Patent Description:
The present disclosure relates generally to communication systems, and more particularly, to methods and apparatus related to feedback for vehicle-to-everything (V2X) communication or vehicle-to-vehicle (V2V) communication.

Aspects of wireless communication may comprise direct communication between devices, such as in V2X, V2V, and/or D2D communication. There exists a need for further improvements in V2X, V2V, and/or D2D technology. Patent application <CIT> relates to a sidelink signal communication scheme that provides for rapid adaptation of the sidelink transmission based on feedback received during each transmission time interval. In this way, a lack of precision in interference measurements, or rapid changes in the amount of interference, which otherwise might cause a modulation and coding scheme that was selected for the sidelink transmission to be unsuitable, may be adapted to improve the reliability of the transmission.

The invention is described by its independent claims. Preferred embodiments are stipulated by their dependent claims.

Various features and aspects related to a front loaded Channel State Information-Reference Signal (CSI-RS) based feedback in a wireless communication system (e.g., including vehicular systems such as vehicle-to-vehicle (V2V) and/or vehicle-to-everything (V2X) networks) are described. For example, a user equipment (UE) may apply channel knowledge based on received feedback to adjust a modulation and coding scheme (MCS), modulation, code rate, rank and/or precoding to improve performance beyond a single port, non-precoded transmission. For example, a link level scheme may be used that applies precoding based on feedback received from a receiver UE. The feedback may be based on the CSI-RS transmissions in a first Transmission Time Interval (TTI) and may be used to determine improved transmission precoding, rank, etc. Closed Loop Spatial Multiplexing (CLSM) may improve performance, e.g., if link adaptation is accurately mapped to the channel. For example, the front loaded CSI-RS based feedback may enable the transmitter UE to adapt precoding and/or rank based on feedback for any of a Precoding Matrix Indicator (PMI), a rank indicator(RI), or a Channel Quality Indicator (CQI).

1A is a diagram illustrating an example of a wireless communications system and an access network <NUM>. The wireless communications system (also referred to as a wireless wide area network (WWAN)) includes base stations <NUM>, UEs <NUM>, an Evolved Packet Core (EPC) <NUM>, and a Core Network (e.g., 5GC) <NUM>.

The base stations <NUM> configured for <NUM> LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC <NUM> through backhaul links <NUM> (e.g., S1 interface). The base stations <NUM> configured for NR (collectively referred to as Next Generation RAN (NG-RAN)) may interface with Core Network <NUM> through backhaul links <NUM>. The base stations <NUM> may communicate directly or indirectly (e.g., through the EPC <NUM> or Core Network <NUM>) with each other over backhaul links <NUM> (e.g., X2 interface).

A network that includes both small cell and macro cells may be known as a heterogeneous network. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

A base station <NUM>, whether a small cell <NUM>' or a large cell (e.g., macro base station), may include an eNB, gNodeB (gNB), or other type of base station.

Devices may use beamforming to transmit and receive communication. For example, FIG. 1A illustrates that a base station <NUM> may transmit a beamformed signal to the UE <NUM> in one or more transmit directions <NUM>'. Although beamformed signals are illustrated between UE <NUM> and base station <NUM>/<NUM>, aspects of beamforming may similarly may be applied by UE <NUM> or RSU <NUM> to communicate with another UE <NUM> or RSU <NUM>, such as based on V2X, V2V, or D2D communication.

The Core Network <NUM> may include a Access and Mobility Management Function (AMF) <NUM>, other AMFs <NUM>, a Session Management Function (SMF) <NUM>, and a User Plane Function (UPF) <NUM>. The AMF <NUM> is the control node that processes the signaling between the UEs <NUM> and the Core Network <NUM>.

The base station <NUM> provides an access point to the EPC <NUM> or Core Network <NUM> for a UE <NUM>.

Some wireless communication networks may include vehicle-based communication devices that can communicate from vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) (e.g., from the vehicle-based communication device to road infrastructure nodes such as a Road Side Unit (RSU)), vehicle-to-network (V2N) (e.g., from the vehicle-based communication device to one or more network nodes, such as a base station), and/or a combination thereof and/or with other devices, which can be collectively referred to as vehicle-to-anything (V2X) communications. Referring again to <FIG>, in certain aspects, a UE <NUM>, e.g., a transmitting Vehicle User Equipment (VUE) or other UE, may be configured to transmit messages directly to another UE <NUM>. The communication may be based on V2V/V2X/V2I or other D2D communication, such as Proximity Services (ProSe), etc. Communication based on V2V, V2X, V2I, and/or D2D may also be transmitted and received by other transmitting and receiving devices, such as Road Side Unit (RSU) <NUM>, etc. Aspects of the communication may be based on PC5 or sidelink communication e.g., as described in connection with any of the examples in <FIG>.

Referring again to FIG. 1A, in certain aspects, a first UE <NUM> (e.g., such as the UE <NUM> which may be a vehicle or a device installed in a vehicle in a V2V/V2X network) may communicate with a second UE (e.g., such as the UE <NUM>' which may be a vehicle or a device installed in a vehicle in a V2V/V2X network) using V2X communication or a V2V communication link <NUM>. For example, the first UE <NUM> may transmit a first data transmission and a first reference signal to a second UE <NUM>', and receive a feedback from the second UE <NUM>' based on the first reference signal. The first UE <NUM> may comprise an adapting component <NUM> configured to adapt one or more transmission parameters based on the feedback received from the second UE. The first UE <NUM> may transmit a second data transmission with the adapted transmission parameter(s) to the second UE <NUM>'. In some aspects, the second UE <NUM>' may receive the first data transmission and the first reference signal from the first UE <NUM>. The second UE <NUM>' may comprise a feedback component <NUM> configured to transmit the feedback, via a transmission component, to the first UE <NUM> based on the first reference signal. The second UE <NUM>' may receive the second data transmission from the first UE <NUM>. For example, the second data transmission may have adjusted transmission parameter(s) based on the feedback.

<FIG> are diagrams 100b, 100c, and 100d illustrating examples of nonstandalone (NSA) architecture deployment which may be used in the access network of <NUM> of FIG. In some configurations, the UE <NUM> may simultaneously connect to a first base station (e.g., eNB) via a first radio access technology (RAT) and a second base station (e.g., gNB) via a second RAT, as shown in <FIG>. For example, the first RAT may comprise and/or support LTE wireless access technology, and the second RAT may comprise and/or support <NUM> NR wireless access technology.

<FIG> illustrates a first option of an NSA architecture deployment that may be used in the access network <NUM> in some configurations. In this option, base station <NUM> (e.g., gNB) may have an S1-U connection to the core network (e.g., EPC <NUM>) via the SGW <NUM>/PGW <NUM>. Base station <NUM> (e.g., eNB) may have an S1-MME connection to the EPC <NUM> via the MME <NUM>. This configuration may comprise a DC, split bearer. Thus, with this option, the data may go through both the first base station <NUM> via LTE and the second base station <NUM> via <NUM> NR. The data may combine, or merge at the second base station <NUM>, because the dual connectivity split bearer is anchored at the second base station <NUM>. The consolidated data may be sent to the core network EPC <NUM> by the second base station <NUM>.

<FIG> illustrates a second option of the NSA architecture deployment that may be used in the access network <NUM> in some configurations. In this option, data may similarly go through both the first base station <NUM> via LTE and the second base station <NUM> via <NUM> NR. However, in this example, the data may combine, or merge at the first base station <NUM> because the dual connectivity split bearer is anchored at the first base station <NUM>. The consolidated data may be sent to the core network EPC <NUM> by the first base station <NUM>.

