Small data transmission process rollback to random access process

Abstract

Example embodiments of methods and devices supporting fallback from a small data transfer (SDT) process to a random access (RA) process are disclosed. A method may include: initiating a small data transfer (SDT) process for transmitting uplink data to a network device; determining whether a condition is satisfied; and when the condition is satisfied, switching from the SDT process to another process for the uplink data transmission. The other process may be a random access (RA) process different from the SDT process.

Description

Technical Field

[0001] Various example embodiments described herein relate generally to communication technology, and more particularly, to methods and apparatuses for supporting small data transfer (SDT) procedure to random access (RA) procedure fallback. Background Art

[0002] 5G NR supports the RRC_INACTIVE state, in which the UE can send small and infrequent (periodic and / or aperiodic) uplink data to the network. No matter how small and infrequent the data packets are, the UE does not need to transition to the RRC_CONNECTED state for every data transmission. Summary of the invention

[0003] A brief summary of example embodiments is provided below to provide a basic understanding of some aspects of various example embodiments. It should be noted that this summary is not intended to identify key features of essential elements or define the scope of example embodiments, and its sole purpose is to introduce some concepts in a simplified form as a prelude to the more detailed description provided below.

[0004] In a first aspect, an example embodiment of a user equipment (UE) is provided. The UE may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, cause the UE to perform one or more actions. The one or more actions may include: initiating a small data transfer (SDT) process for transmitting uplink data to a network device; determining whether a condition is satisfied; and when the condition is satisfied, switching from the SDT process to another process for the uplink data transmission.

[0005] In a second aspect, an example embodiment of a network device is provided. The network device may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, cause the network device to perform one or more actions. The one or more actions may include receiving a message from a user equipment (UE), the message including an indication of a transition from a small data transfer (SDT) process to another process.

[0006] In a third aspect, an example embodiment of a network device is provided. The network device may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, cause the network device to perform one or more actions. The one or more actions may include receiving a message from a user equipment (UE), the message including a payload on a first uplink (UL) grant in a random access (RA) procedure, the payload including a first part of a transport block (TB) for a small data transfer (SDT) procedure different from the RA procedure.

[0007] In a fourth aspect, an example embodiment of a method implemented at a user equipment (UE) is provided. The method may include: initiating a small data transmission (SDT) procedure for transmitting uplink data to a network device; determining whether a condition is satisfied; and when the condition is satisfied, switching from the SDT procedure to another procedure for the uplink data transmission.

[0008] In a fifth aspect, an example embodiment of a method implemented at a network device is provided. The method may include receiving a message from a user equipment (UE), the message including an indication to transition from a small data transfer (SDT) procedure to another procedure.

[0009] In a sixth aspect, an example embodiment of a method implemented at a network device is provided. The method may include receiving a message from a user equipment (UE), the message including a payload on a first uplink (UL) grant in a random access (RA) procedure, the payload including a first portion of a transport block (TB) for a small data transfer (SDT) procedure different from the RA procedure.

[0010] In a seventh aspect, an example embodiment of a computer program is provided. The computer program may include instructions stored on a computer-readable medium. The instructions may, when executed by at least one processor of a user equipment (UE), cause the UE to perform one or more actions. The one or more actions may include: initiating a small data transfer (SDT) process for transmitting uplink data to a network device; determining whether a condition is satisfied; and when the condition is satisfied, switching from the SDT process to another process for the uplink data transmission.

[0011] In an eighth aspect, an example embodiment of a computer program is provided. The computer program may include instructions stored on a computer-readable medium. The instructions may, when executed by at least one processor of a network device, cause the network device to perform one or more actions. The one or more actions may include receiving a message from a user equipment (UE), the message including an indication of transitioning from a small data transfer (SDT) process to another process.

[0012] In a ninth aspect, an example embodiment of a computer program is provided. The computer program may include instructions stored on a computer-readable medium. The instructions, when executed by at least one processor of a network device, may cause the network device to perform one or more actions. The one or more actions may include receiving a message from a user equipment (UE), the message including a payload on a first uplink (UL) grant in a random access (RA) procedure, the payload including a first part (TB) of a transport block for a small data transfer (SDT) procedure different from the RA procedure.

[0013] In a tenth aspect, an example embodiment of an apparatus is provided. The apparatus may include: means for initiating a small data transfer (SDT) procedure for transmitting uplink data to a network device; means for determining whether a condition is satisfied; and means for switching from the SDT procedure to another procedure for transmitting the uplink data when the condition is satisfied.

[0014] In an eleventh aspect, an example embodiment of an apparatus is provided. The apparatus may include means for receiving a message from a user equipment (UE), the message including an indication of transitioning from a small data transfer (SDT) procedure to another procedure.

[0015] In a twelfth aspect, an example embodiment of an apparatus is provided. The apparatus may include: means for receiving a message from a user equipment (UE), the message including a payload on a first uplink (UL) grant in a random access (RA) procedure, the payload including a first portion of a transport block (TB) for a small data transfer (SDT) procedure, the RA procedure being different from the SDT procedure.

[0016] Other features and advantages of the exemplary embodiments of the present application will also be apparent when the following description of the specific exemplary embodiments is read in conjunction with the accompanying drawings, which illustrate the principles of the exemplary embodiments of the present application by way of example. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Some example embodiments will now be described, by way of non-limiting examples, with reference to the accompanying drawings.

[0018] Figure 1is a schematic diagram illustrating an example communication network.

[0019] Figure 2 is a signaling diagram illustrating a four-step random access (RA) procedure.

[0020] Figure 3 is a signaling diagram illustrating a two-step RA process.

[0021] Figure 4 is a signaling diagram illustrating a Small Data Transfer (SDT) procedure that falls back to another procedure according to some example embodiments.

[0022] Figure 5 is a signaling diagram illustrating operations in the case of SDT to RA fallback according to some example embodiments.

[0023] Figure 6 is a signaling diagram illustrating operations in the case of SDT to RA fallback according to some example embodiments.

[0024] Figure 7 is a flow chart illustrating a method implemented at a terminal device according to some example embodiments.

[0025] Figure 8 is a flow chart illustrating a method implemented at a network device according to some example embodiments.

[0026] Fig. 9 is a flow chart illustrating a method implemented at a network device according to some example embodiments.

[0027] Fig.10 is a block diagram illustrating an example communication system in which example embodiments of the present application may be implemented.

