Repeater assisted mobility

Abstract

The relay relays communications between the UE and the first BS. The repeater measures a time difference between signals received from the first BS and from the second BS. The repeater performs cell measurements of these signals. The repeater transmits information indicating the measured time difference and the cell measurement to the first BS. The first BS communicates with the UE through the repeater. The first BS receives, from the relay, information indicating a time difference measured by the relay between a signal received from the first BS and a signal received from the second BS and a cell measurement of the relay on these signals. The first BS makes a handover decision for the UE based at least on the received information indicating the cell measurements.

Description

Technical Field

[0001] The exemplary embodiments herein relate generally to wireless communication systems and, more particularly, to repeaters used in such systems. Background Art

[0002] Cellular repeaters are widely used in 2G (second generation) / 3G (third generation) / 4G (fourth generation) wireless networks to provide coverage extension. Classic RF (radio frequency) repeaters receive signals from nearby base stations, amplify the signals and retransmit the signals in the downlink direction to nearby user devices. In the uplink direction, RF repeaters receive signals from UE (user equipment, wireless device), amplify the signals and retransmit the signals to the base station.

[0003] 5G NR (fifth generation, new radio) repeaters support beamforming capabilities, i.e., they use narrow beams on the access link to communicate with the UE, and use narrow beams on the backhaul link to communicate with the base station. In 3GPP, the 5G repeaters used were called "smart" repeaters (SR), and are now called "network controlled" repeaters (NCR), which means that some intelligence is needed to dynamically manage the direction of the beams generated by the repeater according to the traffic conditions. However, the decision is made by the network (NW) and the repeater is controlled via a dedicated control link.

[0004] While 5G NR repeaters are still being standardized, there are issues that can be improved when using these and similar repeaters. Summary of the invention

[0005] This section is intended to include examples and is not intended to be limiting.

[0006] In an exemplary embodiment, a repeater includes components for performing the following: relaying communications between multiple user devices and a first base station; measuring a time difference between a signal received from the first base station and a signal received from a second base station; performing cell measurements of the signal received from the first base station and the signal received from the second base station; and sending information indicating the measured time difference and the cell measurement to the first base station.

[0007] In another exemplary embodiment, a method includes: relaying, by a repeater, communications between a plurality of user equipments and a first base station; measuring, by the repeater, a time difference between a signal received from the first base station and a signal received from a second base station. The method also includes: performing, by the repeater, a cell measurement of the signal received from the first base station and the signal received from the second base station; and sending, by the repeater, information indicating the measured time difference and the cell measurement to the first base station.

[0008] Additional exemplary embodiments include a computer program comprising code for performing the method described in the preceding paragraph when the computer program is run on a processor. A computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer readable medium carrying computer program code embodied therein for use with a computer. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of a computer.

[0009] In another exemplary embodiment, an exemplary repeater includes one or more processors and one or more memories including computer program code. The one or more memories and computer program code are configured to, together with the one or more processors, cause the repeater to: relay communications between a plurality of user devices and a first base station; measure a time difference between a signal received from the first base station and a signal received from a second base station; perform a cell measurement of the signal received from the first base station and the signal received from the second base station; and send information indicating the measured time difference and the cell measurement to the first base station.

[0010] An exemplary computer program product includes a computer readable storage medium carrying computer program code embodied therein for use with a computer. The computer program code includes: code for relaying communications between a plurality of user devices and a first base station; code for measuring a time difference between a signal received from the first base station and a signal received from a second base station; code for performing a cell measurement of the signal received from the first base station and the signal received from the second base station; and code for sending information indicating the measured time difference and the cell measurement to the first base station.

[0011] In another exemplary embodiment, a first base station includes components for performing the following: communicating with multiple user devices through a repeater, receiving information from the repeater, the information indicating a time difference measured by the repeater between a signal received from the first base station and a signal received from a second base station, and indicating cell measurements performed by the repeater on the signal received from the first base station and the signal received from the second base station; and making switching decisions for the multiple user devices based at least on the received information indicating the cell measurements.

[0012] In an exemplary embodiment, a method is disclosed that includes communicating with a plurality of user devices via a repeater. The method includes receiving information from the repeater that indicates a time difference measured by the repeater between a signal received from a first base station and a signal received from a second base station, and indicates a cell measurement performed by the repeater on the signal received from the first base station and the signal received from the second base station. The method includes making a handover decision for the plurality of user devices based at least on the received information indicating the cell measurement.

[0013] Additional exemplary embodiments include a computer program comprising code for performing the method described in the preceding paragraph when the computer program is run on a processor. A computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer readable medium carrying computer program code embodied therein for use with a computer. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of a computer.

[0014] An exemplary first base station includes one or more processors and one or more memories including computer program code. The one or more memories and computer program code are configured to, together with the one or more processors, cause the first base station to at least: communicate with a plurality of user equipment via a repeater, receive information from the repeater indicating a time difference measured by the repeater between a signal received from the first base station and a signal received from a second base station, and indicating cell measurements performed by the repeater on the signal received from the first base station and the signal received from the second base station; and make a handover decision for the plurality of user equipment based at least on the received information indicating the cell measurements.

[0015] An exemplary computer program product includes a computer readable storage medium carrying computer program code embodied therein for use with a computer. The computer program code includes: code for communicating with a plurality of user devices via a repeater; code for receiving information from the repeater indicating a time difference measured by the repeater between a signal received from a first base station and a signal received from a second base station and indicating cell measurements made by the repeater on the signal received from the first base station and the signal received from the second base station; and code for making a handover decision for the plurality of user devices based at least on the received information indicating the cell measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the attached picture:

[0017] Figure 1 is a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced;

[0018] Figure 1A is suitable for achieving Figure 1 a block diagram of a circuit shown in a network node of any network node in;

[0019] Figure 1B is a block diagram showing circuitry in a network node for a repeater 130, illustrating a loopback technique;

[0020] Figure 2 DAPS switching is shown;

[0021] Figure 3A and Figure 3B shows the L1 inter-cell changes in signaling for baseline switching ( Figure 3A ) and L1 inter-cell mobility ( Figure 3B );

[0022] Figure 4 is a block diagram showing how a repeater (eg, NCR) multiplexes broadcast transmissions (ie, SSB) from two different donors;

[0023] Figure 5 is a diagram illustrating cell mobility when a UE is served by a relay;

[0024] Figure 6 is a diagram illustrating network controlled relay assisted mobility according to an exemplary embodiment;

[0025] Figure 7 is a diagram illustrating ΔT and uplink propagation in an exemplary embodiment;

[0026] Figure 8 shows DL and UL timing for a single repeater, two donor topology in an exemplary embodiment;

[0027] Fig. 9 is a message flow diagram for repeater-assisted mobility when Msg1 is bypassed;

[0028] Fig.10 is the message flow diagram of relay assisted mobility when the Msg2 content is sent by the source gNB. DETAILED DESCRIPTION

[0029] Abbreviations that may be found in the specification and / or drawings are defined at the end of the Detailed Description section that follows.

[0030] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this detailed description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention, without limiting the scope of the invention which is defined by the claims.

[0031] When more than one reference numeral, word or acronym is used with " / " within the specification, " / " may be interpreted as "or", "and" or "both" as generally used in the specification.

[0032] As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising", "having", and / or "including" when used herein specify the presence of stated features, elements, and / or components, etc., but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0033] The exemplary embodiments herein describe techniques for relay-assisted mobility. Additional description of these techniques is described following systems in which the exemplary embodiments may be used.

[0034] Go to Figure 1 , which shows a block diagram of one possible and non-limiting exemplary system 101 in which exemplary embodiments may be practiced. User equipment (UE) 110, relay 130, source gNB 170-1, target gNB 170-2, (multiple) network element 190, and (multiple) data network 191 are shown as network nodes in the system. Although only one UE 110 is shown, there will be multiple UEs 110. In Figure 1 In the present invention, a user equipment (UE) 110 is in wireless communication with a wireless network 100, which includes a relay 130, a source gNB 170-1, a target gNB 170-2, and (multiple) network elements 190. The source gNB and the target gNB may be referred to as donors, as described below. In addition, the source gNB 170-1 may also be referred to as a "serving" gNB, and these gNBs may also be characterized as serving cells and neighboring cells instead of source / serving gNBs and target gNBs, respectively. A known cell is formed and operated by a base station (BS) such as a gNB. Regardless of the terminology used, one or more UEs are initially connected to a first network node (e.g., gNB 170-1) (or the same cell) in order to connect to the network 100, and one or more UEs are handed over to a second network node (e.g., gNB 170-2) (or the same cell) in order to continue to connect to the network 100.

[0035] With respect to network 100, repeater 130 should be considered a network node of access network 100, as the analog repeater is in the wired network, although the operation of the wireless repeater is transparent to the UE. The UE is connected to the base station (BS) via a repeater in the traditional manner. The repeater proxies / emulates the UE in the UL and the base station in the DL in the RF domain. In an exemplary embodiment, repeater 130 uses the RF domain, covering pure analog signal repetition (before ADC) or digital signal (for example, repeated after ADC to obtain a digital signal and sent to a DAC to convert back to an analog signal). Both cases can be considered as "amplified forward transmission". Repeater 130 is capable of connecting to the source gNB 170-1 via a wireless link 111-2 and to the target gNB 170-2 via a wireless link 111-3. Typically, each of links 111-2 and 111-3 is actually two separate links. The amplified fronthaul portion of the link acts as a proxy for the base station in the DL and the UE in the UL, and there are also control links through which the network controls and configures the NCR 130 during the amplified fronthaul operation. On these control links, the NCR 130 can be considered to act like a specially designated UE, although it is still a network node.

