag indicates that the RSRP of all SSBs is below the threshold. If the base station decides to skip the downlink SDT, during step 312, the base station 102 may configure a second wake-up cycle using message 313 (e.g., msgB (2-step RACH) or msg4 (4-step RACH) or MAC CE (in the case of configuration grant (CG))). The user equipment may then configure wake-up according to the second wake-up cycle at step 314 to receive downlink small data. In this way, the base station 102 may avoid sending data when no SSB RSRP has a suitable quality, thereby limiting the risk of retransmission and signaling overhead.

[0093] Figure 4 is a flow chart depicting the main steps of a state machine suitable for implementing a method for receiving a small data transmission by a user equipment according to an embodiment.

[0094] At step S400, the user equipment waits for a paging notification when in an RRC inactive state. Upon receiving a paging notification at a serving base station indicating that small data is available for transmission, the user equipment decodes the received notification and checks at step S401 whether a priority flag and a value of the priority flag are included. When the priority flag is included in the received paging notification and indicates that the small data to be processed has a low priority, the user equipment may then skip the random access procedure at step S402 and wait for the next paging cycle.

[0095] On the other hand, when it is found at step S401 that the data to be processed has a high priority, the user equipment triggers a random access procedure at step S403 and indicates to the base station that the RSRP of the SSB is lower than the threshold, and receives a downlink SDT at a low MCS configured by the base station based on the RSRP indication during step S404, or in an alternative embodiment, the user equipment receives an indication to skip downlink data until the next paging cycle.

[0096] Figure 5 is a flow chart illustrating main steps of a state machine suitable for implementing a method for performing small data transmission by a base station according to an embodiment.

[0097] At step S500, the base station may receive some small data for transmission to the user equipment in RRC inactive state. The base station may prepare a paging notification including an indication of the priority of the data to be transmitted as already described above, and transmit the paging notification to the user equipment.

[0098] At step S501, a base station may receive a message from a user equipment in response to a paging notification. The message may include a flag indicating whether the RSRP of all SSBs is below a preconfigured threshold.

[0099] When the flag does indicate to the base station that the RSRP of all SSBs is below the threshold, the base station may perform step S502 during which the base station may decide to schedule the SDT in another paging cycle, or the base station may perform data transmission using a low MCS in step S504.

[0100] Figure 6 Shown based on Figure 4 Flow chart of the main steps of a state machine suitable for implementing a method for performing small data transmission by a base station according to another embodiment of the embodiment shown in FIG. Figure 4 In the case that the data to be received has not been sent by the base station and step S402 is to be repeatedly performed, in an additional step S405 before step S402, it is checked whether a stopping criterion is met. Such a stopping criterion may be, for example, one of a preconfigured number of repetitions, another flag in the paging message, another flag in the paging response message, or detected static or degraded radio conditions. If the stopping criterion is met, data is received according to the low modulation scheme instead of skipping the reception.

[0101] Figure 7 It is shown based on Figure 5 Flow chart of the main steps of a state machine according to another embodiment suitable for implementing a method for performing small data transmission by a base station. When skipping or rescheduling transmission, it is possible to repeat Figure 5In the case that the data to be transmitted has not been sent by the base station and step S502 is to be performed again, before performing step S502 again, it is checked whether a stopping criterion is met. Such a stopping criterion may be, for example, one of a preconfigured number of repetitions, another flag in the paging message, another flag in the paging response message, or a detected static or degraded radio condition. If the stopping criterion is met, data is transmitted according to the low modulation scheme in step S504 instead of skipping reception.

[0102] Figure 8 is a block diagram showing a schematic architecture of an apparatus 600 suitable for implementing a wireless communication method for receiving a small data transmission (SDT) from a base station according to an embodiment.

[0103] The apparatus 600 comprises a processor 601 and a memory 602, such as a random access memory (RAM). The processor 601 may be controlled by a computer program 603 stored in the memory 602, the computer program comprising instructions configured to implement a method for receiving a small data transmission (SDT) from a base station in a wireless communication network.