[0028] In all drawings, the same or similar reference numerals indicate the same or similar elements, and repeated description of the same elements will be omitted. DETAILED DESCRIPTION

[0029] Hereinafter, some example embodiments will be described in detail with reference to the accompanying drawings. In order to provide a thorough understanding of various concepts, the following description includes specific details. However, it is apparent to those skilled in the art that these concepts can be practiced without these specific details. In some instances, well-known circuits, techniques, and components are shown in block diagram form to avoid obfuscation of the concepts and features described.

[0030] As used herein, the term "network equipment" refers to any suitable entity or device that can provide a cell or coverage, through which a terminal device can access a network or receive a service. Network equipment may generally be referred to as a base station. The term "base station" used herein may represent a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), or a gNB. A base station may be implemented as a macro base station, a relay node, or a low-power node such as a micro base station or a femto base station. A base station may be composed of several distributed network units, such as a central unit (CU), one or more distributed units (DU), one or more remote radio heads (RRH), or a remote radio unit (RRU). The number and functionality of these distributed units depends on the selected split RAN architecture.

[0031] As used herein, the term "terminal device" or "user equipment" (UE) refers to any entity or device that can communicate wirelessly with network devices or each other. Examples of terminal devices may include mobile phones, mobile terminals (MTs), mobile stations (MSs), subscriber stations (SSs), portable subscriber stations (PSSs), access terminals (ATs), computers, wearable devices, vehicle-mounted communication devices, machine type communication (MTC) devices, D2D communication devices, V2X communication devices, sensors, etc. The term "terminal device" may be used interchangeably with UE, user terminal, mobile terminal, mobile station, or wireless device.

[0032] Figure 1 A schematic diagram of an example communication network 100 is illustrated. Figure 1 , a communication network 100 may include a user equipment (UE) 110 and a base station (BS) such as a gNB 120. The BS 120 may serve a cell, and the UE 110 may camp on the cell. When the UE 110 has only small and infrequent data transmissions, the BS 120 may maintain the UE 110 in an RRC_INACTIVE state, in which the UE 110 may send small data through a two-step or four-step random access channel (RACH) procedure or on a pre-configured uplink grant. When performing a small data transmission (SDT) through the RACH procedure, the UE 110 may send an SDT transport block (TB) to the BS 120 in a first message (MsgA) for the two-step RACH procedure or in a third message (Msg3) for the four-step RACH procedure.

[0033] The channel quality of UE 110 may vary in the cell. For example, when UE 110 moves from the central area of ​​the cell to the edge area, or when the beam for UE 110 is at least partially blocked by a building or a moving object, the reference signal received power (RSRP) and signal to interference plus noise ratio (SINR) measured at UE 110 may deteriorate. The deteriorated channel quality may not meet the requirements of SDT transmission. If UE 110 has triggered the SDT process and RSRP drops below a threshold, the SDT process may not be able to send a transport block (TB) to BS 120, causing UE 110 to enter the RRC_IDLE state. Compared with the RRC_INACTIVE state, it will take more time for UE 110 to establish an RRC connection with BS 120 from the RRC_IDLE state. In addition, UE 110 will lose the TB generated during the SDT process.

[0034] Hereinafter, an exemplary embodiment of a method and apparatus for supporting SDT to RA process fallback will be discussed in detail with reference to the accompanying drawings. In an exemplary embodiment, when a specific condition is met, the UE can switch from the SDT process to another process, such as a RA process different from the SDT process. The transport block (TB) generated in the SDT process can be sent to the network by means of the RA process, thereby increasing the probability that uplink data is successfully sent to the network.

[0035] Figure 2 is a signaling diagram illustrating a four-step random access (RA) procedure. Figure 2 As shown, in step 1, UE 110 may send a first message (Msg1) including a preamble to BS 120 on a physical random access channel (PRACH). The preamble may be selected from a preamble group such as preamble group A or preamble group B. In step 2, BS 120 may respond to UE 110 with a random access response (RAR) message (Msg2). The Msg2 message may include a timing advance (TA) and an uplink (UL) grant on a physical downlink shared channel (PDSCH). In response to Msg2, UE 110 sends a third message (Msg3) to BS 120 using the UL grant in step 3. The Msg3 message may include an RRC connection request on a physical uplink shared channel (PUSCH). Then, BS 120 responds with a fourth message (Msg4) in step 4, and the fourth message (Msg4) may include contention resolution on the PDSCH channel. It should be understood that the Msg2 message and the Msg4 message may also include a Physical Downlink Control Channel (PDCCH) communication that carries control information for decoding the PDSCH communication.

[0036] Figure 3 The two-step RA process is shown in the figure, with Figure 2Compared with the four-step process shown in Figure 1, it can speed up access to the network. Figure 3 In step A, UE 110 may send a first message (MsgA) combining Msg1 and Msg3 in the four-step process to BS 120. That is, MsgA may include a preamble and an RRC message on a PRACH channel, such as an RRC connection or resumption request on a PUSCH channel. For non-RRC-based SDT, MsgA may not include an RRC message, but may include, for example, uplink data. The RRC connection request may be sent using a preconfigured uplink grant. In response to MsgA, BS 120 may send a second message (MsgB) combining Msg2 and Msg4 in the four-step process to UE 110 in step B. That is, MsgB may include a random access response (RAR) and contention resolution on a PDSCH channel. Figure 2 Compared with the four-step process shown in FIG. 1 , the two-step process can reduce the time length of the entire random access process.

[0037] Figure 4 is a signaling diagram illustrating an SDT process to another process fallback process according to some example embodiments. Figure 4 At operation 210, the UE 110, which may remain in the RRC_INACTIVE state, may initiate an SDT procedure to transmit uplink data to the BS 120. In the SDT procedure, the UE 110 may package the uplink data into a transport block (TB) and attempt to transmit the TB to the BS 120. The SDT procedure may be performed by Figure 3 The two-step RA process shown or Figure 2 The RA procedure may be performed using the four-step RA procedure shown in FIG. 1 or a pre-configured UL grant. In the four-step RA procedure, the SDT uplink data may be sent to the network in a Msg3 message. In the two-step RA procedure, the SDT uplink data may be sent to the network in a MsgA message.

