Patent Description:
Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.).

<NPL>") discusses details on SUL, single active UL and uplink alignment between LTE and NR. <NPL>") considers a scenario in which LTE UL and NR UL are coexisting on the bandwidth of an LTE FDD component carrier F1, LTE DL on a paired frequency F3 and NR DL transmission on frequency F2. <NPL>") is a summary of an email discussion on [95bis#<NUM>] [LTE/NB-IoT] relating to RACH on non-anchor carriers. <NPL>") discusses NPRACH on non-anchor carriers and makes proposals to address open issues including configuration, measurement and carrier selection. <NPL>") discusses the handover execution procedure, especially on the contents of the handover command (including beam related information) and UE actions to access the target cell. For NR, suitable beam is defined by a minimum quality threshold, which is either specified or signalled from the network.

A UE may perform a RACH procedure to synchronize with a BS in an uplink direction. For example, the UE may transmit a first message (e.g., a random access preamble) on the uplink that includes a preamble identifier and a random access radio network temporary identifier (RA-RNTI). The UE may listen for a second message from the BS (e.g., a random access response or RAR) that identifies a grant of resources reserved for the UE, along with a timing advance, the preamble identifier, transmit power control (TPC) information, and a temporary cell RNTI (T-C-RNTI or TC-RNTI) requesting for the UE to transmit a radio resource control (RRC) connection request. After receiving the second message, the UE may transmit the RRC connection request on the resources as a third message, and may receive, from the BS, a permanent identifier (e.g., a C-RNTI). Thus, synchronization is performed and an RRC connection is established in the uplink direction. Synchronization may be performed in the downlink direction (e.g., synchronization of the UE with the network) using the PSS and SSS transmitted by the BS before the RACH procedure is performed.

A UE, such as a UE using a NR radio access technology (RAT), uses a supplementary uplink (SUL) configuration. In a SUL configuration, the UE connects to a primary uplink carrier at a first frequency band, and connects to a supplementary uplink carrier at a second frequency band different from the first frequency band. In some aspects, the first frequency band may be a time division duplexing (TDD) frequency band or a frequency division duplexing (FDD) frequency band. In some aspects, the second frequency band may be a TDD frequency band, may be an FDD frequency band, or may be an uplink-only frequency band. Additionally, or alternatively, the first frequency band and/or the second frequency band may be associated with respective downlink carriers. The primary uplink carrier and the downlink carrier of the first frequency band may be termed a first set of carriers, and the supplementary uplink carrier and the downlink carrier (when present) of the second frequency band may be termed a second set of carriers.

One advantage of using SUL is that the second set of carriers, of the second frequency band, may have better coupling loss than the first set of carriers due to a lower path loss and a smaller penetration loss. This may provide improved range and uplink performance on the second frequency band. Also, the second frequency band may be narrower than the first frequency band, so for a UE with a limited bandwidth requirement (e.g., based at least in part on link budget or packet size), it may be more spectrally efficient to use the second frequency band.

However, SUL may lead to certain difficulties for RACH configuration of the UE <NUM>. For example, the first set of carriers and the second set of carriers may have different uplink coverage due to a difference in coupling loss between the first set of carriers and the second set of carriers. Furthermore, the supplementary uplink carrier may have less accurate RACH open loop power control than the primary uplink carrier. For example, the supplementary uplink carrier may not have a paired downlink carrier, or, if the supplementary uplink carrier has a paired downlink carrier, the UE <NUM> may not measure or connect to the paired downlink carrier. Therefore, it may be difficult to provide RACH configuration information for the second set of carriers and, thus, it may be difficult to perform RACH configuration of the second set of carriers.

Techniques and apparatuses described herein may provide RACH configuration information for the second set of carriers on a downlink carrier of the first set of carriers, and may selectively perform a RACH procedure with regard to the first set of carriers or the second set of carriers, wherein the RACH procedure is performed using the RACH configuration information. For example, when the UE is capable of using the second set of carriers as a supplementary uplink carrier, the UE may transmit uplink RACH messages (e.g., the first and third messages) using the second set of carriers. In some aspects, the UE may interpret the RACH configuration information and/or a second message of the RACH procedure differently for the supplementary uplink carrier than for the primary uplink carrier, which improves performance of the RACH procedure on the supplementary uplink carrier and mitigates inaccuracy in the RACH procedure caused by the difference in coupling loss between the primary uplink carrier and the supplementary uplink carrier. Thus, RACH performance is improved and RACH configuration of the UE using the supplementary uplink carrier is enabled.

