Patent Description:
The present disclosure relates generally to Device-to-Device (D2D) communication, and more particularly to Sidelink (SL) channels in telecommunications systems.

<FIG> is a schematic diagram of a communications environment illustrating V2X scenarios facilitated by cellular Uplink (UL), Downlink (DL), and SL. During Release <NUM> and Release <NUM>, the 3GPP Long Term Evolution (LTE) standard has been extended with support of D2D communications (also referred to as SL or the "PC5 interface") targeting vehicular communications, collectively referred to as V2X communications. Besides Vehicle-to-Vehicle (V2V) communication, V2X includes Vehicle-to-Pedestrian or Pedestrian-to-Vehicle (collectively, V2P), Vehicle-to-Infrastructure (V2I), and Vehicle-to-Network (V2N).

The Fifth Generation (<NUM>) V2X standardization in Release <NUM> aims to enhance the 3GPP NR system to meet stringent Quality of Service (QoS) requirements (e.g., in terms of latency and reliability) of advanced V2X services that are beyond the capabilities of the V2X safety services supported by LTE V2X Rel-<NUM> and Rel-<NUM>. Therefore, the NR SL design includes new features, including physical layer unicast, power control, Hybrid Automatic Repeat Request (HARQ) and QoS management. A key technical feature of the NR SL for V2X is the capability to support physical-layer unicast and groupcast (also called as multicast) as compared with the broadcast-only LTE SL.

There are two operation modes for the NR SL:.

In cellular networks, including 3GPP NR networks, transmit power control is exercised for UL transmissions. The 3GPP specifications enable a UE to set the transmit power by taking into account the Path Loss (PL), number of scheduled resource blocks, targeted Signal-to-Noise Ratio (SNR) at the Base Station (BS) and some other parameters. Specifically, UL power control is set by the UE according to a set of equations that contains a number of parameters related to large scale fading (estimated PL), number of scheduled resource blocks, target SNR, and some other parameters. This rather general formula is often referred to as the Fractional PL (FRPL) compensation formula, which can be configured separately for the Physical UL Shared Channel (PUSCH) and Physical UL Control Channel (PUCCH).

For controlling the power in network-controlled D2D communications over the SL, a similar PL compensating formula can be used (see below), as it has been proposed and analyzed in some related works. When the FRPL-based power control is employed for SL transmissions, the power control scheme can optionally take into account the PL to the serving BS and the caused interference to the surrounding cellular network and nodes and UEs, in addition to the PL between the communication devices.

The FRPL equation is shown below: <MAT> where PTx is the UE transmit power, P<NUM> is a base power level used to control the SNR target, G is the estimated path gain between the UE and the BS, α is a parameter that controls the level of PL compensation, ΔTF + f(ΔTPC) is a dynamic offset depending on the Transport Format (TF, also referred to as the Modulation and Coding Scheme (MCS)) and Transmit Power Commands (TPCs) sent by the network, and M is the number of scheduled resource blocks. Specific applications to this formula can be used to achieve fixed power, fixed Signal-to-Interference-Plus-Noise Ratio (SINR) or SNR target, open loop with full or fractional path-loss compensation and closed loop power control schemes.

Power Control for NR UL: As with LTE, in NR the transmit power in the UL (from the UE to the network) is often controlled by the NR BS (gNB) (see the FRPL equation above, in which parameters can be set and the TPC command can control the transmit power). This serves two main purposes:.

LTE and NR UL power control are based on a combination of:.

In a simplified term, the baseline power control algorithm in the UL can be expressed as: <MAT> where the P denotes the transmit power, Pcmax denotes the configured maximum UE transmit power per carrier/serving cell. <MAT> is a collective term taking into account the impacts of UL PL PLUL, the desired received power P<NUM> (configurable by the network), and several other factors such as the MCS and a power-control command in the case of closed-loop power control.

Power Control for NR SL: Transmit power control for SL serves the following purposes:.