[0038] At operation 220, UE 110 may determine whether the conditions for the SDT process to fall back to another process are met. If the conditions are not met, UE 110 may continue to perform the SDT process to send the SDT TB to BS 120. When the SDT attempt fails, UE 110 may remain in an inactive state. Additionally or alternatively, when a predetermined number of SDT attempts fail, UE 110 may enter an idle state. If the conditions are met and the SDT process has not successfully sent uplink data to BS 120, UE 110 may fall back from the SDT process to another process at operation 230 to send uplink data to BS 120. The other process may be a random access (RA) process different from the SDT process. In other words, the RACH resources and / or preambles configured for UE 110 in the RA process after the fallback are different from the resources and / or preambles configured in the SDT process before the fallback. For example, UE 110 may fall back to a normal RA process from an SDT process performed through an RA process or on a preconfigured UL grant. The normal RA procedure differs from the SDT RA procedure in that the SDT RA procedure sends uplink data in MsgA or Msg3, whereas the normal RA procedure does not send uplink data to the network in MsgA or Msg3. In another example, the normal RA procedure differs from the SDT RA procedure in that the SDT RA procedure can send more uplink data in MsgA or Msg3 than the normal RA procedure. As another example, the UE 110 may fall back to the SDT RA procedure from the SDT procedure performed on the preconfigured UL grant, or fall back to the four-step SDT RA procedure from the SDT procedure performed through the two-step RA procedure. The UE 110 may transition to the four-step SDT RA procedure by sending a MsgA message to the BS 120. Figure 3 The two-step (normal or SDT) RA process shown in FIG. 1 may be switched to the RA process by sending a Msg1 message to BS 120. Figure 2 The four-step (normal or SDT) RA process is shown.

[0039] In some example embodiments, UE 110 may determine whether a reference signal received power (RSRP) measured at UE 110 is below a first threshold for performing an SDT procedure in operation 220. For example, when UE 110 initiates the SDT procedure in operation 210, the RSRP measured at UE 110 may be equal to or greater than the first threshold. If the RSRP measured at a subsequent measurement opportunity drops below the first threshold, UE 110 may decide to fall back from the SDT procedure to the RA procedure.

[0040] In some example embodiments, UE 110 may determine in operation 220 whether the RSRP measured at UE 110 is below a first threshold to perform an SDT process by an amount equal to or greater than a predetermined offset. For example, when UE 110 initiates the SDT process in operation 210, the RSRP measured at UE 110 is equal to or greater than the first threshold. If the RSRP measured at a subsequent measurement opportunity drops below the first threshold but the difference therebetween is less than the predefined offset, UE 110 may still perform the SDT process. When the RSRP measured at UE 110 is below the first threshold by an amount equal to or greater than the predefined offset, UE 110 may decide to fall back from the SDT process to the RA process. By using the offset between the threshold for performing the SDT process and the threshold for switching from the SDT process to the RA process, UE 110 may avoid frequent switching between the SDT process and the RA process.

[0041] In some example embodiments, UE 110 may determine whether it has attempted to send an SDT TB multiple times in the SDT procedure in operation 220. If the number of SDT attempts reaches a second threshold, UE 110 may decide to fall back from the SDT procedure to the RA procedure.

[0042] In some example embodiments, UE 110 may determine whether RSRP measured at UE 110 is below a first threshold for a second threshold number of SDT attempts in operation 220. If so, UE 110 may decide to fall back from the SDT procedure to the RA procedure.

[0043] In some example embodiments, UE 110 may determine whether the timing alignment of UE 110 has become invalid in operation 220. For example, if the timing alignment timer expires while performing the SDT procedure on a preconfigured UL grant, the low mobility criterion is not met, or the RSRP measured at UE 110 differs from a reference value or range by more than a threshold, UE 110 may determine that the timing alignment has become invalid and decide to fall back from the SDT procedure to the RA procedure.

[0044] In some example embodiments, UE 110 may determine in operation 220 whether resources for SDT transmission (e.g., a beam with SDT resources) become unavailable to UE 110. In some examples, the beam with SDT resources may be a beam for which UE 110 initiates an SDT procedure. For example, the beam with SDT resources may be blocked by a building or a moving object. For example, when the measured RSRP and / or reference signal received quality (RSRQ) and / or SINR is below a configured / predefined threshold level, the beam may become unavailable to UE 110. In this case, UE 110 may decide to fall back from the SDT procedure to the RA procedure.

[0045] It should be understood that the UE 110 may also consider other conditions or a combination of two or more conditions in operation 220 to decide whether it needs to fall back from the SDT process to the RA process.

[0046] Figure 5 is a signaling diagram illustrating operations in the case of SDT to RA fallback according to some example embodiments. Figure 4 Operation 230 in the process is converted from the SDT process to the RA process, then the execution Figure 5 The operation shown.

[0047] refer to Figure 5 At operation 310 in the RA process, UE 110 may send a message including an indication of SDT to RA transition (fallback) to BS 120. Here, the message may be Figure 3 The first message (MsgA) in the two-step RA process shown or Figure 2 The third message (Msg3) in the four-step RA process is shown.

[0048] In some example embodiments, the transition indication may include a buffer status report (BSR) indicating the buffered data in the SDT buffer for the unsuccessful SDT process. For example, when UE 110 decides to fall back from the SDT process to the RA process, it may introduce a BSR trigger. In response to the BSR trigger, the BSR report may be multiplexed into a MsgA or Msg3 message in the RA process. When BS 120 receives the BSR report, it will know that the RA process originated from the SDT to RA process fallback, and BS 120 will further know the size of the data in the SDT buffer that UE 110 needs to send to BS 120.

[0049] In some example embodiments, the transition indication may include a newly introduced medium access control (MAC) control element (CE) and / or a MAC subheader. The MAC subheader may include a specific logical channel identifier (LCID) to identify the transition from the SDT to the RA procedure. In some examples, a MAC subheader with a specific LCID may not have a corresponding MAC CE or MAC service data unit (SDU) in a MAC sub-PDU. When BS 120 knows from the MAC CE and / or the MAC subheader that the RA procedure originates from the SDT to RA fallback, it can estimate the data size that UE 110 needs to send to BS 120, i.e., the data size of the SDT TB.

[0050] In some example embodiments, the MAC CE and / or the MAC subheader may indicate the preamble group used in the SDT process. If the SDT process is performed via a two-step or four-step RACH process, then typically preamble group A is used to send a relatively small amount of data, and preamble group B is used to send a relatively large amount of data. Then, from the preamble group used in the SDT process, BS 120 may infer the amount of data that UE 110 needs to send to BS 120.

