Medium access control protocol data unit in a message 3 buffer

Apparatuses, methods, and systems are disclosed for using a medium access control protocol data unit in a message 3 buffer. One method includes, in response to a medium access control protocol data unit being in a message 3 buffer and receiving an uplink grant: obtaining the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicating to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtaining the medium access control protocol data unit from the multiplexing and assembly entity.

FIELD

The subject matter disclosed herein relates generally to wireless communications and more particularly relates to a medium access control protocol data unit in a message 3 buffer.

BACKGROUND

The following abbreviations are herewith defined, at least some of which are referred to within the following description: Third Generation Partnership Project (“3GPP”), 5thGeneration (“5G”), Positive-Acknowledgment (“ACK”), Aggregation Level (“AL”), Access and Mobility Management Function (“AMF”), Access Point (“AP”), Beam Failure Detection (“BFD”), Binary Phase Shift Keying (“BPSK”), Base Station (“BS”), Buffer Status Report (“BSR”), Bandwidth (“BW”), Bandwidth Part (“BWP”), Carrier Aggregation (“CA”), Contention-Based Random Access (“CBRA”), Clear Channel Assessment (“CCA”), Control Channel Element (“CCE”), Cyclic Delay Diversity (“CDD”), Code Division Multiple Access (“CDMA”), Control Element (“CE”), Contention-Free Random Access (“CFRA”), Closed-Loop (“CL”), Coordinated Multipoint (“CoMP”), Cyclic Prefix (“CP”), Cyclical Redundancy Check (“CRC”), Channel State Information (“CSI”), Channel State Information-Reference Signal (“CSI-RS”), Common Search Space (“CSS”), Control Resource Set (“CORESET”), Discrete Fourier Transform Spread (“DFTS”), Downlink Control Information (“DCI”), Downlink (“DL”), Demodulation Reference Signal (“DMRS”), Data Radio Bearer (“DRB”), Discontinuous Reception (“DRX”), Downlink Pilot Time Slot (“DwPTS”), Enhanced Clear Channel Assessment (“eCCA”), Enhanced Mobile Broadband (“eMBB”), Evolved Node B (“eNB”), Effective Isotropic Radiated Power (“EIRP”), European Telecommunications Standards Institute (“ETSI”), Frame Based Equipment (“FBE”), Frequency Division Duplex (“FDD”), Frequency Division Multiplexing (“FDM”), Frequency Division Multiple Access (“FDMA”), Frequency Division Orthogonal Cover Code (“FD-OCC”), 5G Node B or Next Generation Node B (“gNB”), General Packet Radio Services (“GPRS”), Guard Period (“GP”), Global System for Mobile Communications (“GSM”), Globally Unique Temporary UE Identifier (“GUTI”), Home AMF (“hAMF”), Hybrid Automatic Repeat Request (“HARQ”), Home Location Register (“HLR”), Handover (“HO”), Home PLMN (“HPLMN”), Home Subscriber Server (“HSS”), Identity or Identifier (“ID”), Information Element (“IE”), International Mobile Equipment Identity (“IMEI”), International Mobile Subscriber Identity (“IMSI”), International Mobile Telecommunications (“IMT”), Internet-of-Things (“IoT”), Layer 2 (“L2”), Licensed Assisted Access (“LAA”), Load Based Equipment (“LBE”), Listen-Before-Talk (“LBT”), Logical Channel (“LCH”), Logical Channel Prioritization (“LCP”), Log-Likelihood Ratio (“LLR”), Long Term Evolution (“LTE”), Multiple Access (“MA”), Medium Access Control (“MAC”), Multimedia Broadcast Multicast Services (“MBMS”), Modulation Coding Scheme (“MCS”), Master Information Block (“MIB”), Multiple Input Multiple Output (“MIMO”), Mobility Management (“MM”), Mobility Management Entity (“MME”), Mobile Network Operator (“MNO”), massive MTC (“mMTC”), Maximum Power Reduction (“MPR”), Machine Type Communication (“MTC”), Multi User Shared Access (“MUSA”), Non Access Stratum (“NAS”), Narrowband (“NB”), Negative-Acknowledgment (“NACK”) or (“NAK”), Network Entity (“NE”), Network Function (“NF”), Non-Orthogonal Multiple Access (“NOMA”), New Radio (“NR”), Network Repository Function (“NRF”), Network Slice Instance (“NSI”), Network Slice Selection Assistance Information (“NSSAI”), Network Slice Selection Function (“NSSF”), Network Slice Selection Policy (“NSSP”), Operation and Maintenance System (“OAM”), Orthogonal Frequency Division Multiplexing (“OFDM”), Open-Loop (“OL”), Other System Information (“OSI”), Power Angular Spectrum (“PAS”), Physical Broadcast Channel (“PBCH”), Power Control (“PC”), Primary Cell (“PCell”), Policy Control Function (“ ”PCF”), Physical Cell ID (“PCID”), Physical Downlink Control Channel (“PDCCH”), Packet Data Convergence Protocol (“PDCP”), Physical Downlink Shared Channel (“PDSCH”), Pattern Division Multiple Access (“PDMA”), Packet Data Unit (“PDU”), Physical Hybrid ARQ Indicator Channel (“PHICH”), Power Headroom (“PH”), Power Headroom Report (“PHR”), Physical Layer (“PHY”), Public Land Mobile Network (“PLMN”), Physical Random Access Channel (“PRACH”), Physical Resource Block (“PRB”), Primary Secondary Cell (“PSCell”), Physical Uplink Control Channel (“PUCCH”), Physical Uplink Shared Channel (“PUSCH”), Quasi Co-Located (“QCL”), Quality of Service (“QoS”), Quadrature Phase Shift Keying (“QPSK”), Registration Area (“RA”), Radio Access Network (“RAN”), Radio Access Technology (“RAT”), Random Access Procedure (“RACH”), Random Access Response (“RAR”), Resource Element Group (“REG”), Radio Link Control (“RLC”), RLC Acknowledged Mode (“RLC-AM”), RLC Unacknowledged Mode/Transparent Mode (“RLC-UM/TM”), Radio Link Monitoring (“RLM”), Radio Network Temporary Identifier (“RNTI”), Reference Signal (“RS”), Remaining Minimum System Information (“RMSI”), Radio Resource Control (“RRC”), Radio Resource Management (“RRM”), Resource Spread Multiple Access (“RSMA”), Reference Signal Received Power (“RSRP”), Round Trip Time (“RTT”), Receive (“RX”), Sparse Code Multiple Access (“SCMA”), Scheduling Request (“SR”), Sounding Reference Signal (“SRS”), Single Carrier Frequency Division Multiple Access (“SC-FDMA”), Secondary Cell (“SCell”), Shared Channel (“SCH”), Sub-carrier Spacing (“SCS”), Service Data Unit (“SDU”), System Information Block (“SIB”), SystemInformationBlockType1 (“SIB1”), SystemInformationBlockType2 (“SIB2”), Subscriber Identity/Identification Module (“SIM”), Signal-to-Interference-Plus-Noise Ratio (“SINR”), Service Level Agreement (“SLA”), Session Management Function (“SMF”), Special Cell (“SpCell”), Single Network Slice Selection Assistance Information (“S-NSSAI”), Signaling Radio Bearer (“SRB”), Shortened TTI (“sTTI”), Synchronization Signal (“SS”), Synchronization Signal Block (“SSB”), Supplementary Uplink (“SUL”), Subscriber Permanent Identifier (“SUPI”), Tracking Area (“TA”), TA Indicator (“TAI”), Transport Block (“TB”), Transport Block Size (“TBS”), Time-Division Duplex (“TDD”), Time Division Multiplex (“TDM”), Time Division Orthogonal Cover Code (“TD-OCC”), Transmission Power Control (“TPC”), Transmission Reception Point (“TRP”), Transmission Time Interval (“TTI”), Transmit (“TX”), Uplink Control Information (“UCI”), Unified Data Management Function (“UDM”), Unified Data Repository (“UDR”), User Entity/Equipment (Mobile Terminal) (“UE”), Uplink (“UL”), Universal Mobile Telecommunications System (“UMTS”), User Plane (“UP”), Uplink Pilot Time Slot (“UpPTS”), Ultra-reliability and Low-latency Communications (“URLLC”), UE Route Selection Policy (“URSP”), Visiting AMF (“vAMF”), Visiting NSSF (“vNSSF”), Visiting PLMN (“VPLMN”), and Worldwide Interoperability for Microwave Access (“WiMAX”).