These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements").

A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, a NR BS, a Node B, a gNB, a <NUM> NB, an access point, a transmit receive point (TRP), and/or the like.

A relay station may also be referred to as a relay BS, a relay base station, a relay, etc..

Wireless network <NUM> may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in wireless network <NUM>.

A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, etc. A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

MTC and eMTC UEs include, for example, robots, drones, remote devices, such as sensors, meters, monitors, location tags, etc., that may communicate with a base station, another device (e.g., remote device), or some other entity.

UEs may synchronize with a base station in the downlink direction based at least in part on synchronization signals transmitted by the base station, and may perform a random access procedure to synchronize with the base station in the uplink direction.

<FIG> shows a block diagram of a design of base station <NUM> and UE <NUM>, which may be one of the base stations and one of the UEs in <FIG>.

Transmit processor <NUM> may also process system information (e.g., for semi-static resource partitioning information (SRPI), etc.) and control information (e.g., CQI requests, grants, upper layer signaling, etc.) and provide overhead symbols and control symbols. Transmit processor <NUM> may also generate reference symbols for reference signals (e.g., the CRS) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS)).

A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), etc..

On the uplink, at UE <NUM>, a transmit processor <NUM> may receive and process data from a data source <NUM> and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, etc.) from controller/processor <NUM>. The symbols from transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM, etc.), and transmitted to base station <NUM>. In some aspects, the UE <NUM> may transmit a random access preamble to the base station <NUM>. In some aspects, base station <NUM> may provide a random access response based at least in part on a random access preamble received from the UE <NUM>. The random access response may identify characteristics of a radio resource control connection setup message and/or the like.

Controllers/processors <NUM> and <NUM> and/or any other component(s) in <FIG> may direct the operation at base station <NUM> and UE <NUM>, respectively, to perform supplementary uplink random access configuration. For example, controller/processor <NUM> and/or other processors and modules at UE <NUM>, may perform or direct operations of UE <NUM> to perform supplementary uplink random access configuration. For example, controller/processor <NUM> and/or other controllers/processors and modules at UE <NUM> may perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein. In some aspects, one or more of the components shown in <FIG> may be employed to perform example process <NUM> and/or other processes for the techniques described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively.

In some aspects, UE <NUM> may include means for receiving random access channel (RACH) configuration information on a downlink carrier of a first set of carriers, means for selectively performing a RACH procedure with regard to the first set of carriers or the second set of carriers based at least in part on the RACH configuration information, and/or the like. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>.

<FIG> shows an example frame structure <NUM> for frequency division duplexing (FDD) in a telecommunications system (e.g., LTE). Each radio frame may have a predetermined duration (e.g., <NUM> milliseconds (ms)) and may be partitioned into <NUM> subframes with indices of <NUM> through <NUM>. Each subframe may include two slots. Each radio frame may thus include <NUM> slots with indices of <NUM> through <NUM>. Each slot may include L symbol periods, e.g., seven symbol periods for a normal cyclic prefix (as shown in <FIG>) or six symbol periods for an extended cyclic prefix. The <NUM> symbol periods in each subframe may be assigned indices of <NUM> through <NUM>-<NUM>.

In certain telecommunications (e.g., LTE), a BS may transmit a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) on the downlink in the center of the system bandwidth for each cell supported by the BS. The PSS and SSS may be transmitted in symbol periods <NUM> and <NUM>, respectively, in subframes <NUM> and <NUM> of each radio frame with the normal cyclic prefix, as shown in <FIG>. The BS may transmit a cell-specific reference signal (CRS) across the system bandwidth for each cell supported by the BS. The CRS may be transmitted in certain symbol periods of each subframe and may be used by the UEs to perform channel estimation, channel quality measurement, and/or other functions. The BS may also transmit a physical broadcast channel (PBCH) in symbol periods <NUM> to <NUM> in slot <NUM> of certain radio frames. The PBCH may carry some system information. The BS may transmit other system information such as system information blocks (SIBs) on a physical downlink shared channel (PDSCH) in certain subframes. The BS may transmit control information/data on a physical downlink control channel (PDCCH) in the first B symbol periods of a subframe, where B may be configurable for each subframe. The BS may transmit traffic data and/or other data on the PDSCH in the remaining symbol periods of each subframe.

