Patent Description:
Wireless communication systems are rapidly growing in usage. Further, wireless communication technology has evolved from voice-only communications to also include the transmission of data, such as Internet and multimedia content. Random access procedures may typically include four messages (e.g., four steps, e.g., <NUM>-step RA or <NUM>-step RACH). Techniques for random access with two messages (e.g., <NUM>-step RACH) are in development, however improvements in the field are desired.

While the features described herein may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to be limiting to the particular form disclosed, but on the contrary, the intention is to cover all modifications and alternatives falling within the scope of the subject matter as defined by the appended claims.

As shown, the example wireless communication system includes a base station <NUM> which communicates over a transmission medium with one or more user devices 106A, 106B, etc., through 106N.

The base station (BS) <NUM> may be a base transceiver station (BTS) or cell site (a "cellular base station"), and may include hardware that enables wireless communication with the UEs 106A through 106N.

The communication area (or coverage area) of the base station may be referred to as a "cell. " The base station <NUM> and the UEs <NUM> may be configured to communicate over the transmission medium using any of various radio access technologies (RATs), also referred to as wireless communication technologies, or telecommunication standards, such as GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces), LTE, LTE-Advanced (LTE-A), <NUM> new radio (<NUM> NR), HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), etc. Note that if the base station <NUM> is implemented in the context of LTE, it may alternately be referred to as an 'eNodeB' or 'eNB'. Note that if the base station <NUM> is implemented in the context of <NUM> NR, it may alternately be referred to as 'gNodeB' or 'gNB'.

As shown, the base station <NUM> may also be equipped to communicate with a network <NUM> (e.g., a core network of a cellular service provider, a telecommunication network such as a public switched telephone network (PSTN), and/or the Internet, among various possibilities). Thus, the base station <NUM> may facilitate communication between the user devices and/or between the user devices and the network <NUM>. In particular, the cellular base station <NUM> may provide UEs <NUM> with various telecommunication capabilities, such as voice, SMS and/or data services.

Base station <NUM> and other similar base stations operating according to the same or a different cellular communication standard may thus be provided as a network of cells, which may provide continuous or nearly continuous overlapping service to UEs 106A-N and similar devices over a geographic area via one or more cellular communication standards.

Thus, while base station <NUM> may act as a "serving cell" for UEs 106A-N as illustrated in <FIG>, each UE <NUM> may also be capable of receiving signals from (and possibly within communication range of) one or more other cells (which might be provided by other base stations 102B-N), which may be referred to as "neighboring cells".

In some embodiments, a gNB may be connected to a legacy evolved packet core (EPC) network and/or to a NR core (NRC) network. In addition, a gNB cell may include one or more transition and reception points (TRPs).

Note that a UE <NUM> may be capable of communicating using multiple wireless communication standards. For example, the UE <NUM> may be configured to communicate using a wireless networking (e.g., Wi-Fi) and/or peer-to-peer wireless communication protocol (e.g., Bluetooth, Wi-Fi peer-to-peer, etc.) in addition to at least one cellular communication protocol (e.g., GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces), LTE, LTE-A, <NUM> NR, HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), etc.). The UE <NUM> may also or alternatively be configured to communicate using one or more global navigational satellite systems (GNSS, e.g., GPS or GLONASS), one or more mobile television broadcasting standards (e.g., ATSC-M/H), and/or any other wireless communication protocol, if desired. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

<FIG> illustrates user equipment <NUM> (e.g., one of the devices 106A through 106N) in communication with a base station <NUM>, according to some embodiments. The UE <NUM> may be a device with cellular communication capability such as a mobile phone, a hand-held device, a computer or a tablet, or virtually any type of wireless device.

The UE <NUM> may include one or more antennas for communicating using one or more wireless communication protocols or technologies. In some embodiments, the UE <NUM> may be configured to communicate using, for example, CDMA2000 (1xRTT / 1xEV-DO / HRPD / eHRPD) or LTE using a single shared radio and/or GSM or LTE using the single shared radio. The shared radio may couple to a single antenna, or may couple to multiple antennas (e.g., for multiple-input, multiple-output or "MIMO") for performing wireless communications. In general, a radio may include any combination of a baseband processor, analog RF signal processing circuitry (e.g., including filters, mixers, oscillators, amplifiers, etc.), or digital processing circuitry (e.g., for digital modulation as well as other digital processing). Similarly, the radio may implement one or more receive and transmit chains using the aforementioned hardware. For example, the UE <NUM> may share one or more parts of a receive and/or transmit chain between multiple wireless communication technologies, such as those discussed above.

