Method, device and system for small data transmission in wireless network

Abstract

The present disclosure describes a method and system for various types of small data transmission. The method is performed by a user equipment (UE) in a wireless network, and the method includes: receiving a first message from a wireless communication node in the wireless network, the first message including at least one of the following parameters for configuring a small data transmission (SDT) for a wireless terminal: an SDT scheduling request configuration parameter, a random access channel configuration parameter, a paging parameter, or a discontinuous reception (DRX) parameter; and when the wireless terminal is in an inactive state, initiating an SDT session by sending an SDT initiation message to the wireless communication node on a pre-configured resource allocated by a configuration grant (CG).

Description

[0001] This application is a divisional application. The application number of the original application is 202180087129.9, and the original application date is January 11, 2021. The entire contents of the original application are incorporated into this application by reference. Technical Field

[0002] The present disclosure is generally directed to wireless communications, and more particularly to a method, device, and system for small data transmission. Background Art

[0003] Wireless networks support various types of services that have different requirements for data packet transmission. These requirements include, for example, payload size, transmission delay, transmission reliability, and transmission priority. When the User Equipment (UE) is in inactive mode, it is critical for the UE to reduce power consumption while supporting data transmission with low signaling overhead. Summary of the invention

[0004] The present disclosure is directed to a method, device, and system for various types of small data transmission in wireless communications.

[0005] In an embodiment, a method performed by a wireless terminal in a wireless network is disclosed. The method may include: receiving a first message from a wireless communication node in the wireless network, the first message including at least one of the following parameters for configuring a small data transmission (SDT) for the wireless terminal: an SDT scheduling request configuration parameter, a random access channel configuration parameter, a paging parameter, or a discontinuous reception (DRX) parameter; and initiating an SDT session by sending an SDT initiation message to the wireless communication node on pre-configured resources allocated by a configured grant (CG) when the wireless terminal is in an inactive state.

[0006] In another embodiment, a method performed by a wireless communication node in a wireless network is disclosed. The method may include: receiving a first message from a core network of the wireless network, the first message indicating a paging request for paging a wireless terminal in the wireless network, the wireless terminal being in an SDT session with the wireless communication node; and sending a second message to the wireless terminal.

[0007] In some embodiments, there is a wireless communication device, which includes a processor and a memory, wherein the processor is configured to read code from the memory and implement any method described in any of the multiple embodiments.

[0008] In some embodiments, a computer program product includes a computer readable program medium code stored thereon, which, when executed by a processor, causes the processor to implement any method described in any of the multiple embodiments. The above and other aspects and implementations thereof are described in more detail in the drawings, the specification and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An example wireless communication network is shown.

[0010] Figure 2 An example small data transfer process with error recovery is shown.

[0011] Figure 3 An example multi-step random access procedure is shown. DETAILED DESCRIPTION

[0012] Wireless communication network

[0013] Figure 1 An example cellular wireless communication network 100 (also referred to as a wireless communication system) is shown, which includes a core network 110 and a radio access network (RAN) 120. The RAN 120 also includes a plurality of base stations 122 and 124. The base stations 122 and the user equipment (UE) 130 communicate with each other via Over the Air (OTA) wireless communication resources 140. The wireless communication network 100 can be implemented as, for example, a 2G, 3G, 4G / LTE, or 5G cellular communication network. Accordingly, the base stations 122 and 124 can be implemented as 2G base stations, 3G NodeBs, LTE eNBs, or 5G New Radio (NR) gNBs. The UE 130 can be implemented as a mobile or fixed communication device that is equipped with a SIM / USIM module for accessing the wireless communication network 100. UE 130 may include, but is not limited to, mobile phones, Internet of Things (IoT) devices, Machine-type communication (MTC) devices, laptops, tablets, personal digital assistants, wearable devices, distributed remote sensor devices, roadside assistant equipment, and desktop computers. Instead of the context of a cellular wireless network, RAN 120 and the principles described below may be implemented as other types of wireless access networks, such as Wi-Fi networks, Bluetooth networks, ZigBee networks, and WiMax networks.

[0014] exist Figure 1 In the example wireless communication system 100 of EMBODIMENT 1, UE 130 may connect to base station 122 via OTA interface 140 and establish a communication session with base station 122. The communication session between UE 130 and base station 122 may utilize downlink (DL) transmission resources and / or uplink (UL) transmission resources. DL transmission resources transmit data from base station 122 to UE 130, while UL transmission resources transmit data from UE 130 to base station 122.