<FIG> illustrates a third option of the NSA architecture deployment that may be used in the access network <NUM> in some configurations. In this option, the data may go through the second base station <NUM>, and the second base station <NUM> may send the data the core network EPC <NUM>.

<FIG> is a block diagram <NUM> of a first wireless communication device <NUM> in communication with a second wireless communication device <NUM>, e.g., via V2V/V2X/D2D communication. The device <NUM> may comprise a transmitting device communicating with a receiving device, e.g., device <NUM>, via V2V/V2X/D2D communication. The communication may be based, e.g., on sidelink. The transmitting device <NUM> may comprise a UE, an RSU, etc. The receiving device may comprise a UE, an RSU, etc. Packets may be provided to a controller/processor <NUM> that implements layer <NUM> and layer <NUM> functionality.

At least one of the TX processor <NUM>, the RX processor <NUM>, or the controller/processor <NUM> of device <NUM> or the TX <NUM>, the RX processor <NUM>, or the controller/processor <NUM> may be configured to perform aspects described in connection with <NUM>, or <NUM> of <FIG>.

Described herein are various features and aspects related to a front loaded Channel State Information-Reference Signal (CSI-RS) based feedback in a wireless communication system (e.g., including vehicular systems such as vehicle-to-vehicle (V2V) and/or vehicle-to-everything (V2X) networks). For example, NR V2X may include unicast transmissions for which high throughput and high efficiency are beneficial. If a single port, non-precoded transmission is used, the data rate, capacity, or special efficiency may be limited. Aspects presented herein improve performance to achieve higher data rate, capacity, or special efficiency in communication. For example, the link design aspects presented herein may help V2X/V2V/D2D communication to have higher efficiency to support high spectral efficiencies at high speeds and high carrier frequencies.

A transmitting UE may apply channel knowledge based on received feedback to adjust an MCS, modulation, code rate, rank and/or precoding to improve performance beyond a single port, non-precoded transmission. For example, a link level scheme may be used that enables the transmitting UE to apply precoding based on feedback received directly from a receiver UE. The feedback may be based on the CSI-RS transmissions in a first TTI and may be used to determine improved transmission precoding, rank, etc. Applying channel knowledge to the an MCS, modulation, code rate, rank and/or precoding determination may advantageously improve performance over a single port non-precoded transmission. In this way, the data rate, capacity, or special efficiency in communication may be improved.

In some aspects, CLSM may improve performance, e.g., if link adaptation is accurately mapped to the channel. In some aspects, the front loaded CSI-RS based feedback may enable the transmitter UE to adapt precoding and/or rank based on feedback for any of a Precoding Matrix Indicator (PMI), a rank indicator (RI), or a Channel Quality Indicator (CQI).

<FIG> illustrates a diagram <NUM> of an example of signaling between UEs (e.g., UEs <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) based on V2X/V2V/D2D communication. In one aspect, a first UE <NUM>, which may be a vehicle or a device installed in a vehicle in a V2V/V2X network, may transmit a first data transmission <NUM> and a first reference signal <NUM> directly to a second UE <NUM>, e.g., in a first TTI, receive a feedback <NUM> from the second UE <NUM> based on the first reference signal <NUM>, to adapt one or more transmission parameters based on the feedback <NUM> received from the second UE <NUM>, and to transmit a second data transmission <NUM> directly to the second UE <NUM>, e.g., in the second TTI or a subsequent TTI. In some aspects, the second UE <NUM> may receive the first data transmission <NUM> and the first reference signal <NUM> directly from the first UE <NUM>, transmit the feedback <NUM> to the first UE <NUM> based on the first reference signal <NUM>, and receive the second data transmission <NUM> directly from the first UE <NUM>, e.g., in the second TTI or a subsequent TTI. For example, the first UE <NUM> may communicate with the second UE <NUM> using V2X communication or V2V communication.

<FIG> illustrates a diagram 500a of example link designs for a bundled TTI comprising a first TTI 501a and a second TTI 503a. <FIG> illustrates a first example reference signal pattern <NUM>, a second example reference signal pattern <NUM>, and a third example reference signal pattern <NUM>. For V2X communication or V2V communication, aspects of the link design may enable high efficiency to support high spectral efficiencies at high speeds and a high carrier frequency. The frame structure illustrated in <FIG> may be used, e.g., for sidelink communication. <FIG> illustrates two TTIs, each being <NUM> and including <NUM> symbols. A TTI may correspond to a slot. A resource grid may be used to represent a frame structure. The resource grid may include a resource block (RB) (also referred to as physical RBs (PRBs)) that extend <NUM> consecutive subcarriers. The resource grid may be divided into multiple resource elements (REs). The number of bits carried by each RE may depend on a modulation scheme. As illustrated, REs may be used to transmit control reference signals and. A gap may be provided that enables a device to switch from operating as a transmitting device to prepare to operate as a receiving device. Data may be transmitted in the remaining REs, e.g., as illustrated. Multiple TTIs may be aggregated together. <FIG> illustrates an aggregation of two TTIs. However, the aggregated number of TTIs may be larger than two. As well, multiple RBs may be used for transmissions.

The bundled TTI may comprise at least one symbol for control signaling 506a. As illustrated, the control signaling 506a may be comprised in the first TTI 501a. Each TTI 501a, 503a may comprise data 508a and reference signals 507a. <FIG> illustrates a number of examples having different densities of reference signals 507a within the data 508a, such as in example <NUM> or <NUM> in comparison to example <NUM>. For example, as illustrated in <FIG>, for higher speed, reference signals 507a may be transmitted in a more dense pattern. The bundled TTI may be used for improved link budget and reduced overhead. Interference may change every TTI. Thus, a reference signal pattern may be chosen for each TTI. Channel and noise may be estimated for each TTI. For example, the control 506a may be configured to indicate a number of TTI bundles and RS pattern, transparent mode (TM), a modulation and coding scheme (MCS), a number of ports, a number of layers for data, CSI-RS configuration, feedback mode, etc. A symbol may be used as a gap period 509a to allow for the transmitter UE and receiver UE to turnaround from transmit-to-receive or vice-versa, respectively, or to accommodate for ACK/NACK feedback from a receiving UE in one of the previous TTIs.

<FIG> illustrate an example 500b of a link design including a front loaded CSI-RS based feedback <NUM> in a bundled TTI comprising a first TTI 501b and a second TTI 503b. For example, NR V2X communication may include unicast transmissions for which high throughput and high efficiency are beneficial. Applying channel knowledge to the an MCS, modulation, code rate, rank and/or precoding determination can advantageously improve performance over a single port non-precoded transmission. Closed loop spatial multiplexing can improve performance if link adaptation is accurately mapped to the channel. The TTI may comprise a first control signaling <NUM>. The control signaling <NUM> may be similar to control signaling 506a in <FIG>. The transmitter UE may transmit a first data transmission <NUM> and a first reference signal <NUM> directly to a receiver UE, e.g., in the first TTI 501b. The first reference signal may comprise CSI-RS. The first reference signal may also comprise another reference signal to assist the UE in decoding the data, e.g., such as CRS or DMRS. The receiver UE may transmit feedback <NUM> based on the first reference signal <NUM>. For example, the receiver UE may determine precoding and/or rank and/or channel quality based on CSI-RS in <NUM>, and send the information in the feedback <NUM>. For example, the front loaded CSI-RS based feedback <NUM> can enable the transmitter UE to adapt an MCS, modulation, code rate, rank and/or precoding within bundled TTI based on in-time precoding/rank/channel quality (PMI/RI/CQI) feedback <NUM>. The transmitter UE may also adapt a DMRS pattern density. The feedback <NUM> may also provide speed/velocity information to aid the transmitter UE in selecting the right pattern. The feedback <NUM> may comprise one or more of a PMI, a RI, or a CQI.