[0051] In some example embodiments, the MAC CE and / or MAC subheader may indicate a resource index, such as a transport block size (TBS) index used to construct TBs for SDT transmission. From the TBS index, BS 120 may infer the amount of data that UE 110 needs to send to BS 120.

[0052] In some example embodiments, the transition indication may include a common control channel (CCCH) SDU from the SDT transmission. From the CCCH SDU for the SDT transmission, BS 120 may infer the SDT to RA fallback and, in turn, the amount of data that UE 110 needs to send to BS 120.

[0053] When BS 120 knows the SDT to RA fallback from the transition indication, BS 120 may allocate a UL grant that can accommodate the SDT TB to UE 110. Then the SDT TB that UE 110 failed to send to BS 120 during the SDT process may be sent on the allocated UL grant. UE 110 may store the SDT TB in the MAC buffer, and it does not need to rebuild the SDT TB because the allocated UL grant can accommodate the SDT TB.

[0054] In some example embodiments, the message may also include a random number as an identifier (ID) of UE 110 in the fallback RA procedure. The random number may be generated by UE 110 and included in a MAC CE having a size equal to the C-RNTI MAC CE (e.g., 16 bits). The random number MAC CE may have a special LCID to avoid being mistaken for a C-RNTI MAC CE. For example, the special LCID of the random number MAC CE may be a transition indication LCID as described above.

[0055] In some example embodiments, the message may instead include a CCCH SDU from the SDT transmission to identify UE 110. Similar to the random number MAC CE, the CCCH SDU may have a special LCID.

[0056] In response to the message (MsgA or Msg3) received in operation 310, BS 120 may transmit a message including contention resolution to UE 110 in operation 320. The message transmitted in operation 320 may be Figure 3 The second message (MsgB) in the two-step RA process shown in FIG. Figure 2 The fourth message (Msg4) in the four-step RA process is shown. If the message received in operation 310 includes a UE ID represented by a random number or a CCCH SDU from an SDT transmission, the contention resolution SDT transmission included in the message sent in operation 320 can be generated based on the random number or the CCCH SDU from the SDT transmission.

[0057] In some example embodiments, when the RA procedure is successfully implemented, BS 120 may move UE 110 to an RRC_CONNECTED state, and an RRC connection may be established between UE 110 and BS 120. In some example embodiments, BS 120 may still maintain UE 110 in an RRC_INACTIVE state because BS 120 knows that the RA procedure originates from an SDT to RA fallback. Then in operation 330, BS 120 may allocate an UL grant to UE 110 on a physical downlink control channel (PDCCH). Since BS 120 knows the size of data that UE 110 needs to send, it will allocate a UL grant large enough to UE 110 to accommodate the data size of, for example, an SDT TB. In response to the allocated UL grant, in operation 340, UE 110 will send an SDT TB to BS 120 on the UL grant. In an exemplary embodiment, the SDT TB that UE 110 fails to transmit to BS 120 in the SDT procedure will be transmitted to BS 120 by means of the RA procedure, and UE 110 does not need to re-establish the SDT TB.

[0058] Figure 6 is a signaling diagram illustrating operations in the case of SDT to RA fallback according to some example embodiments. Figure 4 Operation 230 in the process is converted from the SDT process to the RA process, then the execution Figure 6 The operation shown. Figure 6 In the illustrated process, the SDT TB that the UE 110 fails to transmit to the BS 120 may be re-established and transmitted to the BS 120 by means of the RA process.

[0059] Reference Figure 6 At operation 410 in the RA process, UE 110 may send a message including the first part of the SDT TB to BS 120. The message sent in operation 410 may be Figure 3The first message (MsgA) in the two-step RA process shown or Figure 2 The third message (Msg3) in the four-step RA process shown. The first part of the SDT TB can be sent on the first UL grant in the RA process. If the message sent in operation 410 is the first message (MsgA) in the two-step RA process, the first part of the SDT TB can be sent on the pre-configured UL grant; if the message sent in operation 410 is the third message (Msg3) in the four-step RA process, the first part of the SDT TB can be sent on the UL grant received in the second message (Msg2).

[0060] In some example embodiments, the first part of the SDT TB sent in operation 410 may include a CCCH SDU from the SDT TB. As described above, the CCCH SDU may also indicate that the RA procedure originates from an SDT to RA fallback, or the CCCH SDU may have a special LCID to indicate the SDT to RA fallback. The remaining SDUs and MAC CEs of the SDT TB may be sent on a subsequent UL grant. In some example embodiments, the first part of the SDT TB may include a CCCH SDU and additional SDUs and / or MAC CEs from the SDT TB to the extent that the UL grant for the message is exhausted, and the remaining SDUs and / or MAC CEs of the SDT TB may be sent in a subsequent UL grant.

[0061] In some example embodiments, UE 110 may select a preamble group, and in turn select a preamble from the preamble group for the RA procedure. The preamble may be sent in a MsgA message or a Msg1 message in the RA procedure. When selecting a preamble group, UE 110 may consider the payload of the CCCH SDU from the SDT TB, which enables the selection of sequence group A. If the entire SDT TB is taken into account in the preamble group selection, UE 110 may always select preamble group B due to the relatively large SDT TB.

[0062] In response to the message received in operation 410, BS 120 may transmit a message including contention resolution to UE 110 in operation 420. The message transmitted in operation 420 may be Figure 3 The second message (MsgB) in the two-step RA process shown in FIG. Figure 2 The fourth message (Msg4) in the four-step RA process is shown.

[0063] In some example embodiments, when the RA procedure is successfully implemented, BS 120 may move UE 110 to the RRC_CONNECTED state, and an RRC connection may be established between UE 110 and BS 120. In some example embodiments, BS 120 may still maintain UE 110 in the RRC_INACTIVE state because BS 120 knows from the CCCH SDU that the RA procedure originates from the SDT to RA fallback. Then in operation 430, BS 120 may allocate an UL grant to UE 110 on the PDCCH channel. Since BS 120 knows the size of data that UE 110 needs to send based on the CCCH SDU from the SDT TB, it may allocate an UL grant to UE 110 that can accommodate the remaining portion of the SDT TB. In response to the allocated UL grant, UE 110 will send the remaining portion of the SDT TB to BS 120 on the UL grant in operation 440. In this manner, the SDT TB is reestablished at the UE 110 and sent to the BS 120 over multiple UL grants.

