Multipath u2n relay failure report with link quality measurements

Abstract

A remote terminal device is connected to a network through a U2N multipath connection that comprises a direct communication link to a direct link serving cell of the network and an indirect communication link to the network through a relay terminal device. In response to determining a radio link failure (RLF) has occurred on one of direct communication link or the indirect communication link, the remote terminal device transmits a failure report comprising one or more sidelink quality measurements.

Description

MULTIPATH U2N RELAY FAILURE REPORT WITH LINK QUALITY MEASUREMENTSCLAIM OF PRIORITY

[0001] The present application claims priority to Provisional Application No. 63 / 531 ,872, entitled “Failure Report Under Multipath U2N Relay”, docket number TPRO 00395 US, filed August 10, 2023, assigned to the assignee hereof and hereby expressly incorporated by reference in its entirety.FIELD

[0002] This invention generally relates to wireless communications and more particularly to failure reports with sidelink quality measurements for multipath connections with a U2N relay terminal.BACKGROUND

[0003] Many wireless communication systems that employ several base stations that provide wireless service to user equipment (UE) devices enable sidelink communication between two or more UE devices where the UE devices can communicate directly with other UE devices. In addition, one or more UE devices can be used as relay devices between a source UE device and a destination UE device where the relay devices forward data received from the source UE device to the destination UE device. Some conventional systems support multipath communication using a relay UE (relay terminal), where a remote UE device (remote terminal) is connected to the network via direct communication link (direct path) and a relay communication link (indirect path). Such techniques have the potential to improve the reliability / robustness as well as throughput of communications. In some situations, the remote terminal initially connects to a base station via the indirect path since the remote terminal may be out-of- coverage (OoC). When the remote terminal moves in-coverage, it may additionally connect to the base station via the direct path, while keeping the indirect path for betterrobustness. When one path fails, with multipath techniques, the other path may work sufficiently well to maintain communication between the remote terminal and the network. In particular, if the direct path experiences RLF (Radio Link Failure) the indirect path may be kept to maintain ongoing communication.SUMMARY

[0004] A remote terminal device is connected to a network through a U2N multipath connection that comprises a direct communication link to a direct link serving cell of the network and an indirect communication link to the network through a relay terminal device. In response to determining a radio link failure (RLF) has occurred on one of direct communication link or the indirect communication link, the remote terminal device transmits a failure report comprising one or more sidelink quality measurements.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 A is a block diagram of a system for an example of link failure reporting for a remote terminal device during U2N multipath operation between a network and the remote terminal device where a link failure report transmitted to the network includes a one or more link quality measurements.

[0006] FIG. 1 B is a block diagram of the system for an example where the indirect communication link experiences an RLF and the remote terminal device transmits the failure report with link quality measurements to the direct link serving cell over the direct communication link.

[0007] FIG. 1 C is a block diagram of the system for an example of terminal reconfiguration in response to the failure report received for an RLF of the indirect communication link.

[0008] FIG. 2 is a block diagram of an example of a base station suitable for use as the network node.

[0009] FIG. 3 is a block diagram of an example of a UE device suitable for use as each of the terminal devices.

[0010] FIG. 4 is a flow chart of method of radio link failure reporting during multipath operation.DETAILED DESCRIPTION

[0011] As discussed above, multipath U2N connections all maintaining the indirect path or direct path when the other path suffers an RLF. In order to ensure proper control from the network, it is desirable for the remote terminal (remote user equipment (UE)) to provide a failure report to the network. For the case when the direct path fails, a failure report may be sent to the network via the relay terminal (relay UE). An example of the direct path failure report in conventional systems is the MCGFailurelnformation which is a Radio Resource Control (RRC) message.

[0012] The base station (gNB) of the network configures the remote terminal with a Signaling Radio Bearer 1 (SRB1 ) which is used to transmit RRC messages from the remote terminal. SRBs are defined as Radio Bearers (RBs) that are used only for the transmission of RRC and NAS messages. In accordance with in or more revisions of the 3GPP communication specification, SRB1 is defined for 5G New Radio (NR) transmission of RRC messages as well as for NAS messages prior to the establishment of SRB2 using the Dedicated Control Channel (DCCH) logical channel. For conventional systems, the SRB1 configuration may be 1 ) a non-split SRB1 where the remote terminal can only send RRC message to the network over the direct path, 2) a split SRB1 where the remote terminal can send RRC messages to the network over either the direct path or the indirect path, and 3) split SRB1 with duplication where the remote terminal is instructed to send RRC messages to the network over both the direct path and the indirect path. For non-split SRB1 , the SRB1 is only configured for the direct communication link.

