Distributed channel access mechanism using multiple access signatures for control transmissions

Aspects of the disclosure relate to a distributed channel access mechanism using multiple access (MA) signatures for control transmissions. In one aspect, a transmitting device determines a MA signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource, transmits sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, transmits the first data information on the first set of frequency resources, and receives, from a receiving device, a response indicating whether reception of the first data information was successful. Other aspects, embodiments, and features are also claimed and described.

TECHNICAL FIELD

The technology discussed below relates generally to wireless communication systems, and more particularly, to a channel access mechanism using a multiple access (MA) signature for a control transmission.

INTRODUCTION

3rd Generation Partnership Project (3GPP) New Radio (NR) specifications (often referred to as 5G) support downlink transmissions from multiple transmission points (TRPs). In a multi-TRP transmission scheme, multiple TRPs may or may not be co-located (e.g., within a same cell). Moreover, the multiple TRPs may transmit data to the same UE. The data sent from the multiple TRPs to the same UE may be the same data or different data. When transmitting different data from the multiple TRPs, a higher throughput may be achieved. When transmitting the same data (with potentially different redundancy versions) from the multiple TRPs, transmission reliability may be improved.

Cellular vehicle-to-everything (V2X) is a vehicular communication system enabling communications between a vehicle and any entity that may affect the vehicle. V2X may incorporate other more specific types of communication, e.g., vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P), vehicle-to-device (V2D), and vehicle-to-grid (V2G).

In 3GPP Release 14, LTE-based communication has been defined for a direct interface (e.g., PC5 interface) as well as for a network interface (e.g., Uu interface). Currently, V2V communication via the PC5 interface is broadcast. However, for later 3GPP releases (e.g. Release 16 and beyond), there is a need to establish unicast links between vehicles for advanced use cases. A use case for 1-to-1 or 1-to-many V2V link scenarios may involve the on-demand sharing of sensor data that cannot be supported over broadcast. Another use case may involve a see-through camera feed, such as when a first vehicle wishes to see in front of a second vehicle ahead of the first vehicle using the second vehicle's camera.

As the demand for mobile broadband access continues to increase, research and development continue to advance wireless communication technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.

BRIEF SUMMARY OF SOME EXAMPLES

Aspects of the disclosure relate to a distributed channel access mechanism using multiple access (MA) signatures for control transmissions. In one aspect, a transmitting device determines a MA signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource, transmits sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, transmits the first data information on the first set of frequency resources, and receives, from a receiving device, a response indicating whether reception of the first data information was successful. In another aspect, a receiving device receives one or more sidelink control information on a first set of frequency resources from one or more transmitting devices, detects a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices, wherein the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource, determines, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of first data information associated with the corresponding sidelink control information, determines a likelihood of successfully receiving the first data information based on the determined SINR, and transmits a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful. Other aspects, embodiments, and features are also claimed and described.

In one example, a method for channel access at a transmitting device is disclosed. The method includes determining a multiple access (MA) signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource, transmitting sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, transmitting the first data information on the first set of frequency resources, receiving, from a receiving device, a response indicating whether reception of the first data information was successful, determining second data information and a second set of frequency resources based on the response received from the receiving device, and transmitting the second data information on the second set of frequency resources.

In another example, a transmitting device for channel access is disclosed. The transmitting device includes means for determining a multiple access (MA) signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource, means for transmitting sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, means for transmitting the first data information on the first set of frequency resources, means for receiving, from a receiving device, a response indicating whether reception of the first data information was successful, means for determining second data information and a second set of frequency resources based on the response received from the receiving device, and means for transmitting the second data information on the second set of frequency resources.

In a further example, a transmitting device for channel access is disclosed. The transmitting device includes a processor, a transceiver communicatively coupled to the at least one processor, and a memory communicatively coupled to the at least one processor. The at least one processor is configured to determine a multiple access (MA) signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource, transmit sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, transmit the first data information on the first set of frequency resources, receive, from a receiving device, a response indicating whether reception of the first data information was successful, determine second data information and a second set of frequency resources based on the response received from the receiving device, and transmit the second data information on the second set of frequency resources.

In yet another example, a non-transitory computer-readable medium storing computer-executable code at a transmitting device for channel access is disclosed. The non-transitory computer-readable medium includes code for causing a computer to determine a multiple access (MA) signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource, transmit sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, transmit the first data information on the first set of frequency resources, receive, from a receiving device, a response indicating whether reception of the first data information was successful, determine second data information and a second set of frequency resources based on the response received from the receiving device, and transmit the second data information on the second set of frequency resources.

In one example, a method for channel access at a receiving device is disclosed. The method includes receiving one or more sidelink control information on a first set of frequency resources from one or more transmitting devices, detecting a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices, wherein the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource, determining, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of first data information associated with the corresponding sidelink control information, determining a likelihood of successfully receiving the first data information based on the determined SINR, receiving, or attempting to receive, the first data information on the first set of frequency resources, transmitting a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful, and receiving second data information on a second set of frequency resources.

