Method and apparatus for robust small data transmission in wireless network

Abstract

The present invention relates generally to wireless communications, and more particularly, to an apparatus and method for improving mobile terminal terminated small data transmission (MT-SDT) in a radio resource control (RRC) inactive state. A method for transmitting small data transmission, SDT, data from a base station, gNB (102), to a user equipment, UE (101), comprises the steps of: setting (300) the UE (101) to an inactive state (RRCINACTIVE); providing (301), by the gNB (102), SDT data; sending (302, 820) a paging notification from the gNB (102) to the UE (101), the paging notification comprising a backoff parameter value, BPV, range; receiving (810), by the UE (101), the BPV range; and selecting (812), by the UE (101), a backoff time according to the BPV range.

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 / effective data 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] The purpose of this application is to specify support for mobile terminated small data transfer (MT-SDT) triggered by paging. On the one hand, a MT-SDT triggering mechanism is provided for UEs in RRC_INACTIVE, supporting RA-SDT and CG-SDT as UL responses; on the other hand, a mobile terminated small data transfer (MT-SDT) process is provided for initial downlink (DL) data reception and subsequent uplink / downlink (UL / DL) data transmission in RRC_INACTIVE.

[0010] After receiving the paging message, the UE initiates a RA (random access) procedure (ie, 2-step RA or 4-step RA) to receive small data transmission under RRC_INACTIVE.

[0011] The UE selects a preamble in the preamble group. The gNB feeds back a Random Access Response (RAR) to the UE that sent the preamble in Msg1 / MsgA. In the RAR, the gNB indicates a BI (Backoff Indicator) taking into account the cell load. Once the UE fails in RA, for example, the RAR does not include the preamble sent by the UE in Msg1 / MsgA, or the contention resolution in Msg4 / MsgB is considered unsuccessful, the UE will randomly select a backoff time between 0 and BI and retransmit the preamble after the backoff time.

[0012] The current backoff time selection is that the UE selects a random backoff time between 0 and the backoff parameter value (BPV).

[0013] A UE with a smaller backoff parameter value will select a backoff time between [0, small BPV], while a UE with a larger backoff parameter value will select a backoff time between [0, large BPV]. For example, if the BI field value is 10, the backoff parameter value is 320ms. This means that from now on, the UE can send PRACH at any time between 0ms and 320ms.

[0014] Since the lower range of backoff times is overlapping for all SDT UEs, more UEs will select backoff times in the lower range of BPV.

[0015] As a result, during the RACH process, there is a high probability of collision between multiple UEs. Due to the high probability of collision, the UE may need to retransmit the PRACH more times, which will result in greater power consumption and signaling overhead, which is undesirable for small data.

[0016] according to Fig. 9 For example, if UE1 receives a BI value of 10 at time T PRACH opportunity, UE1 can send PRACH at any time between 0ms and 320ms. If UE2 receives a BI value of 6 at time Δ+T PRACH opportunity, UE2 can send PRACH at any time between 0ms and 80ms. As a result, the lower range of backoff times (i.e., 0ms to 80ms) overlaps between UE1 and UE2, and UE1 may have a higher probability of selecting a backoff time between 0ms and 80ms.

[0017] The present invention provides corresponding solutions to the described problems.

[0018] Application DE 102 022 207 895 is incorporated into the present application by reference.

[0019] based on Fig. 9 , when the UE triggers the RA procedure in RRC_INACTIVE, it selects the BPV indicated in the paging message. The gNB configures the UE-specific BPV range in the paging message based on the UE's priority and data volume threshold. The gNB configures a lower BPV for higher data volume threshold / higher data priority UEs, and a higher BPV for lower data volume threshold / lower data priority UEs. UEs with higher data volume threshold / higher data priority have the highest RACH priority.

