Efficient message passing in a process for accessing a communication channel

Abstract

The base station authorizing the user equipment to access the communication channel includes receiving a request for access to the communication channel from the user equipment, the request including a random access preamble and a payload, attempting to decode the payload, selecting a format of a response message based on whether the payload is successfully decoded, and transmitting the response message to the user equipment, including providing an indication of the format of the response message to the user equipment.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 801,429, filed on February 5, 2019, entitled “Efficient Messaging in a Procedure for Access a Communication Channel,” the entire disclosure of which is expressly incorporated by reference. Technical Field

[0003] The present disclosure relates to wireless communications, and more particularly, to synchronizing wireless communications during a channel access procedure. Background Art

[0004] The background description provided here is to present the context of the present disclosure in general terms. The work of the inventors named in this application is not admitted, either explicitly or implicitly, to be prior art to the present disclosure insofar as it is described in this background section, nor insofar as it may not qualify as prior art when the application was filed.

[0005] To synchronize communications over the radio interface in the unlicensed portion of the radio spectrum, a user device (referred to as user equipment or "UE") and a base station may, for example, use a random access channel (RACH) procedure. Some standards define two types of RACH procedures: a two-step procedure and a four-step procedure. Figure 2 In the four-step process shown, (1) the user equipment sends 202 a random access preamble (also referred to herein as "Msg1") to the base station; (2) the base station sends 204 a random access response (RAR) (also referred to herein as "Msg2") to the user equipment; (3) the user equipment sends 206 a scheduled transmission (also referred to herein as "Msg3") to the base station; and (4) the base station sends 208 a contention resolution (also referred to herein as "Msg4") to the user equipment. Figure 3 The two-step process shown compresses steps (1) and (3) into a first step and compresses steps (2) and (4) into a second step, such that (1) the user equipment sends 302 a random access preamble and scheduled transmission (also referred to herein as “MsgA”) to the base station; and (2) the base station sends 304 a RAR and contention resolution (also referred to herein as “MsgB”) to the user equipment.

[0006] In some scenarios, the user equipment sends a message including a random access preamble and a payload to the base station according to a two-step process. If the base station fails to decode the payload, the base station may transmit only the RAR to the user equipment instead of a message including the RAR and contention resolution. However, the user equipment does not know whether the base station transmits the RAR or the MsgB (i.e., a combination of the RAR and contention resolution) and may not be able to decode the transmission from the base station according to the appropriate process. Summary of the invention

[0007] In general, the technology of the present disclosure allows a user equipment to determine which communication scheme a base station is following during a channel access process, and whether the base station needs additional information from the user equipment. In some embodiments, the channel access communication is a RACH transmission from a base station. The user equipment determines how to decode the RACH transmission based on whether the base station generates the RACH transmission according to a two-step or four-step RACH process format (i.e., whether the base station is using a format including RAR and resolution or a format not including resolution). More specifically, in response to receiving a RACH communication from a user equipment, the base station attempts to decode the payload of the RACH communication. If the base station fails to decode the payload, the base station may determine to proceed with the four-step RACH process. In order to let the user equipment know to switch to the four-step RACH process, in response to the RACH communication sent to the user equipment, the base station includes an indication of falling back to the four-step RACH process. The indication may be the presence of a first radio network temporary identifier (RNTI) in the response, wherein the user equipment associates the first RNTI with the switch to the four-step RACH process. In other embodiments, the indication may be included in a medium access control (MAC) layer packet data unit (PDU) or a downlink control information (DCI) element. In still other embodiments, the response to the RACH communication may include an indication of the size of a portion of the response in the DCI, such as the size of the MAC PDU. If the size is less than a threshold size, the user equipment may decode the MAC PDU according to the four-step RACH procedure format or a format that does not include resolution.

[0008] On the other hand, if the base station successfully decodes the payload, the base station may determine to proceed with the two-step RACH process. In order to let the user equipment know that the base station is responding in a two-step RACH process format, the base station includes an indication of continuing the two-step RACH process in a response to a RACH communication sent to the user equipment. The indication may be the presence of a second RNTI, wherein the user equipment associates the second RNTI with the two-step RACH process. In other embodiments, the indication may be included in a MAC PDU or a DCI. In yet other embodiments, the response to the RACH communication may include an indication of the size of a portion of the response in the DCI (such as the size of the MAC PDU). If the size is greater than or equal to a threshold size, the user equipment may decode the MAC PDU according to a two-step RACH process format or a format including an RAR and a resolution.

[0009] An example embodiment of these techniques is a method in a base station for granting access to a communication channel. The method includes receiving, by processing hardware at the base station, a request from a user device to access the communication channel, the request including a random access preamble and a payload, and attempting to decode the payload by the processing hardware. The method also includes selecting, by the processing hardware, a format of a response message based on whether the payload is successfully decoded, and transmitting, by the processing hardware, the response message to the user device, including providing an indication of the format of the response message to the user device.

[0010] Another embodiment of the techniques is a base station including processing hardware configured to implement the above methods.

[0011] Yet another embodiment of these techniques is a method in a user equipment for requesting access to a communication channel. The method includes transmitting, by processing hardware at the user equipment, a request to access the communication channel to a base station, the request including a random access preamble and a payload, and receiving, by processing hardware, a response message to the request from the base station, the response message indicating a format of the response message based on whether the payload is successfully decoded by the base station. The method also includes determining, by processing hardware, a format of the response message, and decoding, by processing hardware, a portion of the response message according to the determined format.

[0012] Yet another embodiment of the techniques is a user device including processing hardware configured to implement the above methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a block diagram of an example wireless communication network in which a base station and a user equipment may process a channel access procedure according to the techniques of the present disclosure;

[0014] Figure 2 is a message passing diagram of an example four-step RACH procedure;

[0015] Figure 3 is a message passing diagram of an example two-step RACH procedure;

[0016] Figure 4A is a message passing diagram of an example process for signaling to a user equipment a format for decoding a response message from a base station using a radio network temporary identifier (RNTI);

[0017] Figure 4B is a messaging diagram for signaling a first format of a response message from a base station to be decoded to a user equipment using a first RNTI;

[0018] Figure 4C is a messaging diagram for signaling to a user equipment a second format of decoding a response message from a base station using a second RNTI;

[0019] Figure 5 An example format of a medium access control (MAC) protocol data unit (PDU) in a response message including a random access response (RAR) is shown;

[0020] Figure 6 Another example format of a MAC PDU in a response message including a RAR is shown;

[0021] Figure 7 Shown included in Figure 5 or Figure 6 Example format of RAR in a MAC PDU;

[0022] Fig. 8A is a message passing diagram of an example process for signaling to a user equipment the format of decoding a response message from a base station using a PDU;

[0023] Figure 8B is a message passing diagram of an example process for signaling to a user equipment a first format for decoding a response message from a base station using a PDU having a first format indicator;

[0024] Figure 8C is a message passing diagram of an example process for signaling to a user equipment a second format for decoding a response message from a base station using a PDU with a second format indicator;

[0025] Fig. 9 An example format of a MAC sub-PDU within a MAC PDU in a response message including a first MAC sub-header and a RAR is shown;

[0026] Fig.10 Shown included in Fig. 9 Another example format of a RAR in a MAC PDU;

[0027] Fig.11 shows an example format of a MAC sub-PDU included in a MAC PDU in a response message with RAR;

[0028] Fig.12 Shown included in Fig.11 Example format of a Random Access Preamble Identifier (RAPID) Control Element (CE) within the first MAC sub-PDU of

[0029] Fig.13 An example format of a MAC PDU in a response message including a second MAC subheader and MsgB is shown;

[0030] Fig.14 An example format of a MAC PDU in a response message including a second MAC subheader and MsgB is shown;

[0031] Fig.15 An example format of a MAC subheader included within a MAC service data unit (SDU) in a response message is shown;

[0032] Fig.16 Another example format of a MAC subheader included within a MAC SDU in a response message is shown;

[0033] Fig.17 shows yet another example format of a MAC subheader included within a MAC SDU in a response message;

[0034] Fig.18 An example format of a MAC PDU in a response message is shown;

[0035] Fig.19A is a message passing diagram of an example process for signaling to a user equipment the format of decoding a response message from a base station using the size of a PDU;

[0036] Fig.19B is a message passing diagram of an example process for signaling to a user equipment a first format of decoding a response message from a base station when the size of the PDU is less than a threshold size;

[0037] Fig.19C is a message passing diagram of an example process for signaling to a user equipment to decode a second format of a response message from a base station when the size of the PDU is greater than or equal to a threshold size;

[0038] Fig. 20A is a messaging diagram of an example process for signaling to a user equipment the format of decoding a response message from a base station using a downlink control information (DCI) element with a format indicator;

[0039] Fig. 20B is a message passing diagram of an example process for signaling to a user equipment a first format for decoding a response message from a base station using a DCI element with a first format indicator;

[0040] Fig. 20C is a message passing diagram of an example process for signaling to a user equipment a second format for decoding a response message from a base station using a DCI element with a second format indicator;

[0041] Fig.21 is a flow chart of an example method for granting access to a communication channel, which may be Figure 1 is implemented in a base station; and

[0042] Fig. 22 is a flow chart of an example method for requesting access to a communication channel, which may be Figure 1 is implemented in a user device. DETAILED DESCRIPTION

[0043] under Figure 1 An example wireless communication network 100 is depicted in which devices such as base stations and user devices (also referred to as user equipment or UE) communicate using a channel access procedure on unlicensed portions of the radio spectrum. Since the following examples primarily relate to 5G NR technology, these unlicensed portions of the radio spectrum are referred to as NR-U.

[0044] The wireless communication network 100 in the example configuration includes a UE 102, which can be any suitable device capable of wireless communication (as further discussed below). The wireless communication network 100 also includes a 5G New Radio (NR) base station 104 connected to a CN 106 of a core network (CN) type 5GC. The 5G NR base station 104 operates as a gNodeB (gNB) accordingly. However, in other embodiments, the wireless communication network 100 may include one or more base stations operating according to a type of radio access technology (RAT) other than NR, and these base stations may be connected to CNs of other CN types, or operate in a standalone mode without being connected to any CN. Therefore, when attempting to obtain radio resources in an unlicensed spectrum, a device operating using any RAT can implement the techniques of the present disclosure.

[0045] Base station 104 covers a 5G NR cell 108 in which UEs can utilize NR-U and a portion of the radio spectrum specifically allocated to the service provider operating base station 104 and core network 106. UE 102 can share NR-U with other devices when receiving data from base station 104 and transmitting data to base station 104 using the 5G NR air interface. For example, UE 110 can be a subscriber of a service provider operating base station 104 and core network 106, and can therefore communicate with base station 104. In another scenario, UE 110 is a subscriber of another service provider that supports NR-U and communicates with a base station other than base station 104 (not shown to avoid confusion). In this scenario, the user operates base station 104 and connects base station 104 to the data network of an Internet service provider (ISP). In this case, base station 104 operates similarly to a WiFi access point (AP), but utilizes NR-U instead of one of the IEEE802.11 standards to communicate with the UE. Furthermore, when operating in a wireless local area network (WLAN) according to one of the IEEE 802.11 standards, AP 112 may utilize a portion of the radio spectrum as NR-U.

[0046] In general, the wireless communication network 100 may include any number of base stations, and each base station may cover one, two, three, or any other suitable number of cells. In addition, the wireless communication network 100 may include any number of UEs 102 .

[0047] The UE 102 is equipped with processing hardware 120, which may include one or more general-purpose processors (e.g., CPUs) and non-transitory computer-readable memory storing instructions executed by the one or more general-purpose processors. Additionally or alternatively, the processing hardware 120 may include a dedicated processing unit. The processing hardware 120 in the example implementation includes a channel access request generator 122, a response message decoder 124, and a downlink transmission processor 126.