In another example, a receiving device for channel access is disclosed. The receiving device includes means for receiving one or more sidelink control information on a first set of frequency resources from one or more transmitting devices, means for detecting a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices, wherein the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource, means for determining, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of first data information associated with the corresponding sidelink control information, means for determining a likelihood of successfully receiving the first data information based on the determined SINR, means for receiving, or attempting to receive, the first data information on the first set of frequency resources, means for transmitting a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful, and means for receiving second data information on a second set of frequency resources.

In a further example, a receiving device for channel access is disclosed. The receiving device includes a processor, a transceiver communicatively coupled to the at least one processor, and a memory communicatively coupled to the at least one processor. The at least one processor is configured to receive one or more sidelink control information on a first set of frequency resources from one or more transmitting devices, detect a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices, wherein the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource, determine, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of first data information associated with the corresponding sidelink control information, determine a likelihood of successfully receiving the first data information based on the determined SINR, receive, or attempt to receive, the first data information on the first set of frequency resources, transmit a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful, and receive second data information on a second set of frequency resources.

In yet another example, a non-transitory computer-readable medium storing computer-executable code at a receiving device for channel access is disclosed. The non-transitory computer-readable medium includes code for causing a computer to receive one or more sidelink control information on a first set of frequency resources from one or more transmitting devices, detect a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices, wherein the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource, determine, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of first data information associated with the corresponding sidelink control information, determine a likelihood of successfully receiving the first data information based on the determined SINR, receive, or attempt to receive, the first data information on the first set of frequency resources, transmit a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful, and receive second data information on a second set of frequency resources.

DETAILED DESCRIPTION

Aspects of the disclosure relate to a distributed channel access mechanism using multiple access (MA) signatures for control transmissions.

As illustrated, the RAN104includes a plurality of base stations108. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. In different technologies, standards, or contexts, a base station may variously be referred to by those skilled in the art as a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a gNode B (gNB), or some other suitable terminology.

Base stations108are not the only entities that may function as scheduling entities. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs).

As illustrated inFIG. 1, a scheduling entity108may broadcast downlink traffic112to one or more scheduled entities106. Broadly, the scheduling entity108is a node or device responsible for scheduling traffic in a wireless communication network, including the downlink traffic112and, in some examples, uplink traffic116from one or more scheduled entities106to the scheduling entity108. On the other hand, the scheduled entity106is a node or device that receives downlink control information114, including but not limited to scheduling information (e.g., a grant), synchronization or timing information, or other control information from another entity in the wireless communication network such as the scheduling entity108.

FIG. 2further includes a quadcopter or drone220, which may be configured to function as a base station. That is, in some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station such as the quadcopter220.

In some examples, a mobile network node (e.g., quadcopter220) may be configured to function as a UE. For example, the quadcopter220may operate within cell202by communicating with base station210.

In a further aspect of the RAN200, sidelink signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, two or more UEs (e.g., UEs226and228) may communicate with each other using peer to peer (P2P) or sidelink signals227without relaying that communication through a base station (e.g., base station212). In a further example, UE238is illustrated communicating with UEs240and242. Here, the UE238may function as a scheduling entity or a primary sidelink device, and UEs240and242may function as a scheduled entity or a non-primary (e.g., secondary) sidelink device. In still another example, a UE may function as a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P), or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a mesh network example, UEs240and242may optionally communicate directly with one another in addition to communicating with the scheduling entity238. Thus, in a wireless communication system with scheduled access to time-frequency resources and having a cellular configuration, a P2P configuration, or a mesh configuration, a scheduling entity and one or more scheduled entities may communicate utilizing the scheduled resources.

In the radio access network200, the ability for a UE to communicate while moving, independent of its location, is referred to as mobility. The various physical channels between the UE and the radio access network are generally set up, maintained, and released under the control of an access and mobility management function (AMF, not illustrated, part of the core network102inFIG. 1), which may include a security context management function (SCMF) that manages the security context for both the control plane and the user plane functionality, and a security anchor function (SEAF) that performs authentication.

In early 5G NR specifications, user data is coded using quasi-cyclic low-density parity check (LDPC) with two different base graphs: one base graph is used for large code blocks and/or high code rates, while the other base graph is used otherwise. Control information and the physical broadcast channel (PBCH) are coded using Polar coding, based on nested sequences. For these channels, puncturing, shortening, and repetition are used for rate matching.

However, those of ordinary skill in the art will understand that aspects of the present disclosure may be implemented utilizing any suitable channel code. Various implementations of scheduling entities108and scheduled entities106may include suitable hardware and capabilities (e.g., an encoder, a decoder, and/or a CODEC) to utilize one or more of these channel codes for wireless communication.