[0036] UE is a wireless, typically mobile device that can access wireless network 100 via wireless link 111-1. Source gNB 170-1 is connected to network element 190 via link 176-1, and target gNB 170-2 is connected to network element 190 via link 176-2. Two or more gNBs 170 communicate via link 131. Links 131 and 176 can be wired (such as optical cables) or wireless. Network element 190 can include many different network elements, as described below, and can be connected to one or more data networks 191, such as the Internet, via link 181.

[0037] Each gNB 170 is a base station that provides access to the wireless network 100 by wireless devices such as UE 110 (e.g., acting as a relay 130 for one or more UEs in the UL). The gNB 170 may be, for example, a base station for 5G, also known as New Radio (NR), and may also be referred to as a RAN node. In 5G, a RAN node may be a NG-RAN node, which is defined as a gNB or ng-eNB. A gNB is a node that provides NR user plane and control plane protocol termination to a UE and is connected to a 5GC (e.g., network element 190) via an NG interface. An ng-eNB is a node that provides E-UTRA user plane and control plane protocol termination to a UE and is connected to a 5GC via an NG interface. The NG-RAN may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) and a distributed unit (DU) (gNB-DU) (neither shown). Note that the DU may include or be coupled to and control a radio unit (RU). The gNB-CU is a logical node that hosts the RRC, SDAP, and PDCP protocols of a gNB or controls the operation of the RRC and PDCP protocols of an en-gNB, or one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU. The gNB-DU is a logical node that hosts the RLC, MAC, and PHY layers of a gNB or en-gNB, and its operation is partially controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU. The gNB 170 may also be an eNB (evolved NodeB) base station, a base station for LTE (Long Term Evolution), or any other suitable base station.

[0038] The wireless network 100 may include one or more network elements 190, which may include core network functions and provide connectivity to a data network 191, such as a telephone network and / or a data communications network (e.g., the Internet), via one or more links 181. Such core network functions for 5G may include access and mobility management functions (AMF) and / or user plane functions (UPF) and / or session management functions (SMF). Such core network functions for LTE may include MME (mobility management entity) functions and / or SGW (serving gateway) functions. These are merely exemplary functions that may be supported by the network element 190, and note that both 5G and LTE functions may be supported.

[0039] Any of the nodes 110, 130, 170-1, 170-2, and 190 may be Figure 1A The circuit shown in FIG. 120 is implemented as shown in FIG. Figure 1A, the node 120 includes a control module 150, which includes one or both of the parts 150-1 and / or 150-2 that can be implemented in a variety of ways. The control module 150 can be implemented in hardware as the control module 150-1, such as being implemented as part of one or more processors 152. The control module 150-1 can also be implemented as an integrated circuit or implemented by other hardware such as a programmable gate array. In another example, the control module 150 can be implemented as a control module 150-2, which is implemented as a computer program code 153 and executed by one or more processors 152. For example, one or more memories 155 and the computer program code 153 are configured to enable the node 120 to perform one or more operations as described herein together with the one or more processors 152. Note that the functionality of the control module 150 can be distributed, for example, distributed between the DU and the CU.

[0040] Node 120 includes one or more transceivers 160 including a receiver (Rx) 162 and a transmitter (Tx) 163 coupled to one or more antennas 158 and communicating via wireless link 111 .

[0041] One or more network interfaces 161 communicate over a network, such as via links 131 and / or 176. Two or more gNBs 170 communicate using, for example, link 131. For a gNB, link 131 may be wired or wireless, or both, and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interfaces for other standards. Other interfaces may be used, depending on which node 110, 130, 170, or 190 is being described. One or more buses 157 may be an address, data, or control bus, and may include any interconnect mechanism, such as a series of lines on a motherboard or integrated circuit, an optical fiber or other optical communication device, a wireless channel, etc.

[0042] Note that repeater 130 may implement a loopback technique. Figure 1B1 is a block diagram showing circuitry in a network node for a relay 130, illustrating a loopback technique. The example shows two transceivers 160-1 and 160-2 and two sets of antennas 158-1 and 158-2, and the remaining circuitry is removed for ease of description. For UL, the relay 130 (as the network node 120) can receive data from the UE 100 via the receiver of the transceiver 160-1 via the link 111-1, and use the UL loopback path 133-UL to the transmitter of the transceiver 160-2, and send to the gNB 170-1 (and also 170-2 in this example) via the link 111-2. Similarly, for DL, relay 130 (as network node 120) can receive data from gNB 170-1 via link 111-2 and via the receiver of transceiver 160-2, and use DL loopback path 133-DL to the transmitter of transceiver 160-1 and send to UE 110 via link 111-1. Although two sets of antennas 158-1 and 158-2 are shown, this is for ease of description and there may be only one set of antennas 158. UL path 133-UL and DL path 133-DL can be transmitted entirely using bus 157 or an addition to bus 157.

[0043] Note that loopback can also be considered a relay operation. That is, the relay 130 can be considered to relay messages between the UE and the gNB node, and loopback is a way of representing this relaying. In any signaling diagram herein, it is assumed that the relay 130 relays messages via an appropriate loopback path 133.

[0044] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functions into a single software-based managed entity, a virtual network. Network virtualization involves platform virtualization, which is often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks or portions of networks into virtual units, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities resulting from network virtualization are still implemented to some extent using hardware such as processor 152 and memory 155, and such virtualized entities also create technical effects.

[0045] Computer readable memory 155 may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, firmware, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. Computer readable memory 155 may be a component for performing storage functions. As a non-limiting example, processor 152 may be of any type suitable for the local technical environment and may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Processor 152 may be a component for performing functions, such as controlling UE 110, relay 130, gNB 170, and (multiple) network element 190, as well as other functions described herein.

[0046] In general, various embodiments of the user device 110 may include, but are not limited to, a cellular phone (such as a smart phone, a mobile phone, a cellular phone, a Voice over Internet Protocol (IP) (VoIP) phone, and / or a wireless local loop phone), a tablet computer, a portable computer, a vehicle or in-vehicle device (e.g., wireless V2X (vehicle-to-everything) communication), an image capture device (such as a digital camera), a gaming device, a music storage and playback device, an Internet device (including an Internet of Things (IoT) device), an IoT device having sensors and / or actuators for, for example, automation applications, and a portable unit or terminal incorporating a combination of such functionality, a laptop embedded device (LEE), a laptop device (LME), a universal serial bus (USB) software dongle, a smart device, a wireless customer premises equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of an industrial and / or automation process chain), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, and the like. That is, UE 110 may be any terminal device capable of wireless communication. As an example and not limitation, UE may also be referred to as a communication device, terminal device (MT), subscriber station (SS), portable subscriber station, mobile station (MS) or access terminal (AT).

[0047] Having introduced a suitable but non-limiting technical background for practicing exemplary embodiments, exemplary embodiments will now be described in more detail.

[0048] As mentioned earlier, 5G NR repeaters are being standardized. Although standardization is not yet complete, the inventors have determined that NR repeaters have advantages and disadvantages compared to IAB devices. For example, for coverage improvement / extension in areas without fiber access, IAB nodes and repeater nodes can be used, each with their own advantages and disadvantages. Consider the following.

[0049] 1) NR IAB has high spectrum efficiency but introduces additional latency because the IAB is a “regenerative repeater” with built-in mobile terminal (MT) and distributed unit (DU) functions.

[0050] 2) RF repeaters are non-regenerative (amplify forward) and therefore introduce minimal latency, but they reduce spectral efficiency in the overall cell by actively amplifying both signal and noise. They are also a non-negligible source of "longer than expected distance" interference (echo). NR RF repeaters can address some of these interference issues using narrow beams. Additionally, RF repeaters tend to amplify noise even when no traffic is present (NR NCR can also address this issue).

[0051] 3) Repeaters have significant cost advantages over IAB devices. Repeaters have less energy consumption, smaller form factor, and less weight, making them easier to deploy.

[0052] Some 3GPP participants are heavily promoting Network Controlled Repeaters (NCRs) due to their cost advantages over IAB devices. Additionally, areas of hybrid deployment of IAB nodes and Repeater nodes can be seen, where either a gNB node or an IAB node can be the parent node of a Repeater. Many top tier cellular service providers are deploying / conducting trials with 5G Repeaters in their networks.

[0053] Another problem is supporting repeaters with more than one donor. A donor is a base station to which a repeater can connect (e.g. Figure 1 In this context, NCR is non-regenerative. That is, it relies on the use of dedicated physical resources (e.g., SSB beams) from the donor to provide service to UEs in its access link. Dedicating multiple SSB beams to the relay reduces the number of SSB beams available to the donor (i.e., reduces the spatial resolution of the SSB beams used for the donor coverage area).

[0054] With a repeater capable of supporting more than one donor, the repeater can "pool" SSBs from several donors together to support the spatial directionality needs in its access link. As a result, each donor can dedicate fewer SSBs to the repeater, and can therefore keep more SSB beams for its own use.

[0055] A relay supporting multiple donors can improve the robustness of the operation. In particular, in the event of failure of one donor, the UEs served by the relay can fall back to the working donor.

[0056] Repeaters can be installed on trains or cars to provide better service to UEs inside the moving vehicles. This is due to the following reasons:

[0057] 1) The repeater amplifies both downlink and uplink signals to and from the UE, so the UE can achieve better SNR and higher throughput.

[0058] 2) Repeaters are less constrained by size or power consumption than UEs, so repeaters can achieve higher power gain or better beam steering (more panels, more antenna elements).

[0059] Another possible issue includes the following. There has been feasibility discussion on repeaters in 3GPP. Specifically, 5G wireless repeaters (e.g., NCRs) are expected to have the ability to achieve time and frequency synchronization with the donor over the air. In addition, the repeater is expected to be able to search and detect SSB signals using its backhaul beam during SSB burst periods from the donor gNB. The repeater is also expected to determine the strongest SSB signal from the SSB signals that the repeater has detected (i.e., the repeater needs to measure and compare the RSRP / RSRQ of the SSB signals it detects).