[0064] In the above example embodiments, when certain conditions are met, UE 110 may fall back from the SDT process to the RA process, and may send a first SDT transmission to BS 120 through the RA process. If the RA process is successful, BS 120 may move UE 110 to the RRC_CONNECTED state or maintain UE 110 in the RRC_INACTIVE state. The SDT TB that UE 110 failed to send in the SDT process may then be sent to BS 120 on a subsequent UL grant. The SDT TB may or may not be reestablished at UE 110 for transmission to BS 120.

[0065] Figure 7 is a flow chart illustrating a method 500 according to some example embodiments. The method 500 may be implemented in a system such as Figure 1 The method 500 is implemented at the terminal device of the UE 110 shown in FIG. For example, the steps of the method 500 may be performed by a device, module or element of a device implemented at the UE 110. Some details of the method 500 have been described above with reference to FIG. Figure 2-6 The process shown in FIG. 5 is discussed in detail, and a brief description of method 500 will be given here. For a better understanding, reference can be made to Figure 2-6 The following description of method 500 should be read in light of the above description.

[0066] refer to Figure 7, method 500 may include step 510 of initiating an SDT procedure for transmitting uplink data to a network device such as BS 120. During the SDT procedure, UE 110 may be in an RRC_INACTIVE state, and it may encapsulate uplink data in a transport block (TB) for SDT transmission. When an SDT attempt fails, the UE may stay in the RRC_INACTIVE state and attempt the next SDT attempt. In some example embodiments, if a predetermined number of SDT attempts fail, the UE may enter an RRC_IDLE state.

[0067] Method 500 may also include step 520 of determining whether a condition is satisfied. In some example embodiments, the condition may include one or more of the following conditions:

[0068] A reference signal received power (RSRP) measured at the UE is lower than a first threshold;

[0069] The RSRP measured at the UE is below a first threshold by a predetermined offset;

[0070] The number of SDT attempts reaches the second threshold;

[0071] The RSRP measured at the UE is below the first threshold for a second threshold number of SDT attempts;

[0072] The UE's timing alignment becomes invalid; and

[0073] The beam with SDT resources becomes unavailable to the UE.

[0074] If the conditions are met, then in step 530, the UE may switch from the SDT process to another process, such as a RA process different from the SDT process.

[0075] The RA process may be implemented in various ways. In some example embodiments, the method 500 may include step 540 of sending a message including an indication of an SDT to RA transition to a network device during the RA process. The message may be the first message (MsgA) in a two-step RA process or the third message (Msg3) in a four-step RA process. In some example embodiments, the transition indication may include a buffer status report (BSR) indicating buffered data for SDT transmission. For example, in step 530, when the UE transitions from the SDT process to the RA process, the UE may further introduce a BSR trigger, and in response to the BSR trigger, the BSR report may be multiplexed into the transmitted RA message in step 540.

[0076] In some example embodiments, the transition indication may include a medium access control (MAC) control element (CE) and / or a logical channel identifier (LCID) in a MAC subheader. The MAC CE and / or LCID may indicate, for example, a transition, a preamble group for SDT transmission, or a transport block size (TBS) index for constructing a transport block (TB) including uplink data for SDT transmission.

[0077] In some example embodiments, the transition indication may include a common control channel (CCCH) service data unit (SDU) from an SDT transmission.

[0078] In some example embodiments, the message sent in step 540 may also include a random number generated at the UE or a CCCH SDU from an SDT transmission for identifying the UE. Figure 7 As not shown, the UE may receive a message including a contention resolution in the RA procedure from the network device, and may generate the contention resolution based on a random number or a CCCH SDU from an SDT transmission.

[0079] The method 500 may further include step 560 of receiving a UL grant from the network device after the RA procedure. Since the network device knows from the transition indication that the UE attempts to send uplink data through the SDT procedure, the network device will allocate a UL grant that can accommodate the SDTTB.

[0080] In response to the UL grant received in step 560, the UE may transmit a TB including uplink data generated in the SDT process to the network device on the UL grant in step 580. The SDT TB including the uplink data may be stored in a MAC buffer of the UE.

[0081] In some example embodiments, the RA process may be implemented by sending a message including a payload to the network device on a first uplink (UL) grant in step 550. The payload may include a first portion of a transport block (TB) including uplink data generated in the SDT process. The message may be the first message (MSGA) in a two-step RA process or the third message (Msg3) in a four-step RA process. The first portion of the SDT TB may include at least a CCCH SDU from the TB. The first portion may also include additional MAC SDUs and / or MAC CEs to the extent that the UL grant for the message is exhausted.

[0082] During the RA process, the UE selects a preamble group, then selects a preamble from the preamble group and Figure 2-3The preamble is sent to the network device in the MsgA or Msg1 message shown. In some example embodiments, the UE can select the preamble group for the RA procedure based on the CCCH SDU from the TB. It will be able to select preamble group A because the UE may always select preamble group B if the entire SDT TB is considered.

[0083] Reference Figure 7 The method 500 may further include a step 570 of receiving a UL grant from the network device and a step 590 of sending the remaining portion of the SDT TB on the UL grant. Therefore, the remaining portion of the SDT TB may be sent on one or more subsequent UL grants.

[0084] Figure 8 600 according to some example embodiments. The method 600 may be implemented in a system such as Figure 1 The method 600 is implemented at a network device of the BS 120 shown. For example, the steps of the method 600 may be performed by a device, module or element of a device implemented at the BS 120. Some details of the method 600 have been described above with reference to Figure 2-7 The process shown in FIG. 6 is discussed, and a brief description of method 600 is given here. For a better understanding, reference can be made to Figure 2-7 The following description of method 600 should be read in light of the above description.