To achieve the above two goals and given what is done for the UL power control, it is natural to base the SL power control procedure on the PL estimated between the Transmitter (Tx) UE and gNB (if the Tx UE is in coverage) and also on the PL between the Tx UE and the Receiver (Rx) UE. Hence, the SL transmit power can be represented by the following generic formula: <MAT> where Pcmax is the maximum allowed transmit power configured by the UE for a carrier/serving cell. <MAT> is the maximum allowed transmit power when considering the interference to UL reception, where PLUL is the PL between the Tx UE and the gNB. This term is introduced to mitigate the interference to UL reception at the gNB. Preq(PLSL) is the required transmit power calculated based on the SL PL PLSL between the Tx UE and the Rx UE in order to guarantee reliable reception(s).

The formula in Equation <NUM> reflects the current agreements in 3GPP RAN1 on open-loop transmit power control when both DL PL and SL PL are considered. RAN1 has also agreed not to support closed-loop power control in Rel-<NUM> NR SL. Compared to the UL power control in Equation <NUM>, the SL power control in Equation <NUM> decouples the required (or desired) transmit power from <MAT> because the desired receiver is another UE. Also note that in LTE SL, due to broadcast transmissions, only Pcmax and <MAT> are considered since the set of target Rx UEs is too large for each individual SL Preq to be relevant. However, for NR SL unicast and groupcast, different parameters can be used to determine Preq, enabling the Tx UE to adjust its transmit power accordingly.

The PL PLSL is determined by the Tx UE based on Reference Signal (RS) Received Power (RSRP) measurements (that is: the Rx UE measuring RSRP) that are reported back by the Rx UE to the Tx UE. Typically, larger distances between the Tx UE and the Rx UE means higher PL and hence increasing the transmit power to cover the distance. As can be noted in Equation <NUM>, the SL transmit power Preq is limited by the Pcmax and <MAT> terms, which will be referred together as Pcmax in the rest of the disclosure.

HARQ Feedback for NR SL and the Physical SL Feedback Channel (PSFCH): Reliable unicast and groupcast communication requires transmission of HARQ acknowledgement (Positive Acknowledgement (ACK) or Negative Acknowledgement (NACK), also called HARQ feedback) from the Rx UE(s) to the Tx UE to signal successful (or unsuccessful) decoding of a previous data transmission. In order to support reliable unicast and groupcast V2X communication in NR, 3GPP has agreed to support a new physical channel to carry the HARQ feedback in the SL. The new channel, called the PSFCH, is mapped to the last symbols available for SL in a slot as represented in <FIG>.

<FIG> is a schematic diagram of the PSFCH, the Physical SL Shared Channel (PSSCH), and the Physical SL Control Channel (PSCCH) in the time-frequency domain. The PSFCH is in the form of a sequence (i.e., sequence-based PSFCH). Typically, the PSFCH sequence is a low Peak-to-Average Power (PAPR) sequence with good auto-correlation and cross-correlation properties. The ACK or NACK bits being sent are used to determine the corresponding PSFCH sequence. Also note that since PSFCH is a sequence, there is no RS (also known as pilot signal) embedded in the PSFCH, which is in contrast to other physical SL channels like the PSCCH (carrying control information) and the PSSCH (carrying data).

There currently exist certain challenge(s). The existing power control mechanisms for cellular UL and SL are designed to set the transmit power level at the Tx UE, including the transmit power level for the SL Physical Layer (PHY) channels PSSCH and PSCCH. However, these mechanisms are not directly applicable to determine the transmit power level for the SL PHY channel PSFCH transmitted by the Rx UE. Although this basic problem arises in both UE-UE unicast and multicast communications, the present disclosure focuses on unicast UE-UE communications.

Therefore, the existing power control solutions for PSSCH and PSCCH do not address the following problems:
<FIG> is a schematic diagram of SL communications between a Tx UE and an Rx UE using PSSCH for data transmission and PSFCH for HARQ feedback. A unidirectional case is illustrated, and in bidirectional cases both UEs act as both a Tx UE and an Rx UE. In either case, an RS is transmitted by the gNB to each UE. The Tx UE transmits a SL Channel State Information RS (SCSI-RS) to the Rx UE.