[0060] The repeater is expected to identify the beam ID of the strongest SSB signal in order to determine the donor's radio frame boundaries (i.e., the repeater needs to perform some simple demodulation of the SSB signal and derive the cell ID and beam index in the process to determine which beam the repeater has detected and the correct offset in samples for that SSB beam from the radio frame perspective).

[0061] The repeater is expected to track the strongest SSB signal and maintain a stable time reference to the donor, where the repeater periodically performs SSB detection to synchronize time and frequency with the donor. With the repeater in motion, the repeater should be able to search and detect SSBs from the target donor and compare the RSRP / RSRQ differences between the source and target donors. At the same time, the repeater should be able to detect the time difference between the current return path of the source donor and the future return path to the target donor by measuring the time difference of arrival (TDOA) of the SSBs from the source and target donors using the source donor as a time reference.

[0062] When a UE transfers from a source gNB to a target gNB, one issue that arises for both the UE and the relay involves handover. One such handover is a dual active protocol stack (DAPS) handover.

[0063] exist Figure 2 A main idea for DAPS is shown in Figure 2 DAPS handover is shown. DAPS is a Release 16 feature for improving reliability and latency for UE handovers. The main idea is that after the source gNB 270-1 (shown as forming the source cell 275-1) triggers the handover, the data traffic from the source gNB remains towards the UE 210, together with the data traffic from the target gNB 270-2 (shown as forming the target cell 275-2) towards the same UE 210, until the RACH procedure from the source gNB to the target gNB is reliably completed and the uplink of the UE is switched to the target gNB. Both the source gNB and the target gNB have PDCP, RLC, MAC and PHY layers. The UE has separate source PDCP_S, RLC_S, MAC_S and target PDCP_T, RLC_T, MAC_T layers, but has a common PDCP layer. Reference numeral 220 indicates the transmission of uplink PDCP data packets until the random access in the target cell is completed. Reference numeral 225 indicates the forwarding of downlink PDCP packets. Reference numeral 230 indicates transmission of an uplink PDCP data packet after random access is completed, and reference numeral 235 indicates simultaneous reception of a downlink PDCP data packet from a source cell to a target cell.

[0064] The benefits of DAPS are: 1) reduction of data outages, and 2) improvement of HO robustness. However, DAPS has problems, including the following.

[0065] DAPS requires simultaneous reception from two gNBs (different PCI, different timing), which requires a special class of UEs with two independent receivers. DAPS still requires the UE to perform a full PRACH procedure with the target gNB. Group switching is not possible in DAPS.

[0066] The relay backhaul beam may be time domain duplex, i.e., it cannot support simultaneous reception from both the source and target donors to support DAPS. It is also difficult for a relay to generate two spatially separated access beams towards the UE in the access link. Furthermore, the spatial diversity exploited by DAPS may not exist in a relay access scenario.

[0067] In contrast, the exemplary embodiments herein do not require dual reception and are applicable to both non-DAPS capable UEs and DAPS capable UEs in fallback (single receiver) mode. These exemplary embodiments aim to reduce the data interruption and messaging overhead of the conventional handover framework. These exemplary embodiments may skip MSG1 (which is instead resolved by the relay) and may use the pre-configured time for RAR (MSG2) and thus remove the need for a RAR window. Therefore, the exemplary embodiments herein use a different RACH procedure.

[0068] There is also a discussion of L1 / L2 inter-cell mobility in RANL1 / RAN4, where "L" stands for layer. The main idea is Figure 3A and Figure 3B Shown, Figure 3A and Figure 3B shows the L1 inter-cell changes in signaling for baseline switching ( Figure 3A ) and L1 inter-cell mobility ( Figure 3B ). That is, Figure 3A The figure in is based on the traditional L3 handover (step 6 triggers HO). Figure 3A The figure in FIG. 1 is based on L1-L2 handover (step 9 triggers HO). In both cases, a conventional full RACH is required.

[0069] like Figure 3B As shown in , there is a proposal to perform handover via L2 messaging (ie, MAC CE) (see Figure 3B and the box marked with reference numeral 381). Compared with the traditional L3-based switching (flow chart in Figure 3), this switching will be faster and with shorter data interruption.

[0070] The proposal still requires a full random access procedure (step 10), measurement reports come from the UE (step 1), and the proposal is based on each UE. In contrast, in this article, there is no need to use a full random access procedure, measurement reports can come from the relay in this article, and group switching is proposed in some exemplary embodiments of this article.

[0071] The concept of L1 / L2 based handover is still compatible with the examples herein, for example, MAC CE may be used herein to trigger cell switching in order to further reduce data interruption during handover.

[0072] like Figure 3A and Figure 3B As shown, conventional full RACH is required in L1 / L2 inter-cell mobility.

[0073] A scheme for repeaters to support multiple donors in U.S. patent application serial number 17 / 502,955, filed on October 15, 2021, has been previously proposed. Figure 4 An example of a main exemplary block diagram of such a system is shown. The exemplary embodiments disclosed below are intended to solve problems such as Figure 4 The mobility process system shown, Figure 4 is a block diagram showing how a repeater (eg, NCR) multiplexes broadcast transmissions (ie, SSB) from two different donors.

[0074] There is a donor A SSB beam set 410-1 (e.g., formed by gNB 170-1) and a donor B SSB beam set 410-2 (e.g., formed by gNB 170-2). There is an M for donor A. A Beam scanning beam 420-1 and M for donor B B Scanning beam 420-2. These are direct access beams for UEs that are not connected through relay 130. There are N A Beam 430-1 and N directed from donor B to the repeater B Beam 430-2. Repeater 130 thus multiplexes the first set of N A Beam 430-1 and the second set of N B Beam 430-2. Repeater 130 performs beam scanning for donors A and B. There is an optional conflict resolution channel 440 between the donors and control and resource allocation and conflict resolution channels 450-1 (donor A to repeater) and 450-2 (donor B to repeater).

[0075] Figure 5 A problem with this or any system in which a repeater moves relative to a base station is shown in Figure 5 is a diagram showing cell mobility when UEs are served by a relay. A train 510 has a relay 130 on it, and the train moves away from the current donor gNB 170-1 and towards the future donor gNB 170-2. There is handover signaling 510 between the two gNBs 170 (e.g., via link 131). As the relay travels towards the target donor, it is clear that all UEs served by the relay access link need to be handed over from the current source donor to the future target donor, and the question mark indicates that the beam to be used for this has not yet been decided.

[0076] Compared to normal UE handover between two gNBs (i.e., without relay 130), there are some unique characteristics regarding handover of a UE served by a mobile relay. More specifically, consider the following.

[0077] 1) The position of the UE relative to the relay can remain essentially unchanged, ie, the access beam direction and the path loss in the access link remain the same before and after the handover.

[0078] 2) The position of the relay relative to the source and target donors is constantly changing, i.e., the backhaul beam direction (required to switch from source to target) and the path loss have changed significantly. In other words, the conditions that trigger the handover (e.g., the RSRP / RSRQ difference between the source and target donors) depend almost entirely on the backhaul link.

[0079] 3) The changes in timing and path loss on the backhaul link for the mobile relay are common to all UEs served by the access link.

[0080] For UEs active with a source donor, it is desirable to minimize interruptions in data transmission during the handover from the source donor to the target donor. From a network level, it is desirable to avoid a large number of UEs participating in the RACH simultaneously, as this would require a large amount of "expensive" RACH resources to be allocated to make this feasible. (PRACH preamble sequences, especially contention-free sequences, are a very limited resource in 5G NR in general).

[0081] In this scenario, there is an opportunity for the relay to assist the handover process for multiple UEs served by the relay to improve user experience and network efficiency.

[0082] The present exemplary embodiments address at least the above opportunities and some or all of the above problems (as well as potentially other problems) by providing a method and system for a network-controlled relay to assist in handover of one or more UEs in its access link, wherein the relay measures the power and time difference between the source cell and the target cell in the backhaul link and sends a measurement report to the source gNB. The source gNB can use the power difference to make a handover decision. The target gNB or the source gNB can use the time difference of arrival (TDOA; although not equal to the TDOA frame from NR positioning) of the SSB beam to derive the uplink timing advance of the target gNB relative to the UE, thereby removing the need for Msg1. The source gNB can initiate a group HO by collecting the identities of multiple UEs served by the relay. Through the source gNB, the target gNB can provide the UE with information such as the target gNB configuration and future UE identities (used by the target) in advance.

[0083] There are two potential techniques for (optional) RAR processing, as follows.

[0084] 1) The scheduling of RAR transmissions in the target cell (i.e., Msg2 DL assignments, such as timeslots, physical resources, etc.) may be configured by the target gNB and transmitted to the UE via the source gNB prior to handover. One view of this is that the relevant information is sent along with the traditional RAR content (such as PDUs). Thus, the UE may receive Msg2 immediately after achieving synchronization with the target gNB, without the need for Msg1 / RACH preamble transmissions in the target cell. It should also be noted that the target gNB may alternatively transmit the RAR transmissions directly to the UE, thereby bypassing the source gNB.

[0085] 2) The scheduling of Msg3 transmission in the target cell (i.e., Msg3 UL grant, such as time slot, physical resources, etc.) can be configured by the target gNB and transmitted to the UE via the source gNB before the handover. One viewpoint on this is that dedicated signaling (e.g., PDU) can be used to configure each UE. Thus, the UE can send Msg3 immediately after achieving synchronization with the target gNB without Msg1 / RACH preamble transmission and Msg2 / RAR reception in the target cell.

[0086] In addition, the exemplary embodiments herein also provide recommended signaling between the relay, UE, source gNB and target gNB to enable the use of such a system in a 5G NR network.