In some embodiments, the UE <NUM> may include any number of antennas and may be configured to use the antennas to transmit and/or receive directional wireless signals (e.g., beams). Similarly, the BS <NUM> may also include any number of antennas and may be configured to use the antennas to transmit and/or receive directional wireless signals (e.g., beams). To receive and/or transmit such directional signals, the antennas of the UE <NUM> and/or BS <NUM> may be configured to apply different "weight" to different antennas. The process of applying these different weights may be referred to as "precoding".

<FIG> illustrates an example simplified block diagram of a communication device <NUM>, according to some embodiments. It is noted that the block diagram of the communication device of <FIG> is only one example of a possible communication device. According to embodiments, communication device <NUM> may be a user equipment (UE) device, a mobile device or mobile station, a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (e.g., a laptop, notebook, or portable computing device), a tablet and/or a combination of devices, among other devices. As shown, the communication device <NUM> may include a set of components <NUM> configured to perform core functions. For example, this set of components may be implemented as a system on chip (SOC), which may include portions for various purposes. Alternatively, this set of components <NUM> may be implemented as separate components or groups of components for the various purposes. The set of components <NUM> may be coupled (e.g., communicatively; directly or indirectly) to various other circuits of the communication device <NUM>.

As shown, the SOC <NUM> may include processor(s) <NUM>, which may execute program instructions for the communication device <NUM> and display circuitry <NUM>, which may perform graphics processing and provide display signals to the display <NUM>. The processor(s) <NUM> may also be coupled to memory management unit (MMU) <NUM>, which may be configured to receive addresses from the processor(s) <NUM> and translate those addresses to locations in memory (e.g., memory <NUM>, read only memory (ROM) <NUM>, NAND flash memory <NUM>) and/or to other circuits or devices, such as the display circuitry <NUM>, short range wireless communication circuitry <NUM>, cellular communication circuitry <NUM>, connector I/F <NUM>, and/or display <NUM>. The MMU <NUM> may be configured to perform memory protection and page table translation or set up. In some embodiments, the MMU <NUM> may be included as a portion of the processor(s) <NUM>.

As noted above, the communication device <NUM> may be configured to communicate using wireless and/or wired communication circuitry. The communication device <NUM> may be configured to transmit a request to attach to a first network node operating according to the first RAT and transmit an indication that the wireless device is capable of maintaining substantially concurrent connections with the first network node and a second network node that operates according to the second RAT. The wireless device may also be configured transmit a request to attach to the second network node. The request may include an indication that the wireless device is capable of maintaining substantially concurrent connections with the first and second network nodes. Further, the wireless device may be configured to receive an indication that dual connectivity (DC) with the first and second network nodes has been established.

As described herein, the communication device <NUM> may include hardware and software components for implementing features for using multiplexing to perform transmissions according to multiple radio access technologies in the same frequency carrier (e.g., and/or multiple frequency carriers), as well as the various other techniques described herein. The processor <NUM> of the communication device <NUM> may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor <NUM> may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor <NUM> of the communication device <NUM>, in conjunction with one or more of the other components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be configured to implement part or all of the features described herein.

Further, as described herein, cellular communication circuitry <NUM> and short range wireless communication circuitry <NUM> may each include one or more processing elements and/or processors. In other words, one or more processing elements/processors may be included in cellular communication circuitry <NUM> and, similarly, one or more processing elements/processors may be included in short range wireless communication circuitry <NUM>. Thus, cellular communication circuitry <NUM> may include one or more integrated circuits (ICs) that are configured to perform the functions of cellular communication circuitry <NUM>. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of cellular communication circuitry <NUM>. Similarly, the short range wireless communication circuitry <NUM> may include one or more ICs that are configured to perform the functions of short range wireless communication circuitry <NUM>. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of short range wireless communication circuitry <NUM>.

The radio <NUM> and at least one antenna <NUM> may be configured to operate as a wireless transceiver and may be further configured to communicate with UE devices <NUM>. The antenna <NUM> may communicate with the radio <NUM> via communication chain <NUM>.

In addition, as described herein, processor(s) <NUM> may include one or more processing elements.

Further, as described herein, radio <NUM> may include one or more processing elements.

<FIG> illustrates an example simplified block diagram of cellular communication circuitry, according to some embodiments. It is noted that the block diagram of the cellular communication circuitry of <FIG> is only one example of a possible cellular communication circuit; other circuits, such as circuits including or coupled to sufficient antennas for different RATs to perform uplink activities using separate antennas, are also possible. According to embodiments, cellular communication circuitry <NUM> may be included in a communication device, such as communication device <NUM> described above. As noted above, communication device <NUM> may be a user equipment (UE) device, a mobile device or mobile station, a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (e.g., a laptop, notebook, or portable computing device), a tablet and/or a combination of devices, among other devices.