Problem <NUM>: In the UE-UE communication scenario illustrated in <FIG>, in which the UEs communicate over the SL (e.g., PC5 interface) and engage in bidirectional communications, there may be a large imbalance between the transmit power levels used for the PSSCH and PSFCH channels. This may result in large bit error rate and packet loss over the PSFCH (e.g., where the PSFCH power is too low) or high interference caused to the serving gNB (e.g., where the PSFCH power is too high). Note that the current 3GPP specifications do not support that the Rx UE sets the PSFCH transmit power level based on SL PL estimate.

<FIG> is a schematic diagram of SL communications between a Tx UE and an Rx UE with multiple parallel SL connections. A bidirectional case is illustrated, in which an RS is transmitted by the gNB to each UE (e.g., UE-A and UE-B) and each UE transmits a SCSI-RS to the other UE.

Problem <NUM>: In the UE-UE communication scenario illustrated in <FIG>, in which the UEs establish and maintain multiple parallel (e.g., unicast) connections, there is a large overhead in terms of SCSI-RS transmissions and measurement reports. In bidirectional SL scenarios, this large overhead is especially problematic, because it affects both UEs as both transmitters and receivers.

A 3GPP submission from Intel Corporation (R1-<NUM>) discloses "the sidelink transmit power control settings should be dependent on pathgain between eRelay and eRemote UEs, similar to UL open loop power control, but should not exceed UL transmission power settings by certain offset to avoid excessive interference for cellular UL reception. The both eRelay and eRemote UEs may request sidelink transmit power adjustments. The both eRelay and eRemote UEs may additionally take into account interference over thermal noise ratio to adjust sidelink transmit power and improve sidelink spectrum efficiency or reliability. More details on power control enhancements are provided in our companion contribution [<NUM>]. Proposal <NUM>: In case of bidirectional sidelink relaying, two independent sidelink power control loops are supported: one by eRemote UE and one by eRelay".

A 3GPP submission from LG Electronics (R1-<NUM>) discloses "for PSFCH power control, it is supported that the open-loop power control is based on the pathloss between PSFCH TX UE and gNB (if PSFCH TX UE is in-coverage".

Power control for a bidirectional Sidelink (SL) is provided. Solutions proposed herein limit the Physical SL Feedback Channel (PSFCH) transmit power level to that of the power level used for Physical SL Shared Channel (PSSCH) so as to prohibit too high transmit power for the PSFCH. In addition, if the difference between the PSSCH and PSFCH exceeds a preconfigured threshold (e.g., the PSFCH is too low), the Receiver (Rx) User Equipment (UE) can take preventive actions that ensure sufficient quality over the PSFCH. In further embodiments, both UEs continuously maintain the estimated SL Path Loss (PL) and transmit a single SL Channel State Information Reference Signal (SCSI-RS), and associated measurement reports rather than triggering new SCSI-RS transmissions and measurement reports for each PSSCH and associated PSFCH channel per SL (e.g., PC5) connection.

There are, proposed herein, various embodiments which address one or more of the issues disclosed herein. Aspects of the invention are set out in the independent claims appended hereto.

Some examples of a radio access node include, but are not limited to, a Base Station (BS) (e.g., a New Radio (NR) BS (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (<NUM>) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro BS, a low-power BS (e.g., a micro BS, a pico BS, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a BS (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node.

Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing a Access and Mobility Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

Transmitter (Tx) UE: As used herein, a UE that sends a data packet is referred to as the Tx UE.

Receiver (Rx) UE: As used herein, a UE that receives the data packet from the Tx UE is referred to as the Rx UE. There is a single Rx UE for a unicast transmission and there are multiple Rx UEs for a groupcast transmission. The Rx UE(s) send a Hybrid Automatic Repeat Request (HARQ) acknowledgment (Positive Acknowledgement (ACK) or Negative Acknowledgement (NACK), also known as HARQ feedback) to the Tx UE upon successful or unsuccessful decoding of the packet. The HARQ acknowledgment for Sidelink (SL) communications is sent in a Physical SL Feedback Channel (PSFCH).