In other systems (e.g., such NR or <NUM> systems), a Node B may transmit these or other signals in these locations or in different locations of the subframe.

<FIG> shows two example subframe formats <NUM> and <NUM> with the normal cyclic prefix. Each resource block may cover <NUM> subcarriers in one slot and may include a number of resource elements. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value.

Subframe format <NUM> may be used for two antennas. A CRS may be transmitted from antennas <NUM> and <NUM> in symbol periods <NUM>, <NUM>, <NUM>, and <NUM>. A reference signal is a signal that is known a priori by a transmitter and a receiver and may also be referred to as a pilot signal. A CRS is a reference signal that is specific for a cell, e.g., generated based at least in part on a cell identity (ID). In <FIG>, for a given resource element with label Ra, a modulation symbol may be transmitted on that resource element from antenna a, and no modulation symbols may be transmitted on that resource element from other antennas. Subframe format <NUM> may be used with four antennas. A CRS may be transmitted from antennas <NUM> and <NUM> in symbol periods <NUM>, <NUM>, <NUM>, and <NUM> and from antennas <NUM> and <NUM> in symbol periods <NUM> and <NUM>. For both subframe formats <NUM> and <NUM>, a CRS may be transmitted on evenly spaced subcarriers, which may be determined based at least in part on cell ID. CRSs may be transmitted on the same or different subcarriers, depending on their cell IDs. For both subframe formats <NUM> and <NUM>, resource elements not used for the CRS may be used to transmit data (e.g., traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP Technical Specification <NUM>, entitled "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation," which is publicly available.

An interlace structure may be used for each of the downlink and uplink for FDD in certain telecommunications systems (e.g., LTE). For example, Q interlaces with indices of <NUM> through Q - <NUM> may be defined, where Q may be equal to <NUM>, <NUM>, <NUM>, <NUM>, or some other value. Each interlace may include subframes that are spaced apart by Q frames. In particular, interlace q may include subframes q, q + Q, q + 2Q, etc., where q ∈ {<NUM>,.

The wireless network may support hybrid automatic retransmission request (HARQ) for data transmission on the downlink and uplink. For HARQ, a transmitter (e.g., a BS) may send one or more transmissions of a packet until the packet is decoded correctly by a receiver (e.g., a UE) or some other termination condition is encountered. For synchronous HARQ, all transmissions of the packet may be sent in subframes of a single interlace. For asynchronous HARQ, each transmission of the packet may be sent in any subframe.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communication systems, such as NR or <NUM> technologies.

In aspects, NR may utilize OFDM with a CP (herein referred to as cyclic prefix OFDM or CP-OFDM) and/or SC-FDM on the uplink, may utilize CP-OFDM on the downlink and include support for half-duplex operation using time division duplexing (TDD).

A single component carrier bandwidth of <NUM> may be supported. NR resource blocks may span <NUM> sub-carriers with a sub-carrier bandwidth of <NUM> kilohertz (kHz) over a <NUM> duration. Each radio frame may include <NUM> subframes with a length of <NUM>. Consequently, each subframe may have a length of <NUM>. Each subframe may indicate a link direction (e.g., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include DL/UL data as well as DL/UL control data. UL and DL subframes for NR may be as described in more detail below with respect to <FIG>.

The RAN may include a central unit (CU) and distributed units (DUs). A NR BS (e.g., gNB, <NUM> Node B, Node B, transmit receive point (TRP), access point (AP)) may correspond to one or multiple BSs. NR cells can be configured as access cells (ACells) or data only cells (DCells). For example, the RAN (e.g., a central unit or distributed unit) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases, DCells may not transmit synchronization signals. In some cases, DCells may transmit synchronization signals. NR BSs may transmit downlink signals to UEs indicating the cell type. Based at least in part on the cell type indication, the UE may communicate with the NR BS. For example, the UE may determine NR BSs to consider for cell selection, access, handover, and/or measurement based at least in part on the indicated cell type.