[0013] Where the direct path experiences an RLF, a failure report is reported through the PC5-RRC connected relay terminal. In conventional systems, however, the failure report can only be reported through the indirect path with split SRB1 configurations. An RRC message is delivered to the network via the PC5-RRC connected relay terminal, but the content of the message is transparent to the relay terminal. More specifically,the RRC message is mapped to the Sidelink Radio Link Control 1 (SL-RLC1 ) in the Sidelink Relay Adaptation Protocol (SRAP) in the sidelink. The relay terminal further maps this to the corresponding RLC channel for the Uu link.

[0014] In conventional systems, therefore, the remote terminal is not be able to send the direct path failure report over the indirect path. In this situation, the remote terminal must declare RLF and attempt to reestablish an RRC connection to the network even though the indirect path is still useable.

[0015] When an RLF occurs in the indirect path, the remote terminal device transmits a failure report to the direct link serving cell in the network. In conventional systems, for example, a master cell group (MCG) Failure Information (MCGFailurelnformation) message (an RRC message) is transmitted over the direct communication link. In order for the direct link serving cell to properly reconfigure the remote terminal device, it would be useful for the serving cell to have link quality information regarding any potential alternate communication links. In accordance with the techniques discussed herein, a failure report is sent to the network where the failure report comprises one or more link quality measurements including at least one sidelink quality measurement of a sidelink to a candidate relay terminal device. In some examples, any combination of quality link measurements of alternate indirect communication links and alternate direct communication links may be provided as well as a quality link measurement for the current direct communication link. In some examples, the remote terminal device transmits, to the direct link serving cell, an RRC message with MCGFailurelnformation that includes Sidelink Reference Signal Received Power (SL-RSRP) measurements of SL communication links to candidate relay terminal devices and direct link RSRP measurements to alternate cells. In other examples, the remote terminal device transmits a UL PC5-RRC message with a failure report including the link quality measurements to the relay terminal device which transmits a UL RRC message to the network with the failure report. Where the remote terminal device is configured with non-split SRB1 , the failure report is encapsulated in the UL PC5-RRC message and the UL RRC message. For example, a remote terminal configured with a non-split SRB1 may transmit an uplink (UL) PC5-RRC message with an encapsulated failure report to the relay terminal providing the relay communication link during U2Nmultipath operation between the network and the remote terminal device. The failure report is generated and the PC5-RRC message is sent in response to the remote terminal determining that the direct communication link to the network has experienced an RLF. The relay terminal device, using its own SRB1 configuration, sends an uplink (LIL) RRC message to the network where the UL RRC message includes the encapsulated failure report. The relay terminal receives a downlink (DL) RRC message from the network where the DL RRC message includes information for reconfiguring the remote terminal. The relay terminal sends a downlink (DL) PC5-RRC message with the information to the remote terminal.

[0016] The direct link serving cell reconfigures the remote terminal device at least partially based on the link quality measurements that include at least one sidelink quality measurement. In some situations, the direct link serving cell may configure a new alternate indirect communication link through a candidate relay terminal device. In other situations, the direct link serving cell configures a new indirect communication link with a handover. Accordingly, service continuity is supported when the indirect path via relay terminal devices are involved. As part of the reconfiguration, the direct link serving cell may reconfigure SRB1 . Where the remote terminal device was originally configured with non-split SRB1 and the remote terminal device reports an RLF on the direct link, for example, the direct link serving cell may configure the remote terminal device with a split SRB1. The direct link serving cell may also send the remote terminal device to RRCJDLE or RRCJNACTIVE in some situations.

[0017] In general, a network node such as a gNB can have multiple cells, whereby the cells may support the same or different portion of the gNB coverage. Additionally, the cells may operate in different frequencies. The indirect communication link and the direct communication link may be through the same cell of a single network node (gNB), may be through two different cells of the same network node, or may be through two different cells where each cell is provided by a different network node. Where the cells providing the direct communication link and the indirect communication link are different, information is routed between the remote terminal and the cell providing the direct path based on entity identification information. A communication interface, such as the Xn interface, is used where the cells are provided by different network nodes. Forthe examples discussed herein, the UL PC5-RRC message and the UL RRC message include a cell identifier and a remote terminal identifier. Also, the DL RRC message includes the remote terminal identifier, allowing the relay terminal to transmit the DL PC5-RRC message to the appropriate terminal device.