[0048] The channel access request generator 122 may generate an MsgA having a random access preamble and a payload. In some embodiments, the payload in the MsgA is a MAC PDU. The payload may include an uplink common control channel (CCCH) message having an RRC request message (e.g., an RRC establishment request message, an RRC recovery request message, an RRC reconstruction request message, or an RRC early data request message). In other embodiments, the payload may include an Internet Protocol (IP) packet. The MAC PDU may include an RRC request message, a MAC control element (CE), a radio link control (RLC) PDU, a packet data convergence protocol (PDCP) PDU, or a service data adaptation protocol (SDAP) PDU. The base station 104 may provide a response message to the MsgA including a DCI on a physical downlink control channel (PDCCH) and a MAC PDU in a physical data shared channel (PDSCH). Then, the response message decoder 124 may decode the response message by obtaining the DCI. When the response message decoder 124 successfully obtains the DCI, the downlink transmission processor 126 can receive the PDSCH transmission including the MAC PDU according to the DCI. The response message decoder 124 can then decode the MAC PDU according to the format indicated by the DCI, RNTI, or MAC PDU. For example, the DCI, RNTI, or MAC PDU can indicate that the MAC PDU adopts a first format with RAR. Therefore, the response message decoder 124 can decode the MAC PDU using the first format. In another example, the DCI, RNTI, or MAC PDU can indicate that the MAC PDU adopts a second format with MsgB. Therefore, the response message decoder 124 can decode the MAC PDU using the second format.

[0049] The memory of the processing hardware 120 may also store the RNTI 128 of the UE 102. The RNTI may be, for example, a cell RNTI (C-RNTI), a temporary C-RNTI, a random access RNTI (RA-RNTI), a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a configured scheduling RNTI (CS-RNTI), etc. The UE 102 may attempt to decode the PDCCH using the RNTI 128. The base station 104 may transmit one or more MAC PDUs in the PDSCH to the UE 102. The one or more MAC PDUs may include one or more MAC control elements. The UE 102 may store multiple RNTIs of different types and utilize these RNTIs when processing different messages, as described below.

[0050] The processing hardware 130 of the base station 104 may also include one or more general purpose processors, such as a CPU and a non-transitory computer readable memory storing instructions executed by the one or more general purpose processors. Additionally or alternatively, the processing hardware 130 may include a dedicated processing unit. The processing hardware in the example implementation includes a payload decoder 132, a DCI controller 134, a PDU controller 136, and an RNTI generator 138. In other implementations, the processing hardware 130 includes only some of the units 132-138.

[0051] In operation, the payload decoder 132 attempts to decode the payload included in the MsgA from the UE 102. If the payload decoder 132 cannot successfully decode the payload, the payload decoder 132 may provide an indication to the DCI controller 134, the PDU controller 136, and / or the RNTI generator 138 to generate a first DCI, a first PDU, or a first RNTI, indicating to the UE 102 to decode the MAC PDU in the first format with the RAR. If the payload decoder 132 successfully decodes the payload, the payload decoder 132 may provide an indication to the DCI controller 134, the PDU controller 136, and / or the RNTI generator 138 to generate a second DCI, a second PDU, or a second RNTI, indicating to the UE 102 to decode the MAC PDU in the second format with the MsgB.

[0052] The DCI controller 134 generates DCI to be transmitted to the UE 102 via the PDCCH. In some embodiments, the DCI is generated so that the UE 102 obtains the information required to decode the information on the PDSCH. For example, when the DCI controller 134 generates a first DCI, the UE 102 determines to decode the MAC PDU transmitted on the PDSCH in a first format with RAR. When the DCI controller 134 generates a second DCI different from the first DCI, the UE 102 determines to decode the MAC PDU transmitted on the PDSCH in a second format with MsgB. The first and second DCIs are described in more detail below.

[0053] The PDU controller 136 generates a MAC PDU to be transmitted to the UE 102 via the PDSCH. In some embodiments, the generated MAC PDU indicates the format of the MAC PDU to be decoded by the UE 102. For example, when the PDU controller 136 generates a first MAC PDU having a first MAC subheader, the UE 102 determines to decode the MAC PDU in a first format having RAR. When the PDU controller 136 generates a second MAC PDU having a second MAC subheader different from the first MAC subheader, the UE 102 determines to decode the MAC PDU transmitted on the PDSCH in a second format having MsgB. The first and second MAC PDUs and the first and second MAC subheaders are described in more detail below.

[0054] The RNTI generator 138 generates an RNTI for scrambling the DCI to be transmitted to the UE 102 via the PDCCH. In some embodiments, the RNTI is generated so that the UE 102 obtains the information required to decode the information on the PDSCH. For example, when the RNTI generator 138 generates a first RNTI, the UE 102 determines to decode the MAC PDU transmitted on the PDSCH in a first format with RAR. When the RNTI generator 138 generates a second RNTI different from the first RNTI, the UE 102 determines to decode the MAC PDU transmitted on the PDSCH in a second format with MsgB. For example, the RNTI generator 138 can generate a first RNTI based on the characteristics of a physical random access channel (PRACH) transmitting MsgA. The RNTI generator 138 can generate a second RNTI as an RNTI included in the payload of the MsgA transmitted by the UE 102. In another example, the RNTI generator 138 can generate a second RNTI based on a UE identifier (ID) associated with the UE 102. In yet another example, the RNTI generator 138 may generate the second RNTI based on other characteristics of the PRACH that transmits Msg A. The first and second RNTIs are described in more detail below.

[0055] As described above, during the channel access process, the UE 102 sends a MsgA including a random access preamble and a payload to the base station 104. The base station 104 then attempts to decode the payload. If the base station 104 fails to decode the payload, the base station 104 may provide a response to the UE 102 in a first format. For example, the base station 104 may provide a RAR to the UE 102 without a resolution, as in a four-step RACH process. On the other hand, if the base station 104 successfully decodes the payload, the base station 104 may provide a response to the UE 102 in a second format. For example, the base station 104 may provide both a RAR and a resolution to the UE 102, as in a two-step RACH process. In some embodiments, the base station 104 provides an indication of the format of the decoding response message to the UE 102 using the RNTI.

[0056] Figure 4A A message passing diagram illustrating an example process for signaling a format of a response message to be decoded from a base station using an RNTI to a user equipment. The UE 102 sends 402A MsgA to the base station 104, including a random access preamble and a payload. The base station 104 then attempts to decode 404A the payload. If the base station 104 detects the preamble in MsgA but fails to decode the payload, the base station 104 generates a RAR instead of MsgB, a MAC subheader for the RAR, and a MAC PDU including the MAC subheader and the RAR. The MAC subheader may include an extension (E), a type (T), and / or a random access preamble identifier (RAPID) field.

[0057] To indicate the format of the response message, the base station 104 applies the first identifier of the UE 102 to the response message in a first instance when the payload is not successfully decoded, and applies the second identifier of the UE 102 to the response message in a second instance when the payload is successfully decoded. More specifically, to transmit the MAC PDU, the base station 104 generates a first RNTI and a DCI and. In some embodiments, the base station 104 scrambles 410A the CRC of the DCI with the first RNTI. In one example, the first RNTI can be the first identifier of the UE 102 and is assigned to the UE 102 by the base station 104. In another example, the first RNTI is a RA-RNTI. The base station 104 calculates the RA-RNTI based on the time and frequency resources of the MsgA or the preamble in the MsgA, as described in more detail below. Then, the base station 104 transmits 420A the DCI and CRC scrambled with the first RNTI to the UE 102 on the PDCCH. The base station also transmits 430 an AMAC PDU to the UE 102 on the physical resources, transport blocks or PDSCH indicated in the DCI.

[0058] On the other hand, if the base station 104 detects the preamble in MsgA and successfully decodes the payload, the base station 104 generates a MAC PDU including MsgB. In some embodiments, MsgB includes one or more fields in the RAR, one or more MAC control elements (CEs), one or more new fields (not included in the RAR), or at least one MAC service data unit (SDU). The MAC SDU may include a radio link control RLC PDU or an RRC response message (e.g., an RRC setup message, an RRC recovery message, or an RRC reconstruction message).

[0059] In one example, if the base station 104 receives MsgA from the UE 102, the base station 104 may include at least some of the following information in MsgB: C-RNTI, timing advance (TA) command, contention resolution identification (ID), downlink (DL) authorization, and / or MAC SDU. The size of the C-RNTI may be 16 bits, and the size of the TA command may be 12 bits. If the payload of MsgA includes an uplink CCCH message, the contention resolution ID may be 48 bits. The base station 104 may generate a contention resolution ID from a CCCH message (e.g., including an RRC establishment request, an RRC recovery request, an RRC reconstruction request, or an RRC early data request message). For example, if the base station 104 determines that the contention resolution ID is included in MsgB or a MAC PDU containing MsgB, the base station 104 includes the first 48 bits of the uplink CCCH message in the contention resolution ID. The size of the DL authorization may be 27 bits. However, if the MAC SDU is included in MsgB, a DL authorization may not be required. The MAC SDU may be of fixed size or variable size, and may not be included if a DL grant is included in Msg B. A DL grant may also be referred to as a DL allocation.

[0060] To transmit the MAC PDU, the base station 104 generates a second RNTI and a DCI, and scrambles the DCI with the second RNTI. In some embodiments, the base station 104 scrambles 410A the CRC of the DCI with the second RNTI. In one example, the second RNTI can be a second identifier of the UE 102 and is assigned to the UE 102 by the base station 104. In another example, the base station 104 calculates the second RNTI based on the time and frequency resources of MsgA, as described in more detail below. The base station 104 then transmits 420A the DCI and CRC scrambled with the second RNTI to the UE 102 on the PDCCH. The base station also transmits 430A the MAC PDU to the UE 102 on the physical resources, transport blocks, or PDSCH indicated in the DCI.

[0061] Then, the UE 102 determines whether the response includes the first RNTI or the second RNTI by using the first and second RNTIs. The UE 102 may use the allocated first RNTI or may calculate the first RNTI based on the time and frequency resources of MsgA or the preamble in MsgA, as described in more detail below. The UE 102 may use the allocated second RNTI or may calculate the second RNTI based on the time and frequency resources of MsgA, as described in more detail below. Then, the UE 102 detects the PDCCH in one or more PDCCH opportunities. If the UE 102 receives the DCI and CRC scrambled with the RNTI in the PDCCH opportunity, the UE 102 determines 440A whether the CRC is scrambled with the first or second RNTI. The UE 102 identifies the DCI and obtains the PDSCH including the MAC PDU based on the DCI. Then, the UE 102 decodes the MAC PDU using the format indicated by the RNTI. There are different implementations to determine or verify whether the CRC is scrambled with the first or second RNTI. In one embodiment, the UE 102 calculates 440A a CRC from the DCI and scrambles the CRC with a first RNTI. If the CRC scrambled with the first RNTI is the same as the CRC scrambled with the RNTI, the UE 102 determines that the received CRC is scrambled with the first RNTI. In addition, the UE 102 calculates a CRC from the DCI and scrambles the CRC with a second RNTI. If the CRC scrambled with the second RNTI is the same as the CRC scrambled with the RNTI, the UE 102 determines that the received CRC is scrambled with the second RNTI. In another embodiment, the UE 102 calculates a CRC from the DCI. The UE 102 descrambles the CRC scrambled with the RNTI using the first RNTI. If the calculated CRC is the same as the descrambled CRC, the UE 102 determines that the received CRC is scrambled with the first RNTI. In addition, the UE 102 descrambles the CRC scrambled with the RNTI using the second RNTI. If the calculated CRC is the same as the descrambled CRC, the UE 102 determines that the received CRC is scrambled with the second RNTI.

[0062] More specifically, in the first example, if the CRC is scrambled with the first RNTI, the UE 102 decodes 442A the MAC PDU using the format of the MAC PDU including the RAR without resolution. The UE 102 can identify the RAR from the first MAC subheader. The UE 102 then proceeds to provide 450A additional information to the base station 104, such as transmission of the payload / schedule, as in the four-step RACH process. In response, the base station 104 transmits 450A a contention resolution to the UE 102.

[0063] In the second example, if the CRC is scrambled with the second RNTI, the UE 102 decodes 444A the MAC PDU using the format of the MAC PDU including MsgB (eg, with resolved RAR). The UE 102 can identify the MsgB based on the corresponding MAC subheader.

[0064] Figure 4B shows that when the base station 104 cannot decode the payload from the UE 102 Figure 4A Detailed message passing diagram of the example process shown in . UE 102 sends 402B MsgA to base station 104, and MsgA includes a random access preamble and a payload. Then, base station 104 attempts to decode 404B payload. Base station 104 detects the preamble in MsgA but fails to decode 406B payload. As a result, base station 104 generates a RAR instead of MsgB, a first MAC subheader of the RAR, and a MAC PDU including the first MAC subheader and the RAR. In some embodiments, the RAR includes at least some of the following: a reserved bit, one or more TA commands, one or more uplink (UL) grants, or one or more temporary C-RNTIs.

