Patent Description:
The following abbreviations are herewith defined, at least some of which are referred to within the following description: Third Generation Partnership Project ("3GPP"), <NUM>th Generation ("<NUM>"), 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"), Cell RNTI ("C-RNTI"), Carrier Aggregation ("CA"), Contention-Based Random Access ("CBRA"), Clear Channel Assessment ("CCA"), Common Control Channel ("CCCH"), 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"), Channel Occupancy Time ("COT"), 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"), <NUM> 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 <NUM> ("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"), NR Unlicensed ("NR-U"), 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"), RA RNTI ("RA-RNTI"), Radio Access Network ("RAN"), Radio Access Technology ("RAT"), Random Access Procedure ("RACH"), Random Access Preamble Identifier ("RAPID"), 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"), Timing Advance ("TA"), Timing Alignment Timer ("TAT"), 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"), UL SCH ("UL-SCH"), 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, the RACH procedure may take longer than desired.

<NPL>, provides a discussion of <NUM>-step RACH procedure and <NUM>-step RACH procedure.

<NPL>, provides a discussion on the calculation of RA-RNTI for different types of random access.

As defined by claim <NUM>, the invention provides a method performed by a user equipment, UE, the method comprising: determining whether to perform a two-step random access channel procedure or a four-step random access channel procedure; and in response to determining to perform the two-step random access channel procedure: in a first step: transmitting a preamble in a first time slot; and transmitting an uplink data transmission via a physical uplink shared channel, PUSCH, in a second time slot different from the first time slot, wherein the second time slot is a time offset later than the first time slot, wherein the time offset corresponds to a subcarrier spacing; and in a second step: receiving a response message corresponding to the first step, wherein the response message comprises a radio network temporary identifier, RNTI, wherein the RNTI for the two-step random access channel procedure is calculated using a first formula, and an RNTI for the four-step random access channel procedure is calculated using a second formula different from the first formula. Preferred embodiments of the method of claim <NUM> are defined by claims <NUM> to <NUM>.

As defined by claim <NUM>, the invention provides a user equipment, UE, for wireless communication, comprising: at least one memory; and at least one processor (<NUM>) coupled with the at least one memory and configured to cause the UE to: determine whether to perform a two-step random access channel procedure or a four- step random access channel procedure, wherein the at least one processor coupled with the at least one memory is further configured to cause the UE to, in response to determining to perform the two-step random access channel procedure: in a first step: transmit a preamble in a first time slot; and transmit an uplink data transmission via a physical uplink shared channel, PUSCH, in a second time slot different from the first time slot, wherein the second time slot is a time offset later than the first time slot, wherein the time offset corresponds to a subcarrier spacing; and in a second step: receive a response message corresponding to the first step, wherein the response message comprises a radio network temporary identifier, RNTI, wherein the RNTI for the two-step random access channel procedure is calculated using a first formula, and a RNTI for the four-step random access channel procedure is calculated using a second formula different from the first formula. Preferred embodiments of the user equipment of claim <NUM> are defined by claims <NUM> to <NUM>.

As defined by claim <NUM>, the invention provides a method performed by a base station, the method comprising: receiving a preamble in a first time slot and receiving an uplink data transmission via a physical uplink shared channel, PUSCH, in a second time slot different from the first time slot in response to a determination by a remote unit to perform a two-step random access channel procedure, wherein the second time slot is a time offset later than the first time slot, wherein the time offset corresponds to a subcarrier spacing; and transmitting a response message corresponding to the preamble, wherein the response message comprises a radio network temporary identifier, RNTI, wherein the RNTI for the two-step random access channel procedure is calculated using a first formula, and a RNTI for a four-step random access channel procedure is calculated using a second formula different from the first formula.

As defined by claim <NUM>, the invention provides a base station for wireless communication, comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the base station to: receive a preamble in a first time slot and receiving an uplink data transmission via a physical uplink shared channel, PUSCH, in a second time slot different from the first time slot in response to a determination by a remote unit to perform a two-step random access channel procedure, wherein the second time slot is a time offset later than the first time slot, wherein the time offset corresponds to a subcarrier spacing; and transmit a response message corresponding to the preamble, wherein the response message comprises a radio network temporary identifier, RNTI, wherein the RNTI for the two-step random access channel procedure is calculated using a first formula, and an RNTI for a four-step random access channel procedure is calculated using a second formula different from the first formula.

<FIG> depicts an embodiment of a wireless communication system <NUM> for performing a two-step random access channel procedure. In one embodiment, the wireless communication system <NUM> includes remote units <NUM> and network units <NUM>. Even though a specific number of remote units <NUM> and network units <NUM> are depicted in <FIG>, one of skill in the art will recognize that any number of remote units <NUM> and network units <NUM> may be included in the wireless communication system <NUM>.

In one embodiment, the remote units <NUM> may include computing devices, such as desktop computers, laptop computers, personal digital assistants ("PDAs"), tablet computers, smart phones, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle on-board computers, network devices (e.g., routers, switches, modems), aerial vehicles, drones, or the like. The remote units <NUM> may communicate directly with one or more of the network units <NUM> via UL communication signals.