[0087] In addition, many UEs in a moving train may need to perform cell handover (HO) simultaneously. This leads to a bottleneck in network performance due to the large number of Msg1 and Msg2 processing, configured inter-cell measurement objects (MO) and associated measurement gaps (MG), resulting in reduced UE throughput.

[0088] Mobile Network Controlled Repeaters (NCRs) have been considered to serve UEs in high-speed trains and similar environments.

[0089] Figure 6 An exemplary network with network controlled relay nodes, UEs, source gNB nodes, and target gNB nodes is depicted in FIG. UE 110 has access beam 660 to relay 130, which communicates with source gNB 170-1 via source backhaul beam 640 and with target gNB 170-2 via target backhaul beam 645.

[0090] Source backhaul beam 640 is used for at least the indicated signaling: measurement reports 620 sent from relay 130 to source gNB 170-1; beam control signaling 625 from source gNB 170-1 to relay 130; and mobility control and trigger signaling from source gNB 170-1 to UE 110 (and through relay 130). Both source backhaul beam 640 and target backhaul beam 645 include (see reference numeral 650) differential SSB power and timing measurements for relay 130. Between source gNB 170-1 and target gNB 170-2, there is mobility setup signaling 610 and mobility request signaling 615.

[0091] In more detail, a network controlled repeater (NCR) 130 is installed on a train 510 that travels from a source gNB 170-1 toward a target gNB 170-2. Both the source gNB and the target gNB have multiple SSB beams 670-1 to 670-4 and 680-1 to 680-4, respectively, pointing to different spatial directions, and these beams are active during the SSB beam scanning period. Note that although an equal number of beams are shown on both gNBs, this is not necessarily the case and each gNB 170 may have a different number of beams. The repeater 130 has initially established a connection with the source gNB by pointing the backhaul beam to the strongest SSB beam of the source gNB (shown as the source backhaul beam 640). The UE 110 inside the train 510 initially communicates with the source gNB 170-1 via the access beam 660 of the repeater and the backhaul beam 640 of the source.

[0092] As the train 510 travels away from the source gNB 170-1 toward the target gNB 170-2, the SSB signal of the target gNB 170-2 may become stronger than the SSB signal of the source gNB. The UE will need to handover from the source gNB to the target gNB. One unique thing about this scenario is that the position of the UE relative to the repeater (i.e., the access link) may remain largely unchanged, but the position of the repeater relative to the donor gNB may have changed significantly.

[0093] The NCR 130 has the capability to acquire time and frequency synchronization with the donor gNB over the air by detecting and tracking the strongest SSB signal. It can also perform signal quality measurements (e.g., RSRP and RSRQ) on the SSB signal.

[0094] It is proposed to address these inter-cell mobility related capacity bottlenecks by extending the NCR concept and framework. In particular, it is proposed that a relay may assist in handover of multiple active UEs served by a relay 130. More specifically, the method may include the following. This is an overview of possible actions, and more details are presented below.

[0095] A) Instead of each UE performing measurements, the NCR 130 measures the time difference (denoted as ΔT) and (optionally but preferably) the power difference between the source gNB and the target gNB. The measurements or measurement events are signaled / reported to the source gNB.

[0096] B) The TDOA / ΔT measured by the NCR can be applied to all UEs as the common change of their respective absolute timing advances (TA) after HO.

[0097] C) The source gNB 170-1 collects identity information of UEs sharing a common ΔT (i.e., those served by the relay) based on some unique ID or index of one or more SSB beams used by the relay towards the UE.

[0098] D) The source gNB triggers a simplified HO procedure in the UE, possibly based on previously reported UE capabilities regarding support for simplified Ho. The term “simplified HO” means that no Msg1 or no Msg1 / Msg2 are sent / received by the UE, since the TA in the target cell is now known prior to the HO, without the need for the target gNB to measure the timing of Msg1 / RACH preamble reception.

[0099] E) The source gNB signals at least the UE identification information to the target gNB 170-2, and the target gNB 170-2 signals back information about the HO / mobility resource allocation.

[0100] F) Since Msg1 is not sent, there is no risk of collision and RACH end after Msg2 / RAR. Msg2 can be processed in a conventional manner, or alternatively, the RAR scheduling bottleneck can be alleviated in the following way.

[0101] 1) The source gNB uses the HO trigger to send the RAR, or the HO trigger can be used to pre-schedule resources to receive the RAR PDSCH / MAC CE from the target gNB after the HO.

[0102] 2) The RAR content may be legacy or modified. For example, the modified RAR may not include RAPID because there is no RACH preamble transmission and / or the modified RAR may signal a new relative TA command value to the UE group (instead of an absolute TA value for each RAPID).

[0103] During and after HO, the NCR framework can control the NCR beams in a way that the HO remains transparent to the UE from a beam management perspective. This is part of the legacy NCR framework and is outside the scope of this disclosure.

[0104] It should be noted that the maximum gain is expected if NCR assists in handing over the entire group of UEs simultaneously. However, the sub-case of assisting each UE individually still brings gains and may be easier in some cases.

[0105] Additional details regarding the above process and corresponding signaling are provided below.

[0106] As an overview, the exemplary embodiments provide the following:

[0107] 1) Perform HO-related measurements (e.g., power and / or timing difference between source and target cells) in the backhaul link using a relay for handover decision and uplink timing advance command in the RAR. For example, handover of a UE served by a relay is Msg1-free: the target gNB and the UE have enough information to enable the UE to receive the RAR directly with the HO command.

[0108] 2) Use the TDOA measured by the relay to determine the uplink timing advance for the entire group of UEs served by the relay. In an example, group switching is used.

[0109] 3) As an enhancement to conventional RAR processing, there are two optional embodiments of RAR processing: a) pre-configure a dedicated time slot for RAR to be sent by the target gNB; b) send RAR (with new RAR content) to the UE via the source gNB so that the UE can send Msg3 to the target gNB. The new RAR content can be modified to have a group-based TA. The new RAR content can also be sent via a more flexible dedicated UE-specific channel.

[0110] 4) There may be new signaling between the relay, source gNB, target gNB and UE to support relay-assisted mobility.

[0111] Now that an overview has been provided, further details are provided.

[0112] In addition to the SSB signals described above, there are other signals that the NCR can use for HO related measurements. For example, the repeater may choose to use other physical channel signals to perform measurements on power difference and arrival time difference. An example of such a signal may be the CSI-RS signals from the source and target gNBs, which are typically used for beam tracking or beam refinement purposes.

[0113] Another topic involves collecting the identities of UEs served by a relay. When source gNB 170-1 makes a HO decision based on measurements from a relay, the source gNB can act as a proxy for handing over multiple UEs served by a relay. The source gNB can identify the UEs served by the relay in a variety of ways. For example, consider the following.

[0114] 1) The source gNB 170-1 may assign a dedicated SSB index to the relay 130: The SSB may be transmitted on a separate beam and mapped with the SSB index as its identifier. Additionally, the RACH opportunity may have a unique mapping to each SSB index such that the UE indicates the SSB beam to which the UE prefers to connect by selecting the RO in which the UE transmits its RACH preamble. In more detail, the RO is a set of time-frequency resources that allow the UE to transmit a PRACH preamble. The RO is configured by the network via a broadcast channel for the cell. If a particular set of SSBs is dedicated for use through the NCR 130, the communication of the UE through the NCR 130 will be identified based on the selected RO in which the preamble is transmitted. In this case, L1 / L2 mobility can allow scenarios where the UE switches from a relay-based beam to a non-relay-based beam, or vice versa, without a full HO, but in this case the gNB still knows the beam identifier of each of its beams and which beams are transmitted over the NCR 130, so that whether the UE is connected on an NCR beam or a non-NCR beam is known at the gNB.

[0115] 2) Unique cell ID for communication through relays: NCR forwarding can be transparent to gNB 170, but gNB 170 should be aware of NCR 130 because relays are generally considered to be network nodes under operator control. In this case, using unique cell ID for SSB transmitted through NCR will clearly identify which UEs are using NCR because the UE will perform initial access to those specifically identified cells. In this case, connecting to and disconnecting from a cell will be identified by HO or cell reselection.

[0116] 3) Other implementations: While 1) and 2) are the most likely implementations for collecting the identity of the UE served by the repeater, other alternatives exist. It could be that the gNB could identify the connection going through the repeater based on some classification of the received RACH preamble. RF fingerprinting is an area of ​​research where a receiving device can authenticate a transmitting device by identifying unique features from the transmitted signal. If the NCR 130 has a unique RF fingerprint, then the RACH preamble sent by the NCR can be identified when compared to the RACH preamble sent by the UE. Other solutions could involve positioning or propagation delay comparison between the UE behind the repeater and the UE directly served by the gNB.

[0117] Now consider the TDOA measurements made by the repeater for timing advance. Figure 7 is a diagram illustrating ΔT and uplink propagation in an exemplary embodiment. Figure 7 It is shown in Figure 6beam and system (without train 510). Figure 7 , initially UE 110 is active and served by source gNB 170-1 via access beam 660 and backhaul beam 640 directed at the source gNB. Relay 130 maintains a timing reference to source gNB 170-1. Source gNB 170-1 maintains the UE’s uplink timing advance via conventional timing advance procedures. More specifically, due to the presence of the relay, the UE timing advance is determined with the goal of compensating for the propagation delay (T (p，UE-NCR) ), the internal delay of the repeater (T eq ) and the propagation delay of the backhaul link toward the source gNB (T (p，NCR-source) ) combination.

[0118] Similarly, in the case of a UE handover to target gNB 170-2, the UE timing advance may be determined with the goal of compensating for the propagation delay (T (p，UE-NCR )), internal delay in the repeater (T eq ) and the propagation delay (T (p，NCR-target) ) combination.

