Path switching in user equipment to user equipment relay

Abstract

A method may include monitoring, by a source user equipment communicating with a destination user equipment over an indirect communication path via the relay user equipment, sidelink control information from the relay user equipment. The method may also include determining a first set of conditions and a second set of conditions based on the sidelink control information received from the relay user equipment. The method may also include transmitting, when the first set of conditions is satisfied, at least one of: a first sidelink message to the destination user equipment according to the first mode or a second sidelink message to the relay user equipment according to the second mode. Further, the method may include monitoring sidelink feedback from the destination user equipment to the relay user equipment when the second set of conditions is satisfied according to a third mode.

Description

Related Applications

[0001] This application claims priority to U.S. Application No. 17 / 963,043, filed on October 10, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0002] Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE) or fifth generation (5G) New Radio (NR) access technologies, or beyond 5G or other communication systems. For example, certain example embodiments may relate to apparatus, systems and / or methods for path switching in user equipment to user equipment (U2U) relays. Background Art

[0003] Examples of mobile or wireless telecommunication systems may include Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), LTE Evolved UTRAN (E-UTRAN), Advanced LTE (LTE-A), MulteFire, LTE-A Pro and / or fifth generation (5G) radio access technology or NR access technology. 5G wireless systems refer to next generation (NG) radio systems and network architectures. 5G network technology is primarily based on New Radio (NR) technology, but 5G (or NG) networks may also be built on E-UTRAN radios. It is estimated that NR can provide bit rates of approximately 10-20 Gbit / s or higher, and can support at least enhanced mobile broadband (eMBB) and ultra-reliable low latency communications (URLLC) and massive machine type communications (mMTC). NR is expected to provide extreme broadband and ultra-robust, low latency connectivity and massive networking to support IoT. Summary of the invention

[0004] Some example embodiments may relate to a method. The method may include monitoring side link control information from a relay user device by a source user device that communicates with a destination user device through an indirect communication path via the relay user device. The method also includes: determining a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The method also includes: when the first set of conditions is met, sending at least one of the following: a first side link message to the destination user device according to a first mode or a first side link message to the destination user device according to the first mode. In addition, the method includes: when the second set of conditions is met, monitoring side link feedback from the destination user device to the relay user device according to a third mode.

[0005] Other example embodiments may relate to a device. The device may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may also be configured to, together with the at least one processor, enable the device to at least monitor side link control information from a relay user device. According to certain example embodiments, the device may communicate with a destination user device via an indirect communication path via a relay user device. The device may also be configured to determine a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The device may also be configured to send at least one of the following when the first set of conditions is met: a first side link message to a destination user device according to a first mode or a second side link message to a relay user device according to a second mode. In addition, when the second set of conditions is met, the device may be configured to monitor side link feedback from the destination user device to the relay user device according to a third mode.

[0006] Other example embodiments may relate to an apparatus. The apparatus may include a component for monitoring side link control information from a relay user device. According to certain example embodiments, the apparatus may communicate with a destination user device via an indirect communication path via the relay user device. The equipment may also include: a component for determining a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The apparatus may also include: a component for sending at least one of the following, the at least one of which includes a first side link message to the destination user device according to a first mode when the first set of conditions is met or a second side link message to the relay user device according to a second mode. In addition, the apparatus may include a component for monitoring side link feedback from the destination user device to the relay user device according to a third mode when the second set of conditions is met.

[0007] According to other example embodiments, a non-transitory computer-readable medium may be encoded with instructions that, when executed in hardware, may perform a method. The method may include: monitoring side link control information from a relay user device by a source user device that communicates with a destination user device through an indirect communication path via the relay user device. The method also includes: determining a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The method also includes: when the first set of conditions is met, sending at least one of the following: a first side link message to the destination user device according to the first mode or a first side link message to the destination user device according to the first mode. In addition, the method includes: when the second set of conditions is met, monitoring side link feedback from the destination user device to the relay user device according to a third mode.

[0008] Other example embodiments may relate to a computer program product that performs a method. The method may include: monitoring side link control information from a relay user device by a source user device that communicates with a destination user device through an indirect communication path via a relay user device. The method also includes: determining a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The method also includes: when the first set of conditions is met, sending at least one of the following: a first side link message to the destination user device according to the first mode or a first side link message to the destination user device according to the first mode. In addition, the method includes: when the second set of conditions is met, monitoring side link feedback from the destination user device to the relay user device according to a third mode.

[0009] Other example embodiments may relate to an apparatus that may include a circuit configured to monitor side link control information from a relay user device. In certain example embodiments, the apparatus may communicate with a destination user device via an indirect communication path via the relay user device. The apparatus may also include a circuit configured to determine a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The apparatus may also include: a circuit configured to send at least one of a first side link message to a destination user device according to a first mode or a second side link message to a relay user device according to a second mode when the first set of conditions is met. In addition, the apparatus may include a circuit configured to monitor side link feedback from a destination user device to a relay user device when the second set of conditions is met according to a third mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a proper understanding of the example embodiments, reference should be made to the accompanying drawings, in which:

[0011] FIG1( a ) shows an example new radio (NR) side link (SL) resource allocation in Mode 1.

[0012] Figure 1(b) shows an example NR SL resource allocation in Mode 2.

[0013] Figure 2 An example of a scenario showing an indirect path according to some example embodiments.

[0014] Figure 3 Example coverage areas of a sidelink control information (SCI) message from a relay user equipment (UE) toward a destination (DST) UE are shown in accordance with certain example embodiments.

[0015] Figure 4 Examples of situations where a source UE and a DST UE may / may not communicate directly are shown according to certain example embodiments.

[0016] Figure 5 An example flow diagram of operations performed by a source (SRC) UE is shown in accordance with certain example embodiments.

[0017] Figure 6 An example flow chart of another method according to certain example embodiments is shown.

[0018] Figure 7 A set of apparatuses according to certain example embodiments is shown. DETAILED DESCRIPTION

[0019] It will be readily appreciated that the components of certain example embodiments as generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations. The following is a detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for path switching in U2U relaying. For example, certain example embodiments may be directed to providing support for path switching from an indirect path to a direct path in a sidelink-based (SL-based) U2U relay.

[0020] The features, structures, or characteristics of the example embodiments described throughout the specification may be combined in any suitable manner in one or more example embodiments. For example, throughout the specification, the use of the phrases "certain embodiments," "example embodiments," "some embodiments," or other similar language refers to the fact that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment. Therefore, throughout the specification, the appearance of the phrases "in certain embodiments," "example embodiments," "in some embodiments," "in other embodiments," or other similar language does not necessarily refer to the same set of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. In addition, the terms "cell," "node," "gNB," "network," or other similar language may be used interchangeably throughout the specification.

[0021] As used herein, “at least one of: ” and “at least one of ” and similar expressions, where a list of two or more elements is connected by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0022] As described in the technical specifications of the 3rd Generation Partnership Project (3GPP), SL communication has been designed to facilitate UEs to communicate with other nearby UEs via direct SL communication. 3GPP also specifies two resource allocation modes, and a SL transmitter (Tx) UE that is configured with one of the modes to perform NR SL transmission. These modes are represented as NR SL Mode 1 and NRSL Mode 2. For example, Figure 1(a) shows an example NR SL resource allocation in Mode 1, and Figure 1(b) shows an example NR SL resource allocation in Mode 2. In Mode 1, SL transmission resources can be assigned (scheduled) to the SL Tx UE by the network (NW), while the SL Tx UE in Mode 2 autonomously selects its SL transmission resources.