[0065] To transmit the MAC PDU, the base station 104 generates 410B a first RNTI, a DCI scrambled with the first RNTI, and a CRC of the DCI. In some embodiments, the first RNTI may be associated with a PRACH for transmitting MsgA. The PRACH includes physical resources for transmitting MsgA and may be divided into a first part and a second part. The first part of the PRACH includes a first physical resource for transmitting a preamble of MsgA, and the second part of the PRACH includes a second physical resource for transmitting a payload. The first RNTI may be generated (or calculated) as:

[0066] First RNTI=1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id, where:

[0067] s_id is the index of the first orthogonal frequency division multiplexing (OFDM) symbol of PRACH (0≤s_id<14), t_id is the index of the first time slot of PRACH in the system frame (0≤t_id<80),

[0068] f_id is the index of the first part of PRACH in the frequency domain (0≤f_id<8), and

[0069] ul_carrier_id is the UL carrier used for MsgA transmission (0 indicates NUL carrier, and 1 indicates SUL carrier). The first RNTI may be a RA-RNTI.

[0070] Then, the base station 104 transmits 420B DCI and CRC scrambled with the first RNTI to the UE 102 on the PDCCH. The base station 104 also transmits 430B MAC PDU to the UE 102 on the physical resource, transport block or PDSCH indicated in the DCI. Then, the UE 102 identifies whether the response includes the first RNTI or the second RNTI by using both the first and second RNTIs. For example, the UE 102 can obtain or generate the first RNTI using the above equation. Then, the UE 102 monitors the PDCCH in one or more PDCCH opportunities and determines 440B whether the CRC is scrambled with the first or second RNTI. More specifically, the UE 102 can attempt to verify the CRC using the first RNTI and the DCI, as described above. If the UE 102 successfully verifies the CRC with the first RNTI and the DCI, the UE 102 can determine that the CRC is scrambled with the first RNTI. If the UE 102 does not successfully decode the CRC with the first RNTI, the UE 102 can attempt to verify the CRC with the second RNTI. If UE 102 successfully verifies the CRC with the second RNTI, UE 102 may determine that the CRC is scrambled with the second RNTI.

[0071] In any case, UE 102 identifies the DCI and obtains the PDSCH including the MAC PDU according to the DCI. Then, UE 102 decodes the MAC PDU using the format indicated by the RNTI. More specifically, because the CRC is scrambled with the first RNTI, UE 102 decodes the 448B MAC PDU using the format of the MAC PDU including the RAR without resolution. UE 102 can identify the RAR from the first MAC subheader. Then, UE 102 continues to provide 450B additional information to the base station 104, such as the transmission of the payload / schedule, as in the four-step RACH process. In response, the base station 104 transmits 452B contention resolution to the UE 102.

[0072] Figure 4C shows when base station 104 successfully decodes the payload from UE 102 Figure 4ADetailed message passing diagram of the example process shown in . UE 102 sends 402C MsgA to base station 104, which MsgA includes a random access preamble and a payload. Then, base station 104 detects the preamble in MsgA and successfully decodes 404C the payload. As a result, base station 104 generates a MAC PDU including MsgB. In some embodiments, MsgB includes one or more fields in the RAR, one or more MAC CEs, one or more new fields (not included in the RAR), or at least one MAC SDU. In some embodiments, base station 104 can generate a MAC PDU, which includes a MAC subheader having a reserved (R) field, a format (F) field, a logical channel identifier (LCID) field and / or a length (L), and MsgB. In order to transmit the MAC PDU, base station 104 generates 410C a second RNTI having a different value from the first RNTI, a DCI scrambled with the second RNTI, and a CRC of the DCI.

[0073] In some embodiments, UE 102 includes a second RNTI in the payload of MsgA. For example, the second RNTI may be a C-RNTI assigned to UE 102 by base station 104 or another base station 104. In other embodiments, UE 102 includes a UE identification (ID) in MsgA. Then, base station 104 generates, derives, or calculates the second RNTI from the UE ID. For example, the second RNTI may be equal to the output of a function with UE ID as the function input, i.e., second RNTI=function(UE ID). The function may be a hash function or a modulo operation. In yet other embodiments, the second RNTI may be associated with the PRACH that transmits MsgA. In one example, the second RNTI may be generated (or calculated) as:

[0074] Second RNTI=1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id, where:

[0075] s_id is the index of the Mth OFDM symbol of PRACH (0≤s_id<14),

[0076] t_id is the index of the Nth time slot of PRACH in the system frame (0≤t_id<80),

[0077] f_id is the index of the first part of PRACH in the frequency domain (0≤f_id<8), and

[0078] The ul_carrier_id is the UL carrier for MsgA transmission (0 represents the NUL carrier, and 1 represents the SUL carrier). M and N are positive integers. In one example, M > 1 and N = 1, 2, …, or 80. In another example, M = 1, 2, …, or 14 and N > 1. In yet another example, 1 < M < 15 and 1 < N < 81.

[0079] In another example, the second RNTI can be generated (or calculated) as:

[0080] Second RNTI = 1 + s_id + 14×t_id + 14×80×f_id + 14×80×8×ul_carrier_id, where:

[0081] s_id is the index of the first OFDM symbol of the second part in the PRACH (0 ≤ s_id < 14),

[0082] t_id is the index of the first time slot of the second part of the PRACH in the system frame (0 ≤ t_id < 80),

[0083] f_id is the index of the second part of the PRACH in the frequency domain (0 ≤ f_id < X, X is an integer and X >= 8), and

[0084] ul_carrier_id is the UL carrier for MsgA transmission (0 represents the NUL carrier, and 1 represents the SUL carrier).

[0085] In additional examples, the second RNTI can be generated (or calculated) as:

[0086] Second RNTI = 1 + s_id + 14×t_id + 14×80×f_id + 14×80×8×ul_carrier_id + offset, where:

[0087] s_id is the index of the first OFDM symbol of the PRACH (0 ≤ s_id < 14),

[0088] t_id is the index of the first time slot of the PRACH in the system frame (0 ≤ t_id < 80),

[0089] f_id is the index of the first part of the PRACH in the frequency domain (0 ≤ f_id < 8),

[0090] ul_carrier_id is the UL carrier for MsgA transmission (0 represents the NUL carrier, and 1 represents the SUL carrier), and

[0091] The offset may be a fixed value or a predetermined value (eg, an integer) specified in the 3GPP specification. Alternatively, the offset may be configured by the base station 104 in a broadcast message or an RRC message.

[0092] Then, the base station 104 transmits 420C DCI and CRC scrambled with the second RNTI to the UE 102 on the PDCCH. The base station also transmits 430C MAC PDU to the UE 102 on the physical resource, transport block or PDSCH indicated in the DCI. Then, the UE 102 identifies whether the response message includes the first RNTI or the second RNTI by using both the first and second RNTIs. For example, the UE 102 can obtain or generate the second RNTI as the RNTI in the payload included in the MsgA. In another example, the UE 102 can obtain or generate the second RNTI based on the UE ID of the UE 102. In yet other examples, the UE 102 can obtain or generate the second RNTI using the above equation. More specifically, the UE 102 can attempt to verify the CRC with the first RNTI and the DCI, as described above. If the UE 102 successfully verifies the CRC with the first RNTI and the DCI, the UE 102 can determine that the CRC is scrambled with the first RNTI. If UE 102 does not successfully verify the CRC with the first RNTI and DCI, UE 102 may attempt to verify the CRC with the second RNTI and DCI. If UE 102 successfully verifies the CRC with the second RNTI and DCI, UE 102 may determine that the CRC is scrambled with the second RNTI.

[0093] In any case, the UE 102 identifies the DCI and obtains the PDSCH including the MAC PDU according to the DCI. Then, the UE 102 decodes the MAC PDU using the format indicated by the RNTI. More specifically, because the CRC is scrambled with the second RNTI, the UE 102 decodes 444C the MAC PDU using the format of the MAC PDU including MsgB (e.g., RAR and resolution). The UE 102 can identify the MsgB from the second MAC subheader.

[0094] Figure 5 An example format of a MAC PDU in a response message including an RAR is shown. The MAC PDU may also include padding (not shown). In other embodiments, the MAC PDU includes: Figure 6MAC sub-PDU shown. For example, the first MAC sub-header may include an E / T / RAPID field, and the first MAC sub-header and the RAR may be combined into MAC sub-PDU 3. In some scenarios, the base station 104 may not include MAC sub-PDU 1 or MAC sub-PDU 2 in the MAC PDU if it does not need to be transmitted. If the base station 104 determines that other (one or more) MAC sub-PDUs are multiplexed for other (one or more) UEs, the base station 104 may include the other (one or more) MAC sub-PDUs in the MAC PDU. In this case, "n" may be an integer such as 4, 5, 6, etc. The first MAC sub-header and the RAR may be included in any one of sub-PDUs 3, 4, 5, ...n. Figure 6 The MAC subheader in the MAC subheader may include an E field, which is a flag indicating whether the MAC subPDU including the MAC subheader is the last MAC PDU or is not in the MAC PDU. The E field may be set to "1" to indicate that at least another MAC subPDU follows. The E field may be set to "0" to indicate that the MAC subPDU including the MAC subheader is the last MAC subPDU in the MAC PDU. The MAC subheader also includes a T field, which is a flag indicating whether the MAC subheader contains a RAPID or a backoff indicator (BI). The T field may be set to "0" to indicate the presence of the BI field in the subheader. The T field may be set to "1" to indicate the presence of the RAPID field in the subheader. In addition, the MAC subheader may include an R field that may be set to "0" and a BI field that identifies an overload condition in a cell. The size of the BI field may be four bits. In addition, the MAC subheader may include a RAPID field that identifies a random access preamble transmitted in MsgA. The size of the RAPID field may be six bits. If the RAPID in the MAC subheader of the MAC sub-PDU corresponds to one of the random access preambles configured for the SI request, the RAR may not be included in the MAC sub-PDU.

[0095] In some embodiments, if the base station 104 receives the C-RNTI in the payload of MsgA, the base station 104 includes the C-RNTI in the second MAC PDU. If the base station 104 includes the C-RNTI, the base station 104 may not include the contention resolution ID in the second MAC PDU. If the base station 104 does receive the C-RNTI in MsgA, the base station 104 may include the temporary C-RNTI and the contention resolution ID in the second MAC PDU. In one aspect, the base station 104 may include the first 48 bits of the uplink CCCH message in the contention resolution ID. In some examples, the base station 104 may include a MAC SDU in the second MAC PDU. The second MAC PDU may include an RRC response message (e.g., RRC establishment, RRC recovery, RRC reconstruction message, or RRC early data completion message) in response to the RRC request message or include an IP packet. If the base station 104 includes the MAC SDU, the base station 104 may not include a DL grant. Otherwise, the base station 104 may include a DL grant indicating the PDSCH containing the second MAC PDU.

[0096] In some scenarios, the base station 104 detects a message 1 (Msg1) for a 4-step RACH procedure consisting only of a preamble from the UE 102. In response to the detection, the base station 104 generates a third MAC PDU in a second MAC PDU format, the third MAC PDU including a RAR and a MAC subheader of the RAR (e.g., as shown in FIG. Figure 6As shown). The MAC subheader includes the RAPID of the preamble, and the RAR includes a TA command, an UL grant, or a temporary C-RNTI. The base station 104 transmits a third MAC PDU to the UE 102 in response to Msg1. In some embodiments, the base station 104 calculates the RA-RNTI and generates a DCI and a CRC scrambled with the RA-RNTI to transmit the third MAC PDU to the UE 102. The base station 104 transmits the DCI and the CRC scrambled with the RA-RNTI to the UE 102 on the PDCCH and transmits the third MAC PDU in the physical resources (e.g., PDSCH) indicated in the DCI. The UE 102 receives the DCI and the CRC scrambled with the RA-RNTI on the PDCCH. The UE 102 uses the RA-RNTI to verify that the CRC is scrambled with the RA-RNTI. Then, the UE 102 receives the third MAC PDU in the physical resources indicated in the DCI. UE 102 adjusts its uplink timing according to the TA command and transmits message 3 (Msg3) to base station 104 in the physical resources indicated by the UL grant. Base station 104 receives Msg3 from UE 102 in the physical resources indicated in the UL grant. Then, base station 104 transmits DCI and CRC scrambled with temporary C-RNTI to UE 102. UE 102 receives message 4 (Msg4) from base station 104 in the physical resources indicated in the DCI. In some examples, Msg3 may include an uplink CCCH message, IP packet, PDCP PDU, or SDAP PDU as described above. Msg4 may include a contention resolution ID, an RRC response message, an IP packet, a PDCP PDU, or a SDAP PDU as described above. UE 102 verifies whether the contention resolution ID is correct. For example, UE 102 checks whether the contention resolution ID is equal to the first 48 bits of the uplink CCCH message in Msg3. If the contention resolution ID is identical to the first 48 bits of the uplink CCCH message in Msg3, then UE 102 determines that the 4-step RACH procedure is successfully completed.