[0015] Small data transfer

[0016] In a wireless communication network, a user equipment (UE) can communicate in a small data transmission (SDT) mode. In a conventional implementation, user data is not allowed to be transmitted when in an inactive state. Even for the transmission of a very small amount of data, the UE needs to first switch to a connected state, which may have a negative impact on system efficiency due to relatively large signaling overhead and device energy consumption. As described in the following various implementations, the transmission of a small data payload can be performed in an inactive state of the UE instead. Under the description of the current new air interface (NR) specification, the UE can have three operational states: an idle state, an inactive state, and a connected state. The UE cannot send data in an idle state and an inactive state. When the UE needs to send data when it is in an idle state or an inactive state, the UE will first switch to a connected state. As described in the following various example implementations, for small data transmission (SDT), the UE can be configured to send small data in an inactive state, rather than having to switch to a connected state first.

[0017] Any device with intermittent small data packets for transmission in an inactive state can benefit from the scheme described below for small data transmission (SDT) while in an inactive state. SDT services may have different service requirements compared to traditional or larger data transmission types. SDT communications or data transmissions to and from the UE may be performed when the UE is in an inactive state. The UE may send an SDT request message to a base station, which may be, for example, a Node B (e.g., an eNB or gNB) in a cellular mobile telecommunications context. The base station may respond to the SDT request message with a reply including an SDT indication or confirmation. The SDT indication signal indicates that communication can be performed from the UE even when the UE is in an inactive state. The scheme for small data transmission while in an inactive state helps to reduce power consumption and overall signaling overhead.

[0018] Figure 2 An example small data transfer (SDT) procedure is shown when the UE is in an inactive state. Figure 2 Communication between a UE and a base station (e.g., a gNB) is shown. As an example prerequisite, in step 201, upon receiving a RRCRelease message with SuspendConfig, the UE transitions to an inactive state. As shown in step 202, small data may arrive at the UE in an inactive state, and at 203, the UE triggers the UE to initiate an SDT communication session (alternatively referred to as an SDT session) by sending an SDT request to the base station. At step 204, the base station may confirm the SDT request and the SDT session may then be established. At step 205, the SDT session is considered to be successfully established and the UE is ready for small data transmission. At step 206, the UE requests uplink (UL) resources by sending a scheduling request to the base station. The UL resources are used for subsequent UL data transmission. Based on the payload size, the UE may need to send multiple scheduling requests to obtain multiple UL resources. Alternatively, Figure 2 Not shown, the UL resources may be pre-configured by the base station, for example, rather than requested by the UE. For example, the base station may schedule periodic UL resource allocations for the UE. If the UL resources are pre-configured, the UE will not need to send a scheduling request.

[0019] Various different example mechanisms may be implemented for the UE to send an SDT request to the base station in step 203. The differences between the various mechanisms may include the communication resources used by the UE to send the SDT request to the base station. In one example scenario, when the UE is triggered to enter an inactive state by the RRCRelease message in step 201, the RRCRelease message may carry the pre-configured resources used by the UE to send the SDT request. This scheme is referred to as a configuration grant scheme (hereinafter referred to as a CG-scheme). In another scheme, the UE uses common resources (e.g., random access channel (RACH) resources) instead of pre-configured resources to send the SDT request. This scheme is referred to as a RACH scheme (hereinafter referred to as a RACH-scheme).

[0020] In subsequent small data transmissions, the UE may or may not need to send an SDT scheduling request. In some embodiments, if the SDT session is based on the CG, a scheduling request for subsequent small data transmission may be required. In some embodiments, if the SDT session is based on the RACH, pre-configured resources may be used for small data transmission without a scheduling request.

[0021] Further references Figure 2, the SDT session may encounter failure conditions 207 at various stages of the SDT session. The failure may be caused by poor signal coverage and resource limitations, etc. Therefore, the failure may be of various types. For example, there may be a synchronization failure during the SDT session. Specifically, during the SDT session, the synchronization between the UE and the base station may be lost (i.e., out of synchronization), which may be indicated by the expiration of the Timing Alignment (TA) timer. For another example, there may be a scheduling request failure. This scheduling request failure may affect subsequent small data transmission. For another example, a beam failure may occur. In the presence of any of these failure conditions, the UE may perform an error recovery action 208. In the following disclosure, various embodiments for recovering from the above-mentioned failure conditions are described. For example, in some embodiments, when the UE is in an inactive state, a random access (RA) process may be called as part of an error recovery process. In some other embodiments, a radio resource control (RRC) related process may be called.