[0023] In mode 1, the gNB may be responsible for SL resource allocation, and the configuration and operation may be similar to that on the Uu interface shown in Figure 1(a). As shown in Figure 1(b), in mode 2, the SL UE may autonomously perform resource selection with the aid of a sensing process. For example, a SL Tx UE in NR SL mode 2 may first perform a sensing process on a configured SL transmission resource pool so that the SL Tx UE may obtain knowledge of the reserved resources by other nearby SL Tx UEs. Based on the knowledge obtained from the sensing, the SL Tx UE may select resources from the available SL resources accordingly. In order for the SL UE to perform sensing and obtain the necessary information for receiving SL transmissions, the SL UE may decode sidelink control information (SCI) from other SL Tx UEs in the vicinity of the SL UE.

[0024] The SCI may follow a 2-stage SCI structure, which may support the size differences between the SCIs required for various NR vehicle-to-everything (V2X) SL service types (e.g., broadcast, groupcast, and unicast). For example, the first-stage SCI with SCI format 1-A may be carried by a physical sidelink control channel (PSCCH) and may include information for enabling sensing operations, as well as determining resource allocations for a physical sidelink shared channel (PSSCH) and information required for decoding the second-stage SCI.

[0025] For the second stage SCI of formats 2-A and 2-B, it can be carried by PSSCH (multiplexed with SL shared channel (SCH)). The second stage SCI may include source (Tx) and destination (Rx) identifiers. The second stage SCI may also include information for identifying and decoding associated SL-SCH transport blocks (TBs), and include control of hybrid automatic repeat request (HARQ) feedback in unicast / multicast. In addition, the second stage SCI may include a trigger for channel state information (CSI) feedback in unicast.

[0026] According to 3GPP, NRSL relays may be provided to support coverage extension in view of a wider range of uses including V2X, public safety, and commercial applications and services. That is, a UE that cannot communicate directly with the NW or another UE (for example, due to being out of coverage of the NW or another UE, or to save power) may use another UE. In this case, the other UE may correspond to a relay UE, and the relay UE may be used as a hop to reach the NW or another UE.

[0027] In addition, NR SL relay can provide a technical solution for SL relay using both layer 2-based relay architecture and layer 3-based relay architecture. However, due to lack of time, NR SL relay may include only limited features. Specifically, NR SL relay at the time of this application may only support UE to network relay, and its service continuity solution may be limited to direct to indirect and indirect to direct path switching within the gNB in ​​layer 2 relay. 3GPP provides support for U2U relay for SL coverage extension without relying on the use of uplink (UL) and downlink (DL). Therefore, in principle, a Tx UE (e.g., source (SRC) UE) can use the UE as a relay to reach the Rx UE (e.g., destination (DST) UE). In some cases, when referring to the case where only one relay UE is used between the SRC UE and the DST UE, the term single-hop U2U relay may be used.

[0028] In SL-based unicast communication, the SRC UE (Tx UE) and the DST UE (Rx UE) may use a direct SL communication path (i.e., a direct path) when they are in direct SL proximity to each other, or use an indirect SL communication path (i.e., an indirect path) via a U2U relay UE when they are not in direct SL proximity to each other. Therefore, switching between a direct path and an indirect path may be expected, taking into account certain mobility or coverage scenarios of the SRC UE and the DST UE. For example, the SRC UE may move in and out of a basement or building with its holder (e.g., a public safety personnel) while communicating with a DST UE (e.g., a commander) outside a building or outside a building during a public safety mission. In this case, the direct path may be applicable when both the SRC UE and the DST UE are outside a basement or building, otherwise an indirect path needs to be used.

[0029] In order to support switching between a direct path and an indirect path, a method for triggering switching at the SRC UE and the DST UE may be provided. For switching from a direct path to an indirect path, the SRC UE or the DST UE may be able to detect that the received power of the corresponding SL communication signal between them drops below a configured threshold so as to trigger a possible switch to the indirect path. However, when considering how to trigger a possible switch from an indirect path to a direct path, it may be considered which of the SRC UE and the DST UE needs to monitor what corresponding SL communication signal for what reason and how to trigger a robust switch from an indirect path to a direct path.

[0030] In one solution, at least one of the SRC UE and the DST UE may be configured to periodically detect each other's direct reachability by periodically sending reference signals or messages to each other on the SL at the maximum allowed transmit power while using an indirect path. However, when the SRC UE and the DST UE are not close to each other when using the indirect path, this solution may require significant overhead in terms of resource consumption of UE power and radio resources. In addition, the periodic transmission of such "probe" signals or messages with the maximum allowed transmit power may cause interference to nearby UEs and should therefore be limited as much as possible. Therefore, certain example embodiments described herein may provide options for supporting path switching from an indirect path to a direct path for SRC UE and DST UE when communicating with each other via a U2U relay UE. In doing so, overhead, interference, and standardization impacts may be minimized.

[0031] Figure 2 An example of a scenario for an indirect path according to certain example embodiments is shown. As described herein, certain example embodiments may provide solutions as to how an SRC UE and a DST UE using an indirect path via a relay UE may identify the possibility of switching to direct SL communication with limited impact on the power usage and signaling overhead of the SRC UE and / or the DST UE, and limited interference introduced to other nearby UEs. For example, Figure 2 As shown, there may be some scenarios where an indirect path between an SRS UE and a DST UE is provided via a serving U2U relay UE (i.e., a relay UE is in the middle, a relay UE is closer to the SRS UE, and a relay UE is closer to the DST UE). Figure 2 In scenario (c), the SRC UE may not be able to receive SL signals such as SCI sent from the U2U relay UE to the DST UE on the PSCCH and PSSCH due to the possible use of transmit power control (TPC) on the unicast SL connection. Figure 2In scenarios (a) and (b), the SRC UE can receive the SCI sent by the relay UE to the DST UE, while in scenario (c), the transmission from the relay UE to the DST UE may not reach the SRS UE. Figure 3 , where the coverage area of ​​the SCI message from the relay UE towards the DST UE is indicated.

[0032] exist Figure 2 In scenarios (a) and (b), since the SRS UE may be able to estimate the path loss distance between the SRS UE and the relay UE based on its own transmit power level toward the relay UE (e.g., the higher the transmit power level that the SRS UE needs to use for SL transmission toward the relay UE, the higher or longer the path loss distance between the SRS UE and the relay UE), the SRS UE may be able to determine the probability that the DST UE may be within the SL range of the SRS UE. According to certain example embodiments, considering the transmit power level used by the SRC UE for SL transmission to the relay UE, the determination of the probability may be based on a comparison of the received power level of the received SCI sent by the relay UE to the DST UE and the received power level of the corresponding SL signal sent by the relay UE to the SRC UE. That is, since the SRC UE may be able to estimate the path loss distance between the SRC UE and the relay UE based on the transmit power level that the SRC UE is using to send the corresponding signal or message to the relay UE and the receive power level on the corresponding signal or message from the relay UE that the SRC UE is receiving, the SRC UE may also be able to estimate the path loss distance between the relay UE and the DST UE based on the receive power level on the SCI sent by the relay UE to the DST UE and received by the SRC UE. Note that the transmit power level that the SRC UE is using for SL transmission toward the relay UE may reflect the path loss distance between the SRC UE and the relay UE. In addition, due to the transmit power control on the unicast SL connection between the SRC UE and the relay UE, the transmit power level may be adapted by the SRC UE based on the receive power level on the corresponding signal or message from the relay UE to the SRC UE. Figure 4 An example of a situation where an SRC UE and a DST UE can / cannot communicate directly according to certain exemplary embodiments is shown. Specifically, Figure 4 Some examples of path losses that can be considered in path switching are shown.

[0033] Based on the above analysis and exploration of possible uses of existing SL signals and messages for minimizing the impact of standardization, certain example embodiments may provide an efficient method for supporting path switching from an indirect path to a direct path when an SRC UE and a DST UE communicate with each other via a U2U relay UE. Specifically, according to certain example embodiments, based on continuous SCI monitoring, the SRC UE may determine whether the SRC UE has sufficiently received the SCI sent by the relay UE to the DST UE (as expected in the U2U relay operation of the indirect path) according to configuration conditions (i.e., the received SCI satisfies the configuration conditions; the received SCI may be decodable, and the received power on the received SCI may be above a threshold at the SRC UE).