As shown in <FIG>, the link level scheme may apply precoding based on the feedback <NUM> received from the receiver UE. The feedback <NUM> may be used by the transmitting UE to determine adapted transmission precoding/rank based on the CSI-RS transmissions in the first TTI 501b. As shown in <FIG>, the feedback <NUM> may be transmitted in the second TTI, e.g., in a first symbol in the second TTI 503b. For example, the feedback <NUM> may be transmitted after an acknowledgment or Negative acknowledgment (ACK/NACK) feedback <NUM> from the receiver UE.

The transmitter UE may also transmit additional reference signals, e.g., a third reference signal. in the first TTI. For example, the third reference signal may be configured for decoding data in the first TTI 501b, and the CSI-RS may be multiplexed with the third reference signal. Thus, both reference signals may be transmitted together in the same symbol(s).

For example, the first reference signal <NUM> might not comprise precoding. For another example, the first reference signal may be beamformed with a specific precoding that is known to the receiver UE. As an example, the first reference signal may comprise a cyclical precoding mechanism or a semi-static precoding known to the first UE. <FIG> illustrates that the reference signal may cycle through precoding, e.g., based on a defined codebook. <FIG> illustrates an index of <NUM>, <NUM>, <NUM>, <NUM> corresponding to four ports. In other examples, different numbers of layers may be used. In an example with two layers, indices <NUM> and <NUM> might not be transmitted. For example, precoding may also be signaled as part of control signaling if the same precoding is likely to be applied across the allocation. For example, the order of precoder cycling may be agreed among the transmitter UE and the receiver UE.

In some aspects, the transmitter UE may receive the feedback <NUM> and adapt one or more transmission parameters, e.g., for a second data transmission <NUM> in the second TTI 503b, based on the feedback <NUM> received from the receiver UE. The transmitter UE may transmit the second data transmission to the receiver UE, e.g., in the second TTI 503b. For example, the first UE <NUM> may communicate with the second UE <NUM> using V2X communication or V2V communication.

For example, the transmitter UE may transmit a second reference signal <NUM> to the receiver UE in the second TTI 503b. The second reference signal may have one or more parameters that have been adjusted based on the feedback <NUM>, corresponding to the adjustment made for the data <NUM>. For example, the second reference signal may comprise precoding adapted based on the feedback <NUM>. The second reference signal may be precoded to indicate any change in PMI/RI/CQI. The second TTI 503b may also comprise a second control signaling <NUM>.

As shown in <FIG>, the transmitter UE may transmit a first control signal <NUM> (control-A) indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping and a precoding type. For example, the first control signal may be transmitted in the first TTI 501b. An adjustment to the one or more transmission parameters may also be indicated in control signals. For example, the transmitter UE may further transmit a second control signal <NUM> indicating an adjustment to the one or more transmission parameters for the second data transmission <NUM> based on the feedback <NUM>. For example, the second control signal <NUM> may be transmitted in the second TTI 503b. For example, the one or more transmission parameters adapted based on the feedback <NUM> may comprise one or more of a PMI, a RI, a modulation and coding scheme (MCS), a CQI, a number of layers, a number of ports, and a coding rate.

Once the feedback <NUM> (e.g., PMI/RI/CQI feedback) is received, for example, at the start of the second TTI 503b, the transmitter UE may apply the rank/precoding and/or adaptation to other transmission parameters immediately after a gap, which may pose some implementation challenges. If the transmitter UE cannot apply the link adaptation parameters, then the link adaptation parameters may be applied at the start of a third TTI (not shown). This solution may be applied to a bundled TTI with a larger number of TTIs. For example, the bundled TTI may further comprise a third TTI, and where the transmitter UE further adapts the one or more transmission parameters for the third TTI based on the feedback received from the receiver UE. Thus, the TTI having the adjusted transmission parameters may be separated by at least one TTI from the TTI on which the feedback is based.

In <FIG>, examples of locations of demodulation reference signal (DMRS) in the second TTI 503b are illustrated. Additional DMRS locations can be incorporated for higher speeds and/or MCS without modifying the baseline front loaded feedback design as shown in <FIG>. For example, DMRS <NUM> may be included with different densities, as described in connection with <FIG>. The additional DMRS locations may improve estimation of one or more of the PMI, the RI, or the CQI.

In one aspect, the feedback <NUM> (e.g., PMI/RI/CQI feedback) may be based on a predicted channel quality in the second TTI 503b (or next few TTIs). For example, the feedback from the receiving UE may comprise a prediction of a channel estimate for the second TTI 503b. Since temporal correlations of the channel are known, the PMI/CQI feedback may be based on the predicted channel in the next TTI (or next few TTIs). For example, the channel may be predicted by the receiving UE through interpolation.

<FIG> illustrates another example 500c of a front loaded feedback link design in a bundled TTI comprising a first TTI 501c and a second TTI 503c. In one aspect, the second control signal <NUM> (e.g., Control-B) may be transmitted prior to transmission of a second reference signal <NUM> in the second TTI 503c. For example, the second control signal <NUM> may be transmitted before the DMRS symbol as shown in <FIG>. The DMRS may be used as a reference by the receiving UE for decoding the second control signal, because the second control signal <NUM> may be precoded. Transmitting the second control signal prior to the second reference signal may advantageously allow the transmitter UE some additional time to get the rank/MCS and/or other transmission parameters set up. Additionally or alternatively, the second control signal <NUM> (e.g., Control-B) may be transmitted at the start of the second TTI but without any refined precoding. In this way, the receiver UE may decode the control signal <NUM> while allowing the transmitter UE more time for MCS/rank and/or other transmission parameters adjustments.

<FIG> illustrates another example 500d of a link design including a front loaded CSI-RS based feedback in a bundled TTI comprising a first TTI 501d and a second TTI (not shown). In one aspect, the CSI-RS <NUM> (e.g., a first reference signal) might not be multiplexed with the reference signal <NUM> (e.g., a third reference signal) for data decoding in the 1st TTI 501d, and the CSI-RS <NUM> may be located in another symbol. <FIG> illustrates the transmitter UE transmitting a third reference signal <NUM> in 5th symbol for decoding data in the first TTI 501d, e.g., DM-RS. The transmitter UE may transmit the CSI-RS <NUM> in a separate symbol than the third reference signal, for example, in the 9th symbol as shown in <FIG>.

<FIG> illustrates another example 500e of aspects of a front loaded feedback design in a bundled TTI comprising a first TTI 501e and a second TTI (not shown). In one aspect, the CSI-RS <NUM> (e.g., a first reference signal) may be transmitted in a symbol, e.g., a second symbol, in the first TTI 501e. Transmitting the CSI-RS in the second symbol may advantageously allow more time for the transmitter UE to adapt the transmission parameters (e.g., PMI/RI/CQI).

<FIG> illustrates another example 500f of a front loaded feedback design in a bundled TTI comprising a first TTI 501f and a second TTI 503f. In one aspect, the feedback <NUM> may be transmitted in the first TTI 501f, as shown in <FIG>. For example, the feedback <NUM> may be transmitted prior to an ACK/NACK feedback <NUM> from the receiver UE. Transmitting the feedback <NUM> in the first TTI may advantageously allow more time for the transmitter UE to adjust the transmission parameters (e.g., PMI/RI/CQI), and even possibly regenerate code words.