Power control for a bidirectional SL is provided. Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. The solution to Problem <NUM> described above builds on recognizing that the Rx UE illustrated in <FIG> under a traditional approach sets the PSFCH power without taking into account the Path Loss (PL) between the Rx UE and Tx UE. This is because under the traditional approach, the PSFCH power is determined based on the estimated PL between the Rx UE and the gNB. The proposed solution utilizes the fact that the SL communication is typically bidirectional between the UEs, and the Rx UE acts as a Tx UE in parallel with its Rx role. Based on this, the Rx UE limits the PSFCH transmit power level to that of the power level used for Physical SL Shared Channel (PSSCH) so as to prohibit too high transmit power for the PSFCH. In addition, if the difference between the PSSCH and PSFCH exceeds a preconfigured threshold (e.g., the PSFCH is too low), the Rx UE takes preventive actions that ensure sufficient quality over the PSFCH.

The solution to Problem <NUM> described above builds on recognizing that a single SL Channel State Information Reference Signal (SCSI-RS) and associated measurements, measurement reports and PL estimation can be reused for the multiple PSSCH and PSFCH channels illustrated in <FIG>. The solution elements developed for addressing Problem <NUM> are combined with both UEs continuously maintaining the estimated SL PL and transmitting a single SCSI-RS and associated measurement reports rather than triggering new SCSI-RS transmissions and measurement reports for each PSSCH and associated PSFCH channel per SL (e.g., PC5) connection.

Certain embodiments may provide one or more of the following technical advantage(s). An advantage of the solution to Problem <NUM> is that it ensures that the PSFCH does not cause high interference at the BS while setting a sufficiently high PSFCH transmit power for enabling the peer UE to decode the ACK/NACK signaling over the PSFCH with low bit error rate. Another advantage of the solution to Problem <NUM> is that it reduces the need for signaling exchange associated with SCSI-RS and measurement reporting over the SL.

In this regard, <FIG> illustrates one example of a cellular communications system <NUM> in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system <NUM> is a <NUM> system (5GS) including a NR RAN or LTE RAN (i.e., Evolved Universal Terrestrial RAN (E-UTRAN)) or an Evolved Packet System (EPS) including a LTE RAN. In this example, the RAN includes BSs <NUM>-<NUM> and <NUM>-<NUM>, which in LTE are referred to as eNBs (when connected to an Evolved Packet Core (EPC)) and in <NUM> NR are referred to as gNBs (e.g., LTE RAN nodes connected to <NUM> Core (5GC), which are referred to as gn-eNBs), controlling corresponding (macro) cells <NUM>-<NUM> and <NUM>-<NUM>. The BSs <NUM>-<NUM> and <NUM>-<NUM> are generally referred to herein collectively as BSs <NUM> and individually as BS <NUM>. Likewise, the (macro) cells <NUM>-<NUM> and <NUM>-<NUM> are generally referred to herein collectively as (macro) cells <NUM> and individually as (macro) cell <NUM>. The RAN may also include a number of low power nodes <NUM>-<NUM> through <NUM>-<NUM> controlling corresponding small cells <NUM>-<NUM> through <NUM>-<NUM>. The low power nodes <NUM>-<NUM> through <NUM>-<NUM> can be small BSs (such as pico or femto BSs) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells <NUM>-<NUM> through <NUM>-<NUM> may alternatively be provided by the BSs <NUM>. The low power nodes <NUM>-<NUM> through <NUM>-<NUM> are generally referred to herein collectively as low power nodes <NUM> and individually as low power node <NUM>. Likewise, the small cells <NUM>-<NUM> through <NUM>-<NUM> are generally referred to herein collectively as small cells <NUM> and individually as small cell <NUM>. The cellular communications system <NUM> also includes a core network <NUM>, which in the 5GS is referred to as the 5GC. The BSs <NUM> (and optionally the low power nodes <NUM>) are connected to the core network <NUM>.

The BSs <NUM> and the low power nodes <NUM> provide service to wireless communication devices <NUM>-<NUM> through <NUM>-<NUM> in the corresponding cells <NUM> and <NUM>.