[0020] Benefit: The UE selects a specific backoff time based on traffic characteristics rather than randomly. Therefore, RACH congestion will be reduced because the backoff times do not overlap. As a result, the UE will not need to transmit more PRACH transmissions, so signaling overhead and power consumption will be reduced. Summary of the invention

[0021] 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: receiving (203) a paging notification from a base station in an inactive state, the paging notification comprising at least:

[0022] A user equipment (UE) specific backoff parameter value (BPV) range in a paging message based on a user equipment (UE) priority and / or data volume threshold;

[0023] A lower backoff parameter value (BPV) is configured for a higher data volume threshold and / or higher data priority UE, and a higher backoff parameter value (BPV) is configured for a lower data volume threshold and / or lower data priority UE.

[0024] 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.

[0025] According to another embodiment, the method is characterized in that a User Equipment (UE) with a higher data volume threshold and / or a higher data priority has the highest RACH priority.

[0026] According to another embodiment, the method is characterized in that signaling overhead and / or power consumption is reduced when the User Equipment (UE) does not need to send a greater number of PRACH transmissions.

[0027] One aspect relates to 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 apparatus being configured to perform a method as described above and / or below.

[0028] One aspect relates to a user equipment comprising an apparatus as described above and / or below.

[0029] One aspect relates to a method for performing small data transmission by a base station in a wireless communication network, wherein the method comprises: transmitting (301) a paging notification (302) to a user equipment in an inactive state, the paging notification comprising at least:

[0030] A user equipment (UE) specific backoff parameter value (BPV) range in a paging message based on a user equipment (UE) priority and / or data volume threshold;

[0031] A lower backoff parameter value (BPV) is configured for a higher data volume threshold and / or higher data priority UE, and a higher backoff parameter value (BPV) is configured for a lower data volume threshold and / or lower data priority UE.

[0032] One aspect relates to an apparatus for performing small data transmission in a wireless communication network, the apparatus comprising a wireless transceiver (704), a processor (701) coupled to a memory (702) having computer program instructions (703) stored therein, the apparatus being configured to perform a method as described above and / or below.

[0033] One aspect relates to a wireless communication system for performing small data transmission from a base station to a user equipment, wherein the base station includes a processor coupled to a memory having computer program instructions stored therein, and the communication system is configured to perform a method as described above and / or below, wherein the user equipment includes a processor coupled to a memory having computer program instructions stored therein, and the processor is configured to perform a method as described above and / or below.

[0034] One aspect relates to a method for transmitting small data transmission (SDT) data from a base station gNB to a user equipment UE, the method comprising the following steps:

[0035] Set the UE to inactive state;

[0036] The gNB provides SDT data.

[0037] Sending a paging notification from the gNB to the UE, the paging notification including the backoff parameter value BPV range;

[0038] Receiving, by the UE, a BPV range; and

[0039] The UE selects the backoff time according to the BPV range.

[0040] The base station may be a 5G base station using new radio (NR) technology. The base station may be designated as a gNB or a gNodeB base station. The UE may be configured to support 5G protocols. The methods described above and / or below may preferably be applied to a UE in a so-called RRC_INACTIVE state as defined by 3GPP. The 3GPP definition may also define conditions and circumstances under which the UE is set to the RRC_INACTIVE state. The gNB may be informed of the RRC_INACTIVE state of the UE. When the UE is in the RRC_INACTIVE state, data may be received by the gNB that is suitable for transmission as SDT data. Examples of such "SDT data candidates" (further referred to as "SDT data" for simplicity) may be data sent by an Internet of Things (IoT) device, or any other type of data that requires only a small amount of data to be transmitted.

[0041] When the UE is in RRC_INACTIVE state and SDT data is available, the gNB may send a so-called paging notification to the UE. The paging notification may include several types of data. One of them may be a BPV range, short for "Backoff Parameter Value (BPV) Range". The BPV may be encoded by a so-called Backoff Indicator (BI) field. The BI field may be a 4-bit field, as in Fig. 9 As depicted. For example, if the BI field value is 10, the BPV is 320ms. This indicates that there may be a time delay between 0ms and 320ms between a PRACH and the next PRACH. A BPV range may contain one or more BPVs. For example, a BPV range of "(0,7)" may define a backoff parameter value between 0ms and 120ms, while a BPV range of "(7,9)" may define a backoff parameter value between 120ms and 240ms.