<FIG> illustrates another example <NUM> of a front loaded feedback link design in a bundled TTI comprising a first TTI <NUM> and a second TTI <NUM>. In one aspect, there may be no control signal transmitted in the first TTI <NUM>. A control signal <NUM> (e.g., Control-B) may be transmitted in a symbol in the second TTI <NUM>. For example, the transmitter UE may transmit a control signal <NUM> in the second TTI <NUM> without transmitting a control signal in the first TTI <NUM>. For example, the first UE may determine a TTI bundle size from the control signal. For example, control information as a whole might be transmitted at the start of the second TTI. For example, a second control signal may not be necessary. For example, control information may contain the necessary data to decode the first TTI as well as the enhanced information to decode data from second TTI onwards. For example, the receiver UE may store the data from the first TTI and attempt decoding only after it has decoded the control information.

Referring to <FIG>, in some aspects, the feedback channel <NUM> can be power controlled. For example the power of the transmitter UE can be modified based on at least one of a received reference signal received power (RSRP), a Received Signal Strength Indicator (RSSI) or a channel Signal-to-Noise Ratio (SNR).

For example, the front loaded CSI-RS based feedback <NUM> may increase overhead. CLSM may be applied when large amounts of data spanning multiple TTIs are to be communicated. For example, CLSM may be applied when the number of TTI is larger than a threshold number. For example, the transmitter UE may determine whether to use the feedback <NUM> to adjust the one or more transmission parameters for the second TTI 503b based on an amount of data to be sent to the receiver UE.

Referring to <FIG>, the front loaded CSI-RS based feedback <NUM> may advantageously enable more efficient communication in the second TTI than in the first TTI. For example, the transmission parameters can be adjusted dynamically based on the feedback that gives a precise reflection of the channel. As a result, the throughput of communication can be increased, and the reliability of the communication can be improved.

The link design including the front loaded CSI-RS based feedback may advantageously improve the throughput of the communication. For example, the transmitter UE may transmit a first control signal (e.g., control-A) in the first TTI, wherein the first control signal may further indicate a potential for early termination of a data transmission. For example, the first control signal (e.g., control-A) may indicate if early termination is possible due to the possibility of a rank increase based on the CSI-RS based feedback. Because the front loaded CSI-RS based feedback <NUM> enables the transmission parameters to be adjusted dynamically, the throughput may be increased. For example, several data streams or transmission layers may be used because of a rank increase. The higher throughput may result in earlier termination of the data transmission. The potential for early termination may be indicated in the first control signal (e.g., control-A) in addition to an anticipated duration of transmission (e.g., a number of TTIs in the bundle).

The transmitter UE may transmit a second control signal (e.g., control-B) in the second TTI, where the receiver UE may determine a TTI bundle size from the second control signal. For example, the receiver UE may attempt to decode the second control signal in the second TTI. The receiver UE may try to decode the second control signal (e.g., control-B) to determine the new TTI bundle size. For example, the receiver UE may receive each TTI independently in response to failure of decoding of the second control signal. If the second control signal (e.g., control-B) decoding fails, the receiver UE may treat each TTI independently (TTI bundling is not assumed).

The link design including the front loaded CSI-RS based feedback may advantageously improve the reliability of the communication. For example, in the front loaded CSI-RS based feedback link design scheme, a change or an adjustment in precoding may be transparent to the receiver UE. In one aspect, the second control signal (e.g. Control B) may not be transmitted in the second TTI. For example, the second TTI may be transmitted without a control signal. For example, the second reference signal may be used as the reference and may also be precoded in the same fashion as the data in the second TTI. For example, a duration and rank of the original transmission may remain the same but with improved reliability. In one aspect, the second data transmission may comprise an adjusted precoding parameter, where the second data transmission comprises a same rank as the first data transmission in the first TTI. For example, a TTI duration of the second TTI may be unchanged from the first TTI.

<FIG> illustrates an example communication flow <NUM> between a first UE <NUM> (e.g., <NUM>, <NUM>, etc.) and a second UE <NUM> (e.g., <NUM>', <NUM>, etc.) in a front loaded feedback link design in a bundled TTI comprising a first TTI and a second TTI in a wireless communication. The communication may be based on V2X, V2V, or D2D based communication directly from the first UE <NUM> to the second UE <NUM>. The communication transmitting from UE <NUM>, <NUM> may be broadcast and received by multiple receiving devices within range of a particular transmitting device, as described in connection with <FIG>. The first UE <NUM>, which may be a vehicle or a device installed in a vehicle in a V2V/V2X network, may transmit a first data transmission <NUM> and a first reference signal <NUM> to the second UE <NUM> in a first TTI. For example, the first reference signal <NUM> may be a CSI-RS signal, as described in connection with <FIG>. The second UE <NUM> may transmit a feedback <NUM> based on the first reference signal <NUM>, as described in connection with any of <FIG>. The first UE <NUM> may adapt one or more transmission parameters for a second data transmission <NUM> in a second TTI based on the feedback <NUM> received from the second UE <NUM>, as illustrated at <NUM>. The first UE <NUM> may transmit the second data transmission <NUM> to the second UE <NUM> in the second TTI. For example, the second data transmission may have the one or more transmission parameters adapted based on the feedback received from the second UE. For example, the first UE <NUM> may transmit a second reference signal <NUM> to the second UE in the second TTI, where the second reference signal may have one or more parameters based on the feedback <NUM>. The UE may use the one or more parameters of the second reference signal to determine the adjusted transmission parameters for decoding the data. The UE <NUM> may further transmit control signaling, e.g., <NUM>, based on the adjusted transmission parameters.

<FIG> is a flowchart <NUM> of a method of wireless communication at a first UE. The method may be performed, for example, by the first UE (e.g., UE <NUM>', <NUM>, <NUM>, <NUM>, the apparatus <NUM>/<NUM>', the processing system <NUM>, which may include the memory <NUM> and which may be the entire UE <NUM> or a component of the UE <NUM>, such as the TX processor <NUM>, the RX processor <NUM>, and/or the controller/processor <NUM>) communicating with a second UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>/<NUM>', the processing system <NUM>, which may include the memory <NUM> and which may be the entire UE <NUM> or a component of the UE <NUM>, such as the TX processor <NUM>, the RX processor <NUM>, and/or the controller/processor <NUM>). The UE may communication using a bundled TTI comprising at least a first TTI and a second TTI. The wireless communication may comprise a V2V or V2X communication. To facilitate an understanding of the techniques and concepts described herein, the method of flowchart <NUM> may be discussed with reference to the examples illustrated in <FIG>, <FIG> and <FIG>. For discussion purposes, consider that the first UE may be the UE <NUM>. Optional aspects may be illustrated in dashed lines.

In the method of flow chart <NUM>, a link level scheme may be used that applies precoding based on feedback received from a receiver UE. The feedback may be based on the CSI-RS transmissions in the first TTI and may be used to determine improved transmission precoding, rank, etc. Applying channel knowledge to the MCS, modulation, code rate, rank and/or precoding determination may advantageously improve performance over a single port non-precoded transmission. In this way, the data rate, capacity, or special efficiency in communication may be improved.

At <NUM>, the first UE may receive a first data transmission. For example, referring back to <FIG> and <FIG>, a receiver UE <NUM> may receive a first data transmission <NUM> and a first reference signal <NUM> directly from a transmitter UE <NUM>, e.g., in a first TTI 501b. For example, reception component <NUM> and/or data component <NUM> of apparatus <NUM> may perform the reception of the first data transmission.