[0097] Figure 7 An example format of a RAR included in a MAC PDU is shown. The RAR may include a reserved bit, one or more TA commands, one or more UL grants, or one or more temporary C-RNTIs.

[0098] In addition to indicating a format for decoding a response message from a base station using the RNTI, the format may also be indicated by a PDU included in the response message. Fig. 8A A messaging diagram illustrating an example process for signaling to a user equipment the format of a response message to decode from a base station using a PDU. The UE 102 sends 802A MsgA to the base station 104, including a random access preamble and a payload.

[0099] The base station 104 then attempts to decode 804A the payload. If the base station 104 detects the preamble in MsgA but fails to decode the payload, the base station 104 generates 810A a RAR instead of MsgB and a first MAC PDU including a MAC subheader and a RAR. The RAR may be a MAC control element or a MAC SDU. The first MAC PDU may indicate a format for decoding the first MAC PDU in the MAC subheader with a first indicator. For example, the first MAC PDU may include a first MAC subheader with a first MAC subheader identifying the RAR. If the RAR is a control element of a fixed size, the first MAC subheader may include a reserved field and an LCID value. If the RAR is a control element of a variable size, the first MAC subheader may include a reserved field, a format field, an LCID field, and a length field. The first MAC subheader indicates to the UE 102 that the first MAC sub PDU adopts a first format including the RAR. In one embodiment, the base station 104 may generate a MAC subheader including an E, T, and / or RAPID field, and include the MAC subheader in the RAR. In another embodiment, the MAC subheader of the RAR does not need to be included in the MAC sub-PDU. Instead, the base station 104 can generate a MAC control element including the RAPID field and generate a MAC subheader of the MAC control element. That is, the base station 104 can generate a second MAC sub-PDU including a MAC subheader and a MAC control element, and include the second MAC sub-PDU in the first MAC PDU together with the first MAC sub-PDU.

[0100] On the other hand, if the base station 104 detects the preamble in MsgA and successfully decodes the payload, the base station 104 generates 810A a second MAC PDU including a second MAC subheader and MsgB. For example, the base station 104 generates a MAC sub-PDU including a second MAC subheader and MsgB. MsgB can be a MAC service data unit (SDU). The second MAC PDU can indicate a format for decoding MsgB in the second MAC subheader with a second indicator. For example, the second MAC subheader may include a reserved field, a format field, an LCID field, and a length field. In some embodiments, MsgB includes one or more fields in the RAR, one or more MAC CEs, one or more new fields (not included in the RAR), or at least one MAC SDU. The MAC SDU may include an RLC PDU or an RRC response message (e.g., an RRC establishment message, an RRC recovery message, an RRC reconstruction message, or an RRC early data completion message).

[0101] To transmit the MAC PDU, the base station 104 generates an RNTI, a DCI scrambled with the RNTI, and a CRC of the DCI. The base station 104 then transmits the DCI scrambled with the RNTI and the CRC on the PDCCH to the UE 102. The base station also transmits 830A the MAC PDU to the UE 102 in the physical resources, transport blocks, or PDSCH indicated in the DCI.

[0102] Then, the UE 102 identifies 840A whether the MAC PDU in the response message includes a first MAC subheader or a second MAC subheader to identify a format for decoding the MAC PDU. Then, the UE 102 decodes the MAC PDU using the format indicated by the first MAC subheader or the second MAC subheader. More specifically, in the first instance, if the MAC PDU includes a first MAC subheader, the UE 102 identifies that the MAC PDU (or a MAC sub-PDU in the MAC PDU) includes a RAR and decodes 842A the RAR according to the RAR format. Then, the UE 102 continues to provide 850A additional information to the base station 104, such as transmission of a payload / schedule in a four-step RACH process. In response, the base station 104 transmits 852A contention resolution to the UE 102.

[0103] In a second example, if the MAC PDU includes a second MAC subheader, the UE 102 identifies that the MAC PDU (or a MAC sub-PDU in the MAC PDU) includes a MsgB and decodes 844A the MsgB according to the MsgB format (eg, with resolved RAR).

[0104] Figure 8B shows that when the base station 104 cannot decode the payload from the UE 102 Fig. 8A Detailed message passing diagram of the example process shown in . UE 102 sends 802B MsgA to base station 104, including a random access preamble and a payload. Then, base station 104 attempts to decode 804B payload. Base station 104 detects the preamble in MsgA but fails to decode 806B payload. As a result, base station 104 generates 810B RAR instead of MsgB, a first MAC subheader of the RAR, and a MAC PDU including the first MAC subheader and the RAR. The first MAC subheader can be a format indicator that a MAC subPDU in a MAC PDU includes a RAR. In some embodiments, the RAR includes at least some of the following: a reserved bit, one or more TA commands, one or more UL grants, or one or more temporary C-RNTIs.

[0105] To transmit the MAC PDU, the base station 104 generates an RNTI, a DCI scrambled with the RNTI, and a CRC of the DCI. The base station 104 then transmits the DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The base station 104 also transmits 830B the MAC PDU to the UE 102 on the physical resource, transport block, or PDSCH indicated in the DCI. The UE 102 then identifies 840B whether the MAC PDU in the response message includes a first MAC subheader or a second MAC subheader.

[0106] Then, the UE 102 decodes the MAC PDU using the format indicated by the identified MAC subheader. More specifically, because the MAC PDU includes the first MAC subheader, the UE 102 identifies the MAC sub-PDU in the MAC PDU including the RAR and decodes 842B the RAR according to the format of the RAR or the format of the MAC sub-PDU. Then, the UE 102 continues to provide 850B additional information to the base station 104, such as the transmission of the payload / scheduled in the four-step RACH process. In response, the base station 104 transmits 852B contention resolution to the UE 102.

[0107] Figure 8C shows when base station 104 successfully decodes the payload from UE 102 Fig. 8A Detailed message passing diagram of the example process shown in . UE 102 sends 802C MsgA to base station 104, including a random access preamble and a payload. Then, base station 104 detects the preamble in MsgA and successfully decodes 804C payload. As a result, base station 104 generates a MAC PDU including MsgB. In some embodiments, MsgB includes one or more fields in the RAR, one or more MACCEs, one or more new fields (not included in the RAR), or at least one MAC SDU. In some embodiments, base station 104 can generate 810C MAC PDU, which includes a second MAC subheader having a reserved field, a format field, an LCID field, and / or a length field, and MsgB. The second MAC subheader can be a format indicator that the MAC PDU adopts a second format including MsgB.

[0108] To transmit the MAC PDU, the base station 104 generates an RNTI, a DCI scrambled with the RNTI, and a CRC of the DCI. The base station 104 then transmits the DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The base station 104 also transmits 830C the MAC PDU to the UE 102 on the physical resource, transport block, or PDSCH indicated in the DCI. The UE 102 then identifies 840C whether the MAC PDU in the response message includes a first MAC subheader or a second MAC subheader.

[0109] Then, the UE 102 decodes the MAC PDU using the format indicated by the identified MAC subheader. More specifically, because the MAC PDU includes the second MAC subheader, the UE 102 identifies that the MAC subPDU in the MAC PDU contains MsgB and decodes 844C MsgB according to the format of MsgB or the format of the MAC subPDU.

[0110] Fig. 9 An example format of a MAC sub-PDU within a MAC PDU in a response message including a first MAC sub-header and a RAR is shown. The MAC sub-PDU includes a first MAC sub-header identifying the RAR. If the RAR is a fixed-size CE, the first MAC sub-header includes an R field (e.g., two bits) and an LCID value (e.g., six bits). If the RAR is a variable-size CE, the first MAC sub-header includes an R field (e.g., one bit), an F field (e.g., one bit), an LCID field (e.g., six bits), and an L field (e.g., eight bits or 16 bits). The RAR has a specific LCID value, which may be defined in the 3GPP specification. If the LCID field contains a specific LCID value for the RAR, the L field indicates the length of the RAR in bytes. The F field indicates the size of the L field. The size of the F field may be one bit. A value of "0" may indicate that the L field is eight bits long. A value of "1" may indicate that the L field is 16 bits long.

[0111] In some embodiments, when the MAC subheader includes information elements (1)-(4), the MAC subheader is a first MAC subheader. Information elements (1)-(4) may include (1) RAPID, (2) TA command, (3) UL grant, and (4) temporary C-RNTI. When the MAC subheader includes information elements (1)-(5), the MAC subheader is a second MAC subheader, wherein information element (5) is a MAC SDU. More specifically, information elements (1)-(5) may include (1) C-RNTI, (2) TA command, (3) contention resolution ID, (4) DL grant, and (5) MAC SDU. Therefore, if the MAC subheader does not include a MAC SDU or includes information elements (1)-(4) having one or more of (1) RAPID, (2) TA command, (3) UL grant, and (4) temporary C-RNTI, the UE 102 may determine that the MAC subheader is a first MAC subheader and decode the MAC PDU in the first format with RAR. If the MAC subheader includes a MAC SDU or includes information elements (1)-(5) having one or more of (1) C-RNTI, (2) TA command, (3) contention resolution ID, (4) DL grant, and (5) MAC SDU, the UE 102 determines that the MAC subheader is a second MAC subheader and decodes the MAC PDU in the second format with MsgB.

[0112] Fig.10 Shown included in Fig. 9 Another example format of a RAR in a MAC PDU of . The RAR may include one or more reserved bits, one or more RAPIDs, one or more TA commands, one or more UL grants, or one or more temporary C-RNTIs.

[0113] Fig.11 An example format of a MAC sub-PDU included in a MAC PDU in a response message with RAR is shown. The MAC PDU includes information elements (1)-(4) which may be CEs. For example, the MAC PDU may include two MAC sub-PDUs. The first MAC sub-PDU may include a first MAC sub-header of a RAPID CE and a RAPID CE. Fig.12 As shown, the RAPID CE may include a RAPID (e.g., six bits and zero or one R field (e.g., two bits). The first MAC subheader may include an R field (e.g., two bits) and an LCID value (e.g., six bits). The second MAC sub-PDU may include a second MAC subheader of an RAR, the RAR including a TA command, an UL grant, and a temporary C-RNTI (e.g., as shown in FIG. Figure 7As shown). If RAR is a fixed-size CE, the second MAC subheader may include an R field (e.g., two bits) and an LCID value (e.g., six bits). If RAR is a variable-size CE, the second MAC subheader may include an R field (e.g., one bit), an F field (e.g., one bit), an LCID field (e.g., 6 bits), and an L field (e.g., eight or 16 bits). The LCID value of the first MAC subheader may be different from the LCID value of the second MAC subheader.

[0114] like Fig.11 As shown, the first and second MAC subheaders may include an R / LCID field or an R / F / LCID / L field. The LCID field may include a specific LCID value for the RAPID CE and a specific LCID value for the RAR. The specific LCID value may be defined in the 3GPP specification. If the LCID field contains a specific LCID value for the RAR, the L field may indicate the length of the RAR in bytes. The F field may indicate the size of the L field. The size of the F field is one bit. The value "0" indicates that the L field is 8 bits. The value "1" indicates that the L field is 16 bits. The R field may be set to "0". In other embodiments, each of the information elements (1)-(4) is a CE and has a corresponding MAC subheader. If the CE is a fixed-size CE, the corresponding MAC subheader may include an R / LCID field. If the CE is a variable-size CE, the corresponding MAC subheader may include an R / F / LCID / L field. Each of the information elements (1)-(4) may have its own LCID value, for example, as required by the corresponding 3GPP specification.