[0042] The UE then receives the BPV range (possibly encoded by a 2-tuple of BI values) and selects a backoff time according to the BPV range, i.e. applies the BPV range or backoff time range, in order to prepare and / or perform its next protocol step. The next protocol step may be to skip the SDT, such as in Figure 2 The next protocol step may be to initiate and / or perform random access based SDT (RA-SDT), e.g. Figure 3a , Figure 3b , Figure 4 or Figure 8 a.

[0043] This may advantageously result in reduced congestion, for example because the UE selects a specific backoff time rather than a random one. Thus, RACH congestion may be reduced due to reduced or avoided overlap of backoff times. Furthermore, the UE may not need to transmit more than one PRACH transmission, which may reduce signaling overhead and power consumption of the communication system, particularly for UEs which are typically equipped with rechargeable batteries.

[0044] In various embodiments, the UE performs the selection only when the priority flag indicates a high priority and the radio signal quality is above a predefined threshold. Under other conditions, the selection and / or further protocol steps may be skipped and / or postponed to a later point in time, for example, waiting for the next paging cycle. The priority flag may be a binary flag that is set to a value of "1" by the base station when the received data has a high priority, or may be set to "0" to indicate a low priority. The high priority flag may be set according to several factors, such as data priority, data volume threshold, traffic pattern, and / or other factors. The paging notification message may, for example, include a PagingDLdataInformation field in a PagingUE-Identity data structure defined by the 3GPP TS38.331 specification. The radio signal quality may be a function of RSRP (reference signal received power), and / or may be indicated by a so-called radio quality flag. This may advantageously force the sending and / or receiving of urgent data, but may further limit the number of retransmissions, the signaling overhead of the system, and / or the power consumption, especially when network conditions are poor.

[0045] In various embodiments, the method further comprises the following steps: performing a random access based SDT (RA-SDT) by the gNB with a backoff time for PRACH transmission according to the BPV range. PRACH transmission means a transmission via a physical random access channel PRACH. When receiving a paging message, the UE may initiate a so-called RA procedure (RA; Random Access), such as a 2-step RA procedure or a 4-step RA procedure, to receive an SDT in the RRC_INACTIVE state. This may advantageously have the effect that the UE does not need to perform more than one PRACH transmission, thereby further reducing signaling overhead and / or power consumption of the UE.

[0046] In various embodiments, for the amount of data of the SDT data above a predefined data amount threshold DV1, the BPV range is between zero and a first BPV value BPV1, and for the amount of data below the predefined data amount threshold DV1, the BPV range is between the first BPV value BPV1 and a second BPV value BPV2. An example order of magnitude of DV1 may be between 10 bytes and 1000 bytes, for example 100 bytes. Due to constraints and / or settings of the network and / or UE, the amount of data of the SDT may additionally have a general upper limit ("DV2"). In some embodiments, there may be one or more data amount thresholds between DV1 and DV2, which may result in further corresponding (multiple) definitions of the BPV range.

[0047] In various embodiments, for high UE priority, the BPV range is between zero and a first BPV value BPV1, and for low UE priority, the BPV range is between the first BPV value BPV1 and a second BPV value BPV2. The UE priority may be determined by the network or gNB based on the amount of latency or other QoS values ​​for data that the UE can guarantee. The BPV range may be determined based on UE priority only, based on the amount of data, based on both values, and / or based on other values. This may allow higher UE priority and / or higher amount of data to have higher priority.

[0048] One aspect relates to a method for transmitting small data transmission (SDT) data by a base station gNB, the method comprising the following steps:

[0049] Provide SDT data; and

[0050] When the user equipment UE is in an inactive state, a paging notification is sent to the UE, where the paging notification includes a backoff parameter value BPV range.

[0051] In various embodiments, the method further comprises the step of performing a random access based SDT (RA-SDT) with a backoff time for PRACH transmission according to the BPV range upon receiving the paging response.

[0052] One aspect relates to a method for receiving small data transmission (SDT) data by a user equipment (UE), the method comprising the following steps:

[0053] Set the UE to inactive state;

[0054] A paging notification is received, the paging notification including a backoff parameter value (BPV) range; and a backoff time is selected according to the BPV range.