[0022] As described above and described in more detail below, various SDT schemes enable the UE to send data in inactive mode. Various embodiments also improve several other aspects of small data transmission, including but not limited to functions such as paging, system information (SI) acquisition, RAN based Notification Area Update (RNAU), and discontinuous reception (DRX).

[0023] CG-Solution: Scheduling Request Parameter Configuration

[0024] As described above, for an SDT session using the CG scheme, a scheduling request (SR) may be required to request UL data transmission resources. The SR is sent based on a specific SR configuration. For example, the SR configuration may be sent from the base station to the UE, for example, by using an RRCRelease message with suspendConfig. Specifically, the UE's medium access control (MAC) entity may be configured with zero SR configurations, one SR configuration, or multiple SR configurations, and each SR configuration corresponds to one or more logical channels.

[0025] The SR configuration may include parameters associated with the dedicated SR resource. These parameters may include at least one of the following:

[0026] An SDT scheduling request identifier, which is used to identify a scheduling request instance corresponding to an SDT session in the MAC layer of the wireless terminal;

[0027] A scheduling request prohibit timer, which is used to prohibit the sending of SDT scheduling requests when the scheduling request prohibit timer is active (not expired);

[0028] The maximum number of consecutive SDT scheduling request transmissions in one SDT scheduling request attempt (SDT scheduling request transmission includes initial transmission and subsequent retransmissions in case of failure of the initial transmission. If the maximum number is reached, SR failure occurs).

[0029] In addition, the SR configuration may also include the following parameters: the parameters are associated with the dedicated SR resources and are also associated with the dedicated physical uplink control channel (PUCCH) resources for the UE to send the SR. These parameters include at least one of the following:

[0030] An SDT scheduling request resource identifier, which is used to identify an SDT scheduling request resource on a dedicated PUCCH resource;

[0031] An SDT scheduling request configuration identifier, the SDT scheduling request configuration identifier being used to identify the first parameter set associated with the second parameter set.

[0032] · SDT schedule request period and offset expressed in number of symbols, slots or mini-slots; or

[0033] A PUCCH resource identifier, which is used to identify a dedicated PUCCH resource.

[0034] In addition, the SR configuration may also include parameters associated with a logical channel, which is configured for the SDT session. These logical channel-related parameters at least include an SDT scheduling request identifier associated with the SDT session.

[0035] Random access process

[0036] As described above, during error recovery of an SDT session, a random access procedure may be used.

[0037] Figure 3Example multi-step random access procedures 300 and 350 are shown. In various embodiments, a UE and a base station may perform a multi-step protocol in which: (i) the UE sends a preamble (e.g., in Msg1) to the base station (302), (ii) after receiving the preamble, the base station sends a random access response (RAR) (e.g., Msg2) back to the UE (304), (iii) the UE sends a third message (e.g., Msg3) to the base station based on the UL grant indicated in the RAR (which is included in the preamble sent in Msg1) (306), and (iv) after successfully decoding Msg3, a fourth message (e.g., Msg4) is sent from the base station to the UE to perform contention resolution (308). This example four-step random access channel (RACH) procedure 300 (alternatively referred to as 4-step RACH) can allow an RRC connection to be established.

[0038] In some embodiments, the latency incurred by the 4-step RACH process 300 can be reduced by using a two-step random access protocol 350 (alternatively referred to as a 2-step RACH). The 2-step RACH 350 can combine (i) and (iii) of the 4-step RACH process and combine (ii) and (iv) of the 4-step RACH process to compress the RACH process into two steps. The first step is to send a first message (e.g., MsgA) (352). In some examples, the first message can include a preamble sent in a physical random access channel and / or a payload sent in a physical uplink shared channel, the payload including at least the same amount of information as the amount of information carried in Msg3 of the 4-step RACH. A second message (e.g., MsgB) (354) in response to MsgA is sent from the base station to the UE. Compared to the 4-step RACH, the example 2-step RACH can help reduce communication latency. This reduction in communication latency can further help, for example, reduce channel occupancy time and increase the data available for payload transmission. Therefore, 2-step RACH provides a technical solution to network latency and other technical issues by improving data network performance and improving the operation of the network's underlying hardware.