[0115] Fig.13 An example format of a MAC PDU in a response message including a second MAC subheader and Msg B is shown. The second MAC subheader may include an R field (e.g., one bit), an F field (e.g., one bit), an LCID field (e.g., six bits), and an L field (e.g., eight bits or 16 bits).

[0116] Fig.14Another example format of a MAC PDU in a response message including a second MAC subheader and MsgB is shown. In some embodiments, each of information elements (1)-(4) is a CE and has a corresponding MAC subheader. If the base station 104 includes a CE, at least one of the second MAC subheaders includes a corresponding MAC subheader. The MAC SDU may also have a corresponding MAC subheader. If the base station 104 includes a MAC SDU, at least one second MAC subheader includes a corresponding MAC subheader. The size of the padding may be zero so that there is no padding. In addition, in some embodiments, some of the information elements (1)-(5) may be included in the CE, and the CE may have a MAC subheader. For example, the CE may contain information elements (1) and (2) and may have a corresponding MAC subheader. If the base station 104 includes a CE, at least one second MAC subheader may include a corresponding MAC subheader. Each of information elements (3) and (4) is a CE and has a corresponding MAC subheader of the CE. If the base station 104 includes a CE, at least one second MAC subheader includes a corresponding MAC subheader. The MAC SDU may also have a corresponding MAC subheader. If the base station 104 includes the MAC SDU, the at least one second MAC subheader includes the corresponding MAC subheader.

[0117] If the CE has a variable size according to its content, the CE is a variable size MAC CE and the MAC subheader of the variable size MAC CE has four header fields R / F / LCID / L. If the CE has a fixed size, the CE is a fixed size MAC CE and the MAC subheader of the fixed size MAC CE has two header fields R / LCID. In one example, each of the information elements (1)-(4) may have a fixed size. A CE containing one or more of the information elements (1)-(4) may be a fixed size MAC CE and may be a fixed size MAC CE. Fig.17 The MAC subheader in the CE is used for CE. Information element (5) (i.e., MAC SDU) can have a variable size and can be Fig.15 or Fig.16 The MAC subheader in is used for MAC SDU.

[0118] The LCID field in the second MAC subheader identifies the logical channel instance of the corresponding MAC SDU or the type of TA corresponding to the CE or padding. The LCID field size can be six bits. Information elements (1)-(5) have different LCID values, which can be specified in the 3GPP specification. The L field in the second MAC subheader indicates the length of MsgB and the corresponding MAC SDU or variable size CE in bytes. The size of the L field can be indicated by the F field. The F field in the second MAC subheader indicates the size of the length field. The size of the F field is one bit. The value "0" indicates that the L field is eight bits. The value "1" indicates that the L field is 16 bits.

[0119] Fig.18 Another example format of a MAC PDU in a response message is shown. Fig. 9 The MAC sub-PDU shown may be as follows Fig.18 In another example, as shown in FIG. Fig.11 The MAC sub-PDU shown may be as follows Fig.18 If each of the information elements (1)-(4) is a CE and has a corresponding MAC subheader, then the corresponding MAC subheader and CE form Fig.18 MAC sub-PDU included in.

[0120] In some implementations, the UE 102 monitors the PDCCH in one or more PDCCH opportunities with the RNTI. When the UE 102 receives the DCI and CRC scrambled with the RNTI, the UE receives the physical resources (or transport blocks on the PDSCH) according to the DCI to obtain the MAC PDU. The UE 102 uses the MAC PDU format (e.g., Fig.18 In one example, UE 102 finds Fig. 9 UE 102 determines or recognizes that RAR is included in the MAC PDU and Fig. 9 The MAC PDU format shown in FIG. 1 extracts the RAR from the MAC PDU. Then, UE 102 Fig.10 The RAR format shown retrieves information elements (1)-(4).

[0121] In one example, if UE 102 identifies Fig.13If the second MAC subheader is included in the MAC PDU, UE 102 recognizes or determines that MsgB is included in the MAC PDU and extracts MsgB from the MAC PDU according to the fixed size of each of the information elements (1)-(4). If the length field in the second MAC subheader is greater than the sum of the fixed sizes of the information elements (1)-(4), UE 102 extracts information element (5) (i.e., MAC SDU) from the MAC PDU.

[0122] In another example, if UE 102 is in Fig.14 If at least one of the second MAC subheaders shown in the figure identifies a MAC subheader, the UE 102 identifies or determines a corresponding CE or MAC SDU included in the MAC PDU and extracts the corresponding CE or MAC SDU from the MAC PDU. For example, the UE 102 can identify an LCID value in the MAC subheader indicating a CE, and the CE includes one or more of a C-RNTI, a TA command, a contention resolution ID, and / or a DL grant. The UE 102 then uses the format of the CE to extract the C-RNTI, the TA command, the contention resolution ID, and / or the DL grant. The DL grant may also be referred to as a DL allocation.

[0123] In addition to indicating a format for decoding a response message from a base station using RNTI or MAC PDU, the format may also be indicated based on the size of at least a portion of the response message, such as the size of the MAC PDU. Fig.19A A messaging diagram illustrating an example process for signaling to a user equipment the format of a response message for decoding from a base station using the size of a PDU. The UE 102 sends 1902A MsgA to the base station 104, including a random access preamble and a payload.

[0124] The base station 104 then attempts to decode 1904A the payload. If the base station 104 detects the preamble in MsgA but fails to decode the payload, the base station 104 generates a RAR instead of MsgB and a MAC PDU including the MAC subheader and the RAR. On the other hand, if the base station 104 detects the preamble in MsgA and successfully decodes the payload, the base station 104 generates a MAC PDU including the MAC subheader and MsgB.

[0125] To transmit the MAC PDU, the base station 104 generates 1910A an RNTI, a DCI scrambled with the RNTI, and a CRC of the DCI. The base station 104 also transmits an indication of the size of a portion of the response message (e.g., the MAC PDU) to the UE 102. For example, in some embodiments, the DCI may include an indication of the size of the MAC PDU. The base station 104 then transmits 1920A the DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The base station also transmits 1930A the MAC PDU to the UE 102 on the physical resources, transport blocks, or PDSCH indicated in the DCI.

[0126] The UE 102 then determines 1940A the size of the MAC PDU. For example, the UE 102 may obtain the size of the MAC PDU from the DCI. In another example, the UE 102 may obtain the size of the MAC PDU from a MAC subheader, such as from a length field of the MAC subheader. The UE 102 then compares the size of the MAC PDU to a size threshold.

[0127] Then, in a first example, if the size is less than a threshold size, the UE 102 decodes 1942A the MAC PDU according to the first format with RAR and no resolution. The UE 102 proceeds to provide 1950A additional information to the base station 104, such as the transmission of the payload / schedule in the four-step RACH process. In response, the base station 104 transmits 1952A contention resolution to the UE 102. In a second example, if the size is greater than or equal to the threshold size, the UE 102 decodes 1944A the MAC PDU using a format of a MAC PDU including MsgB (e.g., with resolved RAR).

[0128] Fig.19B shows that when the base station 104 cannot decode the payload from the UE 102 Fig.19A Detailed message passing diagram of the example process shown in . UE 102 sends 1902B MsgA to base station 104, including a random access preamble and a payload. Then, base station 104 attempts to decode 1904B the payload. Base station 104 detects the preamble in MsgA but fails to decode 1906B the payload. As a result, base station 104 generates 1910B RAR instead of MsgB, a MAC subheader of the RAR, and a MAC PDU having a first size less than a size threshold, wherein the MAC PDU includes the first MAC subheader and the RAR.

[0129] To transmit the MAC PDU, the base station 104 generates an RNTI, a DCI scrambled with the RNTI, and a CRC of the DCI. The base station 104 then transmits 1920B of the DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The base station 104 also transmits 1930B of the MAC PDU to the UE 102 on the physical resource, transport block, or PDSCH indicated in the DCI. In addition, the base station 104 transmits an indication of the size of the MAC PDU, such as an indication of a first size that is less than a threshold size. For example, in some embodiments, the DCI may include an indication of the size of the MAC PDU.

[0130] Then, UE 102 determines the size of 1940B MAC PDU. For example, UE 102 may obtain the size of MAC PDU from DCI. In another example, UE 102 may obtain the size of MAC PDU from MAC subheader (such as from the length field of MAC subheader). Then, UE 102 compares the size of MAC PDU with the size threshold. Then, UE 102 decodes MAC PDU using the format indicated based on the size of MAC PDU. More specifically, because the size of MAC PDU is the first size less than the size threshold, UE 102 decodes 1942B MAC PDU using the format of MAC PDU including RAR without resolution. Then, UE 102 continues to provide 1950B additional information to base station 104, such as transmission of payload / schedule in four-step RACH process. In response, base station 104 transmits 1952B contention resolution to UE 102.

[0131] Fig.19C shows when base station 104 successfully decodes the payload from UE 102 Fig.19A Detailed message passing diagram of the example process shown in . UE 102 sends 1902C MsgA to base station 104, including a random access preamble and a payload. Then, base station 104 detects the preamble in MsgA and successfully decodes 1904C the payload. As a result, base station 104 generates a MAC PDU including MsgB. In some embodiments, base station 104 may generate 1910C a MAC PDU having a second size greater than or equal to a size threshold, wherein the MAC PDU includes a MAC subheader and MsgB.

[0132] To transmit the MAC PDU, the base station 104 generates an RNTI, a DCI scrambled with the RNTI, and a CRC for the DCI. The base station 104 then transmits 1920C the DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The base station 104 also transmits 1930C the MAC PDU to the UE 102 on the physical resource, transport block, or PDSCH indicated in the DCI. In addition, the base station 104 transmits an indication of the size of the MAC PDU, such as an indication of a second size greater than or equal to a threshold size. For example, in some embodiments, the DCI may include an indication of the size of the MAC PDU.

[0133] Then, the UE 102 determines the size of the 1940C MAC PDU. For example, the UE 102 may obtain the size of the MAC PDU from the DCI. In another example, the UE 102 may obtain the size of the MAC PDU from the MAC subheader (such as from the length field of the MAC subheader). Then, the UE 102 compares the size of the MAC PDU with a size threshold. Then, the UE 102 decodes the MAC PDU using a format based on the size indication of the MAC PDU. More specifically, because the size of the MAC PDU is a second size greater than or equal to the size threshold, the UE 102 decodes the 1944C MAC PDU using a format including a MAC PDU with an RAR and resolved MsgB.

[0134] In still other embodiments, the format may be indicated by a DCI element included in the response message. Fig. 20A A messaging diagram illustrating an example process for signaling to a user equipment the format of a response message to decode from a base station using a DCI element. UE 102 sends 2002A MsgA to base station 104, including a random access preamble and a payload.

[0135] The base station 104 then attempts to decode 2004A the payload. If the base station 104 detects the preamble in MsgA but fails to decode the payload, the base station 104 generates a RAR instead of MsgB and a MAC PDU including a MAC subheader and the RAR. To transmit the MAC PDU, the base station 104 generates 2010A an RNTI, a first DCI scrambled with the RNTI, and a CRC of the first DCI. The base station 104 then transmits 2020A the first DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The first DCI can be a first indicator of the format of the response message. The base station 104 also transmits 2030A a MAC PDU to the UE 102 on the physical resources, transport blocks, or PDSCH indicated in the first DCI.

[0136] On the other hand, if the base station 104 detects the preamble in MsgA and successfully decodes the payload, the base station 104 generates a MAC PDU including a MAC subheader and MsgB. In order to transmit the MAC PDU, the base station 104 generates 2010A RNTI, a second DCI different from the first DCI scrambled with the RNTI, and a CRC of the first DCI. Then, the base station 104 transmits 2020A the second DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The second DCI can be a second indicator of the format of the response message. The base station also transmits 2020A MAC PDU to the UE 102 on the physical resources, transport blocks, or PDSCH indicated in the second DCI.

