PATENT DOCUMENT

Publication Number: US-12156114-B2
Application Number: US-202318494980-A
Country: US
Kind Code: B2

Title: Layer 2 UE to UE data forwarding

Abstract:
Systems and methods for using a relay user equipment (UE) to transport data of interest received from a first remote UE to a second remote UE on a UE to UE relay within a wireless communication system are discussed herein. These methods may be performed at Layer 2 of a protocol stack of the wireless communication system. Data packets sent on the UE to UE relay may include an adaptation header including routing information (e.g., Layer 2 addresses, a bearer-specific index, etc.) for the UE to UE relay. An adaptation layer may accordingly be provided within Layer 2 to decode these adaptation headers. In some cases, a per-bearer approach may be used to map between individual direct bearers of a hop by hop path configuration of the UE to UE relay. Embodiments eschewing the adaptation header and instead using logical channel identifiers (LCIDs) to make routing indications are also described.

Claims:
The invention claimed is: 
     
       1. A method of a relay user equipment (UE) for establishing a hop by hop path configuration, comprising:
 receiving, from a first remote UE, a first sidelink (SL) configuration message corresponding to a first bearer between the first remote UE and relay UE, the first SL configuration message comprising a first logical channel identifier (LCID), an end-to-end bearer ID, a next-hop quality of service (QoS) indicator, and a first index; 
 generating a second SL configuration message corresponding to a second bearer between the relay UE and a second remote UE, the second SL configuration message comprising a second LCID, the end-to-end bearer ID, and a second index; 
 sending, to the second remote UE, the second SL configuration message; 
 receiving, from the second remote UE, a first SL reconfiguration complete message; and 
 sending, to the first remote UE, a second SL reconfiguration complete message. 
 
     
     
       2. The method of  claim 1 , wherein each of the first bearer and the second bearer is a radio link control (RLC) bearer. 
     
     
       3. The method of  claim 1 , wherein the first bearer between the first remote UE and the relay UE is a new bearer, and wherein the first SL configuration message further comprises new bearer configuration information. 
     
     
       4. The method of  claim 1 , wherein the first bearer between the first remote UE and the relay UE is an existing bearer. 
     
     
       5. The method of  claim 1 , wherein the second LCID is selected by the relay UE for use in the second SL configuration message based on the next-hop QoS indicator from the first remote UE. 
     
     
       6. The method of  claim 1 , wherein the end-to-end bearer ID identifies a data radio bearer (DRB). 
     
     
       7. The method of  claim 1 , wherein the end-to-end bearer ID identifies a signaling radio bearer (SRB). 
     
     
       8. A method of a relay user equipment (UE) for establishing a hop by hop path configuration, comprising:
 receiving, from a first remote UE, a first sidelink (SL) configuration message corresponding to a first bearer between the first remote UE and relay UE, the first SL configuration message comprising a first logical channel identifier (LCID) configured to provide a routing indication, an end-to-end bearer ID, and a next-hop quality of service (QoS) indicator; 
 generating a second SL configuration message corresponding to a second bearer between the relay UE and a second remote UE, the second SL configuration message comprising a second LCID configured to provide a routing indication, and the end-to-end bearer ID; 
 sending, to the second remote UE, the second SL configuration message; 
 receiving, from the second remote UE, a first SL reconfiguration complete message; and 
 sending, to the first remote UE, a second SL reconfiguration complete message. 
 
     
     
       9. The method of  claim 8 , wherein the first bearer between the first remote UE and the relay UE is a new bearer, and wherein the first SL configuration message further comprises new bearer configuration information. 
     
     
       10. The method of  claim 8 , wherein each of the first bearer and the second bearer is a radio link control (RLC) bearer. 
     
     
       11. The method of  claim 8 , wherein the second LCID is selected by the relay UE based on the next-hop QoS indicator from the first remote UE. 
     
     
       12. The method of  claim 8 , wherein the end-to-end bearer ID identifies a data radio bearer (DRB). 
     
     
       13. The method of  claim 8 , wherein the end-to-end bearer ID identifies a signaling radio bearer (SRB). 
     
     
       14. An apparatus of a relay user equipment (UE) for establishing a hop by hop path configuration, comprising:
 one or more processors, and 
 a memory storing instructions that, when executed by the one or more processors, configure the relay UE to:
 receive, from a first remote UE, a first sidelink (SL) configuration message corresponding to a first bearer between the first remote UE and relay UE, the first SL configuration message comprising a first logical channel identifier (LCID), an end-to-end bearer ID, a next-hop quality of service (QoS) indicator, and a first index; 
 generate a second SL configuration message corresponding to a second bearer between the relay UE and a second remote UE, the second SL configuration message comprising a second LCID, the end-to-end bearer ID, and a second index; 
 send, to the second remote UE, the second SL configuration message; 
 receive, from the second remote UE, a first SL reconfiguration complete message; and 
 send, to the first remote UE, a second SL reconfiguration complete message. 
 
 
     
     
       15. The apparatus of  claim 14 , wherein each of the first bearer and the second bearer is a radio link control (RLC) bearer. 
     
     
       16. The apparatus of  claim 14 , wherein the first bearer between the first remote UE and the relay UE is a new bearer, and wherein the first SL configuration message further comprises new bearer configuration information. 
     
     
       17. The apparatus of  claim 14 , wherein the first bearer between the first remote UE and the relay UE is an existing bearer. 
     
     
       18. The apparatus of  claim 14 , wherein the second LCID is selected by the relay UE for use in the second SL configuration message based on the next-hop QoS indicator from the first remote UE. 
     