In certain wireless communications networks, a RACH procedure may be used. In such networks, buffers may be used as part of the RACH procedure.

BRIEF SUMMARY

Methods for using a medium access control protocol data unit in a message 3 buffer are disclosed. Apparatuses and systems also perform the functions of the apparatus. One embodiment of a method includes, in response to a medium access control protocol data unit being in a message 3 buffer and receiving an uplink grant: obtaining the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicating to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtaining the medium access control protocol data unit from the multiplexing and assembly entity.

One apparatus for using a medium access control protocol data unit in a message 3 buffer includes a receiver and a processor that: in response to a medium access control protocol data unit being in a message 3 buffer and the receiver receiving an uplink grant: obtains the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicates to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtains the medium access control protocol data unit from the multiplexing and assembly entity.

DETAILED DESCRIPTION

FIG. 1depicts an embodiment of a wireless communication system100for using a medium access control protocol data unit in a message 3 buffer. In one embodiment, the wireless communication system100includes remote units102and network units104. Even though a specific number of remote units102and network units104are depicted inFIG. 1, one of skill in the art will recognize that any number of remote units102and network units104may be included in the wireless communication system100.

The network units104may be distributed over a geographic region. In certain embodiments, a network unit104may also be referred to as an access point, an access terminal, a base, a base station, a Node-B, an eNB, a gNB, a Home Node-B, a relay node, a device, a core network, an aerial server, a radio access node, an AP, NR, a network entity, an AMF, a UDM, a UDR, a UDM/UDR, a PCF, a RAN, an NSSF, or by any other terminology used in the art. The network units104are generally part of a radio access network that includes one or more controllers communicably coupled to one or more corresponding network units104. The radio access network is generally communicably coupled to one or more core networks, which may be coupled to other networks, like the Internet and public switched telephone networks, among other networks. These and other elements of radio access and core networks are not illustrated but are well known generally by those having ordinary skill in the art.