Within the present disclosure, a frame refers to a duration of 10 ms for wireless transmissions, with each frame consisting of 10 subframes of 1 ms each. On a given carrier, there may be one set of frames in the UL, and another set of frames in the DL. Referring now toFIG. 3, an expanded view of an exemplary DL subframe302is illustrated, showing an OFDM resource grid304. However, as those skilled in the art will readily appreciate, the PHY transmission structure for any particular application may vary from the example described here, depending on any number of factors. Here, time is in the horizontal direction with units of OFDM symbols; and frequency is in the vertical direction with units of subcarriers or tones.

A UE generally utilizes only a subset of the resource grid304. An RB may be the smallest unit of resources that can be allocated to a UE. Thus, the more RBs scheduled for a UE, and the higher the modulation scheme chosen for the air interface, the higher the data rate for the UE.

In this illustration, the RB308is shown as occupying less than the entire bandwidth of the subframe302, with some subcarriers illustrated above and below the RB308. In a given implementation, the subframe302may have a bandwidth corresponding to any number of one or more RBs308. Further, in this illustration, the RB308is shown as occupying less than the entire duration of the subframe302, although this is merely one possible example.

Although not illustrated inFIG. 3, the various REs306within a RB308may be scheduled to carry one or more physical channels, including control channels, shared channels, data channels, etc. Other REs306within the RB308may also carry pilots or reference signals, including but not limited to a demodulation reference signal (DMRS) a control reference signal (CRS), or a sounding reference signal (SRS). These pilots or reference signals may provide for a receiving device to perform channel estimation of the corresponding channel, which may enable coherent demodulation/detection of the control and/or data channels within the RB308.

In a DL transmission, the transmitting device (e.g., the scheduling entity108) may allocate one or more REs306(e.g., within a control region312) to carry DL control information114including one or more DL control channels, such as a PBCH; a PSS; a SSS; a physical control format indicator channel (PCFICH); a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH); and/or a physical downlink control channel (PDCCH), etc., to one or more scheduled entities106. The PCFICH provides information to assist a receiving device in receiving and decoding the PDCCH. The PDCCH carries downlink control information (DCI) including but not limited to power control commands, scheduling information, a grant, and/or an assignment of REs for DL and UL transmissions. The PHICH carries HARQ feedback transmissions such as an acknowledgment (ACK) or negative acknowledgment (NACK). HARQ is a technique well-known to those of ordinary skill in the art, wherein the integrity of packet transmissions may be checked at the receiving side for accuracy, e.g., utilizing any suitable integrity checking mechanism, such as a checksum or a cyclic redundancy check (CRC). If the integrity of the transmission confirmed, an ACK may be transmitted, whereas if not confirmed, a NACK may be transmitted. In response to a NACK, the transmitting device may send a HARQ retransmission, which may implement chase combining, incremental redundancy, etc.

In an UL transmission, the transmitting device (e.g., the scheduled entity106) may utilize one or more REs306to carry UL control information118including one or more UL control channels, such as a physical uplink control channel (PUCCH), to the scheduling entity108. UL control information may include a variety of packet types and categories, including pilots, reference signals, and information configured to enable or assist in decoding uplink data transmissions. In some examples, the control information118may include a scheduling request (SR), e.g., a request for the scheduling entity108to schedule uplink transmissions. Here, in response to the SR transmitted on the control channel118, the scheduling entity108may transmit downlink control information114that may schedule resources for uplink packet transmissions. UL control information may also include HARQ feedback, channel state feedback (CSF), or any other suitable UL control information.

In addition to control information, one or more REs306(e.g., within the data region314) may be allocated for user data or traffic data. Such traffic may be carried on one or more traffic channels, such as, for a DL transmission, a physical downlink shared channel (PDSCH); or for an UL transmission, a physical uplink shared channel (PUSCH). In some examples, one or more REs306within the data region314may be configured to carry system information blocks (SIBs), carrying information that may enable access to a given cell.

The channels or carriers described above and illustrated inFIGS. 1 and 3are not necessarily all the channels or carriers that may be utilized between a scheduling entity108and scheduled entities106, and those of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other traffic, control, and feedback channels.

In OFDM, to maintain orthogonality of the subcarriers or tones, the subcarrier spacing may be equal to the inverse of the symbol period. A numerology of an OFDM waveform refers to its particular subcarrier spacing and cyclic prefix (CP) overhead. A scalable numerology refers to the capability of the network to select different subcarrier spacings, and accordingly, with each spacing, to select the corresponding symbol duration, including the CP length. With a scalable numerology, a nominal subcarrier spacing (SCS) may be scaled upward or downward by integer multiples. In this manner, regardless of CP overhead and the selected SCS, symbol boundaries may be aligned at certain common multiples of symbols (e.g., aligned at the boundaries of each 1 ms subframe). The range of SCS may include any suitable SCS. For example, a scalable numerology may support a SCS ranging from 15 kHz to 480 kHz.