The cellular communication circuitry <NUM> may couple (e.g., communicatively; directly or indirectly) to one or more antennas, such as antennas 335a-b and <NUM> as shown (in <FIG>). In some embodiments, cellular communication circuitry <NUM> may include dedicated receive chains (including and/or coupled to, e.g., communicatively; directly or indirectly. For example, as shown in <FIG>, cellular communication circuitry <NUM> may include a modem <NUM> and a modem <NUM>. Modem <NUM> may be configured for communications according to a first RAT, e.g., such as LTE or LTE-A, and modem <NUM> may be configured for communications according to a second RAT, e.g., such as <NUM> NR.

In some embodiments, the cellular communication circuitry <NUM> may be configured to transmit, via the first modem while the switch is in the first state, a request to attach to a first network node operating according to the first RAT and transmit, via the first modem while the switch is in a first state, an indication that the wireless device is capable of maintaining substantially concurrent connections with the first network node and a second network node that operates according to the second RAT. The wireless device may also be configured transmit, via the second radio while the switch is in a second state, a request to attach to the second network node. The request may include an indication that the wireless device is capable of maintaining substantially concurrent connections with the first and second network nodes. Further, the wireless device may be configured to receive, via the first radio, an indication that dual connectivity with the first and second network nodes has been established.

As described herein, the modem <NUM> may include hardware and software components for implementing features for using multiplexing to perform transmissions according to multiple radio access technologies in the same frequency carrier, as well as the various other techniques described herein. The processors <NUM> may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor <NUM> may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor <NUM>, in conjunction with one or more of the other components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be configured to implement part or all of the features described herein.

In some embodiments, processor(s) <NUM>, <NUM>, etc. may be configured to implement or support implementation of part or all of the methods described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively, the processor(s) <NUM>, <NUM>, etc. may be configured as a programmable hardware element, such as an FPGA, or as an ASIC, or a combination thereof. In addition, as described herein, processor(s) <NUM>, <NUM>, etc. may include one or more processing elements. Thus, processor(s) <NUM>, <NUM>, etc. may include one or more integrated circuits (ICs) that are configured to perform the functions of processor(s) <NUM>, <NUM>, etc. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processor(s) <NUM>, <NUM>, etc..

In some implementations, fifth generation (<NUM>) wireless communication will initially be deployed concurrently with other wireless communication standards (e.g., LTE). For example, whereas <FIG> illustrates a possible standalone (SA) implementation of a next generation core (NGC) network <NUM> and <NUM> NR base station (e.g., gNB <NUM>), dual connectivity between LTE and <NUM> new radio (<NUM> NR or NR), such as in accordance with the exemplary non-standalone (NSA) architecture illustrated in <FIG>, has been specified as part of the initial deployment of NR. Thus, as illustrated in <FIG>, evolved packet core (EPC) network <NUM> may continue to communicate with current LTE base stations (e.g., eNB <NUM>). In addition, eNB <NUM> may be in communication with a <NUM> NR base station (e.g., gNB <NUM>) and may pass data between the EPC network <NUM> and gNB <NUM>. In some instances, the gNB <NUM> may also have at least a user plane reference point with EPC network <NUM>. Thus, EPC network <NUM> may be used (or reused) and gNB <NUM> may serve as extra capacity for UEs, e.g., for providing increased downlink throughput to UEs. In other words, LTE may be used for control plane signaling and NR may be used for user plane signaling. Thus, LTE may be used to establish connections to the network and NR may be used for data services. As will be appreciated, numerous other non-standalone architecture variants are possible.

A <NUM>-step random access (RA) procedure (e.g., random access channel (RACH)) may be used to initiate, resume, setup, or reestablish a connection (e.g., a radio resource control (RRC) connection) between a UE and a BS, e.g., in LTE. Newer wireless standards, e.g., NR, may seek to reduce latency and/or signaling overhead by using a <NUM>-step RA procedure, under at least some circumstances. However, various features of <NUM>-step RA procedures have not yet been determined. For example, downlink (DL) radio resource control (RRC) message transmission procedures are not currently resolved for <NUM>-step RA procedures.