[0018] FIG. 1 A is a block diagram of a system 100 for an example of link failure reporting for a remote terminal device 102 during U2N multipath operation between a network 104 and the remote terminal device 102 where a link failure report 106 transmitted to the network 104 includes a one or more link quality measurements 108. The network node 102 is any apparatus, equipment, device, or combination of devices, on the network side of the communication system that is connected to the communication network or is part of communication network. Some examples of a network node include a base station, a node B, an E-UTRA Node B, Evolved Node B, eNodeB, eNB, a New Generation eNB (ng-eNB), a gNodeB (also known as a gNB) in new radio (NR) technology, a macro station, pico station, and a femto station. The network node may form, or be a part of, the radio access network (RAN) that provides a connection between the core network and terminal communication devices. A RAN may be organized into three functional blocks including a Radio Unit (RU), a Distributed Unit (DU) and a Centralized Unit (CU). The RU transmits, receives, amplifies, and digitizes radio frequency signals and typically located near, or integrated into, the antenna. The DU and CU perform computations and / or processing to send and receive digitalized radio signals to and from the core network. The DU is typically located at or near the RU and the CU may be closer to the core network. The infrastructure or connection between the RU and the DU is often referred to as fronthaul and the infrastructure or connection between the DU and the CU is often referred to as a midhaul. The communication node, therefore, may perform the functions of one or more of the RU, DU and / or CU depending on the particular implementation.

[0019] A terminal communication device is a communication device on the terminal side of the communication system and is sometimes referred to as user equipment (UE), a UE device, a terminal device, wireless mobile device, wireless communication device and other terms. Some examples of a terminal communication device include a mobile phone, a smart phone, a personal digital assistant (PDA), tablet, and laptopcomputer. In some situations, the terminal communication device is a machine type communication (MTC) communication device or Internet-of-Things (IOT) device. In addition, the terminal communication device may be, or may be a part of, a wearable device or a vehicle where the vehicle may be terrestrial vehicle, watercraft, or aircraft (including unmanned aerial vehicles). The terminal communication device, therefore, is any fixed, mobile, or portable equipment that performs the functions of the terminal device described herein.

[0020] For the example, the remote terminal device 102 is connected through a direct communication link 110 to a direct link serving cell 112 provided by a network node in the network 104 and is also connected through an indirect communication link (relay communication link) 114 via a relay terminal device 116 to a cell provided by a network node (e.g., gNB) in the network 104. As discussed above and in the examples below, a single cell may facilitate both links 110, 114 or different cells may facilitate the two links 110, 114, where both cells may be provided by a single network node or each of the two cells is provided by a different network node. For the example of FIG. 1 A, a relay serving cell 117 is illustrated with a dashed box to indicate that the indirect communication path 114 may include a communication link to a relay serving cell 117 different from the direct link serving cell 112. Where the direct link serving cell and the relay serving cell 117 are provided by different network nodes (e.g., gNBs) an Xn interface between the two network nodes facilitates communication to the direct link serving cell 112.

[0021] During U2N multipath operation, the remote terminal device 102 determines that one of the communication links forming the U2N multipath connection has experiences a radio link failure (RLF) and, in response, generates a radio link failure report 106 for transmission to the network 104 over the communication link that has not experienced the RLF. Therefore, when the direct communication link 110 experiences an RLF, the remote terminal device 102 sends the failure report 106 over the indirect communication link 114. Where the remote terminal device is configured with split SRB1 or split SRB1 with duplication, the failure report is transmitted in an RRC message that is transparent to the relay terminal device using SRAP. Where the remote terminal device is configured with non-split SRB1 , the failure report is encapsulated andtransmitted in a PC5-RRC message to the relay terminal device and forwarded by the relay terminal device to the network in an UL RRC message using the SRB1 configuration of the relay terminal device.

[0022] The failure report 106 includes link quality measurements 108 of communication links that may include sidelinks to candidate relay terminal devices and links to alternate cells as well as currently active links to relay terminal devices and serving cells. For example, where an RLF has been detected on the direct communication link 110, the link quality measurements 108 include a measurement of the sidelink 120 to a candidate relay terminal device 122 and may include a measurement of the sidelink 118 to the relay terminal device 116, and / or a measurement of the link 124 to one or more alternate cells 126. The alternate cell(s) 126 may be provided by the same network node (e.g., gNB) providing the direct link serving cell 112, the same network node (e.g., gNB) providing the serving cell to the relay terminal device 116, or by another network different from both serving cells. For the examples herein, the link quality measurements 108 are Reference Signal Received Power (RSRP) measurements. The link quality measurements 108 of the links to relay terminal devices, therefore, are Sidelink Reference Signal Received Power (SL-RSRP) measurements for the examples. The quality measurements 108, however, may be any type of measurement that indicates a quality of the link being measured.