[0137] In some embodiments, the first DCI may indicate a first physical radio resource dedicated to transmitting a first MAC PDU (or RAR). The second DCI may indicate a second physical radio resource dedicated to transmitting a second PDU (or MsgB). In other embodiments, the first DCI has a field indicating that the MAC PDU includes a RAR. The second DCI has a field indicating that the second MAC PDU includes an MsgB. In addition, in some embodiments, the first DCI and the second DCI may have different DCI formats. For example, the first DCI may follow the first DCI format and the second DCI may follow the second DCI format. The format of the DCI may indicate the format of the decoded MAC PDU. If the first DCI format indicates that the MAC PDU adopts a first format with RAR and the second DCI format indicates that the MAC PDU adopts a second format with MsgB, the first DCI and the second DCI may not need to indicate the corresponding fields of RAR and MsgB. In other embodiments, the first DCI and the second DCI have the same DCI format, and the DCI includes a field indicating the format for decoding the MAC PDU.

[0138] In any case, the UE 102 then identifies 2040A whether the DCI in the response message is the first DCI or the second DCI to identify the format for decoding the MAC PDU. The UE 102 then decodes the MAC PDU using the format indicated by the first DCI or the second DCI. More specifically, in the first instance, if the DCI is the first DCI, the UE 102 decodes 2042A the MAC PDU using the format of the MAC PDU including the RAR without resolution. The UE 102 then proceeds to provide 2050A additional information to the base station 104, such as the transmission of the payload / schedule in the four-step RACH process. In response, the base station 104 transmits 2052A contention resolution to the UE 102. In the second instance, if the DCI is the second DCI, the UE 102 decodes 2044A the MAC PDU using the format of the MAC PDU including MsgB (e.g., with resolved RAR).

[0139] Fig. 20B shows that when the base station 104 cannot decode the payload from the UE 102 Fig. 20A Detailed message transfer diagram of the example process shown in FIG. UE 102 sends 2002B MsgA to base station 104, including a random access preamble and a payload. Base station 104 then attempts to decode 2004B payload. Base station 104 detects the preamble in MsgA but fails to decode 2006B payload. As a result, base station 104 generates a RAR instead of MsgB, a MAC subheader for the RAR, and a MAC PDU including the MAC subheader and the RAR.

[0140] To transmit the MAC PDU, the base station 104 generates 2010B the RNTI, the first DCI scrambled with the RNTI, and the CRC of the DCI. The base station 104 then transmits 2020B the first DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The base station 104 also transmits 2030B the MAC PDU to the UE 102 on the physical resource, transport block, or PDSCH indicated in the DCI. The UE 102 then identifies 2040B whether the DCI in the response message includes the first DCI or the second DCI. The first and second DCIs may include different fields, have different field values, or may be in different formats.

[0141] The UE 102 then decodes the MAC PDU using the format indicated by the DCI. More specifically, because the DCI is the first DCI, the UE 102 decodes 2042B the MAC PDU using the format of the MAC PDU including the RAR without resolution. The UE 102 then proceeds to provide 2050B additional information to the base station 104, such as the transmission of the payload / schedule in the four-step RACH process. In response, the base station 104 transmits 2052B contention resolution to the UE 102.

[0142] Fig. 20C shows when base station 104 successfully decodes the payload from UE 102 Fig. 20A Detailed message transfer diagram of the example process shown in . UE 102 sends 2002C MsgA to base station 104, including a random access preamble and a payload. Then, base station 104 detects the preamble in MsgA and successfully decodes 2004C payload. As a result, base station 104 generates a MAC PDU including MsgB. In some embodiments, base station 104 can generate a MAC PDU including a MAC subheader and MsgB.

[0143] To transmit the MAC PDU, the base station 104 generates 2010C the RNTI, the second DCI scrambled with the RNTI, and the CRC of the second DCI. The base station 104 then transmits 2020C the second DCI scrambled with the RNTI and the CRC to the UE 102 on the PDCCH. The base station 104 also transmits 2040C the MAC PDU to the UE 102 on the physical resource, transport block, or PDSCH indicated in the DCI. The UE 102 then identifies 2044C whether the DCI in the response message includes the first DCI or the second DCI. The first and second DCIs may include different fields, have different field values, or may be in different formats.

[0144] Then, the UE 102 decodes the MAC PDU using the format indicated by the identified DCI. More specifically, because the DCI is the second DCI, the UE 102 decodes 2064 the MAC PDU using the format including the MAC PDU with RAR and resolved MsgB.

[0145] refer to Fig.21 The method 2100 may be implemented in the processing hardware of the base station using hardware, firmware, software, or any suitable combination of hardware, firmware, and software. For convenience, the following discussion will be exemplarily made with reference to the base station 104. Fig.21 , wherein one or more of modules 132 - 138 may implement method 2100 .

[0146] Method 2100 begins at block 2102, where base station 104 receives a request from UE 102 to access a communication channel. The request may be a MsgA having a random access preamble and a payload. As a more specific example, MsgA may be associated with Figure 4A Transmission 402A, Figure 4B Transmission 402B, Figure 4C Transmission 402C, Fig. 8A Transmission 802A, Figure 8B Transmission 802B, Figure 8C Transmission 802C, Fig.19A Transmission 1902A, Fig.19B Transmission 1902B, Fig.19C Transmission 1902C, Fig. 20A Transmission 2002A, Fig. 20B Transmission 2002B or Fig. 20C The transmission 2002C is associated.

[0147] At block 2104, the base station 104 attempts to decode the payload. In the above example, the base station 104 attempts to decode the payload. Figure 4A Step 404A, Figure 4B Step 404B, Figure 4C Step 404C, Fig. 8A Step 804A, Figure 8B Step 804B, Figure 8C Step 804C, Fig.19A Step 1904A, Fig.19B Step 1904B, Fig.19C Step 1904C, Fig. 20A Step 2004A, Fig. 20B Step 2004B or Fig. 20C Step 2004C decodes the payload.

[0148] The base station 104 then selects a format of a response message to send to the UE 102 based on whether the payload is successfully decoded. More specifically, if the base station 104 detects a preamble in MsgA but fails to decode the payload, the base station 104 generates a response message having a first format that includes a RAR instead of MsgB, a MAC subheader of the RAR, and a MAC PDU including the MAC subheader and the RAR. The base station 104 also generates an RNTI, a DCI scrambled with the RNTI, and a CRC of the DCI. The base station 104 then transmits a response message to the UE 102 in the first format with the RAR (block 2108). As a more specific example, the response message in the first format with the RAR may be transmitted with the UE 102 in the first format with the RAR. Figure 4B Transmission 420B, 430B, Figure 8B Transmission 830B, Fig.19B Transmission 1920B, 1930B or Fig. 20B The transmission 2020B and 2030B are associated.

[0149] The response message may include a DCI scrambled with the RNTI in the PDCCH and a CRC of the DCI and a MAC PDU in the PDSCH. The response message may also include an indication of the format of the response message, which UE 102 uses to decode the response message according to the indicated format. For example, the format of the response message may be indicated in the RNTI scrambled with the DCI. If the RNTI is a first RNTI, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts a first format with RAR. If the RNTI is a second RNTI, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts a second format with MsgB.

[0150] In another example, the format of the response message may be indicated in the MAC PDU, such as in a MAC subheader. If the MAC PDU includes a first MAC subheader, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts a first format with RAR. If the MAC PDU includes a second MAC subheader, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts a second format with MsgB.

[0151] In yet another example, the format of the response message may be indicated by the size of a portion of the response message, such as the size of a MAC PDU. In some implementations, the DCI includes an indication of the size of the MAC PDU. If the size of the MAC PDU is less than a threshold size, the UE 102 may determine that the response message, more specifically, the MAC PDU is in a first format with RAR. If the size of the MAC PDU is greater than or equal to a threshold size, the UE 102 may determine that the response message, more specifically, the MAC PDU is in a second format with MsgB.

[0152] In another example, the format of the response message may be indicated in the DCI. If the DCI is the first DCI, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts the first format with RAR. If the DCI is the second DCI, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts the second format with MsgB.

[0153] In any case, at block 2110, the base station receives an additional message from the UE 102, including a payload / scheduled transmission. As a more specific example, the additional message from the UE 102 may be associated with Figure 4A Transmission 450A, Figure 4B Transmission 450B, Fig. 8A Transmission 850A, Figure 8B Transmission 850B, Fig.19A Transmission 1950A, Fig.19B Transmission 1950B, Fig. 20A TRANSMISSION 2050A or Fig. 20B Transmission 2050B associated.

[0154] The base station then transmits an additional response message including the solution to UE 102 (block 2112). As a more specific example, the additional response message from base station 104 may be associated with Figure 4A Transmission 452A, Figure 4B Transmission 452B, Fig. 8A Transmission 852A, Figure 8B Transmission 852B, Fig.19A Transmission 1952A, Fig.19B Transmission 1952B, Fig. 20A TRANSFER 2052A or Fig. 20B Transmission 2052B associated.

[0155] On the other hand, if the base station 104 detects the preamble in MsgA and successfully decodes the payload, the base station 104 generates a response message in a second format different from the first format, wherein the MAC PDU includes MsgB. The base station 104 also generates an RNTI, a DCI scrambled with the RNTI, and a CRC of the DCI. The base station 104 then transmits the response message to the UE 102 in the second format with MsgB (block 2114). As a more specific example, the response message in the second format with MsgB may be Figure 4C Transmission 420C, 430C, Figure 8C Transmission 830C, Fig.19C Transmission 1920C, 1930C or Fig. 20C The transmission of 2020C and 2030C is associated.

[0156] The response message may include the DCI and the CRC of the DCI scrambled with the RNTI in the PDCCH and the MAC PDU in the PDSCH. The response message may also include an indication of the format of the response message, which the UE 102 uses to decode the response message according to the indicated format.

[0157] refer to Fig. 22 The method 2200 may be implemented in the processing hardware of the UE using hardware, firmware, software, or any suitable combination of hardware, firmware, and software. For convenience, the following discussion will be exemplarily made with reference to UE 102. Fig. 22 , wherein one or more of modules 122 - 126 may implement method 2200 .

[0158] Method 2200 begins at block 2202, where UE 102 transmits a request to base station 104 to access a communication channel. The request may be a MsgA having a random access preamble and a payload. As a more specific example, MsgA may be associated with Figure 4A Transmission 402A, Figure 4B Transmission 402B, Figure 4C Transmission 402C, Fig. 8A Transmission 802A, Figure 8B Transmission 802B, Figure 8C Transmission 802C, Fig.19A Transmission 1902A, Fig.19B Transmission 1902B, Fig.19C Transmission 1902C, Fig. 20A Transmission 2002A, Fig. 20B Transmission 2002B or Fig. 20C The transmission 2002C is associated.

[0159] At box 2204, UE 102 receives a response message from the base station. The response message may include a DCI scrambled with an RNTI and a CRC of the DCI, and a MAC PDU. The DCI scrambled with the RNTI may be transmitted in the PDCCH, and the MAC PDU may be transmitted in the PDSCH. In addition, the response message may include an indication of the format of the response message, or more specifically, an indication of the format of the MAC PDU included in the response message. The format of the MAC PDU may depend on whether the payload is successfully decoded by the base station 104. For example, when the payload is not successfully decoded by the base station 104, the MAC PDU may adopt a first format with RAR. On the other hand, when the payload is successfully decoded by the base station 104, the MAC PDU may adopt a second format with MsgB (e.g., RAR and resolution). As a more specific example, the response message in the first format with RAR may be transmitted with Figure 4B Transmission 420B, 430B, Figure 8B Transmission 830B, Fig.19B Transmission 1920B, 1930B or Fig. 20B The response message having the second format of MsgB can be associated with Figure 4C Transmission 420C, 430C, Figure 8C Transmission 830C, Fig.19C Transmission 1920C, 1930C or Fig. 20C The transmission of 2020C and 2030C is associated.

[0160] Then, at block 2206, UE 102 analyzes the response message to determine the format of the response message. Figure 4A Step 440A, Figure 4B Step 440B, Figure 4C Step 440C, Fig. 8A Step 840A, Figure 8B Step 840B, Figure 8C Step 840C, Fig.19A Step 1940A, Fig.19B Step 1940B, Fig.19C Step 1940C, Fig. 20A Step 2040A, Fig. 20B Step 2040B or Fig. 20C Step 2040C determines the format of the response message.

[0161] The format of the response message may be indicated in the RNTI scrambled with the DCI. If the RNTI is the first RNTI, the UE 102 may determine that the response message, more specifically, the MAC PDU, adopts the first format with the RAR. If the RNTI is the second RNTI, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts the second format with the MsgB.

