RRC Reestablishment and Radio Link Failure Reporting in a Sidelink Relay System

Abstract

Certain aspects of the present disclosure provide techniques for RRC connection reestablishment for a remote UE. In some cases, the remote UE may be configured to detect a radio link failure (RLF) that causes a radio resource control (RRC) connection loss on at least one of a first link between a first relay UE and a first network entity or a second link between the remote UE and the first relay UE, and attempt to reestablish the RRC connection by performing at least one of relay selection or cell selection.

Description

Technical Field

[0001] Broadly speaking, aspects of the present disclosure relate to wireless communication. Specifically, aspects of the present disclosure relate to techniques for performing radio resource control (RRC) connection reestablishment after a user equipment (UE) detects a radio link failure in a sidelink relay system. Background Art

[0002] Wireless communication systems have been widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasting, and so on. These wireless communication systems may employ multiple access technologies that can support communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple access systems include the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) system, LTE-Advanced (LTE-A) system, Code Division Multiple Access (CDMA) system, Time Division Multiple Access (TDMA) system, Frequency Division Multiple Access (FDMA) system, Orthogonal Frequency Division Multiple Access (OFDMA) system, Single Carrier Frequency Division Multiple Access (SC-FDMA) system, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) system, to name just a few.

[0003] In some examples, a wireless multiple access communication system may include multiple base stations (BSs), each BS capable of simultaneously supporting communication of multiple communication devices (or referred to as user equipment (UEs)). In an LTE or LTE-A network, a group of one or more base stations may define an evolved Node B (eNB). In other examples (e.g., in a next generation, New Radio (NR) or 5G network), a wireless multiple access communication system may include multiple distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission and reception points (TRPs), etc.) communicating with multiple central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a group of one or more DUs communicating with a CU may define an access node (e.g., which may be referred to as a BS, 5G NB, next generation Node B (gNB or gNodeB), transmission and reception point (TRP), etc.). A BS or DU may communicate with a group of UEs on a downlink channel (e.g., for transmission from the BS or DU to the UE) and an uplink channel (e.g., for transmission from the UE to the BS or DU).

[0004] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate over a city-wide, country-wide, regional, or even global scale. NR (e.g., New Radio or 5G) is an example of an emerging telecommunication standard. NR is an evolved set of the LTE mobile standard released by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, enhancing services, making full use of new spectrum, and better integrating with other open standards that use OFDMA and cyclic prefix (CP) on the downlink (DL) and uplink (UL). To this end, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0005] Sidelink communication is communication from one UE to another UE. With the continuous increase in the demand for mobile broadband access, there is a need to further improve NR and LTE technologies, including improvements for sidelink communication. Preferably, these improvements can also be applicable to other multiple access technologies and communication standards that employ these technologies. Summary of the Invention

[0006] The systems, methods, and devices of the present disclosure all have some aspects, but no single one of these aspects can solely be responsible for their desired attributes. The claims set forth below do not limit the scope of the present disclosure, and some features will now be briefly discussed. After carefully considering these discussions, particularly after reading the section entitled "Detailed Description," one will understand how the features of the present disclosure have advantages, including improved communication between access points and stations in a wireless network.

[0007] Certain aspects provide a method for wireless communication of a remote UE. Generally, the method includes: detecting a radio link failure (RLF) that causes a radio resource control (RRC) connection loss on at least one of a first link between a first relay UE and a first network entity or a second link between the remote UE and the first relay UE; and attempting to reconstruct the RRC connection by performing at least one of relay selection or cell selection.

[0008] Certain aspects provide a method for wireless communication of a network entity. Generally, the method includes: receiving a radio resource control (RRC) reconstruction request message from a remote user equipment (UE); determining whether the remote UE was previously connected to the network entity or another network entity via a first relay UE; if the UE was previously connected to the other network entity, retrieving the context of the remote UE from the other network entity; and sending an RRC reconstruction message or an RRC establishment message to the remote UE.

[0009] Each aspect generally includes a method, an apparatus, a system, a computer-readable medium, and a processing system, as described herein with reference to the accompanying drawings and shown in the drawings.

[0010] To achieve the foregoing and related purposes, one or more aspects include the features described in detail below and particularly pointed out in the claims. The following description and the drawings detail certain exemplary features of one or more aspects. However, these features merely illustrate some of the various ways in which the basic principles of these various aspects may be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] To understand in detail how the above-described features of the present disclosure are implemented, the present application provides a more specific description with reference to some aspects given above, some of which are illustrated in the accompanying drawings. However, it should be noted that since the description of the present invention admits other equivalent effective aspects, these drawings merely depict certain exemplary aspects of the present disclosure and should not be considered as limiting the scope of the present invention.

[0012] Figure 1 is a block diagram conceptually illustrating an exemplary telecommunications system in accordance with certain aspects of the present disclosure.

[0013] Figure 2 is a block diagram showing an exemplary logical architecture of a distributed radio access network (RAN) in accordance with certain aspects of the present disclosure.

[0014] Figure 3 is a diagram showing an exemplary physical architecture of a distributed RAN in accordance with certain aspects of the present disclosure.

[0015] Figure 4 is a block diagram conceptually showing a design of an exemplary base station (BS) and a user equipment (UE) in accordance with certain aspects of the present disclosure.

[0016] Figure 5 is a high-level path diagram showing an exemplary connection path of a remote user equipment (UE) in accordance with certain aspects of the present disclosure.

[0017] Figure 6 is an exemplary block diagram showing a control plane protocol stack on L3 in the case where there is no direct connection path between a remote UE and a network node in accordance with certain aspects of the present disclosure.

[0018] Figure 7 is an exemplary block diagram showing a control plane protocol stack on L2 in the case where there is no direct connection path between a remote UE and a network node in accordance with certain aspects of the present disclosure.

[0019] Figure 8According to certain aspects of the present disclosure, an exemplary Layer 3 (L3) relay procedure is shown.

[0020] Figure 9 According to certain aspects of the present disclosure, an exemplary Layer 2 (L2) relay procedure is shown.

[0021] Figure 10A And Figure 10B An exemplary relay discovery procedure is shown.

[0022] Figure 11 An example communication environment is shown in which a relay UE serves one or more remote UEs.

[0023] Figure 12 According to certain aspects of the present disclosure, example operations for wireless communication of a remote UE are shown.

[0024] Figure 13 According to certain aspects of the present disclosure, example operations for wireless communication of a network entity are shown.

[0025] Figures 14 - 17 According to certain aspects of the present disclosure, a call flow diagram of an example scenario in which a remote UE can re - establish an RRC connection in a sidelink relay system is shown.

[0026] Figure 18 According to certain aspects of the present disclosure, shown is a communication device that can include various components configured to perform the operations shown in Figure 12 The operations shown in.

[0027] Figure 19 According to certain aspects of the present disclosure, shown is a communication device that can include various components configured to perform the operations shown in Figure 13 The operations shown in.

[0028] For ease of understanding, the same reference numerals have been used, wherever possible, to denote the same elements common to the figures. It should be appreciated that elements disclosed in one aspect may be beneficially applied to other aspects without further recitation. Detailed Description

[0029] Aspects of the present disclosure relate to wireless communication, and more particularly, aspects of the present disclosure relate to techniques for performing radio resource control (RRC) connection re - establishment after a user equipment (UE) detects a radio link failure in a sidelink relay system.

[0030] The connection between a repeater and a network entity can be referred to as a Uu connection or via a Uu path. The connection between a remote UE and a repeater (e.g., another UE or a "relay UE") can be referred to as a PC5 connection or via a PC5 path. A PC5 connection is a device-to-device connection that can utilize the relative proximity between the remote UE and the relay UE (e.g., when the remote UE is closer to the relay UE than the nearest base station). The relay UE can be connected to an infrastructure node (e.g., a gNB) via a Uu connection and relay the Uu connection to the remote UE via a PC5 connection.

[0031] The following description provides some examples, but it does not limit the scope of protection, applicability, or examples set forth in the claims. Changes can be made to the functions and arrangements of the elements discussed without departing from the scope of the present disclosure. Each example can omit, substitute, or add various processes or components as needed. For example, the described methods can be performed in a different order than described, steps can be added, omitted, or combined. Additionally, the features described for some examples can be combined into other examples. For instance, a device can be implemented or a method can be implemented using any number of aspects set forth herein. Moreover, the scope of the present disclosure is intended to cover such a device or method that can be implemented by using other structures, functions, or structures and functions different from those of the aspects of the present disclosure set forth herein or in addition to the structures and functions of the aspects of the present disclosure set forth herein. It should be understood that any aspect of the disclosure herein can be embodied by one or more components of the present invention. As used herein, the term "exemplary" means "serving as an example, illustration, or explanation". Any aspect described as "exemplary" herein should not be construed as more preferred or more advantageous than other aspects.