At <NUM>, the first UE may receive a first reference signal <NUM>, <NUM> directly from the second UE , e.g., in the first TTI. For example, reception component <NUM> and/or RS component <NUM> of apparatus <NUM> may perform the reception of the reference signal from UE <NUM>. For example, referring back to <FIG> and <FIG>, the receiver UE <NUM> may receive a a first reference signal <NUM> directly from a transmitter UE <NUM>, e.g., in the first TTI 501b. For example, the first reference signal <NUM> may be a CSI-RS signal, as described in connection with <FIG>. In some aspects, the first reference signal may comprise a CSI-RS. For example, CSI-RS may be transmitted together with a reference signal for decoding the data in the first TTI. For example, the first UE may receive a third reference signal (e.g., CRS, DM-RS, etc.) in the first TTI for decoding data in the first TTI, where the CSI-RS is multiplexed with the third reference signal. <FIG>, <FIG>, <FIG>, and <FIG> illustrate examples of CSI-RS transmitted together with another reference signal, such as CRS, for decoding data <NUM>. For example, the first reference signal <NUM> might not comprise precoding. For example, the first reference signal may comprise a cyclical precoding mechanism or a semi-static precoding known to the first UE. For example, the first UE may receive a third reference signal <NUM>, e.g., in the first TTI for decoding data in the first TTI, where the CSI-RS <NUM> is received in a separate symbol than the third reference signal. <FIG> illustrate examples in which the CSI-RS <NUM> is transmitted separately from another reference signal, e.g., DM-RS <NUM>. For example, the CSI-RS may be received prior to the third reference signal <NUM>, e.g., in a second symbol of the first TTI, as illustrated in <FIG>.

At <NUM>, the first UE may receive a first control signal indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping and a precoding type, where the first control signal may be received, e.g., in the first TTI. For example, reception component <NUM> and/or control component <NUM> of apparatus <NUM> may perform the reception of the control signal from UE <NUM>. For example, referring back to <FIG> and <FIG>, the first UE may receive a first control signal <NUM>, indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping and a precoding type, where the first control signal may be received, e.g., in the first TTI. <FIG> illustrate examples in which the control signaling <NUM> is transmitted in the first TTI. In some aspects, the first UE may receive the first control signal <NUM>, e.g., in the first TTI, where the first control signal may further indicate a potential for early termination of a data transmission.

At <NUM>, the first UE may transmit a feedback <NUM> to the second UE based on the first reference signal <NUM>, <NUM>. For example, transmission component <NUM> and/or feedback component <NUM> of apparatus <NUM> may perform the transmission of the feedback. For example, referring back to <FIG> and <FIG>, the receiver UE may determine precoding and/or rank and/or channel quality based on CSI-RS in <NUM>, and send the information in the feedback <NUM>, <NUM>. For example, the front loaded CSI-RS based feedback <NUM> can enable the transmitter UE to adapt precoding and/or rank within bundled TTI based on in-time precoding/rank/channel quality (PMI/RI/CQI) feedback <NUM>. The feedback <NUM> may comprise one or more of a PMI, a RI, or a CQI. As shown in <FIG>, the link level scheme may apply precoding based on the feedback <NUM> received from the receiver UE. The feedback <NUM> may be used by the transmitting UE to determine adapted transmission precoding/rank based on the CSI-RS transmissions in the first TTI 501b. As shown in <FIG>, the feedback <NUM> may be transmitted in the second TTI, e.g., in a first symbol in the second TTI 503b. For example, the feedback <NUM> may be transmitted after an acknowledgment or Negative acknowledgment (ACK/NACK) feedback <NUM> from the receiver UE.

At <NUM>, the first UE may receive a second reference signal directly from the second UE. For example, reception component <NUM> and/or RS component <NUM> of apparatus <NUM> may perform the reception of the second reference signal from UE <NUM>. For example, referring back to <FIG> and <FIG>, the first UE may receive a second reference signal <NUM>, <NUM> from the second UE, e.g., in the second TTI, where the second reference signal may have one or more parameters based on the feedback <NUM> transmitted to the second UE. For example, the feedback may comprise one or more of a PMI, a RI, or a CQI. For example, the second reference signal may comprise precoding adapted based on the feedback. For example, the feedback <NUM> may be transmitted in the first symbol in the second TTI, as illustrated in <FIG>. For example, the feedback may be transmitted after an acknowledgment or Negative acknowledgment (ACK/NACK) <NUM> from the receiver UE.

At <NUM>, the first UE may receive a second control signal. For example, reception component <NUM> and/or control component <NUM> of apparatus <NUM> may perform the reception of the second control signal from UE <NUM>. For example, referring back to <FIG> and <FIG>, the first UE may receive a second control signal <NUM>, indicating an adjustment to the one or more transmission parameters for the second data transmission based on the feedback. For example, the second control signal may be received in the second TTI. For example, the one or more transmission parameters adapted based on the feedback may comprise any combination of a PMI, a RI, a CQI, a modulation and coding scheme (MCS), a number of layers, a number of ports, and a coding rate. The second control signal <NUM> may be received after the second reference signal <NUM>, as in <FIG>, <FIG>, and <FIG>. In another example, the second control signal <NUM> may be received in a symbol prior to a second reference signal <NUM> in the second TTI, as illustrated in the example in <FIG>. For example, the second control signal <NUM> may comprise precoding, where the precoding may be determined based on the second reference signal <NUM>. For example, the second control signal <NUM> may be received without precoding. For example, the first UE may receive the second control signal <NUM>, e.g., in the second TTI, where the first UE may determine a TTI bundle size from the second control signal <NUM>.

In some aspects, the first UE may receive a control signal <NUM> in the second TTI without receiving a control signal in the first TTI, e.g., as illustrated in the example in <FIG>. For example, the second data transmission may comprise an adjusted precoding parameter, where the second data transmission may comprise a same rank as the first data transmission in the first TTI. For example, a TTI duration of the second TTI may be unchanged from the first TTI. For example, the second TTI may be received without a control signal.

At <NUM>, the first UE may receive a second data transmission. For example, reception component <NUM> and/or data component <NUM> of apparatus <NUM> may perform the reception of the second data transmission from UE <NUM>. For example, referring back to <FIG> and <FIG>, the first UE may receive a second data transmission <NUM>, <NUM> from the second UE, e.g., in the second TTI, where the second data transmission may have one or more transmission parameters adapted based on the feedback <NUM> transmitted to the second UE.

At <NUM>, the first UE may attempt to decode the second control signal <NUM> in the second TTI. For example, decoding component <NUM> of apparatus <NUM> may attempt to decode the second control signal. The first UE may receive each TTI independently in response to failure of decoding of the second control, at <NUM>. For example, the first UE may monitor for a listen before talk (LBT) sequence for each TTI.

At <NUM>, the first UE may receive a third data transmission from the second UE, e.g., in a third TTI. For example, reception component <NUM> and/or data component <NUM> of apparatus <NUM> may perform the reception of the third data transmission from UE <NUM>. For example, the bundled TTI may further comprise the third TTI, where the second TTI may be separated from the first TTI by the third TTI. In this situation, in temporal order, the first UE may receive the first data transmission in the first TTI, the third data transmission in the third TTI, and then the second data transmission in the second TTI. For example, the bundled TTI may further comprise a third TTI, and where the second UE may further adapt the one or more transmission parameters for the third TTI based on the feedback transmitted to the second UE.

In some aspects, the feedback channel on which the feedback is transmitted may be power controlled based on at least one of an RSRP, a RSSI or a channel SNR. Thus, the first UE may determine a transmission power for the feedback <NUM> based on a power control level.