In one embodiment, a remote unit <NUM> may determine whether to perform a two-step random access channel procedure or a four-step random access channel procedure. In some embodiments, the remote unit <NUM> may, in response to determining to perform the two-step random access channel procedure: in a first step: transmit a preamble in a first time slot; and transmit an uplink data transmission via a physical uplink shared channel in a second time slot different from the first time slot; and, in a second step, receive a response message corresponding to the first step, wherein the response message comprises a radio network temporary identifier. Accordingly, the remote unit <NUM> may be used for performing a two-step random access channel procedure.

In certain embodiments, a network unit <NUM> may receive a preamble in a first time slot and receiving an uplink data transmission via a physical uplink shared channel in a second time slot different from the first time slot in response to a determination by a remote unit to perform a two-step random access channel procedure. In some embodiments, the network unit <NUM> may transmit a response message corresponding to the preamble and the uplink data transmission, wherein the response message comprises a radio network temporary identifier. Accordingly, the network unit <NUM> may be used for performing a two-step random access channel procedure.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for performing a two-step random access channel procedure. The apparatus <NUM> includes one embodiment of the remote unit <NUM>. Furthermore, the remote unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. In some embodiments, the input device <NUM> and the display <NUM> are combined into a single device, such as a touchscreen. In certain embodiments, the remote unit <NUM> may not include any input device <NUM> and/or display <NUM>. In various embodiments, the remote unit <NUM> may include one or more of the processor <NUM>, the memory <NUM>, the transmitter <NUM>, and the receiver <NUM>, and may not include the input device <NUM> and/or the display <NUM>.

In various embodiments, the processor <NUM> may determine whether to perform a two-step random access channel procedure or a four-step random access channel procedure.

In some embodiments, in response to determining to perform the two-step random access channel procedure: in a first step, the transmitter <NUM>: transmits a preamble in a first time slot; and transmits an uplink data transmission via a physical uplink shared channel in a second time slot different from the first time slot; and in a second step, the receiver <NUM> receives a response message corresponding to the first step, wherein the response message comprises a radio network temporary identifier.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for performing a two-step random access channel procedure. The apparatus <NUM> includes one embodiment of the network unit <NUM>. Furthermore, the network unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. As may be appreciated, the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> may be substantially similar to the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> of the remote unit <NUM>, respectively.

In various embodiments, the receiver <NUM> receives a preamble in a first time slot and receives an uplink data transmission via a physical uplink shared channel in a second time slot different from the first time slot in response to a determination by a remote unit to perform a two-step random access channel procedure. In some embodiments, the transmitter <NUM> transmits a response message corresponding to the preamble and uplink data transmission, wherein the response message comprises a radio network temporary identifier. Although only one transmitter <NUM> and one receiver <NUM> are illustrated, the network unit <NUM> may have any suitable number of transmitters <NUM> and receivers <NUM>.

In certain configurations, a CBRA procedure involves the exchange of four messages. In such configurations, when performing a RACH procedure on an unlicensed cell, each of the four messages exchanged during the RACH procedure may undergo a CCA procedure before a transmission may be made on the unlicensed cell. To reduce time for the RACH procedure, a <NUM>-step RACH procedure may be used.

Certain details of a <NUM>-step RACH procedure may include: <NUM>) a format and/or content of a response message (e.g., in step <NUM> of the <NUM>-step RACH procedure); <NUM>) power control issues for a preamble and an uplink transmission in step <NUM> of the <NUM>-step RACH procedure; <NUM>) uplink timing for a PUSCH transmission and a preamble transmission in step <NUM> of the <NUM>-step RACH procedure; <NUM>) switching between a <NUM>-step RACH procedure and a <NUM>-step RACH procedure; and/or <NUM>) resource allocation for an uplink transmission in step <NUM> of the <NUM>-step RACH procedure.

<FIG> is a communication diagram illustrating one embodiment of communications <NUM> as part of a RACH procedure (e.g., <NUM>-step RACH procedure). The communications <NUM> occur between a UE <NUM> (e.g., remote unit <NUM>) and a gNB <NUM> (e.g., network unit <NUM>, gNB). As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In one embodiment, in a first communication <NUM> transmitted from the gNB <NUM> to the UE <NUM>, the gNB <NUM> transmits a SIB to the UE <NUM>. In certain embodiments, in a second communication <NUM> transmitted from the UE <NUM> to the gNB <NUM>, the UE <NUM> transmits a PRACH preamble to the gNB <NUM>. In some embodiments, in a third communication <NUM> transmitted from the gNB <NUM> to the UE <NUM>, the gNB <NUM> transmits a RAR to the UE <NUM>.

In various embodiments, in a fourth communication <NUM> transmitted from the UE <NUM> to the gNB <NUM>, the UE <NUM> transmits an uplink transmission on the PUSCH, e.g. connection request message to the gNB <NUM>. In one embodiment, in a fifth communication <NUM> transmitted from the gNB <NUM> to the UE <NUM>, the gNB <NUM> transmits a contention resolution message to the UE <NUM>.

As may be appreciated, <FIG> shows CBRA. It should be noted that CFRA does not include the fourth communication <NUM> and the fifth communication <NUM>. 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 HO, uplink timing alignment, and beam failure recovery, for example.

As may be appreciated, various embodiments described herein may be applied to CBRA. Moreover, embodiments described herein may be described in the context of an unlicensed transmission and/or cell (e.g., NR-U); however, the embodiments herein may also be applicable to licensed cells (e.g., NR or LTE).