[0034] According to certain example embodiments, it may be assumed that the L2 IDs of the U2U relay UE and the DST UE (which are used as the SRC ID and DST ID as indicated in the SCI from the U2U relay UE to the DST UE) are known to the SRC UE (e.g., based on the establishment of the indirect path). That is, for the establishment and maintenance of the U2U relay connection for the indirect path, the L2 IDs of the corresponding SRC UE, DST UE, and relay UE may be signaled and maintained between the SRC UE, the DST UE, and the relay UE. Therefore, the SRC UE may be able to determine which SCI received (and successfully decoded) at the SRC UE was sent by the relay UE to the DST UE. Additionally, in certain example embodiments, the SRC UE may determine that it has sufficiently received the SCI sent by the relay UE to the DST UE if the following conditions are met: (i) the SRC UE receives at least one SCI sent from the relay UE to the DST UE within the monitoring time window; and (ii) a received power (RxPw) level on the at least one received SCI is above a first RxPw threshold (e.g., within 1 second of the RxPw threshold). Figure 2 Otherwise, the SRC UE may determine that it has not adequately received the SCI sent by the relay UE to the DST UE (e.g., Figure 2 In some example embodiments, when the SRC UE performs continuous SCI monitoring, if the SRC UE directly and sufficiently receives the SCI sent by the DST UE so that the received power level on the received SCI from the DST UE is higher than a threshold (i.e., a configured RxPw threshold), the SRC UE may initiate a path switch from an indirect path to a direct path with the DST UE.

[0035] In certain example embodiments, the monitoring time window may be set by the SRC UE according to an end-to-end packet delay budget for data traffic that the SRC UE is sending to the DST UE via a relay UE (e.g., one or more thereof), according to a configuration from the SRC UE's serving network. In a simpler option, a semi-static duration may be configured or set for the monitoring time window. However, in some example embodiments, the determination of which option to use and its constraints may be configured or pre-configured to the SRC UE by the SRC UE's serving network, or left to the UE implementation at the SRC UE.

[0036] According to certain example embodiments, according to a configuration from a serving network of the SRC UE, a first RxPw threshold may be set by the SRC UE according to at least one of a received power level at the SRC UE on a SL transmission from the relay UE to the SRC UE and a transmit power level that the SRC UE is using for SL transmission to the relay UE. The received power level and the transmit power level may reflect the path loss distance between the SRC UE and the relay UE. In another example embodiment, a semi-static power level may be configured or set for the first RxPw threshold. However, the determination of which option to use and its constraints may be configured or pre-configured to the SRC UE by the serving network of the SRC UE, or left to the UE implementation at the SRC UE.

[0037] In certain example embodiments, when the SRC UE determines that it has not adequately received the SCI sent by the relay UE to the DST UE, the SRC UE may perform at least one of the following: further determine that it does not need to perform any action to facilitate possible path switching; send its own SCI to the relay UE, primarily for SL transmission of data traffic to the relay UE to be relayed by the relay UE to the DST UE, and secondarily for targeting the DST UE; or periodically send SL messages directly to the DST UE. Details of these options are described below.

[0038] As described above, in some example embodiments, the SRC UE may determine that it may not need to perform any action to facilitate a possible path switch. This may occur, for example, when the SRS UE does not receive any SCI sent by the relay UE to the DST UE within the monitoring time window (meaning that the SRS UE is much farther from the relay UE than the DST UE, e.g. Figure 2 ), and / or the transmit power level that the SRS UE is using for SL transmission to the relay UE is higher than the first TxPw threshold (meaning that the path loss distance between the SRS UE and the relay UE is close to the upper limit of the direct SL range, and therefore the SRS UE and the DST UE may be outside the direct SL range).

[0039] In other example embodiments, when the SRC UE determines that it has not sufficiently received the SCI sent by the relay UE to the DST UE such that some of the SCI can be successfully received and decoded within the monitoring time window, but the receive power level on the received SCI may be below the first RxPw threshold and / or the transmit power level that the SRC UE is using for SL transmission to the relay UE is below the first TxPw threshold, the SRC UE may send its own SCI to the relay UE, primarily for SL transmission of data traffic to be relayed by the relay UE to the DST UE, but with a maximum allowed transmit power according to a predefined pattern (such as secondarily targeting the DST UE every nth SCI). In doing so, in the event that the DST UE is able to receive the SCI sent by the SRC UE to the relay UE, the DST UE may trigger a possible path switch based on SCI monitoring in regular SL operation. According to some example embodiments, the maximum allowed transmit power may be higher than the power level required for SL transmission from the SRC UE to the relay UE and within the power budget of the SRC UE, as determined by the SRC UE based on a configuration from the serving network. In some example embodiments, sending an SCI with a maximum allowed transmit power for triggering a path switch may be inconsistent with the power control specified for a unicast SL. Therefore, in some example embodiments, the relay UE may be made aware of the use of this option so that the relay UE will not adjust its Tx power towards the SRC UE based on receiving the nth SCI sent at the maximum allowed transmit power from the SRC UE. In some example embodiments, this option may be desirable when the SRC UE frequently sends data to the DST UE via the relay UE.

[0040] In another example embodiment, when the SRC UE determines that it has not sufficiently received the SCI sent by the relay UE to the DST UE so that some of the SCI can be successfully received and decoded within the monitoring time window, but the received power level on the received SCI can be lower than the first RxPw threshold and / or the transmit power level that the SRC UE is using for SL transmission to the relay UE can be lower than the first TxPw threshold, the SRC UE can periodically send SL messages directly to the DST UE using the maximum allowed transmit power while using an indirect path, such as reusing the discovery announcement, direct communication request (DCR) or SL channel state information (CSI) request sent in the SCI and the medium access control control element (MACCE), or reusing a "keep alive" PC5-S signaling message. When the DST UE is able to receive the SL message or at least its SCI directly from the SRC UE, performing this action can allow the DST UE to trigger a possible path switch (or if received by the SRC UE, help the SRC UE trigger a possible path switch based on a response from the DST UE). This option does not affect power control on the unicast SL connection between the SRC UE and the relay UE. In certain example embodiments, this option may be used when the SRC UE does not frequently send data to the DST UE via the relay UE.

[0041] According to certain example embodiments, the SRC UE may replicate periodic PC5-S signaling message (e.g., keep-alive message) transmissions to the relay UE and the DST UE. The replicated transmissions to the DST UE may use the maximum allowed transmit power, and the replication may be implemented using packet data convergence protocol (PDCP) replication for at least the L2 U2U relay. In this case, the default configuration of the lower layer protocols (e.g., radio link control (RLC), MAC, and physical (PHY) layers) may be directly used for the replicated transmissions between the SRC UE and the DST UE.

[0042] In certain example embodiments, when the SRC UE determines as described above that it has sufficiently received the SCI sent by the relay UE to the DST UE, the SRC UE may perform at least one of the following: determine that it does not need to perform any action to facilitate possible path switching, monitor the HARQ feedback sent from the DST UE to the relay UE on the physical sidelink feedback channel (PSFCH), or perform at least one of the following: send its own SCI to the relay UE for primary use for SL transmission and secondarily towards the DST UE, or periodically send SL messages, such as reusing discovery announcements, DCRs or SL CSI requests sent in the SCI and MAC CE, or reusing the "keep alive" PC5-S signaling message as described above.