     
       19. The apparatus of  claim 14 , wherein the end-to-end bearer ID identifies a data radio bearer (DRB). 
     
     
       20. The apparatus of  claim 14 , wherein the end-to-end bearer ID identifies a signaling radio bearer (SRB).

Description:
TECHNICAL FIELD 
     This application relates generally to wireless communication systems, including wireless communication systems with one or more user equipment (UE) that can perform UE to UE relay functionalities using Layer 2 methods. 
     BACKGROUND 
     Wireless mobile communication technology uses various standards and protocols to transmit data between a base station and a wireless mobile device. Wireless communication system standards and protocols can include the 3rd Generation Partnership Project (3GPP) long term evolution (LTE) (e.g., 4G) or new radio (NR) (e.g., 5G); the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, which is commonly known to industry groups as worldwide interoperability for microwave access (WiMAX); and the IEEE 802.11 standard for wireless local area networks (WLAN), which is commonly known to industry groups as Wi-Fi. In 3GPP radio access networks (RANs) in LTE systems, the base station can include a RAN Node such as a Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (also commonly denoted as evolved Node B, enhanced Node B, eNodeB, or eNB) and/or Radio Network Controller (RNC) in an E-UTRAN, which communicate with a wireless communication device, known as user equipment (UE). In fifth generation (5G) wireless RANs, RAN Nodes can include a 5G Node, NR node (also referred to as a next generation Node B or g Node B (gNB)). 
     RANs use a radio access technology (RAT) to communicate between the RAN Node and UE. RANs can include global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE) RAN (GERAN), Universal Terrestrial Radio Access Network (UTRAN), and/or E-UTRAN, which provide access to communication services through a core network. Each of the RANs operates according to a specific 3GPP RAT. For example, the GERAN implements GSM and/or EDGE RAT, the UTRAN implements universal mobile telecommunication system (UMTS) RAT or other 3GPP RAT, the E-UTRAN implements LTE RAT, and NG-RAN implements 5G RAT. In certain deployments, the E-UTRAN may also implement 5G RAT. 
     Frequency bands for 5G NR may be separated into two different frequency ranges. Frequency Range 1 (FR1) may include frequency bands operating in sub-6 GHz frequencies, some of which are bands that may be used by previous standards, and may potentially be extended to cover new spectrum offerings from 410 MHz to 7,125 MHz. Frequency Range 2 (FR2) may include frequency bands from 24.25 GHz to 52.6 GHz. Bands in the millimeter wave (mmWave) range of FR2 may have smaller coverage but potentially higher available bandwidth than bands in the FR1. Skilled persons will recognize these frequency ranges, which are provided by way of example, may change from time to time or from region to region. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced. 
         FIG.  1    illustrates a relay UE providing a UE to UE relay, according to an embodiment. 
         FIG.  2    illustrates a setup procedure for setting up a relay UE to provide a UE to UE relay between a first remote UE and a second remote UE, according to an embodiment. 
         FIG.  3    is a diagram illustrating a source remote UE, a relay UE, and a destination remote UE and their various user protocol stacks, according to embodiments herein. 
         FIG.  4    illustrates the sending of a first data packet between a source remote UE and a relay UE according to a UE to UE relay between the source remote UE and a destination remote UE, according to an embodiment. 
         FIG.  5    illustrates the sending of a second data packet between a relay UE and a destination remote UE according to a UE to UE relay between the source remote UE and a destination remote UE, according to an embodiment. 
         FIG.  6    illustrates various possible adaptation headers that may be used according to some embodiments. 
         FIG.  7    illustrates a method for setting up hop by hop path configurations from a source remote UE to a destination remote UE through a relay UE, according to an embodiment. 
         FIG.  8    is a diagram illustrating the use of a data forwarding method according to a per-bearer approach of some embodiments. 
         FIG.  9    illustrates a method for setting up hop by hop path configurations from a source remote UE to a destination remote UE through a relay UE, according to an embodiment. 
         FIG.  10    is a diagram illustrating the use of a data forwarding method according to a per-bearer approach of some embodiments. 
         FIG.  11    illustrates a method of a relay UE, according to an embodiment. 
         FIG.  12    illustrates a method of a relay UE, according to an embodiment. 
         FIG.  13    illustrates a method of a relay UE, according to an embodiment. 
         FIG.  14    illustrates a method of a relay UE for establishing a hop by hop path configuration, according to an embodiment. 
         FIG.  15    illustrates a method of a relay UE for establishing a hop by hop path configuration, according to an embodiment. 
         FIG.  16    illustrates a UE in accordance with one embodiment. 
         FIG.  17    illustrates a network node in accordance with one embodiment. 
         FIG.  18    illustrates an example service based architecture in accordance with certain embodiments. 
         FIG.  19    illustrates components in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A relay UE may be capable of receiving data from one wireless mobile device and transporting it to another wireless mobile device. For example, a relay UE may be capable of receiving data from a first remote UE and transmitting it to a base station (and vice versa, from the base station to the first remote UE). In other words, the relay UE acts as a UE to network (NW) relay between the first remote UE and the base station. In other examples, a relay UE may be capable of receiving data from a first remote UE and transmitting it to a second remote UE (and vice versa, from the second remote UE to the first remote UE). In other words, the relay UE provides a UE to UE relay between the first remote UE and the second remote UE. 
     A UE providing a UE to UE relay may aid the connectivity of users of remote UEs to each other. For example, a relay UE may be helpful to a user of a first remote UE that is out of range of a second remote UE on sidelink (SL). In these cases, data may be communicated from the first remote UE to the relay UE providing a UE to UE relay, and then forwarded to the second remote UE on the UE to UE relay. A relay UE may be analogously used for UE to NW relay applications. In this fashion, communications from the first remote UE may be received by entities in the wireless communication system that are out of direct range of the first remote UE. This may be useful in cases where, for example, one or more various entities (UEs, base stations) of the wireless communication system are widely dispersed, with each entity in range of only one or only a handful (but not all) of the other entities within the wireless communication system. 
     It is contemplated that UE to UE relay functionalities may be implemented in Layer 2 (sometimes referred to herein as “L2”) of a protocol stack of, for example, an NR wireless communication system (among other possible systems, such as, e.g., an LTE wireless communication system, or a hybrid or another wireless communication system). Further, any Layer 2 UE to UE relay functionalities used within a wireless communication system may correspond to/be designed for use with UE to NW relay functionalities within the wireless communication system that are implemented in Layer 2 of a protocol stack. 
     As compared to, for example, Layer 3 approaches, Layer 2 approaches disclosed herein may provide better end-to-end security protection (because the relay UE cannot peek into the data shared between remote UEs in such Layer 2 approaches). Moreover, the Layer 2 approach enables access stratum (AS)-layer mechanisms to ensure quality of service (QoS) and service continuity, which may not be possible using a Layer 3 relaying approach. Further, Layer 2 UE to UE relaying and Layer 2 UE to NW relaying can have a common scalable design which can be extended to support multi-hop relaying. 
     Systems implementing UE to UE relay functionalities may be useful in, for example, public safety cases or Vehicle-to-Everything (V2X) cases, where it is possible that a UE may be out of range of a base station, but within range of one or more (possibly dispersed) other UEs. 
       FIG.  1    illustrates a relay UE  102  providing a UE to UE relay, according to an embodiment. The relay UE  102  may connect to a first remote UE  104  using the first PC5 link  106 . The relay UE  102  may also connect to a second remote UE  108  on a second PC5 link  110 . Data may be sent on one or both of the first PC5 link  106  and/or the second PC5 link  110 . These data transmissions (and other data transmissions on a PC5 link) may be discussed herein as “SL transmissions” or “SL messages”. 
     The relay UE  102  may receive data of interest for the second remote UE  108  as part of one or more data packets from the first remote UE  104  on the first PC5 link  106 . The relay UE  102  may then send this data of interest to the second remote UE  108  as part of one or more data packets on the second PC5 link  110 . 
     The messaging described in relation to  FIG.  1    may be usefully applied in various coverage scenarios. For example, it may be that all three of the relay UE  102 , the first remote UE  104 , and the second remote UE  108  are out of coverage (e.g., not within communication range of a base station of the wireless communication system). In this case, the first PC5 link  106  and the second PC5 link  110  can be used by these devices to enable communications between the first remote UE  104  and the second remote UE  108 . As another example, it may be that only the relay UE  102  is in coverage. In this case, the relay UE  102  may forward data of interest to the second remote UE  108  as described (and this may happen directly via the UE to UE relay, rather than, for example, the relay UE  102  involving a base station by acting as a UE to NW relay). As another example, the relay UE  102  and one of the first remote UE  104  or second remote UE  108  is in coverage, but the other of the first remote UE  104  and the second remote UE  108  is out of coverage. In this case, the relay UE  102  may forward the data of interest from the one of the first remote UE  104  and the second remote UE  108  to the other of the first remote UE  104  and the second remote UE  108  directly (e.g., via the UE to UE relay) rather than involving the base station in the data transmission process, which may require a greater number of transmissions than in the UE to UE relay case. 
     It is anticipated that, in some embodiments, a relay UE that is providing a UE to UE relay could also provide a UE to NW relay. 
       FIG.  2    illustrates a setup procedure  200  for setting up a relay UE  202  to provide a UE to UE relay between a first remote UE  204  and a second remote UE  206 , according to an embodiment. The setup procedure  200  may include performing first PC5 discovery  208 , during which the relay UE  202  and the second remote UE  206  discover that they are within SL range of each other. 
     The setup procedure  200  may further include performing second PC5 discovery  210 , during which the relay UE  202  and the first remote UE  204  discover that they are within SL range of each other. 
     The order of performing the first PC5 discovery  208  and the second PC5 discovery  210  may be reversed. 
     As part of performing the first PC5 discovery  208  and/or the second PC5 discovery  210 , it may be that, for example, the first remote UE  204  discovers that the second remote UE  206  would be reachable by the first remote UE  204  via a UE to UE relay provided by the relay UE  202 , and/or that the second remote UE  206  discovers that the first remote UE  204  would be reachable by the second remote UE  206  via a UE to UE relay provided by the relay UE  202 . 
     The setup procedure  200  may further include performing the first PC5 link setup  212 , during which the relay UE  202  and the second remote UE  206  establish a PC5 link (e.g., for SL communications) between themselves. 
     The setup procedure  200  may further include performing the second PC5 link setup  214 , during which the relay UE  202  and the first remote UE  204  establish a PC5 link (e.g., for SL communications) between themselves. 
     The order of performing the first PC5 link setup  212  and the second PC5 link setup  214  may be reversed. Further, it is contemplated that each of the first PC5 discovery  208  and the first PC5 link setup  212  may both be performed prior to performing either/both of the second PC5 discovery  210  and/or the second PC5 link setup  214 , and/or that each of the second PC5 discovery  210  and the second PC5 link setup  214  may both be performed prior to performing either/both of the first PC5 discovery  208  and/or the first PC5 link setup  212 . 
     The setup procedure  200  further optionally includes performing the hop by hop path configurations  216 . A “hop” may be one (of multiple) direct communications between UEs as part of a UE to UE relay (e.g., SL communications between the first remote UE  204  and the relay UE  202  may be a “hop,” and SL communications between the relay UE  202  and the second remote UE  206  may be a “hop”). As will be described in further detail below, hop by hop path configurations  216  may be useful in cases where an adaptation header either does not carry, e.g., Layer 2 address(es) (sometimes referred to herein as “Layer 2 IDs” or “L2 IDs”) in one or more data packets sent along a UE to UE relay, and/or where an adaptation header is not used at all in one or more data packets sent along a UE to UE relay. These hop by hop path configurations  216  may configure (or reconfigure) one or more (per-hop) direct bearers that are identified by the logical channel identifier (LCID) used in a data packet using the hop and/or data found in an adaptation header of a data packet using the hop. This may be the case for all hops between endpoints (e.g., in the case of  FIG.  2   , all hops between the first remote UE  204  and the second remote UE  206 ). 
     The setup procedure  200  may further include performing an end-to-end PC5 link setup (control plane)  218 , where one or more end-to-end bearers are established between the endpoints (e.g., between the first remote UE  204  and the second remote UE  206 ). These end-to-end bearers may include or comprise bearers corresponding to single “hops” as discussed above. These end-to-end bearers may include SL signaling radio bearers (SRBs) and/or SL data radio bearers (DRBs). These end-to-end bearers may be set up using end-to-end PC5 signaling (PC5-S) procedures and/or end-to-end PC5 radio resource control (PC5-RRC) procedures. Each end-to-end bearer may have an ID that is unique as to other end-to-end bearers between its same pair of UE endpoints (but perhaps not unique globally within the wireless communication system). 
     The end-to-end PC5 link setup (control plane)  218  may not be performable until intermediate relay UEs (e.g., the relay UE  202 ) are ready to conduct forwarding of data that is not terminated locally at the respective relay UE. It is for this reason that, in some embodiments, the hop by hop path configurations  216  are performed. For example, in embodiments that use per-bearer reservation systems, the hop by hop path configurations  216  may be necessary (as opposed to embodiments using per-packet configurations, where all required routing information is conveyed in user plane headers (e.g., adaptation headers) in each data packet and thus the hop by hop path configurations  216  may not be necessary). 
     The setup procedure  200  further includes end-to-end data transport (user plane)  220 . This end-to-end data transport (user plane)  220  may involve the transmission of data between end points and through relay UEs (e.g., the transmission of data between the first remote UE  204  and the second remote UE  206  via the relay UE  202 ), in the manner described above. This transport may involve end-to-end transport using SL DRBs via a relay UE, established in the manner described above. 
       FIG.  3    is a diagram  300  illustrating a source remote UE  302 , a relay UE  304 , and a destination remote UE  306  and their various user protocol stacks, according to embodiments herein. As described herein, a “source remote UE” may be a UE that initiates the UE to UE relay of data to a “destination remote UE.” Correspondingly, the “destination remote UE” may be a UE that is the intended destination for such a data packet. 