[0119] Due to T (p，UE-NCR) and T eq It is common before and after handover, so the required change in uplink timing for the UE can be determined by T alone. (p，NCR-source) and T (p，NCR-target) The difference between them is determined.

[0120] As the repeater 130 moves toward the target gNB 170-2, the repeater backhaul beam may have SSB signals from both the source gNB and the target gNB, and a receiver (e.g., Rx 162) may be used to determine these signals. Since the repeater is already synchronized with the source gNB and uses the source gNB as a reference, the repeater can measure the arrival time difference (i.e., ΔT) of the radio signals between the source SSB and the target SSB with a precise resolution of the sampling period Ts, which is proportional to the subcarrier spacing (SCS). In this example, ΔT is visually shown as measured relative to line segment 710, which corresponds to the distance between the repeater and the source gNB at a radial position projected onto the target backhaul beam 645. Here, ΔT represents the time it takes for the radio signal to traverse from the target gNB 170-2 to the line segment 710. More mathematically, ΔT may be characterized as the arrival time difference of the radio signals between the repeater and the first gNB and the repeater and the second gNB. If there is dispersion in the radio signal, a time difference is taken between the strongest paths from the repeater to the first gNB and from the repeater to the second gNB.

[0121] When the target gNB receives the ΔT from the source gNB over the Xn interface, the target gNB can use the ΔT information to calculate the actual timing advance message in the RAR. The value of the timing advance command field in the RAR has a coarser resolution than the sampling period rate. For example, in FR1 TDD, each timing advance step (one unit for the 12-bit value of the timing advance command) can have a resolution of eight samples, which translates to a distance of 19.5 meters (33.3μs / symbol / 4096 samples per symbol*3x10 8 m / s*8). This reiterates the robustness of the method since a slight movement in the UE in the access link will not change the RAR value.

[0122] Another discussion point concerns the DL / UL timing diagram for NCR assisted mobility. Figure 8 DL and UL timing for a single relay, two donor topology in an exemplary embodiment is shown.

[0123] Figure 8 The timing diagram of DL and UL transmissions between the source gNB and the target gNB and the UE via the NCR 130 is shown. As shown in the figure, the propagation delay T between the NCR and the UE p，UE-NCR is constant regardless of whether the UE is communicating with the source gNB or the target gNB.

[0124] As previously discussed, an exemplary embodiment proposes using a signal ΔT given as the TDOA of transmissions from both the source gNB and the target gNB. This measurement is available at the NCR 130 and can be reported directly to the source gNB and additionally forwarded to the target gNB via the Xn interface. Consider the following equation:

[0125] delta-T=T p，source -T p，target ,

[0126] in,

[0127] T p，source =T p，NCR-source +T eq +T p，UE-NCR ,as well as

[0128] T p，target =T p，NCR-target +T eq +T p，UE-NCR .

[0129] Here, T eq is the delay associated with the amplification and forwarding operation, including any additional signal processing. This delay is a function of the NCR capabilities and is independent of which equipment is at either end of the repeater link.

[0130] For UL transmission alignment, TA = 2·T p +T G , where T G is the guard interval to allow TDD switching and is link independent. And delta-T is constant for all UEs switching from source to target via NCR 130 .

[0131] Exemplary message flow diagrams are now described. These flow diagrams illustrate the operation of exemplary methods, the results of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and / or interconnected components for performing functions according to exemplary embodiments.

[0132] Fig. 9 An exemplary flow chart for relay-assisted mobility when Msg1 is bypassed is shown. Initially, relay 130 is time / frequency synchronized with source gNB 170-1 in the backhaul link, and UE 110 is served by source gNB 170-1 through relay 130. In addition, the UE is configured to use a common search space to search for DCI for RRC signaling for RACH procedures. During the process of periodic SSB scanning, relay 130 detects SSB signals from target gNB 170-2 and then determines the strongest SSB beam from the target.

[0133] In more detail, RAR content (such as RAR PDU) is configured to be sent in the PDSCH for the RACH procedure and is scheduled using DCI format1_0 (i.e., fallback) sent in the Type1 common search space. The UE must search this common search space for the RA-RNTI to correctly decode the PDSCH and complete the RACH procedure. Because the common search space is a shared resource and it may become a bottleneck, this process may be less efficient in terms of spectrum, but this approach is also more backward compatible because this is the traditional mechanism for completing the RACH procedure.

[0134] The steps for performing relay assisted mobility for this exemplary embodiment include the following.

[0135] Step 1, the source gNB sends a measurement control message to the relay. The measurement control message may include handover related information such as measurement object (e.g., SSB), reporting configuration, measurement identity (e.g., RSRP), quantization configuration (e.g., filtering), etc. The measurement control message may also include a configuration for measuring the time difference between the source gNB and the target gNB. The measurement control message may be an RRC message or any alternative control layer for controlling the operation of the relay.

[0136] Step 2, the repeater performs SSB search (L1 / L3 measurements for HO) during the SSB burst period and makes measurements for handover (e.g., power difference between source and target cells, referred to as ΔP) and time difference of arrival (ΔT) between source and target gNBs. The measurements may also include serving cell measurements. Furthermore, these measurements may be measurement events for the target cell, such as an A3 event, whereby the target cell is measured to be better offset than the current serving cell.

[0137] Step 3: The relay sends an SSB measurement report to the source gNB. The measurement report may include information such as the relay ID, target cell ID, and beam ID of the strongest beam, ΔP, and ΔT. The measurement report message may be an RRC message (L3 measurement) or a MAC CE message (L1 / L2 measurement).

[0138] Step 4: The source gNB makes a handover decision based on the measurement report from the relay. In addition, the source gNB 170-1 collects information for the UE group served by the relay, including their identities (e.g., C-RNTI in the source gNB) and their current timing advance (TA) and ΔT.

[0139] In step 5, the source gNB 170-1 sends a group handover request message to the target gNB 170-2. The group handover request message may include information such as the identity of the UE group, their timing advance (TA) and ΔT, for example in a single message. Note that the TA for each UE may be different, but the ΔT is common. The new TA for the target gNB should be the (current) TA of each UE (known by the source gNB) + ΔT. Optionally, many handover request messages may be sent to the target gNB 170-2, each of which includes information for individual UEs from the UE group.

[0140] “ΔT / TA” is based on the following. When performing a RACH procedure, the UE is provided with a timing advance, TA, which is an offset from the time when the UE should send an UL transmission relative to the time when it receives a DL transmission. In a traditional RACH, each UE would receive this update independently relative to its own DL RX timing. Alternatively, each UE may be provided with a timing offset relative to its previous TA (i.e., the TA provided by the source gNB), which is referred to herein as ΔT. Since this ΔT is only a function of the propagation delays from the source to the repeater and the target to the repeater, the ΔT will be the same value for each UE connected to the repeater.

[0141] Step 6, the target gNB 170-2 performs admission control and creates a Msg2 assignment for the UE.

[0142] In step 7, the target gNB 170-2 sends a Group Handover Request Confirm message to the source gNB 170-1. The Group Handover Request Confirm message may include information such as the identity of the UE group in the target gNB 170-2, the Msg2 assignment, and the time(s) (e.g., slot index) at which the handover is to start. Optionally, multiple Handover Request Confirm messages may be sent to the source gNB, where each Handover Request Confirm message includes information for a respective UE from the UE group.

[0143] Step 8: The source gNB sends an RRCReconfiguration message to each UE. The RRCReconfiguration message may include information such as the identity of the UE in the target gNB, Msg2 assignment, and the time to start the handover.

[0144] Step 9: The source gNB 170-1 sends a beam control message to the relay so that the backhaul beam switching is aligned with the cell switching performed by the UE. The beam control message may include information such as the relay ID and the backhaul beam configuration (e.g., the beam direction and time for triggering the beam switching).

[0145] Step 10, UE 110 achieves downlink synchronization with the strongest SSB signal from the target gNB and is ready to receive Msg2 based on the Msg2 assignment information from step 8. That is, Msg1 is skipped.

[0146] In more detail, in step 10, the UE synchronizes with the downlink of the target gNB 170-2 via the strongest SSB. It is not part of the random access procedure, which starts with the UE's first transmission in the uplink (i.e., Msg1, although this example skips Msg1). The UE is initially synchronized with the downlink of the source base station 170-1, and the uplink is also synchronized via the current timing advance (TA). After switching to the target gNB 170-2 (via handover), downlink and uplink synchronization needs to be reestablished. First, the UE needs to search in the downlink by finding the strongest SSB beam of the target base station and tracking the strongest SSB beam in time and frequency (i.e., synchronize with that beam). Once downlink synchronization is achieved, the UE 110 can correctly receive Msg2 (which is a downlink signal) from the target base station and then send Msg3 (uplink) in this embodiment ( Fig. 9 In another embodiment ( Fig.10 ), the content of Msg2 from the target base station is transmitted to the UE through the source gNB before the handover. In this case, the UE can send msg3 after achieving downlink synchronization, and the synchronization technology is the same as Fig. 9 and Fig.10 The synchronization technology is the same between them.

[0147] Msg1 (the first message in the random access procedure, which is sent by the UE) is used to find the timing advance from the UE to the target base station via the repeater. Since the repeater is installed on the train, the relative position of the repeater to the UE is somewhat stable (the TA value has a granularity that can tolerate small distances), but the distance of the repeater to the source / target base station will vary dramatically, the latter of which can be measured by the repeater as ΔT. Once ΔT and the original TA are known to the target base station, it can inform the UE of the new TA to achieve uplink synchronization with the target gNB (i.e., in Fig. 9 and Fig.10 In both embodiments, the UE may send Msg3) using the new TA notified to the UE before the handover.

[0148] Step 11, the target gNB sends Msg2 (RAR) to the UE. The RAR may include information such as UL grant for Msg3 and timing advance (TA) for the target gNB derived from the information from step 5.