[0023] For the non-split SRB1 configuration where the direct communication link experiences an RLF, the remote terminal device 102 generates and transmits a UL direct communications interface (PC5) radio resource control (RRC) message (UL PC5- RRC message) including an encapsulated version of the direct radio link failure report 106. The relay terminal device 116 receives the UL PC5-RRC message with the failure report 106 over the PC5 connection and generates a UL RRC message that includes the encapsulated failure report 106. The relay terminal device 116 is configured with an SRB1 (relay terminal SRB1 ) different from the non-split SRB1 configuration (remote terminal SRB1 ) of the remote terminal device 102. Using the relay terminal SRB1 , the relay terminal device transmits the UL RRC message with the encapsulated failure report 106 to the network 104. Where the relay serving cell is different from the remoteterminal direct link serving cell, the information in the UL RRC message is forwarded to the remote terminal direct link serving cell. The UL PC5-RRC message and the UL RRC message each include a remote terminal identifier and a cell identifier of the remote terminal direct link serving cell and the failure report 106 includes one or more link quality measurements.

[0024] FIG. 1 B is a block diagram of the system 100 for an example where the indirect communication link 114 experiences an RLF 130 and the remote terminal device 102 transmits the failure report 106 with link quality measurements 108 to the direct link serving cell 112 over the direct communication link 110. The link quality measurements 108 include at least one sidelink quality measurement of sidelink to a candidate relay device. For the example, the remote terminal device 102 measures the communication links 124 to other cells 126 and the sidelinks 120 to candidate relay devices 122 to determine an RSRP and / or SL-RSRP for each alternate link 120, 124. The remote terminal device 102 may measure any number of alternate links. The failure report 106 is transmitted in an uplink (UL) RRC message 132 using the SRB1 configuration of the remote terminal device 102. For the example, the UL RRC message 132 is an MCGFailurelnformation message as defined by one or more revisions of the 3GPP communication specification except that the MCGFailurelnformation message for the example includes the additional information related to the link quality measurements 108. An example of a suitable technique for conveying the link quality measurement information includes associating an RSRP and / or SL-RSRP value to a cell identifier identifying the alternate cell providing the alternate link or the terminal identifier identifying a candidate relay terminal device.

[0025] FIG. 1 C is a block diagram of the system 100 for an example of terminal reconfiguration in response to the failure report 106 received for an RLF of the indirect communication link 114. After receiving the failure report information, the remote terminal direct link serving cell 112 determines a preferred action for the remote terminal device 102 and sends a dedicated control channel (DCCH) message 134 to the remote terminal device 102. Examples of preferred actions include reconfiguring the remote terminal device 102 with a single communication path where the single path may be adirect communication path or an indirect communication path. The direct communication path may be the current direct communication link 110 or may be a new direct communication link to another cell. Therefore, the direct link serving cell 112 may invoke a handover to a new cell in some situations. The direct link serving cell 112 may also reconfigure the remote terminal device 102 with a multipath connection that includes a new indirect communication link through a candidate relay terminal device. Where all available alternative paths have poor quality, the preferred action may include sending the remote terminal device to RRCJDLE or RRCJNACTIVE. For example, where the SL-RSRP measurements 108 included in the failure report 106 indicate that the available indirect paths have a channel quality below a threshold and the direct communication link 110 is below a quality threshold, the remote terminal direct link serving cell may send an RRC Release message to transition the remote terminal device to IDLE or INACTIVE. In some situations, the remote terminal device 102 may be reconfigured with a different SRB1 . Where the original SRB1 configuration for the multipath connection was a non-split SRB1 , the new SRB1 configuration may be split- SRB1.

[0026] For the example of FIG. 1 C, the remote terminal device 102 is reconfigured with a multipath connection including the original direct communication link 110 and a new indirect communication path 136 via a candidate relay terminal device 122. The remote terminal direct link serving cell 112 generates a dedicated control channel (DCCH) message 134 for reconfiguring the remote terminal device 102. The direct link serving cell 112 in the network 104 transmits a DL RRC message 138 including the DCCH message 134. In response to the DCCH message 134, the remote terminal device 102 establishes the new relay communication link 136 in accordance with conventional techniques. The relay communication link 136 may be through the direct link serving cell 112 or may be though a relay serving cell 140. The box representing the relay serving cell 140 includes dashed lines to illustrate that a cell different from the direct link serving cell 112 may be used. The relay serving cell 140 may be provided by the same network node providing the direct link serving cell 112 or may be provided by a different network node.