In one implementation, the wireless communication system100is compliant with NR protocols standardized in 3GPP, wherein the network unit104transmits using an OFDM modulation scheme on the DL and the remote units102transmit on the UL using a SC-FDMA scheme or an OFDM scheme. More generally, however, the wireless communication system100may implement some other open or proprietary communication protocol, for example, WiMAX, IEEE 802.11 variants, GSM, GPRS, UMTS, LTE variants, CDMA2000, Bluetooth®, ZigBee, Sigfoxx, among other protocols. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol.

In one embodiment, a remote unit102may, in response to a medium access control protocol data unit being in a message 3 buffer and receiving an uplink grant: obtain the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicate to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtain the medium access control protocol data unit from the multiplexing and assembly entity. Accordingly, the remote unit102may be used for using a medium access control protocol data unit in a message 3 buffer.

The processor202, in one embodiment, may include any known controller capable of executing computer-readable instructions and/or capable of performing logical operations. For example, the processor202may be a microcontroller, a microprocessor, a central processing unit (“CPU”), a graphics processing unit (“GPU”), an auxiliary processing unit, a field programmable gate array (“FPGA”), or similar programmable controller. In some embodiments, the processor202executes instructions stored in the memory204to perform the methods and routines described herein. In various embodiments, the processor202may: in response to a medium access control protocol data unit being in a message 3 buffer and a receiver receiving an uplink grant: obtain the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicate to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtain the medium access control protocol data unit from the multiplexing and assembly entity. The processor202is communicatively coupled to the memory204, the input device206, the display208, the transmitter210, and the receiver212.

The transmitter210is used to provide UL communication signals to the network unit104and the receiver212is used to receive DL communication signals from the network unit104, as described herein. Although only one transmitter210and one receiver212are illustrated, the remote unit102may have any suitable number of transmitters210and receivers212. The transmitter210and the receiver212may be any suitable type of transmitters and receivers. In one embodiment, the transmitter210and the receiver212may be part of a transceiver.

Although only one transmitter310and one receiver312are illustrated, the network unit104may have any suitable number of transmitters310and receivers312. The transmitter310and the receiver312may be any suitable type of transmitters and receivers. In one embodiment, the transmitter310and the receiver312may be part of a transceiver.

In some embodiments, a UE may end up switching between CFRA and CBRA based on a selected beam for each random access resource selection because a network may be expected to allocate CFRA resources only to a subset of beams in a cell. In such embodiments, this may happen (e.g., during HO) if the UE is configured with CFRA resources, but at the time of random access resource selection none of the SSBs having a configured CFRA resource are above a selection threshold. Moreover, in such embodiments the UE may fall back to CBRA resources where it is possible to select any SSB. If the CBRA fails contention resolution (e.g., if the selected SSB does not provide sufficient quality), the UE may perform a new random access resource selection that may lead to a successful SSB selection and CFRA. As may be appreciated, the switch from CBRA to CFRA may only be applicable to UEs in an RRC connected mode. Table 1 shows a random access procedure for resource selection, such as one that may be used for NR.