<FIG> is a diagram <NUM> showing an example of a DL-centric subframe or wireless communication structure. In some aspects, the control portion may include RACH configuration information for a UE <NUM>. In some aspects, the control portion <NUM> may include legacy PDCCH information, shortened PDCCH (sPDCCH) information), a control format indicator (CFI) value (e.g., carried on a physical control format indicator channel (PCFICH)), one or more grants (e.g., downlink grants, uplink grants, etc.), and/or the like.

The DL-centric subframe may also include an UL short burst portion <NUM>. The UL short burst portion <NUM> may sometimes be referred to as an UL burst, an UL burst portion, a common UL burst, a short burst, an UL short burst, a common UL short burst, a common UL short burst portion, and/or various other suitable terms. In some aspects, the UL short burst portion <NUM> may include a random access preamble or the like. In some aspects, the UL short burst portion <NUM> may include one or more reference signals. Additionally, or alternatively, the UL short burst portion <NUM> may include feedback information corresponding to various other portions of the DL-centric subframe. For example, the UL short burst portion <NUM> may include feedback information corresponding to the control portion <NUM> and/or the data portion <NUM>. Non-limiting examples of information that may be included in the UL short burst portion <NUM> include an acknowledgment (ACK) signal (e.g., a physical uplink control channel (PUCCH) ACK, a physical uplink shared channel (PUSCH) ACK, an immediate ACK), a non-acknowledgment (NACK) signal (e.g., a PUCCH NACK, a PUSCH NACK, an immediate NACK), a scheduling request (SR), a buffer status report (BSR), a HARQ indicator, a channel state indication (CSI), a channel quality indicator (CQI), a sounding reference signal (SRS), a demodulation reference signal (DMRS), PUSCH data, and/or various other suitable types of information. The UL short burst portion <NUM> may include additional or alternative information, such as information pertaining to random access channel (RACH) procedures, scheduling requests, and various other suitable types of information.

<FIG> is a diagram <NUM> showing an example of an UL-centric subframe or wireless communication structure. The UL-centric subframe may include a control portion <NUM>. The control portion <NUM> may exist in the initial or beginning portion of the UL-centric subframe. The control portion <NUM> in <FIG> may be similar to the control portion <NUM> described above with reference to <FIG>. The UL-centric subframe may also include an UL long burst portion <NUM>. The UL long burst portion <NUM> may sometimes be referred to as the payload of the UL-centric subframe. The UL portion may refer to the communication resources utilized to communicate UL data from the subordinate entity (e.g., UE) to the scheduling entity (e.g., UE or BS). In some configurations, the control portion <NUM> may be a physical DL control channel (PDCCH).

The UL-centric subframe may also include an UL short burst portion <NUM>. The UL short burst portion <NUM> in <FIG> may be similar to the UL short burst portion <NUM> described above with reference to <FIG>, and may include any of the information described above in connection with <FIG>. The foregoing is merely one example of an UL-centric wireless communication structure, and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

In examples of configuring a RACH procedure for a supplementary uplink carrier using RACH configuration information provided on a different set of carriers than one including the supplementary uplink carrier, a BS <NUM> provides RACH configuration information to a UE <NUM> on a downlink carrier of a high band (i.e., a higher frequency band than a low band). The downlink carrier is included in a first set of carriers in the high band. The RACH configuration information may include configuration information for all uplink carriers of the UE <NUM>. For example, the RACH configuration information pertains to the first set of carriers and to a second set of carriers on the low band (e.g., a lower frequency band than the high band) that includes a supplementary uplink carrier of the UE <NUM>. The RACH configuration information includes a threshold (e.g., an RSRP threshold and/or the like) for selection of a synchronization signal block for the first set of carriers, a threshold for selection of a synchronization signal block for the second set of carriers, and may further include, for example, a starting index of a random access preamble group for the first set of carriers and/or the second set of carriers, a number of random access preambles for the first set of carriers and/or the second set of carriers, a configured UE transmitted power of the supplementary uplink carrier, a configured UE transmitted power of the downlink carrier and/or a serving cell of the high band (e.g., the cell performing the random access procedure), and/or the like.