[0043] As described above, when the SRC UE receives the SCI sent by the relay UE to the DST UE (i.e., since the SCI is broadcast, the SRC UE can monitor and receive such SCI), the SRC UE can determine that it does not need to perform any action to facilitate possible path switching. For example, when the SRS UE further determines that the received power level on the received SCI is higher than the second RxPw threshold and greater than the first RxPw threshold (meaning that the SRS UE is significantly closer to the relay UE than the DST UE, such as Figure 2 This determination can be made when the SRS UE is using a second TxPw threshold (as shown in scenario (b)), and / or the transmit power level that the SRS UE is using for SL transmission to the relay UE is higher than the second TxPw threshold (meaning that the path loss distance between the SRS UE and the relay UE is still high, so the SRS UE and the DST UE may be out of direct SL range).

[0044] As also described above, the SRC UE may monitor HARQ feedback from the DST UE to the relay UE. For example, according to certain example embodiments, when a received SCI sent from the relay UE to the DST UE indicates that SL HARQ with feedback is used between the relay UE and the DST UE, the SRC UE may monitor HARQ feedback sent from the DST UE to the relay UE on the PSFCH for the corresponding HARQ transmission according to the configured mode. In some example embodiments, the PSFCH resources used to send HARQ feedback by the DST UE to the relay UE may be derived from the resource allocation used to send the corresponding HARQ transmission by the SRC UE other than the DST UE, as indicated in the SCI of the corresponding HARQ transmission from the relay UE to the DST UE.

[0045] Based on whether the HARQ feedback from the DST UE to the relay UE is received and the received power level on the HARQ feedback received at the SRC UE, the SRC UE can trigger a possible path switch between the SRC UE and the DST UE. For example, if the received power level on the received HARQ feedback is higher than the third RxPw threshold, the SRC UE can initiate a direct path switching request to the DST UE (e.g., a request sent to the DST UE via the relay UE). In other example embodiments, the SRC UE can initiate a direct DCR to the DST UE to establish a direct unicast SL connection with the DST UE, and then further communicate with the DST UE to perform a path switch via the direct SL connection. In addition, in some example embodiments, both the direct path and the indirect path can be maintained and used for the transition period to avoid the ping-pong effect. The option of using DCR may mean that the non-access layer (PC5-S) above the access layer needs to be involved. Furthermore, when the SRC UE performs at least one of primarily sending its own SCI to the relay UE and secondarily targeting the DST UE or periodically sending SL messages directly to the DST UE, the request may be initiated by the DST UE when the DST UE receives the SCI or message from the SRC UE.

[0046] According to certain example embodiments, the option of the SRC UE monitoring the HARQ feedback from the DST UE to the relay UE can be considered as an alternative or supplement to the SRC UE sending its own SCI to the relay UE for SL transmission of data traffic to the relay UE to be primarily relayed to the DST UE and secondarily targeted to the DST UE or periodically sending SL messages directly to the above-mentioned DST UE. In other example embodiments, when the SRC UE frequently sends data to the DST UE via the relay UE, the option of the SRC UE monitoring the HARQ feedback from the DST UE to the relay UE can be used alone, or when the SRC UE does not frequently send data to the DST UE via the relay UE, the option of the SRC UE monitoring the HARQ feedback from the DST UE to the relay UE can be used with other options. It may also be necessary to make the relay UE aware of the use of this option so that it will not adjust its Tx power towards the DST UE based on the HARQ feedback received from the DST UE to be sent at the maximum allowed power, as further described below.

[0047] As described above, when the SRC UE determines that it receives an SCI sent by the relay UE to the DST UE, the received SCI may indicate that SL HARQ with feedback is not used between the relay UE and the DST UE. When this occurs, the SRC UE may perform at least one of the following: sending its own SCI primarily to the relay UE and secondarily targeting the DST UE, or periodically sending SL messages directly to the DST UE, as described in the above examples. In certain example embodiments, the option of sending its own SCI and periodically sending SL messages may be a supplement or alternative to the option of monitoring HARQ feedback, i.e., performing at least one of the following: sending its own SCI primarily to the relay UE and secondarily targeting the DST UE or periodically sending SL messages to the DST UE.

[0048] According to certain example embodiments, the above-mentioned configuration of conditions and constraints for actions performed by the SRC UE, and the above-mentioned patterns for sending and monitoring steps from the serving network to the SRC UE and the DST UE, can be based on common signaling (e.g., system information block (SIB)) for in-coverage operation and dedicated signaling or pre-configuration for out-of-coverage operation. In addition, a first set of conditions (i.e., related to when the SRC UE determines to perform at least one of sending its own SCI primarily to the relay UE and secondarily targeting the DST UE or periodically directing SL messages to the DST UE) and a second set of conditions (i.e., related to when the SRC UE determines to perform monitoring of HARQ feedback from the DST UE to the relay UE) can be used to trigger an indication from the SRC UE to the DST UE regarding the expectation and triggering the DST UE to participate, as further described below.

[0049] In certain example embodiments, the first set of conditions and the second set of conditions may not only relate to or correspond to, for example, the TxPw and RxPw thresholds provided above, but may also relate to, for example, whether HARQ with feedback is used between the relay UE and the DST UE, the frequency of data transmission from the SRC UE to the DST UE via the relay UE, and coordination between the SRC and DST UEs.

[0050] According to certain example embodiments, TxPw and RxPw thresholds may be introduced for SRC UEs to decide whether to send SL messages (e.g., DCR or SL CSI request MAC CE) or monitor HARQ feedback to reduce overhead. Therefore, in certain example embodiments, these thresholds may be considered as a common part of both the first set of conditions and the second set of conditions. In other example embodiments, TxPw and RxPw thresholds may be used for SRC UEs to determine the likelihood that the SRC UE may be within the direct coverage of the DST UE in order to trigger the sending step or the monitoring step or both.

[0051] In certain example embodiments, when the SRC UE and the DST UE communicate with each other using an indirect path, a first message, such as a SL discovery message or a direct communication request or a CSI request MAC CE, may be periodically sent from the SRC UE to the DST UE according to a first mode. In other example embodiments, the second message may be based on an SCI for SL transmission of data from the SRC UE to the relay UE to be relayed toward the DST UE. In some example embodiments, the SCI may be sent at the maximum allowed Tx power and according to a second mode, such as every nth SCI or SL transmission from the SRC UE to the relay UE. The SCI may be primarily used for SL transmission from the SRC UE to the relay UE, and secondly targeted at the DST UE. In some example embodiments, the second message may be a SL message from the SRC UE to the relay UE that is not relayed to the DST UE. The SL message may be a designated SCI combined with a MAC CE for the SRC UE to periodically detect the DST UE when using an indirect path via the relay UE. The SCI of the SL message may be sent by the SRC UE at the maximum allowed transmit power. The relay UE may ignore the SL message when receiving the SL message from the SRC UE.

[0052] As described above, the SRC UE may monitor HARQ feedback (i.e., SL feedback) from the DST UE. In certain example embodiments, the SL feedback to be monitored by the SRC UE may be based on utilizing HARQ feedback from the DST UE to the relay UE sent at the maximum allowed Tx power and according to the third mode. This option may be similar to utilizing SCI, but is sent by the DST UE and monitored by the SRC UE. According to certain example embodiments, the use of SL feedback monitoring may be triggered by the SRC UE to the DST UE. That is, the SRC UE may be responsible for determining that the second set of conditions are met and then indicating to the DST UE to activate the option.

[0053] Figure 5An example flow chart of operations performed by an SRC UE according to certain example embodiments is shown. At operation 500, the SRC UE may determine whether it has received an SCI from a relay UE to a DST UE according to a configured criterion or condition (e.g., a received power level of the SCI is above a first RxPw threshold). If the SRC UE has not received an SCI according to the configured criterion or condition, then at operation 505, the SRC UE may determine whether it has not received any SCI from the relay UE to the DST UE within a monitoring time window, or whether its transmit power level for SL transmission to the relay UE is above a first TxPw threshold. At operation 510, if the SRC UE determines that it has not received any SCI from the relay UE to the DST UE within the monitoring time window, or the transmit power level for SL transmission from the SRC UE to the relay UE is not higher than the first TxPw threshold, the SRC UE may send its own SCI to the relay UE for SL transmission of data relayed to the DST UE at the maximum allowed transmit power according to a predefined pattern (such as, every nth SCI). At operation 515, the SRC UE may send a SL message, such as, for example, a DCR or SL CSI request MAC CE, directly to the DST UE using the maximum allowed transmit power. Operation 515 may be performed in addition to or instead of operation 510.