TABLE 1Random Access Resource SelectionThe MAC entity shall:1>if the Random Access procedure was initiated for beam failure recovery (as specified insubclause 5.17); and1>if the beamFailureRecoveryTimer (in subclause 5.17) is either running or not configured; and1>if the contention-free Random Access Resources for beam failure recovery request associatedwith any of the SSBs and/or CSI-RSs have been explicitly provided by RRC; and1>if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB amongst the SSBs incandidateBeamRSList or the CSI-RSs with CSI-RSRP above rsrp-ThresholdCSI-RS amongstthe CSI-RSs in candidateBeamRSList is available:2>select an SSB with SS-RSRP above rsrp-ThresholdSSB amongst theSSBs in candidateBeamRSList or a CSI-RS with CSI-RSRP aboversrp-ThresholdCSI-RS amongst the CSI-RSs in candidateBeamRSList;2>if CSI-RS is selected, and there is no ra-PreambleIndex associated with theselected CSI-RS:3>set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding tothe SSB in candidateBeamRSList which is quasi-collocated with theselected CSI-RS as specified in TS 38.214 [7].2>else:3>set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to theselected SSB or CSI-RS from the set of Random Access Preambles forbeam failure recovery request.1>else if the ra-PreambleIndex has been explicitly provided by either PDCCH or RRC; and1>if the ra-PreambleIndex is not 0b000000; and1>if contention-free Random Access Resource associated with SSBs or CSI-RSs have not beenexplicitly provided by RRC:2>set the PREAMBLE_INDEX to the signalled ra-PreambleIndex.1>else if the contention-free Random Access Resources associated with SSBs have been explicitlyprovided by RRC and at least one SSB with SS-RSRP above rsrp-ThresholdSSB amongst the associatedSSBs is available:2>select an SSB with SS-RSRP above rsrp-ThresholdSSB amongst the associatedSSBs;2>set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the selected SSB.1>else if the contention-free Random Access Resources associated with CSI-RSs have been explicitly providedby RRC and at least one CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the associated CSI-RSs is available:2>select a CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the associated CSI-RSs;2>set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the selected CSI-RS.1>else:2>if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB is available:3>select an SSB with SS-RSRP above rsrp-ThresholdSSB.2>else:3>select any SSB.2>if Msg3 has not yet been transmitted:3>if Random Access Preambles group B is configured:4>if the potential Msg3 size (UL data available for transmission plusMAC header and, where required, MAC CEs) is greater thanra-Msg3SizeGroupA and the pathloss is less than PCMAX (of the ServingCell performing the Random Access Procedure) -preambleReceivedTargetPower - msg3-DeltaPreamble -messagePowerOffsetGroupB; or4>if the Random Access procedure was initiated for the CCCH logical channel andthe CCCH SDU size plus MAC subheader is greater than ra-Msg3SizeGroupA:5>select the Random Access Preambles group B.4>else:5>select the Random Access Preambles group A.3>else:4>select the Random Access Preambles group A.2>else (i.e. Msg3 is being retransmitted):3>select the same group of Random Access Preambles as was used for theRandom Access Preamble transmission attempt corresponding to the firsttransmission of Msg3.2>if the association between Random Access Preambles and SSBs is configured:3>select a ra-PreambleIndex randomly with equal probability from the RandomAccess Preambles associated with the selected SSB and the selected Random AccessPreambles group.2>else:3>select a ra-PreambleIndex randomly with equal probability from the Random AccessPreambles within the selected Random Access Preambles group.2>set the PREAMBLE_INDEX to the selected ra-PreambleIndex.1>if an SSB is selected above and an association between PRACH occasions and SSBs is configured:2>determine the next available PRACH occasion from the PRACH occasions corresponding to the selectedSSB permitted by the restrictions given by the ra-ssb-OccasionMaskIndex if configured (the MAC entityshall select a PRACH occasion randomly with equal probability amongst the PRACH occasionsoccurring simultaneously but on different subcarriers, corresponding to the selected SSB; theMAC entity may take into account the possible occurrence of measurement gaps when determiningthe next available PRACH occasion corresponding to the selected SSB).1>else if a CSI-RS is selected above and an association between PRACH occasions and CSI-RSs is configured:2>determine the next available PRACH occasion from the PRACH occasions in ra-OccasionListcorresponding to the selected CSI-RS (the MAC entity shall select a PRACH occasion randomly withequal probability amongst the PRACH occasions occurring simultaneously but on different subcarriers,corresponding to the selected CSI-RS; the MAC entity may take into account the possible occurrence ofmeasurement gaps when determining the next available PRACH occasion corresponding to the selectedCSI-RS).1>else if Random Access procedure was initiated for beam failure recovery; and1>if a CSI-RS is selected above and there is no contention-free Random Access Resource associated with theselected CSI-RS:2>determine the next available PRACH occasion from the PRACH occasions, permitted by the restrictionsgiven by the ra-ssb-OccasionMaskIndex if configured, corresponding to the SSB incandidateBeamRSList which is quasi-collocated with the selected CSI-RS as specified in TS 38.214[7] (the MAC entity may take into account the possible occurrence of measurement gaps whendetermining the next available PRACH occasion corresponding to the SSB which is quasi-collactedwith the selected CSI-RS).1>else:2>determine the next available PRACH occasion (the MAC entity shall select a PRACH occasionrandomly with equal probability amongst the PRACH occasions occurring simultaneously but ondifferent subcarriers; the MAC entity may take into account the possible occurrence ofmeasurement gaps when determining the next available PRACH occasion).1>perform the Random Access Preamble transmission procedure (see subclause 5.1.3).

In certain embodiments, if a UE applies CBRA and then switches to CFRA, a Message 3 (e.g., Msg3) may have been generated and stored in a Message 3 buffer (e.g., Msg3 buffer). In some embodiments, a UE may transmit a TB stored in the Msg3 buffer also for a CFRA (e.g., uplink transmission allocated by a random access response message). In such embodiments, a HARQ buffer may be flushed if contention resolution fails and a MAC PDU transmitted in the Message 3 may be stored in the Msg3 buffer. Moreover, in such embodiments, if the random access procedure continues and a new RAR is received, because there is a MAC PDU stored in the Msg3 buffer irrespective of whether it is a CBRA or a CFRA, the UE may transmit a TB from the Msg3 buffer on the UL resources allocated by RAR.

If a grant is received in the new RAR, the UE may deliver the uplink grant and the associated HARQ information to a HARQ entity as described in Table 2.