In some aspects, performing the RACH procedure may include selecting a carrier, of the first set of carriers and the second set of carriers, and setting a transmission power to a configured UE transmitted power for the selected carrier.

In some aspects, the UE <NUM> may receive RACH procedure downlink traffic (e.g., the second message and/or the fourth message of the RACH procedure) using the first set of carriers (e.g., the downlink carrier used to provide the RACH configuration information). The UE <NUM> may optionally receive the RACH procedure downlink traffic using the second set of carriers (e.g., a paired downlink carrier of the supplementary uplink carrier). For example, when the supplementary uplink carrier is associated with a paired downlink carrier, the BS <NUM> may provide the RACH procedure downlink traffic on the paired downlink carrier, thereby conserving resources of the downlink carrier of the first set of carriers. In some aspects, the UE <NUM> may modify or interpret the second message differently based at least in part on whether the second message is received using the first set of carriers or the second set of carriers, as described in more detail below. In some aspects, the UE <NUM> may modify or interpret the second message differently based at least in part on whether the second message is received using the primary uplink or the supplementary uplink, as described in more detail elsewhere herein.

In aspects of the invention, the UE <NUM> determines whether the RACH procedure is to be performed using the first set of carriers or the second set of carriers based at least in part on a threshold. The BS <NUM> (or the UE <NUM>) configures a threshold, and the UE <NUM> selectively performs the RACH procedure using the first set of carriers, or the second set of carriers, based at least in part on whether threshold is satisfied. In some aspects, the threshold may be configured to improve load balancing of the first set of carriers and the second set of carriers. For example, the threshold may be based at least in part on a function (e.g., a hash function) of a UE identifier of the UE <NUM> (e.g., UEs <NUM> with an odd last digit may use the first set of carriers, and UEs <NUM> with an even last digit may use the second set of carriers).

In some aspects, the BS <NUM> is capable of overriding the threshold. The UE <NUM> receives a value from the BS <NUM> indicating that the threshold is to be overridden. In such a case, the UE <NUM> performs the RACH procedure using a particular set of carriers, of the first set of carriers and the second set of carriers, irrespective of a value associated with the threshold. The particular set of carriers is based on information specified by the value received from the BS <NUM>.

<FIG> shows an example of interpreting a random access response and/or a TPC command based at least in part on a configuration to transmit a particular message (e.g., an RRC connection setup message) on a supplementary uplink carrier. As shown in <FIG>, and by reference number <NUM>, the BS <NUM> may transmit a second message (e.g., shown as MSG2) to the UE <NUM> on the downlink carrier associated with the first set of carriers as part of the RACH procedure. In some aspects, the second message may include a random access response, and/ or the like. As further shown, the second message may include a TPC command. The TPC command may identify a power back-off for transmission of a third message by the UE <NUM>.

However, the power level used for transmission on the primary uplink carrier may be different than the power level used for transmission on the supplementary uplink carrier due to differences in coupling loss, channel characteristics, and/or the like. Furthermore, it may be beneficial to use different waveforms (e.g., DFT-spread waveforms versus CP-OFDM waveforms) for the supplementary uplink carrier and the primary uplink carrier. Still further, it may be beneficial to use a different numerology (e.g., subcarrier spacing, etc.) for the supplementary uplink carrier and the primary uplink carrier. In some aspects, the second message may identify a waveform and/or numerology for transmission of the third message.

As shown by reference number <NUM>, the UE <NUM> may determine that the third message is to be transmitted on the supplementary uplink carrier associated with the second set of carriers. Therefore, the UE <NUM> may interpret the second message differently than if the third message is to be transmitted on the primary uplink carrier. For example, the UE <NUM> may determine to use at least one of a modified TPC power offset (e.g., a modified power level or power back-off), a modified waveform, and/or a modified numerology to transmit the third message on the supplementary uplink carrier in comparison to transmitting the third message on the primary uplink carrier. For example, the UE <NUM> may use a lower power level (e.g., a higher TPC power offset or power back-off), may use a simpler waveform (e.g., a CP-OFDM waveform), and/or may use a tighter subcarrier spacing for the transmission of the third message using the supplementary uplink carrier in comparison to transmitting the third message on the primary uplink carrier.