To illustrate this concept of a scalable numerology,FIG. 4shows a first RB402having a nominal numerology, and a second RB404having a scaled numerology. As one example, the first RB402may have a ‘nominal’ subcarrier spacing (SCSn) of 30 kHz, and a ‘nominal’ symbol durationnof 333 μs. Here, in the second RB404, the scaled numerology includes a scaled SCS of double the nominal SCS, or 2×SCSn=60 kHz. Because this provides twice the bandwidth per symbol, it results in a shortened symbol duration to carry the same information. Thus, in the second RB404, the scaled numerology includes a scaled symbol duration of half the nominal symbol duration, or (symbol durationn)÷2=167 μs.

In some aspects, a channel access mechanism may be based on a Listen Before Talk (LBT) contention-based design.FIG. 5illustrates a transmission time interval (TTI) structure500for a LBT-based channel access mechanism, e.g., 0.5 ms TTI with 30 kHz subcarrier spacing (SCS). The TTI structure500may include a first region502having a number of LBT symbols for communicating a LBT sequence. The first region502is followed by a second region504for communicating control information. A third region506may include a number of symbols for communicating data. Finally, the third region506is followed by a feedback/gap region508for communicating a feedback transmission (e.g., related to a previous TTI) and facilitating a transmission/reception (Tx/Rx) turnaround. If TTI bundling is utilized, then the LBT symbols in the first region502may be amortized as data. Notably, some of the symbols may be vulnerable to puncturing if automatic gain control (AGC) retraining is required.

FIG. 6illustrates use of a channel bandwidth600for a channel access mechanism. In an aspect, a channel bandwidth/resource pool may be divided into subchannels. For example, one subchannel may be equal to 5 resource blocks (RBs).

In an aspect, a transmitting UE may follow a LBT procedure for selecting one or more subchannels. The LBT procedure may include the transmitting UE using a counter to determine an action to execute based on a counter value (e.g., 0 or 1). Actions corresponding to the counter values may be randomly chosen or based on priority. In an example, if the counter=0, a first UE602may begin transmitting an LBT sequence620in a subchannel starting from a first symbol in a TTI. Following the LBT sequence620, the first UE602may transmit control information622and data624.

In another example, if the counter=1, a transmitting UE (e.g., second UE604or third UE606) may listen during a first LBT symbol of a TTI to determine whether one or more subchannels are being used. The transmitting UE may then rank subchannels according to a received energy on a subchannel and select one or more unused contiguous subchannels with a lowest energy for transmission. Thereafter, following a symbol for Tx/Rx turnaround, the transmitting UE may begin transmitting an LBT sequence in one or more subchannels starting from a third symbol in a TTI. Following the LBT sequence, the transmitting UE may transmit control information and data.

As shown inFIG. 6, the second UE604may listen during a first LBT symbol640of TTI(n+1) to determine whether two contiguous subchannels are being used. If the second UE604detects a low energy from the two subchannels, this may indicate that the two subchannels are unused and available for transmission. Accordingly, the second UE604selects the two subchannels and begins transmitting an LBT sequence642in the two subchannels starting from a third symbol in the TTI(n+1), followed by control information644and data646.

As further shown inFIG. 6, the third UE606may listen during a first LBT symbol660of TTI(n) to determine whether any subchannels are being used. If the third UE606detects a low energy only from one subchannel, this may indicate that only the one subchannel is unused and available for transmission. Accordingly, the third UE606selects the subchannel and begins transmitting an LBT sequence662in the subchannel starting from a third symbol in the TTI(n), followed by control information664and data666.

In an aspect, the channel bandwidth600for the channel access mechanism may be scaled to allow for more LBT symbols. However, such scaling may increase overhead. A drawback of the channel access mechanism ofFIG. 6may be that the mechanism only provides for transmitter-side yielding. Hence, a receiver in the middle of two transmitters may have lower quality of service (QoS). Another drawback may be that the mechanism may not scale well with increasing UE densities.

Aspects of the disclosure relate to using multiple access (MA) signatures for non-orthogonal multiple access (NOMA). MA signatures are identifiers for distinguishing UE-specific patterns of data transmissions and may be used to multiplex UEs on a set of resources. NOMA uses non-orthogonal signatures. When an overloading factor of greater than 1 (>1) is present, NOMA access may support a large number of UEs. For example, the overloading factor is greater than 1 when 6 UEs are spread over 4 resource elements (REs).

In 3GPP, NOMA in downlink communications may use superposition coding, such as multi-user superposition transmission (MUST). Moreover, a receiver may be configured for successive interference cancellation (SIC). NOMA in uplink communications may utilize grant-free uplink transmissions that are power controlled. Schemes may include RSMA, SCMA, interleave-division multiple access (IDMA), pattern division multiple access (PDMA), multi-user shared access (MUSA), etc.