[0149] Step 12: The UE sends Msg3 to the target gNB based on the UL grant and the TA from the RAR. Msg3 may include an RRCReconfigurationComplete message.

[0150] Step 13: The target gNB sends a UEContextRelease message to the source gNB to complete the handover.

[0151] In another embodiment of relay-assisted mobility, both Msg1 and Msg2 are bypassed, wherein the relevant content of Msg2 is sent by source gNB 170-1 to UE 110 before the handover, for example as part of the handover command, such as Fig.10 shown. Fig.10 With Fig. 9 Same starting conditions where the repeater performs power difference and timing measurements of the SSB signal and sends the measurement report to the source gNB.

[0152] However, the important Msg2 information is transmitted to the UE via the source gNB using a dedicated channel. This can be done because the source gNB has configured a dedicated search space for the connected UE and assigned a C-RNTI. This means that the gNB can schedule the PDSCH using DCI format1_1, which is more efficient than the fallback DCI (such as Fig. 9 ) is more flexible and does not require adding congestion to the common search space.

[0153] Another consideration is that there is a difference between signaling a new TA and using ΔT, which is a signaling detail. The following describes how this detail is implemented.

[0154] TA: This will be the same value sent in the RAR, but now just sent in different signaling such as a different PDU. This will be a UE-specific signal that provides the timing offset of the UL transmission from the UE relative to the DL Rx timing and can be sent as a dedicated signal from the source TA.

[0155] ΔT: This will be a group specific signal, where the group is all UEs connected to the mobile relay. Here, ΔT is the timing offset for UL transmissions to the target gNB relative to the timing offset for UL transmissions to the source gNB (old TA assignment). This value will be constant for all UEs connected to the relay, and can therefore be broadcasted in a signaling message to all UEs connected to the relay. One possible scenario is that ΔT is sent in a group broadcast, only to a limited group of UEs that are configured to look for the broadcast, for example.

[0156] Fig.10 The process in Fig. 9 One benefit of TSMC (compared to TSMC) is the increased spectral efficiency and flexibility that comes from using dedicated channels to configure the UE, but this also involves new signaling (e.g., new PDUs) that the UE will need to be able to receive.

[0157] Fig.10 and Fig. 9 The differences between include the following.

[0158] Step 6: The target gNB performs admission control and creates UL grants for the UE group for future Msg3 transmissions.

[0159] Step 7, the target gNB 170-2 sends a Group Handover Request Confirm message to the source gNB 170-1. The Handover Request Confirm message may include information such as the identity of the UE group in the target gNB 170-2, the UL grant for Msg3, and the (multiple) time points (e.g., time slot indices) at which the handover is to start. Optionally, multiple Handover Request Confirm messages may be sent to the source gNB 170-1, where each Handover Request Confirm message includes information from individual UEs for the UE group.

[0160] Step 8: The source gNB sends an RRCReconfiguration message to each UE. The RRCReconfiguration message may include information such as the identity of the UE in the target gNB, the UL grant for Msg3, and the time to start the handover.

[0161] Although this is characterized as being in the RRCReconfiguration message, this is only an option. RRCReconfiguration is typically an RRC layer message, while RAR is typically a MAC layer message. Fig.10 , the signal flow looks as if the two messages have been mixed together. While this is possible (e.g., given the newly defined RRCReconfiguration message), the ΔT / TA information element can be a (e.g., newly defined) MAC layer message sent separately from the RRCReconfiguration, as shown by reference numeral 1010. Note that the MAC layer message is received using a dedicated channel that has been configured by source gNB 170-1 for UE 110.

[0162] Fig.10 There is no RAR in this method because the method does not require RAR. Instead, in this method, the relevant RAR can be split and placed in different places. Generally, this information can be RRC signal, MAC signal or signaled from another layer.

[0163] Regarding the MAC layer, a MAC RAR is a collection of MAC subPDUs, each of which contains necessary information for a specific UE. The contents of a single subPDU are described below, where the contents are described first and then parenthetical comments ([…]) related to the contents are provided.

[0164] MAC Subtitle:

[0165] E: Indicates whether this PDU is the last one in the sequence [no dedicated signal is needed, as PDUs do not have to be aggregated but can be sent independently on a dedicated channel for each UE]

[0166] T: Indicates whether to include RAPID [Not required as this technique avoids the use of Msg1 and sends appropriate configuration to each UE on a dedicated channel]

[0167] R: Reserved bit, set to "0" [can be ignored]

[0168] BI: Used to resolve PRACH conflict (Msg1) [not required because Msg1 is not used in this method].

[0169] RAPID: PRACH preamble ID for msg1 [not needed as msg1 is bypassed]

[0170] subPDU:

[0171] Timing Advance Command (TAC): A new TA used to align UL transmissions from the UL to the target gNB [this may be the only information that needs to be sent as part of this new message, alternatively this may be a group-specific signal using ΔT instead of TAC].

[0172] UL Grant: UL transmission grant for RRC connection reestablishment request [This is useful if RRC reconfiguration is used before starting the handover procedure] Fig.10 Not strictly necessary for UE-to-gNB, but in some scenarios it may be preferable to simply have the UE initiate RRC re-establishment without requiring RRC reconfiguration from the source gNB, so it may make sense to include this]

[0173] TC-RNTI: Temporary UE identifier used until the target gNB can establish an RRC connection with the UE [Similar to the UL Grant, this is not necessary if the RRC Reconfiguration is sent from the source gNB, but may be necessary if the connection is reestablished directly between the UE and the target gNB]

[0174] Based on this, it can be said that Fig.10 The E, T, R, BI and RAPID fields of the subheader are removed in the method of , but this is just an example. UL grant and TC-RNTI can be optionally included to obtain more flexibility, and TAC or timing difference is actually the main element that should be sent.

[0175] Step 10, the UE achieves downlink synchronization with the strongest SSB signal from the target gNB and is ready to send Msg3 based on the Msg3 UL grant information from step 8. (Msg1 and Msg2 are skipped).

[0176] A description of capability signaling is now provided. To perform relay-assisted mobility, the network-controlled relay 130 may need to report to the donor gNB its ability to support differential measurements of physical channel signals so that the donor gNB node can set measurement configurations (e.g., measurement objects, periodicity, thresholds, hysteresis, etc.) for measurement reports to be sent by the relay.

[0177] Capability signaling may include at least the following parameters: -REPEATER_ID Repeater identification -repeater-measurementSupport-r18 ENUM {true} -repeater_measurementResources-r18 ●SSB Enum {true} ●CSI-RS Enum {true} -repeater_mesaurementCategory-r18 ●Difference value ■ Difference in signal power (eg, RSRP) Enum {true} ■ Difference in signal quality (eg, RSRQ) Enum {true} ■Difference in Arrival Times Enum {true}

[0178] To achieve this, connections and changes to the 3GPP specifications are described.

[0179] The NR relay specification (3GPP TS38.106) may need to be updated to include relays with the ability to support inter-cell measurements based on SSB signals and send measurement reports to the source donor.

[0180] The relay assisted handover signal flow as described above may need to be included in 3GPP TS38.331.

[0181] The modified random access procedure may affect 3GPP TS38.213.

[0182] The L2-based handover procedure in 3GPP TS38.321 may be affected.

[0183] Signaling on the Xn interface between the source node and the target node (3GPP TS38.422) may also be affected.

[0184] Benefits and technical effects include the following.

[0185] 1) Reduced interruption of user traffic for UEs served by the relay during handover, which provides a better user experience. This is very important for active users. More specifically,

[0186] A) It can be Msg1-free. That is, the repeater provides uplink timing advance.

[0187] i) The UE may be required to send RACH separately. This can avoid network congestion in RACH reception in gNB and L3 processing in 5G core.

[0188] B) This can be completely contention-free.

[0189] i) In legacy HO with Msg1, the number of contention-free preambles may be limited, and if the contention-free preambles are exhausted, the gNB will use contention-based preambles for HO, which may cause collisions and delays.

[0190] ii) In an exemplary embodiment, the access identity is passed via messaging and collisions can be avoided (eg using C-RNTI as in an alternative embodiment of RAR processing).

[0191] C) Due to optional enhancements to RAR reception, in some exemplary embodiments, no RAR window is required because the RAR timing (eg, slot offset) is preconfigured.

[0192] D) There may be less measurement overhead since one entity (relay) can perform HO related measurements, which avoids a large number of measurement reports and measurement gaps by individual UEs.

[0193] E) Group based handover can be performed which provides less signaling overhead and should be faster.

[0194] 2) Lower messaging overhead.

[0195] A) The measurements made by the relay in the backhaul link can be used to replace the large number of measurement reports made by multiple UEs if these UEs were to perform HO measurement reports individually.

[0196] B) Existing per-UE messaging can be extended to include UE groups (eg, UE context setup can be extended to include multiple UEs), thereby saving messaging overhead.

[0197] 3) Save power.

[0198] A) For the UE side:

[0199] i) No Msg1: The UE does not need to send Msg1, thus saving power.

[0200] ii) No RAR window is required. The UE does not need to blindly search for PDCCH with RA-RNTI in all DL slots within the RAR window. Two enhancements for RAR handling are proposed: a) the UE knows in advance which slot contains the RAR, and b) the content of the RAR is sent by the source gNB. Both do not require a RAR window.

[0201] iii) The UE may be preconfigured to receive the SSB for downlink synchronization at a specific time (e.g., symbol offset) of the expected (i.e., strongest) SSB. The UE saves power by not having to perform blind SSB scanning and searching in order to synchronize to the strongest SSB. Optionally, the UE may be pre-informed of the target cell id and beam id to facilitate synchronization, resulting in less processing.

[0202] B) On the gNB side:

[0203] i) Each UE does not need to perform a large amount of RACH preamble processing and each UL timing advance calculation.