In some instances as used herein, the term "interpret" may include performing, by the UE <NUM> for example, a determination or reading of information based on at least one factor in addition to the content of a message. In the present example, the UE <NUM> may receive a second message whose contents include parameters to be used by the UE <NUM> for transmission of a subsequent third message. The parameters, as determined by the UE <NUM>, however, may differ depending on whether the third message is to be transmitted on a primary uplink carrier or on a supplementary uplink carrier, although the content of the second message as received by the UE <NUM> remains the same. For example, the UE <NUM> may determine that the contents of the second message indicate a first set of parameters for transmission of the third message if the UE <NUM> is configured to transmit the third message on a primary uplink carrier, while the UE <NUM> may determine that the contents of the second message indicate a second set of parameters for transmission of the third message if the UE <NUM> is configured to transmit the third message on a supplementary uplink carrier. In some instances, a processor <NUM> of the UE <NUM> may perform the interpreting, determining, or reading of the second message.

As shown by reference number <NUM>, the UE <NUM> may transmit the third message of the RACH procedure on the supplementary uplink carrier associated with the low band. As shown, in some aspects, the UE <NUM> may transmit the third message at diminished transmission power. Additionally, or alternatively, the UE <NUM> may transmit the third message with a modified waveform. Additionally, or alternatively, the UE <NUM> may transmit the third message with a modified numerology. In this way, transmission performance of the UE <NUM> with regard to the third message may be improved. Furthermore, the specified transmission power can be adjusted for the supplementary uplink carrier, which may enable more reliable operation of the RACH procedure and/or reduce battery consumption associated with the RACH procedure.

<FIG> shows an example of generating a grant for a third message (e.g., an RRC connection setup message) based at least in part on receiving a first message (e.g., a random access preamble) on a supplementary uplink carrier. As shown in Fig. 9D, and by reference number <NUM>, the BS <NUM> may determine that the UE <NUM> is performing the RACH procedure using the supplementary uplink carrier (e.g., the second set of carriers) according to the first message (e.g., based at least in part on the first message being received on the second set of carriers). As further shown, the BS <NUM> may determine that a resource allocation and/or a TPC command of a grant (e.g., a grant provided using the second message of the RACH procedure) are to be formatted for the supplementary uplink carrier. For example, the supplementary uplink carrier may use a different resource allocation format, a different TPC command format, and/or the like than the primary uplink carrier. By using the different resource allocation format, the different TPC command format, and/or the like, the BS <NUM> may improve versatility of the RACH procedure and may enable performance of the RACH procedure using the supplementary uplink carrier.

In some aspects, the TPC command may have a different width for different frequency bands. For example, the TPC command may have a narrower width (e.g., <NUM> bits) for a frequency band associated with LTE, and may have a wider width (e.g., greater than <NUM> bits) for a <NUM> or NR band. In some aspects, the second message may exclude a channel quality indicator (CQI) request bit when the third message is to be provided on the supplementary uplink channel. For example, when the supplementary uplink channel is not associated with a paired downlink channel, a CQI may not be beneficial. Therefore, the BS <NUM> may omit the CQI request bit from the grant.

In some aspects, the resource allocation scheme may be different when the third message is to be provided on the supplementary uplink carrier. For example, the BS <NUM> may use a different subcarrier spacing, may allocate resources of a different uplink bandwidth, and/or the like.

As shown by reference number <NUM>, the BS <NUM> may provide the second message of the RACH procedure (e.g., the random access response), including the grant for the third message, on a downlink carrier of the first set of carriers (e.g., associated with the higher frequency band of the UE <NUM>). As shown by reference number <NUM>, the UE <NUM> may determine to transmit the third message on the supplementary uplink carrier according to the information included in the grant, and, as shown by reference number <NUM>, the UE <NUM> may transmit the third message on the supplementary uplink carrier. By transmitting the third message according to the information included in the grant, the UE <NUM> may improve RACH procedure performance on the supplementary uplink carrier.