[0054] like Figure 5 As further shown, when the SRC UE determines that it receives an SCI from the relay UE to the DST UE according to a configured standard or condition, at operation 520, the SRC UE may determine whether the received power level on the received SCI from the relay UE to the DST UE is higher than the second RxPw threshold, and / or whether the transmit power level used for SL transmission to the relay UE is higher than the second TxPw threshold. If the result at operation 520 is no, at operation 525, the SRC UE may determine whether HARQ with feedback is used between the relay UE and the DST UE. If the SRC UE determines that HARQ with feedback is used, at operation 530, the SRC UE may monitor HARQ feedback from the DST UE to the relay UE. In addition, at operation 535, if the received power level on the received HARQ feedback is higher than the third RxPw threshold, the SRC UE may initiate a path switching request to the DST UE.

[0055] refer to Figure 5In some example embodiments, operation 510 and / or operation 515 may be performed before or after operation 525. In addition, the SRC UE may be configured to adapt whether to perform one or both of the transmission in operation 510 and / or operation 515 and / or the monitoring in operation 530 when the corresponding conditions are met. The SRC UE may also be configured to adapt a transmission mode including a maximum allowed transmission power for transmitting its own SCI to the relay UE or a SL message to the DST UE, and / or a monitoring mode for monitoring HARQ feedback from the DST UE to the relay UE. In some example embodiments, these adaptations may be based on measurements of the SCI received from the relay UE at the SRC UE, a channel busy rate (CBR) on the selected Tx resource pool, priority, and other QoS requirements of the data traffic between the SRC UE and the DST UE.

[0056] According to other example embodiments, after operation 520, if the SRC UE determines that the DST UE may be close enough to the SRC UE, the SRC UE may choose to transmit in operation 510 and / or operation 515 instead of monitoring in operation 530. In this case, the SRC UE may use the maximum allowed Tx power adjusted based on the necessary transmit power to reach the DST UE determined on the basis of the conditions determined in operation 520. In other example embodiments, when the CBR is high, the SRC UE may prioritize the monitoring in operation 530 over the transmission in operation 510 and / or operation 515. In yet another example embodiment, when the traffic is highly delay sensitive with a high priority, the SRC UE may perform all transmissions in operation 510 and / or operation 515 and the monitoring in operation 530 when the corresponding conditions are met. Therefore, in some example embodiments, the CBR condition, QoS requirements, and / or data traffic patterns (such as the frequency with which the SRC UE transmits data to the DST UE) may be considered as part of the first set of conditions and / or the second set of conditions. In some example embodiments, the first set of conditions may be a subset of the second set of conditions.

[0057] In certain example embodiments, when acting as a Tx UE or SRC UE for the corresponding direction, both the SRC UE and the DST UE may be configured by the service NW to perform the above operations in a two-way SL communication. In other example embodiments, the SRC UE and the DST UE in the two-way SL communication may be configured by the service network to independently determine at the SRC UE and the DST UE which of the SRC UE and the DST UE is closer to the relay UE or has a lower or shorter path loss distance to perform the above operations. In certain example embodiments, operations may be performed when the SRC UE or the DST UE acts as a Tx UE (i.e., SRC UE) for the corresponding direction in a two-way communication. In order to ensure that at least one of the SRC UE and the DST UE will perform operations when acting as a Tx UE for the corresponding direction in bidirectional communication, a robust offset may be configured to allow the SRC UE and the DST UE to determine whether the difference between the received power level on the received SCI sent from the relay UE to the SRC UE and the received power level on the received SCI sent from the relay UE to the DST UE is higher than the offset. According to certain example embodiments, the determination may be performed by the SRC UE and the DST UE in bidirectional communication to determine whether the SRC UE and the DST UE (when acting as a Tx UE) need to perform the above operations.

[0058] According to certain example embodiments, the relay UE may determine the transmit power required to reach the SRC UE and the DST UE, and may evaluate the possibility of direct communication between the SRC UE and the DST UE, and trigger either the SRC UE or the DST UE to switch to a direct path or perform the above-mentioned transmission and / or monitoring operations. In certain example embodiments, the determination may be based on determining that the sum of TxPw-SRC (the Tx power required to reach the SRC UE) and TxPw-DST (the Tx power required to reach the DST-UE) is less than a third TxPw threshold. The third TxPw threshold may be set to the maximum allowed transmit power plus or minus an offset.

[0059] In other example embodiments, when the SRS UE determines that the conditions for monitoring the HARQ feedback from the DST UE to the relay UE are met (see Figure 5In operation 520 and operation 525 in the above), the SRSUE may send an indication to the DST UE via the relay UE. The indication may be used to trigger the DST UE to send HARQ feedback to the relay UE on the PSFCH at the maximum allowed power according to the mode. For example, the mode may be configured for the upcoming HARQ process, or for a configured time interval starting from the moment the indication from the SRC UE is received. In other example embodiments, the mode may be configured for all HARQ feedbacks for the upcoming HARQ process, or for up to a configured maximum number of HARQ feedbacks within a configured time interval. Therefore, certain example embodiments may further enhance the scheme with minimized overhead in terms of the transmit power of the DST UE. Certain example embodiments may also be applicable during unidirectional data communication from the SRC UE to the DST UE.

[0060] It may be noted that in some example embodiments, when the conditions for monitoring HARQ feedback from the DST UE to the relay UE are met, the SRC UE may monitor the HARQ feedback from the DST UE to the relay UE, regardless of knowing or not knowing the transmission mode of the HARQ feedback from the DST UE. Thus, the monitoring mode of the SRC UE may or may not correspond to or depend on the transmission mode of the DST UE. In other example embodiments, the maximum allowed transmit power may be considered as part of the transmission mode.

[0061] Figure 6 An example flow chart of a method according to certain example embodiments is shown. In an example embodiment, Figure 6 The method may be performed by a network entity or a set of multiple network elements in a 3GPP system (such as LTE or 5G-NR). For example, in an example embodiment, Figure 6 The method can be similar to Figure 7 The method is performed by a UE or SRC UE of one of the apparatuses 10 or 20 shown in FIG.

[0062] According to certain example embodiments, Figure 6The method may include: at 600, monitoring side link control information from the relay user equipment by a source user equipment that communicates with the destination user equipment through an indirect communication path via the relay user equipment. The method may also include: at 605, determining a first set of conditions and a second set of conditions based on the side link control information received from the relay user equipment. The method may also include: at 610, when the first set of conditions is met, sending at least one of the following: a first side link message to the destination user equipment according to the first mode or a second side link message to the relay user equipment according to the second mode. In addition, the method may include: at 615, when the second set of conditions is met according to the third mode, monitoring the side link feedback from the destination user equipment to the relay user equipment.