<FIG> is a communication flow diagram which illustrates exemplary techniques for performing transmission of DL RRC messages and/or other connection configuration messages in association with <NUM>-step RA. Aspects of the method of <FIG> may be implemented by a network including one or more base stations (e.g., BS <NUM>) in communication with one or more wireless device, such as the UE(s) <NUM>, as illustrated in and described with respect to the Figures, or more generally in conjunction with any of the computer circuitry, systems, devices, elements, or components shown in the Figures, among other devices, as desired. For example, a processor (or processors) of the UE (e.g., processor(s) <NUM>, processor(s) associated with communication circuitry <NUM> or <NUM> such as processor(s) <NUM> and/or <NUM>, etc.), base station (e.g., processor(s) <NUM>, or a processor associated with radio <NUM> and/or communication chain <NUM>, among various possibilities), or network element (e.g., any component of NGC <NUM>, EPC <NUM>, etc.) may cause the UE or base station to perform some or all of the illustrated method elements. Note that while at least some elements of the method are described in a manner relating to the use of communication techniques and/or features associated with 3GPP specification documents, such description is not intended to be limiting to the disclosure, and aspects of the method may be used in any suitable wireless communication system, as desired. Further, the method may be applied in other contexts (e.g., between multiple UEs, e.g., in device-to-device communications). In various embodiments, some of the elements of the methods shown may be performed concurrently, in a different order than shown, may be substituted for by other method elements, or may be omitted. Additional method elements may also be performed as desired. As shown, the method may operate as follows.

A BS <NUM> transmits system information about a network, e.g., a cellular network, according to the invention (<NUM>). A user equipment device (e.g., UE <NUM>) may detect the network, e.g., based on the system information. The UE may determine configuration information related to performing random access (RA) with the network. For example, the BS may broadcast and the UE may receive one or more system information blocks (SIB) such as SIB1 transmitted by the BS which may include the RA configuration information. The RA configuration information may include condition configuration information and/or RA procedure configuration information, among various possibilities. The RA configuration information may apply to <NUM>-step RA and/or <NUM>-step RA.

The RA procedure configuration information may indicate resources and/or a transmission scheme (e.g., or schemes) for a downlink RRC message or messages and/or other connection configuration message(s), e.g., which may be transmitted by the BS to the UE based on a successful RA procedure. For example, the RA procedure configuration information may indicate any of the various transmission schemes described herein, e.g., with respect to <NUM> below and/or subsequent Figures.

The RA procedure configuration information may indicate resources (e.g., time and/or frequency resources on a physical random access channel (PRACH)) for use for transmitting and receiving RA messages. The RA configuration may identify resources for any of various RA messages, including message <NUM> (Msg1), Msg2, Msg3, Msg4, MsgA, and/or MsgB. Msg1-Msg4 (described with reference to, for example, <FIG>) may be useful for <NUM>-step RA and MsgA and MsgB (described with reference to, for example, <FIG>) may be useful for <NUM>-step RA.

Based on the RA procedure configuration and/or other factors (e.g., application traffic activity, measurements, etc.) the UE <NUM> may determine to perform a <NUM>-step RA procedure and transmits a MsgA to the BS <NUM> (<NUM>), according to the invention. The MsgA may utilize a preamble according to the RA configuration information. The MsgA may also include control information. MsgA is further described below with respect to <FIG>.

In response to the MsgA, the BS <NUM> transmits MsgB to the UE <NUM> (<NUM>), according to the invention. The MsgB includes a response to the MsgA. Such a response to MsgA (e.g., a random access response (RAR)) may include: an indication of success, an indication to fallback to a <NUM>-step RA procedure (e.g., in response to MsgA being incompletely received by the BS <NUM>), and/or a backoff indication (e.g., signaling the UE to attempt random access again). MsgB is further described below with respect to <FIG>.

The BS <NUM> may transmit a downlink (DL) RRC message and/or other connection configuration message(s) to the UE <NUM> (<NUM>), according to some embodiments. The BS <NUM> may transmit the connection configuration message(s) to the UE in a manner indicated in the RA configuration information. For example, the BS may transmit the message(s) using time and frequency resources consistent with an indication transmitted as system information. The UE <NUM> may determine the time and frequency resources to receive the connection configuration message(s) according to such RA configuration information or other system information.

The DL RRC message may be an RRC setup message, among various possibilities. More generally, the connection configuration message may indicate to the UE one or more parameters or settings to configure the connection between the UE and the BS <NUM>. The DL RRC message and/or other connection configuration message(s) may be transmitted subsequent to MsgB or concurrently with MsgB (e.g., multiplexed with MsgB), among other possibilities.

According to various embodiments, the DL RRC message and/or other connection configuration message(s) may be group-cast (e.g., multiple respective messages to corresponding respective UEs may be multiplexed together) or may be unicast (e.g., a message may be sent to an individual UE using a dedicated transmission).