<FIG> is a communication diagram illustrating another embodiment of communications <NUM> as part of a RACH procedure (e.g., <NUM>-step RACH procedure). The communications <NUM> occur between a UE <NUM> (e.g., remote unit <NUM>) and an gNB <NUM> (e.g., network unit <NUM>, gNB). As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In one embodiment, in a first communication <NUM> transmitted from the gNB <NUM> to the UE <NUM>, the gNB <NUM> transmits a SIB to the UE <NUM>. In certain embodiments, in a second communication <NUM> (e.g., first step in the <NUM>-step RACH procedure, msg1 and msg3 of the <NUM>-step RACH procedure) transmitted from the UE <NUM> to the gNB <NUM>, the UE <NUM> transmits a PRACH preamble to the gNB <NUM> and an uplink transmission (e.g., on PUSCH). In some embodiments, in a third communication <NUM> transmitted from the gNB <NUM> to the UE <NUM>, the gNB <NUM> transmits a RAR and a contention resolution message to the UE <NUM> (e.g., second step in the <NUM>-step RACH procedure, msg2 and msg4 of the <NUM>-step RACH procedure).

In one embodiment, a UE, after having sent in a first step of a <NUM>-step RACH procedure a preamble-like signal and an initial uplink transmission (e.g., on PUSCH), monitors for one or more response messages (e.g., in a second step of the <NUM>-step RACH procedure) sent from a gNB. In such an embodiment, the UE may monitor for the one or more response messages during a defined time period (e.g., time window). In such an embodiment, the UE monitors during the time window for a PDCCH identified by an RA-RNTI scheduling PDSCH resources on which the one or more response messages are transmitted.

In some embodiments, an initial uplink transmission transmitted in a first step of the <NUM>-step RACH procedure may include a TB containing at least a UE identifier such as a C-RNTI MAC control element or a UL CCCH SDU. In such embodiments, the TB may contain data of a data radio bearer or control information such as a BSR or a PHR.

In various embodiments, a response message (e.g., in step <NUM> of a <NUM>-step RACH procedure) sent from a network device (e.g., gNB) in response to the successful detection of a preamble-like signal (e.g., sent in step <NUM> of the <NUM>-step RACH procedure together with an initial uplink transmission) contains a random access preamble identifier field identifying a preamble received. In such embodiments, the response message may contain a TA Value that the gNB uses to inform the UE to change its timing so it may compensate for a round trip delay caused by the UE distance from the gNB. In certain embodiments, the response message may include an UL grant field within which a gNB may schedule a retransmission of a transport block transmitted in step-<NUM> of a <NUM>-step RACH procedure or a new initial uplink transmission. In some embodiments, if a TB and/or uplink transmission sent in a first step of a <NUM>-step RACH procedure along with a preamble-like signal are detected but not correctly decoded by a gNB, the gNB may schedule a retransmission of the TB. In such embodiments, because the TB may contain an identifier identifying a UE, the gNB may decode the TB as soon as possible to resolve a potential contention. In such embodiments, if the TB sent in the first step cannot be correctly decoded by the gNB, the gNB may schedule an additional uplink transmission within the response message. In such embodiments, if the TB sent in the first step can be correctly decoded by the gNB, the gNB may schedule a further initial uplink transmission within the response message. In certain embodiments, a HARQ process used for the transmission of an uplink transmission (e.g., on PUSCH) in step <NUM> of a <NUM>-step RACH procedure may be predefined, preconfigured, and/or fixed in a standard. It should be noted that an UL grant contained within a response message (e.g., in step <NUM> of a <NUM>-step RACH procedure) may allocate multiple uplink resources for an initial transmission or retransmission (e.g., for transmissions on an unlicensed cell).

In certain embodiments, depending on whether a TB containing an identifier sent in step <NUM> of a <NUM>-step RACH procedure is successfully decoded by a gNB, a response message may contain an ID field echoing the identifier sent in step <NUM>, thereby resolving a potential contention. For example, if an uplink transmission in step <NUM> containing a C-RNTI MAC CE (e.g., for UEs in an RRC_CONNECTED state having already a C-RNTI allocated) is successfully decoded, the response message may contain a C-RNTI MAC CE set to the same value as the C-RNTI MAC CE sent in step <NUM>. Similarly, as another example, if an uplink transmission sent in step <NUM> containing a UL CCCH SDU (e.g., UE in an RRC_IDLE state) is successfully decoded, the response message may carry a UE contention resolution ID MAC CE (e.g., first <NUM> bits of the UL CCCH SDU transmitted in step <NUM>). In some embodiments, if a TB sent in step <NUM> of a <NUM>-step RACH procedure cannot be successfully decoded, a response message may not contain an identifier field (e.g., C-RNTI MAC CE or UE contention resolution ID MAC CE) because the identity of a UE is not known to a gNB. In such embodiments, a potential contention may not be resolved (e.g., one or more further retransmissions of the uplink transmission of step <NUM> is required).

