Patent Description:
The subject matter disclosed herein relates generally to wireless communications and more particularly relates to transmitting sidelink control information indicating no sidelink data.

In certain wireless communications networks, sidelink control information may be transmitted. Generally, sidelink control information is transmitted with data. D1 (<NPL>, and discusses the design for HARQ transmission, MIMO and CSI, and power control.

Claim <NUM> defines a method and claim <NUM> defines an apparatus. In the following, any method and/or apparatus referred to as embodiments but nevertheless do not fall within the scope of the appended claims are to be understood as examples helpful in understanding the invention.

<FIG> depicts an embodiment of a wireless communication system <NUM> for transmitting sidelink control information indicating no sidelink data. In one embodiment, the wireless communication system <NUM> includes remote units <NUM> and network units <NUM>. Even though a specific number of remote units <NUM> and network units <NUM> are depicted in <FIG>, one of skill in the art will recognize that any number of remote units <NUM> and network units <NUM> may be included in the wireless communication system <NUM>.

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

In certain embodiments, a network unit <NUM> may also be referred to and/or may include one or more of an access point, an access terminal, a base, a base station, a location server, a core network ("CN"), a radio network entity, a Node-B, an evolved node-B ("eNB"), a <NUM> node-B ("gNB"), a Home Node-B, a relay node, a device, a core network, an aerial server, a radio access node, an access point ("AP"), new radio ("NR"), a network entity, an access and mobility management function ("AMF"), a unified data management ("UDM"), a unified data repository ("UDR"), a UDM/UDR, a policy control function ("PCF"), a radio access network ("RAN"), a network slice selection function ("NSSF"), an operations, administration, and management ("OAM"), a session management function ("SMF"), a user plane function ("UPF"), an application function, an authentication server function ("AUSF"), security anchor functionality ("SEAF"), trusted non-3GPP gateway function ("TNGF"), or by any other terminology used in the art.

In one implementation, the wireless communication system <NUM> is compliant with NR protocols standardized in third generation partnership project ("3GPP"), wherein the network unit <NUM> transmits using an OFDM modulation scheme on the downlink ("DL") and the remote units <NUM> transmit on the uplink ("UL") using a single-carrier frequency division multiple access ("SC-FDMA") scheme or an orthogonal frequency division multiplexing ("OFDM") scheme. More generally, however, the wireless communication system <NUM> may implement some other open or proprietary communication protocol, for example, WiMAX, institute of electrical and electronics engineers ("IEEE") <NUM> variants, global system for mobile communications ("GSM"), general packet radio service ("GPRS"), universal mobile telecommunications system ("UMTS"), long term evolution ("LTE") variants, code division multiple access <NUM> ("CDMA2000"), Bluetooth®, ZigBee, Sigfoxx, among other protocols.

According to the invention as claimed, a remote unit <NUM> determines, at a user equipment, that there is no sidelink data available for a destination. The remote unit <NUM> transmits sidelink control information to the destination that indicates that there is no sidelink data available for the destination and triggers a channel state information feedback response from the destination. The remote unit <NUM> monitors for reception of the channel state information feedback response from the destination. Accordingly, the remote unit <NUM> may be used for transmitting sidelink control information indicating no sidelink data.

In certain embodiments, a remote unit <NUM> may receive, at a user equipment, information indicating a discontinuous transmission. In some embodiments, the remote unit <NUM> may increment a discontinuous transmission counter of a radio link failure procedure. In various embodiments, the remote unit <NUM> may start a discontinuous transmission timer. Accordingly, the remote unit <NUM> may be used for a radio link failure procedure.