     A user protocol stack according to embodiments here may include one or more of a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, an adaptation layer, and a packet data convergence protocol (PDCP) layer. As shown, an outgoing user protocol stack  308  of the source remote UE  302  according to embodiments here may be a include the PHY layer  310 , the MAC layer  312 , the RLC layer  314 , the adaptation layer  316 , and the PDCP layer  318 . Further, the relay UE  304  may include the incoming user protocol stack  320 , with the PHY layer  322 , the MAC layer  324 , the RLC layer  326 , and the adaptation layer  328  and the outgoing user protocol stack  330  with the PHY layer  332 , the MAC layer  334 , the RLC layer  336 , and the adaptation layer  338 . Finally, the destination remote UE  306  may include the incoming user protocol stack  340  with the PHY layer  342 , the MAC layer  344 , the RLC layer  346 , the adaptation layer  348 , and the PDCP layer  350 . 
     Each of a PHY layer, a MAC layer, an RLC layer, and a PDCP layer may be as these layers are understood by persons of ordinary skill in the art of relevant wireless communication systems (e.g., NR and/or LTE wireless communication systems). 
     An adaptation layer may be used to help a relay UE to make forwarding decisions as part of a Layer 2 forwarding process described herein. An adaptation header may be placed within a radio link control (RLC) protocol data unit (PDU) of a first data packet. The decoding of this adaptation header may occur at the adaptation layer. By decoding this adaptation header, the adaptation layer of an incoming user protocol stack may be enabled to identify bearers and/or next hops according to UE to UE relay embodiments. Further, an adaptation layer of an outgoing user protocol stack may be responsible for encoding corresponding information into an adaptation header of a second data packet that is to be sent according to a UE to UE relay functionality. 
     As illustrated relative to the relay UE  304  a UE (including, e.g., the source remote UE  302 , the relay UE  304 , and/or the destination remote UE  306 ) may use multiple instances of such a user plane protocol stack, with some being used corresponding to incoming data packets and others being used corresponding to outgoing data packets. For example, some of these instances, such as the incoming user protocol stack  320  and the incoming user protocol stack  340 , may be for decoding received data packets, while other instances, such as the outgoing user protocol stack  308  and the outgoing user protocol stack  330 , are used for encoding data packets to be sent. 
     UE to UE relay transmissions according to embodiments herein that use Layer 2 transmissions may use PDCP bearers as end-to-end bearers. These end-to-end PDCP bearers may include DRBs and SRBs. As illustrated, a transmission from the source remote UE  302  through the relay UE  304  and to the destination remote UE  306  according to a UE to UE relay transmission may use, e.g., a PDCP bearer  352  as an end-to-end bearer. 
     The PDCP bearer  352  may comprise each of a first RLC bearer  354  that travels from the source remote UE  302  to the relay UE  304  and the second RLC bearer  356  that travels from the destination remote relay UE  304  to the PHY layer  310 . The first RLC bearer  354  and the second RLC bearer  356  may be examples of direct bearers as described herein. 
     Although the diagram  300  has been illustrated and described from the perspective of a source remote UE  302  sending data on a UE to UE relay via the relay UE  304  to a destination remote UE  306 , it is contemplated that in many cases any of the UEs would be capable of performing the functions of any of the source remote UE  302 , the relay UE  304 , and/or the destination remote UE  306 . Further, while only a single relay UE has been illustrated in the diagram  300 , it is contemplated that analogous principles would apply as described herein to extend a UE to UE relay to use any number of relay UEs. 
       FIG.  4    illustrates the sending of a first data packet  402  between a source remote UE  302  and a relay UE  304  according to a UE to UE relay between the source remote UE  302  and a destination remote UE  306 , according to an embodiment. The source remote UE  302 , the relay UE  304 , and the destination remote UE  306  (and the PDCP bearer  352 , the first RLC bearer  354 , and the second RLC bearer  356 ) may be those discussed above in relation to  FIG.  3   . 
     The first data packet  402  may include, among other things, a source UE Layer 2 address  404 . The source UE Layer 2 address  404  may indicate a Layer 2 address of the source remote UE  302 . The first data packet  402  may further include a destination UE Layer 2 address  406 . The destination UE Layer 2 address  406  may indicate a Layer 2 address of the relay UE  304 . 
     The first data packet  402  may further include a MAC PDU payload  408 , which may include one or more MAC subheaders (such as the MAC subheader  410 ) and one or more RLC PDUs (such as the RLC PDU  412 ). 
     The MAC subheader  410  may include an LCID  414 . The LCID  414  may be used to indicate QoS information to the relay UE  304 . For example, if the LCID  414  is of a certain value understood by the relay UE  304 , the relay UE  304  may treat the first data packet  402  with a certain QoS priority or treatment. In some embodiments, the LCID  414  may also include a routing indication that is used by the relay UE  304  to determine the identity of the destination remote UE  306  for routing purposes, as will be discussed in further detail below. It is contemplated that other MAC subheaders of the MAC PDU payload  408  could have analogous contents. 
     The RLC PDU  412  may be the portion of the packet that is conceptually “sent” on the first RLC bearer  354 . The RLC PDU  412  may be decoded at, for example, the RLC layer  326  of the relay UE  304 . 
     The RLC PDU  412  may include an RLC header  416 . 
     Further, the RLC PDU  412  may include an adaptation header  418 . The adaptation header  418  may include routing information that is useful to the relay UE  304  in determining the manner of forwarding data taken from the first data packet  402  to the destination remote UE  306 . For example, the adaptation header  418  may include an identity of an end-to-end bearer (e.g., the PDCP bearer  352 ) between the source remote UE  302  and the destination remote UE  306 . Additionally or alternatively, the adaptation header  418  may include a Layer 2 address for the source remote UE  302 . Additionally or alternatively, the adaptation header  418  may include a Layer 2 address of the destination remote UE  306 . Additionally or alternatively, the adaptation header  418  may include QoS information corresponding to the first data packet. Additionally or alternatively, the adaptation header  418  may include an index (sometimes referred to herein as a “local index”) that can be used by the relay UE  304  to determine a bearer between the relay UE  304  and the destination remote UE  306  to use to forward data to the destination remote UE  306 . The use of each of these types of routing information will be discussed in additional detail below. As will be discussed below, the adaptation header  418  may not be used in some embodiments herein when certain types of routing indications are possible in an LCID. 
     The RLC PDU  412  may further include a PDCP PDU  420 . The PDCP PDU  420  may be the portion of the packet that is conceptually “sent” on the PDCP bearer  352 . As illustrated, the PDCP PDU  420  may not be decoded at the relay UE  304  (because the relay UE  304  is not the ultimate destination of the PDCP PDU  420 ). 
     The PDCP PDU  420  may be or include the data of interest that is driving the use of the UE to UE relay provided by the relay UE  304  and that was determined (e.g., by the source remote UE  302 ) to be delivered from the source remote UE  302  to the destination remote UE  306  according to the UE to UE relay provided between these devices by the relay UE  304 . Accordingly, and as will be shown in relation to  FIG.  5   , the PDCP PDU  420  may be forwarded by the relay UE  304  to the destination remote UE  306 . 
       FIG.  5    illustrates the sending of a second data packet  502  between a relay UE  304  and a destination remote UE  306  according to a UE to UE relay between the source remote UE  302  and a destination remote UE  306 , according to an embodiment. The source remote UE  302 , the relay UE  304 , and the destination remote UE  306  (and the PDCP bearer  352 , the first RLC bearer  354 , and the second RLC bearer  356 ) may be those discussed above in relation to  FIG.  3   . 
     The second data packet  502  may include, among other things, a source UE Layer 2 address  504 . The source UE Layer 2 address  504  may indicate a Layer 2 address of the relay UE  304 . The second data packet  502  may further include a destination UE Layer 2 address  506 . The destination UE Layer 2 address  506  may indicate a Layer 2 address of the destination remote UE  306 . 
     The second data packet  502  may further include a MAC PDU payload  508 , which may include one or more MAC subheaders (such as a MAC subheader  510 ) and one or more RLC PDUs (such as an RLC PDU  512 ). 
     The MAC subheader  510  may include an LCID  514 . The LCID  514  may be of a value that indicates to the destination remote UE  306  that it is the ultimate destination for, e.g., the PDCP PDU  420  included in the second data packet  502 . 
     The RLC PDU  512  may be the portion of the packet that is conceptually “sent” on the second RLC bearer  356 . The RLC PDU  512  may be decoded at, for example, the RLC layer  346  of the destination remote UE  306 . 
     The RLC PDU  512  main include an RLC header  516 . 
     Further, the RLC PDU  512  may include an adaptation header  518 . The adaptation header  518  may include routing information that is useful to the destination remote UE  306  in determining that it is the ultimate destination for, for example, the PDCP PDU  420  included in the second data packet  502 . This will be discussed in further detail below. As will also be discussed, the adaptation header  518  may not be used in some embodiments herein when certain types of routing indications are possible in an LCID. 
     The RLC PDU  512  may further include the PDCP PDU  420  (e.g., the same PDCP PDU introduced in relation to  FIG.  4   ). The PDCP PDU  420  may be the portion of the packet that is conceptually “sent” on the PDCP bearer  352 . As discussed above, the PDCP PDU  420  may be or include the data of interest that is driving the use of the UE to UE relay provided by the relay UE  304  and that was determined (e.g., by the source remote UE  302 ) to be delivered from the source remote UE  302  to the destination remote UE  306  according to the UE to UE relay established between these devices by the relay UE  304 . Because the destination remote UE  306  is the intended destination remote UE, the PDCP PDU  420  may be decoded at the PDCP layer  520  of the destination remote UE  306 . 
     Solutions discussed herein may use the adaptation headers introduced above as included in one or more data packets that enable (in some cases, in conjunction with other information from the data packet, such as information found in an LCID of the data packet) to perform the illustrated UE to UE relay functionalities. Further solutions may eschew the adaptation header entirely and may be configured to make one or more routing indications in, for example, an LCID that are used for routing purposes. Any of these solutions may act to provide a way for a source UE to inform a relay UE to where (e.g., to which remote UE) to forward a data packet. In some embodiments, the usage of LCID to distinguish traffic to be forwarded to the (final) destination remote UE from the traffic to be passed up to the local PDCP entity can be avoided. For example, an adaptation header containing routing information may use one designated index value to label the packets which are to be processed locally. Alternatively or additionally, the adaptation header may include a destination remote UE layer 2 address of the traffic. In these kind of embodiments, the LCID may not indicate routing information, whereas the adaptation header is always used by the first remote UE for any outgoing traffic to guide the relay UEs which receive those traffic about how to process it. 
     A first approach may leverage per-packet configurations by explicitly placing one or more Layer 2 addresses in an adaption header. Under this approach, the UE may use PC5 QoS Identifier (PQI) to SL radio bearer (SLRB) mapping to classify traffic into different logical channels. In some cases, separate LCID values (even if corresponding to a same QoS priority or treatment) may be used to distinguish traffic terminated at the relay UE as opposed to traffic meant to be forwarded by a relay UE on a UE to UE relay provided by the relay UE. 
     Under the first approach, the adaptation header may be used to indicate both QoS information and, in many cases, a relay destination. The relay destination may be the Layer 2 address of the eventual destination remote UE. 
     The QoS information may be, for example, end-to-end QoS information or remaining QoS information. End-to-end QoS information may indicate that certain data on a given end-to-end bearer of the UE to UE relay is to be treated with a certain (static) QoS priority or treatment at each hop. Remaining QoS information may be a total of remaining (unused) time left to deliver data to the destination remote UE, and may be updated at each hop of the UE to UE relay based on the amount of time it took to make the hop. 
       FIG.  6    illustrates various possible adaptation headers  600  that may be used according to some embodiments. The possible adaptation headers  600  may be used as part of the first approach. The possible adaptation headers  600  include a first hop adaptation header format  602 . The first hop adaptation header format  602  may be sent to a relay UE from a source remote UE (or a prior relay UE) in a data packet that contains data that is to be forwarded by the relay UE. The first hop adaptation header format  602  includes a Layer 2 destination address field  608 , an end-to-end bearer ID field  610 , and a QoS information field  612 , each of which may be an example of routing information as discussed herein. A relay UE that receives the first hop adaptation header format  602  may use the Layer 2 destination address field  608  and the end-to-end bearer ID field  610  to identify how to forward data of interest (e.g., a PDCP PDU) from a received data packet according to the UE to UE relay on a corresponding outgoing data packet. Further, the relay UE may use the QoS information field  612  to identify with what QoS to send the corresponding outgoing data packet. In some embodiments, when the relay UE receives traffic from a prior relay UE, the first-hop adaptation header may include a Layer 2 address of the source remote UE. In some embodiments, when the relay UE receives traffic from a source remote UE, the first-hop adaptation header may include a Layer 2 source address of the source remote UE, so that this information can be handily retrieved by the adaptation layer (instead of being retrieved from the MAC header). 
     The possible adaptation headers  600  include a second hop adaptation header format  604 . The second hop adaptation header format  604  may be sent to a destination remote UE from a relay UE in a data packet that contains data of interest (e.g., data in a PDCP PDU of the data packet) that is to be used at the destination remote UE. The second hop adaptation header format  604  includes a Layer 2 source address field  614  and an end-to-end bearer ID field  616 , each of which may be an example of routing information as discussed herein. The Layer 2 source address field  614  and the end-to-end bearer ID field  616  may be used by the destination remote UE to identify the UE from which the data of interest to be used from the data packet originated. A Layer 2 destination address and/or QoS information field may not be necessary in this case, as the data of interest has arrived at its destination. As discussed above, an LCID may be used by the destination remote UE to determine that the received data is for use at the destination remote UE (and not to be further relayed). Alternatively, another version of the second hop adaptation header format  604  may include the Layer 2 destination address field (with the Layer 2 address of the destination remote UE) that may then be used by the destination remote UE to determine that the data received is for use at the destination remote UE (and not to be further relayed). 
     The possible adaptation headers  600  include a unified adaptation header format  606 . In some embodiments, it may be determined to be more straightforward to use a format according to the unified adaptation header format  606  in every data packet used in the UE to UE relay (rather than differentiate between, e.g., the use cases of the first hop adaptation header format  602  and the second hop adaptation header format  604 ). Accordingly, the unified adaptation header format  606  includes all of the previously discussed fields of the possible adaptation headers  600  in an adaptation header, including a Layer 2 source address field  618 , a Layer 2 destination address field  620 , an end-to-end bearer ID field  622 , and a QoS information field  624  (each of which may be an example of routing information as discussed herein), each used (as necessary) at each UE of the UE to UE relay. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Destination 
                 Forwarding Interface 
               