[0085] refer to Figure 8 , method 600 may include step 610, receiving a message including a fallback indication from a user equipment (UE) such as UE 110 during a random access (RA) procedure. The fallback indication may indicate a fallback from the SDT procedure to another procedure such as a RA procedure that is different from the SDT procedure. The message may be the first message (MsgA) in a two-step RA procedure or the third message (Msg3) in a four-step RA procedure. In some example embodiments, the transition indication may include a buffer status report (BSR) indicating buffered data for SDT transmission. In some example embodiments, the transition indication may include a medium access control (MAC) control element (CE) and / or a logical channel identifier (LCID) in a MAC subheader. The MAC CE and / or LCID may indicate a transition, a preamble group for SDT transmission, or a transport block size (TBS) index for constructing a transport block (TB) for SDT transmission. In some example embodiments, the transition indication may include a common control channel (CCCH) service data unit (SDU) from the SDT transmission.

[0086] In some example embodiments, the message received in step 610 may also include a CCCHSDU or a random number from an SDT transmission for identifying the UE. Figure 8Not shown, but the network device may generate a contention solution based on the CCCH SDU or a random number from the SDT transmission, and send the contention solution to the UE in a MsgB or Msg4 message.

[0087] refer to Figure 8 The method 800 may further include step 620 of allocating a UL grant to the UE after the RA process. Since the network device knows that the UE falls back from the SDT process to the RA process, the UL grant allocated in step 620 may be large enough to accommodate the TB for SDT transmission.

[0088] Then, in step 630, the network device may receive the TB on the allocated UL grant from the UE. In this way, the TB generated during the SDT process may be sent to the network device via the RA process.

[0089] Fig. 9 700 according to some example embodiments. The method 700 may be implemented in a system such as Figure 1 The method 700 may be implemented at a network device of the BS 120 shown in FIG. For example, the steps of the method 700 may be performed by a device, module, or element of a device implemented at the BS 120. Some details of the method 700 have been described above with reference to FIG. Figure 2-7 The process shown in FIG. 7 is discussed, and a brief description of method 700 is given here. For a better understanding, reference can be made to Figure 2-7 The following description of method 700 should be read in light of the above description.

[0090] refer to Fig. 9 , method 700 may include step 710, receiving a message including a payload from a user equipment (UE) on a first uplink (UL) grant in a random access (RA) procedure. The message may be the first message (MsgA) in a 2-step RA procedure or the third message (Msg3) in a 4-step RA procedure. The payload may include a first portion of a transport block (TB) for a small data transfer (SDT). For example, the first portion of the TB may include at least a common control channel (CCCH) service data unit (SDU) from the TB. In some example embodiments, the first portion of the TB may also include an additional MAC CE and / or MAC SDU from the TB.

[0091] The method 700 may further include a step 720 of allocating a UL grant to the UE. For example, the network device may send the UL grant to the UE on a PDCCH channel.

[0092] Then, in step 730, the network device may receive the remaining portion of the TB on the allocated UL grant from the UE. In this way, the TB generated during the SDT process may be sent to the UE via the RA process.

[0093] Fig.10 8 is a block diagram illustrating an example communication system 800 in which example embodiments of the present application may be implemented. Fig.10 As shown, the communication system 800 may include a user equipment (UE) 810 which may be implemented as the above-mentioned UE 110, and a network device 820 which may be implemented as the above-mentioned BS 120. Fig.10 Only one UE 810 is shown, but it should be understood that the communication system 800 may include multiple UEs 810 wirelessly connected to the network device 820.

[0094] refer to Fig.10 , UE 810 may include one or more processors 811, one or more memories 812, and one or more transceivers 813 interconnected by one or more buses 814. The one or more buses 814 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fibers, optical devices, or other optical communication devices. Each of the one or more transceivers 813 may include a receiver and a transmitter connected to one or more antennas 816. UE 810 may wirelessly communicate with network device 820 via one or more antennas 816. The one or more memories 812 may include computer program code 815. The one or more memories 812 and the computer program code 815 may be configured to, when executed by the one or more processors 811, cause the user equipment 810 to perform the processes and steps related to UE 110 as described above.

[0095] The network device 820 may include one or more processors 821, one or more memories 822, one or more transceivers 823, and one or more network interfaces 827 interconnected by one or more buses 824. The one or more buses 824 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fiber, optical device, or other optical communication device, etc. Each of the one or more transceivers 823 may include a receiver and a transmitter connected to one or more antennas 826. The network device 820 may operate as a base station for the UE 810 and communicate wirelessly with the UE 810 through one or more antennas 826. The one or more network interfaces 827 may provide a wired or wireless communication link, and the network device 820 may communicate with other network devices, entities, or functions through a wired or wireless communication link. The one or more memories 822 may include a computer program code 825. The one or more memories 822 and the computer program code 825 may be configured to, when executed by the one or more processors 821, cause the network device 820 to perform the processes and steps related to the BS 120 as described above.

[0096] The one or more processors 811, 821 discussed above may be any suitable type suitable for the local technology network, and may include a general-purpose processor, a dedicated processor, a microprocessor, a digital signal processor (DSP), one or more processors in a processor-based multi-core processor architecture, and one or more of a dedicated processor such as one developed based on a field programmable gate array (FPGA) and an application-specific integrated circuit (ASIC). The one or more processors 811, 821 may be configured to control other elements of the UE / network device and operate in cooperation with them to implement the above process.

[0097] The one or more memories 812, 822 may include at least one storage medium in various forms, such as volatile memory and / or non-volatile memory. Volatile memory may include, but is not limited to, for example, random access memory (RAM) or cache. Non-volatile memory may include, but is not limited to, for example, read-only memory (ROM), hard disk, flash memory, etc. In addition, the one or more memories 812, 822 may include, but are not limited to, electrical, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or equipment or any combination thereof.

[0098] The network device 820 may be implemented as a single network node, or decomposed / distributed over two or more network nodes, such as a central unit (CU), a distributed unit (DU), a remote radio head (RRH), using different functional split architectures and different interfaces.

[0099] It should be understood that the blocks in the drawings can be implemented in various ways, including software, hardware, firmware, or any combination thereof. In some example embodiments, one or more blocks may be implemented using software and / or firmware (e.g., machine executable instructions stored in a storage medium). Additionally or alternatively, machine executable instructions, some or all of the blocks in the drawings may be implemented at least in part by one or more hardware logic components. For example, but not limited to, illustrative types of hardware logic components that may be used include field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system on chip systems (SOCs), complex programmable logic devices (CPLDs), etc.