[0027] Therefore, the remote terminal device 102 detects the RLF on the indirect path during multipath operation and, in response, sends a failure report to the direct link serving cell where the failure report indicates the RLF has occurred and comprises one or more RSRP or SL-RSRP measurements (link quality measurements 108) of alternate communication links. The direct link serving cell 112 evaluates the link quality measurements 108 and determines, at least partially based on measurements, the appropriate action for the remote terminal device 102. The serving cell 112 generates and sends a DCCH message as DL RRC message over the direct communication linkl 110 to the remote terminal device. For the example, the DCCH message instructs the remote terminal device to establish the indirect communication link (new relay communication link) 136 through a candidate relay terminal device 122. In response to the DCCH message, the remote terminal device 102 establishes the relay communication link 136 and maintains a multipath connection to the network 104.

[0028] In the examples below, the network nodes and terminal devices are represented by base stations and UE devices, respectively. The functions and operations performed by the base station and UE devices may be applied to other types of network nodes and terminal devices. The examples and embodiments are merely preferred examples and are not intended to limit the present disclosure. Accordingly, the system may include any desired combination of base stations, UE devices, and other equipment, while remaining within the scope of the present disclosure.

[0029] FIG. 2 is a block diagram of an example of a base station 200 suitable for use as a network node. The base station 200 includes electronics 204, transmitter 206, a receiver 208, and multiple antennas 210, as well as other electronics, hardware, and code. The base station 200 is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to the base station 200 and network node 102 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices. The base station 200 may be a fixed device or apparatus that is installed at a particular location at the time of system deployment. Examples of such equipment include fixed basestations or fixed transceiver stations. Although the base station may be referred to by different terms, the base station is typically referred to as a gNodeB or gNB when operating in accordance with one or more communication specifications of the 3GPP V2X operation. In some situations, the base station 200 may be mobile equipment that is temporarily installed at a particular location. Some examples of such equipment include mobile transceiver stations that may include power generating equipment such as electric generators, solar panels, and / or batteries. Larger and heavier versions of such equipment may be transported by trailer. In still other situations, the base station 200 may be a portable device that is not fixed to any particular location.

[0030] The electronics 204 include any combination of hardware, software, and / or firmware for communicating with and controlling other base station components to execute the functions described herein as well as facilitating the overall functionality of the base station 200. The electronics 204, therefore, cooperatively operate with other base station 200 components to initiate tasks and perform the operations and functions of the base station 200. An example of suitable electronics 204 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 206 includes electronics configured to transmit wireless signals. In some situations, the transmitter 206 may include multiple transmitters. The receiver 208 includes electronics configured to receive wireless signals. In some situations, the receiver 208 may include multiple receivers. The receiver 208 may receive signals through multiple antennas 210 or through a selected antenna of the plurality of antennas 210. The antennas 210 may include separate transmit and receive antennas.

[0031] The transmitter 206 and receiver 208 in the example of FIG. 2 perform radio frequency (RF) processing including modulation and demodulation. The receiver 208, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 206 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the base station functions. The required components may depend on the particular functionality required by the base station 200.

[0032] The transmitter 206 includes a modulator (not shown), and the receiver 208 includes a demodulator (not shown). The modulator modulates the signals to be transmitted as part of the downlink signals and can apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signals received at the base station 200 in accordance with one of a plurality of modulation orders. The electronics 204 in conjunction with the transmitter 206 apply a precoder matrix to signals transmitted through the multiple antennas 210.

[0033] The base station 200 includes a communication interface 212 for communicating with other base stations and other network components, and other entities, such as servers and databases. The communication interface 212 may be connected to a backhaul or network enabling communication with other base stations. In some situations, the link between base stations may include at least some wireless portions. The communication interface 212, therefore, may include wireless communication functionality and may utilize some of the components of the transmitter 206 and / or receiver 208.

[0034] The electronics 204, in conjunction with the receiver 208, measure and evaluate signals transmitted by UE devices. The electronics 204 and the receiver 206, therefore, can receive, measure, and evaluate uplink signals including reference signals transmitted by UE devices. Signal measurements and evaluations can be stored in a memory 214 and are used to determine the location of UE devices in some circumstances.

[0035] The electronics 204, in conjunction with the transmitter 206 and antennas 210, process outgoing signals to precode signals transmitted to UE devices. Accordingly, the electronics 204 and transmitter 206 apply the appropriate MU-MIMO precoder to signals transmitted to a specific UE device.