[0032] The techniques described herein can be used in various wireless communication technologies, such as, LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other networks. The terms "network" and "system" are often used interchangeably. A CDMA network may implement radio technologies such as Universal Terrestrial Radio Access (UTRA), CDMA 2000, and the like. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. CDMA2000 covers the IS-2000, IS-95, and IS-856 standards. A TDMA network may implement radio technologies such as Global System for Mobile Communications (GSM). An OFDMA network may implement radio technologies such as NR (e.g., 5G RA), evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and the like. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS).

[0033] New Radio (NR) is an emerging wireless communication technology that is deployed in conjunction with the 5G Technology Forum (5GTF). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that employ E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). CDMA2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). The techniques described herein can be used in the wireless networks and radio technologies mentioned above and other wireless networks and radio technologies. For clarity, while the present disclosure uses terms commonly associated with 3G and / or 4G wireless technologies to describe aspects, aspects of the present disclosure may also be applied to communication systems based on other generations (e.g., 5G and later generations including NR technology).

[0034] New Radio (NR) access (e.g., 5G technology) can support various wireless communication services, such as enhanced mobile broadband (eMBB) targeted for relatively wide bandwidths (e.g., 80 MHz or above), millimeter wave (mmW) targeted for high carrier frequencies (e.g., 25 GHz or above), massive machine type communication (mMTC) targeted for non-backward compatible MTC technologies, and / or mission critical targeted for ultra-reliable low latency communication (URLLC). These services can include latency and reliability requirements. These services can also have different transmission time intervals (TTIs) to meet the corresponding quality of service (QoS) requirements. Additionally, these services can coexist in the same subframe.

[0035] Figure 1 An exemplary wireless communication network 100 is shown in which aspects of the present disclosure may be performed. For example, UE 120a may be configured to perform operation 1200 described below with reference to Figure 12 while base station 110a may be configured to perform Figure 13 operation 1300.

[0036] As Figure 1 shown, wireless communication network 100 may include multiple base stations (BSs) 110a-z (each also referred to herein individually as BS 110 or collectively as BS 110) and other network entities. In aspects of the present disclosure, a roadside service unit (RSU) may be considered a type of BS, and BS 110 may be referred to as an RSU. BS 110 may provide communication coverage for a particular geographic area (which is sometimes referred to as a “cell”), and the cell may be stationary or may move according to the location of the mobile BS 110. In some examples, BS 110 may be interconnected with each other and / or interconnected to one or more other BSs or network nodes (not shown) in wireless communication network 100 via various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.) using any suitable transport network. In Figure 1In the example shown, BS 110a, BS 110b, and BS 110c can be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x can be a pico BS for pico cell 102x. BS 110y and BS 110z can be femto BSs for femto cells 102y and 102z, respectively. A BS can support one or more cells. BS 110 communicates with user equipment (UE) 120a - y in wireless communication network 100 (each also individually referred to herein as UE 120 or collectively as UE 120). UE 120 (e.g., 120x, 120y, etc.) can be dispersed throughout wireless communication network 100, and each UE 120 can be fixed or mobile.

[0037] Wireless communication network 100 can also include a relay UE (e.g., relay UE 110r), also referred to as a repeater, etc., which receives a transmission of data and / or other information from an upstream station (e.g., BS 110a or UE 120r) and sends the transmission of the data and / or other information to a downstream station (e.g., UE 120 or BS 110), or relays transmissions between UE 120s to facilitate communication between devices.

[0038] Network controller 130 can be coupled to a set of BSs 110 and provide coordination and control for these BSs 110. Network controller 130 can communicate with these BSs 110 via a backhaul. BSs 110 can also communicate with each other (e.g., directly or indirectly) via a wireless backhaul or a wired backhaul.

[0039] UE 120 (e.g., UE 120x, UE 120y, etc.) can be dispersed throughout the wireless communication network 100, and each UE can be stationary or mobile. A UE can also be referred to as a mobile station, terminal, access terminal, user unit, station, customer premise equipment (CPE), cellular phone, smart phone, personal digital assistant (PDA), wireless modem, wireless communication device, handheld device, laptop computer, cordless phone, wireless local loop (WLL) station, tablet computer, camera, gaming device, netbook, smartbook, ultrabook, home appliance, medical device or apparatus, biosensor / device, wearable devices such as smart watches, smart clothes, smart glasses, smart bracelets, smart jewelry (e.g., smart rings, smart bracelets, etc.), entertainment devices (e.g., music devices, video devices, satellite radio, etc.), vehicle components or sensors, smart meters / sensors, industrial manufacturing equipment, global positioning system devices, or any other suitable device configured to communicate via wireless or wired media. Some UEs can be considered machine type communication (MTC) devices or evolved MTC (eMTC) devices. For example, MTC and eMTC UEs include robots, drones, remote devices, sensors, meters, monitors, location tags, etc. that can communicate with a BS, another device (e.g., a remote device), or some other entity. A wireless node can provide connectivity to a network or to the network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link, for example. Some UEs can be considered Internet of Things (IoT) devices, which can be narrowband IoT (NB-IoT) devices.

[0040] Some wireless networks (e.g., LTE) utilize Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and Single Carrier Frequency Division Multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM divide the system bandwidth into multiple (K) orthogonal subcarriers, where these subcarriers are also commonly referred to as tones, frequency bins, etc. Each subcarrier can be modulated with data. Typically, modulation symbols are transmitted using OFDM in the frequency domain and SC-FDM in the time domain. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers (K) can depend on the system bandwidth. For example, the subcarrier spacing can be 15 kHz, and the minimum resource allocation (which is called a "resource block" (RB)) can be 12 subcarriers (or 180 kHz). Thus, for system bandwidths of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), the nominal Fast Fourier Transform (FFT) size can be equal to 128, 256, 512, 1024, or 2048, respectively. The system bandwidth can also be divided into subbands. For example, one subband can cover 1.08 MHz (i.e., 6 resource blocks), and for system bandwidths of 1.25, 2.5, 5, 10, or 20 MHz, there can be 1, 2, 4, 8, or 16 subbands, respectively.

[0041] Although aspects of the examples described herein are associated with LTE technology, aspects of the present disclosure can be applicable to other wireless communication systems (e.g., NR). NR can utilize OFDM with a cyclic prefix (CP) on both the uplink and downlink, including support for half-duplex operation using TDD. Beamforming can be supported, and the beam direction can be configured dynamically. MIMO transmission with precoding can also be supported. The MIMO configuration in the DL can support up to 8 transmit antennas in the case of multi-layer DL transmission of up to 8 streams and up to 2 streams per UE. Multi-layer transmission of up to 2 streams per UE can be supported. Aggregation of multiple cells with up to 8 serving cells can be supported.

[0042] In some examples, access to the air interface can be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication between some or all of the devices and equipment within its serving area or cell. The scheduling entity can be responsible for scheduling, allocating, reconfiguring, and releasing resources for one or more subordinate entities. That is, for the scheduled communication, the subordinate entities can utilize the resources allocated by the scheduling entity. The base station is not the only entity that can act as a scheduling entity. In some examples, a UE can act as a scheduling entity and can schedule resources for one or more subordinate entities (e.g., one or more other UEs), and the other UEs can utilize the resources scheduled by the UE for wireless communication. In some examples, a UE can act as a scheduling entity in a peer-to-peer (P2P) network and / or a mesh network. In the mesh network example, the UEs can communicate directly with each other in addition to communicating with the scheduling entity.

[0043] In Figure 1 it, the solid line with double arrows represents the desired transmission between the UE and the serving BS, which is the BS designated to serve the UE on the downlink and / or uplink. The thin dashed line with double arrows indicates the interfering transmission between the UE and the BS.

[0044] Figure 2 depicts an exemplary logical architecture of a distributed radio access network (RAN) 200 that can be implemented in the Figure 1 wireless communication network 100 shown. The 5G access node 206 can include an access node controller (ANC) 202. The ANC 202 can be the central unit (CU) of the distributed RAN 200. The backhaul interface for the next generation core network (NG-CN) 204 can terminate at the ANC 202. The backhaul interface for an adjacent next generation access node (NG-AN) 210 can terminate at the ANC 202. The ANC 202 can include one or more TRPs 208 (e.g., cells, BSs, gNBs, etc.).

[0045] The TRP 208 can be a distributed unit (DU). The TRP 208 can be connected to a single ANC (e.g., ANC 202) or more than one ANC (not shown). For example, for RAN sharing, radio as a service (RaaS), and service-specific AND deployments, the TRP 208 can be connected to more than one ANC. Each TRP 208 can include one or more antenna ports. The TRP 208 can be configured to serve traffic for a UE either individually (e.g., dynamically selected) or jointly (e.g., joint transmission).