In some embodiments, a response message may contain a temporary C-RNTI field that may include an identity assigned by a gNB for further communication. In such embodiments, the temporary C-RNTI field may only be present in the response message, such as if a TB sent in step <NUM> of a <NUM>-step RACH procedure is not able to be successfully decoded or if the TB sent in step <NUM> contains a UL CCCH SDU (e.g., if a UE is in an RRC_IDLE state). In certain embodiments, if a UE in an RRC_CONNECTED state is performing a <NUM>-step RACH procedure and a TB sent in step <NUM> of the <NUM>-step RACH procedure is successfully decoded by a gNB, a C-RNTI field may not be used if the UE already has an assigned C-RNTI that is known to the gNB. In various embodiments, a temporary C-RNTI field is always present in a response message and a UE may ignore the temporary C-RNTI field upon reception of the response message if the identifier sent in the response message (e.g., temporary C-RNTI MAC CE) matches an ID sent in step <NUM> of the <NUM>-step RACH procedure.

In one embodiment, a response message of a <NUM>-step RACH procedure is transmitted within a RACH response message transmitted on a PDSCH (e.g., MAC PDU). In certain embodiments, a UE may monitor upon transmission of a preamble and an UL transmission during a RACH response window for a response message (e.g., PDCCH addressed to RA-RNTI calculated from a timeslot in which the preamble is sent). In some embodiments, a RAPID in a MAC subheader for a random access response indicates whether a corresponding MAC RAR is a legacy RAR or a new response message for a <NUM>-step RACH. In various embodiments, certain fields in a MAC RAR (e.g., MAC payload for a random access response) identify a response for a <NUM>-step RACH and a legacy random access response. For example, a reserved bit in a MAC RAR (e.g., see Table <NUM>) may be used to indicate a format of the MAC RAR (e.g., response for <NUM>-step RACH or a legacy RAR - <NUM>-step RACH RAR).

In certain embodiments, a first reserved bit set to '<NUM>' indicates that a response for a <NUM>-step RACH procedure is contained within the MAC RAR. In various embodiments, a format for a MAC RAR that includes a response for a <NUM>-step RACH procedure may be different than a legacy MAC RAR format. In one embodiment, a response message for a <NUM>-step RACH may schedule a retransmission of an uplink transmission made in step <NUM> of the <NUM>-step RACH procedure. In such an embodiment, an indicator that distinguishes between an UL grant for a retransmission and an initial transmission may be contained in the UL grant field. In certain embodiments, a response message for a <NUM>-step RACH procedure may contain a C-RNTI MAC CE or a UE contention resolution ID MAC CE (e.g., depending on a decoding status of a first uplink transmission and a UE RRC state). In various embodiments, a MAC RAR containing a response for <NUM>-step RACH procedure may have a variable size. In one embodiment, extension bits may indicate a presence of a C-RNTI MAC CE or a UE contention resolution ID MAC CE. In certain embodiments, a response message for a <NUM>-step RACH procedure may contain a DL allocation (e.g., either a DL TB or DL grant information pointing to PDSCH resources).

In various embodiments, a RNTI, e.g. RA-RNTI, used for identifying a response for a <NUM>-step RACH procedure may be calculated differently (e.g., using a different formula) than the RA-RNTI used for a RAR of a legacy RACH procedure (e.g., <NUM>-step RACH procedure). As used herein, a legacy RACH procedure may refer to a <NUM>-step RACH procedure.

In some embodiments, in response to not receiving a response message in step <NUM> of a <NUM>-step RACH procedure, a UE may repeat step <NUM> of the <NUM>-step RACH procedure and may send a preamble-like signal together with an uplink transmission. In certain embodiments, a UE that does not successfully receive a response message within a defined time window may assume that a preamble was not detected by a gNB. In various embodiments, a UE transmits or retransmits a preamble and an uplink transmission sent previously in step <NUM> of a <NUM>-step RACH procedure with an increased transmission power than a transmission power used for a previous transmission of the preamble and the uplink transmission (e.g., power ramping may be applied to both the preamble and the uplink transmission).

In one embodiment, a UE switches to a legacy <NUM>-step RACH procedure in the absence of a response message during a defined time window. In some embodiments, if a UE doesn't successfully receive a response message for a <NUM>-step RACH procedure, the UE switches to the legacy <NUM>-step RACH procedure and subsequently transmits only a preamble (e.g., no UL transmission on PUSCH with the preamble). In various embodiments, a preamble transmission may be transmitted with an increased transmission power as compared to a previous preamble transmission (e.g., power ramping). In certain embodiments in which different preambles are used for a <NUM>-step RACH procedure and a legacy <NUM>-step RACH procedure, a UE may select a preamble reserved for the <NUM>-step RACH procedure. In one embodiment, a UE stores a MAC PDU sent in step <NUM> of a <NUM>-step RACH procedure in a Msg3 buffer if switching to a <NUM>-step RACH procedure. In some embodiments, a new transmission buffer may be used in which a UE stores a MAC PDU sent in step <NUM> of a <NUM>-step RACH procedure after generating the MAC PDU. As may be appreciated, storing a MAC PDU generated for step <NUM> in a separate buffer may enable later retransmissions of the generated MAC PDU (e.g., if contention resolution fails).