TABLE 22>if the uplink grant was received in a Random Access Response; or2>if the uplink grant is part of a bundle of the configured uplink grant, and may be used for initialtransmission according to subclause 6.1.2.3 of TS 38.214 [7], and if no MAC PDU has been obtained for thisbundle:3>if there is a MAC PDU in the Msg3 buffer and the uplink grant was received in a RandomAccess Response:4>obtain the MAC PDU to transmit from the Msg3 buffer.3>else:4>obtain the MAC PDU to transmit from the Multiplexing and assembly entity, if any;3>if a MAC PDU to transmit has been obtained:4>deliver the MAC PDU and the uplink grant and the HARQ information of the TB tothe identified HARQ process;4>instruct the identified HARQ process to trigger a new transmission;

Accordingly, the MAC PDU from the Msg3 buffer may be obtained for transmission.

In various embodiments, if a UE receives a RAR successfully in response to a contention-free RACH preamble transmission, the UE may process an UL grant in the RAR and obtain a MAC PDU from a Msg3 buffer for a CBRA-to-CFRA switching case. However, because the CFRA procedure is successfully completed upon reception of the RAR, the UE may flush the HARQ process used for the transmission of a TB from the Msg3 buffer.

In some embodiments, a UE may upon reception of a RAR obtain a TB stored in a Msg3 buffer and store it in a HARQ buffer of HARQ process 0 and then subsequently flush the HARQ buffer of HARQ process 0 (e.g., because a RACH procedure was completed). Table 3 shows one embodiment of a random access response reception. Table 4 shows one embodiment of completion of a random access procedure.

TABLE 3Random Access Response ReceptionOnce the Random Access Preamble is transmitted and regardless of the possible occurrence of a measurement gap,the MAC entity shall:1>if the contention-free Random Access Preamble for beam failure recovery request was transmitted by theMAC entity:2>start the ra-ResponseWindow configured in BeamFailureRecoveryConfig at the first PDCCH occasion asspecified in TS 38.213 [6] from the end of the Random Access Preamble transmission;2>monitor the PDCCH of the SpCell for response to beam failure recovery request identified by the C-RNTIwhile ra-ResponseWindow is running.1>else:2>start the ra-ResponseWindow configured in RACH-ConfigCommon at the first PDCCH occasion asspecified in TS 38.213 [6] from the end of the Random Access Preamble transmission;2>monitor the PDCCH of the SpCell for Random Access Response(s) identified by the RA-RNTI while thera-ResponsedWindow is running.1>if notification of a reception of a PDCCH transmission is received from lower layers: and1>if PDCCH transmission is addressed to the C-RNTI; and1>if the contention-free Random Access Preamble for beam failure recovery request was transmitted by theMAC entity:2>consider the Random Access procedure successfully completed.1>else if a downlink assignment lias been received on the PDCCH for the RA-RNTI and the received TB issuccessfully decoded:2>if the Random Access Response contains a MAC subPDU with Backoff Indicator:3>set the PREAMBLE_BACKOFF to value of the BI field of the MAC subPDU using Table 7.2-1,multiplied with SCALING_FACTOR_BI.2>else:3>set the PREAMBLE_BACKOFF to 0 ms.2>if the Random Access Response contains a MAC subPDU with Random Access Preamble identifiercorresponding to the transmitted PREAMBLE_INDEX (see subclause 5.1.3):3>consider this Random Access Response reception successful.2>if the Random Access Response reception is considered successful:3>if the Random Access Response includes a MAC subPDU with RAPID only:4>consider this Random Access procedure successfully completed;4>indicate the reception of an acknowledgement for SI request to upper layers .3>else:4>apply the following actions for the Serving Cell where the Random Access Preamble wastransmitted:5>process the received Timing Advance Command (see subclause 5.2);5>indicate the preambleReceivedTargetPower and the amount of power ramping applied to thelatest Random Access Preamble transmission to lower layers (i.e.(PREAMBLE_POWER_RAMPING_ COUNTER − 1) ×PREAMBLE_POWER_RAMPING_STEP);5>if the Serving Cell for the Random Access procedure is SRS-only SCell:6>ignore the received UL grant.5>else:6>process the received UL grant value and indicate it to the lower layers.4>if the Random Access Preamble was not selected by the MAC entity among the contention-basedRandom Access Preamble(s):5>consider the Random Access procedure successfully completed.4>else:5>set the TEMPORARY_C-RNTI to the value received in the Random Access Response;5>if this is the first successfully received Random Access Response within this Random Accessprocedure:6>if the transmission is not being made for the CCCH logical channel:7>indicate to Multiplexing and assembly entity to include a C-RNTI MAC CE in thesubsequent uplink transmission.6>obtain the MAC PDU to transmit from the Multiplexing and assembly entity and store it inthe Msg3 buffer.

TABLE 4Completion of a Random Access ProcedureUpon completion of the Random Access procedure, the MAC entity shall:1>discard explicitly signalled contention-free Random Access Resources except contention-free Random AccessResources for beam failure recovery request, if any;1>flush the HARQ buffer used for transmission of the MAC PDU in the Msg3 buffer.

In certain embodiments described herein, a UE may switch between CBRA and CFRA and, in such embodiments, a Msg3 buffer may not be empty at a time in which the UE performs CFRA.