[0046] The logical architecture of the distributed RAN 200 can support fronthauling solutions across different deployment types. For example, the logical architecture can be based on the transmit network capabilities (e.g., bandwidth, latency, and / or jitter).

[0047] The logical architecture of the distributed RAN 200 can share features and / or components with LTE. For example, the next-generation access node (NG-AN) 210 can support dual connectivity with NR and can share a common backhaul for LTE and NR.

[0048] The logical architecture of the distributed RAN 200 can enable cooperation between and within the TRPs 208. For example, cooperation can be achieved via the ANC 202, within and / or across the TRPs. The inter-TRP interface may not be used.

[0049] Logical functions can be dynamically distributed in the logical architecture of the distributed RAN 200. The radio resource control (RRC) layer, packet data convergence protocol (PDCP) layer, radio link control (RLC) layer, media access control (MAC) layer, and physical (PHY) layer can be adaptively arranged at the DU (e.g., TRP 208) or the CU (e.g., ANC 202).

[0050] Figure 3 In accordance with aspects of the present disclosure, an exemplary physical architecture of the distributed RAN 300 is shown. The centralized core network unit (C-CU) 302 can host core network functions. The C-CU 302 can be centrally deployed. The C-CU 302 functions can be offloaded (e.g., offloaded to advanced wireless services (AWS)) to handle peak capacity as much as possible.

[0051] The centralized RAN unit (C-RU) 304 can host one or more ANC functions. Optionally, the C-RU 304 can locally host core network functions. The C-RU 304 can have a distributed deployment. The C-RU 304 can be close to the network edge.

[0052] The DU 306 can host one or more TRPs (edge node (EN), edge unit (EU), radio head (RH), smart radio head (SRH), etc.). The DU can be located at the edge of the network with radio frequency (RF) capabilities.

[0053] Figure 4 BS 110a and UE 120a are shown (as Figure 1Exemplary components (depicted in ) that can be used to implement aspects of the present disclosure. For example, the antennas 452, processors 466, 458, 464, and / or controller / processor 480 of the UE 120a can be used to perform the various techniques and methods described herein with reference to Figure 12 and the antennas 434, processors 420, 430, 438, and / or controller / processor 440 of the BS 110a can be used to perform the various techniques and methods described herein with reference to Figure 13 described.

[0054] At the BS 110a, the transmit processor 420 can receive data from the data source 412 and control information from the controller / processor 440. The control information can be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data can be for the physical downlink shared channel (PDSCH), etc. The processor 420 can process the data and control information (e.g., encoding and symbol mapping) to obtain data symbols and control symbols, respectively. The processor 420 can also generate reference symbols, e.g., for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and cell-specific reference signal (CRS). The transmit (TX) multiple-input multiple-output (MIMO) processor 430 can perform spatial processing (e.g., precoding) on these data symbols, control symbols, and / or reference symbols (if any) and provide an output symbol stream to the modulators (MOD) 432a to 432t. Each modulator 432 can process its respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator can further process (e.g., convert to an analog signal, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. The downlink signals from the modulators 432a to 432t can be transmitted via the antennas 434a to 434t, respectively.

[0055] At UE 120a, antennas 452a through 452r may receive downlink signals from base station 110a and provide the received signals to a demodulator (DEMOD) in transceivers 454a through 454r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, down-convert, and digitize) the respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 456 may obtain the received symbols from all demodulators 454a through 454r, perform MIMO detection (if any) on the received symbols, and provide the detected symbols. A receive processor 458 may process (e.g., demodulate, de-interleave, and decode) the detected symbols, provide decoded data for UE 120a to data sink 460, and provide decoded control information to controller / processor 480.

[0056] On the uplink, at UE 120a, a transmit processor 464 may receive data (e.g., for a physical uplink shared channel (PUSCH)) from a data source 462, receive control information (e.g., for a physical uplink control channel (PUCCH)) from controller / processor 480, and process the data and control information. The transmit processor 464 may also generate reference symbols for reference signals (e.g., for sounding reference signals (SRS)). Symbols from the transmit processor 464 may be precoded (if any) by a TX MIMO processor 466, further processed (e.g., for SC-FDM, etc.) by a demodulator in transceivers 454a through 454r, and sent back to base station 110a. At BS 110a, the uplink signal from UE 120a may be received by an antenna 434, processed by a modulator 432, detected (if any) by a MIMO detector 436, and further processed by a receive processor 438 to obtain decoded data and control information transmitted by UE 120a. The receive processor 438 may provide the decoded data to a data sink 439 and provide the decoded control information to controller / processor 440.

[0057] In some environments, two or more secondary entities (e.g., UEs) may communicate with each other using sidelink signals. Practical applications of such sidelink communications may include public safety, proximity services, UE-to-network relay, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical grids, and / or various other suitable applications. Generally, a sidelink signal may refer to a signal transmitted from one secondary entity (e.g., UE1) to another secondary entity (e.g., UE2) without relaying the communication through a scheduling entity (e.g., UE or BS), even though the scheduling entity may be used for scheduling and / or control purposes. In some examples, licensed spectrum may be used to transmit sidelink signals (as opposed to wireless local area networks (WLANs) which typically use unlicensed spectrum).

[0058] Example UE-to-NW Relay

[0059] Aspects of the present disclosure relate to remote UEs, relay UEs, and networks, as Figure 5 shown in Figure 5 is a high-level path diagram showing example connection paths: the Uu path (cellular link) between the relay UE and the network gNB, and the PC5 path (D2D link) between the remote UE and the relay UE. The remote UE and the relay UE may be in radio resource control (RRC) connected mode.

[0060] As Figure 6 and Figure 7 shown in, the remote UE may generally connect to the relay UE via a layer 3 (L3) connection that is Uu connectionless (and invisible) to the network or via a layer 2 (L2) connection, where the UE supports Uu access stratum (AS) and non-AS connection (NAS) to the network.

[0061] Figure 6 is an example block diagram of a control plane protocol stack on L3 in the case where there is no direct connection path (Uu connection) between the remote UE and the network node. In this case, the remote UE does not have a Uu connection to the network and is connected to the relay UE only via a PC5 connection (e.g., layer 3 UE-to-NW). In some implementations, the relay UE may require PC5 unicast link setup to serve the remote UE. The remote UE may not have a Uu application server (AS) connection to the radio access network (RAN) via the relay path. In other cases, the remote UE may not have a direct non-access stratum (NAS) connection to the 5G core network (5GC). The relay UE may report the presence of the remote UE to the 5GC. Alternatively and optionally, the remote UE may be visible to the 5GC via a non-3GPP interworking function (N3IWF).

[0062] Figure 7It is an example block diagram of the control plane protocol stack on L2 when there is a direct connection path between the remote UE and the network node. This control plane protocol stack refers to the L2 relay option based on the NR-V2X connection. Both the PC5 control plane (C plane) and the NR Uu C plane are on the remote UE, similar to Figure 6 that shown. The PC5 C plane can establish a unicast link before relaying. The remote UE can support the NR Uu AS and NAS connections on top of the PC5 radio link control (RLC). The NG-RAN can control the PC5 link of the remote UE via the NR radio resource control (RRC). In some embodiments, an adaptation layer may be required to support multiplexing of multiple UE services on the Uu connection of the relay UE.

[0063] Some systems (e.g., NR) can support the stand-alone (SA) capability of UE-to-network and UE-to-UE relay communication based on sidelink (e.g., as described above, using layer 3 (L3) and layer 2 (L2) relay).

[0064] The specific relay process may depend on whether the repeater is an L3 or L2 relay. Figure 8 An example dedicated PDU session for L3 relay is shown. In the scenario shown, the remote UE establishes a PC5-S unicast link setup and obtains an IP address. The PC5-RRC is used to manage the PC5 unicast link AS configuration. The relay UE and the remote UE coordinate on the AS configuration. The relay UE can consider information from the RAN to configure the PC5 link. The authentication / authorization for the remote UE to access the relay can be completed during the PC5 link establishment. In the example shown, the relay UE performs L3 relay.

[0065] Figure 9 An example dedicated PDU session for L2 relay is shown. In the scenario shown, there is no PC5 unicast link setup before relaying. The remote UE broadcasts a control channel (SBCCH) over the sidelink and sends NR RRC messages on the PC5 signaling radio bearer (SRB). The RAN can independently indicate the PC5 AS configuration to the remote UE and the relay UE via the NR RRC message. Changes can be made to the NR V2X PC5 stack operation to support radio bearer processing in NR RRC / PDCP, but support the corresponding logical channels in the PC5 link. In L2 relay, the PC5 RLC may need to support direct interaction with the NR PDCP.