               
                   
               
             
            
               
                 No adaptation 
                 Pass to PCDP layer of the relay UE 
               
               
                 header 
               
               
                 L2 Dst ID = L2 ID 
                 Pass to PCDP layer of the relay UE 
               
               
                 of relay UE 
               
               
                 L2 Dst ID = L2 ID 
                 Find corresponding PC5 link using Layer 2 address 
               
               
                 of destination 
                 of destination remote UE and the end-to-end bearer 
               
               
                 remote UE 
                 ID, form necessary adaptation header, and forward 
               
               
                 end-to-end bearer 
                 data in a new packet using the necessary adaptation 
               
               
                 ID = x 
                 header along the UE to UE relay 
               
               
                   
               
            
           
         
       
     
     Table 1 illustrates the functionalities of a relay UE according to the first approach just described. If no adaptation header is included in a packet received at the relay UE, the relay UE determines that it was the ultimate destination of the data of interest (e.g., a PDCP PDU), and passes the data packet containing this data through to a PDCP layer of the relay UE for decoding and further use. In other cases, if the adaptation header includes a Layer 2 destination address field and the value in that field is a Layer 2 address of the relay UE, the relay UE determines that it was the ultimate destination of the data of interest (e.g., a PDCP PDU), and passes the data packet containing this data through to a PDCP layer of the relay UE for decoding and further use. 
     In other cases, if the adaptation header includes a Layer 2 destination address field and the value in that field is an address of a destination remote UE, the relay UE may then use the address of the destination remote UE and a bearer ID value from an end-to-end bearer ID field to determine a PC5 link to forward the data of interest toward the destination remote UE in a data packet that also includes an appropriate adaptation header (with appropriate routing information, as described above) that the relay UE forms for this purpose. 
     Note that because a pair of UEs may communicate using more than one end-to-end bearer, and because end-to-end bearer IDs may not be global IDs (but instead may be understood as an ID that may be unique only as between a given pair of UEs) it may be necessary to include both the end-to-end bearer ID field and a Layer 2 address for one of the UEs in order to make a complete forwarding determination as described above. 
     It is contemplated that the adaptation headers of the first approach could be used in embodiments involving more than one relay UE. In that case, an adaptation header of a first hop adaptation header format  602  may be sent by each relay UE (except a last relay UE, which may then send an adaptation header of a second hop adaptation header format  604 ). In other such embodiments, an adaptation header of the unified adaptation header format  606  may be used in every case. Further, QoS information (e.g., remaining QoS information) may need to be updated to account for each hop, in the manner described above. 
     A second approach may be a per-bearer approach that leverages implicit indications according to pre-established hop by hop path configurations. As introduced above, in order to use such a per-bearer implicit approach, it may be necessary to first establish the hop by hop path configurations. The establishment of the hop by hop path configurations may correspond to performing the hop by hop path configurations  216  discussed above in relation to  FIG.  2   . 
     It may be that using such an implicit, per-bearer approach according to hop by hop path configurations may reduce the amount of data (and therefore processing resources needed to interpret and/or use such data) in an adaptation header as compared to methods using the one or more of the possible adaptation headers  600  according to the first approach. For example, in the second approach, the adaptation header may contain only an index value, as opposed to the (perhaps larger and multiple) values discussed in adaptation headers according to the first approach (e.g., the possible adaptation headers  600 ). 
     A UE may need to send data in one or more data packets along a UE to UE relay, and those data packets may need to be sent according to a certain LCID (which may represent the QoS priority or treatment of the packet). Each UE may review its current direct bearers (e.g., DRBs) with the next UE in the UE to UE relay and determine whether a new direct bearer needs to be established (either because there is not a direct bearer between the UEs currently established, or because the direct bearers that are established between the UEs do not have an appropriate LCID to meet the QoS priority or treatment for the data in question), or whether a current direct bearer will suffice for that hop of the UE to UE relay for that data. 
       FIG.  7    illustrates a method  700  for setting up hop by hop path configurations from a source remote UE  702  to a destination remote UE  706  through a relay UE  704 , according to an embodiment. The method  700  includes performing a first PC5 link setup  708  and a second PC5 link setup  710 . This may be done in the manner described above in relation to, for example, performing the first PC5 link setup  212  and second PC5 link setup  214  of  FIG.  2   . 
     The method  700  further includes sending a message  712  between the source remote UE  702  and the relay UE  704 . The message  712  may be an SL configuration message such as a “SidelinkReconfig” message or some other message configured to carry the illustrated parameters. The parameters of the message  712  may include an SLRB-config, which may indicate new bearer configuration information regarding a newly set up (by the source remote UE  702 ) direct bearer between the source remote UE  702  and the relay UE  704 . This parameter may be optional, in that it may only be present if a new such direct bearer is being established (rather than an already existing direct bearer between the source remote UE  702  and the relay UE  704  being reused, as described above) for use according to this hop by hop path configuration. The parameters of the message  712  further include an LCID, which corresponds to the QoS priority or treatment with which data will be sent by the source remote UE  702  on this bearer, and may further be used (as described below) for identifying data to this hop by hop path configuration. The message  712  further includes a destination address parameter, which indicates to the relay UE  704  the ultimate destination (e.g., the destination remote UE) of data sent according to this hop by hop path configuration (e.g., using a Layer 2 address of the ultimate destination). The message  712  further includes an end-to-end bearer ID that indicates to the relay UE  704  the end-to-end bearer that corresponds to this hop by hop path configuration. The message  712  further includes a next-hop QoS, which allows the relay UE  704  to determine the QoS priority or treatment that should be given to data sent according to this hop by hop path configuration on a next hop. The next-hop QoS included in the message  712  may be an explicit indication of the QoS priority or treatment that should be given such data. Alternatively, the next-hop QoS included in the message  712  may be an indication of a general (static) QoS priority or treatment that should be used for all data on this hop by hop path configuration. Finally, the message  712  may further include an index that may be used to uniquely identify the hop between the source remote UE  702  and the relay UE  704  within this hop by hop path configuration. In other words, the index uniquely identifies the use of this direct bearer as within this particular hop by hop path configuration (as opposed to, e.g., the use of the same direct bearer as within a different hop by hop path configuration). 
     The method  700  further includes recording  714 , at the relay UE  704 , the end-to-end bearer ID corresponding to this hop by hop path configuration received in the message  712 . The method  700  further includes recording  716 , at the relay UE  704 , next-hop QoS requirement corresponding to the next hop of this hop by hop path configuration received in the message  712 . 
     The method  700  further includes checking  718  any existing LCIDs of direct bearers between the relay UE  704  and the destination remote UE  706  to see whether such bearers meet the next-hop QoS requirements for the hop of this hop by hop path configuration between the relay UE  704  and the destination remote UE  706 . 
     The method  700  further includes sending a message  720  between the relay UE  704  and the destination remote UE  706 . The message  720  may be a sidelink configuration message such as a “SidelinkReconfig” message or some other message configured to carry the illustrated parameters. The parameters of the message  720  may include an SLRB-config, which may indicate new bearer configuration information regarding a newly set up (by the relay UE  704 ) bearer between the relay UE  704  and the relay destination remote UE  706 . This parameter may be optional, in that it may only be present if a new such bearer is being established for use according to this hop by hop path configuration (rather than, for example, the case where the relay UE  704  instead decides to re-use an existing direct bearer between the relay UE  704  and the destination remote UE  706  in the case that an LCID of the existing direct bearer met the next-hop QoS requirement for this hop of the hop by hop path configuration, which the relay UE  704  checked as described above in checking  718 ). The parameters of the message  720  further include an LCID, which corresponds to the QoS priority or treatment with which data will be sent by the relay UE  704  on this bearer, and will further be used (as described below) for identifying data to this hop by hop path configuration. This LCID may be selected based on the next-hop QoS indicator received from the source remote UE  702 . The message  720  further includes a destination address parameter, which indicates to the destination remote UE  706  the ultimate destination of data sent according to this hop by hop path configuration (e.g., using a Layer 2 address of the ultimate destination of the data, which may be a Layer 2 address of the destination remote UE  706 ). The message  720  further includes an end-to-end bearer ID that indicates to the relay destination remote UE  706  the end-to-end bearer that corresponds to this hop by hop path configuration. This end-to-end bearer ID is the same end-to-end bearer ID that was sent to the relay UE  704  by the source remote UE  702 . The message  720  further includes a next-hop QoS, which allows the destination remote UE  706  to determine the QoS priority or treatment that should be given to data sent according to this hop by hop path configuration on a next hop (in the case that the relay UE  704  does not realize that the destination remote UE  706  is the destination, but note that including this information would also be of use in the case where the relay UE  704  is instead setting up a hop by hop path configuration with another relay UE rather than the destination remote UE  706 ). The next-hop QoS included in the message  720  may be an explicit indication of the QoS priority or treatment that should be given such data. Alternatively, the next-hop QoS included in the message  720  may be an indication of a general (static) QoS priority or treatment that should be used for all data on this hop by hop path configuration. Finally, the message  720  may further include an index that may be used to uniquely identify the hop between the relay UE  704  and the destination remote UE  706  within this hop by hop path configuration. In other words, the index uniquely identifies the use of this direct bearer as within this particular hop by hop path configuration (as opposed to, e.g., the use of the same direct bearer as within a different hop by hop path configuration). Because this index is local to the direct bearer of the relay UE  704  and the destination remote UE  706 , the value of the index between the source remote UE  702  and the relay UE  704  has no bearing on its value. 
     To confirm the portion of the hop by hop path configuration between the relay UE  704  and destination remote UE  706  that uses this direct bearer between the relay UE  704  and the destination remote UE  706 , the destination remote UE  706  sends an SL reconfiguration complete message  722  such as a “SidelinkReconfigComplete” message, or some other message. The message  722  may include the index identifying the hop of the hop by hop path configuration between the relay UE  704  and the destination remote UE  706 . 
     Then, to confirm the setup of the portion of the hop by hop path configuration between the source remote UE  702  and the relay UE  704  that uses the (other) direct bearer between the source remote UE  702  and the relay UE  704 , the relay UE  704  sends an SL reconfiguration complete message  724  such as a “SidelinkReconfigComplete” message, or some other message. The message  724  may include the (other) index identifying the hop of the hop by hop path configuration between the source remote UE  702  and the relay UE  704 . 
     The method  700  further includes storing  726 , at the relay UE  704 , the correspondence or mapping between the indexes (e.g., storing information that each of the indexes discussed above is part of the same hop by hop path configuration); storing the relationships between each index and its corresponding LCID; storing a mapping between the Layer 2 address of the source remote UE  702  and the Layer 2 address of the destination remote UE  706  corresponding to this hop by hop path configuration; storing the end-to-end bearer ID corresponding to this hop by hop path configuration; and storing QoS information regarding one or both of the hops of this hop by hop path configuration. 
     The method  700  then proceeds to perform a PC5 secure link establishment (end-to-end)  728 , which may correspond to the end-to-end PC5 link setup (control plane)  218  of  FIG.  2   . 
     It is contemplated that the method  700  could be extended to include multiple relay UEs (more than just the relay UE  704 ). In these instances, each relay UE may receive a message analogous to the message  712  from a prior UE in the UE to UE relay; perform operations analogous to the recording  714 , the recording  716 , and the checking  718 ; send a message analogous to the message  720  to the next UE in the UE to UE relay; receive a message analogous to the message  722  from the next UE in the UE to UE relay; send a message analogous to the message  724  back to the prior UE in the UE to UE relay; and perform the operations analogous to the storing  726 . 
     It is further contemplated that analogous information as was sent in the message  712  and the message  720  can be sent in return on the message  722  and the message  724  (e.g., an SL configuration message such as the illustrated “SidelinkReconfig” messages of the message  712  and the message  720  can be sent on the message  722  and the message  724 , perhaps with additional confirmatory signaling then added to the method  700 ). This may allow for the configuration of a second hop by hop path configuration that is the reverse of the first using only a single messaging method. For example, in the method  700  illustrated in  FIG.  7   , the support of data forwarding setup is for the directional end-to-end PDCP bearer from source remote UE  702  to the destination remote UE  706 . If there is another directional bearer from the destination remote UE  706  to the source remote UE  702 , then an analogous set of configuration parameters can be included in the “SidelinkReconfigComplete” message or any other sort of message used for similar purposes. Then, with a single round-trip, a data forwarding setup can be achieved for traffic in both directions between the source remote UE  702  and the destination remote UE  706 . 
     It is also further contemplated that multiple hop by hop path configurations may be achieved in one messaging round trip by including duplicates of the discussed information (relative to each individual hop by hop path configuration) in each of the message  712 , the message  720 , the message  722 , and the message  724 . For example, if there are multiple end-to-end PDCP bearers to be set up from the source remote UE  702  to the destination remote UE  706 , an array of configurations, one for each of the multiple PDCP bearers, can be included in the “SidelinkReconfig” message or any other sort of messages used for similar purposes. 
     Once a hop by hop path configuration as described above is set up, a per-bearer, implicit approach for UE to UE relay may be accomplished. In this approach, the LCID value placed in a data packet may be used to distinguish data packets terminated at the receiving UE and any data packets to be forwarded on to, for example, a destination remote UE or another relay UE. This means that there may be multiple usable LCID values for a single QoS priority or treatment, one of which is used to indicate a data packet terminated at the receiving UE, and another of which is used to indicate that a data packet is to be forwarded along the UE to UE relay. Under this approach, a UE may use PQI to SLRB mapping to classify traffic into different logical channels. 
     The index value for the particular hop being used in the particular the hop by hop path configuration being used is placed into an adaptation header of the data packet to be sent. 
     Once received at the receiving UE, the LCID value, the index value, and a Layer 2 source address of the sending UE (from, e.g., the MAC header, as in the source UE Layer 2 address  404  of  FIG.  4    and the source UE Layer 2 address  504  of  FIG.  5   ) are used at each receiving UE on the UE to UE relay (whether it be a relay UE or a destination remote UE) to determine the necessary forwarding configuration (or not) for the data of interest in the received data packet. 
       FIG.  8    is a diagram  800  illustrating the use of a data forwarding method according to a per-bearer approach of some embodiments. The diagram  800  includes a first remote UE  802  (labeled as “UE  1 ” in  FIG.  8   ), a relay UE  804  (labeled as “UE  2 ” in  FIG.  8   ), a second remote UE  806  (labeled as “UE  3 ” in  FIG.  8   ), and a third remote UE  808  (labeled as “UE  4 ” in  FIG.  8   ). A first hop by hop path configuration  810  has been established between the first remote UE  802  and the relay UE  804 . A second hop by hop path configuration  812  has been established between the first remote UE  802  and the second remote UE  806 . A third hop by hop path configuration  814  has been established between the first remote UE  802  and the second remote UE  806 . A fourth hop by hop path configuration  816  has been established between the third remote UE  808  and the second remote UE  806 . Each of these hop by hop path configurations may have been established using the methods disclosed in relation to  FIG.  7    above. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Ingress 
                 Egress 
               
               
                   
               
             
            
               
                 L2 Src ID = UE 1, LCID = 0 
                 N/A, pass up to PDCP of UE 2 
               
               
                 L2 Src ID = UE 1, LCID = 1, index = 1 
                 L2 Dst ID = UE 3, LCID = 1, index = 5 
               
               
                 L2 Src ID = UE 1, LCID = 2, index = 2 
                 L2 Dst ID = UE 3, LCID = 1, index = 6 
               
               
                 L2 Src ID = UE 4, LCID = 4, index = 1 
                 L2 Dst ID = UE 3, LCID = 3, index = 1 
               
               
                   
               
            
           
         
       
     