In certain embodiments, a UE transmits or retransmits a preamble together with an uplink (e.g., UL-SCH) transmission in the absence of a response message. In such embodiments, the UE may determine whether to apply power ramping (e.g., transmitting with an increased TX power compared to a previous transmission) for both the preamble and the uplink transmission or for only the preamble. In one embodiment, a UE calculates a required transmission power for both a preamble transmission Ppreamble using a power control formula specified for preamble transmission thereby assuming an predefined power offset and for an uplink transmission PUL using a power control formula specified for the uplink transmission to account for the predefined power offset. It should be noted that the predefined power offset, also referred to as Power_Ramping_Stepsize, may be separately defined for the preamble transmission and the uplink transmission. In certain embodiments, if a sum of a required transmission power for a preamble and an uplink transmission (e.g., including power offsets) does not exceed a UE's total maximum transmission power (e.g., PCMAX,f,c(i)), power ramping may be applied to both the preamble and the uplink transmission. In various embodiments, if a sum of PPreamble including a power offset and PUL without consideration of a power offset doesn't exceed Pcmax,c , power ramping may only be applied to the preamble transmission. In some embodiments, if PPreamble including a power offset and PUL without consideration of a power offset exceeds PCMAX,f,c(i), a UE may switch to a legacy <NUM>-step RACH procedure.

In one embodiment, a UE transmits a preamble-like signal and an uplink data transmission conveyed by PUSCH (e.g., elements forming step <NUM> in a <NUM>-step RACH procedure) in different time slots. As may be appreciated, one benefit of transmitting the preamble-like signal and the uplink data transmission in different time slots may be that a power between the preamble-like signal and the uplink data transmission does not need to be shared so that both transmissions may operate at optimum coverage (e.g., optimal power). Further, it should be noted that another benefit of transmitting the preamble-like signal and the uplink data transmission in different time slots may be that a network node (e.g., gNB) may first detect the preamble-like transmission, and upon successful detection of the preamble-like transmission proceed to receive the uplink data transmission. Furthermore, transmitting the preamble-like signal and the uplink data transmission in different time slots may eliminate and/or reduce the need for precautionary buffering of a received time slot.

In some embodiments, different gNB implementations may need a different amount of time to successfully detect a preamble. Therefore, in one embodiment, a gNB may configure a time offset that a UE has to observe between a transmission of a preamble-like signal and a transmission of uplink data. In such an embodiment, the configuration may be advertised (e.g., in broadcast information in an SIB because all UEs may observe the same offset). In certain embodiments, an offset may depend on an employed subcarrier spacing (e.g., because a duration of a preamble-like signal may be a function of the subcarrier spacing) even though a required detection time may not scale equally. For example, in a first subcarrier spacing, an offset may be <NUM> slot, and in another subcarrier spacing the offset may be <NUM> slots. As may be appreciated, because it is possible that a gNB has sufficient capability to buffer a received signal, it may be beneficial if an offset can be <NUM> slots (e.g., implying that a preamble-like signal and an uplink data transmission occur in the same slot). In various embodiments, an offset of <NUM> slot may indicate that a UE is to transmit a preamble-like signal in slot n1, and an uplink data transmission in slot n2=n1+<NUM>. In other words, both transmissions are adjacent in time. As may be appreciated, this may be beneficial in an unlicensed carrier configuration in which the UE contends for channel access (e.g., where any gap may bear the risk of losing a right to transmit on a channel), or with interference from a hidden node.

In one embodiment, if an offset is larger than <NUM> slot and if a RACH procedure occurs on an unlicensed carrier, a UE may perform a clear channel assessment before transmission of uplink data. As may be appreciated, this may result in not being able to transmit the uplink data in a designated slot due to a blocked channel. In certain embodiments, a UE repeats a transmission of a preamble-like signal and uplink data for a number of consecutive slots based on an offset value. In some embodiments, if an offset value is n_o, then a UE may transmit and/or repeat a preamble-like signal during n_o slots followed by uplink data transmitted and/or repeated during n_o slots. Accordingly, there may be no gap from the UE's transmission point of view thereby eliminating (e.g., or reducing) a risk of losing a channel access prior to the uplink data transmission. From the gNB's perspective, if the gNB detects the preamble-like signal in slot n1, then the gNB may be able to receive an uplink data signal in slot n1 + n_o.

In various embodiments, an offset may be set to a fixed value of <NUM> slot so that a preamble-like transmission and uplink data transmission occur in adjacent slots. As may be appreciated, this does not require a configuration of an offset value and, therefore, uses less overhead than configurations in which the offset is configured via a message and/or signaling.

In some embodiments, if a transmission of a preamble-like signal and uplink data occur in the same slot, available transmit power of a UE may be shared. In such embodiments, the preamble-like signal may be prioritized over the uplink data signal so that the preamble-like signal is transmitted with a designated power, and the transmit power of the uplink data signal is reduced to not exceed a total available transmit power. In such embodiments, a good reception quality of the preamble-like signal may be made. Having good reception quality for the preamble-like signa may be more important than good reception quality of the uplink data transmission for the RACH procedure. In various embodiments, if a preamble is detected successfully but an uplink data transmission cannot be decoded correctly by a gNB, the gNB may still be aware that a RACH procedure has been initiated by the UE, and may request a retransmission of the uplink data.