[0066] Generally, before the remote UE connects to the relay, it follows the traditional UE idle / inactive behavior in NR Rel-16 (i.e., receiving Uu paging, monitoring Uu SIB, and triggering RRC setup when receiving Uu paging).

[0067] After a remote UE connects to a relay (i.e., PC5 RRC is established), it can be configured to receive paging and SIBs from the relay for better coverage. Before connecting to the relay, the remote UE can be in an idle / inactive / out-of-coverage (OOC) state. The network can configure the relay node to also monitor paging for the remote UE. In this case, the remote UE can stop monitoring paging and SIB reception (for coverage and power saving). After receiving the paging for the remote UE, the relay UE can notify the remote UE via a dedicated PC5 RRC message (e.g., there is no need to introduce a new message). The remote UE can trigger RRC setup / resumption and perform unified access control (UAC). After receiving the updated SIBs, the relay UE forwards them to the remote UE via a dedicated PC5 RRC message. The remote UE may be interested only in certain specific SIBs. In the previous discussion, the reference to the RRC state refers to the Uu RRC state.

[0068] The sidelink relay DRX scenario needs to address various issues. One issue involves support for relay discovery by the remote UE sidelink DRX. In some cases, an assumption for relay discovery is that the relay UE is only in the connected mode, rather than the idle / inactive mode. The remote UE can be in the connected, idle / inactive, or out-of-coverage (OOC) state.

[0069] Mechanisms can also be provided for relay selection and reselection. Relay selection generally refers to the process where a remote UE that is not connected to any relay node discovers relay nodes whose sidelink discovery reference signal received power (SD-RSRP) is higher than a threshold level (possibly a certain quantity) and selects the relay node with the best SD-RSRP from among them. Relay reselection generally refers to the process where a remote UE that has already been connected to a relay node (e.g., has performed relay selection) discovers relay nodes whose SD-RSRP is higher than a threshold level (possibly a certain quantity) when the SD-RSRP of the current relay node is lower than the threshold level and selects the relay node with the best SD-RSRP from among them.

[0070] Discovery for relay selection and reselection can be supported. Different types of discovery models can be supported. For example, Figure 10A The first model (referred to as model A discovery) is shown. In this case, the UE sends discovery messages (e.g., notifications), and other UEs monitor such discovery messages.

[0071] In some cases, the relay service code may identify the connection service provided by a relay UE (e.g., a ProSe relay UE). The relay service code may be pre-configured or provided to the UE by a Policy Control Function (PCF), for example. In some cases, security information for discovery messages may be provided during a key management process. A remote UE may discover the relay UE by monitoring only the corresponding relay service code.

[0072] According to Figure 10B In the second model (referred to as Model B discovery) shown in, the UE (the discoverer) sends a request message and waits for a response from the monitoring UE (the discovered). Such discovery messages may be sent on the PC5 communication channel (e.g., rather than on a separate discovery channel). The discovery message may be carried within the same layer 2 frame as the frame used for other direct communications, e.g., which includes a destination layer 2 ID that may be set to a unicast, multicast, or broadcast identifier, a source layer 2 ID that is always set to the unicast identifier of the transmitter, and the frame type indicates that it is a ProSe direct discovery message.

[0073] As described above, for relay selection, the remote UE is not connected to any relay nodes (i.e., no PC5 unicast link is established between the remote UE and the relay node). In this case, it may be desirable to design a DRX mode to reduce the power consumption of the remote UE while monitoring relay discovery messages for relay selection.

[0074] As described above, for relay reselection, the remote UE is already connected to at least one relay node (e.g., a PC5 unicast is established between the remote UE and the relay node). For relay reselection, it may be desirable to design a DRX configuration that helps reduce the power consumption of the remote UE while monitoring relay discovery messages for relay reselection and PC5 data transmission.

[0075] Figure 11 An example environment is shown in which a network entity provides services to a remote UE via a UE-to-network relay (e.g., a relay UE). To communicate via the relay UE, a remote UE that is not yet connected to a relay node may discover the relay nodes and select one or more of these relay nodes as relays for the remote UE. For example, the remote UE may discover all relay nodes whose sidelink discovery reference signal received power (SD-RSRP) is higher than a first threshold (e.g., exceeding minHyst which is higher than q-Rx-Lq-Rx-LevevMin). When the remote UE is already connected to a relay node, the remote UE may also reselect a relay. To do so, the remote UE may determine that the sidelink RSRP (SL-RSRP) is lower than a second threshold (e.g., above minHyst which is lower than q-Rx-LevMin), and based on this determination, discover relay nodes whose SD-RSRP is higher than the first threshold.

[0076] Example RRC Re - establishment and RLF Reporting in a Sidelink Relay System

[0077] In an L2 relay system (e.g., the system described in reference Figure 9 ), a potential problem is that when an RLF (e.g., PC5 RLF) is detected in a remote UE, the current RRC connection to the network is lost. Currently, there is no specified procedure for re - establishing the RRC connection.

[0078] However, aspects of the present disclosure provide techniques for re - establishing an RRC connection between a remote UE and a network entity after the remote UE has detected a radio link failure (RLF).

[0079] As will be described herein, upon detecting an RLF on Uu and / or PC5, the remote UE can attempt RRC connection re - establishment by performing cell selection and / or relay selection (since the RLF can effectively render the relay UE and / or the current serving cell unsuitable).

[0080] Thus, the techniques proposed herein can cover the case where the remote UE declares a Uu RLF (including a handover failure from PC5 to Uu), and the case where the remote UE declares a PC5 RLF (including a handover failure from Uu to PC5 or from PC5 to Uu). As will be described in more detail below, in both cases, the remote UE can trigger different solutions based on joint cell selection and relay selection, and can perform such tat RRC re - establishment directly via Uu or via a relay (indirectly).

[0081] Generally, a remote UE can declare a Uu RLF based on multiple conditions (e.g., conditions occurring within a radio link monitoring (RLM) timer (e.g., T310)). For example, an RLF may occur when the maximum re - transmission count of radio link control (RLC) is reached. As another example, an RLF may occur when the maximum number of random access channel (RACH) preamble (re) - transmissions occur, a Uu security failure occurs, or a re - configuration failure occurs.

[0082] Generally, a (remote or relay) UE may declare a PC5 RLF based on multiple conditions. For example, RLF may occur when the maximum retransmission count of radio link control (RLC) is reached. Another condition may be reconfiguration failure (e.g., T400 expiration). As another example, RLF may occur when the maximum number of consecutive hybrid automatic repeat request (HARQ) discontinuous transmissions (DTX) to a destination is reached. Additionally, RLF may occur when a PC5 Internet Protocol (IP) check fails. It should be noted that each of the conditions mentioned above may be an RLF detected by transmission (TX) or an RLF detected by reception (RX).

[0083] After declaring a PC5 RLF, the access stratum (AS) of the UE may send a PC5 RLR indication including the PC5 link identifier to the upper stratum (e.g., the vehicle-to-everything (V2X) stratum) to indicate the PC5 unicast link for which the RLF declaration has been made, and release the PC5 radio resource control (RRC) connection. If the UE is in the connected mode, the UE may report to the network entity whether RLF and / or reconfiguration failure has occurred.

[0084] In some cases of RLF, joint cell (re)selection and / or relay (re)selection may be completed before or after the remote UE connects to the relay UE. In the case before the remote UE connects to the relay UE, the remote UE may first perform cell (re)selection (e.g., attempt to search for and camp on a "suitable" cell). If the cell (re)selection process fails (e.g., the remote UE cannot find any "suitable" cell), the remote UE considers it to be out of coverage and starts the relay selection process.

[0085] After the remote UE connects to the relay UE, there may be multiple options. For example, if at least one "suitable" relay is available, the remote UE may only perform relay (re)selection (i.e., not perform cell (re)selection). In other cases, the remote UE may consider the relay UE as an inter-radio access technology (RAT) cell and thus perform joint cell reselection and relay reselection. In this case, the remote UE performs a relay reselection process to ensure that the connected relay is "suitable" and has the highest sidelink reference signal received power (SL-RSRP). Additionally, the remote UE may consider the relay to which it is connected as its serving cell, and the remote UE may calculate the cell ranking criterion R Hyst based on the SL-RSRP and / or sidelink reference signal received quality (SL-RSRQ) and the hysteresis parameter Q broadcast by the relay sIn addition, the remote UE may consider all Uu cells as neighboring cells, and the remote UE may perform a cell reselection process and calculate the cell ranking criterion R based on their RSRP / RSRQ and Q broadcast by these cells. offset to calculate the cell ranking criterion R n In another case, the remote UE may rank the cells according to the best relay that can be used to connect to the cell, and the remote UE may consider the relay downlink (DL) signal quality as a proxy for the cell.