     Table 2 illustrates the ingress and egress treatment of data of interest in a data packet received at the relay UE  804 . For example, if a data packet is received with a certain LCID indicating the data is not to be forwarded (e.g., LCID=0), the data of interest is decoded by the PDCP layer of the relay UE  804 . This is the first row of Table 2 as applied to the first hop by hop path configuration  810  of  FIG.  8   . 
     In other cases, a data packet may be received at the relay UE  804  with an LCID that indicates that the data of interest should be forwarded (e.g., LCID 0), and an index in an adaptation header that corresponds to the particular hop of the particular hop by hop path configuration that was used to send the data packet. The relay UE  804  may then refer to the index and LCID that was saved during the setup of the particular hop by hop path configuration to identify the hop by hop path configuration that corresponds to the received data packet, and to further determine that the data of interest from the data packet should be packaged into another (outgoing) data packet and sent on a next hop (according to its corresponding index) of the particular hop by hop path configuration. Accordingly, the relay UE  804  may generate a data packet containing the data of interest that contains an LCID and an index value in an adaptation header that corresponds to the next hop in the particular hop by hop path configuration as was determined during the hop by hop path configuration setup. This data packet is then sent by the relay UE  804  on the direct bearer corresponding to that particular hop of the particular hop by hop path configuration. 
     For example, as in the second row of Table 2, the relay UE  804  may receive a data packet from the first remote UE  802  with LCID=1 and index (from the adaptation header)=1. This may correspond to an incoming hop of the second hop by hop path configuration  812  that maps to an outgoing hop of the second hop by hop path configuration  812  that uses a mapped-to direct bearer with an LCID of 1 and an index (in the adaptation header) of 5 to send the data of interest to the second remote UE  806 . Accordingly, the relay UE  804  prepares a corresponding data packet, places within it the data of interest, and forwards it to the second remote UE  806  on the mapped-to direct bearer. 
     As another example, as in the third row of Table 2, the relay UE  804  may receive a data packet from the first remote UE  802  with LCID=2 and index (from the adaptation header)=2. This may correspond to an incoming hop of the third hop by hop path configuration  814  that maps to an outgoing hop of the third hop by hop path configuration  814  that uses a mapped-to direct bearer with an LCID of 1 and an index (in the adaptation header) of 5 to send the data of interest to the second remote UE  806 . Accordingly, the relay UE  804  prepares a corresponding data packet, places within it the data of interest, and forwards it to the second remote UE  806  on the mapped-to direct bearer. 
     As another example, as in the fourth row of Table 2, the relay UE  804  may receive a data packet from the third remote UE  808  with LCID=4 and index (from the adaptation header)=1. This may correspond to an incoming hop of the fourth hop by hop path configuration  816  that maps to an outgoing hop of the fourth hop by hop path configuration  816  that uses a mapped-to direct bearer with an LCID of 3 and an index (in the adaptation header) of 1 to send the data of interest to the second remote UE  806 . Accordingly, the relay UE  804  prepares a corresponding data packet, places within it the data of interest, and forwards it to the second remote UE  806  on the mapped-to direct bearer. 
     It is contemplated that embodiments according to this second approach could be extended to include devices other than UEs, such as base stations (in which case the method would be considered to function in a UE to NW relay context). 
     A third approach may also be a per-bearer approach that leverages implicit indications according to pre-established hop by hop path configurations. The third approach may be different than the second approach, in that in at least some circumstances, it may be that there is a wide enough range of LCID values available for use that an LCID value can itself be configured to provide a routing indication (without interfering with the necessary communication of QoS information in the LCID values within the wireless communication system). This may be the case when there are not too many UEs involved in UE to UE relay operations within the wireless communication system. In this case, an index may not be required (as an LCID value can make an analogous indication), and so an adaptation header may not be required and may be omitted, granting even further gains to signaling efficiency. 
     A UE may need to send data in one or more data packets along a UE to UE relay, and those data packets may need to be sent according to a certain LCID (which may represent the QoS priority or treatment of the packet). Each UE may review its current direct bearers (e.g., DRBs) with the next UE in the UE to UE relay and determine whether a new direct bearer needs to be established (either because there is not a direct bearer established, or because the direct bearers that are established do not have an appropriate LCID to meet the QoS priority or treatment for the data in question), or whether a current direct bearer will suffice for that hop of the UE to UE relay for that data. 
       FIG.  9    illustrates a method  900  for setting up hop by hop path configurations from a source remote UE  902  to a destination remote UE  906  through a relay UE  904 , according to an embodiment. The method  900  includes performing a first PC5 link setup  908  and a second PC5 link setup  910 . This may be done in the manner described above in relation to, for example, performing the first PC5 link setup  212  and the second PC5 link setup  214  of  FIG.  2   . 
     The method  900  further includes sending a message  912  between the source remote UE  902  and the relay UE  904 . The message  912  may be an SL configuration message such as a “SidelinkReconfig” message or some other message configured to carry the illustrated parameters. The parameters of the message  912  may include an SLRB-config, which may indicate new bearer configuration information regarding a newly set up (by the source remote UE  902 ) direct bearer between the source remote UE  902  and the relay UE  904 . This parameter may be optional, in that it may only be present if a new such direct bearer is being established (rather than an already existing direct bearer between the source remote UE  902  and the relay UE  904  being reused, as described above) for use according to this hop by hop path configuration. The parameters of the message  912  further include an LCID, which corresponds to the QoS priority or treatment with which data will be sent by the source remote UE  902  on this direct bearer. The LCID may also provide (e.g., represent, due to the particular value of LCID selected) a routing indication used to instruct the relay UE  904  sufficiently to identify the next direct bearer of the corresponding hop by hop path configuration. The message  912  further includes a destination address parameter, which indicates to the relay UE  904  the ultimate destination (e.g., the destination remote UE) of data sent according to this hop by hop path configuration (e.g., using a Layer 2 address of the ultimate destination). The message  912  further includes an end-to-end bearer ID that indicates to the relay UE  904  the end-to-end bearer that corresponds to this hop by hop path configuration. The message  912  further includes a next-hop QoS, which allows the relay UE  904  to determine the QoS priority or treatment that should be given to data sent according to this hop by hop path configuration on a next hop. The next-hop QoS included in the message  912  may be an explicit indication of the QoS priority or treatment that should be given such data. Alternatively, the next-hop QoS included in the message  912  may be an indication of a general (static) QoS priority or treatment that should be used for all data on this hop by hop path configuration. 
     The method  900  further includes recording  914 , at the relay UE  904 , the end-to-end bearer ID corresponding to this hop by hop path configuration received in the message  912 . The method  900  further includes recording  916 , at the relay UE  904 , the LCID corresponding to the previous hop of the hop by hop path configuration received in the message  912 . The method  900  further includes recording  918 , at the relay UE  904 , a next-hop QoS requirement corresponding to the next hop of this hop by hop path configuration received in the message  912 . The method  900  further includes picking a new LCID for the next-hop that meets the next-hop QoS requirement (and, if necessary, a new SLRB configuration for a direct bearer for the next hop that meets this LCID, if such a direct bearer between the relay UE  904  and the destination remote UE  906  does not already exist; otherwise, an existing direct bearer that meets this LCID may be used instead). 
     The method  900  further includes sending a message  922  between the relay UE  904  and the destination remote UE  906 . The message  922  may be a sidelink configuration message such as a “SidelinkReconfig” message or some other message configured to carry the illustrated parameters. The parameters of the message  922  may include an SLRB-config, which may indicate new bearer configuration information regarding a newly set up (by the relay UE  904 ) bearer between the relay UE  904  and the destination remote UE  906 . This parameter may be optional, in that it may only be present if a new such direct bearer is being established for use according to this hop by hop path configuration (rather than, for example, the case where the relay UE  904  instead decides to re-use an existing direct bearer between the relay UE  904  and the destination remote UE  906  in the case that an LCID of the existing direct bearer met the next-hop QoS requirement for this hop of the hop by hop path configuration, which the relay UE  904  checked as described above in picking  920 ). The parameters of the message picking  920  further include an LCID, which corresponds to the QoS priority or treatment with which data will be sent by the relay UE  704  on this bearer. This LCID may be selected based on the next-hop QoS indicator received from the source remote UE  902 . The LCID may also provide (e.g., represent, due to the particular value of LCID selected) a routing indication used to instruct the destination remote UE  906  sufficiently to identify data to this hop by hop path configuration. The message  922  further includes a destination address parameter, which indicates to the destination remote UE  906  the ultimate destination of data sent according to this hop by hop path configuration (e.g., using a Layer 2 address of the ultimate destination of the data, which may be a Layer 2 address of the destination remote UE  906 ). The message  922  further includes an end-to-end bearer ID that indicates to the destination remote UE  906  the end-to-end bearer that corresponds to this hop by hop path configuration. This end-to-end bearer ID is the same end-to-end bearer ID that was sent to the relay UE  904  by the source remote UE  902 . The message  912  further includes a next-hop QoS, which allows the relay UE  904  to determine the QoS priority or treatment that should be given to data sent according to this hop by hop path configuration on a next hop (in the case that the relay UE  904  does not realize that the destination remote UE  906  is the destination, but note that this information would also be of use in the case where the relay UE  904  is instead setting up a hop by hop path configuration with another relay UE rather than the destination remote UE  906 ). The next-hop QoS included in the message  912  may be an explicit indication of the QoS priority or treatment that should be given such data. Alternatively, the next-hop QoS included in the message  912  may be an indication of a general (static) QoS priority or treatment that should be used for all data on this hop by hop path configuration. 
     To confirm the portion of the hop by hop path configuration between the relay UE  904  and destination remote UE  906  that uses this direct bearer between the relay UE  904  and the destination remote UE  906 , the destination remote UE  906  sends an SL reconfiguration complete message  924  such as a “SidelinkReconfigComplete” message, or some other message. 
     Then, to confirm the setup of the portion of the hop by hop path configuration between the source remote UE  902  and the relay UE  904  that uses the (other) direct bearer between the source remote UE  902  and the relay UE  904 , the relay UE  904  sends an SL reconfiguration complete message  926  such as a “SidelinkReconfigComplete” message, or some other message. 
     The method  900  further includes maintaining  928 , at the relay UE  904 , the correspondence or mapping between LCID pairs, storing a mapping between the Layer 2 address of the source remote UE  902  and the Layer 2 address of the destination remote UE  906  corresponding to this hop by hop path configuration, storing the end-to-end bearer ID corresponding to this hop by hop path configuration, and storing QoS information regarding one or both of the hops of this hop by hop path configuration. 
     The method  900  then proceeds to perform a PC5 secure link establishment (end-to-end)  930 , which may correspond to the end-to-end PC5 link setup (control plane)  218  of  FIG.  2   . 
     It is contemplated that the method  900  could be extended to include multiple relay UEs (more than just the relay UE  904 ). In these instances, each relay UE may receive a message analogous to the message  912  from a prior UE in the UE to UE relay; perform operations analogous to the recording  914 , the recording  916 , the recording  918 , and the picking  920 ; send a message analogous to the message  922  to the next UE in the UE to UE relay; receive a message analogous to the message  924  from the next UE in the UE to UE relay; and send a message analogous to the message  926  back to the prior UE in the UE to UE relay, and perform the operations analogous to the maintaining  928 . 
     It is further contemplated that analogous information as was sent in the message  912  and the recording message  922  can be sent in return on the message  924  and the message  926  (e.g., an SL configuration message such as the illustrated “SidelinkReconfig” messages of the message  912  and the message  922  can be sent on the message  924  and the message  926 , perhaps with additional confirmatory signaling then added to the method  900 ). This may allow for the configuration of a second hop by hop path configuration that is the reverse of the first using only a single messaging method. 
     It is also further contemplated that multiple hop by hop path configurations may be achieved in one messaging round trip by including duplicates of the discussed information (relative to each individual hop by hop path configuration) in each of the message  912 , the message  922 , the message  924 , and the message  926 . 
     Once a hop by hop path configuration as described above is set up, a per-bearer, implicit approach for UE to UE relay may be accomplished. In this approach, the LCID value within received data packets may provide a routing indication that may be used distinguish a data packet terminated at the receiving UE and any data packets to be forwarded on to, for example, a destination remote UE or another relay UE. Such a routing indication under the third approach may also distinguish a direct bearer to use on a next hop of a hop by hop path configuration. 
     Once received at the receiving UE, the LCID value and a Layer 2 source address of the sending UE (from, e.g., the MAC header, as in the source UE Layer 2 address  404  of  FIG.  4    and the source UE Layer 2 address  504  of  FIG.  5   ) are used at each receiving UE on the UE to UE relay (whether it be a relay UE or a destination remote UE) to determine the necessary forwarding configuration (or not) for the data of interest in the received data packet. 
       FIG.  10    is a diagram  1000  illustrating the use of a data forwarding method according to a per-bearer approach of some embodiments. The diagram  1000  includes a first remote UE  1002  (labeled as “UE  1 ” in  FIG.  10   ), a relay UE  1004  (labeled as “UE  2 ” in  FIG.  10   ), a second remote UE  1006  (labeled as “UE  3 ” in  FIG.  10   ), a third remote UE  1008  (labeled as “UE  4 ” in  FIG.  10   ), and a fourth remote UE  1010  (labeled as “UE  5 ” in  FIG.  10   ). A first hop by hop path configuration  1012  has been established between the first remote UE  1002  and the relay UE  1004 . A second hop by hop path configuration  1014  has been established between the first remote UE  1002  and the second remote UE  1006 . A third hop by hop path configuration  1016  has been established between the third remote UE  1008  and the second remote UE  1006 . A fourth hop by hop path configuration  1018  has been established between the first remote UE  1002  and the fourth remote UE  1010 . Each of these hop by hop path configurations may have been established using the methods disclosed in relation to  FIG.  9    above. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Ingress 
                 Egress 
               
               
                   
                   
               
             
            
               
                   
                 L2 Src ID = UE 1, LCID = 0 
                 N/A, pass up to PDCP of UE 2 
               
               
                   
                 L2 Src ID = UE 1, LCID = x 
                 L2 Dst ID = UE 3, LCID = y 
               
               
                   
                 L2 Src ID = UE 4, LCID = p 
                 L2 Dst ID = UE 3, LCID = q 
               
               
                   
                 L2 Src ID = UE 1, LCID = u 
                 L2 Dst ID = UE 5, LCID = v 
               
               
                   
                   
               
            
           
         
       