In certain embodiments, a remote unit <NUM> may perform, at a user equipment, a logical channel prioritization procedure. In some embodiments, the remote unit <NUM> may determine, based on the logical channel prioritization procedure, that a transport block contains only data of logical channels having hybrid automatic repeat request feedback disabled. In various embodiments, the remote unit <NUM> may transmit sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block. Accordingly, the remote unit <NUM> may be used for a logical channel prioritization procedure.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for transmitting sidelink control information indicating no sidelink data. The apparatus <NUM> includes one embodiment of the remote unit <NUM>. Furthermore, the remote unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. In some embodiments, the input device <NUM> and the display <NUM> are combined into a single device, such as a touchscreen. In certain embodiments, the remote unit <NUM> may not include any input device <NUM> and/or display <NUM>. In various embodiments, the remote unit <NUM> may include one or more of the processor <NUM>, the memory <NUM>, the transmitter <NUM>, and the receiver <NUM>, and may not include the input device <NUM> and/or the display <NUM>.

For example, the display <NUM> may include, but is not limited to, a liquid crystal display ("LCD"), a light emitting diode ("LED") display, an organic light emitting diode ("OLED") display, a projector, or similar display device capable of outputting images, text, or the like to a user.

According to the invention as claimed, the processor <NUM> determines that there is no sidelink data available for a destination. The transmitter <NUM> transmits sidelink control information to the destination that indicates that there is no sidelink data available for the destination and triggers a channel state information feedback response from the destination, wherein the processor monitors for reception of the channel state information feedback response from the destination.

In certain embodiments, the receiver <NUM> may receive information indicating a discontinuous transmission. In various embodiments, the processor <NUM> may: increment a discontinuous transmission counter of a radio link failure procedure; and start a discontinuous transmission timer.

In some embodiments, the processor <NUM> may: perform a logical channel prioritization procedure; and determine, based on the logical channel prioritization procedure, that a transport block contains only data of logical channels having hybrid automatic repeat request feedback disabled. In various embodiments, the transmitter <NUM> may transmit sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for transmitting sidelink control information indicating no sidelink data. The apparatus <NUM> includes one embodiment of the network unit <NUM>. Furthermore, the network unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. As may be appreciated, the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> may be substantially similar to the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> of the remote unit <NUM>, respectively.

In some embodiments, such as using a user equipment ("UE") to network ("Uu") interface (e.g., NR, LTE), radio link monitoring ("RLM") may be performed. If a RLM procedure indicates that the UE is out of sync with respect to DL (e.g., a hypothetical block error rate ("BLER") target for a physical downlink control channel ("PDCCH") exceeds a threshold such as <NUM>%) for a time duration, the UE may declare a radio link failure ("RLF") and may initiate a recovery procedure. The recovery on Uu may include trying to re-establish a radio resource control ("RRC") connection on a different cell. In direct communication between UEs ("PC5"), it may be meaningful to perform radio link monitoring to determine if a radio link between two UEs is sufficiently good and, if not, the UEs may not unnecessarily attempt transmission to the other UE. In certain embodiments, after having declared RLF, UEs may immediately or later clear a context for another UE and free memory space.

In various embodiments, a RLF mechanism at a transmit ("TX") UE may be based on hybrid automatic repeat request ("HARQ") feedback. In certain embodiments, a TX UE counts a number of consecutive discontinuous transmissions ("DTX") received from a receive ("RX") UE in response to a physical sidelink shared channel ("PSSCH") transmission. In some embodiments, RLF may be declared and subsequent actions may be carried out if a counter exceeds a predefined threshold (e.g., x number of consecutive DTX received from the RX UE for a specific link and/or connection).

In certain embodiments, channel state information ("CSI") reporting may be used. A sidelink channel state information ("SL-CSI") reporting procedure may be used to provide a peer UE with sidelink channel state information. In various embodiments, a MAC entity may, for each pair of the source layer-<NUM> identifier ("ID") and the destination layer-<NUM> ID: if the SL-CSI reporting has been triggered by a SCI and not cancelled: <NUM>) if the MAC entity has SL resources allocated for new transmission: a) instruct the multiplexing and assembly procedure to generate a sidelink CSI reporting MAC CE; b) cancel the triggered SL-CSI reporting; <NUM>) else if the MAC entity has been configured by RRC to transmit using a SL-RNTI or SLCS-RNTI: trigger a scheduling request.