[0086] As described above, aspects of the present disclosure provide techniques for reconstructing an RRC connection between a remote UE and a network entity after the remote UE has detected a radio link failure (RLF).

[0087] Accordingly, certain aspects of the present disclosure provide techniques for reconstructing an RRC connection after RLF. As will be described in more detail, the remote UE may be configured to reconstruct the RRC connection by first attempting to find a suitable cell, first attempting to find a suitable relay, or searching for a suitable cell and a suitable relay simultaneously. The exact messaging for reconstructing the RRC connection may depend on whether a suitable cell or a suitable relay is found first. If a suitable cell is found first, the remote UE may send an RRC reconstruction request directly to the network (e.g., to the gNB of the suitable cell). If a suitable cell is found first, the remote UE may send an RRC reconstruction request to the network via the suitable cell.

[0088] Figure 12 According to aspects of the present disclosure, an example operation 1200 for wireless communication of a remote UE is shown. For example, operation 1200 may be performed by Figure 1 or Figure 4 UE 120a (acting as a remote UE) to reconstruct an RRC connection lost due to RLF.

[0089] Operation 1200 begins at 1202 by detecting a radio link failure (RLF) that causes a loss of radio resource control (RRC) connection with a first network entity on at least one of a first link between a first relay UE and a first network entity or a second link between the remote UE and the first relay UE. At 1204, the relay UE attempts to reconstruct the RRC connection with the first network entity or a second network entity by performing at least one of relay selection or cell selection.

[0090] For example, the remote UE may detect a PC5 or Uu RLF, and to reconstruct the RRC connection, may perform joint cell selection and relay selection, as described in more detail below (refer to Figures 14 - 17 ). The units for performing the functions of 1202 and 1204 may but need not include, for example, refer toFigure 4 antenna 452, transceiver 454, receiving processor 458, controller / processor 480, etc. and / or reference Figure 18 transceiver 1808, antenna 1810, and / or processing system 1802 of

[0091] Figure 13 illustrates an example operation 1300 of complementary wireless communication that can be considered Figure 12 of operation 1200. For example, operation 1300 can be performed by Figure 1 or Figure 4 BS 110 of Figure 12 to participate in the RRC connection re - establishment of the remote UE that performs operation 1200 of

[0092] Operation 1300 starts at 1302, receiving a Radio Resource Control (RRC) re - establishment request message from a remote user equipment (UE). For example, as described in more detail below (reference Figures 14 - 17 ), the network entity can receive the RRC re - establishment connection directly or (indirectly) via a relay.

[0093] At 1304, the network entity determines whether the remote UE was previously connected to the network entity or another network entity via a first relay UE. At 1306, if the UE was previously connected to another network entity, the network entity retrieves the context of the remote UE from the other network entity. At 1308, the network entity sends an RRC re - establishment message or an RRC setup message to the remote UE.

[0094] The unit for performing the functions of 1302, 1304, 1306, and 1308 may or may not include, for example, the unit for performing the function of 1104 may or may not include, for example, reference Figure 4 antenna 434, transceiver 432, receiving processor 438, transmitting processor 420, controller / processor 440, etc. and / or reference Figure 19 transceiver 1908, antenna 1910, and / or processing system 1902 of

[0095] In some cases, upon detecting RLF, the remote UE can attempt RRC connection re - establishment by performing joint cell selection and relay selection (e.g., simultaneously). In this case, the remote UE has no preference for re - establishing the RRC via the gNB or the relay UE. Therefore, in this case, as long as a suitable cell or a suitable relay is available, the remote UE can initiate the RRC re - establishment process.

[0096] In this case, when RLF is declared, the remote UE may start a timer (e.g., T311 associated with the cell selection procedure) and may perform cell selection and relay selection simultaneously. If T311 expires, the remote UE may enter the RRC idle state.

[0097] If a suitable cell is found first (e.g., before the T311 timer expires), the remote UE may stop the timer and start the RRC reestablishment procedure (and start the T301 timer for RRC connection reestablishment) by sending an RRCReestablishmentRequest message directly to the gNB. On the other hand, if a suitable relay is selected first (before a suitable cell is found and before the T311 timer expires), the remote UE may stop the T311 timer and start the RRC reestablishment procedure (and may start the T301 timer) by sending an RRCReestablishmentRequest message to the gNB via forwarding through the selected relay.

[0098] On the gNB side, after receiving the RRCReestablishmentRequest message, the specific actions taken may depend on whether the reestablished gNB (the gNB with which the RRC connection is reestablished) was connected before. For example, if the reestablished gNB is the gNB that was previously connected to the remote UE, the UE context retrieval procedure may not be required. On the other hand, if the reestablished gNB is a new gNB, the gNB may trigger a UE context retrieval procedure with the old gNB (the gNB that was previously connected at the time of detecting RLF).

[0099] In either case, if the reestablishment procedure is successful, the reestablished gNB may send an RRCReestablishment message to the remote UE via the previous route (i.e., directly or via a relay). If the reestablishment is unsuccessful, the reestablished gNB may send an RRCSetup message to the remote UE via the previous route (i.e., directly or via a relay).

[0100] If the remote UE receives an RRCReestablishment message before the T301 timer expires, the remote UE may consider the RRC reestablishment procedure as successful. In this case, the remote UE may send an RRCReestablishmentComplete message to the reestablished gNB via the previous route (i.e., directly or via a relay). On the other hand, if an RRCSetup message is received before the T301 timer expires, the remote UE may send an RRCSetupComplete message to the gNB via the previous route (i.e., directly or via a relay).

[0101] Figures 14 - 17 Illustrates an example scenario where a remote UE that has detected PC5 RLF re - establishes RRC. These example scenarios differ in whether the remote UE re - establishes the RRC connection with the same or a new gNB and the same or a new relay. The processes shown can be applied to the NG interface and cross - RAT context retrieval.

[0102] Figure 14 Illustrates an example scenario where a remote UE that has detected PC5 RLF re - establishes an RRC connection with the same gNB via a new relay. As shown, in this case, the remote UE can send an RRCReestablishmentRequest message via a relay with a default configuration (PHY / MAC / RLC / adaptation layer configuration). In this case, as described above, the RRCReestablishment and RRCReestablishmentComplete messages can use the same routing as the RRCReestablishmentRequest message.

[0103] After receiving the RRCReestablishmentComplete, the gNB can re - configure the RLC and adaptation layer configurations for the new relay and the remote UE. After receiving the RRCReestablishmentComplete, the gNB can also release the old relay adaptation layer configuration associated with the remote UE (via RRCReconfiguration).

[0104] Figure 15 Illustrates an example scenario where a remote UE re - establishes RRC with a different gNB (different from the gNB that served the remote UE when the RLF was detected). Different from the example in Figure 14 , in this case, after receiving the RRCReestablishmentRequest message, the re - established gNB triggers a UE context acquisition process to obtain the upper - layer configuration (i.e., PDCP layer and above) of the remote UE from the previous gNB.

[0105] As shown, after receiving the RRCReestablishmentComplete, the new gNB can send a release context message to the old gNB. After receiving the release context message, the old gNB can release the relay adaptation layer configuration associated with the remote UE (e.g., via RRCReconfiguration).

[0106] Figure 16Illustrates an example scenario where a remote UE re - establishes RRC directly with a new gNB and different relays to re - establish RRC. Relative to Figure 14 and Figure 15 In the example shown, the difference is that upon receiving the RRCReestablishmentComplete message, the new gNB sends a release context message to the old gNB, and the old gNB releases the adaptation layer configuration of the remote UE.

[0107] Figure 17 Illustrates an example scenario where a remote UE re - establishes RRC with a new gNB via a new relay. Relative to Figures 14 - 16 In this case, in the example shown, when the RRCReestablishmentComplete message is received, the gNB re - configures the RLC and adaptation layer configurations of the new relay and the remote UE.

[0108] In some cases, the remote UE can be configured to prefer cell selection or relay selection when attempting to re - establish an RRC connection after RLF.

[0109] For example, by first performing cell selection, the remote UE can have a preference for re - establishing RRC via the gNB. Thus, in this case, the remote UE can first trigger cell selection using only a new timer (e.g., new timer T391). In this case, the remote UE can trigger relay selection only when the new timer T391 expires.

[0110] Upon detecting RLF, the remote UE can start the T391 timer and perform only cell selection. If a suitable cell is selected first (before the T391 timer expires), the remote UE can stop the T391 timer and start the RRC re - establishment process by directly sending an RRCReestablishmentRequest message to the gNB (and start the T301 timer and perform the remaining operations described in the example above for the UE performing joint cell and relay selection (simultaneously)).

[0111] In some cases, if the T391 timer expires, the remote UE can start the T311 timer while performing cell selection and relay selection (e.g., resume or “fall back” to the joint selection example described above).