[0036] FIG. 3 is a block diagram of an example of a UE device 300 suitable for use as each of the terminal devices 102, 116, 122. In some examples, the UE device 300 is any wireless communication device such as a mobile phone, a transceiver modem, a personal digital assistant (PDA), a tablet, or a smartphone. In other examples, the UE device 300 is a machine type communication (MTC) communication device or Internet-of-Things (IOT) device. The UE device 300, therefore is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to UE device 300 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices.

[0037] The UE device 300 includes at least electronics 302, a transmitter 304 and a receiver 306. The electronics 302 include any combination of hardware, software, and / or firmware for communicating with and controlling other UE device components to execute the functions described herein as well as facilitating the overall functionality of a communication device. The electronics 302, therefore, cooperatively operate with other UE device components to initiate tasks and perform the operations and functions of the UE device 300. An example of suitable electronics 302 includes code running on a microprocessor or processor arrangement connected to memory 310. The transmitter 304 includes electronics configured to transmit wireless signals. In some situations, the transmitter 304 may include multiple transmitters. The receiver 306 includes electronics configured to receive wireless signals. In some situations, the receiver 306 may include multiple receivers. The receiver 306 and transmitter 304 receive and transmit signals, respectively, through antenna 308. The antenna 308 may include separate transmit and receive antennas. In some circumstances, the antenna 308 may include multiple transmit and receive antennas.

[0038] The transmitter 304 and receiver 306 in the example of FIG. 3 perform radio frequency (RF) processing including modulation and demodulation. The receiver 306, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 304 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the communication device functions. The required components may depend on the particular functionality required by the communication device.

[0039] The transmitter 304 includes a modulator (not shown), and the receiver 306 includes a demodulator (not shown). The modulator can apply any one of a plurality ofmodulation orders to modulate the signals to be transmitted as part of the uplink signals. The demodulator demodulates the downlink signals in accordance with one of a plurality of modulation orders.

[0040] The UE device 300 is capable of transmitting and receiving sidelink signals to and from other UE devices as well as communicating with base stations. The electronics 302, in conjunction with the receiver 306, measure an evaluate signals transmitted by other devices, such as base stations and UE devices. The electronics 302 and the receiver 306, therefore, can receive, measure, and evaluate downlink reference signals transmitted by a base station. Signal measurements and evaluations can be stored in the memory 310. The electronics 302 and receiver 306 can also receive, measure and evaluate discovery signals transmitted by nearby UE devices to generate a neighbor list that includes neighbor UE devices within the maximum distance. The neighbor list is stored in the memory 310 and may be transmitted to a base station.

[0041] FIG. 4 is a flow chart of method of radio link failure reporting during multipath operation. The method may be performed in a system such as the system 100 discussed herein. The method is performed by a terminal device such as the remote terminal device 102 or UE device 300 and may be performed using any of several techniques involving any combination of electronics, software, hardware, and firmware. For example, software code running on electronics including a processor, computer or other processor arrangement within the remote terminal device 102 may facilitate the generation, formatting, and transmission of the failure report 106. One or more of the steps may be omitted, combined, performed in parallel, or performed in a different order than that described herein or shown in FIG. 4. In still further examples, additional steps may be added that are not explicitly described in connection with the example discussed with reference to FIG. 4. For example, steps for obtaining the link quality measurements are performed even though not explicitly shown in FIG. 4

[0042] At step 402, a U2N multipath connection is maintained between the remote terminal device and the network 104 where the U2N multipath connection includes the direct communication link 110 and the indirect communication link (relay communicationlink) 114. As discussed above, the serving cell of the relay terminal device and the serving cell of remote terminal device may be the same cell or different cells. Where the cells are different each cell may be provided by a different network node or the same network node.

[0043] At step 404, an RLF is detected on one of the communication links 110, 114 of the U2N multipath connection. The remote terminal device determines that either the direct communication link 110 or the indirect communication link 114 has experienced an RLF.

[0044] At step 406, a failure report is sent to the network. The remote terminal device generates and sends a failure report over the communication link that has not experience an RLF where the failure report indicates that the RLF has occurred and comprises one or more link quality measurements. The link quality measurements include at least one sidelink quality measurement of a sidelink to a candidate relay device. In some examples, the link quality measurements are RSRP and SL-RSRP measurements of links to alternate cells and candidate relay terminal devices and may also include RSRP measurements of the current links. Where the indirect communication link 114 has experienced the RLF, the remote terminal device transmits an UL RRC message over the direct communication link to the serving cell. The UL RRC message includes the failure report and may be in accordance with a conventional MCGFailurelnformation message but includes the link quality measurements with at least one sidelink quality measurement to a candidate relay device. Where the direct communication link 110 has experienced the RLF and the remote terminal device is configured with split SRB1 , the remote terminal device transmits an UL RRC message over the indirect communication link through the relay terminal device to the network. Where the relay serving cell and the direct link serving cell are different cells, the message (or information based on the message) is forwarded to the serving cell of the remote terminal device. The UL RRC message includes the failure report and may be in accordance with a conventional MCGFailurelnformation message but includes the link quality measurements.