For V2X, a transmission may not be power controlled to a certain receiver. Hence, V2X and NOMA are different with respect to uplink communications in that different tradeoff and combination schemes are possible. In V2X, successive interference cancellation (SIC) is needed to separate transmitting UEs with a power imbalance. Moreover, V2X needs MA signatures to separate transmitting UEs that cannot be separated with SIC. Notably, power-domain MA schemes are not applicable for V2X.

FIG. 7illustrates a V2X scenario700where transmissions to a receiver are not power controlled. InFIG. 7, a first transmitting UE702, a second transmitting UE704, and a third transmitting UE706all transmit to a receiving UE708. In an example, a first transmission710from the first transmitting UE702and a second transmission712from the second transmitting UE704may potentially be separated with SIC at the receiving UE708. However, orthogonal/low correlation signatures may be needed to separate the first transmission710from the first UE702and a third transmission714from the third UE706if such transmissions cannot be separated with SIC at the receiving UE708.

In an aspect of the disclosure, to improve transmission reliability with increasing user densities, MA signatures may be used for control transmissions to make a control transmission more reliable even when collisions are detected. For example, a NACK-based reselection scheme is provided to reselect a resource in case a collision is detected. In an aspect, a request (REQ)-response (RSP) based design is provided that allows for a NOMA/MA signature spread REQ and RSP for detecting collisions during the REQ phase.

FIG. 8illustrates an example TTI structure800for a REQ-RSP based channel access design according to an aspect of the present disclosure.

The TTI structure800may include a first region802for communicating control information over, e.g., 1 or 2 symbols. In an aspect, the control information includes a transmission request (REQ). That is, the first region802carries information related to the REQ instead of only a sequence. The first region802is followed by a second region804for communicating orthogonal multiple access (OMA) data over a number of symbols. A third region806for communicating a response (RSP) to the REQ may follow the second region804. Notably, a Tx/Rx turnaround region (e.g., 1/2 symbol in length) may precede and follow the third region806. In an aspect, the RSP may be in the form of ACK/NACK or information indicating that a transmitter should reselect a resource for the transmission of data. In an aspect, the TTI structure800for the REQ-RSP based transmission design, wherein the control information (REQ) is transmitted followed by the transmission of the OMA data and then the RSP, reduces overhead in comparison to a transmission design that transmits a REQ followed by a transmission of a RSP, control information, and data in a TTI.

In an aspect, the REQ-RSP based transmission design ofFIG. 8may be implemented with or without LBT symbols. When implemented without LBT symbols, control information may be transmitted in the first region802with MA signatures (e.g., RSMA or SCMA). A MA signature length (e.g., repetition factor for RSMA) may be configured for a channel bandwidth/resource pool since the MA signature length depends on a QoS versus density needs. Moreover, the MA signature length can be dynamically modified based on UE measurements of congestion, etc. Notably, a baseline of OMA control information and data may still be supported based on configuration (with LBT symbols).

In an aspect, when the control information is transmitted with MA signatures (e.g., RSMA), reference symbols (RS) for the control information are orthogonal. The RS may be used to determine a start/stop of resource allocation. Notably, in a previous scheme, the start/stop of resource allocation may have been determined based on different LBT sequences.

In an aspect, a number of orthogonal RS dimensions needed for transmission may be determined as follows. For example, a number of orthogonal RS dimensions needed may be equal to N×4, where N is the number of UEs that can be multiplexed in the channel bandwidth/resource pool. The number of UEs that can be multiplexed may determine a collision probability. Therefore, a higher value of N may be needed for higher QoS and higher densities.

If N=1, then the number of orthogonal RS dimensions needed is equal to N×4=1×4=4. Thus, a transmitter transmitting OMA control information and data may rely on random selection alone for reduced collisions. Notably, this is the same as a baseline design with a LBT-based mechanism.

If N=2, then the number of orthogonal RS dimensions needed is equal to N×4=2×4=8. If N=4, then the number of orthogonal RS dimensions needed is equal to N×4=4×4=16. If N=8, then the number of orthogonal RS dimensions needed is equal to N×8=8×4=32. Beyond 32 orthogonal RS dimensions may be difficult to attain but low correlation may still be achieved with different sequences.

FIG. 9illustrates an example resource structure900for control symbols having reference symbols (RS) according to an aspect of the present disclosure. Referring toFIG. 9, methods for attaining a number of orthogonal RS dimensions will be described.