[0039] The above 2-step RACH and 4-step RACH may be contention-based. In some other implementations, the base station notifies the UE of a preamble index for random access, thereby generating a non-contention RACH process.

[0040] In some embodiments, the UE may choose to use different RACH resources to initiate a random access procedure for error recovery according to the SDT scheme (i.e., the CG-scheme or the RACH-scheme). Under the CG-scheme, during the error recovery process, the UE may use RACH resources that are in the same bandwidth part (BWP) as the resources used by the UE to initiate the SDT session. In this scheme, RACH resources may be pre-configured via an RRCRelease message. The RACH resource configuration may be combined or separated with the SuspendConfig in the RRCRelease message. Under the RACH-scheme, during the error recovery process, the UE may use a common RACH resource for a random access procedure that may be configured via a system information message.

[0041] CG-Scheme Error Recovery: SR Failed

[0042] During an SDT session, if the transmission of a scheduling request fails at the UE (e.g., no reply is received from the base station), the scheduling request may be retransmitted. SR failure occurs when the number of consecutive scheduling request transmissions exceeds a preconfigured maximum number (e.g., configured in the SR configuration parameters as described above). For error recovery purposes, the UE may initiate a random access procedure or enter an idle state as a number of options.

[0043] Option 1

[0044] During the SDT session, after detecting SR failure, the UE may initiate a contention-based random access procedure using the preconfigured RACH resources as described above. Specifically, the RACH resources may be in the same BWP as the resources used by the UE to initiate the SDT session.

[0045] In some implementations, the random access procedure may be a 4-step RACH or a 2-step RACH.

[0046] In some embodiments, a new MAC control element (CE) is introduced in the error recovery process, and the new MCA CE is alternatively referred to as I-RNTI (Inactive Radio Network Temporary Identifier) ​​MAC CE. The I-RNTI MAC CE is associated with the I-RNTI, which can be used by the network to identify the UE. The I-RNTI MAC CE can also be in two formats: short format and full-size format. The short format I-RNTI MAC CE (also called short I-RNTI MAC CE) is associated with the short I-RNTI (e.g., 24 bits) of the UE's MAC entity, while the full-size format I-RNTI MAC CE (also called full I-RNTI MAC CE) is associated with the full I-RNTI (e.g., 40 bits) of the UE's MAC entity.

[0047] For example, before the UE calls the random access procedure, the MAC entity of the UE can notify the RRC layer of the UE to release the PUCCH resources allocated to the UE for the SDT session. After the UE completes the random access procedure, the base station can reconfigure the PUCCH parameters for the UE through a RRCRelease message or a RRCRecConfiguration message.

[0048] In the above random access procedure invoked by the UE, Msg3 / MsgA may include C-RNTI MAC CE or I-RNTI MAC CE to help the base station or network identify the UE.

[0049] In these embodiments, the random access procedure may be invoked when the UE is in an inactive state.

[0050] Option 2:

[0051] Alternatively, during the SDT session and after detecting the SR failure, the MAC entity of the UE notifies the RRC layer of the UE to release the dedicated resources associated with the SDT session. The UE then transitions to the RRC idle state.

[0052] Option 3:

[0053] Alternatively, during the SDT session and after detecting the SR failure, the MAC entity of the UE notifies the RRC layer of the UE to release the dedicated resources associated with the SDT session. The UE then initiates the RRC reestablishment procedure.

[0054] Option 4:

[0055] Alternatively, during the SDT session and after detecting the SR failure, the MAC entity of the UE notifies the RRC layer of the UE to release the dedicated resources associated with the SDT session. The UE then initiates the RRC recovery procedure.

[0056] The various options or embodiments described above may be combined in various numbers and orders without limitation.

[0057] CG-Scheme Error Recovery: Sync failed

[0058] During an SDT session, it may be necessary to maintain timing alignment between the UE and the base station. During an SDT session, synchronization failure may occur, and such failure may be indicated by the expiration of a Time Alignment (TA) timer.

[0059] In some embodiments, the UE may choose to initiate a contention-based random access procedure immediately after detecting a synchronization failure, or wait until UL data needs to be sent before initiating a contention-based random access procedure. The contention-based random access procedure is similar to the random access procedure described in the above section for CG-scheme SR failure error recovery, and is not repeated here.