     
     Table 2 illustrates the ingress and egress treatment of data of interest in a data packet received at the relay UE  1004 . For example, if a data packet is received with an LCID that provides a routing indication that the data of interest is not to be forwarded (e.g., LCID=0), the data of interest is decoded by the PDCP layer of the relay UE  1004 . This is the first row of Table 2 as applied to the first hop by hop path configuration diagram  1000  of  FIG.  10   . 
     In other cases, a data packet may be received at the relay UE  1004  with an LCID that provides a routing indication that necessitates the forwarding of the data of interest in the data packet. The relay UE  1004  may then refer to the LCID that was saved during the setup of the particular hop by hop path configuration to identify the hop by hop path configuration that corresponds to the received data packet, and to further determine that the data of interest from the data packet should be packaged into another (outgoing) data packet and sent on a next hop of the particular hop by hop path configuration. Accordingly, the relay UE  1004  may generate a data packet containing the data of interest that contains an LCID that corresponds to the next hop in the particular hop by hop path configuration as was determined during setup. This data packet is then sent by the relay UE  1004  on the bearer corresponding to that particular hop of the particular hop by hop path configuration. 
     For example, as in the second row of Table 2, the relay UE  1004  may receive a data packet from the first remote UE  1002  with LCID=x. This may correspond to an incoming hop of the second hop by hop path configuration  1014  that maps to an outgoing hop of the second hop by hop path configuration  1014  that uses a mapped-to direct bearer with an LCID of y to send the data of interest to the second remote UE  1006 . Accordingly, the relay UE  1004  prepares a corresponding data packet, places within it the data of interest, and forwards it to the second remote UE  1006  on the mapped-to direct bearer. 
     As another example, as in the third row of Table 2, the relay UE  1004  may receive a data packet from the third remote UE  1008  with LCID=p. This may correspond to an incoming hop of the third hop by hop path configuration  1016  that maps to an outgoing hop of the third hop by hop path configuration  1016  that uses a mapped-to direct bearer with an LCID of q to send the data of interest to the second remote UE  1006 . Accordingly, the relay UE  1004  prepares a corresponding data packet, places within it the data of interest, and forwards it to the second remote UE  1006  on the mapped-to direct bearer. 
     As another example, as in the fourth row of Table 2, the relay UE  1004  may receive a data packet from the first remote UE  1002  with LCID=u. This may correspond to an incoming hop of the fourth hop by hop path configuration  1018  that maps to an outgoing hop of the fourth hop by hop path configuration  1018  that uses a mapped-to direct bearer with an LCID of i to send the data of interest to the fourth remote UE  1010 . Accordingly, the relay UE  1004  prepares a corresponding data packet, places within it the data of interest, and forwards it to the fourth remote UE  1010  on the mapped-to direct bearer. 
     It is contemplated that embodiments according to this third approach could be extended to include devices other than UEs, such as base stations (in which case the method would be considered to function in a UE to NW relay context). 
       FIG.  11    illustrates a method  1100  of a relay UE, according to an embodiment. The method  1100  includes receiving  1102 , from a first remote UE, a data packet comprising an RLC PDU comprising a PDCP PDU and a first adaptation header having first routing information. 
     The method  1100  further includes decoding  1104  the first routing information from the first adaptation header at an adaptation layer of the relay UE that is between an RLC layer of the UE and a PDCP layer of the UE. 
     The method  1100  further includes determining  1106 , based on the first routing information, that the PDCP PDU should be forwarded to a second remote UE. 
     The method  1100  further includes generating  1108  a second packet comprising the PDCP PDU. 
     The method  1100  further includes forwarding the second packet to the second remote UE. 
       FIG.  12    illustrates a method  1200  of a relay UE, according to an embodiment. The method  1200  includes receiving  1202 , from a first remote UE, a data packet comprising an LCID and an RLC PDU comprising a PDCP PDU and a first adaptation header having first routing information. 
     The method  1200  further includes decoding  1204  the first routing information from the first adaptation header at an adaptation layer of the relay UE that is between an RLC layer of the UE and a PDCP layer of the UE. 
     The method  1200  further includes determining  1206 , based on the LCID and the first routing information, that the PDCP PDU should be forwarded to a second remote UE. 
     The method  1200  further includes generating  1208  a second packet comprising the PDCP PDU. 
     The method  1200  further includes identifying  1210 , based on an index located in the first routing information, a bearer between the relay UE and the second remote UE to use to forward the PDCP PDU to the second remote UE; wherein the second packet is forwarded to the second remote UE using the bearer. 
     The method  1200  further includes forwarding  1212  the second packet to the second remote UE. 
       FIG.  13    illustrates a method  1300  of a relay UE, according to an embodiment. The method  1300  includes receiving  1302 , from a first remote UE, a data packet comprising a MAC header, an LCID comprising a routing indication, and an RLC PDU comprising a PDCP PDU. 
     The method  1300  further includes determining  1304 , based on the routing indication of the LCID and a Layer 2 address provided in the MAC header, that the PDCP PDU should be forwarded to the second remote UE. 
     The method  1300  further includes generating  1306  a second packet comprising the PDCP PDU. 
     The method  1300  further includes identifying  1308 , based on the routing indication in the LCID, a bearer between the relay UE and the second remote UE to use to forward the PDCP PDU to the second remote UE; wherein the second packet is forwarded to the second remote UE using the bearer. 
     The method  1300  further includes forwarding  1310  the second packet to the second remote UE. 
       FIG.  14    illustrates a method  1400  of a relay UE for establishing a hop by hop path configuration, according to an embodiment. The method  1400  includes receiving  1402 , from a first remote UE, a first SL configuration message corresponding to a first bearer between the first remote UE and relay UE, the first SL configuration message comprising a first LCID, a first Layer 2 address, an end-to-end bearer ID, a next-hop QoS indicator, and a first index. 
     The method  1400  further includes generating  1404  a second SL configuration message corresponding to a second bearer between the relay UE and a second remote UE, the second SL configuration message comprising a second LCID, a second Layer 2 address, the end-to-end bearer ID, and a second index. 
     The method  1400  further includes sending  1406 , to the second remote UE, the second SL configuration message. 
     The method  1400  further includes receiving  1408 , from the second remote UE, a first SL reconfiguration complete message comprising the second index. 
     The method  1400  further includes sending  1410 , to the first remote UE, a second SL reconfiguration complete message comprising the first index. 
       FIG.  15    illustrates a method  1500  of a relay UE for establishing a hop by hop path configuration, according to an embodiment. The method  1500  includes receiving  1502 , from a first remote UE, a first SL configuration message corresponding to a first bearer between the first remote UE and relay UE, the first SL configuration message comprising a first LCID configured to provide a routing indication, a first Layer 2 address, an end-to-end bearer ID, and a next-hop QoS indicator. 
     The method  1500  further includes generating  1504  a second SL configuration message corresponding to a second bearer between the relay UE and a second remote UE, the second SL configuration message comprising a second LCID configured to provide a routing indication, a second Layer 2 address, and the end-to-end bearer ID. 
     The method  1500  further includes sending  1506 , to the second remote UE, the second SL configuration message. 
     The method  1500  further includes receiving  1508 , from the second remote UE, a first SL reconfiguration complete message. 
     The method  1500  further includes sending  1510 , to the first remote UE, a second SL reconfiguration complete message. 
       FIG.  16    is a block diagram of an example UE  1600  configurable according to various embodiments of the present disclosure, including by execution of instructions on a computer-readable medium that correspond to any of the example methods and/or procedures described herein. The UE  1600  comprises one or more processor  1602 , transceiver  1604 , memory  1606 , user interface  1608 , and control interface  1610 . 
     The one or more processor  1602  may include, for example, an application processor, an audio digital signal processor, a central processing unit, and/or one or more baseband processors. Each of the one or more processor  1602  may include internal memory and/or may include interface(s) to communicate with external memory (including the memory  1606 ). The internal or external memory can store software code, programs, and/or instructions for execution by the one or more processor  1602  to configure and/or facilitate the UE  1600  to perform various operations, including operations described herein. For example, execution of the instructions can configure the UE  1600  to communicate using one or more wired or wireless communication protocols, including one or more wireless communication protocols standardized by 3GPP such as those commonly known as 5G/NR, LTE, LTE-A, UMTS, HSPA, GSM, GPRS, EDGE, etc., or any other current or future protocols that can be utilized in conjunction with the one or more transceiver  1604 , user interface  1608 , and/or control interface  1610 . As another example, the one or more processor  1602  may execute program code stored in the memory  1606  or other memory that corresponds to MAC, RLC, PDCP, and RRC layer protocols standardized by 3GPP (e.g., for NR and/or LTE). As a further example, the processor  1602  may execute program code stored in the memory  1606  or other memory that, together with the one or more transceiver  1604 , implements corresponding PHY layer protocols, such as Orthogonal Frequency Division Multiplexing (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), and Single-Carrier Frequency Division Multiple Access (SC-FDMA). 
     The memory  1606  may comprise memory area for the one or more processor  1602  to store variables used in protocols, configuration, control, and other functions of the UE  1600 , including operations corresponding to, or comprising, any of the example methods and/or procedures described herein. Moreover, the memory  1606  may comprise non-volatile memory (e.g., flash memory), volatile memory (e.g., static or dynamic RAM), or a combination thereof. Furthermore, the memory  1606  may interface with a memory slot by which removable memory cards in one or more formats (e.g., SD Card, Memory Stick, Compact Flash, etc.) can be inserted and removed. 
     The one or more transceiver  1604  may include radio-frequency transmitter and/or receiver circuitry that facilitates the UE  1600  to communicate with other equipment supporting like wireless communication standards and/or protocols. For example, the one or more transceiver  1604  may include switches, mixer circuitry, amplifier circuitry, filter circuitry, and synthesizer circuitry. Such RF circuitry may include a receive signal path with circuitry to down-convert RF signals received from a front-end module (FEM) and provide baseband signals to a baseband processor of the one or more processor  1602 . The RF circuitry may also include a transmit signal path that may include circuitry to up-convert baseband signals provided by a baseband processor and provide RF output signals to the FEM for transmission. The FEM may include a receive signal path that may include circuitry configured to operate on RF signals received from one or more antennas, amplify the received signals, and provide the amplified versions of the received signals to the RF circuitry for further processing. The FEM may also include a transmit signal path that may include circuitry configured to amplify signals for transmission provided by the RF circuitry for transmission by one or more antennas. In various embodiments, the amplification through the transmit or receive signal paths may be done solely in the RF circuitry, solely in the FEM, or in both the RF circuitry and the FEM circuitry. In some embodiments, the FEM circuitry may include a TX/RX switch to switch between transmit mode and receive mode operation. 
     In some exemplary embodiments, the one or more transceiver  1604  includes a transmitter and a receiver that enable UE  1600  to communicate with various 5G/NR networks according to various protocols and/or methods proposed for standardization by 3 GPP and/or other standards bodies. For example, such functionality can operate cooperatively with the one or more processor  1602  to implement a PHY layer based on OFDM, OFDMA, and/or SC-FDMA technologies, such as described herein with respect to other figures. 
     The user interface  1608  may take various forms depending on particular embodiments, or can be absent from the UE  1600 . In some embodiments, the user interface  1608  includes a microphone, a loudspeaker, slidable buttons, depressible buttons, a display, a touchscreen display, a mechanical or virtual keypad, a mechanical or virtual keyboard, and/or any other user-interface features commonly found on mobile phones. In other embodiments, the UE  1600  may comprise a tablet computing device including a larger touchscreen display. In such embodiments, one or more of the mechanical features of the user interface  1608  may be replaced by comparable or functionally equivalent virtual user interface features (e.g., virtual keypad, virtual buttons, etc.) implemented using the touchscreen display, as familiar to persons of ordinary skill in the art. In other embodiments, the UE  1600  may be a digital computing device, such as a laptop computer, desktop computer, workstation, etc. that comprises a mechanical keyboard that can be integrated, detached, or detachable depending on the particular exemplary embodiment. Such a digital computing device can also comprise a touch screen display. Many example embodiments of the UE  1600  having a touch screen display are capable of receiving user inputs, such as inputs related to exemplary methods and/or procedures described herein or otherwise known to persons of ordinary skill in the art. 
     In some exemplary embodiments of the present disclosure, the UE  1600  may include an orientation sensor, which can be used in various ways by features and functions of the UE  1600 . For example, the UE  1600  can use outputs of the orientation sensor to determine when a user has changed the physical orientation of the UE  1600 &#39;s touch screen display. An indication signal from the orientation sensor can be available to any application program executing on the UE  1600 , such that an application program can change the orientation of a screen display (e.g., from portrait to landscape) automatically when the indication signal indicates an approximate 90-degree change in physical orientation of the device. In this manner, the application program can maintain the screen display in a manner that is readable by the user, regardless of the physical orientation of the device. In addition, the output of the orientation sensor can be used in conjunction with various exemplary embodiments of the present disclosure. 
     The control interface  1610  may take various forms depending on particular embodiments. For example, the control interface  1610  may include an RS-232 interface, an RS-485 interface, a USB interface, an HDMI interface, a Bluetooth interface, an IEEE (“Firewire”) interface, an I 2 C interface, a PCMCIA interface, or the like. In some exemplary embodiments of the present disclosure, the control interface  1660  can comprise an IEEE 802.3 Ethernet interface such as described above. In some embodiments of the present disclosure, the control interface  1610  may include analog interface circuitry including, for example, one or more digital-to-analog (D/A) and/or analog-to-digital (A/D) converters. 
     Persons of ordinary skill in the art can recognize the above list of features, interfaces, and radio-frequency communication standards is merely exemplary, and not limiting to the scope of the present disclosure. In other words, the UE  1600  may include more functionality than is shown in  FIG.  16    including, for example, a video and/or still-image camera, microphone, media player and/or recorder, etc. Moreover, the one or more transceiver  1604  may include circuitry for communication using additional radio-frequency communication standards including Bluetooth, GPS, and/or others. Moreover, the one or more processor  1602  may execute software code stored in the memory  1606  to control such additional functionality. For example, directional velocity and/or position estimates output from a GPS receiver can be available to any application program executing on the UE  1600 , including various exemplary methods and/or computer-readable media according to various exemplary embodiments of the present disclosure. 
       FIG.  17    is a block diagram of an example network node  1700  configurable according to various embodiments of the present disclosure, including by execution of instructions on a computer-readable medium that correspond to any of the example methods and/or procedures described herein. 
     The network node  1700  includes a one or more processor  1702 , a radio network interface  1704 , a memory  1706 , a core network interface  1708 , and other interfaces  1710 . The network node  1700  may comprise, for example, a base station, an eNB, a gNB, an access node, or a component thereof. 
     The one or more processor  1702  may include any type of processor or processing circuitry and may be configured to perform any of the methods or procedures disclosed herein. The memory  1706  may store software code, programs, and/or instructions executed by the one or more processor  1702  to configure the network node  1700  to perform various operations, including operations described herein. For example, execution of such stored instructions can configure the network node  1700  to communicate with one or more other devices using protocols according to various embodiments of the present disclosure, including one or more methods and/or procedures discussed above. Furthermore, execution of such stored instructions can also configure and/or facilitate the network node  1700  to communicate with one or more other devices using other protocols or protocol layers, such as one or more of the PHY, MAC, RLC, PDCP, and RRC layer protocols standardized by 3GPP for LTE, LTE-A, and/or NR, or any other higher-layer protocols utilized in conjunction with the radio network interface  1704  and the core network interface  1708 . By way of example and without limitation, the core network interface  1708  comprises an S1 interface and the radio network interface  1704  may comprise a Uu interface, as standardized by 3GPP. The memory  1706  may also store variables used in protocols, configuration, control, and other functions of the network node  1700 . As such, the memory  1706  may comprise non-volatile memory (e.g., flash memory, hard disk, etc.), volatile memory (e.g., static or dynamic RAM), network-based (e.g., “cloud”) storage, or a combination thereof. 