In some embodiments, an SCI format <NUM>-<NUM> may be used for scheduling PSSCH and <NUM>nd-stage-SCI on PSSCH. The following information may be transmitted using the SCI format <NUM>-<NUM>: <NUM>) priority - <NUM> bits; <NUM>) frequency resource assignment - <MAT> bits if the value of the higher layer parameter sl-MaxNumPerReserve is configured to <NUM>; otherwise <MAT> if the value of the higher layer parameter sl-MaxNumPerReserve is configured to <NUM>; <NUM>) time resource assignment - <NUM> bits if the value of the higher layer parameter sl-MaxNumPerReserve is configured to <NUM>; otherwise <NUM> bits if the value of the higher layer parameter sl-MaxNumPerReserve is configured to <NUM>; <NUM>) resource reservation period - <MAT> bits if higher parameter sl-MultiReserveResource is configured; <NUM> bits otherwise; <NUM>) demodulation reference signal ("DMRS") pattern - [x] bits if more than one DMRS pattern is configured by higher layer parameter sl-PSSCH-DMRS-TimePattern; <NUM> bits otherwise; <NUM>) 2nd-stage SCI format - [x] bits; <NUM>) beta_offset indicator - [<NUM>] bits as provided by higher layer parameter sl-BetaOffsets2ndSCI; <NUM>) number of DMRS ports - <NUM> bit; <NUM>) modulation and coding scheme - <NUM> bits; and <NUM>) reserved - [<NUM> - <NUM>] bits as determined by higher layer parameter sl-NumReservedBits with value set to zero.

In various embodiments, SCI format <NUM>-<NUM> is used for the decoding of a PSSCH transmission. The following information may be transmitted by means of the SCI format <NUM>-<NUM>: HARQ process ID - [x] bits; new data indicator - <NUM> bit; redundancy version - <NUM> bits; source ID - <NUM> bits; destination ID - <NUM> bits; CSI request - <NUM> bit; if the 2nd-stage SCI format field in the corresponding SCI format <NUM>-<NUM> indicates type <NUM> groupcast, the following fields are present: zone ID - <NUM> bits; and communication range requirement - <NUM> bits.

In various embodiments, there may be an efficient radio link failure ("RLF") mechanism at a transmitter ("TX") user equipment ("UE") if the TX UE sends sidelink ("SL") data in a blind retransmission mode and hybrid automatic repeat request ("HARQ") feedback is disabled. In some embodiments, determining whether a transport block ("TB") is transmitted using a HARQ feedback mode depends on the configuration of a highest priority logical channel within a TB (e.g., it may happen that a UE uses blind retransmissions for some period of time) for a specific destination. In such embodiments, HARQ feedback may be enabled for every TB transmission for a specific destination.

According to the invention as claimed, channel state information ("CSI") feedback may be considered in addition to a HARQ feedback for a HARQ-based RLF mechanism running at a TX UE. In the absence of SL data for a destination for which the HARQ-based RLF procedure is running, the TX UE signals sidelink control information ("SCI") for the destination with a CSI request bit set to '<NUM>' (e.g., asking for CSI information). If the TX UE doesn't receive a CSI report from a receiver ("RX") UE even though requested, the TX UE considers the absence of a CSI medium access control ("MAC") control element ("CE") the same as a discontinuous reception ("DTX") for the HARQ-based RLF procedure. Moreover, if a MAC protocol data unit ("PDU") is sent to the RX UE without HARQ feedback support (e.g., using a blind retransmission mode) a CSI report may be used for the RLF procedure (e.g., the absence of a requested CSI report is considered and/or handled as being a DTX).

In a second embodiment, SCI-only may be transmitted without a corresponding physical sidelink shared channel ("PSSCH") transmission. To save sidelink ("SL") resources only the SCI without any PSSCH transmission may be sent. In such an embodiment, the SCI-only may be used if there is no SL data available for a destination and a TX UE wants to trigger HARQ feedback transmission of an RX UE for RLF measurements and/or procedures (e.g., HARQ-based RLF procedure). In one embodiment of the second embodiment, to reduce transmission power and to reduce interference, the TX UE may signal only SCI without a physical sidelink shared channel ("PSSCH") transmission. Upon reception of SCI-only, the RX UE may acknowledge the reception of the SCI by sending a hybrid automatic repeat request ("HARQ") acknowledgement ("ACK"). In some embodiments of the second embodiment, the SCI indicates that there is no associated PSSCH transmission (e.g., one of the reserved bits in a first stage SCI may be used to indicate the absence of the PSSCH transmission). In certain embodiments of the second embodiment, a field of the SCI or a combination of fields of the SCI is set to predefined values indicating the absence of the PSSCH transmission.