In various embodiments, for switching between CBRA and CFRA, if a grant provided in response to a CFRA preamble transmission is equal in size to a grant provided earlier in a response to a CBRA preamble transmission, a MAC PDU in a Msg3 buffer may be transmitted in the provided grant. However, in such embodiments, two different preamble groups may be defined and a network may not know if the UE has attempted CBRA before CFRA. Accordingly, it may not be possible for the network to know which size of grant should be provided to the UE to avoid different grant sizes from the MAC PDU being in the Msg3 buffer.

As may be appreciated, various embodiments described herein may be used for: rebuilding a MAC PDU if a UL grant received within RAR doesn't match a size of a TB in a Msg3 buffer; and/or avoiding flushing of a HARQ buffer used for transmission of the MAC PDU generated according to the UL grant received within RAR.

In some embodiments, a UE implementation may be used to determine what happens if a RAR grant size does not match a size of a TB stored in a Msg3 buffer is not specified. In certain embodiments, a UE may generate a new transport block according to a latest received RAR UL grant. In other words, data contained in a TB in a Msg3 buffer may be lost (e.g., for RLC-UM/TM) or a network and/or UE may rely on an RLC retransmission for RLC-AM.

In various embodiments, a UE may set an RLC context and/or status LCHs for which data is contained in a TB in a Msg3 buffer to a time instance before LCP is performed for the TB in the Msg3 buffer (e.g., undo an LCP procedure for the TB stored in the Msg3 buffer). As described herein, a loss of data may be avoided if an RAR grant size does not match a size of a TB Stored in a Msg3 buffer.

FIG. 4is a communication diagram illustrating one embodiment of communications400as part of a RACH procedure. The communications400occur between a UE402(e.g., remote unit102) and an eNB404(e.g., network unit104, gNB). As may be appreciated, each of the communications400described herein may include one or more messages.

In one embodiment, in a first communication406transmitted from the eNB404to the UE402, the eNB404transmits a SIB to the UE402. In certain embodiments, in a second communication408transmitted from the UE402to the eNB404, the UE402transmits a PRACH preamble to the eNB404. In some embodiments, in a third communication410transmitted from the eNB404to the UE402, the eNB404transmits a RAR to the UE402.

In various embodiments, in a fourth communication412transmitted from the UE402to the eNB404, the UE402transmits an uplink transmission on the PUSCH, e.g. connect request message to the eNB404. In one embodiment, in a fifth communication414transmitted from the eNB404to the UE402, the eNB404transmits a contention resolution message to the UE402.

As may be appreciated,FIG. 4shows CBRA. It should be noted that CFRA does not include the fourth communication412and the fifth communication414. In some embodiments, in CFRA a UE may be allocated a RACH preamble and/or RACH resource (e.g., by means of a PDCCH order) that makes a need for a contention resolution obsolete. An RAR message may have the same content for CBRA and CFRA. As may be appreciated, a CFRA may be used for handover (HO), uplink timing alignment, and beam failure recovery, for example.

In a first embodiment, a UE may flush only a HARQ buffer used for transmission of a MAC PDU in a Msg3 buffer if a PRACH preamble is selected from a set of contention-based random access preambles. In other words, if a RACH attempt successfully completed (e.g., a random access procedure successfully completed) is a contention-based RACH, the UE may flush a HARQ buffer used for transmission of a MAC PDU of a Msg3 buffer (e.g., the HARQ buffer of HARQ process 0). If a contention-free RACH attempt is successfully completed, a UE may not flush a HARQ buffer.

Table 5 shows one embodiment of an implementation of completion of a random access procedure based on the first embodiment.

TABLE 5Completion of a Random Access ProcedureUpon completion of the Random Access procedure, the MAC entity shall:1>discard explicitly signalled contention-free Random Access Resources except contention-free Random AccessResources for beam failure recovery request, if any;1>if the Random Access Preamble was selected by the MAC entity among the contention-based Random AccessPreamble(s):2>flush the HARQ buffer used for transmission of the MAC PDU in the Msg3 buffer.

In certain embodiments, a new condition may ensure that a HARQ buffer of a HARQ process 0 is not flushed if CFRA is performed by a UE. Therefore, if the UE switches between a CBRA and CFRA, the HARQ buffer used for transmission of Msg3 TB is not flushed. Hence the MAC PDU that is obtained from a Msg3 buffer may be transmitted (or retransmitted) on UL resources granted by an UL grant in a RAR and/or on uplink resources allocated by a retransmission grant.

In a second embodiment, a UE may first flush a HARQ buffer used for transmission of a MAC PDU in a Msg3 buffer before processing a received UL grant within a RAR and obtaining the MAC PDU from the Msg3 buffer (e.g., if a MAC PDU is stored in a Msg3 buffer). Therefore, HARQ buffer flushing may be executed before an UL grant received within a RAR is processed.

In a third embodiment, if an UL grant is received within a RAR message that does not fit a size of a TB stored in the Msg3 buffer, a UE performs an LCP procedure according to the UL grant received within the RAR. Accordingly, MAC subPDUs from a MAC PDU stored in a Msg3 buffer may be used as an input to the LCP procedure.