In some aspects, the feedback may be based on the predicted channel in the second TTI. For example, the feedback may comprises a prediction of a channel estimate for the second TTI. Since temporal correlations of the channel are known, the PMI/CQI feedback may be based on the predicted channel in the next TTI (or next few TTIs). For example, the channel may be predicted through interpolation.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an example apparatus <NUM>. The apparatus may be a first UE (e.g., UE <NUM>', <NUM>, <NUM>, <NUM>, the apparatus <NUM>/<NUM>', etc.) communicating with a second UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>/<NUM>', etc.) in a bundled TTI comprising a first TTI and a second TTI in a wireless communication. The apparatus <NUM> may correspond to the entire UE or to a component of the UE. The wireless communication may comprise a V2V or V2X communication, as described herein.

The apparatus includes a data component <NUM> that receives a first data transmission from the second UE <NUM>, e.g., in the first TTI, and a second data transmission from the second UE <NUM>, e.g., in the second TTI, e.g., via reception component <NUM>. The apparatus includes a reference signal component <NUM> that receives a first reference signal, e.g., CSI-RS, via reception component <NUM>. The apparatus includes a feedback component <NUM> that transmits a feedback to the second UE based on the first reference signal, e.g., via transmission component <NUM>. The second data transmission may have one or more transmission parameters adapted based on the feedback transmitted to the second UE. The feedback provided by the feedback component <NUM> may be based on the first reference signal, e.g., CSI-RS.

In some aspects, the data component <NUM> may receive additional data transmissions, e.g., a third transmission.

In some aspects, the RS component <NUM> may receive a second reference signal, where the second reference signal may have one or more parameters based on the feedback transmitted to the second UE. For example, the second reference signal may comprise precoding adapted based on the feedback.

For example, the first reference signal may comprise a channel state information-reference signal (CSI-RS). In some aspects, the apparatus may receive a third reference signal in the first TTI, where the third reference signal for decoding data in the first TTI, wherein the CSI-RS is multiplexed with the third reference signal. In some aspects, the apparatus may receive a third reference signal in the first TTI, where the CSI-RS is received in a separate symbol than the third reference signal.

The apparatus may include a control component <NUM> for the received control signals. For example, the control component <NUM> may receive a first control signal indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping and a precoding type, where the first control signal is received in the first TTI, which may be used to decode data. For example, the apparatus may receive a second control signal indicating an adjustment to the one or more transmission parameters for the second data transmission based on the feedback. For example, the one or more transmission parameters adapted based on the feedback may comprise one or more of a PMI, a RI, a CQI, a MCS, a number of layers, a number of ports, and a coding rate. For example, the first control signal may further indicate a potential for early termination of a data transmission.

The apparatus may include a decoding component <NUM> for decoding the data, reference signals and the control signals. For example, the apparatus may attempt to decode the second control signal in the second TTI, where the first apparatus receives each TTI independently in response to failure of decoding of the second control. For example, the apparatus may receive a control signal in the second TTI without receiving a control signal in the first TTI. For example, the apparatus may receive a third data transmission from the second UE in a third TTI, where the bundled TTI further comprises the third TTI, and where the second TTI is separated from the first TTI by the third TTI.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of <FIG>, <FIG> and <FIG>. As such, each block in the aforementioned flowcharts of <FIG>, <FIG> and <FIG>may be performed by a component and the apparatus may include one or more of those components.

<FIG> is a diagram <NUM> illustrating an example of a hardware implementation for an apparatus <NUM>' employing a processing system <NUM>. The processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> links together various circuits including one or more processors and/or hardware components, represented by the processor <NUM>, the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the computer-readable medium/memory <NUM>. The bus <NUM> may 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.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium/memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium/memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. In one configuration, the processing system <NUM> may be a component of the UE <NUM> and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>. Alternatively, the processing system <NUM> may correspond to the entire UE.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for receiving a first data transmission from a second UE in the first TTI (e.g., at least reception component <NUM>, data component <NUM>, memory <NUM>, and/or processor <NUM>. The apparatus may include means for receiving a first reference signal from the second UE(e.g., at least reception component <NUM>, RS component <NUM>, memory <NUM>, and/or processor <NUM>). The apparatus may include means for transmitting a feedback to the second UE based on the first reference signal(e.g., at least transmission component <NUM>, feedback component <NUM>, memory <NUM>, and/or processor <NUM>). The apparatus may include means for receiving a second data transmission from the second UE in the second TTI, the second data transmission having one or more transmission parameters adapted based on the feedback transmitted to the second UE (e.g., at least reception component <NUM>, RS component <NUM>, memory <NUM>, and/or processor <NUM>). The apparatus may include means for receiving a second reference signal in the first TTI, the second reference signal for decoding data in the first TTI, wherein the CSI-RS is multiplexed with the second reference signal. The apparatus may include means for receiving a second reference signal in the first TTI, the second reference signal for decoding data in the first TTI, and wherein the CSI-RS is received in a separate symbol than the second reference signal (e.g., at least reception component <NUM>, RS component <NUM>, memory <NUM>, and/or processor <NUM>). The apparatus may include means for receiving a first control signal indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping or a precoding type, wherein the first control signal is received in the first TTI (e.g., at least reception component <NUM>, control component <NUM>, memory <NUM>, and/or processor <NUM>). The apparatus may include means for receiving a second control signal indicating an adjustment to the one or more transmission parameters for the second data transmission (e.g., at least reception component <NUM>, control component <NUM>, memory <NUM>, and/or processor <NUM>). The apparatus may include means for receiving a control signal in the second TTI, wherein the first UE determines a TTI bundle size from the control signal (e.g., at least reception component <NUM>, control component <NUM>, memory <NUM>, and/or processor <NUM>). The apparatus may comprise means for attempting to decode the first and second data transmissions. (e.g., at least decoding component <NUM>, memory <NUM>, and/or processor <NUM>).

<FIG> is a flowchart <NUM> of a method of wireless communication at a first UE. The method may be performed, for example, by the first UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>/<NUM>', the processing system <NUM>, which may include the memory <NUM> and which may be the entire UE <NUM> or a component of the UE <NUM>, such as the TX processor <NUM>, the RX processor <NUM>, and/or the controller/processor <NUM>). The UE may communicate directly with another UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) using a bundled TTI comprising at least a first TTI and a second TTI in a wireless communication. The wireless communication may comprise a V2V or V2X communication. To facilitate an understanding of the techniques and concepts described herein, the method of flowchart <NUM> may be discussed with reference to the examples illustrated in <FIG>, <FIG> and <FIG>. For discussion purposes, consider that the first UE may correspond to UE <NUM> in <FIG>. Optional aspects may be illustrated in dashed lines.

In the method of flow chart <NUM>, the first UE may apply channel knowledge based on received feedback to adjust an MCS, modulation, code rate, rank and/or precoding to improve performance beyond a single port, non-precoded transmission. In this method, a link level scheme may be used that applies precoding based on feedback received from a receiver UE. The feedback may be based on the CSI-RS transmissions in the first TTI and may be used to determine improved transmission precoding, rank, etc. Applying channel knowledge to the MCS, modulation, code rate, rank and/or precoding determination may advantageously improve performance over a single port non-precoded transmission. In this way, the data rate, capacity, or special efficiency in communication may be improved.

At <NUM>, the first UE may transmit a first data transmission. For example, transmission component <NUM> and/or data component <NUM> of apparatus <NUM> may perform the transmission of the first data transmission. For example, referring back to <FIG>and <FIG>, the transmitter UE may transmit a first data transmission <NUM> and a first reference signal <NUM> directly to a receiver UE, e.g., in the first TTI 501b.