[0104] More specifically, the computer program 603 includes instructions for receiving a paging notification from a base station in an inactive state, the paging notification including at least an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data; determining at least one synchronization signal reference signal received power, and when the priority flag indicates low priority downlink data and the at least one synchronization signal reference signal received power is below a threshold, postponing downlink data reception until the next paging cycle.

[0105] At initialization, the instructions of the computer program 603 may be loaded into the memory 602 before being executed by the processor 601. The processor 601 implements the steps of the method according to the instructions of the computer program 603.

[0106] The device 600 includes a wireless communication unit 604 for exchanging messages with other devices, such as a 3G, 4G, 5G, 5GNR, WiFi or WiMax transceiver. In particular, the communication unit 604 is configured by program instructions to receive a paging notification broadcast by a base station and to check whether the received paging is addressed to the device by comparing an identifier included in the paging notification with an identifier associated with the device. The communication unit 605 can be further configured to obtain an indication of a priority associated with available small data from the paging notification. The indication can be a binary flag included in the PagingUE-Identity data field of the paging notification, wherein the flag is set to indicate high priority small data.

[0107] The apparatus 600 further comprises a channel quality sensor 605. The channel quality sensor may be configured by computer program instructions to measure the signal strength on one or more available SSBs (synchronization signal blocks) and compare the measured value with a preconfigured threshold to determine whether the RSRP of all SSBs is below the threshold.

[0108] According to an embodiment, the apparatus 600 further comprises a scheduler unit 606. The scheduler unit 606 may be configured by computer program instructions to postpone downlink data reception until the next paging cycle when the priority flag received by the communication unit 604 indicates low priority downlink data and when the channel quality sensor 605 determines that the RSRP of all the measured SSBs is below the threshold.

[0109] In some embodiments, the apparatus 600 may include a random access module 607 configured by computer program instructions to initiate a random access procedure. The random access procedure may include sending a quality indicator determined by a channel quality sensor 605 to a serving base station via a communication unit 604. In some examples, the quality indicator is sent as a binary flag that is set to indicate that the RSRP of all SSBs is below a preconfigured threshold.

[0110] According to an embodiment, the communication unit 604 is further configured by computer program instructions to receive downlink data from a base station, wherein the downlink data is transmitted using a low modulation scheme selected by the base station based on the at least one synchronization signal reference signal received power being lower than a threshold.

[0111] In some embodiments, the apparatus 600 is included in a user device like a smart phone, a laptop, an IoT (Internet of Things) device, or a vehicle.

[0112] Fig. 9 is a block diagram showing a schematic architecture of an apparatus 700 suitable for implementing a wireless communication method for small data transmission (SDT) to a user equipment according to an embodiment.

[0113] The apparatus 700 comprises a processor 701 and a memory 702, such as a random access memory (RAM). The processor 701 may be controlled by a computer program 703 stored in the memory 702, the computer program comprising instructions configured to implement a method for receiving a small data transmission (SDT) from a base station in a wireless communication network.

[0114] More precisely, the computer program 703 includes instructions configured to transmit a paging notification to a user equipment in an inactive state, the paging notification including at least an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data; receive a paging response including at least an indication that at least one synchronization signal reference signal received power is below a threshold; and transmit downlink data using a modulation scheme selected based on the received synchronization signal reference signal received power indication.

[0115] At initialization, the instructions of the computer program 703 may be loaded into the memory 702 before being executed by the processor 701. The processor 701 implements the steps of the method according to the instructions of the computer program 703.

[0116] The device 700 includes a wireless communication unit 704 for exchanging messages with other devices, such as a 3G, 4G, 5G, 5GNR, WiFi or WiMax transceiver. In particular, the communication unit 704 is configured by program instructions to transmit a paging notification to an inactive user equipment when small data is available for download, the paging notification comprising at least an indication that downlink small data is available for transmission and a priority flag associated with the downlink small data. According to an embodiment, the indication can be a binary flag included in the PagingUE-Identity data field of the paging notification, wherein the flag is set to indicate high priority small data.