The number of orthogonal RS dimensions may be attained using one or two root sequences. Moreover, the number of attainable RS dimensions may be a product of a maximum number of cyclic shifts, a time domain orthogonal cover code (TD-OCC), a frequency domain orthogonal cover code (FD-OCC), and the number of roots sequences. In one example, if the maximum number of cyclic shifts is 4, TD-OCC is 2, FD-OCC is 2, and the number of root sequences is 1, then the number of attainable RS dimensions=4×2×2×1=16. In another example, if the maximum number of cyclic shifts is 4, TD-OCC is 2, FD-OCC is 2, and the number of root sequences is 2, then the number of attainable RS dimensions=4×2×2×1=32.

In an aspect, a MA sequence may be applied to have subchannel-based spreading/interleaving. This is appropriate since two UEs may overlap only in a subset of subchannels.

In an aspect, a MA sequence may be configured for a channel bandwidth/resource pool according to a MA signature length, a number of control symbols, a number of cyclic shifts, a number of TD-OCC, a number of FD-OCC, and a number of root sequences. In an example, the MA signature length is 4, the number of control symbols is 2, the number of cyclic shifts is 4, the number of TD-OCC is 2, the number of FD-OCC is 2, and the number of root sequences is 1. This results in a multiplexing factor of4with16orthogonal RS for control decoding and allocation size detection.

FIG. 10illustrates an example TTI structure1000for a REQ-RSP based channel access design according to an aspect of the present disclosure.

The TTI structure1000may include a first TTI (TTI(n)) having a first region1002for communicating control information over 1 or 2 symbols. In an aspect, the control information includes a transmission request (REQ). The first region1002is followed by a second region1004for communicating orthogonal multiple access (OMA) data over a number of symbols. A third region1006for communicating a response (RSP) to the REQ may follow the second region1004. Notably, a Tx/Rx turnaround region (e.g., 1/2 symbol in length) may precede and follow the third region1006. The RSP may be in the form of ACK/NACK or information indicating that a transmitter should reselect a resource for the transmission of data. The TTI structure1000may also include a second TTI (TTI(n+1)) having a fourth region1008for communicating OMA data. However, if the RSP communicated during the previous TTI (e.g., third region1006of TTI(n)) indicates that the transmitter should reselect a resource (e.g., due to a collision) for transmission, the OMA data will not be transmitted in the fourth region1008.

In an aspect, when control information is transmitted with MA signatures, a receiving UE may decode multiple control information from multiple transmitting UEs and determine whether data corresponding to the multiple control information will collide. The receiving UE may estimate a signal-to-interference-plus-noise ratio (SINR) of the data of interest based on RS. Notably, a one-to-one correspondence may exist between a data RS sequence and a MA signature used for control information. Thus, SINR in a data portion can be estimated per UE. The receiving UE may determine whether or not the data can be decoded based on an estimated SINR for the data (on RS REs).

Referring toFIG. 10, the receiving UE transmits the RSP (in the third region1006) to the transmitting UE to indicate whether the transmitting UE is to continue transmission of data or reselect a resource for transmission due to collision. Priority information, included in the control information transmitted in the first region1002or based on a MA signature, is used to determine which transmitting UE should yield. In an aspect, the RSP transmitted to a particular transmitting UE is transmitted with the same MA signature used by the particular transmitting UE to transmit the control information (REQ) to the receiving UE. The RSP may be transmitted using a system frame number (SFN). In an aspect, the receiving UE may transmit the RSP to two or more transmitting UEs. For example, the receiving UE may inform one transmitting UE to continue data transmission while informing another transmitting UE to reselect a resource for transmission. In another aspect, a transmitting UE may detect the RSP from a previous TTI to determine whether or not a next TTI is available for transmission. Accordingly, the RSP may provide receiver-side protection.

FIG. 11is a block diagram illustrating an example of a hardware implementation for a user equipment (UE)1100employing a processing system1114. For example, the UE1100may be a UE as illustrated in any one or more ofFIGS. 1 and/or 2.

The UE1100may be implemented with a processing system1114that includes one or more processors1104. Examples of processors1104include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the UE1100may be configured to perform any one or more of the functions described herein. That is, the processor1104, as utilized in a UE1100, may be used to implement any one or more of the processes and procedures described below and illustrated inFIGS. 12 and 13.

In this example, the processing system1114may be implemented with a bus architecture, represented generally by the bus1102. The bus1102may include any number of interconnecting buses and bridges depending on the specific application of the processing system1114and the overall design constraints. The bus1102communicatively couples together various circuits including one or more processors (represented generally by the processor1104), a memory1105, and computer-readable media (represented generally by the computer-readable medium1106). The bus1102may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface1108provides an interface between the bus1102and a transceiver1110. The transceiver1110provides a communication interface or means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface1112(e.g., keypad, display, speaker, microphone, joystick) may also be provided. Of course, such a user interface1112is optional, and may be omitted in some examples, such as a base station.