[0055] One aspect relates to a wireless communication system configured to transmit small data transmission (SDT) data from a base station gNB to a user equipment UE as described above and / or below.

[0056] One aspect relates to a base station gNB, which is configured to transmit small data transmission (SDT) data as described above and / or below.

[0057] One aspect relates to a user equipment UE configured to receive small data transmission SDT data as described above and / or below.

[0058] One aspect relates to a non-transitory computer-readable storage medium having a program stored thereon, which, when executed on a base station gNB, instructs the gNB to perform a method as described above and / or below.

[0059] One aspect relates to a non-transitory computer-readable storage medium having a program stored thereon, which, when executed on a user equipment UE, instructs the UE to perform the method as described above and / or below.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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).

[0065] 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.

[0066] 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.

[0067] 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

[0068] 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:

[0069] Figure 1 A wireless system including user equipment and a base station in which aspects of the present disclosure may be practiced is presented.

[0070] 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,

[0071] 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,

[0072] 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,

[0073] 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,

[0074] 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,

[0075] Figure 6 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

[0076] Figure 7is a block diagram showing a schematic architecture of an apparatus suitable for implementing a wireless communication method for performing small data transmission (SDT) to a user equipment according to an embodiment.

[0077] Figure 8 a. Figure 8 b 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 and a user equipment according to a further embodiment,

[0078] Fig. 9 A backoff parameter value table is shown accordingly.

[0079] Fig.10 The relationship between the data volume of SDT data and the BPV range is shown. DETAILED DESCRIPTION

[0080] 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.

[0081] 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".

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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, and thus the channel quality changes.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] The user equipment 101 receives the paging notification 202 at step 203 and decodes the priority flag set by the base station 102 .

[0091] At step 204, the user equipment 101 may determine at least one synchronization signal reference signal received power.

[0092] 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 a preconfigured threshold, it may skip the random access (RA) procedure at step 205 and return to sleep mode and wake up in the next paging cycle. The threshold may be an RSRP threshold defined by 3GPP.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] The user equipment 101 receives the paging notification 302 at step 303 and decodes the priority flag set by the base station 102 .

[0099] 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).

[0100] If the user equipment 101 receives "1" in the paging notification message, which means that high priority data is pending, the user equipment can 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 lower than the threshold through 2-step RACH / 4-step RACH / CG. The base station 102 can be informed that the RSRP of the SSB is lower than the threshold in message 306. In some examples, a radio quality flag (e.g., a bit or a CQI index) can be set in the message 306 to indicate that the RSRP of the SSB determined at step 304 is lower than the threshold.

[0101] 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.

[0102] according to Figure 3bIn 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] When the flag does indicate to the base station that the RSRP of all SSBs are 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.

[0110] Figure 6 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] Figure 7 is a block diagram showing a schematic architecture of an apparatus 700 suitable for implementing a wireless communication method for performing small data transmission (SDT) to a user equipment according to an embodiment.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] In some embodiments, the apparatus 700 is included in a base station like a gNodeB or an eNodeB.

[0130] Figure 8 a. Figure 8 b 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 and a user equipment according to a further embodiment,

[0131] Another embodiment is an example based on a data volume approach.

[0132] The gNB configures the backoff parameter range of the data volume (DV1) to [BPV1, BPV2] and the backoff parameter range of DV2 to [0, BPV1], where DV1 <DV2;

[0133] If the gNB wants to transmit a total data volume lower than DV1 to the UE, a backoff time between BPV1 and BPV2 is configured in the paging message;

[0134] The UE selects a backoff time between BPV1 and BPV2;

[0135] If the gNB wants to transmit a total data volume higher than DV1 to the UE, a backoff time between 0 and BPV1 is selected;

[0136] The UE selects a backoff time between 0 and BPV1;

[0137] UEs receiving a higher amount of data are given priority for PRACH transmission.

[0138] Another embodiment is an example based on a data priority approach.