[0112] On the other hand, by first performing relay selection, the remote UE can give a preference for re - establishing an RRC connection via a relay. In this case, the remote UE first triggers cell selection using only a new timer (e.g., new timer T392), and triggers cell selection only when the new timer T393 expires.

[0113] In this case, when RLF is detected, the remote UE starts T392 and only performs relay selection. If a suitable relay is selected first (before the T392 timer expires), the remote UE stops the T392 timer and starts the RRC reestablishment procedure by sending an RRCReestablishmentRequest message to the gNB for forwarding via the selected relay, and starts T301. If T392 expires, the remote UE starts T311 and simultaneously performs cell selection and relay selection, returning again to the combined selection example described above.

[0114] In some cases, the UE may utilize a resource set (referred to as an exception pool), which generally refers to the resource set used by the UE during transmission between RRC idle and connected states. The remote UE may be allowed to use the resources of the exception pool for sidelink transmission during the period from RLF detection to RRC reestablishment. For example, when the T311 / T391 timer is running, the remote UE may use the exception pool provided by the cell (faulty cell) in which RLF is detected. When the T301 timer is running, the remote UE may use the exception pool provided by the cell in which the remote UE initiates reestablishment.

[0115] In some cases, the UE may be configured to perform cell selection and relay selection jointly, prioritize cell selection, or prioritize relay selection. For example, the remote UE may be configured by the network via RRCreconfiguration or system information (SIB), preconfigured, or configured via the Policy Control Function (PCF). In some cases, certain preferences may be used in certain scenarios (e.g., relay selection may be performed first in the case of PC5 RLF).

[0116] In some cases, after the remote UE has an RRC connection (reestablishment) with the gNB, the remote UE may report a PC5 RLF report to the gNB. For example, the RRC connection may be via RRCReestablishment or RRCSetup, and the remote UE may include the PC5 RLF report in the Uu UEinformationResponse message. In this case, the UE may indicate the availability of the PC5 RLF report, for example, in the RRCSetupComplete or RRCReestablishmentComplete message.

[0117] The PC5 RLF report can be sent directly or via a relay to the gNB (e.g., if the RRC connection is re - established via a relay). The PC5 RLF report can include various contents, such as the RLF cause, the remote UE ID, and / or available sidelink reference signal received power (SL - RSRP) measurements and Uu measurements.

[0118] Figure 18 A communication device 1800 is shown that can include various components (e.g., corresponding to unit functional components), where these components are configured to perform the operations of the techniques disclosed herein (e.g., Figure 12 the operations shown in Figure 1 ). For example, the communication device 1800 can be a UE 180 (e.g., Figure 4 as shown in Figure 4 ). The communication device 1800 includes a processing system 1802 coupled to a transceiver 1808 (e.g., the transceiver 1808 is an example of the transceiver 454 of Figure 4 ). The transceiver 1808 is configured to transmit and receive signals for the communication device 1800 via an antenna 1810 (e.g., the antenna 1810 is an example of the antenna 452 of

[0119] The processing system 1802 includes a processor 1804 (e.g., the processor 1804 is an example of one of the processors 458, 464, 466, and 480 of Figure 4 coupled to a computer - readable medium / memory 1812 via a bus 1806 (e.g., the medium / memory 1818 is an example of the memory 482 of Figure 4 ). In some aspects, the computer - readable medium / memory 1812 is configured to store instructions (e.g., computer - executable code) that, when executed by the processor 1804, cause the processor 1804 to perform Figure 12The operations shown or other operations for performing the various techniques discussed herein. In some aspects, the computer-readable medium / memory 1812 stores: code 1814 for detecting a radio link failure (RLF) that causes a radio resource control (RRC) connection loss on at least one of a first link between a first relay UE and a first network entity or a second link between a remote UE and the first relay UE; and code 1816 for attempting to reconstruct the RRC connection by performing at least one of relay selection or cell selection. In some aspects, the processor 1804 has circuitry configured to implement the code stored in the computer-readable medium / memory 1812. The processor 1804 includes: circuitry 1820; circuitry 1822 for attempting to reconstruct the RRC connection by performing at least one of relay selection or cell selection. The circuitry 1820 and / or 1822 can be specially designed circuitry for performing the indicated functions or can be general-purpose circuitry configured or programmed to perform these functions.

[0120] Figure 19 A communication device 1900 is shown that can include various components (e.g., corresponding to unit functional components), where these components are configured to perform the operations of the techniques disclosed herein (e.g., Figure 19 the operations shown in). For example, the communication device 1900 can be a BS 110 (e.g., Figure 1 or Figure 4 as shown in). The communication device 1900 includes a processing system 1902 coupled to a transceiver 1908 (e.g., the transceiver 1908 is an example of the transceiver 432 of Figure 4 ). The transceiver 1908 is configured to transmit and receive signals for the communication device 1900 via an antenna 1910 (e.g., the antenna 1910 is an example of the antenna 434 of Figure 4 ), such as the various signals described herein. The processing system 1902 can be configured to perform the processing functions of the communication device 1900, which includes processing the signals received and / or to be transmitted by the communication device 1900.

[0121] The processing system 1902 includes a processor 1904 (e.g., the processor 1904 is an example of one of the processors 420, 430, 438, and 440 of Figure 4 ), coupled to a computer-readable medium / memory 1912 (e.g., the medium / memory 1912 is an example of the memory 442 of Figure 4 ) via a bus 1906. In some aspects, the computer-readable medium / memory 1912 is configured to store instructions (e.g., computer-executable code) that, when executed by the processor 1904, cause the processor 1904 to perform Figure 13The operations shown or other operations for performing the various techniques discussed herein. In some aspects, the computer-readable medium / memory 1912 stores: code 1914 for receiving a Radio Resource Control (RRC) reconstruction request message from a remote user equipment (UE); code 1916 for determining whether the remote UE was previously connected to a network entity or another network entity via a first relay UE; code 1918 for retrieving the context of the remote UE from the other network entity if the UE was previously connected to the other network entity; and code 1919 for sending an RRC reconstruction message or an RRC setup message to the remote UE. In some aspects, the processor 1904 has circuitry configured to implement the code stored in the computer-readable medium / memory 1912. The processor 1904 includes: circuitry 1920 for receiving a Radio Resource Control (RRC) reconstruction request message from a remote user equipment (UE); circuitry 1922 for determining whether the remote UE was previously connected to a network entity or another network entity via a first relay UE; circuitry 1924 for retrieving the context of the remote UE from the other network entity if the UE was previously connected to the other network entity; and circuitry 1926 for sending an RRC reconstruction message or an RRC establishment message to the remote UE. The circuitry 1920, 1922, 1924, and / or 1926 can be specially designed circuitry for performing the indicated functions or can be general-purpose circuitry configured or programmed to perform these functions.

[0122] The methods disclosed herein include one or more steps or acts for implementing these methods. Without departing from the scope of the present invention, these method steps and / or acts can be interchanged with each other. In other words, unless a specific order of steps or acts is specified, the order and / or use of specific steps and / or acts can be modified without departing from the scope of the present invention.

[0123] As used herein, the phrase referring to "at least one of" a list of items means any combination of these items, including a single member. For example, "at least one of a, b, or c" is intended to cover: a, b, c, a - b, a - c, b - c, and a - b - c, as well as any combination with multiple identical elements (e.g., a - a, a - a - a, a - a - b, a - a - c, a - b - b, a - c - c, b - b, b - b - b, b - b - c, c - c, and c - c - c or any other ordering of a, b, and c).

[0124] As used herein, the term "determine" encompasses a variety of actions. For example, "determine" can include calculating, computing, processing, deriving, researching, querying (e.g., querying a table, a database, or other data structure), ascertaining, and the like. Additionally, "determine" can also include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Further, "determine" can also include parsing, selecting, choosing, establishing, and the like.

[0125] To enable any ordinary person skilled in the art to implement the various aspects described herein, the various aspects have been described above. For an ordinary person skilled in the art, various modifications to these aspects are obvious, and the general principles defined herein can also be applied to other aspects. Therefore, the present invention is not limited to the aspects shown herein, but is consistent with the entire scope disclosed by the present invention, where, unless otherwise specified, modifying a component in the singular form does not mean "one and only one", but can be "one or more". Unless otherwise specifically stated, the term "some" refers to one or more. All structural and functional equivalents of the components of the various aspects described throughout this disclosure are expressly incorporated herein by reference and are intended to be covered by the claims, and these structural and functional equivalents are known or will be known to an ordinary person skilled in the art. Additionally, nothing disclosed herein is intended to be dedicated to the public, whether or not such disclosure is expressly recited in the claims. Further, no claim element should be construed in accordance with 35 U.S.C. § 112(f) unless the claim element is expressly recited using the phrase "functional module", or in a method claim, the claim element is recited using the phrase "functional step".