In a third embodiment, a UE starts a timer after having received a DTX from an RX UE and having incremented a DTX counter of a RLF procedure. Upon reception of a HARQ feedback (e.g., ACK and/or negative acknowledgement ("NACK")) or DTX, the timer is stopped if an ACK and/or NACK is received or restarted with reception of a next DTX. When the timer expires, the UE resets the DTX counter used for RLF detection to zero. The timer may be used to account for circumstances in which some TBs are transmitted in a blind retransmission mode where no HARQ feedback is received from RX UEs.

In a fourth embodiment, a UE may indicate within SCI that HARQ feedback is enabled, even though as a result of a logical channel prioritization ("LCP") procedure the TB contains only data of logical channels ("LCHs") for which HARQ feedback is disabled. As may be appreciated, overriding a LCH configuration by a network may be useful if HARQ feedback is required for a RLF mechanism to work properly. In one embodiment of the fourth embodiment, a TX UE may use a mixed mode of operation for transmission of a TB, where the TX UE asks for HARQ feedback from the RX UE after a certain number of blind retransmissions. The number of (re)transmissions after which TX UE requests HARQ feedback, e.g., HARQ feedback is enabled for any further retransmission, may be preconfigured or determined by the TX UE. In another embodiment of the fourth embodiment, the TX UE may enable SL HARQ feedback based on a distance between multiple resources indicated in DCI (e.g., if a distance between multiple resource is such that it could fulfil HARQ round trip reception timing, then SL HARQ feedback is enabled by the TX UE).

As may be appreciated, any of the embodiments described herein may be configurable for a given destination identifier ("ID"), pair of source layer-<NUM> ID and destination layer-<NUM> ID corresponding to a UE to UE interface ("PC5") radio resource control ("RRC") connection and/or SL LCH. For specific destinations and/or LCHs, a UE may rely on upper layer keep alive messages.

<FIG> is a flow chart diagram illustrating one embodiment of a method <NUM> for transmitting sidelink control information indicating no sidelink data. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

In various embodiments, the method <NUM> includes determining <NUM>, at a user equipment, that there is no sidelink data available for a destination. In some embodiments, the method <NUM> includes, transmitting <NUM> sidelink control information to the destination that indicates that there is no sidelink data available for the destination and triggers a channel state information feedback response from the destination. In certain embodiments, the method <NUM> includes monitoring <NUM> for reception of the channel state information feedback response from the destination.

In certain embodiments, the sidelink control information comprises a channel state information request bit that indicates a request for a channel state information feedback response.

According to the invention as claimed, the method further comprises, in response to monitoring for reception of the channel state information feedback response resulting in not receiving the channel state information feedback response, indicating a discontinuous transmission.

<FIG> is a flow chart diagram illustrating one embodiment of a method <NUM> for a radio link failure procedure. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

In various embodiments, the method <NUM> includes receiving <NUM>, at a user equipment, information indicating a discontinuous transmission. In some embodiments, the method <NUM> includes incrementing <NUM> a discontinuous transmission counter of a radio link failure procedure. In certain embodiments, the method <NUM> includes starting <NUM> a discontinuous transmission timer.

In certain embodiments, the method further comprises stopping the discontinuous transmission timer in response to receiving hybrid automatic repeat request feedback. In some embodiments, the method further comprises restarting the discontinuous transmission timer in response to receiving information indicating a second discontinuous transmission. In various embodiments, the method further comprises, in response to the discontinuous transmission timer expiring, resetting the discontinuous transmission counter to zero.