In the case of a unicast transmission, the DL RRC message and/or other connection configuration message(s) may be transmitted under any of the following conditions, among various possibilities. The BS <NUM> may transmit the message after receiving an acknowledgement (e.g., ACK) from the UE of MsgB, e.g., indicating successful reception of MsgB. The BS <NUM> may transmit the message without (e.g., or prior to) receiving such an ACK. The BS <NUM> may transmit the message according to a DL resource assignment that may be included in MsgB or transmitted at a fixed time, among various possibilities. In some embodiments, the DL resource assignment may be indicated in a PDCCH. The BS <NUM> may transmit the message at a fixed time (e.g., a certain period of time after transmitting the MsgB or a certain period of time after receiving MsgA). For example, the time and frequency resources used for transmission of the DL RRC message and/or other connection configuration message(s) may be indicated in RA configuration information. A unicast (e.g., dedicated) transmission of the message (e.g., according to any of the options described herein) may provide for HARQ acknowledgement (e.g., and retransmission, if needed) of the message.

In the case of a group-cast transmission, the BS <NUM> may transmit the message multiplexed with responses to MsgA included in MsgB. In other words, MsgB may be multiplexed with the DL RRC message and/or other connection configuration message(s) to various UEs. For example, each response indicating successful random access may optionally include a corresponding DL RRC message and/or other connection configuration message. As another example, a new type of media access control (MAC) sub protocol data unit (subPDU) may be introduced to include the DL RRC message and/or other connection configuration message, e.g., an RRC-Msg MAC subPDU. The RRC-Msg MAC subPDU may be next to (e.g., successively follow, e.g., as illustrated in <FIG>) a corresponding response or may be located after all responses (e.g., as illustrated in <FIG>).

Retransmission of such multiplexed configuration messages may be handled by RACH retransmission, e.g., started from MsgA. In other words, if the UE does not successfully receive the DL RRC message and/or other connection configuration message, the UE may restart the RA process by transmitting (e.g., retransmitting) MsgA. Alternatively, the UE may fallback to <NUM>-step RA, e.g., by transmitting Msg3.

In another example of group-cast transmission, the BS <NUM> may transmit a dedicated MAC PDU including the DL RRC message and/or other connection configuration messages for any number of UEs. For example, the BS may transmit a dedicated RRC-msg type MAC PDU, e.g., subsequent to transmission of corresponding MsgB for the UE(s). In such a dedicated MAC PDU any number of configuration messages (e.g., RRC-Msg MAC subPDUs) may be concatenated. Such a message may be scheduled via RA-RNTI. Retransmission may be scheduled via T-C-RNTI, e.g., as allocated in MsgB-RAR.

<FIG> illustrates aspects of <NUM>-step RA, according to some embodiments. A UE (e.g., UE <NUM>) may transmit a RA preamble to a gNB (e.g., BS <NUM>) (<NUM>). The preamble may be referred to as Msg1 (e.g., message <NUM>). Physical RA channel (PRACH) resource/preamble may be configured via system information block <NUM> (SIB1) or RRC dedicated signaling. Multiple preambles may be transmitted on one PRACH resource. The UE may select the PRACH occasion and preamble for Msg1 transmission.

The BS <NUM> may respond to the preamble with a RA response (RAR) (<NUM>). The RAR may be referred to as Msg2. Msg2 may be transmitted using a RA radio network temporary identifier (RA-RNTI) associated with the PRACH occasion in which the preamble is transmitted. In other words, the Msg2 may be scheduled via a physical downlink control channel (PDCCH) with the RA RNTI.

In some embodiments, the RA-RNTI may be calculated based on various factors such as: a symbol index (e.g., the index of the first OFDM symbol of the PRACH occasion, a slot index (e.g., the index of the first slot of the PRACH occasion in a system frame, a frequency index (e.g., the index of the PRACH occasion in the frequency domain, and an index of the carrier used for transmitting the preamble. The UE may monitor the physical downlink control channel (PDCCH) masked by RA-RNTI within a RAR window (e.g., from the time of the transmission of the preamble). Based on detecting its preamble (e.g., RAPID) in the RAR, the UE may consider Msg2 reception successful.

Msg2 may include: an uplink (UL) grant for Msg3, a timing advance (TA) command, and a temporary cell radio network temporary identifier (T-C-RNTI). The TA command may serve to synchronize the UE and the network.

In some embodiments, Msg2 transmission may be group-cast and scheduled by RA-RNTI. In other words, the BS <NUM> may multiplex RAR for multiple UEs in a single message (e.g., a MAC PDU containing respective subPDUs for each of multiple respective UEs). Thus, Msg2 may not be configured to support retransmissions, e.g., via hybrid automatic repeat request (HARQ).