[0100] Some example embodiments further provide computer program codes or instructions that, when executed by one or more processors, can cause a device or apparatus to perform the above-described processes. Computer program codes for performing the processes of example embodiments can be written in any combination of one or more programming languages. The computer program code can be provided to one or more processors or controllers of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the program code causes the functions / operations specified in the flow chart and / or block diagram to be implemented when executed by the processor or controller. The program code can be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0101] Some example embodiments further provide a computer program product or computer readable medium having a computer program code or instruction stored therein. A computer readable medium may be any tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or apparatus. A machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or device, or any suitable combination of the foregoing. A more specific example of a machine readable storage medium would include an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0102] In addition, although the operations are described in a particular order, this should not be understood as requiring the operations to be performed in the particular order shown or in sequence, or requiring the execution of all illustrated operations to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be understood as limitations on the scope of the present application, but should be understood as descriptions of features that may be specific example embodiments. Certain features described in the case of separate example implementations may also be implemented in combination in a single example embodiment. Conversely, the various features described in the case of a single example embodiment may also be implemented in multiple example embodiments individually or in any suitable sub-combination.

[0103] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims.

[0104] The abbreviations used in the specification and / or drawings are defined as follows:

[0105] BS Base Station

[0106] BSR Buffer Status Report

[0107] C-RNTI Cell-Radio Network Temporary Identifier

[0108] gNB Next Generation Base Station

[0109] LCID Logical Channel Identifier

[0110] MAC Media Access Control

[0111] Msg

[0112] NR New Radio

[0113] PDCCH Physical Downlink Control Channel

[0114] PDSCH Physical Downlink Shared Channel

[0115] PRACH Physical Random Access Channel

[0116] RACH Random Access Channel

[0117] RAR Random Access Response

[0118] RRC Radio Resource Control

[0119] RSRP Reference Signal Received Power

[0120] SDT Small Data Transfer

[0121] TA Timing Advance

[0122] UE User Equipment

Claims

1. A user equipment (UE), comprising: at least one processor; as well as at least one memory including computer program code, the at least one memory and the computer program code being configured, together with at least one processor, to cause the UE to: Initiating a small data transfer (SDT) process for transmitting uplink data to a network device; determining whether a condition is satisfied after initiating the SDT process to send the uplink data, and determining whether the SDT process has not successfully sent the uplink data to the network device; as well as When the condition is satisfied and the SDT process has not successfully sent the uplink data to the network device, switching from the SDT process to another process for the uplink data transmission, The conditions include one or more of the following: A reference signal received power (RSRP) measured at the UE is lower than a first threshold; or the timing alignment for the UE becomes invalid, And wherein the other process is a random access (RA) process different from the SDT process.

2. The UE according to claim 1, wherein: The conditions also include one or more of the following: The RSRP measured at the UE is below the first threshold by more than a predetermined offset; The number of SDT attempts reaches the second threshold; The RSRP measured at the UE is lower than the first threshold for a number of SDT attempts equal to the second threshold; as well as The beam with SDT resources becomes unavailable to the UE.

3. The UE according to claim 1, wherein: The UE is configured with random access channel (RACH) resources in the RA procedure, which are different from those configured in the SDT procedure.

4. The UE according to claim 1, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the UE to: In the RA process, a message including the conversion indication is sent to the network device.

5. The UE according to claim 4, wherein: The message is the first message (MsgA) in a two-step RA procedure or the third message (Msg3) in a four-step RA procedure.

6. The UE according to claim 4, wherein: The indication includes a buffer status report (BSR) indicating buffered data for the SDT transmission.

7. The UE according to claim 4, wherein: The indication includes a medium access control (MAC) control element (CE) or a logical channel identifier (LCID) in a MAC subheader to indicate: The conversion, A preamble group for the SDT transmission, or A transport block size (TBS) index for constructing a transport block (TB), the TB including the uplink data for the SDT transmission.

8. The UE according to claim 4, wherein: The indication includes a common control channel (CCCH) service data unit (SDU) from the SDT transmission.

9. The UE according to claim 4, wherein: The message further includes: A random number generated at the UE or from the CCCH SDU of the SDT transmission is used to identify the UE.

10. The UE according to claim 9, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the UE to: In the RA procedure, a message including a contention resolution generated based on the random number or the CCCH SDU from the SDT transmission is received.

11. The UE according to claim 4, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the UE to: receiving an uplink grant from the network device, the uplink grant being capable of accommodating a transport block (TB) including the uplink data generated during the SDT process; as well as A TB including the uplink data is sent to the network device on the uplink grant.

12. The UE according to claim 11, wherein: The TB including the uplink data is stored in a MAC buffer.

13. The UE according to claim 1, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the UE to: A message is sent to the network device, the message including a payload on a first uplink (UL) grant in the RA process, the payload including a first portion of a transport block (TB), the transport block (TB) including the uplink data generated in the SDT process.

14. The UE according to claim 13, wherein: The message is the first message (MSGA) in a two-step RA procedure or the third message (Msg3) in a four-step RA procedure.

15. The UE according to claim 13, wherein: The first part of the TB includes at least the CCCHSDU from the TB.

16. The UE according to claim 15, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the UE to: Based on the CCCH SDU from the TB, a preamble group is selected for the RA procedure.

17. The UE according to claim 13, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the UE to: The remainder of the TB is sent on one or more subsequent UL grants.

18. The UE according to claim 1, wherein: When the SDT attempt fails, the UE remains in an inactive state, and / or when the SDT attempt fails a predetermined number of times, the UE enters an idle state.

19. A network device comprising: at least one processor; as well as at least one memory including computer program code, the at least one memory and the computer program code being configured, together with the at least one processor, to cause the network device to: When a condition is satisfied and a small data transfer (SDT) process has not successfully sent uplink data to the network device, receiving a message from a user equipment (UE), the message including an indication to switch from the SDT process to another process to send the uplink data to the network device, The conditions include one or more of the following: A reference signal received power (RSRP) measured at the UE is lower than a first threshold; or the timing alignment for the UE becomes invalid, And wherein the other process is a random access (RA) process different from the SDT process.

20. The network device according to claim 19, wherein: The message is the first message (MsgA) in the RA procedure when the RA procedure is a 2-step RA procedure, or the message is the third message (Msg3) in the RA procedure when the RA procedure is a 4-step RA procedure.

21. The network device according to claim 19, wherein: The indication includes a buffer status report (BSR) indicating buffered data for SDT transmission.