[0126] The various operations of the methods described above can be performed by any suitable unit capable of performing the corresponding functions. These units can include various hardware and / or software components and / or modules, including but not limited to: circuits, application specific integrated circuits (ASICs), or processors. Generally, where operations are shown in the figures, these operations can have corresponding paired functional module components numbered similarly. For example, Figures 12 - 13 the various operations shown in Figure 4 can be performed by the various processors shown in

[0127] A general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof can implement or perform the various exemplary logic blocks, modules, and circuits described in connection with the disclosure herein. The general-purpose processor may be a microprocessor, or, alternatively, the processor may be any commercially available processor, controller, microcontroller, or state machine. The processor may 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 such architecture.

[0128] When implemented in hardware, an exemplary hardware configuration may include a processing system in a wireless node. The processing system may be implemented using a bus architecture. Depending on the particular application and overall design constraints of the processing system, the bus may include any number of interconnected buses and bridges. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, etc., to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the physical layer. In the case of the user terminal 120 (see Figure 1 ), a user interface (e.g., keyboard, display, mouse, joystick, etc.) may also be connected to the bus. The bus also links various other circuits such as a clock source, peripherals, voltage regulators, power management circuits, etc., which are well known in the art and thus not described any further. The processor may be implemented using one or more general-purpose processors and / or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuits capable of executing software. Those of ordinary skill in the art will recognize how best to implement the described functions of the processing system in accordance with the particular application and overall design constraints imposed on the overall system.

[0129] When implemented using software, these functions can be stored on a tangible computer-readable medium or transmitted as one or more instructions or codes on a computer-readable medium. Software should be construed broadly to mean instructions, data, or any combination thereof, etc., whether it is referred to as software, firmware, middleware, microcode, hardware description language, or other terms. Computer-readable media include computer storage media and communication media, where communication media include any medium that facilitates the transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, which includes executing software stored on a machine-readable storage medium. The computer-readable storage medium may be coupled to the processor such that the processor can read information from and write information to the storage medium. Alternatively, the storage medium may also be part of the processor. For example, the machine-readable medium may include a transmission line, a carrier wave form modulated with data, and / or a computer-readable storage medium with instructions stored thereon that is separate from a wireless node, all of which can be accessed by the processor through a bus interface. Alternatively or additionally, the machine-readable medium or any part thereof may be part of the processor, for example, this may be the case with a cache and / or a general register file. For example, examples of the machine-readable medium may include RAM (Random Access Memory), flash memory, ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard disks, or any other suitable storage medium, or any combination thereof. The machine-readable medium can be embodied in a computer program product.

[0130] Software modules can include a single instruction or multiple instructions. Software modules can be distributed across several different code segments, across different programs, and across multiple storage media. The computer-readable medium can include multiple software modules. These software modules include instructions that, when executed by a device such as a processor, cause the processing system to perform various functions. Software modules can include a transmission module and a receiving module. Each software module can be located in a single storage device or distributed across multiple storage devices. For example, when a trigger event occurs, the software module can be loaded from a hard disk into RAM. During the execution of the software module, the processor can load some of these instructions into the cache to increase the access speed. Subsequently, one or more cache lines can be loaded into the general register file for execution by the processor. When referring to the functions of the following software modules, it should be understood that the functions are implemented by the processor when executing the instructions from the software module.

[0131] In addition, any connection can be properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), wireless, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, wireless, and microwave are included in the definition of the medium. As used herein, magnetic disks and optical disks include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray optical discs, where magnetic disks typically reproduce data magnetically, while optical discs reproduce data optically with a laser. Thus, in some aspects, a computer-readable medium can include a non-transitory computer-readable medium (e.g., a tangible medium). Additionally, for other aspects, a computer-readable medium can include a transitory computer-readable medium (e.g., a signal). Combinations of the above should also be included within the scope of protection of computer-readable media.

[0132] Accordingly, some aspects can include a computer program product for performing the operations presented herein. For example, the computer program product can include a computer-readable medium having instructions (and / or encoded with instructions) stored thereon that can be executed by one or more processors to perform the operations described herein. For example, instructions for performing the operations described herein and shown in Figures 12 - 13 are provided.

[0133] In addition, it should be understood that modules and / or other suitable units for performing the methods and techniques described herein can be downloaded and / or obtained on demand by a user terminal and / or a base station. For example, such a device can be coupled to a server to facilitate the transfer of units for performing the methods described herein. Alternatively, the various methods described herein can be provided by a storage unit (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or a floppy disk, etc.), such that when the user terminal and / or the base station couple or provide the storage unit to the device, the various methods can be obtained. Additionally, any other suitable technique for providing the methods and techniques described herein to the device can be utilized.

[0134] It should be understood that the present invention is not limited to the exact configurations and components shown above. Various modifications, changes, and variations can be made to the arrangements, operations, and details of the methods and apparatuses described above without departing from the scope of the present invention.

Claims

1. A method for wireless communication of a remote user equipment (UE), comprising: detecting a radio link failure (RLF) that causes a radio resource control (RRC) connection loss on at least one of a first link between a first relay UE and a first network entity or a second link between the remote UE and the first relay UE; and attempting to reconstruct the RRC connection by performing at least one of relay selection or cell selection and initializing a timer when starting to perform the at least one of the relay selection or the cell selection, wherein the performing further comprises: performing cell selection to search for a suitable cell; and if the timer expires before the remote UE finds a suitable cell, performing relay selection to search for a suitable relay; or performing relay selection to search for a suitable relay; and if the timer expires before the remote UE finds a suitable relay, performing cell selection to search for a suitable cell.

2. The method according to claim 1, wherein: the RLF includes an RLF on a link between the first network entity and at least one of the remote UE or the first relay UE; and the cause of the RLF relates to at least one of the following: start of a timer due to radio link monitoring (RLM), reaching the maximum number of retransmissions of radio link control (RLC), reaching the maximum number of retransmissions of a random access channel (RACH) preamble, security failure on a cellular link with a network entity, reconfiguration failure, or handover failure.

3. The method according to claim 1, wherein: the RLF includes an RLF on a link between the remote UE and the first relay UE; and the cause of the RLF relates to at least one of the following: reaching the maximum number of retransmissions of radio link control (RLC), expiration of a reconfiguration timer, reaching the maximum number of hybrid automatic repeat request (HARQ) transmissions, Internet protocol (IP) check failure, or handover failure.

4. The method according to claim 1, wherein, the performing includes: performing relay selection to search for a suitable relay and performing cell selection to search for a suitable cell.

5. The method according to claim 4, further comprising: if the remote UE finds a suitable cell before finding a suitable relay, the remote UE initiates an RRC re - establishment process by directly sending an RRC re - establishment request message to the network entity of the suitable cell; or if the remote UE finds a suitable relay before finding a suitable cell, the remote UE initiates an RRC re - establishment process by sending an RRC re - establishment request message to the network entity via the suitable relay.

6. The method according to claim 5, further comprising: receiving an RRC re - establishment message from at least one of the suitable cell or the suitable relay; and sending an RRC re - establishment complete message to the suitable cell or the suitable relay.

7. The method according to claim 1, wherein, If the timer expires before the remote UE finds a suitable cell, the remote UE performs both relay selection and cell selection.

8. The method according to claim 1, wherein, if the timer expires before the remote UE finds a suitable relay, the remote UE performs both relay selection and cell selection.

9. The method according to claim 1, wherein, the remote UE utilizes an exception resource pool after detecting the RLF and before RRC reconstruction.

10. The method according to claim 9, wherein: the remote UE utilizes the exception pool provided by the cell in which the RLF is detected when performing the relay selection or cell selection; and the remote UE utilizes the exception pool provided by the cell in which it initiates reconstruction after finding a suitable cell or a suitable relay.

11. The method according to claim 1, further comprising: when attempting to reconstruct an RRC connection, receiving signaling for configuring the remote UE to perform the following operations: performing cell selection and relay selection simultaneously; performing cell selection before performing relay selection; or performing relay selection before performing cell selection.

12. The method according to claim 1, further comprising: after the remote UE has reconstructed an RRC connection with the first network entity or the second network entity, sending a report for indicating the RLF.

13. The method according to claim 12, wherein, the remote UE sends the report via a UE information response message.

14. The method according to claim 12, further comprising: providing an indication of the availability of the report via an RRC setup complete message or an RRC reconstruction complete message.

15. The method according to claim 12, wherein, the report is sent directly or via a relay UE to a network entity.

16. The method according to claim 12, wherein, the report indicates at least one of the following: RLF cause, the identity of the remote UE, measurements on the first link, or measurements associated with the first link, or measurements associated with the second link.