In certain embodiments, MAC subPDUs (e.g. MAC subPDUs carrying MAC CEs or MAC subPDUs carrying MAC SDUs) from a MAC PDU in a Msg3 buffer may be prioritized over any other data pending in a UE for transmission. In such embodiments, the UE may reserve space for the MAC subPDUs from the MAC PDU in the Msg3 buffer in the TB scheduled by the RAR (e.g., as indicated by an UL grant within a RAR) and may add MAC subPDUs according to an LCP procedure. As may be appreciated, including the MAC subPDUs from the MAC PDU in Msg3 buffer may not affect a token bucket status of corresponding logical channels. If the TB size indicated by the UL grant within the RAR is larger than the TB stored in Msg3 buffer, the UE takes all the MAC subPDUs from the TB stored in the Msg3 buffer (e.g., except possibly padding MAC subPDU) and fills the remaining available space with new MAC subPDUs according to the LCP procedure.

In some embodiments, if a TB size indicated by an UL grant within a RAR is smaller than the TB size of a MAC PDU stored in a Msg3 buffer, a UE may take MAC subPDUs from an obtained MAC PDU (e.g., the TB from the Msg3 buffer) in a descending priority order starting with a highest priority MAC subPDU until the UL grant is exhausted. The remaining space may be filled with MAC subPDUs (e.g., new MAC subPDUs) according to an LCP procedure. In one embodiment, a priority of the MAC subPDUs may be defined according a relative priority order specified in section 5.4.3.1.3 of TS38.321 as well as a logical channel priority configured by RRC signaling. In such embodiments, the MAC subPDUs (e.g. MAC subPDUs carrying MAC CEs or MAC subPDUs carrying MAC SDUs) from the MAC PDU in the Msg3 buffer may be prioritized over any other data pending in the UE for transmission (e.g., the UE reserves space for the MAC subPDUs from the MAC PDU in the Msg3 buffer from the TB size—such as by being indicated by the UL grant within RAR).

In certain embodiments, because an LCP procedure may be done for an entire UL grant, LCP may be performed for a TB size indicated by the UL grant and a generated MAC PDU may be compliant to a defined MAC PDU format (e.g., MAC subPDUs taken from the TB stored in the Msg3 buffer and newly generated MAC subPDUs may be placed at a correct position within a MAC PDU).

Table 6 shows one embodiment of implementing the third embodiment. In Table 6, a UE may indicate to a multiplexing and assembly entity to include MAC subPDUs from an obtained MAC PDU in a subsequent uplink transmission thereby prioritizing MAC subPDUs from the obtained MAC PDU over newly generated MAC subPDUs if an uplink grant size (e.g., received within a RAR) does not match the size of the MAC PDU from a Msg3 buffer.

TABLE 6HARQ Entity2>if the uplink grant was received in a Random Access Response; or2>if the uplink grant is part of a bundle of the configured uplink grant, and may be used for initialtransmission according to subclause 6.1.2.3 of TS 38.214 [7], and if no MAC PDU has been obtained forthis bundle:3>if there is a MAC PDU in the Msg3 buffer and the uplink grant was received in a Random AccessResponse:4>obtain the MAC PDU to transmit from the Msg3 buffer.4>if the uplink grant size does not match with the size of the obtained MAC PDU:5>indicate to the Multiplexing and assembly entity to include MAC subPDUs from the obtainedMAC PDU in the subsequent uplink transmission thereby prioritizing MAC subPDUs fromthe obtained MAC PDU over newly generated MAC subPDUs;5>obtain the MAC PDU to transmit from the Multiplexing and assembly entity.3>else:4>obtain the MAC PDU to transmit from the Multiplexing and assembly entity, if any;3>if a MAC PDU to transmit has been obtained:4>deliver the MAC PDU and the uplink grant and the HARQ information of the TB to the identifiedHARQ process;4>instruct the identified HARQ process to trigger a new transmission;

In various embodiments, a UE prioritizes MAC subPDUs from a MAC PDU in a Msg3 buffer containing a MAC SDU of an SRB over any other data (e.g., data pending in the UE for transmission as well as other MAC subPDUs from the MAC PDU in the Msg3 buffer). In such embodiments, an RRC message may be placed first in a new MAC PDU (e.g., generated according to an UL grant within a RAR) before a MAC CE. As may be appreciated, a benefit of such a prioritization may be that a handover complete message may be carried in a newly generated MAC PDU even if a TB size indicated by the UL grant within the RAR is smaller than the TB size of the MAC PDU stored in the Msg3 buffer.

In a fourth embodiment, if a UE receives an UL grant within a RAR message that does not fit a size of a TB stored in a Msg3 buffer, the UE may perform an LCP procedure according to the UL grant received within the RAR, thereby using MAC subPDUs from a MAC PDU stored in the Msg3 buffer as an input to the LCP procedure except MAC subPDUs containing a MAC CE or padding (using MAC subPDUs containing a MAC SDU as an input to the LCP procedure). In such an embodiment, the UE may instruct a multiplexing and assembly procedure to newly generate MAC CEs contained in the TB stored in the Msg3 buffer. For example, if a BSR MAC CE is contained within the MAC PDU in the Msg3 buffer, then the UE may generate a new BSR MAC CE (e.g., reflecting the most recent buffer status) and include it in the MAC PDU (e.g., if there is sufficient space according to an LCP procedure). Therefore, the BSR MAC CE type may be different (e.g., truncated BSR MAC CE may be contained in the TB from the Msg3 buffer) as long as the BSR MAC CE is included in the new MAC PDU according to the UL grant received within the RAR.