The UE may respond to the RAR with a scheduled transmission (<NUM>). The scheduled transmission may be referred to as Msg3. The UE may transmit Msg3 according to the UL grant in the RAR (e.g., in Msg2). The UE may monitor PDCCH masked by T-C-RNTI for potential Msg3 retransmission (e.g., for an indication from the BS to retransmit Msg3).

In some embodiments, the Msg3 may include a logical channel identifier (LCID) and a common control channel (CCCH) service data unit (SDU) and/or a media access control (MAC) protocol data unit (PDU), among various possibilities.

The BS <NUM> may respond to Msg3 with a contention resolution (CR) (<NUM>). The CR (e.g., a CR MAC control element (CE)) may be referred to as Msg4. In some embodiments, Msg4 may also include a first DL RRC message, e.g., in addition to the CR. In other words, the DL RRC message may be multiplexed in Msg4.

The BS <NUM> may transmit Msg4 via a unicast transmission (e.g., a transmission dedicated to an individual UE). The unicast transmission may be scheduled by T-C-RNTI and may support HARQ retransmission, according to some embodiments. A UE may monitor PDCCH masked by T-C-RNTI and/or C-RNTI. If a CR is received the RA procedure may be a success.

The (e.g., first) DL RRC message may include any of: RRC reject, RRC setup, RRC reestablishment, and/or RRC resume messages, among various possibilities. Including the DL RRC message with the Msg4 may reduce the latency of the RRC procedure (e.g., may enable the UE to receive the RRC message and perform RRC configuration sooner relative to a case in which the DL RRC message is transmitted subsequent to the Msg4).

Following reception of the first RRC message, the UE may operate as indicated in the RRC message.

<FIG> illustrates an exemplary <NUM>-step RA procedure, e.g., for initial access, according to some embodiments. A <NUM>-step RA procedure may include MsgA (e.g., similar to Msg1 combined with Msg3) and MsgB (e.g., similar to Msg2 combined with Msg4).

A UE (e.g., UE <NUM>) transmits MsgA to a BS (e.g., BS <NUM>) (<NUM>). The MsgA may include a preamble (<NUM>) and a CCCH MAC CE transmitted on a PUSCH (<NUM>). The preamble and MAC PDU may be transmitted concurrently or sequentially (e.g., with or without a time interval in between the transmissions) on one or more frequencies. Based on determining to perform a <NUM>-step RA procedure, the UE may select the next available PRACH resource, and may (e.g., randomly) select a preamble for transmission of MsgA (<NUM>).

After transmitting MsgA, the UE may start monitoring for MsgB within a <NUM>-step RAR window. The <NUM>-step RAR window may be determined based on received RA configuration information, network configuration, definitions in a standard, etc. The BS responds with a MsgB (<NUM>), e.g., during the RAR window. MsgB may indicate success or fallback in the RAR. MsgB may multiplex RAR for multiple UEs. MsgB may include a PDCCH transmitted with a MsgB-RNTI (<NUM>) and a MsgB-MAC PDU (<NUM>). The MsgB-RNTI may be determined based on various factors such as: a symbol index (e.g., the index of the first OFDM symbol of the PRACH occasion, a slot index (e.g., the index of the first slot of the PRACH occasion in a system frame, a frequency index (e.g., the index of the PRACH occasion in the frequency domain, and an index of the carrier used for transmitting the preamble, and potentially the PUSCH info used by MsgA. The MsgB-MAC PDU may be scheduled according to a DL grant included in the PDCCH. The MsgB-MAC PDU may include the RAR.

In some embodiments, a SuccessRAR (e.g., an RAR indicating that the RA procedure is successful (e. g, MsgA received successfully by the BS) and that the UE may access the network) may include a contention resolution (CR) identifier (ID), C-RNTI, and a TA command. The CR ID may be used as an identifier for the UE, e.g., to resolve the contention(s) and assist a UE in determining whether an RAR is directed to itself. In some embodiments, a FallbackRAR (e.g., an RAR indicating that the MsgA was not successfully or completely received by the BS, and that the UE should fallback to a <NUM>-step RA procedure) may include: a RA preamble identifier (RAPID) (e.g., for the failed MsgA), a UL grant (e.g., for Msg3 transmission), T-C-RNTI, and a TA command. MsgB may additionally or alternatively include a backoff indicator (BI), e.g., to indicate to one or more UEs to attempt MsgA again after a backoff period.