[0060] In some embodiments, the base station may command or request the UE to initiate a non-contention random access procedure or a contention-based random access procedure via a PDCCH command when DL data arrives. The PDCCH command may carry the following indication: the random access should be non-contention or contention-based. For example, if the ra-PreambleIndex has been explicitly provided by the PDCCH command, the UE may use a non-contention random access procedure. Otherwise, a contention-based random access procedure may be used.

[0061] The above random access process implementation may be invoked when the UE is in an inactive state.

[0062] CG-Scheme Error Recovery: Beam Failure

[0063] After detecting beam failure during an SDT session, the UE may initiate a non-contention based random access procedure or a contention based random access procedure to recover from the beam failure. The various implementations of the random access procedure are similar to the above.

[0064] In some embodiments, a non-contention based random access procedure may be preferred and may be invoked first, while a contention based random access procedure may be used as a backup solution.

[0065] In these embodiments, the random access procedure may be invoked when the UE is in an inactive state.

[0066] RACH-Scheme Error Recovery: Synchronization Failed

[0067] During an SDT session, it is necessary to maintain timing alignment between the UE and the base station.During an SDT session, synchronization failure may occur, and such failure may be indicated by the expiration of a Time Alignment (TA) timer.

[0068] The UE may initiate a random access procedure to obtain uplink synchronization again. The random access procedure is similar to the random access procedure for CG-scheme SR failure error recovery in the above section, except that the UE may use common RACH resources (e.g., RACH resources configured by system information messages) to initiate the random access procedure.

[0069] In these embodiments, the random access procedure may be invoked when the UE is in an inactive state.

[0070] Using SDT Paging

[0071] During the SDT session, communication between the UE and the network has been established. In this regard, when the network needs to send DL data to the UE, it is not necessary to send paging downlink control information (DCI) and paging messages associated with the paging DCI to the UE during the SDT session. Instead, the base station can directly send RRC messages (e.g., RRCesume and RRCSetup, etc.) to transition the UE to a connected state. Compared with the paging method, this implementation reduces signaling overhead, reduces latency, or may have other technical advantages.

[0072] In some cases, the UE may have just sent an SDT request to initiate an SDT session to the base station, but has not yet received an acknowledgment from the base station. Before the SDT session is successfully established (e.g., after receiving the acknowledgment), if the UE receives a paging DCI (for a paging message) and an associated paging message from the base station, the UE may stop the SDT process and initiate an RRC recovery process.

[0073] During an SDT session, in order to receive system information modification, the UE may need to receive another type of paging DCI to obtain a system information modification indication. It should be understood that the other type of paging DCI is for system information modification and is different from the paging DCI used for paging messages described above. In this regard, the UE may be configured with a pagingSearchSpace parameter that the UE uses when in an SDT session.

[0074] For SDT using the CG-scheme, the pagingSearchSpace parameter may be configured via a RRCRelease message with suspendConfig in the same BWP as the resource used by the UE to initiate the SDT session. Specifically, the pagingSearchSpace parameter may be sent with or without suspendConfig in the RRCRelease message.

[0075] For SDT using the RACH-scheme, the pagingSearchSpace parameter can be configured through system information in the common BWP.

[0076] System Information

[0077] System information (SI) provides key information to the UE, such as physical resource information, cell measurement results, and selection / reselection association information, etc. According to the information transmission method, there are two types of SI: broadcast SI and non-broadcast SI.

[0078] During the SDT session, the UE monitors the SI modification indication in its own paging occasion in each DRX cycle. Upon receiving the SI modification indication, the UE invokes the SI acquisition procedure from the beginning of the next modification cycle.

[0079] For non-broadcast SI and for UEs that are not in an SDT session, the UE can initiate a random access process to obtain non-broadcast SI. However, if the UE is in an SDT session, the communication between the UE and the network has been established. In this regard, the UE can send an RRC message (e.g., a DedicatedSIBRequest message) requesting non-broadcast SI. The base station can respond with an RRCReconfiguration message carrying the requested non-broadcast SI. Alternatively, the base station can transmit the requested non-broadcast SI in a broadcast manner (e.g., via an SI message). This implementation reduces additional process and signaling overhead, thereby improving system performance and reducing UE power consumption.