[0162] In another example, the format of the response message may be indicated in the MAC PDU, such as in a MAC subheader. If the MAC PDU includes a first MAC subheader, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts a first format with RAR. If the MAC PDU includes a second MAC subheader, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts a second format with MsgB.

[0163] In yet another example, the format of the response message may be indicated by the size of a portion of the response message, such as the size of a MAC PDU. In some implementations, the DCI includes an indication of the size of the MAC PDU. If the size of the MAC PDU is less than a threshold size, the UE 102 may determine that the response message, more specifically, the MAC PDU is in a first format with RAR. If the size of the MAC PDU is greater than or equal to a threshold size, the UE 102 may determine that the response message, more specifically, the MAC PDU is in a second format with MsgB.

[0164] In another example, the format of the response message may be indicated in the DCI. If the DCI is the first DCI, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts the first format with RAR. If the DCI is the second DCI, the UE 102 may determine that the response message, more specifically, the MAC PDU adopts the second format with MsgB.

[0165] If the UE 102 determines that the response message is in the first format with RAR, then at block 2210, the UE 102 decodes the MAC PDU included in the response message according to the first format. Figure 4B Step 448B, Figure 8B Step 842B, Fig.19B Step 1942B or Fig. 20B Step 2042B decodes the MAC PDU included in the response message according to the first format.

[0166] The UE 102 then transmits an additional message including the payload / scheduled transmission to the base station 104 (block 2212). As a more specific example, the additional message from the UE 102 may be associated with Figure 4A Transmission 450A, Figure 4B Transmission 450B, Fig. 8A Transmission 850A, Figure 8B Transmission 850B, Fig.19A Transmission 1950A, Fig.19B Transmission 1950B, Fig. 20A TRANSMISSION 2050A or Fig. 20B UE 102 then receives an additional response message including the solution from the base station (block 2214). As a more specific example, the additional response message from base station 104 may be associated with Figure 4A Transmission 452A, Figure 4B Transmission 452B, Fig. 8A Transmission 852A, Figure 8B Transmission 852B, Fig.19A Transmission 1952A, Fig.19B Transmission 1952B, Fig. 20A TRANSFER 2052A or Fig. 20B Transmission 2052B associated.

[0167] On the other hand, if UE 102 determines that the response message adopts the second format with MsgB including the indication of UL grant, then at block 2216, UE 102 decodes the MAC PDU included in the response message according to the second format. Figure 4C Step 444C, Figure 8C Step 844C, Fig.19C Step 1944C or Fig. 20C Step 2064 decodes the MAC PDU included in the response message according to the second format.

[0168] Embodiments of the technology described in this disclosure may include any number of the following aspects, either alone or in combination:

[0169] 1. A method for authorizing access to a communication channel in a base station, the method comprising: receiving a request for access to a communication channel from a user device through processing hardware at the base station, the request comprising a random access preamble and a payload; attempting to decode the payload through the processing hardware; selecting a format of a response message through the processing hardware based on whether the payload is successfully decoded; and transmitting a response message to the user device through the processing hardware, including providing an indication of the format of the response message to the user device.

[0170] 2. A method according to aspect 1, wherein providing an indication of the format includes: in a first instance, when the payload is not successfully decoded, applying a first identifier of the user device to the response message; and in a second instance, when the payload is successfully decoded, applying a second identifier of the user device to the response message.

[0171] 3. A method according to any one of the preceding aspects, wherein: in a first instance, the method further comprises: receiving an additional message including a payload from a user device by processing hardware; and transmitting an additional response message to the user device by processing hardware; and in a second instance, transmitting the response message comprises transmitting a response message including an indication of an uplink authorization to the user device by processing hardware.

[0172] 5. A method according to any one of the preceding aspects, wherein: scrambling the DCI element with a first identifier includes scrambling a cyclic redundancy check (CRC) of the DCI element with the first identifier; and scrambling the DCI element with a second identifier includes scrambling the CRC of the DCI element with the second identifier.

[0173] 6. A method according to any one of the preceding aspects, wherein: applying the first identifier in the first instance comprises applying a first Radio Network Temporary Identifier (RNTI) of the user equipment to the response message when the data is not successfully decoded.

[0174] 7. A method according to any one of the preceding aspects, wherein: applying the second identifier in the second instance comprises applying a second RNTI of the user equipment to the response message when the payload is successfully decoded.

[0175] 8. A method according to any one of the preceding aspects, wherein: applying a first identifier in a first instance includes applying a first identifier in a first format indicating a response message, the first format having a random access response; and applying a second identifier in a second instance includes applying a second identifier in a second format indicating a response message, the second format having a random access response and a resolution.

[0176] 9. A method according to any one of the preceding aspects, wherein a random access response in a first format and a random access response and a resolution in a second format are included in a medium access control (MAC) layer protocol data unit (PDU), and further comprises: transmitting a DCI element encrypted with a first or second identifier to a user equipment on a physical downlink control channel (PDCCH) through processing hardware; and transmitting the MAC PDU to the user equipment on a physical data shared channel (PDSCH) through processing hardware.

[0177] 10. A method according to any one of the preceding aspects, wherein the request to access the communication channel is a random access channel (RACH) communication, and wherein the first RNTI is associated with a physical random access channel (PRACH) over which the RACH communication is transmitted from the user equipment.

[0178] 11. A method according to any one of the preceding aspects, wherein the first RNTI = 1 + s_id + 14 × t_id + 14 × 80 × f_id + 14 × 80 × 8 × ul_carrier_id, wherein: s_id is the index of the first orthogonal frequency division multiplexing (OFDM) symbol of PRACH, t_id is the index of the first time slot of PRACH in the system frame, f_id is the index of the first part of PRACH in the frequency domain, and ul_carrier_id is the uplink carrier used to transmit RACH communication.

[0179] 12. A method according to any one of the preceding aspects, wherein providing an indication of a format comprises: transmitting, via processing hardware, a response message having a protocol data unit (PDU) to a user device, the protocol data unit comprising an indicator of the format of the response message to the user device.

[0180] 13. A method according to any one of the preceding aspects, wherein transmitting a response message having a PDU with an indicator including a format of the response message comprises: in a first instance, when the payload is not successfully decoded, transmitting the response message having the PDU including a first indicator to a user device through processing hardware; and in a second instance, when the payload is successfully decoded, transmitting the response message having the PDU including a second indicator to the user device through processing hardware.

[0181] 14. A method according to any of the preceding aspects, wherein providing an indication of a format comprises: transmitting, by processing hardware, an indication of a size of a portion of a response message to a user equipment.

[0182] 15. A method according to any one of the preceding aspects, wherein the indication of the size of a portion of the transmission response message comprises: in a first instance, when the payload is not successfully decoded, transmitting an indication of a first size less than a threshold size to a user device through processing hardware; and in a second instance, when the payload is successfully decoded, transmitting an indication of a second size greater than or equal to the threshold size to the user device through processing hardware.

[0183] 16. A method according to any one of the preceding aspects, wherein the indication of the size of a portion of a transmitted response message comprises transmitting, via processing hardware, a response message comprising a downlink control information (DCI) element to a user equipment, the DCI element comprising an indication of the size of a protocol data unit (PDU) included in the response message.

[0184] 17. A method according to any one of the preceding aspects, wherein providing an indication of a format comprises transmitting, via processing hardware, a response message having a downlink control information (DCI) element to a user equipment, the DCI element comprising an indicator of the format of the response message to the user equipment.

[0185] 18. A method according to any one of the aforementioned aspects, wherein transmitting a response message having a DCI element including an indicator of a format of the response message includes: in a first instance, when a payload is not successfully decoded, transmitting a response message having a DCI element including a first indicator to a user device through processing hardware; and in a second instance, when the payload is successfully decoded, transmitting a response message having a DCI element including a second indicator to the user device through processing hardware.

[0186] 19. A method for requesting access to a communication channel in a user device, the method comprising: transmitting a request for access to a communication channel to a base station through processing hardware at the user device, the request including a random access preamble code and a payload; receiving a response message to the request from the base station through the processing hardware, the response message indicating a format of the response message based on whether the payload is successfully decoded by the base station; determining the format of the response message through the processing hardware; and decoding a portion of the response message according to the determined format through the processing hardware.

[0187] 20. A method according to aspect 19, wherein determining the format of a response message comprises: in a first instance, determining that the response message adopts a first format based on an indication of the first format included in the response message; decoding the portion of the response message according to the first format by processing hardware; transmitting an additional message including a payload to a base station by processing hardware; and receiving an additional response message from the base station by processing hardware; and in a second instance, determining that the response message adopts a second format based on an indication of the second format included in the response message; and decoding the portion of the response message according to the second format by processing hardware, wherein receiving the response message comprises receiving a response message including an indication of an uplink authorization from the base station by processing hardware.

[0188] 21. The method according to any one of aspects 19 or 20, wherein decoding a portion of the response message comprises decoding a protocol data unit (PDU) according to the determined format by processing hardware.

[0189] 22. The method according to any one of aspects 19-21, wherein determining the format of the response message comprises: in a first instance, obtaining a first identifier of the user equipment from the response message; and in a second instance, obtaining a second identifier of the user equipment from the response message.

[0190] 23. A method according to any one of aspects 19-22, wherein determining the format of the response message includes: obtaining a first identifier of the user equipment; attempting to decode a downlink control information (DCI) element in the response message using the first identifier; and in response to determining that the DCI element is successfully decoded, determining that the first identifier indicates that the response message adopts a first format.

[0191] 24. A method according to any one of aspects 19-23, wherein determining the format of the response message further includes: in response to determining that the DCI element is not successfully decoded, obtaining a second identifier of the user equipment; attempting to decode the DCI element in the response message using the second identifier; and in response to determining that the DCI element is successfully decoded, determining that the second identifier indicates that the response message adopts a second format.

[0192] 25. A method according to any one of aspects 19-24, wherein: obtaining a first identifier of the user equipment comprises obtaining a first radio network temporary identifier (RNTI) of the user equipment from a response message; and obtaining a second identifier of the user equipment comprises obtaining a second RNTI of the user equipment from the response message.

[0193] 26. A method according to any one of aspects 19-25, wherein transmitting a request for access to a communication channel comprises transmitting a random access channel (RACH) communication to a base station through processing hardware at a user equipment, and wherein obtaining a first RNTI of the user equipment from a response message comprises determining the first RNTI based on characteristics of a physical random access channel (PRACH) over which the RACH communication is transmitted from the user equipment.

[0194] 27. A method according to any one of aspects 19-26, wherein obtaining the second RNTI of the user equipment from the response message includes obtaining the second RNTI from a payload of a RACH communication transmitted from the user equipment, or determining the second RNTI based on other characteristics of a physical random access channel (PRACH) for transmitting the RACH communication from the user equipment.

[0195] 28. A method according to any one of aspects 19-27, wherein the first RNTI = 1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id, wherein: s_id is the index of the first orthogonal frequency division multiplexing (OFDM) symbol of PRACH, t_id is the index of the first time slot of PRACH in the system frame, f_id is the index of the first part of PRACH in the frequency domain, and ul_carrier_id is the uplink carrier used to transmit RACH communication.

[0196] 29. The method according to any one of aspects 19-28, wherein determining the format of the response message comprises: obtaining an indicator of the format of the response message from a protocol data unit (PDU) in the response message.

[0197] 30. A method according to any one of aspects 19-29, wherein determining the format of the response message includes: obtaining an indication of the size of a portion of the response message; in a first instance, in response to determining that the size is less than a threshold size, determining that the response message adopts a first format; and in a second example, in response to determining that the size is greater than or equal to a threshold size, determining that the response message adopts a second format.

[0198] 31. A method according to any one of aspects 19-30, wherein obtaining an indication of the size of a portion of the response message includes obtaining a downlink control information (DCI) element in the response message, the DCI element including an indication of the size of a protocol data unit (PDU) included in the response message.

[0199] 32. The method of any one of aspects 19-31, wherein determining the format of the response message comprises obtaining an indicator of the format of the response message from a downlink control information (DCI) element in the response message.