[0063] According to certain example embodiments, determining the first set of conditions and the second set of conditions may include determining whether the sidelink control information sent by the relay user equipment to the destination user equipment is received according to a configured criterion, the configured criterion including whether a received power level from the relay user equipment to the destination user equipment on the sidelink control information is higher than a first received power threshold. The determination also includes determining whether the source user equipment receives any sidelink control information sent by the relay user equipment to the destination user equipment within a configured monitoring time window, or whether a transmit power level for performing a sidelink transmission from the source user equipment to the relay user equipment is higher than a first transmit power threshold. The determination also includes determining at least one of the following: whether the received power level on the sidelink control information from the relay user equipment to the destination user equipment is higher than a second received power threshold, or whether a transmit power level for performing a sidelink transmission from the source user equipment to the relay user equipment is higher than a second transmit power threshold. According to some example embodiments, determining the second set of conditions may include determining whether a hybrid automatic repeat request with feedback is used between the relay user equipment and the destination user equipment. In certain example embodiments, the method may further include: when a received power level on the sidelink feedback from the destination user equipment to the relay user equipment is higher than a third received power threshold, initiating a path switching request to the destination user equipment. According to other example embodiments, the first sidelink message may include a discovery notification, a direct communication request, a keep-alive message, or a sidelink channel state information request, and the first sidelink message may be sent directly to the destination user equipment. According to other example embodiments, the second sidelink message is sidelink control information for sidelink transmission of data from the source user equipment to the relay user equipment, where the data will be relayed to the destination device. According to other example embodiments, the sidelink feedback is HARQ feedback from the destination user equipment to the relay user equipment.

[0064] In certain example embodiments, when at least one of the first set of conditions or the second set of conditions is met, the method may also include: determining that the destination user equipment is outside the side link range of the source user equipment, and communicating with the destination user equipment via an indirect communication path via a relay user equipment, without performing at least one of sending a first side link message to the destination user equipment according to the first mode or sending a second side link message to the relay user equipment according to the second mode, or monitoring the side link feedback from the destination user equipment to the relay user equipment according to the third mode. In some example embodiments, the second side link message may be sent to the relay user equipment at a maximum allowed transmit power. In other example embodiments, the maximum allowed transmit power may be an amount of power that is higher than the power level required to send the second side link message to the relay user equipment, and may be within a predefined power budget. In other example embodiments, at least when the second set of conditions is met, the SRC UE may send an indication to the DST UE via the relay UE, indicating that the source UE is performing monitoring of SL feedback from the DST UE to the relay UE (to trigger the DST UE to send SL feedback according to a mode that may be the same as or different from the third mode).

[0065] Figure 7 A set of apparatuses 10 and apparatuses 20 according to some example embodiments are shown. In some example embodiments, apparatus 10 may be an element in a communication network or an element associated with such a network, such as a UE, a mobile equipment (ME), a mobile station, a mobile device, a fixed device, an IoT device, or other device. It should be noted that a person skilled in the art will understand that apparatus 10 may include Figure 7 Components or features not shown.

[0066] In some example embodiments, the apparatus 10 may include one or more processors, one or more computer-readable storage media (e.g., memory, storage, etc.), one or more radio access components (e.g., modems, transceivers, etc.), and / or a user interface. In some example embodiments, the apparatus 10 may be configured to operate using one or more radio access technologies, such as GSM, LTE, LTE-A, NR, 5G, WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and / or any other radio access technology.

[0067] like Figure 7As shown in the example of , the device 10 may include or be coupled to a processor 12 for processing information and executing instructions or operations. The processor 12 may be any type of general or special purpose processor. In fact, as an example, the processor 12 may include one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), and a processor based on a multi-core processor architecture. Although Figure 7 A single processor 12 is shown in FIG. 1 , but according to other example embodiments, multiple processors may be utilized. For example, it should be understood that in some example embodiments, the apparatus 10 may include two or more processors that may form a multiprocessor system that may support multiprocessing (e.g., in which case the processor 12 may represent a multiprocessor). According to some example embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

[0068] Processor 12 may perform functions associated with the operation of device 10, including, as some examples, precoding of antenna gain / phase parameters, encoding and decoding of individual bits forming communication messages, formatting of information, and overall control of device 10, including FIGS. 1 to 3. Figure 6 The process and examples shown in .

[0069] The device 10 may also include or be coupled to a (internal or external) memory 14, which may be coupled to the processor 12 for storing information and instructions that may be executed by the processor 12. The memory 14 may be one or more memories and of any type suitable for the local application environment, and may be implemented using any suitable volatile or non-volatile data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and / or removable memory. For example, the memory 14 may include any combination of random access memory (RAM), read-only memory (ROM), static storage devices such as magnetic disks or optical disks, hard disk drives (HDDs), or any other type of non-transitory machine or computer readable media. The instructions stored in the memory 14 may include program instructions or computer program code that, when executed by the processor 12, enables the device 10 to perform tasks as described herein.

[0070] In some example embodiments, the apparatus 10 may also include or be coupled to a (internal or external) drive or port configured to accept and read an external computer-readable storage medium, such as an optical disk, a USB drive, a flash drive, or any other storage medium. For example, the external computer-readable storage medium may store data for execution by the processor 12 and / or the apparatus 10 to perform the operations of FIGS. 1 to 3. Figure 6Any of the methods and examples shown may be computer programs or software.

[0071] In some example embodiments, the apparatus 10 may also include or be coupled to one or more antennas 15 for receiving downlink signals and transmitting from the apparatus 10 via the UL. The apparatus 10 may also include a transceiver 18 configured to send and receive information. The transceiver 18 may also include a radio interface (e.g., a modem) coupled to the antenna 15. The radio interface may correspond to a variety of radio access technologies, including one or more of GSM, LTE, LTE-A, 5G, NR, WLAN, NB-IoT, Bluetooth, BT-LE, NFC, RFID, UWB, etc. The radio interface may include other components, such as filters, converters (e.g., digital-to-analog converters, etc.), symbol demappers, signal shaping components, inverse fast Fourier transform (IFFT) modules, etc., to process symbols carried by the downlink or UL, such as OFDMA symbols.

[0072] For example, the transceiver 18 may be configured to modulate information onto a carrier waveform for transmission by the antenna 15, and to demodulate information received via the antenna 15 for further processing by other elements of the apparatus 10. In other example embodiments, the transceiver 18 may be capable of directly sending and receiving signals or data. Additionally or alternatively, in some example embodiments, the apparatus 10 may include input and / or output devices (I / O devices). In certain example embodiments, the apparatus 10 may also include a user interface, such as a graphical user interface or a touch screen.

[0073] In certain example embodiments, memory 14 stores software modules that provide functionality when executed by processor 12. The modules may include, for example, an operating system that provides operating system functionality for device 10. The memory may also store one or more functional modules, such as applications or programs, to provide additional functionality for device 10. The components of device 10 may be implemented in hardware, or in any suitable combination of hardware and software. According to certain example embodiments, device 10 may optionally be configured to communicate with device 20 via a wireless or wired communication link 70 according to any radio access technology, such as NR.

[0074] According to some example embodiments, the processor 12 and the memory 14 may be included in or may form part of a processing circuit or a control circuit. In addition, in some example embodiments, the transceiver 18 may be included in or may form part of a transceiver circuit.

[0075] For example, in certain example embodiments, the device 10 may be controlled by the memory 14 and the processor 12 to monitor side link control information from a relay user device, wherein the device communicates with the destination user device via the relay user device through an indirect communication path. The device 10 may also be controlled by the memory 14 and the processor 12 to determine a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The device 10 may also be controlled by the memory 14 and the processor 12 to send at least one of the following when the first set of conditions is met: a first side link message to the destination user device according to a first mode or a second side link message to the relay user device according to a second mode. In addition, the device 10 may be controlled by the memory 14 and the processor 12 to monitor the side link feedback from the destination user device to the relay user device according to a third mode when the second set of conditions is met.

[0076] like Figure 7 As shown in the example of , the apparatus 20 may be an element in a network, a core network element, or a communication network or an element associated with such a network, such as a gNB or a NW. It should be noted that a person skilled in the art will understand that the apparatus 20 may include Figure 7 Components or features not shown.