[0045] In situations where the remote terminal device is configured with a non-split SRB1 configuration and the direct communication link experiences an RLF, the remote terminal device 102 generates and transmits a UL PC5-RRC message including an encapsulated version of the failure report. The relay terminal device 116 receives the UL PC5-RRC message with the failure report 106 over the PC5 connection and generates a UL RRC message that includes the encapsulated failure report 106. The relay terminal device 116 is configured with an SRB1 (relay terminal SRB1 ) different from the non-split SRB1 configuration (remote terminal SRB1 ) of the remote terminal device 102. Using the relay terminal SRB1 , the relay terminal device transmits the UL RRC message with the encapsulated failure report 106 to the network 104. Where the relay serving cell is different from the remote terminal direct link serving cell, the information in the UL RRC message is forwarded to the remote terminal direct link serving cell. The UL PC5-RRC message and the UL RRC message each include a remote terminal identifier and a cell identifier of the remote terminal direct link serving cell and the failure report 106 includes one or more link quality measurements.

[0046] At step 408, a DCCH message is received from the serving cell 112. The DCCH message is at least partially based on the link quality measurements reported in the failure report 106. Where the DCCH message received over the indirect communication link and the remote terminal device is configured with non-split SRB1 , the DCCH message is received in a PC5-RRC message from the relay terminal device.

[0047] At step 410, the remote terminal device performs the operations directed by the DCCH message which may include operations, such as performing a handover to an alternate cell, establishing an alternate indirect communication link, establishing a new SRB1 configuration, entering RRCJNACTIVE, and entering RRC-IDLE.

[0048] To clearly illustrate this interchangeability of hardware, firmware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in various ways for eachparticular application, but such implementation decisions do not cause a departure from the scope of the present disclosure. In accordance with various embodiments, a processor, device, component, circuit, structure, machine, module, etc. can be configured to perform one or more of the functions described herein. The term "configured to" or "configured for" as used herein with respect to a specified operation or function refers to processors, devices, components, circuits, electronics, and equipment that are physically constructed, programmed, instructed and / or arranged to perform the specified operation or function. Furthermore, the various illustrative logical blocks, modules, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), other electronics or combinations thereof. (ASIC), a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, electronics, and circuits can further include antennas and / or transceivers to communicate with various components within the network or within the device. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein.

[0010] When implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored on a computer- readable medium. Computer readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program or code from one place to another. A storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices,or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0001] Therefore, the methods and apparatus of this invention may take the form, at least partially, of program logic or program code (i.e., instructions) embodied in tangible media, such as a machine-readable storage medium. When the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. The methods and apparatus of the present invention may also be embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission. When the program code is received and loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates analogously to specific logic circuits.

[0049] Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present disclosure. It will be appreciated that, for clarity purposes, the above description has described embodiments of the present disclosure with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements or domains may be used without detracting from the present disclosure. For example, functionality illustrated to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Therefore, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

[0050] Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of theinvention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims

CLAIMS1 . A method comprising: maintaining a U2N multipath connection to a network, the U2N multipath connection comprising a direct communication link to a direct link serving cell of a current network node of the network and an indirect communication link to the network through a relay terminal device; determining that a radio link failure (RLF) has occurred on one of the direct communication link or the indirect communication link; in response to determining that the RLF has occurred, transmitting a failure report message to the network, the failure report indicating the RLF has occurred and comprising at least one sidelink quality measurement for an alternate sidelink communication link other than the indirect communication link.

2. The method of claim 1 , wherein determining that the RLF has occurred comprises determining the RLF has occurred on the indirect communication link, and wherein the transmitting the failure report comprises transmitting the failure report over the direct communication link.

3. The method of claim 1 , wherein the at least one link quality measurement comprises at least one of Sidelink Reference Signal Received Power (SL-RSRP) measurement of a sidelink communication link to an alternate relay terminal device.

4. The method of claim 3, wherein the at least one link quality measurement comprises a current cell RSRP measurement of the direct communication link.

5. The method of claim 3, wherein the failure report is a MCGFailurelnformation message with a link quality measurement field for conveying the at least one link quality measurement.