<FIG> is a flowchart illustrating a process for controlling power in bidirectional SL communications. The process can address Problem <NUM> described above. Accordingly, the process is described with reference to <FIG> and <FIG>. In this regard, the process includes one or more of the following steps:
The process may optionally begin at step <NUM>, with receiving, from a BS, a power threshold. In some examples, the gNB sets up (e.g., defines or pre-defines) one or more power thresholds for an individual UE (e.g., each of the Tx UE and the Rx UE). Such thresholds specify what level of received interference power is acceptable for the gNB and the maximum difference between the PSSCH and PSFCH transmit power levels.

The process continues at step <NUM>, with determining (e.g., by the Rx UE) a PL-based transmit power for the PSFCH, denoted by PSFCHO. The Rx UE can perform measurements on the Reference Signals (RSs) continuously transmitted by the BS (e.g., gNB) and estimate the PL to the serving BS. The Rx UE then derives the PL-based PSFCH transmit power PSFCHO such that the caused interference at the BS remains under a predefined threshold (configured by the BS in Step <NUM>): <MAT> where Equation <NUM> constrains the PSFCH transmit power to a PSFCHO value which satisfies the above equation (which may be expressed in decibel-milliwatts (dBm)).

The process continues at step <NUM>, with setting (e.g., by the Rx UE) an initial PSFCH transmit power PSFCH1 based on PSFCHO and limited by a PSSCH transmit power level. The current 3GPP Rel-<NUM> specifications do not support SL PL-based power control for the PSFCH, therefore a solution that is applicable in NR Rel-<NUM> networks must not use SL PL for PSFCH. According to exemplary embodiments herein, the Rx UE utilizes the fact that it also acts as a Tx UE and thus sets the PSSCH transmit power using existing schemes. Specifically, at step <NUM> an initial value for the PSFCH transmit power PSFCH1 is set as: <MAT>.

The initial PSFCH transmit power PSFCH1 is upper bounded by the PSSCH transmit power as well as by the PL-based PSFCH transmit power PSFCHO and thereby it is not unnecessarily high and does not cause high interference at the BS. However, it may be too low with respect to the PSSCH transmit power and the SL distance over which the SL communications take place. Therefore, the Rx UE calculates the absolute value of a difference between the PSSCH transmit power and the initial PSFCH transmit power PSFCH <NUM>: <MAT> and continuously compares this value with a preconfigured threshold TH (from step <NUM>).

If the above absolute value exceeds the preconfigured threshold TH, the Rx UE takes the following actions (in any combination):.

<FIG> is a flowchart illustrating another process for controlling power in bidirectional SL communications. The process can address Problem <NUM> described above. Accordingly, the process is described with reference to <FIG> and <FIG>. This process builds on the key observation that the PSFCH power control and associated parameter configuration can be reused across multiple PC5 connections. Thus, the steps of the process illustrated in <FIG> can be combined with one or more of the steps of the process illustrated in <FIG> in order to solve Problem <NUM>.

The process begins at step <NUM>, with a UE storing configuration parameters which are used to configure one or more existing PC5 connections (e.g., an SL) with another UE (e.g., wireless device). The UE can be a Tx UE configuring the PSSCH and/or an Rx UE configuring the PSFCH, and the stored configuration parameters can be α and P<NUM>. In some examples, the UE can also store PSSCH and PSFCH transmit power levels for the existing PC5 connection. The UE can also store Quality of Service (QoS) parameters (e.g., packet loss rate, maximum bit rate, minimum bit rate, QoS Class Identifier (QCI)) associated with the PC5 connection.

The process continues at step <NUM>, with the UE setting up a new PC5 connection by configuring transmit power setting parameters for the new PC5 connection based on the stored configuration parameters. Step <NUM> may optionally include sub-step <NUM>, with the Rx UE configuring the transmit power setting parameters equal to the stored configuration parameters of the existing PC5 connection when setting up a new PC5 connection having QoS parameters similar to those of any of the one or more existing PC5 connections. Step <NUM> may optionally include sub-step <NUM>, with the Tx UE using a higher or lower transmit power setting (e.g., PSSCH transmit power) than that used for the existing PC5 connection when setting up a new PC5 connection with QoS parameters that are different from any of the one or more existing PC5 connections.