In some aspects of the disclosure, the processor1104may include multiple access (MA) signature processing circuitry1140configured for various functions, including, for example, determining a multiple access (MA) signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource. For example, the MA signature processing circuitry1140may be configured to implement one or more of the functions described below in relation toFIG. 12, including, e.g., block1202. The processor may also include control/data processing circuitry1142configured for various functions, including, for example, transmitting sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, transmitting the first data information on the first set of frequency resources, determining second data information and a second set of frequency resources based on a response received from a receiving device, and transmitting the second data information on the second set of frequency resources. For example, the control/data processing circuitry1142may be configured to implement one or more of the functions described below in relation toFIG. 12, including, e.g., blocks1204,1206,1210, and1212. The processor1104may also include response processing circuitry1146configured for various functions, including, for example, receiving, from the receiving device, a response indicating whether reception of the first data information was successful. For example, the response processing circuitry1146may be configured to implement one or more of the functions described below in relation toFIG. 12, including, e.g., block1208.

In an aspect, the MA signature processing circuitry1140may also be configured for detecting a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices, wherein the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource. For example, the MA signature processing circuitry1140may be configured to implement one or more of the functions described below in relation toFIG. 13, including, e.g., block1304. In an aspect, the control/data processing circuitry1142may be configured for receiving one or more sidelink control information on a first set of frequency resources from one or more transmitting devices, receiving, or attempting to receive, the first data information on the first set of frequency resources, and receiving second data information on a second set of frequency resources. For example, the control/data processing circuitry1142may be configured to implement one or more of the functions described below in relation toFIG. 13, including, e.g., blocks1302and1312. The processor1104may also include SINR determining circuitry1144configured for various functions, including, for example, determining, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of the first data information associated with the corresponding sidelink control information and determining a likelihood of successfully receiving the first data information based on the determined SINR. For example, the SINR determining circuitry1144may be configured to implement one or more of the functions described below in relation toFIG. 13, including, e.g., blocks1306and1308. In an aspect, the response processing circuitry1146may also be configured for transmitting a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful. For example, the response processing circuitry1146may be configured to implement one or more of the functions described below in relation toFIG. 13, including, e.g., block1310.

The processor1104is responsible for managing the bus1102and general processing, including the execution of software stored on the computer-readable medium1106. The software, when executed by the processor1104, causes the processing system1114to perform the various functions described below for any particular apparatus. The computer-readable medium1106and the memory1105may also be used for storing data that is manipulated by the processor1104when executing software.

In one or more examples, the computer-readable storage medium1106may include multiple access (MA) signature processing instructions1150, control/data processing instructions1152, SINR determining instructions1154, and response processing instructions1156configured for various functions. For example, the MA signature processing instructions1150may be configured to implement one or more of the functions described in relation toFIG. 12, including, e.g., block1202andFIG. 13, including, e.g., block1304. The control/data processing instructions1152may be configured to implement one or more of the functions described in relation toFIG. 12, including, e.g., blocks1204,1206,1210, and1212andFIG. 13, including, e.g., blocks1302and1312. The SINR determining instructions1154may be configured to implement one or more of the functions described in relation toFIG. 13, including, e.g., blocks1306and1308. The response processing instructions1156may be configured to implement one or more of the functions described in relation toFIG. 12, including, e.g., block1208andFIG. 13, including, e.g., block1310.

FIG. 12is a flow chart illustrating an exemplary process1200for channel access at a transmitting device in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process1200may be carried out by the UE1100illustrated inFIG. 11. In some examples, the process1200may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block1202, the transmitting device determines a multiple access (MA) signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource.

At block1204, the transmitting device transmits sidelink control information using the MA signature on a first set of frequency resources. The sidelink control information corresponds to first data information. In an aspect, when transmitting the sidelink control information, the transmitting device also determines a length of the MA signature and/or a number of reference symbols to use for transmitting the sidelink control information. The transmitting device may determine such information via reception of a radio resource control (RRC) configuration message. In another aspect, when transmitting the sidelink control information, the transmitting device also determines a reference symbol (RS) sequence, and determines the first set of frequency resources to use for transmitting the RS sequence based on the MA signature. In a further aspect, when transmitting the sidelink control information, the transmitting device may also determine a sequence identifier, a time domain orthogonal cover code (TD-OCC), a frequency domain orthogonal cover code (FD-OCC), and/or a cyclic shift to use for transmitting the sidelink control information. Such information may be determined via reception of a RRC configuration message.

In an aspect, the RS sequence is used to demodulate the sidelink control information at a receiving device. The RS sequence is also used to measure a signal-to-interference-plus-noise ratio (SINR) of the first data information at the receiving device. The RS sequence may be determined based on the MA signature.

At block1206, the transmitting device transmits the first data information on the first set of frequency resources. At block1208, the transmitting device receives, from the receiving device, a response indicating whether reception of the first data information was successful. In an aspect, the response is based on the actual/successful decoding or the likelihood of successful decoding of the first data information at the receiving device.