17. A method for wireless communication of a network entity, comprising: receiving a radio resource control (RRC) reconstruction request message from a remote user equipment (UE) via a relay or a cell determined by performing joint relay selection and cell selection; determining whether the remote UE was previously connected to the network entity or another network entity via a first relay UE; if the remote UE was previously connected to the other network entity, retrieving the context of the remote UE from the other network entity; and sending an RRC reconstruction message or an RRC setup message to the remote UE.

18. The method according to claim 17, wherein: the determination is that the remote UE was previously connected to the network entity via the first relay UE; and the RRC reconstruction request message is received from the remote UE via a second relay UE.

19. The method according to claim 18, further comprising: Receive an RRC re - establishment complete message from the remote UE via the same route that the network entity uses to send the RRC re - establishment message.

20. The method according to claim 19, further comprising, when receiving the RRC re - establishment complete message: Re - configure radio link control (RLC) and adaptation layers for the remote UE and the second relay UE; and Signal the first relay to release the adaptation layer configuration related to the remote UE.

21. The method according to claim 17, wherein: The determination is that the remote UE was previously connected to the other network entity via the first relay UE.

22. The method according to claim 21, further comprising: Retrieve the context of the remote UE from the other network entity.

23. The method according to claim 22, further comprising: Receive an RRC re - establishment complete message from the remote UE; and Signal the other network entity to release the context of the remote UE.

24. The method according to claim 17, wherein: The determination is that the remote UE was previously connected to the other network entity via the first relay UE; and The RRC re - establishment request message is received directly from the remote UE.

25. The method according to claim 17, further comprising: Retrieve the context of the remote UE from the other network entity.

26. The method according to claim 24, further comprising: Receive an RRC re - establishment complete message from the remote UE; and Signal the other network entity to release the context of the remote UE.

27. The method according to claim 17, wherein: The determination is that the remote UE was previously connected to the other network entity via the first relay UE; and The RRC re - establishment request message is received from the remote UE via the second relay UE.

28. The method according to claim 27, further comprising: Retrieve the context of the remote UE from the other network entity.

29. The method according to claim 24, further comprising: Receive an RRC re - establishment complete message from the remote UE via the second relay; and Signal the other network entity to release the context of the remote UE.

30. The method according to claim 17, further comprising: Provide an exception resource pool to the remote UE, wherein the remote UE utilizes the exception resource pool provided by the network entity at least for signaling the RRC re - establishment request message.

31. The method according to claim 17, further comprising: When attempting to re - establish an RRC connection, configure the remote UE to: Perform cell selection and relay selection simultaneously; Perform cell selection before performing relay selection; or Perform relay selection before performing cell selection.

32. The method according to claim 17, receive a report from the remote UE indicating a radio link failure (RLF) that triggers the RRC re - configuration request message.

33. The method according to claim 32, wherein, The network entity receives the report via a UE information response message.

34. The method according to claim 32, further comprising: determining the availability of the report via an RRC setup complete message or an RRC reestablishment complete message.

35. The method according to claim 32, wherein, the report is sent directly or via a relay UE to the network entity.

36. The method according to claim 32, wherein, the report indicates at least one of the following: an RLF cause, an identifier of the remote UE, measurements on a first link, or measurements associated with the first link, or measurements associated with a second link.

37. An apparatus for wireless communication of a remote user equipment (UE), comprising: a unit for detecting a radio link failure (RLF) that causes a radio resource control (RRC) connection loss on at least one of a first link between a first relay UE and a first network entity or a second link between the remote UE and the first relay UE; and a unit for attempting to reestablish the RRC connection by performing at least one of relay selection or cell selection and initializing a timer when starting to perform the at least one of the relay selection or the cell selection, wherein the apparatus further comprises: a unit for performing cell selection to search for a suitable cell; and a unit for performing relay selection to search for a suitable relay if the timer expires before the remote UE finds a suitable cell; or a unit for performing relay selection to search for a suitable relay; and a unit for performing cell selection to search for a suitable cell if the timer expires before the remote UE finds a suitable relay.

38. The apparatus according to claim 37, further comprising: a unit for simultaneously performing cell selection and relay selection; a unit for performing cell selection before performing relay selection; or a unit for performing relay selection before performing cell selection.

39. The apparatus according to claim 37, further comprising: a unit for sending a report for indicating the RLF after the remote UE has reestablished an RRC connection with the first network entity or a second network entity.

40. An apparatus for wireless communication of a network entity, comprising: a unit for receiving a radio resource control (RRC) reestablishment request message from a remote user equipment (UE) via a relay or a cell determined by performing joint relay selection and cell selection; a unit for determining whether the remote UE was previously connected to the network entity or another network entity via a first relay UE; a unit for retrieving the context of the remote UE from the other network entity if the remote UE was previously connected to the other network entity; and a unit for sending an RRC reestablishment message or an RRC setup message to the remote UE.

41. The apparatus according to claim 40, further comprising: A unit for sending a report for instructing the RLF to provide an exception resource pool to the remote UE, wherein the remote UE utilizes the exception resource pool provided by the network entity to at least signal the RRC reestablishment request message.

42. The apparatus according to claim 40, further comprising: A unit for, when attempting to reestablish an RRC connection, sending a report for instructing the RLF to configure the remote UE to perform the following operations: Simultaneously perform cell selection and relay selection; Perform cell selection before performing relay selection; or Perform relay selection before performing cell selection.

43. An apparatus for wireless communication of a remote user equipment (UE), comprising: At least one processor and a memory, which are configured to: Detect a radio link failure (RLF) that causes a radio resource control (RRC) connection loss on at least one of a first link between a first relay UE and a first network entity or a second link between the remote UE and the first relay UE; And Attempt to reestablish the RRC connection by performing at least one of relay selection or cell selection, and initializing a timer when starting to perform the at least one of the relay selection or the cell selection, wherein the at least one processor and the memory are further configured to: Perform cell selection to search for a suitable cell; and If the timer expires before the remote UE finds a suitable cell, perform relay selection to search for a suitable relay; Or Perform relay selection to search for a suitable relay; and If the timer expires before the remote UE finds a suitable relay, perform cell selection to search for a suitable cell.

44. The apparatus according to claim 43, wherein the at least one processor and the memory are configured to, when attempting to reestablish the RRC connection, receive signaling for configuring the remote UE to perform the following operations: Simultaneously perform cell selection and relay selection; Perform cell selection before performing relay selection; or Perform relay selection before performing cell selection.

45. The apparatus according to claim 43, wherein the at least one processor and the memory are configured to send a report for indicating the RLF after the remote UE has reestablished an RRC connection with the first network entity or a second network entity.

46. An apparatus for wireless communication of a network entity, comprising: At least one processor and a memory, which are configured to: Receive a radio resource control (RRC) reestablishment request message from a remote user equipment (UE) via a relay or a cell determined by performing joint relay selection and cell selection; Determine whether the remote UE was previously connected to the network entity or another network entity via a first relay UE; If the remote UE was previously connected to the other network entity, retrieve the context of the remote UE from the other network entity; and Send an RRC reestablishment message or an RRC setup message to the remote UE.

47. The apparatus according to claim 46, wherein at least one processor and a memory are configured to send a report for instructing the RLF to provide an exception resource pool to the remote UE, wherein, the remote UE utilizes the exception resource pool provided by the network entity for at least signaling the RRC reestablishment request message.

48. The apparatus according to claim 46, wherein at least one processor and a memory are configured to, when attempting to reestablish an RRC connection, send a report for instructing the RLF to configure the remote UE to perform the following operations: perform cell selection and relay selection simultaneously; perform cell selection before performing relay selection; or perform relay selection before performing cell selection.

49. A computer-readable medium having instructions stored thereon for performing the following operations: detect, by a user equipment (UE), a radio link failure (RLF) that causes a radio resource control (RRC) connection loss on at least one of a first link between a first relay UE and a first network entity or a second link between a remote UE and the first relay UE ； and attempt to reestablish the RRC connection by performing at least one of relay selection or cell selection, and initializing a timer when starting to perform the at least one of the relay selection or the cell selection, wherein, the instructions further include: perform cell selection to search for a suitable cell; and if the timer expires before the remote UE finds a suitable cell, perform relay selection to search for a suitable relay; or perform relay selection to search for a suitable relay; and if the timer expires before the remote UE finds a suitable relay, perform cell selection to search for a suitable cell.

50. A computer-readable medium having instructions stored thereon for performing the following operations: receive, by a network entity, a radio resource control (RRC) reestablishment request message from a remote user equipment (UE) via a relay or a cell determined by performing joint relay selection and cell selection; determine whether the remote UE was previously connected to the network entity or another network entity via a first relay UE; if the remote UE was previously connected to the other network entity, retrieve the context of the remote UE from the other network entity; and send an RRC reestablishment message or an RRC setup message to the remote UE.

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