[0077] like Figure 7 As shown in the example of , the device 20 may include a processor 22 for processing information and executing instructions or operations. The processor 22 may be any type of general-purpose or special-purpose processor. For example, as an example, the processor 22 may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), and a processor based on a multi-core processor architecture. Although Figure 7 A single processor 22 is shown in FIG. 1 , but multiple processors may be utilized according to other example embodiments. For example, it should be understood that in some example embodiments, the apparatus 20 may include two or more processors that may form a multiprocessor system that may support multiprocessing (e.g., in which case the processor 22 may represent a multiprocessor). In some example embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

[0078] According to certain example embodiments, processor 22 may perform functions associated with the operation of device 20, which may include, for example, precoding of antenna gain / phase parameters, encoding and decoding of individual bits forming communication messages, formatting of information, and overall control of device 20, including FIGS. 1 to 3. Figure 5 The process and examples shown.

[0079] The device 20 may also include or be coupled to a memory 24 (internal or external), which may be coupled to the processor 22 for storing information and instructions that may be executed by the processor 22. The memory 24 may be one or more memories and of any type suitable for the local application environment, and may be implemented using any suitable volatile or non-volatile data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and / or removable memory. For example, the memory 24 may include any combination of random access memory (RAM), read-only memory (ROM), static storage devices such as magnetic disks or optical disks, hard disk drives (HDDs), or any other type of non-transitory machine or computer-readable media. The instructions stored in the memory 24 may include program instructions or computer program code that, when executed by the processor 22, enables the device 20 to perform tasks as described herein.

[0080] In some example embodiments, the apparatus 20 may also include or be coupled to a (internal or external) drive or port configured to accept and read an external computer-readable storage medium, such as an optical disk, a USB drive, a flash drive, or any other storage medium. For example, the external computer-readable storage medium may store data for execution by the processor 22 and / or the apparatus 20 to perform the operations of FIGS. 1 to 3. Figure 5 The methods and examples are shown as computer programs or software.

[0081] In certain example embodiments, the apparatus 20 may also include or be coupled to one or more antennas 25 for transmitting signals and / or data to and receiving signals and / or data from the apparatus 20. The apparatus 20 may also include or be coupled to a transceiver 28 configured to transmit and receive information. The transceiver 28 may include, for example, a plurality of radio interfaces that may be coupled to the antennas 25. The radio interfaces may correspond to a variety of radio access technologies, including one or more of GSM, NB-IoT, LTE, 5G, WLAN, Bluetooth, BT-LE, NFC, Radio Frequency Identifier (RFID), Ultra-Wideband (UWB), MulteFire, etc. The radio interfaces may include components such as filters, converters (e.g., digital-to-analog converters, etc.), mappers, Fast Fourier Transform (FFT) modules, etc., to generate symbols for transmission via one or more downlinks and receive symbols (e.g., via UL).

[0082] Thus, the transceiver 28 may be configured to modulate information onto a carrier waveform for transmission by the antenna 25, and to demodulate information received via the antenna 25 for further processing by other elements of the apparatus 20. In other example embodiments, the transceiver 18 may be capable of directly sending and receiving signals or data. Additionally or alternatively, in some example embodiments, the apparatus 20 may include input and / or output devices (I / O devices).

[0083] In certain example embodiments, memory 24 may store software modules that provide functionality when executed by processor 22. The modules may include, for example, an operating system that provides operating system functionality for device 20. The memory may also store one or more functional modules, such as applications or programs, to provide additional functionality to device 20. The components of device 20 may be implemented in hardware or any suitable combination of hardware and software.

[0084] According to some example embodiments, the processor 22 and the memory 24 may be included in or may form part of a processing circuit or a control circuit. In addition, in some example embodiments, the transceiver 28 may be included in or may form part of a transceiver circuit.

[0085] As used herein, the term "circuit" may refer to a hardware circuit implementation only (e.g., analog and / or digital circuits), a combination of hardware circuits and software, a combination of analog and / or digital hardware circuits and software / firmware, any portion of a hardware processor (including a digital signal processor) with software that works together to enable a device (e.g., device 10 and device 20) to perform various functions, and / or a hardware circuit and / or processor, or portion thereof, that uses software to operate, but the software may not be present when the software is not required to operate. As another example, as used herein, the term "circuit" may also cover an implementation of a hardware circuit or processor (or multiple processors), or a portion of a hardware circuit or processor and its accompanying software and / or firmware. The term circuit may also cover, for example, a baseband integrated circuit in a server, a cellular network node or device, or other computing or network device.

[0086] In some example embodiments, an apparatus (e.g., apparatus 10 and / or apparatus 20) may include components for performing the methods, processes, or any variations discussed herein. Examples of components may include one or more processors, memories, controllers, transmitters, receivers, and / or computer program codes for causing the execution of operations.

[0087] Certain example embodiments may relate to an apparatus comprising components for performing any of the methods described herein, including, for example, components for monitoring side link control information from a relay user device, wherein the apparatus communicates with a destination user device via an indirect communication path via the relay user device. The apparatus may also include components for determining a first set of conditions and a second set of conditions based on the side link control information received from the relay user device. The apparatus may also include components for sending at least one of a first side link message to a destination user device according to a first mode or a second side link message to a relay user device according to a second mode when the first set of conditions is met. In addition, the apparatus may include: when the second set of conditions is met, monitoring side link feedback from the destination user device to the relay user device according to a third mode.

[0088] Certain example embodiments described herein provide several technical improvements, enhancements and / or advantages. For example, in some example embodiments, a trigger for a path switch from an indirect path to a direct path between a SRC UE and a DST UE may be configured in an efficient and robust manner with minimal standardized impact and overhead. According to other example embodiments, support for efficient unidirectional and bidirectional data communication between a SRC UE and a DST UE may also be provided. In addition, certain example embodiments may minimize the transmit power for a DST UE.

[0089] The computer program product may include one or more computer executable components that are configured to perform some example embodiments when the program is run. The one or more computer executable components may be at least one software code or part thereof. Modifications and configurations required to implement the functionality of some example embodiments may be performed as routines that may be implemented as added or updated software routines. The software routines may be downloaded into a device.

[0090] As an example, the software or computer program code or part thereof may be in source code form, object code form or some intermediate form, and it may be stored in some carrier, distribution medium or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers may include, for example, recording media, computer memory, read-only memory, optoelectronic and / or electrical carrier signals, telecommunication signals and software distribution packages. Depending on the processing power required, the computer program may be executed in a single electronic digital computer, or may be distributed among multiple computers. The computer readable medium or computer readable storage medium may be a non-transient medium.

[0091] In other example embodiments, the functions may be performed by hardware or circuitry included in a device (e.g., device 10 or device 20), such as by using an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In yet another example embodiment, the functions may be implemented as signals, non-tangible components that may be carried by electromagnetic signals downloaded from the Internet or other networks.

[0092] According to certain example embodiments, an apparatus such as a node, a device or a corresponding component may be configured as a circuit, a computer or a microprocessor (such as a single-chip computer element), or as a chipset, which includes at least a memory for providing storage capacity for arithmetic operations and an operation processor for performing arithmetic operations.

[0093] Those of ordinary skill in the art will readily appreciate that the disclosure described above may be practiced using processes in a different order and / or using hardware elements in a configuration different from that disclosed. Therefore, although the present disclosure has been described based on these example embodiments, it will be apparent to those skilled in the art that certain modifications, variations, and alternative configurations will be apparent while remaining within the spirit and scope of the example embodiments. Although the above embodiments relate to 5GNR and LTE technologies, the above embodiments may also be applied to any other current or future 3GPP technologies, such as Advanced LTE and / or fourth generation (4G) technologies.