<FIG> is an example of generating a random access radio network temporary identifier including a carrier frequency offset index. As shown in Fig. 9E, and by reference number <NUM>, the BS <NUM> may generate a random access radio network temporary identifier (RA-RNTI) for the UE <NUM>. The BS <NUM> may generate the RA-RNTI using information provided by the UE <NUM> (e.g., a slot index for the slot on which the UE <NUM> provided the first message and a carrier frequency offset index for the carrier on which the UE <NUM> provided the first message). The RA-RNTI may be used to scramble a PDCCH grant for PDSCH resources on which to provide the second message of the RACH procedure. In some aspects, the BS <NUM> may generate the RA-RNTI using an uplink carrier identifier based at least in part on whether the first set of carriers or the second set of carriers is used for the RACH procedure. For example, the uplink carrier identifier may have a first value when the first set of carriers is used and may have a second value when a second set of carriers is used.

By generating the RA-RNTI using the carrier frequency offset index, provision of an RA-RNTI on a downlink carrier for a different set of carriers than the supplementary uplink carrier is enabled. For example, a traditional RA-RNTI may be generated using the slot index and not the carrier frequency offset. In such a situation, when the UE <NUM> receives the PDCCH with the grant for the random access response, the UE <NUM> may not be able to identify the uplink carrier on which the random access preamble (e.g., the first message) was provided. By generating the RA-RNTI using the carrier frequency offset index, provision of the random access response on a different set of carriers than the random access preamble is enabled.

As shown by reference number <NUM>, the UE <NUM> may receive the grant for the second message (e.g., the random access response). As further shown, the grant may be scrambled using the RA-RNTI (e.g., that identifies the carrier frequency offset index), and may be received on the downlink carrier associated with the first set of carriers.

As shown by reference number <NUM>, the UE <NUM> may unscramble the grant using the slot index and carrier frequency offset index from the first message (e.g., the random access preamble). For example, the UE <NUM> may know the slot index and the carrier frequency offset index, and may attempt to unscramble the grant using the known slot index and the carrier frequency offset index. Since unscrambling in such a case is successful, the UE <NUM> may determine that the granted resources are for the UE <NUM>, and may receive the second message (e.g., the random access response) on the granted resources.

As shown by reference number <NUM>, the BS <NUM> may provide the second message (e.g., the random access response) on the granted resources using the downlink carrier of the first set of carriers. As shown by reference number <NUM>, the UE <NUM> may receive the second message (e.g., the random access response) on the granted resources, and may perform the RACH procedure accordingly, as described in more detail elsewhere herein. Thus, the RA-RNTI is determined based at least in part on a carrier frequency offset index, which enables provision of the random access preamble on a different carrier than the grant for the random access response.

In some aspects, the grant and/or the random access response may include information identifying the carrier on which the random access preamble was received (e.g., the supplementary uplink carrier). For example, such information may be included in a payload of the grant and/or the random access response. Thus, complexity of generating the RA-RNTI is reduced.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where a UE (e.g., UE <NUM>) performs supplementary uplink random access configuration.

As shown in <FIG>, process <NUM> includes receiving random access channel (RACH) configuration information on a downlink carrier of a first set of carriers, wherein the RACH configuration information pertains to the first set of carriers and to a second set of carriers (block <NUM>). For example, the UE (e.g., using antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, and/or the like) may receive RACH configuration information on a downlink carrier of a first set of carriers. The RACH configuration information pertains to the first set of carriers and to a second set of carriers.

As further shown in <FIG>, process <NUM> includes selectively performing a RACH procedure with regard to the first set of carriers or the second set of carriers based at least in part on the RACH configuration information (block <NUM>). For example, the UE (e.g., using controller/processor <NUM> and/or the like) may selectively perform a RACH procedure with regard to the first set of carriers or the second set of carriers. When the UE performs the RACH procedure with regard to the first set of carriers, the UE may use RACH configuration information pertaining to the first set of carriers. When the UE performs the RACH procedure with regard to the second set of carriers, the UE may use RACH configuration information pertaining to the second set of carriers.

The first set of carriers is associated with a higher frequency band than the second set of carriers. The second set of carriers includes an uplink carrier that is a supplementary uplink carrier of the user equipment. In some aspects, the RACH configuration information may be received in system information or radio resource control configuration information of the user equipment.