In certain embodiments, to determine a transmit power of an uplink data transmission, a UE may use the same power control parameters for calculating a transmit power PPUSCH,b,f,c(i, j, qd, l) of the uplink transmission in step <NUM> of the <NUM>-step RACH procedure as the power control parameters used for a msg3 PUSCH transmission. The power control parameters may include PO_PUSCH,b,f,c , αb,f,c, , PLb,f,c(qd). In such embodiments, the PUSCH transmission in step <NUM> of the <NUM>-step RACH procedure may be treated as a msg3 PUSCH transmission from a power control perspective. In various embodiments, separate power control parameters may be defined for a PUSCH transmission in step <NUM> of a <NUM>-step RACH procedure (e.g., separate values are defined for PO_PUSCH,b,f,c , αb,f,c, , PLb,f,c(qd) to satisfy different requirements in terms of reliability (e.g., BLER) or latency). In various embodiments, the following formula may be used: <MAT>.

In some embodiments, if a UE is not provided with a higher layer parameter P0-PUSCH-AlphaSet or for a msg3 PUSCH transmission, j = <NUM> , PO_UE_PUSCH,f,c(<NUM>) = <NUM>, and PO_NOMINAL_PUSCH,f,c(<NUM>) = PO_PRE + ΔPREAMBLE_Msg<NUM>, where the parameter preambleReceivedTargetPower (for PO_PRE) and msg3-DeltaPreamble (for ΔPREAMBLE_Msg<NUM> ) are provided by higher layers for carrier f of serving cell c.

For αb,f,c(j), j = <NUM> and αb,f,c(<NUM>) is a value of higher layer parameter msg3-Alpha, when provided; otherwise, αb,f,c(<NUM>) = <NUM>. <MAT> is the bandwidth of the PUSCH resource assignment expressed in number of resource blocks for PUSCH transmission occasion i on UL BWP b of carrier f of serving cell c and µ may be predefined. PLb,f,c(qd)is a downlink path-loss estimate in dB calculated by the UE using reference signal (RS) index qd for a DL BWP that is linked with UL BWP b of carrier f of serving cell c.

If the UE is not provided higher layer parameter PUSCH-PathlossReferenceRS and before the UE is provided dedicated higher layer parameters, the UE calculates PLb,f,c(qd) using a RS resource from the SS/PBCH block index that the UE obtains higher layer parameter MasterInformationBlock.

If the UE is configured with a number of RS resource indexes up to the value of higher layer parameter maxNrofPUSCH-PathlossReferenceRSs and a respective set of RS configurations for the number of RS resource indexes by higher layer parameter PUSCH-PathlossReferenceRS. The set of RS resource indexes can include one or both of a set of SS/PBCH block indexes, each provided by higher layer parameter ssb-Index when a value of a corresponding higher layer parameter pusch-PathlossReferenceRS-Id maps to a SS/PBCH block index, and a set of CSI-RS resource indexes, each provided by higher layer parameter csi-RS-Index when a value of a corresponding higher layer parameter pusch-PathlossReferenceRS-Id maps to a CSI-RS resource index. The UE identifies a RS resource index in the set of RS resource indexes to correspond either to a SS/PBCH block index or to a CSI-RS resource index as provided by higher layer parameter pusch-PathlossReferenceRS-Id in PUSCH-PathlossReferenceRS.

If the PUSCH is an Msg3 PUSCH, the UE uses the same RS resource index as for a corresponding PRACH transmission.

PLb,f,c(qd) PLf,c(qd) = referenceSignalPower - higher layer filtered RSRP, where referenceSignalPower is provided by higher layers and RSRP is defined in [<NUM>, TS <NUM>] for the reference serving cell and the higher layer filter configuration is defined in [<NUM>, TS <NUM>] for the reference serving cell.

For j = <NUM> , referenceSignalPower is provided by higher layer parameter ss-PBCH-BlockPower. For j > <NUM> , referenceSignalPower is configured by either higher layer parameter ss-PBCH-BlockPower or, when periodic CSI-RS transmission is configured, by higher layer parameter powerControlOffsetSS providing an offset of the CSI-RS transmission power relative to the SS/PBCH block transmission power. <MAT> for KS =<NUM> and ΔTF,b,f,c(i) = <NUM> for KS = <NUM> where KS is provided by higher layer parameter deltaMCS provided for each UL BWP b of each carrier f and serving cell c. If the PUSCH transmission is over more than one layer [<NUM>, TS <NUM>], ΔTF,b,f,c(i) = <NUM>. BPRE and <MAT>, for each UL BWP b of each carrier f and each serving cell c , are computed as below. <MAT> for PUSCH with UL-SCH data and BPRE = OCSI / NRE for CSI transmission in a PUSCH without UL-SCH data, where
C is the number of code blocks, Kr is the size for code block r, OCSI is the number of CSI part <NUM> bits including CRC bits, and NRE is the number of resource elements determined as
<MAT>
where
<MAT>
is the number of symbols for PUSCH transmission occasion i on UL BWP b of carrier f of serving cell c, <MAT> is a number of subcarriers excluding DM-RS subcarriers in PUSCH symbol j, <MAT>, and C, Kr are defined in [<NUM>, TS <NUM>]. <MAT> when the PUSCH includes UL-SCH data and <MAT> when the PUSCH includes CSI and does not include UL-SCH data.