[0117] The wireless communication unit 704 may be further configured by computer program instructions to receive a response to the paging notification from the user equipment, and to obtain a quality indicator indicating whether the RSRP of all SSBs measured by the user equipment is lower than a preconfigured threshold from the received response.

[0118] In some embodiments, the apparatus 700 further comprises a modulation scheme selector module 705. The MCS selector module may be configured by computer program instructions to select a low MCS when the quality indicator received by the communication unit 704 indicates that the RSRP of all SSBs determined by the user equipment is below a preconfigured threshold.

[0119] The communication unit 704 may be further configured by computer program instructions to transmit downlink data using the MCS selected by the MCS selector module 705; that is, when the RSRP of all SSBs measured by the user equipment is below a threshold, small data is transmitted using a low MCS.

[0120] According to an embodiment, the apparatus 700 may include a skipping module 706 configured to skip the small data transmission and schedule it into the next paging cycle when the received quality indicator indicates that the RSRP of all SSBs is below a threshold.

[0121] In some embodiments, the apparatus 700 is included in a base station similar to a gNodeB or an eNodeB.

[0122] List of Reference Numerals

[0123] 101 User Equipment

[0124] 102 Base Station

[0125] 200 The user equipment switches to the RRC inactive state

[0126] 201 The base station receives a small downlink data packet destined for the user equipment.

[0127] 202 Paging notification message, enter sleep mode

[0128] 203 User equipment receives paging notification

[0129] 204 The user equipment measures the signal quality and determines the SSB RSRP

[0130] 205 Skip / postpone small data reception

[0131] 300 User equipment switches to RRC inactive state

[0132] 301 The base station receives a small downlink data packet destined for the user equipment.

[0133] 302 Paging notification message

[0134] 303 User equipment receives paging notification

[0135] 304 The user equipment determines the SSB RSRP

[0136] 305 The user equipment triggers the RA-SDT or CG-SDT process

[0137] 306 Paging Response Message

[0138] 307 Base station receives paging response

[0139] 308 Base station sends small data

[0140] 309 Small data message

[0141] 311 User device receives small data

[0142] S400 to S404 method steps

[0143] S500 to S505 method steps

[0144] 600 Devices

[0145] 601 Processor

[0146] 602 Memory

[0147] 603 Computer Programs

[0148] 604 Communication Unit

[0149] 605 Channel Quality Sensor

[0150] 606 Scheduler Unit

[0151] 607 Random Access Module

[0152] 700 Devices

[0153] 701 Processor

[0154] 702 Memory

[0155] 703 Computer Programs

[0156] 704 Wireless Communication Unit

[0157] 705 MCS Selector Module

[0158] 706 Skip module

Claims

1. A method for receiving a small data transmission by a user equipment connected to a wireless communication network, wherein: The method includes: A paging notification is received (203) from a base station in an inactive state, the paging notification comprising at least: An indication that downlink small data is available for transmission, and a priority flag (PF) associated with the downlink small data, determining (204) at least one synchronization signal reference signal received power, When the priority flag (PF) indicates low priority downlink data and all of the at least one synchronization signal reference signal received power are below a threshold, downlink data reception is postponed (205) until the next paging cycle.

2. The method according to claim 1, wherein: The method comprises when the priority flag indicates high priority downlink data and the at least one synchronization signal reference signal received power is lower than a threshold: sending a paging response, the paging response comprising at least a flag indicating that all of the at least one synchronization signal reference signal received power are below a threshold, and Downlink data is received from the base station, the downlink data being transmitted using a low modulation scheme selected by the base station based on the indication that all of at least one synchronization signal reference signal received power are below a threshold.

3. The method according to claim 2, wherein: The step of sending a paging response is performed by the user equipment through a 2-step random access channel RACH, a 4-step RACH or a pre-configured grant CG, and the paging response includes at least a flag indicating that all of the received powers of at least one synchronization signal reference signal are below a threshold.

4. The method according to claim 1, wherein: The method comprises when the priority flag indicates high priority downlink data and the at least one synchronization signal reference signal received power is lower than a threshold: sending a paging response, the paging response comprising at least a flag indicating that all of the at least one synchronization signal reference signal received power are below a threshold, and An instruction is received to skip downlink data until the next paging cycle.