<FIG> illustrates a MsgB MAC PDU, according to some embodiments. The BS may transmit a MAC PDU consisting of one or more MAC subPDUs. Each subPDU may include a subheader indicating whether the subPDU includes backoff indication (BI), a RA preamble (RAPID), and/or a RAR. In the illustrated example, subPDU <NUM> may include a MAC RAR, e.g., for a first UE <NUM>. MAC subPDUs <NUM>-n may include RARs for additional UEs. The exemplary, illustrated MsgB MAC RAR may include <NUM> octets. The first octet may include R (e.g., a reserved bit) and a timing advance (TA) command. The TA command may serve to synchronize the UE and the network. The second octet may include the remainder of the TA command and a portion of a grant, e.g., for UL and/or DL resources. The remainder of the grant may be included in octets <NUM>-<NUM>. The <NUM>th and <NUM>th octets may include a temporary cell radio network temporary identifier (T-C-RNTI). The remaining octets may include a UE CR ID. Based on detecting its preamble (e.g., RAPID) in the RAR, the UE may consider MsgB reception successful and may apply the timing advance value from the TA command for UL synchronization with the network.

<FIG> are communication flow diagrams illustrating exemplary processes for transmitting a first DL RRC message using a dedicated (e.g., unicast) transmission, according to some embodiments.

<FIG> illustrates examples in which the network sends (e.g., the BS <NUM> transmits) the first DL RRC message via a dedicated transmission separate from MsgB, according to some embodiments. Transmission of MsgA and MsgB may operate as illustrated in <FIG> and described with respect to <NUM>, <NUM>, <NUM>, and <NUM> (e.g., including <NUM> and <NUM>).

In some embodiments, the UE may transmit an acknowledgement (ACK) of the MsgB (<NUM>), and the BS may receive the acknowledgement.

The BS may transmit the RRC message to the UE (<NUM>). In some embodiments, transmitting the RRC message may be responsive to receiving the acknowledgement of MsgB. In some embodiments, transmitting the RRC message may be responsive to expiration of a timer (e.g., the RRC message may be transmitted a certain amount of time after transmission of MsgB.

Transmitting the RRC message to the UE may include transmitting a DL grant (<NUM>) to the UE. The DL grant may be transmitted on PDCCH resources according to T-C-RNTI. Transmitting the RRC message to the UE may also include transmitting an RRC setup message (<NUM>) to the UE. The RRC setup message may be transmitted on resources indicated in the DL grant, e.g., via PDSCH. It will be appreciated that HARQ retransmission may be applicable to the DL grant and RRC setup message; accordingly, <NUM>, <NUM>, and/or <NUM> may be repeated, if necessary (e.g., in response to a NACK or if no ACK is received).

<FIG> illustrates examples in which the network sends (e.g., the BS <NUM> transmits) the first DL RRC message via a dedicated transmission scheduled by MsgB, according to some embodiments. Transmission of MsgA may operate as illustrated in <FIG> and described with respect to <NUM>, <NUM>, and <NUM>. Transmission of MsgB may be similar to <NUM>, <NUM>, and <NUM>, however a DL grant may be included in the successRAR of MsgB (<NUM>). In other words, the MsgB-MAC PDU described above with respect to <NUM> and <FIG> may include a DL grant which identifies DL resources for the first DL RRC message. The first DL RRC message may be an RRC setup message transmitted on PDSCH resources identified by the DL grant (<NUM>). As noted above, HARQ retransmission may be applicable to the DL grant and RRC setup message; accordingly, retransmission (e.g., <NUM>, <NUM>, and/or <NUM>) may occur, if necessary (e.g., in response to a NACK or if no ACK is received). It will be appreciated that retransmission may not be needed and may not occur in some cases.

<FIG> illustrate aspects of exemplary processes for transmitting a first DL RRC message using a non-dedicated (e.g., group-cast or multi-cast) transmission, according to the invention.

<FIG> illustrate exemplary MAC PDUs, each including a plurality of MAC RARs, according to the invention. Such a MAC PDU is transmitted in MsgB. The MAC PDUs of <FIG> may be similar to that of <FIG>, in some regards. For example, each subPDU may include a header. Further, a plurality of subPDUs may include respective RARs (e.g., indicating success or failure of the RA process) for respective UEs.

As shown in <FIG>, a MAC PDU or subPDU including a successRAR (e.g., subPDU <NUM>, in the example) may optionally include an RRC message or other connection configuration message. The subheader of the subPDU indicates whether or not a DL RRC message and/or other connection configuration message(s) is included in the subPDU. The subheader of the subPDU may include a length indicator (LI). The LI may indicate the length of the subPDU. Based on the LI, a UE <NUM> may determine whether or not an RRC message is included in the subPDU and/or may determine the length of the RRC message if one is included. A MAC subPDU including a fallbackRAR may not include an RRC message. For example, a MAC PDU may include some subPDUs which indicate successful random access attempts and other subPDUs which indicate RA failure (e.g., fallback RAR). The subPDUs indicating success may include respective RRC messages and the subPDUs indicating RA failure may not include RRC messages, according to some embodiments.