In an aspect, the response is based on a signal-to-interference-plus-noise ratio (SINR) detected on the first set of frequency resources used to transmit the first data information. In an aspect, when receiving the response, the transmitting device may receive a negative acknowledgement (NACK) if reception was not successful and receive no response transmission if reception was successful. In another aspect, when receiving the response, the transmitting device may receive the NACK if reception was not successful and receive an acknowledgement (ACK) if reception was successful. In a further aspect, when receiving the response, the transmitting device may receive an indication to reselect a different set of frequency resources for transmitting data if reception was not successful and receive an indication to continue using the first set of frequency resources for transmitting data if reception was successful.

At block1210, the transmitting device determines second data information and a second set of frequency resources based on the response received from the receiving device. At block1212, the transmitting device transmits the second data information on the second set of frequency resources. In an aspect, if the response received from the receiving device is the NACK, then the second data information is the same as the first data information. In another aspect, if the response received from the receiving device is the ACK or no response transmission is received, then the second data information is different from the first data information and the second set of frequency resources is the same as the first set of frequency resources. In a further aspect, the response is received in a transmission time interval (TTI). Accordingly, the transmitting device may further determine whether a next TTI is available for transmission based on the response received in the TTI.

In one configuration, the apparatus1100for wireless communication includes means for determining a multiple access (MA) signature for distinguishing a transmission of the transmitting device from another transmission of another transmitting device on a same frequency resource, means for transmitting sidelink control information using the MA signature on a first set of frequency resources, the sidelink control information corresponding to first data information, means for transmitting the first data information on the first set of frequency resources, means for receiving, from a receiving device, a response indicating whether reception of the first data information was successful, means for determining second data information and a second set of frequency resources based on the response received from the receiving device, means for transmitting the second data information on the second set of frequency resources, and means for determining whether a next TTI is available for transmission based on the response received in a TTI. In one aspect, the aforementioned means may be the processor1104shown inFIG. 11configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

FIG. 13is a flow chart illustrating an exemplary process1300for channel access at a receiving device in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process1300may be carried out by the UE1100illustrated inFIG. 11. In some examples, the process1300may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block1302, the receiving device receives one or more sidelink control information on a first set of frequency resources from one or more transmitting devices. At block1304, the receiving device detects a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices. In an aspect, the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource.

At block1306, the receiving device determines, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of first data information associated with the corresponding sidelink control information. In an aspect, when determining the SINR, the receiving device may also determine a reference symbol (RS) sequence used to transmit the corresponding sidelink control information. The RS sequence is determined based on the MA signature. The SINR is determined based on the RS sequence. Moreover, the receiving device may demodulate the corresponding sidelink control information using the RS sequence.

At block1308, the receiving device determines a likelihood of successfully receiving the first data information based on the determined SINR. Thereafter, the receiving device may receive, or attempt to receive, the first data information on the first set of frequency resources.

At block1310, the receiving device transmits a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful. In an aspect, when transmitting the response, the receiving device transmits a negative acknowledgement (NACK) if reception was not successful and refrains from transmitting the response if reception was successful. In another aspect, when transmitting the response, the receiving device transmits the NACK if reception was not successful and transmits an acknowledgement (ACK) if reception was successful. In a further aspect, when transmitting the response, the receiving device transmits an indication to reselect a different set of frequency resources for transmitting data if reception was not successful and transmits an indication to continue using the first set of frequency resources for transmitting data if reception was successful.

At block1312, the receiving device receives second data information on a second set of frequency resources. In an aspect, if the response transmitted to the transmitting device is the NACK, then the second data information is the same as the first data information. In a further aspect, if the response transmitted to the transmitting device is the ACK or if no response transmission is transmitted, then the second data information is different from the first data information and the second set of frequency resources is the same as the first set of frequency resources.

In one configuration, the apparatus1100for wireless communication includes means for receiving one or more sidelink control information on a first set of frequency resources from one or more transmitting devices, means for detecting a multiple access (MA) signature used to transmit corresponding sidelink control information from a transmitting device of the one or more transmitting devices, wherein the MA signature distinguishes a transmission of the transmitting device from another transmission of another transmitting device of the one or more transmitting devices on a same frequency resource, means for determining, for the detected MA signature, a signal-to-interference-plus-noise ratio (SINR) of first data information associated with the corresponding sidelink control information, means for determining a likelihood of successfully receiving the first data information based on the determined SINR, means for transmitting a response to the transmitting device based on the likelihood, wherein the response indicates whether reception of the first data information is successful, means for determining a reference symbol (RS) sequence used to transmit the corresponding sidelink control information, wherein the SINR is determined based on the RS sequence, means for demodulating the corresponding sidelink control information using the RS sequence, means for receiving, or attempting to receive, the first data information on the first set of frequency resources, and means for receiving second data information on a second set of frequency resources. In one aspect, the aforementioned means may be the processor1104shown inFIG. 11configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.