At <NUM>, the first UE may transmit a first reference signal (e.g., <NUM>, <NUM>) to the second UE, e.g., in the first TTI. For example, transmission component <NUM> and/or RS component <NUM> of apparatus <NUM> may perform the transmission of the first RS. For example, referring back to <FIG> and <FIG>, the transmitter UE may transmit a first data transmission <NUM> and a first reference signal <NUM> directly to a receiver UE, e.g., in the first TTI 501b. For example, the first reference signal <NUM> may be a CSI-RS signal, as described in connection with <FIG>. In some aspects, the first reference signal may comprise a CSI-RS. For example, CSI-RS may be transmitted together with a reference signal for decoding the data in the first TTI. For example, the first UE may receive a third reference signal (e.g., CRS, DM-RS, etc.) in the first TTI for decoding data in the first TTI, where the CSI-RS is multiplexed with the third reference signal. <FIG>, <FIG>, <FIG>, and <FIG> illustrate examples of CSI-RS transmitted together with another reference signal, such as CRS, for decoding data <NUM>. For example, the first reference signal <NUM> might not comprise precoding. For example, the first reference signal may comprise a cyclical precoding mechanism or a semi-static precoding known to the first UE. For example, the first UE may receive a third reference signal <NUM>, e.g., in the first TTI for decoding data in the first TTI, where the CSI-RS <NUM> is received in a separate symbol than the third reference signal. <FIG> illustrate examples in which the CSI-RS <NUM> is transmitted separately from another reference signal, e.g., DM-RS <NUM>. For example, the CSI-RS may be received prior to the third reference signal <NUM>, e.g., in a second symbol of the first TTI, as illustrated in <FIG>.

At <NUM>, the first UE may transmit a first control signal (e.g., <NUM>) indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping and a precoding type, where the first control signal may be transmitted in the first TTI. For example, transmission component <NUM> and/or control component <NUM> of apparatus <NUM> may perform the transmission of the first control signal. For example, referring back to <FIG> and <FIG>, the first UE may receive a first control signal <NUM>, indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping and a precoding type, where the first control signal may be received, e.g., in the first TTI. <FIG> illustrate examples in which the control signaling <NUM> is transmitted in the first TTI. In some aspects, the first UE may receive the first control signal <NUM>, e.g., in the first TTI, where the first control signal may further indicate a potential for early termination of a data transmission.

At <NUM>, the first UE may receive a feedback (e.g., <NUM>) to the second UE based on the first reference signal <NUM>, <NUM>. For example, reception component <NUM> and/or feedback component <NUM> of apparatus <NUM> may perform reception of the feedback. For example, referring back to <FIG> and <FIG>, the receiver UE may determine precoding and/or rank and/or channel quality based on CSI-RS in <NUM>, and send the information in the feedback <NUM>. For example, the front loaded CSI-RS based feedback <NUM> can enable the transmitter UE to adapt precoding and/or rank within bundled TTI based on in-time precoding/rank/channel quality (PMI/RI/CQI) feedback <NUM>. The feedback <NUM> may comprise one or more of a PMI, a RI, or a CQI. As shown in <FIG>, the link level scheme may apply precoding based on the feedback <NUM> received from the receiver UE. The feedback <NUM> may be used by the transmitting UE to determine adapted transmission precoding/rank based on the CSI-RS transmissions in the first TTI 501b. As shown in <FIG>, the feedback <NUM> may be transmitted in the second TTI, e.g., in a first symbol in the second TTI 503b. For example, the feedback <NUM> may be transmitted after an acknowledgment or Negative acknowledgment (ACK/NACK) feedback <NUM> from the receiver UE.

At <NUM>, in some aspects, the first UE may determine whether to use the feedback to adapt the one or more transmission parameters for the second TTI based on an amount of data to be sent to the second UE. For example, determination component <NUM> of apparatus <NUM> may perform the determination. For example, referring back to <FIG> and <FIG>, the front loaded feedback may increase overhead. CLSM may be applied when large amounts of data spanning multiple TTIs are to be communicated. For example, the front loaded feedback may be used to adapt the one or more transmission parameters for the second TTI when the number of TTI is larger than a threshold number.

At <NUM>, the first UE may adapt one or more transmission parameters for a second data transmission. For example, adapting component <NUM> may perform the adaptation of the transmission parameters. For example, referring back to <FIG> and <FIG>, the first UE may adapt one or more transmission parameters for a second data transmission <NUM> , e.g., in the second TTI based on the feedback <NUM> received from the second UE. For example, the front loaded CSI-RS based feedback <NUM> can enable the transmitter UE to adapt precoding and/or rank within bundled TTI based on in-time precoding/rank/channel quality (PMI/RI/CQI) feedback <NUM>. The feedback <NUM> may comprise one or more of a PMI, a RI, or a CQI. As shown in <FIG>, the link level scheme may apply precoding based on the feedback <NUM> received from the receiver UE. The feedback <NUM> may be used by the transmitting UE to determine adapted transmission precoding/rank based on the CSI-RS transmissions in the first TTI 501b.

At <NUM>, the first UE may transmit a second reference signal to the second UE in the second TTI. For example, transmission component <NUM> and/or RS component <NUM> of apparatus <NUM> may perform the transmission of the second reference signal. For example, referring back to <FIG> and <FIG>, the first UE may transmit a second reference signal <NUM> to the second UE, e.g., in the second TTI, where the second reference signal may have one or more parameters based on the feedback <NUM> transmitted to the second UE. For example, the feedback <NUM> may comprise one or more of a PMI, a RI, or a CQI. For example, the second reference signal may comprise precoding adapted based on the feedback. For example, the feedback may be transmitted in the first symbol in the second TTI, as illustrated in <FIG>. For example, the feedback may be transmitted after an acknowledgment or Negative acknowledgment (ACK/NACK) <NUM> from the receiver UE.

At <NUM>, the first UE may transmit a second control signal, e.g., <NUM>, indicating an adjustment to the one or more transmission parameters for the second data transmission based on the feedback. For example, transmission component <NUM> and/or control component <NUM> of apparatus <NUM> may perform the transmission of the second control signal. For example, referring back to <FIG> and <FIG>, the second control signal may be transmitted in the second TTI. For example, the one or more transmission parameters adapted based on the feedback may comprise any combination of a PMI, a RI, a MCS, a CQI, a number of layers, a number of ports, and a coding rate. The second control signal <NUM> may be transmitted after the second reference signal <NUM>, as in <FIG>, <FIG>, and <FIG>. For another example, the second control signal <NUM> may be transmitted in a symbol prior to a second reference signal <NUM> in the second TTI, as illustrated in the example in <FIG>. For example, the second control signal <NUM> may comprise precoding, where the precoding may be determined based on the second reference signal <NUM>. For example, the second control signal may be transmitted without precoding. For example, the first UE may transmit the second control signal <NUM> in the second TTI, where the second UE may determine a TTI bundle size from the second control signal <NUM>. For example, the second UE may receive each TTI independently in response to failure of decoding of the second control signal. For example, the second UE may monitor for a listen before talk (LBT) sequence for each TTI.

In some aspects, the first UE may transmit a control signal <NUM> in the second TTI without transmitting a control signal in the first TTI. For example, the second data transmission may comprise an adjusted precoding parameter, where the second data transmission may comprise a same rank as the first data transmission in the first TTI. For example, a TTI duration of the second TTI is unchanged from the first TTI. For example, the second TTI is transmitted without a control signal.