     The radio network interface  1704  may include transmitters, receivers, signal processors, ASICs, antennas, beamforming units, and other circuitry that enables network node  1700  to communicate with other equipment such as, in some embodiments, a plurality of compatible UE. In some embodiments, the network node  1700  may include various protocols or protocol layers, such as the PHY, MAC, RLC, PDCP, and RRC layer protocols standardized by 3GPP for LTE, LTE-A, and/or 5G/NR. According to further embodiments of the present disclosure, the radio network interface  1704  may include a PHY layer based on OFDM, OFDMA, and/or SC-FDMA technologies. In some embodiments, the functionality of such a PHY layer can be provided cooperatively by the radio network interface  1704  and the one or more processor  1702 . 
     The core network interface  1708  may include transmitters, receivers, and other circuitry that enables the network node  1700  to communicate with other equipment in a core network such as, in some embodiments, circuit-switched (CS) and/or packet-switched Core (PS) networks. In some embodiments, the core network interface  1708  may include the S1 interface standardized by 3GPP. In some embodiments, the core network interface  1708  may include one or more interfaces to one or more SGWs, MMEs, SGSNs, GGSNs, and other physical devices that comprise functionality found in GERAN, UTRAN, E-UTRAN, and CDMA2000 core networks that are known to persons of ordinary skill in the art. In some embodiments, these one or more interfaces may be multiplexed together on a single physical interface. In some embodiments, lower layers of the core network interface  1708  may include one or more of asynchronous transfer mode (ATM), Internet Protocol (IP)-over-Ethernet, SDH over optical fiber, T1/E1/PDH over a copper wire, microwave radio, or other wired or wireless transmission technologies known to those of ordinary skill in the art. 
     The other interfaces  1710  may include transmitters, receivers, and other circuitry that enables the network node  1700  to communicate with external networks, computers, databases, and the like for purposes of operations, administration, and maintenance of the network node  1700  or other network equipment operably connected thereto. 
     Example System Architecture 
     In certain embodiments, 5G System architecture supports data connectivity and services enabling deployments to use techniques such as Network Function Virtualization and Software Defined Networking. The 5G System architecture may leverage service-based interactions between Control Plane Network Functions. Separating User Plane functions from the Control Plane functions allows independent scalability, evolution, and flexible deployments (e.g., centralized location or distributed (remote) location). Modularized function design allows for function re-use and may enable flexible and efficient network slicing. A Network Function and its Network Function Services may interact with another NF and its Network Function Services directly or indirectly via a Service Communication Proxy. Another intermediate function may help route Control Plane messages. The architecture minimizes dependencies between the AN and the CN. The architecture may include a converged core network with a common AN-CN interface that integrates different Access Types (e.g., 3GPP access and non-3GPP access). The architecture may also support a unified authentication framework, stateless NFs where the compute resource is decoupled from the storage resource, capability exposure, concurrent access to local and centralized services (to support low latency services and access to local data networks, User Plane functions can be deployed close to the AN), and/or roaming with both Home routed traffic as well as Local breakout traffic in the visited PLMN. 
     The 5G architecture may be defined as service-based and the interaction between network functions may include a service-based representation, where network functions (e.g., AMF) within the Control Plane enable other authorized network functions to access their services. The service-based representation may also include point-to-point reference points. A reference point representation may also be used to show the interactions between the NF services in the network functions described by point-to-point reference point (e.g., N11) between any two network functions (e.g., AMF and SMF). 
       FIG.  18    illustrates a service based architecture  1800  in 5GS according to one embodiment. As described in 3GPP TS 23.501, the service based architecture  1800  comprises NFs such as an NSSF  1808 , a NEF  1810 , an NRF  1814 , a PCF  1812 , a UDM  1826 , an AUSF  1818 , an AMF  1820 , and an SMF  1822 , for communication with a UE  1816 , a (R)AN  1806 , a UPF  1802 , and a DN  1804 . The NFs and NF services can communicate directly, referred to as Direct Communication, or indirectly via a SCP  1824 , referred to as Indirect Communication.  FIG.  18    also shows corresponding service-based interfaces including Nutm, Naf, Nudm, Npcf, Nsmf, Nnrf, Namf, Nnef, Nnssf, and Nausf, as well as reference points N1, N2, N3, N4, and N6. A few example functions provided by the NFs shown in  FIG.  18    are described below. 
     The NSSF  1808  supports functionality such as: selecting the set of Network Slice instances serving the UE; determining the Allowed NSSAI and, if needed, mapping to the Subscribed S-NSSAIs; determining the Configured NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs; and/or determining the AMF Set to be used to serve the UE, or, based on configuration, a list of candidate AMF(s), possibly by querying the NRF. 
     The NEF  1810  supports exposure of capabilities and events. NF capabilities and events may be securely exposed by the NEF  1810  (e.g., for 3rd party, Application Functions, and/or Edge Computing). The NEF  1810  may store/retrieve information as structured data using a standardized interface (Nudr) to a UDR. The NEF  1810  may also secure provision of information from an external application to a 3GPP network and may provide for the Application Functions to securely provide information to the 3GPP network (e.g., expected UE behavior, 5GLAN group information, and service specific information), wherein the NEF  1810  may authenticate and authorize and assist in throttling the Application Functions. The NEF  1810  may provide translation of internal-external information by translating between information exchanged with the AF  1828  and information exchanged with the internal network function. For example, the NEF  1810  translates between an AF-Service-Identifier and internal 5G Core information such as DNN and S-NSSAI. The NEF  1810  may handle masking of network and user sensitive information to external AF&#39;s according to the network policy. The NEF  1810  may receive information from other network functions (based on exposed capabilities of other network functions), and stores the received information as structured data using a standardized interface to a UDR. The stored information can be accessed and re-exposed by the NEF  1810  to other network functions and Application Functions, and used for other purposes such as analytics. For external exposure of services related to specific UE(s), the NEF  1810  may reside in the HPLMN. Depending on operator agreements, the NEF  1810  in the HPLMN may have interface(s) with NF(s) in the VPLMN. When a UE is capable of switching between EPC and 5GC, an SCEF+NEF may be used for service exposure. 
     The NRF  1814  supports service discovery function by receiving an NF Discovery Request from an NF instance or SCP and providing the information of the discovered NF instances to the NF instance or SCP. The NRF  1814  may also support P-CSCF discovery (specialized case of AF discovery by SMF), maintain the NF profile of available NF instances and their supported services, and/or notify about newly registered/updated/deregistered NF instances along with its NF services to the subscribed NF service consumer or SCP. In the context of Network Slicing, based on network implementation, multiple NRFs can be deployed at different levels such as a PLMN level (the NRF is configured with information for the whole PLMN), a shared-slice level (the NRF is configured with information belonging to a set of Network Slices), and/or a slice-specific level (the NRF is configured with information belonging to an S-NSSAI). In the context of roaming, multiple NRFs may be deployed in the different networks, wherein the NRF(s) in the Visited PLMN (known as the vNRF) are configured with information for the visited PLMN, and wherein the NRF(s) in the Home PLMN (known as the hNRF) are configured with information for the home PLMN, referenced by the vNRF via an N27 interface. 
     The PCF  1812  supports a unified policy framework to govern network behavior. The PCF  1812  provides policy rules to Control Plane function(s) to enforce them. The PCF  1812  accesses subscription information relevant for policy decisions in a Unified Data Repository (UDR). The PCF  1812  may access the UDR located in the same PLMN as the PCF. 
     The UDM  1826  supports generation of 3GPP AKA Authentication Credentials, User Identification Handling (e.g., storage and management of SUPI for each subscriber in the 5G system), de-concealment of a privacy-protected subscription identifier (SUCI), access authorization based on subscription data (e.g., roaming restrictions), UE&#39;s Serving NF Registration Management (e.g., storing serving AMF for UE, storing serving SMF for UE&#39;s PDU Session), service/session continuity (e.g., by keeping SMF/DNN assignment of ongoing sessions, MT-SMS delivery, Lawful Intercept Functionality (especially in outbound roaming cases where a UDM is the only point of contact for LI), subscription management, SMS management, 5GLAN group management handling, and/or external parameter provisioning (Expected UE Behavior parameters or Network Configuration parameters). To provide such functionality, the UDM  1826  uses subscription data (including authentication data) that may be stored in a UDR, in which case a UDM implements the application logic and may not require an internal user data storage and several different UDMs may serve the same user in different transactions. The UDM  1826  may be located in the HPLMN of the subscribers it serves, and may access the information of the UDR located in the same PLMN. 
     The AUSF  1818  supports authentication for 3GPP access and untrusted non-3GPP access. The AUSF  1818  may also provide support for Network Slice-Specific Authentication and Authorization. 
     The AMF  1820  supports termination of RAN CP interface (N2), termination of NAS (N1) for NAS ciphering and integrity protection, registration management, connection management, reachability management, Mobility Management, lawful intercept (for AMF events and interface to LI System), transport for SM messages between UE and SMF, transparent proxy for routing SM messages, Access Authentication, Access Authorization, transport for SMS messages between UE and SMSF, SEAF, Location Services management for regulatory services, transport for Location Services messages between UE and LMF as well as between RAN and LMF, EPS Bearer ID allocation for interworking with EPS, UE mobility event notification, Control Plane CIoT 5GS Optimization, User Plane CIoT 5GS Optimization, provisioning of external parameters (Expected UE Behavior parameters or Network Configuration parameters), and/or Network Slice-Specific Authentication and Authorization. Some or all of the AMF functionalities may be supported in a single instance of the AMF  1820 . Regardless of the number of Network functions, in certain embodiments there is only one NAS interface instance per access network between the UE and the CN, terminated at one of the Network functions that implements at least NAS security and Mobility Management. The AMF  1820  may also include policy related functionalities. 
     In addition to the functionalities described above, the AMF  1820  may include the following functionality to support non-3GPP access networks: support of N2 interface with N3IWF/TNGF, over which some information (e.g., 3GPP Cell Identification) and procedures (e.g., Handover related) defined over 3GPP access may not apply, and non-3GPP access specific information may be applied that do not apply to 3GPP accesses; support of NAS signaling with a UE over N3IWF/TNGF, wherein some procedures supported by NAS signaling over 3GPP access may be not applicable to untrusted non-3GPP (e.g., Paging) access; support of authentication of UEs connected over N3IWF/TNGF; management of mobility, authentication, and separate security context state(s) of a UE connected via a non-3GPP access or connected via a 3GPP access and a non-3GPP access simultaneously; support a co-ordinated RM management context valid over a 3GPP access and a Non 3GPP access; and/or support dedicated CM management contexts for the UE for connectivity over non-3GPP access. Not all of the above functionalities may be required to be supported in an instance of a Network Slice. 
     The SMF  1822  supports Session Management (e.g., Session Establishment, modify and release, including tunnel maintain between UPF and AN node), UE IP address allocation &amp; management (including optional Authorization) wherein the UE IP address may be received from a UPF or from an external data network, DHCPv4 (server and client) and DHCPv6 (server and client) functions, functionality to respond to Address Resolution Protocol requests and/or IPv6 Neighbor Solicitation requests based on local cache information for the Ethernet PDUs (e.g., the SMF responds to the ARP and/or the IPv6 Neighbor Solicitation Request by providing the MAC address corresponding to the IP address sent in the request), selection and control of User Plane functions including controlling the UPF to proxy ARP or IPv6 Neighbor Discovery or to forward all ARP/IPv6 Neighbor Solicitation traffic to the SMF for Ethernet PDU Sessions, traffic steering configuration at the UPF to route traffic to proper destinations, 5G VN group management (e.g., maintain the topology of the involved PSA UPFs, establish and release the N19 tunnels between PSA UPFs, configure traffic forwarding at UPF to apply local switching, and/or N6-based forwarding or N19-based forwarding), termination of interfaces towards Policy control functions, lawful intercept (for SM events and interface to LI System), charging data collection and support of charging interfaces, control and coordination of charging data collection at the UPF, termination of SM parts of NAS messages, Downlink Data Notification, Initiator of AN specific SM information sent via AMF over N2 to AN, determination of SSC mode of a session, Control Plane CIoT 5GS Optimization, header compression, acting as I-SMF in deployments where I-SMF can be inserted/removed/relocated, provisioning of external parameters (Expected UE Behavior parameters or Network Configuration parameters), P-CSCF discovery for IMS services, roaming functionality (e.g., handle local enforcement to apply QoS SLAs (VPLMN), charging data collection and charging interface (VPLMN), and/or lawful intercept (in VPLMN for SM events and interface to LI System), interaction with external DN for transport of signaling for PDU Session authentication/authorization by external DN, and/or instructing UPF and NG-RAN to perform redundant transmission on N3/N9 interfaces. Some or all of the SMF functionalities may be supported in a single instance of a SMF. However, in certain embodiments, not all of the functionalities are required to be supported in an instance of a Network Slice. In addition to the functionalities, the SMF  1822  may include policy-related functionalities. 
     The SCP  1824  includes one or more of the following functionalities: Indirect Communication; Delegated Discovery; message forwarding and routing to destination NF/NF services; communication security (e.g., authorization of the NF Service Consumer to access the NF Service Producer&#39;s API), load balancing, monitoring, overload control, etc.; and/or optionally interact with the UDR, to resolve the UDM Group ID/UDR Group ID/AUSF Group ID/PCF Group ID/CHF Group ID/HSS Group ID based on UE identity (e.g., SUPI or IMPI/IMPU). Some or all of the SCP functionalities may be supported in a single instance of an SCP. In certain embodiments, the SCP  1824  may be deployed in a distributed manner and/or more than one SCP can be present in the communication path between NF Services. SCPs can be deployed at PLMN level, shared-slice level, and slice-specific level. It may be left to operator deployment to ensure that SCPs can communicate with relevant NRFs. 
     The UE  1816  may include a device with radio communication capabilities. For example, the UE  1816  may comprise a smartphone (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks). The UE  1816  may also comprise any mobile or non-mobile computing device, such as Personal Data Assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, or any computing device including a wireless communications interface. A UE may also be referred to as a client, mobile, mobile device, mobile terminal, user terminal, mobile unit, mobile station, mobile user, subscriber, user, remote station, access agent, user agent, receiver, radio equipment, reconfigurable radio equipment, or reconfigurable mobile device. The UE  1816  may comprise an IoT UE, which can comprise a network access layer designed for low-power IoT applications utilizing short-lived UE connections. An IoT UE can utilize technologies (e.g., M2M, MTC, or mMTC technology) for exchanging data with an MTC server or device via a PLMN, other UEs using ProSe or D2D communications, sensor networks, or IoT networks. The M2M or MTC exchange of data may be a machine-initiated exchange of data. An IoT network describes interconnecting IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure). The IoT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the IoT network. 
     The UE  1816  may be configured to connect or communicatively couple with the (R)AN  1806  through a radio interface  1830 , which may be a physical communication interface or layer configured to operate with cellular communication protocols such as a GSM protocol, a CDMA network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a UMTS protocol, a 3GPP LTE protocol, a 5G protocol, a NR protocol, and the like. For example, the UE  1816  and the (R)AN  1806  may use a Uu interface (e.g., an LTE-Uu interface) to exchange control plane data via a protocol stack comprising a PHY layer, an MAC layer, an RLC layer, a PDCP layer, and an RRC layer. A DL transmission may be from the (R)AN  1806  to the UE  1816  and a UL transmission may be from the UE  1816  to the (R)AN  1806 . The UE  1816  may further use a sidelink to communicate directly with another UE (not shown) for D2D, P2P, and/or ProSe communication. For example, a ProSe interface may comprise one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH). 