22. The network device of claim 19, wherein: The indication includes a medium access control (MAC) control element (CE) or a logical channel identifier (LCID) in a MAC subheader to indicate: The conversion, Preamble group for SDT transmission, or Transport Block Size (TBS) index used to construct transport blocks (TBs) for SDT transmission.

23. The network device of claim 19, wherein: The indication includes a common control channel (CCCH) service data unit (SDU) from the SDT transmission.

24. The network device of claim 19, wherein: The message further includes: The CCCH SDU or random number from the SDT transmission is used to identify the UE.

25. The network device of claim 24, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the network device to: In the RA procedure, a message including a contention resolution based on the CCCH SDU from the SDT transmission or the random number generation is sent.

26. The network device of claim 19, wherein: The at least one memory and the computer program code are further configured to, with the at least one processor, cause the network device to: An uplink (UL) grant is allocated to the UE after the RA procedure, the UL grant being able to accommodate the TB for SDT transmission.

27. A method implemented at a user equipment (UE), comprising: Initiating a small data transfer (SDT) process for transmitting uplink data to a network device; determining whether a condition is satisfied after initiating the SDT process to send the uplink data, and determining whether the SDT process has not successfully sent the uplink data to the network device; as well as When the condition is satisfied and the SDT process has not successfully sent the uplink data to the network device, switching from the SDT process to another process for the uplink data transmission, The conditions include one or more of the following: A reference signal received power (RSRP) measured at the UE is lower than a first threshold; or the timing alignment for the UE becomes invalid, And wherein the other process is a random access (RA) process different from the SDT process.

28. The method of claim 27, wherein: The conditions also include one or more of the following: The RSRP measured at the UE is below the first threshold by more than a predetermined offset; The number of SDT attempts reaches the second threshold; The RSRP measured at the UE is lower than the first threshold for a number of SDT attempts equal to the second threshold; as well as The beam with SDT resources becomes unavailable to the UE.

29. The method of claim 27, wherein: The UE is configured with random access channel (RACH) resources in the RA procedure, which are different from those configured in the SDT procedure.

30. The method of claim 27, further comprising: In the RA process, a message including the conversion indication is sent to the network device.

31. The method of claim 30, wherein: The indication includes a buffer status report (BSR) indicating buffered data for the SDT transmission.

32. The method of claim 30, wherein: The indication includes a medium access control (MAC) control element (CE) or a logical channel identifier (LCID) in a MAC subheader to indicate: The conversion, A preamble group for the SDT transmission, or A transport block size (TBS) index used to construct a transport block (TB), the TB including uplink data for the SDT transmission.

33. The method of claim 30, wherein: The indication includes a common control channel (CCCH) service data unit (SDU) from the SDT transmission.

34. The method of claim 30, wherein: The message further includes: A random number generated at the UE or from a CCCH SDU of an SDT transmission to identify the UE.

35. The method of claim 34, further comprising: In the RA procedure, a message including a contention resolution generated based on the random number or the CCCH SDU from the SDT transmission is received.

36. The method of claim 30, further comprising: receiving an uplink grant from the network device, the uplink grant being capable of accommodating a transport block (TB) including the uplink data generated during the SDT process; as well as A TB including the uplink data is sent to the network device on the uplink grant.

37. The method of claim 27, further comprising: A message is sent to the network device, the message including a payload on a first uplink (UL) grant in the RA process, the payload including a first portion of a transport block (TB), the transport block (TB) including the uplink data generated in the SDT process.

38. The method of claim 37, wherein: The first part of the TB includes at least the CCCHSDU from the TB.

39. The method of claim 38, further comprising: Based on the CCCH SDU from the TB, a preamble group is selected for the RA procedure.

40. The method of claim 37, further comprising: The remainder of the TB is sent on one or more subsequent UL grants.

41. The method of claim 27, wherein: When the SDT attempt fails, the UE remains in an inactive state, and when the SDT attempt fails a predetermined number of times, the UE enters an idle state.

42. A method implemented at a network device, comprising: When a condition is satisfied and a small data transfer (SDT) process has not successfully sent uplink data to the network device, receiving a message from a user equipment (UE), the message including an indication to switch from the SDT process to another process to send the uplink data to the network device, The conditions include one or more of the following: A reference signal received power (RSRP) measured at the UE is lower than a first threshold; or the timing alignment for the UE becomes invalid, And wherein the other process is a random access (RA) process different from the SDT process.

43. The method of claim 42, wherein: The indication includes a buffer status report (BSR) indicating buffered data for SDT transmission.

44. The method of claim 42, wherein: The indication includes a medium access control (MAC) control element (CE) or a logical channel identifier (LCID) in a MAC subheader to indicate: The conversion, Preamble group for SDT transmission, or Transport Block Size (TBS) index used to construct transport blocks (TBs) for SDT transmission.

45. The method of claim 42, wherein: The indication includes a common control channel (CCCH) service data unit (SDU) from the SDT transmission.

46. ​​The method of claim 42, wherein: The message further includes: The CCCH SDU or random number from the SDT transmission is used to identify the UE.

47. The method of claim 42, further comprising: An uplink (UL) grant is allocated to the UE after the RA procedure, the UL grant being able to accommodate the TB for SDT transmission.

48. A computer-readable medium comprising instructions which, when executed by at least one processor of a user equipment (UE), cause the UE to: Initiating a small data transfer (SDT) process for transmitting uplink data to a network device; determining whether a condition is satisfied after initiating the SDT process to send the uplink data, and determining whether the SDT process has not successfully sent the uplink data to the network device; as well as When the condition is satisfied and the SDT process has not successfully sent the uplink data to the network device, switching from the SDT process to another process for the uplink data transmission, The conditions include one or more of the following: A reference signal received power (RSRP) measured at the UE is lower than a first threshold; or the timing alignment for the UE becomes invalid, And wherein the other process is a random access (RA) process different from the SDT process.

49. A computer-readable medium comprising instructions that, when executed by at least one processor of a network device, cause the network device to: When a condition is satisfied and a small data transfer (SDT) process has not successfully sent uplink data to the network device, receiving a message from a user equipment (UE), the message including an indication to switch from the SDT process to another process to send the uplink data to the network device, in, The conditions include one or more of the following: A reference signal received power (RSRP) measured at the UE is lower than a first threshold; or the timing alignment for the UE becomes invalid, And wherein the other process is a random access (RA) process different from the SDT process.

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