[0204] ii) No processing power is required to handle the large number of measurement reports from various UEs.

[0205] 4) Except for the absence of Msg1, the exemplary embodiments may still use the same framework of Msg3, Msg4 and possibly Msg2 for the rest of the RACH procedure.

[0206] i) When it comes to repeater switching, this is more acceptable as there is no drastic change compared to conventional technology.

[0207] ii) It is fully compatible with some other HO related optimizations (e.g., 2-step / 4-step Rach, L1-L2 mobility, packet handover at higher layers, etc.).

[0208] Additional examples are below.

[0209] Example 1. A repeater comprising components for performing the following:

[0210] relaying communications between a plurality of user equipment and a first base station;

[0211] measuring a time difference between a signal received from a first base station and a signal received from a second base station;

[0212] performing cell measurement of a signal received from the first base station and a signal received from the second base station; and

[0213] Information indicating the measured time difference and the cell measurement is sent to the first base station.

[0214] Example 2. The repeater of Example 1, wherein communications between the plurality of user equipments and the first base station are relayed in a radio frequency domain,

[0215] And wherein the component is further configured to: perform a synchronization signal block search during a burst period for measuring time difference and for performing cell measurement.

[0216] Example 3. A repeater according to Example 1 or 2, wherein information indicating the measured time difference and cell measurement is sent to a first base station for switching of multiple user equipment from a first cell operated by the first base station to a second cell operated by a second base station, and wherein a signal received from the first base station is associated with the first cell, and a signal received from the second base station is associated with the second cell.

[0217] Example 4. A repeater according to any one of Examples 1 to 3, wherein:

[0218] Performing the cell measurement includes measuring a first power of a signal received from the first base station and a second power of a signal received from the second base station; or

[0219] Measuring the time difference includes measuring a time difference of arrival between a signal received from the first base station and a signal received from the second base station;

[0220] Example 5. A relay according to any one of Examples 1 to 4, wherein the information indicating the cell measurement includes a measurement event implemented by the cell measurement.

[0221] Example 6. The repeater of any one of Examples 1 to 5, wherein the component is further configured to perform:

[0222] receiving a Msg2 assignment from the first base station for use by each of the plurality of user equipments in a random access procedure skipping Msg1 between each of the user equipments and the second base station; and

[0223] The Msg2 assignment is relayed to each user equipment.

[0224] Example 7. The repeater of any one of Examples 1 to 5, wherein the component is further configured to perform:

[0225] receiving an uplink grant from the first base station for use by each of the plurality of user equipments in a random access procedure skipping Msg1 and Msg2 between each of the user equipments and the second base station; and

[0226] An uplink grant is relayed to each user equipment.

[0227] Example 8. The repeater of Example 7, wherein:

[0228] Receiving the uplink grant further includes: receiving a time difference or a timing advance used by each user equipment for uplink communication with the second base station; and

[0229] The relay uplink grant also includes: relaying the received timing advance or the received time difference to the user equipment.

[0230] Example 9. A device comprising a repeater as described in any one of Examples 1 to 8.

[0231] Example 10. A first base station comprising means for performing:

[0232] Communicate with multiple user devices through repeaters,

[0233] receiving information from the repeater, the information indicating a time difference measured by the repeater between a signal received from the first base station and a signal received from the second base station, and indicating a cell measurement performed by the repeater on the signal received from the first base station and the signal received from the second base station; and

[0234] A handover decision is made for a plurality of user equipments based at least on the received information indicative of the cell measurements.

[0235] Example 11. A first base station according to Example 10, wherein, in response to a switching decision made by the first base station for multiple user equipment from the first base station to the second base station based at least on received information indicating cell measurement, one or more switching request messages are sent to the second base station, and the one or more switching request messages include information for identifying the multiple user equipment and for enabling the second base station to determine the timing advance used by the multiple user equipment for uplink communication with the second base station.

[0236] Example 12. The first base station of Example 11, wherein the information used to enable the second base station to determine a timing advance used by a plurality of user equipments for uplink communication with the second base station comprises:

[0237] a time difference between a signal received from the first base station and a signal received from the second base station, as measured by the repeater; and

[0238] A timing advance for use by a plurality of user equipments for uplink communications with a first base station.

[0239] Example 13. A first base station according to Example 12, wherein the following is sent in a single switching request message: information identifying multiple user devices; a time difference measured by a repeater between a signal received from the first base station and a signal received from the second base station; and a timing advance used by multiple user devices for uplink communication with the first base station.

[0240] Example 14. The first base station of Example 12, wherein the one or more handover request messages include respective handover request messages corresponding to respective user equipments of the plurality of user equipments, and wherein the respective handover request messages include:

[0241] Information for identifying each user equipment of the plurality of user equipments;

[0242] The time difference between the signal received from the first base station and the signal received from the second base station measured by the relay, and the timing advance used by each user equipment for uplink communication with the first base station.

[0243] Example 15. The first base station of Example 11, wherein:

[0244] The component is further configured to perform: determining respective timing advances for the plurality of user equipment based on timing advances used by the plurality of user equipment for uplink communications with the first base station and based on a time difference measured by the repeater between a signal received from the first base station and a signal received from the second base station;

[0245] The one or more handover request messages include respective handover request messages corresponding to respective user equipments of the plurality of user equipments, and wherein each handover request message includes:

[0246] Information used to identify each user device;

[0247] The information enabling the second base station to determine the timing advances for the plurality of user equipments comprises the determined respective timing advances corresponding to the respective user equipments.

[0248] Example 16. The first base station of any one of Examples 11 to 15, wherein the component is further configured to perform:

[0249] receiving an indication that handover of each user equipment of the plurality of user equipments from the first base station to the second base station is confirmed by the second base station, the indication comprising an Msg2 assignment for use by each user equipment in a random access procedure of each user equipment and the second base station skipping Msg1; and

[0250] A message including Msg2 assignment is sent to each user equipment.

[0251] Example 17. The first base station of Example 14, wherein the component is further configured to perform:

[0252] sending to each user equipment a time difference between a signal received from the first base station and a signal received from the second base station measured by the repeater,

[0253] Wherein the transmission of the time difference is transmitted to each user equipment in a message comprising an uplink assignment, or the transmission is broadcast from the first base station and is intended for a group of user equipment of which each user equipment is a member.

[0254] Example 18. The first base station of Example 15, wherein the component is further configured to perform:

[0255] A timing advance used by each user equipment for uplink communication with the second base station is sent to each user equipment, wherein the timing advance is sent in a medium access control message using a search space specific to each user equipment.

[0256] Example 19. The first base station of any of Examples 17 or 18, wherein the component is further configured to perform:

[0257] receiving an indication that a handover of each user equipment of a plurality of user equipments from the first base station to the second base station is confirmed by the second base station, the indication comprising an uplink grant for use by each user equipment in a random access procedure of each user equipment and the second base station skipping Msg1 and Msg2; and

[0258] A message including an uplink grant is sent to each user equipment.

[0259] Example 20. An apparatus comprising a first base station according to any one of Examples 10 to 19.

[0260] Example 21. A repeater according to any one of Examples 1 to 8 or a first base station according to any one of Examples 10 to 19, wherein the component comprises:

[0261] at least one processor; and

[0262] At least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause execution of the apparatus.

[0263] Example 22. A method comprising:

[0264] relaying, by a repeater, communications between a plurality of user equipments and the first base station;

[0265] measuring, by the repeater, a time difference between a signal received from the first base station and a signal received from the second base station;

[0266] performing, by the repeater, cell measurement of a signal received from the first base station and a signal received from the second base station; and

[0267] Information indicating the measured time difference and the cell measurement is sent by the relay to the first base station.

[0268] Example 23. A method according to Example 22, wherein communications between multiple user equipment and the first base station are relayed in the radio frequency domain, and wherein the method further comprises: performing a synchronization signal block search during a burst period for measuring time differences and for performing cell measurements.

[0269] Example 24. A method according to Example 22 or 23, wherein information indicating the measured time difference and cell measurement is sent to a first base station for switching of multiple user equipment from a first cell operated by the first base station to a second cell operated by a second base station, and wherein the signal received from the first base station is associated with the first cell and the signal received from the second base station is associated with the second cell.

[0270] Example 25. The method of any one of Examples 22 to 24, wherein:

[0271] Performing the cell measurement includes measuring a first power of a signal received from the first base station and a second power of a signal received from the second base station; or

[0272] Measuring the time difference includes measuring a time difference of arrival between a signal received from the first base station and a signal received from the second base station;

[0273] Example 26. A method according to any one of Examples 22 to 25, wherein the information indicating the cell measurement includes a measurement event implemented by the cell measurement.

[0274] Example 27. The method of any one of Examples 22 to 26, wherein the method further comprises:

[0275] receiving a Msg2 assignment from the first base station for use by each of the plurality of user equipments in a random access procedure skipping Msg1 between each of the user equipments and the second base station; and

[0276] The Msg2 assignment is relayed to each user equipment.

[0277] Example 28. The method of any one of Examples 22 to 26, wherein the method further comprises:

[0278] receiving an uplink grant from the first base station for use by each of the plurality of user equipments in a random access procedure skipping Msg1 and Msg2 between each of the user equipments and the second base station; and

[0279] An uplink grant is relayed to each user equipment.

[0280] Example 29. The method of Example 28, wherein:

[0281] Receiving the uplink grant further includes: receiving a time difference or a timing advance used by each user equipment for uplink communication with the second base station; and

[0282] The relay uplink grant also includes: relaying the received timing advance or the received time difference to the user equipment.