     The (R)AN  1806  can include one or more access nodes, which may be referred to as base stations (BS s), NodeB s, evolved NodeB s (eNB s), next Generation NodeB s (gNB), RAN nodes, controllers, transmission reception points (TRPs), and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell). The (R)AN  1806  may include one or more RAN nodes for providing macrocells, picocells, femtocells, or other types of cells. A macrocell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A picocell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femtocell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having an association with the femtocell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in the home, etc.). 
     Although not shown, multiple RAN nodes (such as the (R)AN  1806 ) may be used, wherein an Xn interface is defined between two or more nodes. In some implementations, the Xn interface may include an Xn user plane (Xn-U) interface and an Xn control plane (Xn-C) interface. The Xn-U may provide non-guaranteed delivery of user plane PDUs and support/provide data forwarding and flow control functionality. The Xn-C may provide management and error handling functionality, functionality to manage the Xn-C interface; mobility support for the UE  1816  in a connected mode (e.g., CM-CONNECTED) including functionality to manage the UE mobility for connected mode between one or more (R)AN nodes. The mobility support may include context transfer from an old (source) serving (R)AN node to new (target) serving (R)AN node, and control of user plane tunnels between old (source) serving (R)AN node to new (target) serving (R)AN node. 
     The UPF  1802  may act as an anchor point for intra-RAT and inter-RAT mobility, an external PDU session point of interconnect to the DN  1804 , and a branching point to support a multi-homed PDU session. The UPF  1802  may also perform packet routing and forwarding, packet inspection, enforce user plane part of policy rules, lawfully intercept packets (UP collection); traffic usage reporting, perform QoS handling for user plane (e.g. packet filtering, gating, UL/DL rate enforcement), perform Uplink Traffic verification (e.g., SDF to QoS flow mapping), transport level packet marking in the uplink and downlink, and downlink packet buffering, and downlink data notification triggering. The UPF  1802  may include an uplink classifier to support routing traffic flows to a data network. The DN  1804  may represent various network operator services, Internet access, or third party services. The DN  1804  may include, for example, an application server. 
       FIG.  19    is a block diagram illustrating components  1900 , according to some example embodiments, able to read instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and perform any one or more of the methodologies discussed herein. Specifically,  FIG.  19    shows a diagrammatic representation of hardware resources  1902  including one or more processors  1906  (or processor cores), one or more memory/storage devices  1914 , and one or more communication resources  1924 , each of which may be communicatively coupled via a bus  1916 . For embodiments where node virtualization (e.g., NFV) is utilized, a hypervisor  1922  may be executed to provide an execution environment for one or more network slices/sub-slices to utilize the hardware resources  1902 . 
     The processors  1906  (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP) such as a baseband processor, an application specific integrated circuit (ASIC), a radio-frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, a processor  1908  and a processor  1910 . 
     The memory/storage devices  1914  may include main memory, disk storage, or any suitable combination thereof. The memory/storage devices  1914  may include, but are not limited to, any type of volatile or non-volatile memory such as dynamic random access memory (DRAM), static random-access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), Flash memory, solid-state storage, etc. 
     The communication resources  1924  may include interconnection or network interface components or other suitable devices to communicate with one or more peripheral devices  1904  or one or more databases  1920  via a network  1918 . For example, the communication resources  1924  may include wired communication components (e.g., for coupling via a Universal Serial Bus (USB)), cellular communication components, NFC components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components. 
     Instructions  1912  may comprise software, a program, an application, an applet, an app, or other executable code for causing at least any of the processors  1906  to perform any one or more of the methodologies discussed herein. The instructions  1912  may reside, completely or partially, within at least one of the processors  1906  (e.g., within the processor&#39;s cache memory), the memory/storage devices  1914 , or any suitable combination thereof. Furthermore, any portion of the instructions  1912  may be transferred to the hardware resources  1902  from any combination of the peripheral devices  1904  or the databases  1920 . Accordingly, the memory of the processors  1906 , the memory/storage devices  1914 , the peripheral devices  1904 , and the databases  1920  are examples of computer-readable and machine-readable media. 
     For one or more embodiments, at least one of the components set forth in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, and/or methods as set forth in the Example Section below. For example, the baseband circuitry as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth below. For another example, circuitry associated with a UE, base station, network element, etc. as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth below in the example section. 
     Example Section 
     The following examples pertain to further embodiments. 
     Example 1 is a method of a relay user equipment (UE), comprising: receiving, from a first remote UE, a data packet comprising a radio link control (RLC) protocol data unit (PDU) comprising a packet data convergence protocol (PDCP) PDU and a first adaptation header having first routing information; decoding the first routing information from the first adaptation header at an adaptation layer of the relay UE that is between an RLC layer of the UE and a PDCP layer of the UE; determining, based on the first routing information, that the PDCP PDU should be forwarded to a second remote UE; generating a second packet comprising the PDCP PDU; and forwarding the second packet to the second remote UE. 
     Example 2 is the method of Example 1, wherein the first routing information includes an identity of an end-to-end bearer. 
     Example 3 is the method of Example 2, wherein the end-to-end bearer is a PDCP bearer traveling from the first remote UE, through the relay UE, and terminating at the second remote UE. 
     Example 4 is the method of Example 2, wherein the end-to-end bearer is a data radio bearer (DRB). 
     Example 5 is the method of Example 2, wherein the end-to-end bearer is a signaling radio bearer (SRB). 
     Example 6 is the method of any of Examples 1 through 5, wherein the first routing information includes a Layer 2 address for the second remote UE. 
     Example 7 is the method of any of Examples 1 through 6, wherein the first routing information includes Quality of Service (QoS) information. 
     Example 8 is the method of any of Examples 1 through 7, wherein the second packet comprises a second adaptation header comprising second routing information. 
     Example 9 is the method of any of Examples 1 through 8, wherein the second routing information comprises a Layer 2 address for the first remote UE. 
     Example 10 is a method of a relay user equipment (UE), comprising: receiving, from a first remote UE, a data packet comprising a logical channel identifier (LCID) and a radio link control (RLC) protocol data unit (PDU) comprising a packet data convergence protocol (PDCP) PDU and a first adaptation header having first routing information; decoding the first routing information from the first adaptation header at an adaptation layer of the relay UE that is between an RLC layer of the UE and a PDCP layer of the UE; determining, based on the LCID and the first routing information, that the PDCP PDU should be forwarded to a second remote UE; generating a second packet comprising the PDCP PDU; and forwarding the second packet to the second remote UE. 
     Example 11 is the method of Example 10, wherein the LCID is a value that indicates that the PDCP PDU should be forwarded. 
     Example 12 is the method of any of Examples 10 through 11, further comprising identifying, based on an index located in the first routing information, a bearer between the relay UE and the second remote UE to use to forward the PDCP PDU to the second remote UE; wherein the second packet is forwarded to the second remote UE using the bearer. 
     Example 13 is the method of Example 12, wherein the bearer between the relay UE and the second remote UE is an RLC bearer. 
     Example 14 is a method of a relay user equipment (UE), comprising: receiving, from a first remote UE, a data packet comprising a medium access control (MAC) header, a logical channel identifier (LCID) comprising a routing indication, and a radio link control RLC protocol data unit (PDU) comprising a packet data convergence protocol (PDCP) PDU; determining, based on the routing indication of the LCID and a Layer 2 address provided in the MAC header, that the PDCP PDU should be forwarded to the second remote UE; generating a second packet comprising the PDCP PDU; and forwarding the second packet to the second remote UE. 
     Example 15 is the method of Example 14, further comprising identifying, based on the routing indication in the LCID, a bearer between the relay UE and the second remote UE to use to forward the PDCP PDU to the second remote UE; wherein the second packet is forwarded to the second remote UE using the bearer. 
     Example 16 is the method of Example 15, wherein the bearer between the relay UE and the second remote UE is an RLC bearer. 
     Example 17 is the method of any of Examples 14 through 16, wherein the Layer 2 address is a Layer 2 address of the first remote UE. 
     Example 18 is a method of a relay user equipment (UE) for establishing a hop by hop path configuration, comprising: receiving, from a first remote UE, a first sidelink (SL) configuration message corresponding to a first bearer between the first remote UE and relay UE, the first SL configuration message comprising a first logical channel identifier (LCID), a first Layer 2 address, an end-to-end bearer ID, a next-hop quality of service (QoS) indicator, and a first index; generating a second SL configuration message corresponding to a second bearer between the relay UE and a second remote UE, the second SL configuration message comprising a second LCID, a second Layer 2 address, the end-to-end bearer ID, and a second index; sending, to the second remote UE, the second SL configuration message; receiving, from the second remote UE, a first SL reconfiguration complete message comprising the second index; and sending, to the first remote UE, a second SL reconfiguration complete message comprising the first index. 
     Example 19 is the method of Example 18, wherein each of the first bearer and the second bearer is a radio link control (RLC) bearer. 
     Example 20 is the method of any of Examples 18 through 19, wherein the first bearer between the first remote UE and the relay UE is a new bearer, and wherein the first SL configuration message further comprises new bearer configuration information. 
     Example 21 is the method of any of Examples 18 and 19, wherein the first bearer between the first remote UE and the relay UE is an existing bearer. 
     Example 22 is the method of any of Examples 18 through 21, wherein the second LCID is selected by the relay UE for use in the second SL configuration message based on the next-hop QoS indicator from the first remote UE. 
     Example 23 is the method of any of Examples 18 through 22, wherein the first Layer 2 address is a destination address and the second Layer 2 address is a source address. 
     Example 24 is a method of a relay UE for establishing a hop by hop path configuration, comprising: receiving, from a first remote UE, a first sidelink (SL) configuration message corresponding to a first bearer between the first remote UE and relay UE, the first SL configuration message comprising a first logical channel identifier (LCID) configured to provide a routing indication, a first Layer 2 address, an end-to-end bearer ID, and a next-hop quality of service (QoS) indicator; generating a second SL configuration message corresponding to a second bearer between the relay UE and a second remote UE, the second SL configuration message comprising a second LCID configured to provide a routing indication, a second Layer 2 address, and the end-to-end bearer ID; sending, to the second remote UE, the second SL configuration message; receiving, from the second remote UE, a first SL reconfiguration complete message; and sending, to the first remote UE, a second SL reconfiguration complete message. 
     Example 25 is the method of Example 24, wherein the first bearer between the first remote UE and the relay UE is a new bearer, and wherein the first SL configuration message further comprises new bearer configuration information. 
     Example 26 is the method of Example 24, wherein each of the first bearer and the second bearer is a radio link control (RLC) bearer. 
     Example 27 is the method of any of Examples 24 through 26, wherein the second LCID is selected by the relay UE based on the next-hop QoS indicator from the first remote UE. 
     Example 28 is the method of any of Examples 24 through 27, wherein the first Layer 2 address is a destination address and the second Layer 2 address is a source address. 
     Example 29 may include an apparatus comprising means to perform one or more elements of a method described in or related to any of the above Examples, or any other method or process described herein. 
     Example 30 may include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of a method described in or related to any of the above Examples, or any other method or process described herein. 
     Example 31 may include an apparatus comprising logic, modules, or circuitry to perform one or more elements of a method described in or related to any of the above Examples, or any other method or process described herein. 
     Example 32 may include a method, technique, or process as described in or related to any of the above Examples, or portions or parts thereof. 
     Example 33 may include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform the method, techniques, or process as described in or related to any of the above Examples, or portions thereof. 
     Example 34 may include a signal as described in or related to any of the above Examples, or portions or parts thereof. 
     Example 35 may include a datagram, packet, frame, segment, protocol data unit (PDU), or message as described in or related to any of the above Examples, or portions or parts thereof, or otherwise described in the present disclosure. 
     Example 36 may include a signal encoded with data as described in or related to any of the above Examples, or portions or parts thereof, or otherwise described in the present disclosure. 
     Example 37 may include a signal encoded with a datagram, packet, frame, segment, PDU, or message as described in or related to any of the above Examples, or portions or parts thereof, or otherwise described in the present disclosure. 
     Example 38 may include an electromagnetic signal carrying computer-readable instructions, wherein execution of the computer-readable instructions by one or more processors is to cause the one or more processors to perform the method, techniques, or process as described in or related to any of the above Examples, or portions thereof. 
     Example 39 may include a computer program comprising instructions, wherein execution of the program by a processing element is to cause the processing element to carry out the method, techniques, or process as described in or related to any of the above Examples, or portions thereof. 
     Example 40 may include a signal in a wireless network as shown and described herein. 
     Example 41 may include a method of communicating in a wireless network as shown and described herein. 
     Example 42 may include a system for providing wireless communication as shown and described herein. 
     Example 43 may include a device for providing wireless communication as shown and described herein. 
     Any of the above described examples may be combined with any other example (or combination of examples), unless explicitly stated otherwise. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments. 
     Embodiments and implementations of the systems and methods described herein may include various operations, which may be embodied in machine-executable instructions to be executed by a computer system. A computer system may include one or more general-purpose or special-purpose computers (or other electronic devices). The computer system may include hardware components that include specific logic for performing the operations or may include a combination of hardware, software, and/or firmware. 
     It should be recognized that the systems described herein include descriptions of specific embodiments. These embodiments can be combined into single systems, partially combined into other systems, split into multiple systems, or divided or combined in other ways. In addition, it is contemplated that parameters, attributes, aspects, etc. of one embodiment can be used in another embodiment. The parameters, attributes, aspects, etc. are merely described in one or more embodiments for clarity, and it is recognized that the parameters, attributes, aspects, etc. can be combined with or substituted for parameters, attributes, aspects, etc. of another embodiment unless specifically disclaimed herein. 
     It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     Although the foregoing has been described in some detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered illustrative and not restrictive, and the description is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Metadata:
Filing Date: 20231026
Publication Date: 20241126
Grant Date: 20241126
Priority Date: 20201022
Inventors: WU, ZHIBIN
YE, CHUNXUAN
ZHANG, DAWEI
XU, FANGLI
HU, HAIJING
SUN, HAITONG
ZENG, WEI
CHEN, YUQIN
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W88/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L45/66", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/11", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W40/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W40/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W76/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W88/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/11", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L45/66", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W40/02", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 81289655