5. The method according to claim 3, wherein: Repeating the steps of sending a paging response and receiving an instruction to skip downlink data until the next paging cycle, the paging response comprising at least a flag indicating that all of the at least one synchronization signal reference signal received power are below a threshold; and if a stop criterion occurs, performing the step of receiving downlink data from the base station, the downlink data being transmitted using a low modulation scheme selected by the base station.

6. The method according to claim 5, wherein: The stopping criterion is one of the following: Preconfigured number of repetitions; Another flag in the paging message; Another flag in the paging response message; or Static or degraded radio conditions detected.

7. The method according to claim 5, wherein: The preconfigured number of repetitions is configured in the base station and / or the user equipment.

8. An apparatus for receiving a small data transmission (SDT) from a base station in a wireless communication network, the apparatus comprising a wireless transceiver (704), a processor (601) coupled to a memory (602) having computer program instructions (603) stored therein, the instructions being configured to implement the following steps: Receive a paging notification from a base station in an inactive state, the paging notification at least including: an indication that downlink data is available for transmission, and a priority flag associated with the downlink data, determining at least one synchronization signal reference signal received power, When the priority flag indicates low priority downlink data and the at least one synchronization signal reference signal received power is below a threshold, downlink data reception is postponed until at least a next paging cycle.

9. The device according to claim 8, wherein: The apparatus 600 further includes a scheduler unit 606 configured to postpone reception of downlink data until at least the next paging cycle when the priority flag received by the communication unit 604 indicates low priority downlink data and when the channel quality sensor 605 determines that the RSRP of all measured SSBs is below the threshold.

10. A user equipment, comprising the apparatus according to claim 8 or 9.

11. A method for performing small data transmission by a base station in a wireless communication network, wherein: The method includes: A paging notification (302) is transmitted (301) to a user equipment in an inactive state, the paging notification comprising at least: An indication that downlink small data is available for transmission, and a priority flag (PF) associated with the downlink small data, receiving (307) a paging response (306) comprising at least an indication that all of at least one synchronization signal reference signal received power are below a threshold (QF), and Downlink data is transmitted (308) using a modulation scheme selected based on the received synchronization signal reference signal received power indication.

12. The method according to claim 11, wherein: The step of transmitting (308) downlink data using a modulation scheme selected based on the received synchronization signal reference signal received power indication is preceded by the step of receiving a paging response and transmitting an instruction for skipping downlink data until the next paging cycle, the paging response comprising at least a flag indicating that all of at least one synchronization signal reference signal received power are below a threshold.

13. An apparatus for performing small data transmission in a wireless communication network, the apparatus comprising a wireless transceiver (704) and a processor (701) coupled to a memory (702) having computer program instructions (703) stored therein, the instructions being configured to implement the following steps: Transmitting a paging notification to a user equipment in an inactive state, the paging notification comprising at least: An indication that downlink small data is available for transmission, and a priority flag associated with the downlink small data, receiving a paging response including at least an indication that all of at least one synchronization signal reference signal received power are below a threshold, and Downlink data is transmitted using a modulation scheme selected based on the received synchronization signal reference signal received power indication.

14. A base station comprising the device according to claim 13.

15. A wireless communication system for performing small data transmission from a base station to a user equipment, the wireless communication system comprising a base station and a user equipment, wherein: The base station comprises a processor coupled to a memory having computer program instructions stored therein, the instructions being configured to implement the following steps: Transmitting a paging notification to a user equipment in an inactive state, the paging notification comprising at least: An indication that downlink small data is available for transmission, and a priority flag associated with the downlink small data, The user equipment comprises a processor coupled to a memory having computer program instructions stored therein, the instructions being configured to implement the following steps: The paging notification is received from the base station in an inactive state, and the paging notification at least includes: an indication that downlink data is available for transmission, and a priority flag associated with the downlink data, determining at least one synchronization signal reference signal received power, When the priority flag indicates low priority downlink data and all of the at least one synchronization signal reference signal received power are below a threshold, downlink data reception is postponed until at least a next paging cycle.

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