At <NUM>, the first UE may transmit the second data transmission to the second UE in the second TTI. For example, transmission component <NUM> and/or data component <NUM> of apparatus <NUM> may perform the transmission of the second data transmission. For example, referring back to <FIG> and <FIG>, the first UE may transmit the second data transmission <NUM> to the second UE, e.g., in the second TTI, where the second data transmission <NUM> may have the one or more transmission parameters adapted based on the feedback <NUM> received from the second UE.

At <NUM>, the first UE may adapt the one or more transmission parameters for the third TTI. For example, the bundled TTI may further comprise a third TTI, where the first UE may further adapt the one or more transmission parameters for the third TTI based on the feedback received from the second UE.

At <NUM>, the first UE may transmit a third data transmission to the second UE in a third TTI. For example, transmission component <NUM> and/or data component <NUM> of apparatus <NUM> may perform the transmission of the third data transmission. For example, the bundled TTI may further comprise the third TTI, where the second TTI may be separated from the first TTI by the third TTI. In this situation, in temporal order, the first UE may transmit the first data transmission in the first TTI, the third data transmission in the third TTI, and then the second data transmission in the second TTI.

In some aspects, the feedback channel on which the feedback is received is power controlled based on at least one of a RSRP, a RSSI or a channel SNR.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an example apparatus <NUM>. The apparatus may be a first UE or a component of a first UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>/<NUM>', etc.) communicating with a second UE (e.g., UE <NUM>', <NUM>, <NUM>, <NUM>, the apparatus <NUM>/<NUM>', etc.) in a bundled TTI comprising a first TTI and a second TTI in a wireless communication. The wireless communication may comprise a V2V or V2X communication, as described herein.

The apparatus includes a data component <NUM> that transmits, via the transmission component <NUM>, a first data transmission to the second UE <NUM>, e.g., in the first TTI. The apparatus includes an RS component that transmits, via transmission component <NUM>, a first reference signal to the second UE <NUM> in the first TTI. The data component <NUM> further transmits, via the transmission component <NUM>, a second data transmission to the second UE <NUM>, e.g., in the second TTI. The apparatus includes a reception component <NUM> that receives communication from the second UE <NUM>. The apparatus includes a feedback component <NUM> that receives, via the reception component <NUM>, a feedback from the second UE <NUM> based on the first reference signal. The second data transmission may have one or more transmission parameters adapted based on the feedback received from the second UE <NUM>. Thus, the apparatus may include an adapting component <NUM> for adapting one or more transmission parameters for the second data transmission in the second TTI based on the feedback received from the second UE <NUM>. The adapted parameters may be provided from the adaptating component <NUM> to the data component <NUM>, RS component <NUM>, and control component <NUM>.

The data component <NUM> may transmit additional TTIs to the second UE, e.g., in a third transmission.

In some aspects, the RS component <NUM> may transmit a second reference signal, where the second reference signal may have one or more parameters based on the feedback transmitted to the second UE. For example, the second reference signal may comprise precoding adapted based on the feedback.

For example, the first reference signal generated by the RS component <NUM> may comprise a CSI-RS. In some aspects, the RS component <NUM> may transmit a third reference signal in the first TTI, where the third reference signal for decoding data in the first TTI, where the CSI-RS is multiplexed with the third reference signal. In some aspects, the apparatus may transmit a third reference signal in the first TTI, where the CSI-RS is transmitted in a separate symbol than the third reference signal.

The apparatus may include a control component <NUM> for transmitting control signals to the second UE <NUM>. For example, the apparatus may transmit a first control signal indicating at least one of a target UE identification, a reference signal pattern, a transparent mode (TM), a rank indicator, a layer mapping and a precoding type, where the first control signal is transmitted in the first TTI. For example, the apparatus may transmit a second control signal indicating an adjustment to the one or more transmission parameters for the second data transmission based on the feedback. For example, the one or more transmission parameters adapted based on the feedback may comprise one or more of a precoding matrix indicator (PMI), a rank indicator (RI), a modulation and coding scheme (MCS), a channel quality indicator (CQI), a number of layers, a number of ports, and a coding rate.

For example, the first control signal may further indicate a potential for early termination of a data transmission. For example, the second UE <NUM> may attempt to decode the second control signal in the second TTI, where the second UE <NUM> may receive each TTI independently in response to failure of decoding of the second control. For example, the apparatus may transmit a control signal in the second TTI without transmitting a control signal in the first TTI. For example, the apparatus may transmit a third data transmission to the second UE <NUM> in a third TTI, where the bundled TTI may further comprise the third TTI, and where the second TTI is separated from the first TTI by the third TTI. For example, the apparatus may transmit a third data transmission to the second UE <NUM> in a third TTI, where the bundled TTI further may comprise the third TTI, and wherein the apparatus may further adapt the one or more transmission parameters for the third TTI based on the feedback received from the second UE.

The apparatus may include a determination component <NUM> for determining whether to use the feedback to adapt the one or more transmission parameters for the second TTI based on an amount of data to be sent to the second UE. For example, the front loaded feedback may increase overhead. CLSM may be applied when large amounts of data spanning multiple TTIs are to be communicated. For example, the front loaded feedback may be used to adapt the one or more transmission parameters for the second TTI when the number of TTI is larger than a threshold number.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of <FIG>, <FIG>, <FIG> and <FIG>. As such, each block in the aforementioned flowcharts of <FIG>, <FIG>, <FIG> and <FIG>may be performed by a component and the apparatus may include one or more of those components.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for transmitting a first data transmission to a second UE in the first TTI (e.g., at least transmission component <NUM>, data component <NUM>, memory <NUM> and/or processor <NUM>). The apparatus may include means for transmitting a first reference signal to the second UE(e.g., at least transmission component <NUM>, RS component <NUM>, memory <NUM> and/or processor <NUM>). The apparatus may include means for receiving a feedback from the second UE based on the first reference signal(e.g., at least reception component <NUM>, feedback component <NUM>, memory <NUM> and/or processor <NUM>). The apparatus may include means for adapting one or more transmission parameters for a second data transmission in the second TTI based on the feedback received from the second UE (e.g., at least transmission component <NUM>, adapting component <NUM>, memory <NUM> and/or processor <NUM>). The apparatus may include means for transmitting a second data transmission from the second UE in the second TTI, the second data transmission having one or more transmission parameters adapted based on the feedback transmitted to the second UE (e.g., at least transmission component <NUM>, data component <NUM>, memory <NUM> and/or processor <NUM>). The apparatus may include means for transmitting a control signal (e.g., at least transmission component <NUM>, control component <NUM>, memory <NUM> and/or processor <NUM>).

Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes/flowcharts may be rearranged. The scope of protection is limited only by the appended claims.

Claim 1:
A method of wireless communication at a first user equipment, UE, in a bundled Transmission Time Interval, TTI, comprising at least a first TTI and a second TTI, the method comprising:
receiving, at the first UE, a first data transmission (<NUM>) directly from a second UE in the first TTI;
receiving, at the first UE, a first reference signal (<NUM>) directly from the second UE, wherein the first reference signal comprises a channel state information-reference signal, CSI-RS;
receiving a second reference signal in the first TTI, the second reference signal for decoding data in the first TTI, wherein the CSI-RS is received in a separate symbol than the second reference signal;
transmitting a feedback to the second UE based on the first reference signal (<NUM>); and
receiving a second data transmission (<NUM>) from the second UE in the second TTI or a subsequent TTI, the second data transmission having one or more transmission parameters adapted based on the feedback transmitted to the second UE and an amount of data in the second data transmission.