In certain embodiments, instead of reducing a power of an uplink data transmission, a UE may defer the uplink data transmission to a later slot if insufficient power is available for transmission of the preamble-like signal and the uplink data in the same slot. In some embodiments, to avoid creating transmission gaps on an unlicensed carrier, it may be advantageous if a UE defers an uplink data transmission to a next slot after a slot used to transmit a preamble-like signal so that the preamble-like signal and uplink data are transmitted in adjacent slots. In one embodiment, a gNB performs a blind detection of uplink data at expected resources in the same slot and one or more slots after a detected preamble-like signal. In another embodiment, a preamble-like signal indicates whether uplink data is transmitted in the same slot, or deferred to a later slot. For example, a plurality of preamble-like signals forms two or more sets in which the transmission of a preamble-like signal from a first set indicates that the uplink data is transmitted in the same slot as the preamble-like signal. In such an example, if the preamble-like signal is from a second set, this indicates that transmission of the uplink data is deferred to a later slot than the preamble-like signal (e.g., to the next slot). As may be appreciated, partitioning of the preamble-like signals to sets may be defined in a communication system, or configured by a network (e.g., by broadcast in system information or by dedicated configuration signals).

In various embodiments, a timing advance value used for an uplink transmission in step <NUM> of a <NUM>-step RACH procedure may be stored and maintained NTA in a UE for a serving cell on which the uplink transmission and a preamble transmission take place. It should be noted that if a TAT expires, a UE maintains NTA. In certain configurations, the UE is only allowed to perform a PRACH transmission if TAT is expired. In some embodiments, the UE performs an uplink transmission on PUSCH, e.g. in step <NUM> of a <NUM>-step RACH procedure, if the TAT is expired. In some embodiments, a UE uses NTA=<NUM> for an uplink transmission in step <NUM> of a <NUM>-step RACH procedure. In such embodiments, a preamble transmission and the uplink transmission may use the same timing advance value.

As may be appreciated, a UE, before it performs transmission of step <NUM> of a <NUM>-step RACH procedure, may determine which resources may be used for transmitting a preamble and an uplink transmission.

In one embodiment, PRACH resources are determined as in a <NUM>-step RACH procedure (e.g., using RACH-ConfigGeneric parameters broadcasted as part of SIB1 in <NUM> NR). It should be noted that parameters used to determine PUSCH resources may be broadcast specifically for the purpose of transmitting step <NUM> of a <NUM>-step RACH procedure. Accordingly, the PUSCH resources to be used by the UE may have a linking to chosen PRACH resources. The linking may be accomplished using one or more of the following offsets: <NUM>) frequency offset, O_f: offset of lowest PUSCH transmission occasion in a frequency domain with respective to PRACH resources defined by msg1-FrequencyStart in <NUM> NR system; and/or <NUM>) time offset, T_f: offset of lowest PUSCH transmission occasion in time domain with respective to PRACH transmission occasion chosen by the UE.

<FIG> is a resource diagram <NUM> illustrating a time offset and a frequency offset. The resource diagram <NUM> includes a 16x16 grid of resource elements <NUM>. One resource element <NUM> is PRB0 "A", another resource element <NUM> is the PRACH resource "B". A time offset <NUM> "T_f" is defined relative to the PRACH resource B to indicate a lowest time "T" in the time domain for a PUSCH transmission. This is illustrated by the column of resource elements <NUM> T. A frequency offset <NUM> "O_f" is defined relative to the PRACH resource B to indicate a lowest frequency "F" in the frequency domain for a PUSCH transmission. This is illustrated by the row of resource elements <NUM> F. The intersection of the lowest time T and the lowest frequency F is illustrated by resource element <NUM> "C".

As may be appreciated, a time offset may be a value in a number of symbols, a number of slots, or in milliseconds.

In certain embodiments, more than one set of O_f and T_f may be broadcast such that for one preamble ID or group of preambles IDs, one specific set of O_f and T_f may be used. For example, if <NUM> sets of O_f and T_f are broadcast then a first half of the preambles used in this cell (e.g., <NUM>. <NUM>) may use the first set of O_f and T_f and the second half of the preambles used in this cell (e.g., <NUM>. <NUM>) may use the second set of O_f and T_f. As may be appreciated, though broadcasting has been indicated above as the signaling mechanism, a dedicated RRC signaling or specified values may also be used (e.g., for a non-initial random access procedure).

In various embodiments, a network may configure how many PRBs are used for transmitting PUSCH of step <NUM> of a <NUM>-step RACH procedure using RRC signaling. In certain embodiments, physical layer parameters like MCS may be specified or configured using RRC signaling for transmitting the PUSCH of step <NUM> of a <NUM>-step RACH procedure.