In aspects of the invention, the user equipment is configured to select a particular set of carriers, of the first set of carriers and the second set of carriers, to use to perform the RACH procedure based at least in part on a threshold. In some aspects, the threshold is configured to balance a load, relating to the RACH procedure, between the first set of carriers and the second set of carriers.

In some aspects, the threshold is based at least in part on a hash function performed using an identifier associated with the user equipment. In some aspects, the user equipment is configured to perform the RACH procedure with regard to a particular set of carriers, of the first set of carriers and the second set of carriers, based at least in part on a value received by the user equipment and indicating to perform the RACH procedure with regard to the particular set of carriers. In some aspects, selectively performing the RACH procedure comprises retransmitting a first message of the RACH procedure on the second set of carriers based at least in part on an unsuccessful transmission of the first message on the first set of carriers. In some aspects, the first message is retransmitted on the second set of carriers based at least in part on a particular number of unsuccessful transmissions of the first message on the first set of carriers. In some aspects, a different power level is used for the retransmission than for the unsuccessful transmission. In some aspects, the different power level is based at least in part on performance of an open loop power control process for the second set of carriers. In some aspects, a same power level is used for the retransmission and for the unsuccessful transmission.

In some aspects, selectively performing the RACH procedure comprises transmitting an uplink message, based at least in part on a TPC message, using the first set of carriers or the second set of carriers, wherein the TPC message is interpreted based at least in part on whether the uplink message is transmitted using the first set of carriers or the second set of carriers.

In some aspects, selectively performing the RACH procedure comprises transmitting an uplink message, based at least in part on a TPC message, using the first set of carriers or the second set of carriers, wherein the TPC message is associated with a different number of bits based at least in part on whether the uplink message is transmitted using the first set of carriers or the second set of carriers.

In some aspects, selectively performing the RACH procedure comprises transmitting an uplink message, based at least in part on a TPC message, using the first set of carriers or the second set of carriers, wherein the uplink message is associated with a particular waveform or numerology based at least in part on whether the uplink message is transmitted using the first set of carriers or the second set of carriers.

In some aspects, selectively performing the RACH procedure comprises transmitting an uplink message, based at least in part on a TPC message, using the first set of carriers or the second set of carriers, wherein the uplink message is a third message of the RACH procedure.

In some aspects, selectively performing the RACH procedure comprises transmitting an uplink message, based at least in part on a TPC message, using the first set of carriers or the second set of carriers, wherein the uplink message is associated with a grant, wherein the grant is formatted differently based at least in part on whether the uplink message is transmitted using the first set of carriers or the second set of carriers.

In some aspects, at least one of a resource allocation, a TPC message bit width, or a channel quality information (CQI) request bit is formatted differently based at least in part on whether the uplink message is transmitted using the first set of carriers or the second set of carriers.

In some aspects, a random access radio network temporary identifier (RA-RNTI) of the user equipment may be determined based at least in part on a particular set of carriers, of the first set of carriers and the second set of carriers, with regard to which the RACH procedure is performed.

In some aspects, a random access radio network temporary identifier (RA-RNTI) for a random access response (RAR) of the RACH procedure may identify a particular set of carriers, of the first set of carriers and the second set of carriers, on which the RACH procedure is performed.

Claim 1:
A method of wireless communication performed by a user equipment (<NUM>), to establish an RRC connection with a base station (<NUM>), comprising:
receiving (<NUM>) random access channel, RACH, configuration information on a downlink carrier of a first set of carriers, the first set of carriers including a primary uplink carrier of a first frequency band, which is a higher frequency band than a second frequency band associated with a supplementary uplink carrier included by a second set of carriers,
wherein the RACH configuration information pertains to the first set of carriers and to the second set of carriers,
wherein the RACH configuration information includes a threshold, wherein the user equipment (<NUM>) is configured to select a particular set of carriers, of the first set of carriers and the second set of carriers, to use to perform the RACH procedure based on whether the threshold is satisfied; and
selectively performing (<NUM>) a RACH procedure with regard to the first set of carriers or the second set of carriers based at least in part on the RACH configuration information,
characterized in that:
the user equipment is configured to perform the RACH procedure with regard to a particular set of carriers, of the first set of carriers and the second set of carriers, based on a value received by the user equipment and indicating to perform the RACH procedure with regard to the particular set of carriers, irrespective of the threshold.