In some embodiments, a UE considers MAC subPDUs containing a MAC CE as input for an LCP procedure. However, the UE may update the content of the MAC CEs according to a most recent UE status (e.g., a buffer status for a BSR MAC CE or a power situation for a PHR MAC CE).

FIG. 5is a flow chart diagram illustrating one embodiment of a method500for using a medium access control protocol data unit in a message 3 buffer. In some embodiments, the method500is performed by an apparatus, such as the remote unit102. In certain embodiments, the method500may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

The method500may include, in response to a medium access control protocol data unit being in a message 3 buffer and receiving an uplink grant: obtaining502the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicating to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtaining the medium access control protocol data unit from the multiplexing and assembly entity.

In certain embodiments, receiving the uplink grant comprises receiving the uplink grant within a random access response as part of a non-contention based random access procedure. In some embodiments, the method500further comprises performing a logical channel prioritization procedure based on the uplink grant. In various embodiments, the medium access control sub-protocol data units are used as inputs to the logical channel prioritization procedure.

In one embodiment, the medium access control sub-protocol data units comprising a medium access control control element are excluded from being part of the inputs. In certain embodiments, the medium access control sub-protocol data units comprising padding are excluded from being part of the inputs. In some embodiments, the method500further comprises instructing the multiplexing and assembly entity to generate medium access control control elements contained in the medium access control protocol data unit.

In various embodiments, the method500further comprises flushing a hybrid automatic repeat request buffer used for transmission of the medium access control protocol data unit in the message 3 buffer if a random access channel preamble from a set of contention-based random access preambles is used. In one embodiment, the method500further comprises flushing a hybrid automatic repeat request buffer used for transmission of the medium access control protocol data unit in the message 3 buffer before processing the uplink grant.

In one embodiment, a method comprises: in response to a medium access control protocol data unit being in a message 3 buffer and receiving an uplink grant: obtaining the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicating to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtaining the medium access control protocol data unit from the multiplexing and assembly entity.

In certain embodiments, receiving the uplink grant comprises receiving the uplink grant within a random access response as part of a non-contention based random access procedure.

In some embodiments, the method further comprises performing a logical channel prioritization procedure based on the uplink grant.

In various embodiments, the medium access control sub-protocol data units are used as inputs to the logical channel prioritization procedure.

In one embodiment, the medium access control sub-protocol data units comprising a medium access control control element are excluded from being part of the inputs.

In certain embodiments, the medium access control sub-protocol data units comprising padding are excluded from being part of the inputs.

In some embodiments, the method further comprises instructing the multiplexing and assembly entity to generate medium access control control elements contained in the medium access control protocol data unit.

In various embodiments, the method further comprises flushing a hybrid automatic repeat request buffer used for transmission of the medium access control protocol data unit in the message 3 buffer if a random access channel preamble from a set of contention-based random access preambles is used.

In one embodiment, the method further comprises flushing a hybrid automatic repeat request buffer used for transmission of the medium access control protocol data unit in the message 3 buffer before processing the uplink grant.

In one embodiment, an apparatus comprises: a receiver; and a processor that: in response to a medium access control protocol data unit being in a message 3 buffer and the receiver receiving an uplink grant: obtains the medium access control protocol data unit from the message 3 buffer; if a first size of the uplink grant does not match a second size of the medium access control protocol data unit: indicates to a multiplexing and assembly entity to include medium access control sub-protocol data units carrying medium access control service data units from the obtained medium access control protocol data unit in a subsequent uplink transmission; and obtains the medium access control protocol data unit from the multiplexing and assembly entity.

In certain embodiments, the receiver receiving the uplink grant comprises the receiver receiving the uplink grant within a random access response as part of a non-contention based random access procedure.

In some embodiments, the processor performs a logical channel prioritization procedure based on the uplink grant.

In various embodiments, the medium access control sub-protocol data units are used as inputs to the logical channel prioritization procedure.

In one embodiment, the medium access control sub-protocol data units comprising a medium access control control element are excluded from being part of the inputs.

In certain embodiments, the medium access control sub-protocol data units comprising padding are excluded from being part of the inputs.

In some embodiments, the processor instructs the multiplexing and assembly entity to generate medium access control control elements contained in the medium access control protocol data unit.

In various embodiments, the processor flushes a hybrid automatic repeat request buffer used for transmission of the medium access control protocol data unit in the message 3 buffer if a random access channel preamble from a set of contention-based random access preambles is used.

In one embodiment, the processor flushes a hybrid automatic repeat request buffer used for transmission of the medium access control protocol data unit in the message 3 buffer before processing the uplink grant.