[0080] DRX

[0081] The UE may use DRX technology to reduce power consumption. When the UE is in an inactive state, the UE may monitor a paging occasion (PO) in each DRX cycle. If the DRX cycle of the UE is configured by the RRC or upper layers and the default DRX value broadcast in the SI, the DRX cycle of the UE may be determined by the shortest of one or more UE-specific DRX values.

[0082] In some embodiments, when the UE is in an SDT session, the UE may be configured with new DRX parameters specific to the UE. For example, these new DRX parameters may be used to support UE PDCCH activity monitoring for C-RNTI and CS-RNTI (configured scheduling RNTI), etc. These new DRX parameters may be configured via an RRCRelease message.

[0083] In some embodiments, an SDT-specific search space value may be configured. Specifically, the UE may be configured with a search space value (e.g., a search space period parameter) that is longer than a predefined value, and the predefined value may be set and modified through an OAM (Operations, Administration and Maintenance) platform. For example, the search space value may be set to be equal to or greater than 2 milliseconds. The longer SDT-specific search space value disclosed herein helps the UE save energy during an SDT session.

[0084] RAN Notification Area Update

[0085] At least for the reason that the RAN needs information about how to page the UE, an inactive UE may be tracked by the RAN. The UE may report its location-related information by sending periodic RAN Notification Area (RNA) updates to the base station, and this may be triggered by the T380 timer. During the SDT session, communication between the UE and the network has been established. The following various embodiments help reduce the overhead of periodic RNA updates.

[0086] In the inactive state, once the SDT session is initiated, the UE can stop the T380 timer. Once the SDT session is ended, the UE can start the T380 timer again.

[0087] In addition, the UE may move during an SDT session, and it may move to another serving cell, and the new serving cell may not belong to the configured RAN notification area of ​​the UE. Furthermore, the new serving cell may or may not support SDT. In this regard:

[0088] If the new serving cell does not support SDT, the UE may terminate the SDT procedure and initiate an RRC connection recovery procedure with resumeCause set to rna-Update;

[0089] If the new serving cell supports SDT, the UE may initiate a new SDT session by sending an SDT request to the base station, where the SDT request includes an rna-Update indication.

[0090] Data arrival for non-SDT data radio bearers

[0091] The UE can use, for example, MCG (Master Cell Group) and SCG (Secondary Cell Group) to configure Multi-Radio Dual Connectivity (MR-DC). Depending on whether logical channels are configured in the MCG, there may be the following two types of data radio bearers (DRBs), which are configured not to be used for SDT (called non-SDT DRBs):

[0092] Non-SDT DRB with MCG path,

[0093] • Non-SDT DRBs without MCG paths.

[0094] For non-SDT DRBs with MCG path, a buffer status report (BSR) can be used during the SDT session to notify the network that UL data has arrived on the UE side. However, for non-SDT DRBs without MCG path, since there is no logical channel for DRBs in MCG, the buffer status of such DRBs will not be included in the BSR.

[0095] To detect UL data arrival of non-SDT DRBs without MCG path during an SDT session, the following two options may be used:

[0096] Option 1:

[0097] It is up to the network to ensure that no non-SDT DRBs without an MCG path are configured for an SDT-enabled UE in inactive mode.

[0098] Option 2:

[0099] In case of UL data arrival of non-SDT DRBs without MCG path, the UE sends at least one of the following information to notify the network to trigger state switching:

[0100] BSR with special value;

[0101] A new type of MAC CE; or

[0102] New RRC messages.

[0103] Suppression of Packet Data Convergence Protocol (PDCP) status reports system

[0104] When the upper layer of the UE requests the PDCP entity to re-establish, the receiving PDCP entity of the UE may trigger a PDCP status report.

[0105] For PDCP entity reestablishment triggered by initialization of SDT or by RRC recovery procedure, the PDCP suspend procedure may be invoked to reset the RX_NEXT and RX_DELIV state variables to their initial values. In this regard, the PDCP status report triggered in this case may not provide any useful information to the network side.

[0106] NOTE: RX_NEXT is a state variable indicating the COUNT value of the next PDCP SDU (service data unit) expected to be received, and RX_DELIV is a state variable indicating the COUNT value of the first PDCP SDU that has not been delivered to the upper layer but is still waiting.