[0094] Partial glossary:

[0095] 3GPP Third Generation Partnership Project

[0096] 5G Fifth Generation

[0097] 5GCN 5G Core Network

[0098] 5GS 5G System

[0099] BS Base Station

[0100] CBR Channel Busy Rate

[0101] DCI Downlink Control Information

[0102] DL Downlink

[0103] DST destination

[0104] eNB Enhanced Node B

[0105] E-UTRAN Evolved UTRAN

[0106] FC Flow Control

[0107] gNB 5G or Next Generation NodeB

[0108] HARQ Hybrid Automatic Repeat Request

[0109] InS Sync

[0110] IUC Inter-UE Coordination

[0111] LTE Long Term Evolution

[0112] MCS Modulation and Coding Scheme

[0113] NR New Radio

[0114] NW Network

[0115] PDB Packet Delay Budget

[0116] PSCCH Physical Sidelink Control Channel

[0117] PSSCH Physical Sidelink Shared Channel

[0118] QoS Quality of Service

[0119] RRC Radio Resource Control

[0120] SCI Side Link Control Information

[0121] SL Side Link

[0122] SIB System Information Block

[0123] SRC Source

[0124] TB Transfer Block

[0125] TBS Transport Block Size

[0126] TPC Transmit Power Control

[0127] U2N UE to Network

[0128] U2U UE to UE

[0129] UAI UE assistance information

[0130] UE User Equipment

[0131] UL Uplink

Claims

1. A method comprising: monitoring, by a source user equipment communicating with a destination user equipment via a relay user equipment over an indirect communication path, sidelink control information from the relay user equipment; determining a first set of conditions and a second set of conditions based on the sidelink control information received from the relay user equipment; When the first set of conditions is met, at least one of the following is sent: a first sidelink message to the destination user equipment according to a first mode, or a second sidelink message to the relay user equipment according to the second mode; and When the second set of conditions is met, sidelink feedback from the destination user equipment to the relay user equipment is monitored according to a third mode.

2. The method of claim 1 , wherein determining the first set of conditions and the second set of conditions comprises: Determine whether the side link control information sent by the relay user equipment to the destination user equipment is received according to a configured standard, wherein the configured standard includes whether a received power level on the side link control information from the relay user equipment to the destination user equipment is higher than a first received power threshold.

3. The method of claim 1 , wherein determining the first set of conditions and the second set of conditions comprises: Determining whether the source user equipment receives any side link control information sent by the relay user equipment to the destination user equipment within a configured monitoring time window; or A transmit power level used to perform a sidelink transmission from the source user equipment to the relay user equipment is above a first transmit power threshold.

4. The method of claim 1 , wherein determining the first set of conditions and the second set of conditions comprises: Identify at least one of the following: whether the received power level on the sidelink control information from the relay user equipment to the destination user equipment is higher than a second received power threshold, or Whether a transmission power level used to perform sidelink transmission from the source user equipment to the relay user equipment is higher than a second transmission power threshold.

5. The method of claim 1 , wherein determining the second set of conditions comprises: It is determined whether a hybrid automatic repeat request with feedback is used between the relay user equipment and the destination user equipment.

6. The method according to claim 5, further comprising: When the received power level on the sidelink feedback from the destination user equipment to the relay user equipment is higher than a third received power threshold, a path switching request is initiated to the destination user equipment.

7. The method according to any one of claims 1 to 6, wherein the first side link message comprises a discovery notification, a direct communication request, a keep-alive message or a side link channel state information request, and The first sidelink message is sent directly to the destination user equipment.

8. The method according to any one of claims 1 to 7, wherein the second sidelink message is sidelink control information for sidelink transmission of data from the source user equipment to the relay user equipment, and The data will be relayed to the destination user equipment.

9. The method according to any one of claims 1 to 8, wherein the sidelink feedback is a hybrid automatic repeat request feedback from the destination user equipment to the relay user equipment.

10. The method according to any one of claims 1 to 9, wherein when at least one of the first set of conditions or the second set of conditions is satisfied, the method further comprises: Determining that the destination user equipment is out of the sidelink range of the source user equipment; as well as communicating with the destination user equipment via the relay user equipment through an indirect communication path without performing the sending of at least one of the following: the first sidelink message to the destination user equipment according to the first mode, the second sidelink message to the relay user equipment according to the second mode; or The sidelink feedback from the destination user equipment to the relay user equipment is monitored according to the third mode.

11. The method according to any one of claims 1 to 10, wherein the second sidelink message is sent to the relay user equipment at a maximum allowed transmit power, and The maximum allowed transmit power is an amount of power that is higher than a power level required to send the second sidelink message to the relay user equipment and that is within a predefined power budget.

12. An apparatus comprising: at least one processor; as well as at least one memory including computer program code, The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least: monitoring sidelink control information from the relay user equipment, wherein the apparatus communicates with a destination user equipment via the relay user equipment over an indirect communication path; determining a first set of conditions and a second set of conditions based on the sidelink control information received from the relay user equipment; When the first set of conditions is met, at least one of the following is sent: a first sidelink message to the destination user equipment according to a first mode, or a second sidelink message to the relay user equipment according to the second mode; and When the second set of conditions is met, sidelink feedback from the destination user equipment to the relay user equipment is monitored according to a third mode.

13. The apparatus of claim 12, wherein the determining of the first set of conditions and the second set of conditions comprises: Determine whether the side link control information sent by the relay user equipment to the destination user equipment is received according to a configured standard, wherein the configured standard includes whether a received power level on the side link control information from the relay user equipment to the destination user equipment is higher than a first received power threshold.

14. The apparatus of claim 12, wherein the determining of the first set of conditions and the second set of conditions comprises: determining whether the apparatus receives any sidelink control information sent by the relay user equipment to the destination user equipment within a configured monitoring time window, or A transmit power level used to perform sidelink transmissions from the apparatus to the relay user equipment is above a first transmit power threshold.

15. The apparatus of claim 12, wherein the determining of the first set of conditions and the second set of conditions comprises: Identify at least one of the following: whether the received power level on the sidelink control information from the relay user equipment to the destination user equipment is higher than a second received power threshold, or Whether a transmission power level for performing sidelink transmission from the apparatus to the relay user equipment is higher than a second transmission power threshold.

16. The apparatus according to any one of claims 12 to 15, wherein the determination of the second set of conditions comprises: It is determined whether a hybrid automatic repeat request with feedback is used between the relay user equipment and the destination user equipment.

17. The apparatus of claim 16, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to at least: When the received power level on the sidelink feedback from the destination user equipment to the relay user equipment is higher than a third received power threshold, a path switching request is initiated to the destination user equipment.

18. The device according to any one of claims 12 to 17, wherein the first side link message comprises a discovery notification, a direct communication request, a keep-alive message or a side link channel state information request, and The first sidelink message is sent directly to the destination user equipment.

19. The device according to any one of claims 12 to 18, wherein the second sidelink message is sidelink control information for sidelink transmission of data from the apparatus to the relay user equipment, and The data will be relayed to the destination user equipment.

20. The apparatus according to any one of claims 12 to 19, wherein the sidelink feedback is a hybrid automatic repeat request feedback from the destination user equipment to the relay user equipment.

21. The apparatus of any one of claims 12 to 20, wherein when at least one of the first set of conditions or the second set of conditions is satisfied, the at least one memory and the computer program code are further configured to, together with the at least one processor, cause the apparatus to at least: determining that the destination user equipment is out of sidelink range of the apparatus; and communicating with the destination user equipment via the relay user equipment through an indirect communication path without performing the sending of at least one of the following: the first sidelink message to the destination user equipment according to the first mode, the second sidelink message to the relay user equipment according to the second mode; or The sidelink feedback from the destination user equipment to the relay user equipment is monitored according to the third mode.

22. The device according to any one of claims 12 to 21, wherein the second sidelink message is sent to the relay user equipment at a maximum allowed transmit power, and The maximum allowed transmit power is an amount of power that is higher than a power level required to send the second sidelink message to the relay user equipment and that is within a predefined power budget.

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