6. The method of claim 1 , wherein determining that the RLF has occurred comprises determining the RLF has occurred on the direct communication link, andwherein the transmitting the failure report comprises transmitting the failure report over the indirect communication link.

7. The method of claim 6, wherein transmitting the failure report comprises transmitting, to the relay terminal device, an uplink (UL) direct communications interface (PC5) radio resource control (RRC) message (UL PC5-RRC message) comprising an encapsulated direct radio link failure report generated in response to detecting the radio link failure of the direct path communication link.

8. The method of claim 7, wherein the at least one sidelink quality measurement comprises at least one of Sidelink Reference Signal Received Power (SL-RSRP) measurement of a sidelink communication link to an alternate relay terminal device.

9. The method of claim 8, wherein the at least one link quality measurement comprises a current cell RSRP measurement of the direct communication link.

10. A remote terminal device comprising: a transceiver comprising a transmitter and a receiver, the transceiver configured to maintaining a U2N multipath connection to a network, the U2N multipath connection comprising a direct communication link to a direct link serving cell of a current network node of the network and an indirect communication link to the network through a relay terminal device; and electronics configured to determine that a radio link failure (RLF) has occurred on one of the direct communication link or the indirect communication link; the transmitted configured to transmit, in response to determining that the RLF has occurred, a failure report message to the network, the failure report indicating the RLF has occurred and comprising at least one sidelink quality measurement for an alternate sidelink communication link other than the indirect communication link.11 . The remote terminal device of claim 10, wherein the electronics are configured to determine that the RLF has occurred on the indirect communication link, and whereinthe transmitter is configured to transmit the failure report over the direct communication link.

12. The remote terminal device of claim 10, wherein the at least one sidelink quality measurement comprises at least one of Sidelink Reference Signal Received Power (SL- RSRP) measurement of a sidelink communication link to an alternate relay terminal device.

13. The remote terminal device of claim 12, wherein the at least one link quality measurement comprises a current cell RSRP measurement of the direct communication link.

14. The remote terminal device of claim 12, wherein the failure report is a MCGFailurelnformation message with a link quality measurement field for conveying the at least one link quality measurement.

15. A method comprising: maintaining a U2N multipath connection to between a network and a remote terminal device, the U2N multipath connection comprising a direct communication link from a direct link serving cell of a current network node of the network and an indirect communication link from the network through a relay terminal device; receiving a failure report message from the remote terminal device, the failure report indicating a radio link failure (RLF) has occurred on one of the direct communication link or the indirect communication link, the failure report comprising at least one sidelink quality measurement for an alternate sidelink communication link other than the indirect communication link; and determining a preferred operation of the remote terminal device at least partially based on the at least one link quality measurement.

16. The method of claim 15, wherein the RLF has occurred on the indirect communication link, and wherein receiving the failure report comprises receiving the failure report over the direct communication link.

17. The method of claim 16, wherein the at least one sidelink quality measurement comprises at least one of Sidelink Reference Signal Received Power (SL-RSRP) measurement of a sidelink communication link to an alternate relay terminal device.

18. The method of claim 17, wherein the at least one link quality measurement comprises a current cell RSRP measurement of the direct communication link.

19. The method of claim 17, wherein the failure report is a MCGFailurelnformation message with a link quality measurement field for conveying the at least one link quality measurement.

20. A network comprising: a transceiver comprising a transmitter and receiver, the transceiver configured to maintain a U2N multipath connection between the network and a remote terminal device, the U2N multipath connection comprising a direct communication link from a direct link serving cell of a current network node of the network and an indirect communication link from the network through a relay terminal device; the receiver configured to receive a failure report message from the remote terminal device, the failure report indicating a radio link failure (RLF) has occurred on one of the direct communication link or the indirect communication link, the failure report comprising at least one sidelink quality measurement for an alternate communication link other than the direct communication link and the indirect communication link; and electronics configured to determine a preferred operation of the remote terminal device at least partially based on the at least one link quality measurement.21 . A non-transitory computer readable medium storing computer-executable instructions which when executed perform the method of:maintaining a U2N multipath connection to a network, the U2N multipath connection comprising a direct communication link to a direct link serving cell of a current network node of the network and an indirect communication link to the network through a relay terminal device; determining that a radio link failure (RLF) has occurred on one of the direct communication link or the indirect communication link; in response to determining that the RLF has occurred, transmitting a failure report message to the network, the failure report indicating the RLF has occurred and comprising at least one sidelink quality measurement for an alternate communication link other than the direct communication link and the indirect communication link.

Images