<FIG> is a schematic block diagram of a radio access node <NUM> according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The radio access node <NUM> may be, for example, a BS <NUM> or <NUM> or a network node that implements all or part of the functionality of the BS <NUM> or gNB described herein. As illustrated, the radio access node <NUM> includes a control system <NUM> that includes one or more processors <NUM> (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory <NUM>, and a network interface <NUM>. The one or more processors <NUM> are also referred to herein as processing circuitry. In addition, the radio access node <NUM> may include one or more radio units <NUM> that each includes one or more transmitters <NUM> and one or more receivers <NUM> coupled to one or more antennas <NUM>. The radio units <NUM> may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) <NUM> is external to the control system <NUM> and connected to the control system <NUM> via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) <NUM> and potentially the antenna(s) <NUM> are integrated together with the control system <NUM>. The one or more processors <NUM> operate to provide one or more functions of a radio access node <NUM> as described herein. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory <NUM> and executed by the one or more processors <NUM>.

As used herein, a "virtualized" radio access node is an implementation of the radio access node <NUM> in which at least a portion of the functionality of the radio access node <NUM> is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the radio access node <NUM> may include the control system <NUM> and/or the one or more radio units <NUM>, as described above. The control system <NUM> may be connected to the radio unit(s) <NUM> via, for example, an optical cable or the like. The radio access node <NUM> includes one or more processing nodes <NUM> coupled to or included as part of a network(s) <NUM>. If present, the control system <NUM> or the radio unit(s) <NUM> are connected to the processing node(s) <NUM> via the network <NUM>. Each processing node <NUM> includes one or more processors <NUM> (e.g., CPUs, ASICs, FPGAs, and/or the like), memory <NUM>, and a network interface <NUM>.

In this example, functions <NUM> of the radio access node <NUM> described herein are implemented at the one or more processing nodes <NUM> or distributed across the one or more processing nodes <NUM> and the control system <NUM> and/or the radio unit(s) <NUM> in any desired manner. In some particular embodiments, some or all of the functions <NUM> of the radio access node <NUM> described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) <NUM>. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) <NUM> and the control system <NUM> is used in order to carry out at least some of the desired functions <NUM>. Notably, in some embodiments, the control system <NUM> may not be included, in which case the radio unit(s) <NUM> communicate directly with the processing node(s) <NUM> via an appropriate network interface(s).

<FIG> is a schematic block diagram of a wireless communication device <NUM> according to some embodiments of the present disclosure. As illustrated, the wireless communication device <NUM> includes one or more processors <NUM> (e.g., CPUs, ASICs, FPGAs, and/or the like), memory <NUM>, and one or more transceivers <NUM> each including one or more transmitters <NUM> and one or more receivers <NUM> coupled to one or more antennas <NUM>. The transceiver(s) <NUM> includes radio-front end circuitry connected to the antenna(s) <NUM> that is configured to condition signals communicated between the antenna(s) <NUM> and the processor(s) <NUM>, as will be appreciated by one of ordinary skill in the art. The processors <NUM> are also referred to herein as processing circuitry. The transceivers <NUM> are also referred to herein as radio circuitry. In some embodiments, the functionality of the wireless communication device <NUM> described above may be fully or partially implemented in software that is, e.g., stored in the memory <NUM> and executed by the processor(s) <NUM>. Note that the wireless communication device <NUM> may include additional components not illustrated in <FIG> such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the wireless communication device <NUM> and/or allowing output of information from the wireless communication device <NUM>), a power supply (e.g., a battery and associated power circuitry), etc..

αP<NUM>At least some of the following abbreviations may be used in this disclosure.

Claim 1:
A method performed by a wireless communication device (<NUM>) for controlling power in bidirectional Sidelink, SL, communications, the method comprising:
- determining (<NUM>) a Path Loss, PL, based transmit power for a Physical SL Feedback Channel, PSFCH based on an estimated PL to a Base Station, BS (<NUM>); and
- setting (<NUM>) an initial PSFCH transmit power as a lesser of the PL-based transmit power for the PSFCH and a Physical SL Shared Channel, PSSCH, transmit power level.