[0107] Therefore, in order to avoid wasting resources, the following two options can be used:

[0108] Option 1:

[0109] For a suspended PDCP, PDCP entity re-establishment does not need to trigger a PDCP status report (ie, if the PDCP is suspended before re-establishment, no PDCP status report is triggered).

[0110] Option 2:

[0111] For a suspended PDCP, the UE may discard the PDCP status report triggered by the re-establishment of the PDCP entity.

[0112] RRC reconfiguration failed

[0113] During an SDT session, the UE may receive an RRC reconfiguration message. When an RRC connection reconfiguration fails during an SDT session, the UE may use two options to handle the failure:

[0114] Option 1:

[0115] When RRC connection reconfiguration fails during an SDT session, the UE may release dedicated resources associated with the SDT session and enter an idle state.

[0116] Option 2:

[0117] When RRC connection reconfiguration fails during an SDT session, the UE may release dedicated resources associated with the SDT session and then initiate an RRC reestablishment procedure.

[0118] Integrity check failed

[0119] During an SDT session, the UE may configure its lower layer (e.g., PDCP layer) to apply signaling radio bearer (SRB) integrity protection. During an SDT session, if an integrity check failure indication on an SRB is received from the lower layer of the UE, the UE has the following two options:

[0120] Option 1:

[0121] According to the integrity check failure indication about SRB from the bottom layer during the SDT session, the UE can release the dedicated resources related to the SDT session and enter the idle state.

[0122] Option 2:

[0123] According to the integrity check failure indication on SRB from the lower layer during the SDT session, the UE can release the dedicated resources related to the SDT session and initiate the RRC re-establishment process.

[0124] The above description and accompanying drawings provide specific example embodiments and implementations. However, the described subject matter may be embodied in a variety of different forms, and therefore the subject matter covered or claimed is intended to be interpreted as not being limited to any example embodiment set forth herein. A reasonably broad scope of the subject matter claimed or covered is desired. In addition, for example, the subject matter may be embodied as a method, device, component, system, or non-transitory computer-readable medium for storing computer code. Therefore, the embodiments may, for example, take the form of hardware, software, firmware, storage media, or any combination thereof. For example, the above method embodiments may be implemented by a component, device, or system including a memory and a processor by executing a computer code stored in the memory.

[0125] Throughout the specification and claims, terms may have slightly different meanings that are suggested or implied by the context, beyond the explicitly stated meanings. Similarly, the phrase "in one embodiment / implementation" as used herein does not necessarily refer to the same embodiment, and the phrase "in another embodiment / implementation" as used herein does not necessarily refer to a different embodiment. For example, it is intended that the claimed subject matter includes all or a combination of some of the example embodiments.

[0126] In general, terms can be understood at least in part according to the usage in the context. For example, terms such as "and", "or", or "and / or" used in this article can include various meanings, which can depend at least in part on the context in which these terms are used. Typically, "or" is intended to represent A, B and C (here for inclusion meanings), and A, B or C (here for exclusive meanings) if used to associate lists such as A, B or C. In addition, the term "one or more" as used herein can be used to describe any feature, structure or characteristic in the singular sense, or can be used to describe a combination of features, structures or features in the plural sense, depending at least in part on the context. Similarly, terms such as "one", "an" or "the" can be understood to convey singular usage or convey plural usage, depending at least in part on the context. In addition, the term "based on" can be understood to not necessarily be intended to convey a set of exclusive factors, and alternatively can allow the presence of additional factors that are not necessarily explicitly described, depending at least in part on the context.

[0127] References to features, advantages, or similar language throughout the specification do not imply that all features and advantages that may be realized with the present solution should be, or be included in, any single embodiment thereof. Rather, language referring to features and advantages is understood to mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present solution. Thus, discussion of features and advantages and similar language throughout the specification may, but does not necessarily, refer to the same embodiment.

[0128] In addition, the described features, structures or characteristics of the present solution may be combined in any suitable manner into one or more embodiments. A person of ordinary skill in the relevant art will recognize from the description herein that the present solution may be practiced without one or more specific features or advantages of a particular embodiment. In other examples, it may be recognized in certain embodiments that additional features and advantages may not be present in all embodiments of the present solution.