In some embodiments, a UE decides whether to start a <NUM>-step RACH procedure or a legacy <NUM>-step RACH procedure once an RACH procedure has been triggered depending on certain criteria. In various embodiments, a UE may determine whether to start a <NUM>-step RACH procedure or a <NUM>-step RACH procedure based on e.g., its power status. In such embodiments, the UE calculates a required transmission power for both a preamble transmission Ppreamble according to the power control formula specified for preamble transmission and for an uplink transmission PUL according to a power control formula specified for the uplink transmission. In certain embodiments, if the sum of Ppreamble and PUL doesn't exceed a UE's total maximum transmission power (e.g., Pcmax,c ), a UE starts a <NUM>-step RACH procedure, otherwise the UE uses the <NUM>-step RACH procedure. In one embodiment, a criterion for determining whether to use a <NUM>-step RACH procedure or a <NUM>-step RACH procedure may be a size of data to be transmitted in an UL transmission (e.g., if the size of the data is above a certain configured threshold, the UE may use the <NUM>-step RACH procedure). In another embodiment, a network entity (e.g., such as a gNB) configures whether a UE is enabled, allowed, and/or obliged to perform a <NUM>-step RACH procedure and/or a <NUM>-step RACH procedure in a current cell. In such embodiment, the configuration may be made per RACH type (e.g., the <NUM>-step RACH procedure is used for handover situations and for scheduling request purposes the <NUM>-step RACH procedure is used). In certain embodiments, a PDCCH order or a RRC message ordering a handover may indicate whether to use a legacy contention-free RACH procedure or a <NUM>-step RACH procedure (e.g., a handover complete message may be included in step <NUM> of the <NUM>-step RACH procedure). In various embodiments, a configuration and/or a specification may indicate that a <NUM>-step RACH procedure is used in an unlicensed spectrum. In certain embodiments, use of a <NUM>-step RACH procedure or a <NUM>-step RACH procedure may be tied to COT (e.g., determining to use either the <NUM>-step RACH procedure or the <NUM>-step RACH procedure based on whether the COT is above and/or below certain threshold).

In some embodiments, a UE is enabled to use a channel access Type <NUM> (e.g., implying a fixed or shorter sensing interval for a CCA procedure) for transmission of a preamble-like signal and an uplink transmission in step <NUM> of a <NUM>-step RACH procedure.

<FIG> is a flow chart diagram illustrating one embodiment of a method <NUM> for performing a two-step random access channel procedure. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may 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 method <NUM> may include determining <NUM> whether to perform a two-step random access channel procedure or a four-step random access channel procedure. In some embodiments, the method <NUM> includes, in response to determining to perform the two-step random access channel procedure: in a first step: transmitting <NUM> a preamble in a first time slot; and transmitting an uplink data transmission via a physical uplink shared channel in a second time slot different from the first time slot; and, in a second step, receiving a response message corresponding to the first step, wherein the response message comprises a radio network temporary identifier.

In certain embodiments, the method <NUM> further comprises monitoring during a response window for the response message. In some embodiments, the radio network temporary identifier for the two-step random access channel procedure is calculated using a first formula, and a radio network temporary identifier for the four-step random access channel procedure is calculated using a second formula different from the first formula. In various embodiments, the uplink data transmission comprises a medium access control physical data unit.

In one embodiment, the method <NUM> further comprises storing the medium access control physical data unit in a buffer. In certain embodiments, the medium access control physical data unit is stored in the buffer in response to switching from the two-step random access channel procedure to the four-step random access channel procedure. In some embodiments, the method <NUM> further comprises delaying for an offset time between transmission of the preamble and transmission of the uplink data transmission.

In various embodiments, the offset time corresponds to a subcarrier spacing. In one embodiment, determining whether to perform the two-step random access channel procedure or the four-step random access channel procedure comprises determining whether to perform the two-step random access channel procedure or the four-step random access channel procedure based on a predetermined factor. In certain embodiments, the predetermined factor comprises a power status.

In some embodiments, the method <NUM> further comprises receiving information configuring a requirement for performing the two-step random access channel procedure. In various embodiments, the information indicates that the two-step random access channel procedure is allowed. In one embodiment, the information indicates that the two-step random access channel procedure is required.

<FIG> is a flow chart diagram illustrating another embodiment of a method <NUM> for performing a two-step random access channel procedure. In some embodiments, the method <NUM> is performed by an apparatus, such as the network unit <NUM>. In certain embodiments, the method <NUM> may 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 method <NUM> may include receiving <NUM> a preamble in a first time slot and receiving an uplink data transmission via a physical uplink shared channel in a second time slot different from the first time slot in response to a determination by a remote unit to perform a two-step random access channel procedure. In some embodiments, the method <NUM> includes transmitting <NUM> a response message corresponding to the preamble, wherein the response message comprises a radio network temporary identifier.

In certain embodiments, the radio network temporary identifier for the two-step random access channel procedure is calculated using a first formula, and a radio network temporary identifier for a four-step random access channel procedure is calculated using a second formula different from the first formula. In some embodiments, the uplink data transmission comprises a medium access control physical data unit. In various embodiments, an offset time delay is between receiving the preamble and receiving the uplink data transmission.

In one embodiment, the offset time corresponds to a subcarrier spacing. In certain embodiments, the method <NUM> further comprises transmitting information configuring a requirement for performing the two-step random access channel procedure. In some embodiments, the information indicates that the two-step random access channel procedure is allowed. In various embodiments, the information indicates that the two-step random access channel procedure is required.

Claim 1:
A method (<NUM>) performed by a user equipment, UE, the method (<NUM>) comprising:
determining (<NUM>) whether to perform a two-step random access channel procedure or a four-step random access channel procedure; and
in response to determining to perform the two-step random access channel procedure (<NUM>):
in a first step:
transmitting a preamble in a first time slot; and
transmitting an uplink data transmission via a physical uplink shared channel, PUSCH, in a second time slot different from the first time slot, wherein the second time slot is a time offset later than the first time slot, wherein the time offset corresponds to a subcarrier spacing; and
in a second step:
receiving a response message corresponding to the first step, wherein the response message comprises a radio network temporary identifier, RNTI, wherein the RNTI for the two-step random access channel procedure is calculated using a first formula, and an RNTI for the four-step random access channel procedure is calculated using a second formula different from the first formula.