<FIG> illustrate exemplary MAC PDUs which may include new MAC subPDU types, introduced to include an RRC message multiplexed with RAR in MsgB, according to the invention. <FIG> illustrates that an RRC message MAC sub PDU (e.g., RRC-Msg Type MAC subPDU) may be next to (e.g., may immediately follow) a subPDU with an associated successRAR. Thus, in the illustrative example, subPDU <NUM> may include a successRAR for a first UE and subPDU <NUM> may include a subPDU of a new type including the RRC message. As shown, the new type of subPDU may include a subheader followed by the RRC message. In some embodiments, the subheader may not include the RAPID, e.g., because the RAPID of the corresponding successRAR PDU may identify the UE for which the RRC message is intended. The intended UE may determine that the subPDU following its successRAR is directed to it, and may therefore receive and decode the RRC-Msg MAC subPDU corresponding to its RAPID.

<FIG> illustrates that an RRC message MAC sub PDU (e.g., RRC-Msg Type MAC subPDU) may follow all RAR type MAC subPDUs. Thus, in the illustrative example MAC subPDU3 may include a successRAR for a first UE. MAC subPDU3 may be followed by any number of subPDUs containing RARs for other UEs and/or RRC messages for other UEs. MAC subPDU n may be an RRC-Msg type subPDU for the first UE (e.g., corresponding to MAC subPDU <NUM>). The RRC-Msg type subPDU may be identified by a RAPID in the subheader and, based on the RAPID, a UE may determine whether it is the UE for which the RRC-Msg type subPDU is intended. Any number of RRC-Msg type subPDUs may be included in a MsgB MAC PDU.

<FIG> is a communication flow diagram illustrating a <NUM>-step RA process and transmission of a dedicated MAC PDU including RRC messages for one or more UEs (e.g., an RRC-Msg MAC PDU), according to some embodiments. Transmission of MsgA and MsgB may operate as illustrated in <FIG> and described with respect to <NUM>, <NUM>, <NUM>, and <NUM> (e.g., including <NUM> and <NUM>). Following transmission of MsgB, the BS <NUM> may transmit an RRC message MAC PDU (<NUM>). The RRC message MAC PDU may be scheduled via RA-RNTI. RRC messages for any number of UEs may be concatenated together in the MAC PDU as illustrated in <FIG>. For example, respective subPDUs may include RRC messages for corresponding respective UEs. It will be appreciated that the RRC-Msg MAC PDU may include RRC setup messages for any number (e.g., one or more) of UEs.

A UE may consider the RA process to be a success based on receiving the MsgB, e.g., regardless of whether the RRC-Msg MAC PDU is received. In the event that the RRC-Msg MAC PDU is not received, a UE may request retransmission (<NUM>), e.g., the UE may send a negative acknowledgement (NACK). In response to such a request, the BS may perform retransmission of the RRC-Msg MAC PDU (<NUM>), including sending a DL grant (e.g., using PDCCH scheduled by T-C-RNTI) (<NUM>) and may resend the (e.g., UE-specific) RRC setup message on PDSCH resources according to the DL grant (<NUM>). It will be appreciated that retransmission may not be performed in some cases, e.g., when the initial RRC-Msg MAC PDU is received by the UE(s).

Claim 1:
A method for operating a base station (<NUM>), the method comprising:
at the base station (<NUM>)
transmitting (<NUM>) random access configuration information for <NUM>-step random access;
receiving (<NUM>), from a plurality user equipment devices, UEs (<NUM>), a first plurality of initial messages of <NUM>-step random access, MsgA, according to the random access configuration information for <NUM>-step random access; and
transmitting, to the plurality of UEs (<NUM>), a plurality of corresponding responses to the first plurality of initial messages of <NUM>-step random access, MsgA, the responses comprising:
a first response message for a first UE of the plurality of UEs, the first response message including a fallback random access response, RAR;
a second response message for a second UE of the plurality of UEs, the second response message including a success RAR and a subheader indicating whether or not a downlink, DL, radio resource control, RRC, message is included in the second response message, wherein the DL RRC message is in a sub protocol data unit, subPDU, of a protocol data unit, PDU, wherein the subPDU associated with the DL RRC message successively follows the subheader and the success RAR.