Claims

1. A method performed by a wireless terminal in a wireless network, comprising: receiving a first message from a wireless communication node in the wireless network, the first message comprising a random access channel configuration parameter; as well as When the wireless terminal is in an inactive state, initiating an SDT session by sending a small data transmission SDT initiation message to the wireless communication node on a pre-configured resource allocated by a configuration grant CG; wherein, when the wireless terminal is in the SDT session, the wireless terminal is configured with a discontinuous reception DRX parameter, and the DRX parameter is used to monitor the PDCCH activity of the C-RNTI or CS-RNTI of the wireless terminal; detecting an SDT session failure condition associated with the SDT session; wherein the SDT session failure condition comprises a timing alignment failure with the wireless communication node; and In response to the SDT session failure, a random access procedure RAP is initiated.

2. The method according to claim 1, wherein: The first message further comprises a random access channel RACH configuration, the RACH configuration indicating a random access channel resource, the RACH configuration being on the same bandwidth part BWP of the pre-configured resources allocated by a configuration grant.

3. The method according to claim 1, wherein: The random access procedure includes a contention-based random access procedure.

4. The method according to claim 3, wherein: The random access process includes Msg3 or MsgA; The Msg3 includes a cell radio network temporary identifier MAC control element C-RNTI MAC CE; and The MsgA includes C-RNTI MAC CE.

5. The method according to claim 1, further comprising: Detect SDT session failures; as well as In response to the SDT session failure condition: The MAC entity of the wireless terminal notifies the radio resource control RRC layer of the wireless terminal to release resources dedicated to the SDT session; and Transition to the idle state.

6. A method performed by a wireless terminal in a wireless network, comprising: When the wireless terminal is in an inactive state, sending a small data transmission SDT initiation message to a wireless communication node in the wireless network on a RACH resource based on a random access process to initiate an SDT session; wherein, when the wireless terminal is in the SDT session, the wireless terminal is configured with a discontinuous reception DRX parameter, and the DRX parameter is used to monitor the PDCCH activity of the C-RNTI or CS-RNTI of the wireless terminal; detecting an SDT session failure condition associated with the SDT session; wherein the SDT session failure condition comprises a timing alignment failure with the wireless communication node; and In response to the SDT session failure, a random access procedure RAP is initiated.

7. The method according to claim 6, wherein: The random access procedure includes a contention-based random access procedure.

8. The method according to claim 7, wherein: The random access process includes Msg3 or MsgA; The Msg3 includes a cell radio network temporary identifier MAC control element C-RNTI MAC CE; and The MsgA includes C-RNTI MAC CE.

9. A wireless terminal comprising a memory for storing computer instructions and a processor in communication with the memory, wherein: The processor executes the computer instructions, and the processor is configured to cause the wireless terminal to execute: receiving a first message from a wireless communication node, the first message comprising a random access channel configuration parameter; and When the wireless terminal is in an inactive state, initiating an SDT session by sending a small data transmission SDT initiation message to the wireless communication node on a pre-configured resource allocated by a configuration grant CG; wherein, when the wireless terminal is in the SDT session, the wireless terminal is configured with a discontinuous reception DRX parameter, and the DRX parameter is used to monitor the PDCCH activity of the C-RNTI or CS-RNTI of the wireless terminal; detecting an SDT session failure condition associated with the SDT session; wherein the SDT session failure condition comprises a timing alignment failure with the wireless communication node; and In response to the SDT session failure, a random access procedure RAP is initiated.

10. The wireless terminal according to claim 9, wherein: The first message further comprises a random access channel RACH configuration, the RACH configuration indicating a random access channel resource, the RACH configuration being on the same bandwidth part BWP of the pre-configured resources allocated by a configuration grant.

11. The wireless terminal according to claim 9, wherein: The random access procedure includes a contention-based random access procedure.

12. The wireless terminal according to claim 11, wherein: The random access process includes Msg3 or MsgA; The Msg3 includes a cell radio network temporary identifier MAC control element C-RNTI MAC CE; and The MsgA includes C-RNTI MAC CE.

13. The wireless terminal according to claim 9, wherein: The processor executes the computer instructions, and the processor is configured to cause the wireless terminal to execute: Detecting SDT session failures; and In response to the SDT session failure condition: The MAC entity of the wireless terminal notifies the radio resource control RRC layer of the wireless terminal to release resources dedicated to the SDT session; and Transition to the idle state.

14. A wireless terminal comprising a memory for storing computer instructions and a processor in communication with the memory, wherein: The processor is configured to implement the method of claim 6 when executing the computer instructions.

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