[0200] 33. A method for authorizing access to a communication channel in a base station, the method comprising: receiving a request for access to a communication channel from a user equipment through processing hardware at the base station, the request comprising a random access preamble and a payload; attempting to decode the payload through the processing hardware; selecting a format of a response message through the processing hardware based on whether the payload is successfully decoded; and transmitting a response message to the user equipment through the processing hardware, comprising providing an indication of the format of the response message to the user equipment through at least one of the following: (i) in a first instance, applying a first identifier of the user equipment to the response message when the payload is not successfully decoded, and in a second instance, applying a second identifier of the user equipment to the response message when the payload is successfully decoded, (ii) transmitting an indication of the size of a portion of the response message, or (iii) transmitting a response message with downlink control information (DCI) to the user equipment, the downlink control information comprising an indicator of the format of the response message.

[0201] 34. A method according to aspect 33, wherein applying the first identifier in the first instance comprises applying a first Radio Network Temporary Identifier (RNTI) of the user equipment to the response message.

[0202] 35. The method according to any one of aspects 33 or 34, wherein applying the second identifier in the second instance comprises: applying the second RNTI of the user equipment to the response message.

[0203] 36. A method according to any of aspects 33-35, wherein the request to access the communication channel is a random access channel (RACH) communication, and wherein the first RNTI is associated with a physical random access channel (PRACH) over which the RACH communication is transmitted from the user equipment.

[0204] 37. A method according to any one of aspects 33-36, wherein: applying the first identifier in the first instance includes applying the first identifier in a first format indicating a response message, the first format having a random access response; and applying the second identifier in the second instance includes applying the second identifier in a second format indicating a response message, the second format having a random access response and a resolution.

[0205] 38. A method according to any one of aspects 33-37, wherein the random access response in the first format and the random access response and resolution in the second format are included in a medium access control (MAC) layer protocol data unit (PDU), and also includes: transmitting a DCI element scrambled with a first or second identifier to a user equipment on a physical downlink control channel (PDCCH) through processing hardware; and transmitting the MAC PDU to the user equipment on a physical data shared channel (PDSCH) through processing hardware.

[0206] 39. A method according to any of aspects 33-38, wherein the indication of the size of a portion of the transmission response message includes: in a third instance, when the payload is not successfully decoded, transmitting an indication of a first size less than a threshold size to the user device through processing hardware; and in a fourth instance, when the payload is successfully decoded, transmitting an indication of a second size greater than or equal to the threshold size to the user device through processing hardware.

[0207] 40. A method according to any of aspects 33-39, wherein transmitting an indication of the size of a portion of the response message includes transmitting, via processing hardware, a response message including a DCI element to a user equipment, the DCI element including an indication of the size of a protocol data unit (PDU) included in the response message.

[0208] 41. A method according to any one of aspects 33-40, wherein transmitting a response message having a DCI element including an indicator of a format of the response message includes: in a fifth instance, when the payload is not successfully decoded, transmitting a response message having a DCI element including a first indicator to a user device through processing hardware; and in a sixth instance, when the payload is successfully decoded, transmitting a response message having a DCI element including a second indicator to a user device through processing hardware.

[0209] 42. A method according to any one of aspects 33-41, wherein: in the seventh instance, the method also includes: receiving an additional message including a payload from a user device through processing hardware; and sending an additional response message to the user device through processing hardware; and in the eighth instance, transmitting the response message includes transmitting a response message including an indication of an uplink authorization to the user device through processing hardware.

[0210] 43. A base station comprising processing hardware configured to implement the method of any of aspects 33-42.

[0211] 44. A method for requesting access to a communication channel in a user equipment, the method comprising: transmitting a request for access to a communication channel to a base station through processing hardware at the user equipment, the request comprising a random access preamble code and a payload; receiving a response message to the request from the base station through processing hardware, the response message indicating the format of the response message based on whether the payload is successfully decoded by the base station; determining the format of the response message through processing hardware based on at least one of: a first identifier of the user equipment and a second identifier of the user equipment applied to the response message, an indication of the size of a portion of the response message, or an indicator of the format of the response message from a downlink control information (DCI) element in the response message; and decoding a portion of the response message according to the determined format through processing hardware.

[0212] 45. A method according to aspect 44, wherein determining the format of the response message includes: in a first instance, determining that the response message adopts a first format based on an indication of the first format included in the response message; decoding the portion of the response message according to the first format by processing hardware; transmitting an additional message including a payload to a base station by processing hardware; and receiving the additional response message from the base station by processing hardware; and in a second instance, determining that the response message adopts a second format based on an indication of the second format included in the response message; and decoding the portion of the response message according to the second format by processing hardware, wherein receiving the response message includes receiving a response message including an indication of an uplink grant from the base station by processing hardware.

[0213] 46. ​​A method according to any one of Aspect 44 or Aspect 45, wherein determining the format of a response message based on a first identifier of a user device and a second identifier of the user device comprises: obtaining a first identifier of the user device; attempting to decode a DCI element in the response message using the first identifier; in a third instance, in response to determining that the DCI element is successfully decoded using the first identifier: determining that the first identifier indicates that the response message is in a first format; and in a fourth instance, in response to determining that the DCI element is not successfully decoded using the first identifier: obtaining a second identifier of the user device; attempting to decode the DCI element in the response message using the second identifier; and in response to determining that the DCI element is successfully decoded using the second identifier, determining that the second identifier indicates that the response message is in a second format.

[0214] 47. A method according to any one of aspects 44-46, wherein: obtaining a first identifier of the user equipment includes obtaining a first radio network temporary identifier (RNTI) of the user equipment from a response message; and obtaining a second identifier of the user equipment includes obtaining a second RNTI of the user equipment from the response message.

[0215] 48. A method according to any of aspects 44-47, wherein transmitting a request for access to a communication channel comprises transmitting a random access channel (RACH) communication to a base station via processing hardware at a user equipment, and wherein obtaining a first RNTI of the user equipment from a response message comprises determining the first RNTI based on characteristics of a physical random access channel (PRACH) over which the RACH communication is transmitted from the user equipment.

[0216] 49. A method according to any one of aspects 44-48, wherein obtaining the second RNTI of the user equipment from the response message comprises obtaining the second RNTI from a payload of a RACH communication transmitted from the user equipment, or determining the second RNTI based on other characteristics of a PRACH over which the RACH communication is transmitted from the user equipment.

[0217] 50. A method according to any one of aspects 44-49, wherein determining the format of the response message based on an indication of the size of the portion of the response message comprises: obtaining an indication of the size of the portion of the response message; in a fifth instance, in response to determining that the size is less than a threshold size, determining that the response message adopts a first format; and in a sixth instance, in response to determining that the size is greater than or equal to a threshold size, determining that the response message adopts a second format.

[0218] 51. A method according to any of aspects 44-50, wherein obtaining the indication of the size of the part of the response message includes obtaining a DCI element in the response message, the DCI element including an indication of the size of a protocol data unit (PDU) included in the response message.

[0219] 52. A user equipment comprising processing hardware configured to implement the method of any of aspects 44-51.

[0220] The following additional considerations apply to the above discussion.

[0221] The user equipment (e.g., UE 102) in which the technology of the present disclosure can be implemented can be any suitable device capable of wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile game console, a point of sale (POS) terminal, a health monitoring device, a drone, a camera, a streaming media dongle or other personal media device, a wearable device such as a smart watch, a wireless hotspot, a femtocell, or a broadband router. In addition, in some cases, the user equipment can be embedded in an electronic system, such as a head unit or an advanced driver assistance system (ADAS) of a vehicle. Further, the user equipment can be operated as an Internet of Things (IoT) device or a mobile Internet device (MID). Depending on the type, the user equipment may include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0222] Certain embodiments are described in the present disclosure as including logic or multiple components or modules. A module can be a software module (e.g., code stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit that is capable of performing a specific operation and can be configured or arranged in a specific manner. A hardware module can include dedicated circuits or logic that are permanently configured (e.g., as a dedicated processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC)) to perform a specific operation. A hardware module may also include programmable logic or circuits (e.g., contained within a general-purpose processor or other programmable processor) that are temporarily configured by software to perform a specific operation. The decision to implement a hardware module in a dedicated and permanently configured circuit or in a temporarily configured circuit (e.g., configured by software) may be driven by cost and time considerations.

[0223] When implemented in software, the technology may be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software may be executed by one or more general-purpose processors or one or more special-purpose processors.

[0224] After reading this disclosure, those skilled in the art will appreciate further alternative structures and functional designs for processing the channel access process by the principles disclosed herein. Therefore, although specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the precise configurations and components disclosed herein. Various modifications, changes and variations that will be apparent to those of ordinary skill in the art may be made to the arrangement, operation and details of the methods and devices disclosed herein without departing from the spirit and scope defined by the appended claims.

Claims

1. A method for granting access to a communication channel in a base station, the method comprising: receiving, at the base station, from a user equipment, a request for access to the communication channel, the request comprising a random access preamble and a payload; attempting to decode said payload; In the first instance, when the data payload is not successfully decoded: generating a first response message, the first response message comprising a first protocol data unit (PDU) having a first subheader in a first subheader format, the first subheader format comprising an extension, a type and / or a random access preamble identifier field, the first subheader format indicating a four-step random access channel (RACH) procedure; and Transmitting the first response message to the user equipment; In the second example, when the data payload is successfully decoded: generating a second response message, the second response message comprising a second PDU having a second subheader having a second subheader format different from the first subheader format and including a reserved field, the second subheader format indicating a two-step RACH procedure; and Sending the second response message to the user equipment.

2. The method according to claim 1, wherein: In the first example, the method further includes: receiving an attach message including the payload from the user equipment; and sending an additional response message to the user equipment; and In the second example, sending the second response message includes sending a second response message including an indication of an uplink grant to the user equipment.

3. The method according to claim 1 or 2, wherein: Generating a first response message in the first instance includes: A first response message including a random access response RAR is generated as Msg2 in a four-step random access channel RACH procedure.

4. The method according to claim 1 or 2, wherein: Generating the second response message in the second instance includes: A second response message including the RAR and contention resolution is generated as MsgB in the two-step RACH procedure.

5. The method according to claim 1 or 2, further comprising: generating a radio network temporary identifier RNTI; Generate downlink control information DCI element; Generate a cyclic redundancy check CRC of the DCI element; and Sending the DCI and CRC scrambled with the RNTI to the user equipment on a physical downlink control channel PDCCH; and The first PDU or the second PDU is sent to the user equipment on a physical data shared channel PDSCH.

6. A base station comprising processing hardware configured to implement the method according to claim 1 or 2.

7. A method for requesting access to a communication channel in a user equipment, the method comprising: Sending, at the user equipment, a request to access a communication channel to a base station, the request comprising a random access preamble and a payload; receiving a response message to the request from the base station, the response message indicating a format of the response message based on whether the payload is successfully decoded by the base station; Determining a format of the response message based on a subheader format of a protocol data unit (PDU) included in the response message; wherein, in a case where the payload is successfully decoded by the base station, the subheader format comprises a first subheader format, the first subheader format comprising an extension, a type and / or a random access preamble identifier field and indicating a four-step random access channel RACH procedure, and in a case where the payload is not successfully decoded by the base station, the subheader format comprises a second subheader format, the second subheader format comprising a reserved field and indicating a two-step RACH procedure, wherein the first subheader format is different from the second subheader format; and A portion of the response message is decoded according to the determined format.

8. The method according to claim 7, wherein: Determining the format of the response message includes: In the first instance, determining that the response message is in the first format based on a subheader in the response message including the first subheader format indicating that the payload was not successfully decoded; decoding the portion of the response message according to the first format; sending an attach message including the payload to the base station; and receiving an additional response message from the base station; and In the second example, determining that the response message is in the second format based on a subheader in the response message including the second subheader format indicating that the payload was successfully decoded; and decoding the portion of the response message according to the second format, Wherein, receiving the response message includes receiving a response message including an indication of an uplink grant from the base station.

9. The method according to claim 8, wherein: In the first example, decoding the portion of the response message includes decoding a random access response RAR in the response message according to a Msg2 format in a four-step random access channel RACH procedure; and The sending of the additional message includes sending the payload as Msg3 in the four-step RACH process.

10. The method according to claim 8, wherein: In the second example, decoding the response message includes decoding RAR and contention resolution in the response message according to a MsgB format in a two-step RACH procedure.

11. A user equipment comprising processing hardware configured to implement the method according to any one of claims 7-10.

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