<FIG> is a flow chart diagram illustrating one embodiment of a method <NUM> for a logical channel prioritization procedure. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

In various embodiments, the method <NUM> includes performing <NUM>, at a user equipment, a logical channel prioritization procedure. In some embodiments, the method <NUM> includes determining <NUM>, based on the logical channel prioritization procedure, that a transport block contains only data of logical channels having hybrid automatic repeat request feedback disabled. In certain embodiments, the method <NUM> includes transmitting <NUM> sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block.

In certain embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled after transmitting a predetermined number of blind retransmissions. In some embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled in response to a distance between resources being less than a threshold distance.

In one embodiment, a method comprises: determining, at a user equipment, that there is no sidelink data available for a destination; transmitting sidelink control information to the destination that indicates that there is no sidelink data available for the destination and triggers a channel state information feedback response from the destination; and monitoring for reception of the channel state information feedback response from the destination.

In some embodiments, the method further comprises, in response to monitoring for reception of the channel state information feedback response resulting in not receiving the channel state information feedback response, indicating a discontinuous transmission.

In one embodiment, an apparatus comprises a user equipment, the apparatus further comprises: a processor that determines that there is no sidelink data available for a destination; and a transmitter that transmits sidelink control information to the destination that indicates that there is no sidelink data available for the destination and triggers a channel state information feedback response from the destination; wherein the processor monitors for reception of the channel state information feedback response from the destination.

In some embodiments, the processor, in response to monitoring for reception of the channel state information feedback response resulting in not receiving the channel state information feedback response, indicates a discontinuous transmission.

In one embodiment, a method comprises: receiving, at a user equipment, information indicating a discontinuous transmission; incrementing a discontinuous transmission counter of a radio link failure procedure; and starting a discontinuous transmission timer.

In certain embodiments, the method further comprises stopping the discontinuous transmission timer in response to receiving hybrid automatic repeat request feedback.

In some embodiments, the method further comprises restarting the discontinuous transmission timer in response to receiving information indicating a second discontinuous transmission.

In various embodiments, the method further comprises, in response to the discontinuous transmission timer expiring, resetting the discontinuous transmission counter to zero.

In one embodiment, an apparatus comprises a user equipment, the apparatus further comprises: a receiver that receives information indicating a discontinuous transmission; and a processor that: increments a discontinuous transmission counter of a radio link failure procedure; and starts a discontinuous transmission timer.

In certain embodiments, the processor stops the discontinuous transmission timer in response to receiving hybrid automatic repeat request feedback.

In some embodiments, the processor restarts the discontinuous transmission timer in response to receiving information indicating a second discontinuous transmission.

In various embodiments, the processor, in response to the discontinuous transmission timer expiring, resets the discontinuous transmission counter to zero.

In one embodiment, a method comprises: performing, at a user equipment, a logical channel prioritization procedure; determining, based on the logical channel prioritization procedure, that a transport block contains only data of logical channels having hybrid automatic repeat request
feedback disabled; and transmitting sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block.

In certain embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled after transmitting a predetermined number of blind retransmissions.

In some embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled in response to a distance between resources being less than a threshold distance.

In one embodiment, an apparatus comprises a user equipment, the apparatus further comprises: a processor that: performs a logical channel prioritization procedure; and determines, based on the logical channel prioritization procedure, that a transport block contains only data of logical channels having hybrid automatic repeat request feedback disabled; and a transmitter that transmits sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block.

In certain embodiments, the transmitter transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises the transmitter transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled after transmitting a predetermined number of blind retransmissions.

In some embodiments, the transmitter transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises the transmitter transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled in response to a distance between resources being less than a threshold distance.

Claim 1:
A method (<NUM>) performed by a user equipment, UE, the method comprising:
determining (<NUM>) that there is no sidelink data available for a destination;
transmitting (<NUM>) sidelink control information, SCI, to the destination, wherein the SCI indicates that there is no sidelink data available for the destination and triggers a channel state information, CSI, feedback response from the destination;
monitoring (<NUM>) for reception of the CSI feedback response from the destination; and
indicating a discontinuous transmission, DTX, in response to monitoring for reception of the CSI feedback response resulting in not receiving the CSI feedback response.