[0139] The gNB configures the backoff parameter range of the data volume (DV1) to [BPV1, BPV2] and the backoff parameter range of DV2 to [0, BPV1], where DV1 <DV2;

[0140] If the gNB wants to transmit a total data volume lower than DV1 to the UE, a backoff time between BPV1 and BPV2 is configured in the paging message;

[0141] The UE selects a backoff time between BPV1 and BPV2;

[0142] If the gNB wants to transmit a total data volume higher than DV1 to the UE, a backoff time between 0 and BPV1 is selected;

[0143] The UE selects a backoff time between 0 and BPV1;

[0144] UEs receiving a higher amount of data are given priority for PRACH transmission.

[0145] Fig. 9 A backoff parameter value table is shown accordingly.

[0146] Fig.10 The relationship between the data volume of SDT data and the BPV range according to an embodiment is shown. The y-axis of the graph depicts the data volume, where the data volume is 0 (zero), DV1, and DV2. In the case where the data volume of the SDT data is higher than the predefined data volume threshold DV1, the BPV range is between zero and the first BPV value BPV1. In the case where the data volume of the SDT data is lower than the predefined data volume threshold DV1, the BPV range is between the first BPV value BPV1 and the second BPV value BPV2.

[0147] The last two methods cited in the examples can be combined with all other methods disclosed accordingly.

[0148] This feature is most beneficial for messaging and presence applications in sensors, IoT devices, and even smartphones.

Claims

1. A method for transmitting small data transmission (SDT) data from a base station gNB (102) to a user equipment UE (101), the method comprising the following steps: Setting (300) the UE (101) to an inactive state (RRC_INACTIVE); The SDT data is provided (301) by the gNB (102); Sending (302, 820) a paging notification from the gNB (102) to the UE (101), the paging notification including a backoff parameter value BPV range; Receiving (810) the BPV range by the UE (101); as well as The UE (101) selects (812) a backoff time according to the BPV range.

2. The method according to claim 1, in, The UE (101) performs the selection only when the priority flag indicates a high priority and the radio signal quality is above a predefined threshold.

3. The method according to any one of the preceding claims, further comprising the steps of: A random access based SDT (RA-SDT) is performed by the gNB (102) with a backoff time for PRACH transmission according to the BPV range.

4. A method as claimed in any one of the preceding claims, in, For a data volume of the SDT data above a predefined data volume threshold (DV1), the BPV range is between zero and a first BPV value (BPV1), and For a data volume lower than the predefined data volume threshold (DV1), the BPV range is between the first BPV value (BPV1) and the second BPV value (BPV2).

5. A method as claimed in any one of the preceding claims, in, For high UE priority, the BPV range is between zero and a first BPV value (BPV1), and For low UE priority, the BPV range is between the first BPV value (BPV1) and the second BPV value (BPV2).

6. A method for transmitting small data transmission (SDT) data by a base station gNB (102), the method comprising the following steps: Providing (301) the SDT data; as well as When the user equipment UE (101) is in an inactive state (RRC_INACTIVE), a paging notification is sent (302, 820) to the UE (101), the paging notification including a backoff parameter value BPV range.

7. The method of claim 6, further comprising the steps of: Upon receiving the paging response (306), a random access-based SDT (RA-SDT) is performed with a backoff time for PRACH transmission according to the BPV range.

8. A method for receiving small data transmission (SDT) data by a user equipment UE (101), the method comprising the following steps: Setting (300) the UE (101) to an inactive state (RRC_INACTIVE); receiving (810) a paging notification, the paging notification including a backoff parameter value BPV range; and A backoff time is selected (812) based on the BPV range.

9. A wireless communication system configured to transmit small data transmission (SDT) data from a base station gNB (102) to a user equipment UE (101) according to the method described in any one of claims 1 to 5.

10. A base station gNB (102), configured to transmit small data transmission (SDT) data according to the method described in claim 6 or 7.

11. A user equipment UE (101), configured to receive small data transmission (SDT) data according to the method according to claim 8.

12. A non-transitory computer-readable storage medium having a program stored thereon, which, when executed on a base station gNB (102), instructs the gNB (102) to execute the method according to claim 6 or 7.

13. A non-transitory computer-readable storage medium having a program stored thereon, which, when executed on a user equipment UE (101), instructs the UE (101) to execute the method according to claim 8.

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