[0283] Example 30. A method comprising:

[0284] The first base station communicates with multiple user equipments through a repeater,

[0285] receiving information from the repeater, the information indicating a time difference measured by the repeater between a signal received from the first base station and a signal received from the second base station, and indicating a cell measurement performed by the repeater on the signal received from the first base station and the signal received from the second base station; and

[0286] A handover decision is made for a plurality of user equipments based at least on the received information indicative of the cell measurements.

[0287] Example 31. A method according to Example 30, wherein, in response to a switching decision made by the first base station for multiple user equipment from the first base station to the second base station based at least on received information indicating cell measurement, one or more switching request messages are sent to the second base station, the one or more switching request messages including information for identifying the multiple user equipment and for enabling the second base station to determine a timing advance used by the multiple user equipment for uplink communication with the second base station.

[0288] Example 32. The method of Example 31, wherein the information used to enable the second base station to determine a timing advance used by a plurality of user equipments for uplink communication with the second base station comprises:

[0289] a time difference between a signal received from the first base station and a signal received from the second base station, as measured by the repeater; and

[0290] A timing advance for use by a plurality of user equipments for uplink communications with a first base station.

[0291] Example 33. A method according to Example 32, wherein the following is sent in a single switching request message: information identifying multiple user devices; a time difference measured by a repeater between a signal received from a first base station and a signal received from a second base station; and a timing advance used by multiple user devices for uplink communication with the first base station.

[0292] Example 34. The method of Example 32, wherein the one or more handover request messages include a respective handover request message corresponding to a respective user equipment of the plurality of user equipments, and wherein the respective handover request message includes:

[0293] Information for identifying each user equipment of the plurality of user equipments;

[0294] The time difference between the signal received from the first base station and the signal received from the second base station measured by the relay, and the timing advance used by each user equipment for uplink communication with the first base station.

[0295] Example 35. The method of Example 32, wherein:

[0296] The method further includes determining respective timing advances for the plurality of user devices based on timing advances used by the plurality of user devices for uplink communications with the first base station and based on a time difference measured by the repeater between a signal received from the first base station and a signal received from the second base station;

[0297] The one or more handover request messages include respective handover request messages corresponding to respective user equipments of the plurality of user equipments, and wherein each handover request message includes:

[0298] Information used to identify each user device;

[0299] The information enabling the second base station to determine the timing advances for the plurality of user equipments comprises the determined respective timing advances corresponding to the respective user equipments.

[0300] Example 36. The method of any one of Examples 32 to 35, wherein the method further comprises:

[0301] receiving an indication that handover of each user equipment of the plurality of user equipments from the first base station to the second base station is confirmed by the second base station, the indication comprising an Msg2 assignment for use by each user equipment in a random access procedure of each user equipment and the second base station skipping Msg1; and

[0302] A message including Msg2 assignment is sent to each user equipment.

[0303] Example 37. The method of Example 34, wherein the method further comprises:

[0304] sending to each user equipment a time difference between a signal received from the first base station and a signal received from the second base station measured by the repeater,

[0305] Wherein the transmission of the time difference is transmitted to each user equipment in a message comprising an uplink assignment, or the transmission is broadcast from the first base station and is intended for a group of user equipment of which each user equipment is a member.

[0306] Example 38. The method of Example 35, wherein the method further comprises:

[0307] A timing advance used by each user equipment for uplink communication with the second base station is sent to each user equipment, wherein the timing advance is sent in a medium access control message using a search space specific to each user equipment.

[0308] Example 39. The method of any one of Examples 37 or 38, wherein the method further comprises:

[0309] receiving an indication that a handover of each user equipment of a plurality of user equipments from the first base station to the second base station is confirmed by the second base station, the indication comprising an uplink grant for use by each user equipment in a random access procedure of each user equipment and the second base station skipping Msg1 and Msg2; and

[0310] A message including an uplink grant is sent to each user equipment.

[0311] Example 40. A computer program comprising code for performing a method as described in any one of Examples 22 to 39 when the computer program is run on a computer.

[0312] Example 41. A computer program according to Example 40, wherein the computer program is a computer program product comprising a computer readable medium carrying computer program code embodied therein for use with the computer.

[0313] Example 42. A computer program according to Example 40, wherein the computer program is directly loadable into an internal memory of the computer.

[0314] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0315] (a) hardware circuit implementation only (e.g., implementation only in analog and / or digital circuits), and

[0316] (b) a combination of hardware circuitry and software, for example (as applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) any portion of a hardware processor (including a digital signal processor) with software, software and memory that work together to enable a device (such as a mobile phone or server) to perform various functions.

[0317] (c) A hardware circuit and / or processor that requires software (e.g., firmware) for operation, such as a microprocessor or portion of a microprocessor, but the software may not be present when not needed for operation.

[0318] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, if applicable to the particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0319] The embodiments of this document may be implemented in software (executed by one or more processors), hardware (e.g., application specific integrated circuits), or a combination of software and hardware. In example embodiments, the software (e.g., application logic, instruction sets) is maintained on any of a variety of conventional computer-readable media. In the context of this document, a "computer-readable medium" can be any medium or component that can contain, store, communicate, propagate, or transport instructions for use by or in connection with an instruction execution system, apparatus, or device (such as a computer), where an example of a computer is, for example, a computer program product. Figure 1 Computer-readable media may include computer-readable storage media (e.g., memory 155 or other devices), which may be any medium or component that can contain, store, and / or transmit instructions for use by or in connection with an instruction execution system, apparatus, or device (such as a computer). Computer-readable storage media do not include propagating signals.

[0320] If desired, the different functions discussed herein may be performed in different orders and / or simultaneously with each other. In addition, if desired, one or more of the above-mentioned functions may be optional or may be combined.

[0321] Although various aspects of the invention are set out in the independent claims, further aspects of the invention comprise other combinations of features from the described embodiments and / or the dependent claims with features of the independent claims, and not just the combinations explicitly stated in the claims.

[0322] It is noted herein that although the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. On the contrary, several variations and modifications may be made without departing from the scope of the invention as defined in the appended claims.

[0323] The following abbreviations that may be found in the specification and / or drawings are defined as follows:

[0324] 3GPP Third Generation Partnership Project

[0325] 5G Fifth Generation

[0326] 5GC 5G Core Network

[0327] ADC Analog to Digital Conversion or Converter

[0328] AMF Access and Mobility Management Function

[0329] BS Base Station

[0330] CE control components

[0331] C-RNTI Cell Radio Network Temporary Identifier

[0332] CSI-RS Channel State Information-Reference Signal

[0333] CU Central Unit

[0334] DAC Digital to Analog Converter or Converter

[0335] DAPS Dual Active Protocol Stack

[0336] DCI Downlink Control Information

[0337] DL Downlink

[0338] DU Distributed Unit

[0339] eNB (or eNodeB) Evolved Node B (e.g., LTE base station)

[0340] EN-DC E-UTRA-NR Dual Connectivity

[0341] en-gNB or En-gNB A node that provides NR user plane and control plane protocol termination to the UE and acts as a secondary node in EN-DC

[0342] E-UTRA Evolved Universal Terrestrial Radio Access, also known as LTE radio access technology

[0343] gNB (or gNodeB) is a base station for 5G / NR, i.e., a node that provides NR user plane and control plane protocol termination to the UE and is connected to the 5GC via the NG interface.

[0344] HO Switchover

[0345] IAB Integrated Access and Backhaul

[0346] Id or ID

[0347] I / F Interface

[0348] LTE Long Term Evolution

[0349] MAC Media Access Control

[0350] MME Mobility Management Entity

[0351] MO measurement object

[0352] MT Mobile Terminal

[0353] NCR Network Controlled Repeaters

[0354] ng or NG Next Generation

[0355] ng-eNB or NG-eNB Next Generation eNB

[0356] NR New Radio

[0357] N / W or NW network

[0358] PCI Physical Cell Identifier

[0359] PDCCH Physical Downlink Control Channel

[0360] PDCH Physical Downlink Channel

[0361] PDCP Packet Data Convergence Protocol

[0362] PDSCH Physical Downlink Shared Channel

[0363] PDU Protocol Data Unit

[0364] PHY Physical Layer

[0365] RACH Random Access Channel

[0366] RAN Radio Access Network

[0367] RAPID Random Access Preamble ID

[0368] RAR Random Access Response

[0369] Rel Release

[0370] RF

[0371] RLC Radio Link Control

[0372] RNTI Radio Network Temporary Identifier

[0373] RO RACH Timing

[0374] RSRP Reference Signal Received Power

[0375] RSRQ Reference Signal Received Quality

[0376] RRH Remote Radio Head

[0377] RRC Radio Resource Control

[0378] RU Radio Unit

[0379] Rx Receiver

[0380] SCS Subcarrier Spacing

[0381] SDAP Service Data Adaptation Protocol

[0382] SGW Service Gateway

[0383] SMF session management functions

[0384] SNR Signal to Noise Ratio

[0385] SSB Synchronous Signal Block

[0386] SR Smart Repeater

[0387] TA Timing Advance

[0388] TAC Timing Advance Command

[0389] TC-RNTI Temporary Cell-RNTI

[0390] TDD Time Division Duplex

[0391] TDOA Time Difference of Arrival

[0392] TS Technical Specifications

[0393] Tx Transmitter

[0394] UE User Equipment (e.g., wireless, usually mobile)

[0395] UL Uplink

[0396] UPF User Plane Function

[0397] WI Work Item

Claims

1. A repeater comprising components for performing the following: relaying communications between a plurality of user equipment and a first base station; measuring a time difference between a signal received from the first base station and a signal received from a second base station; performing cell measurement of a signal received from the first base station and a signal received from the second base station; as well as Information indicating the measured time difference and the cell measurement is sent to the first base station.

2. The repeater of claim 1 , wherein the information indicating the measured time difference and the cell measurement is sent to the first base station for handover of the plurality of user equipment from a first cell operated by the first base station to a second cell operated by the second base station, and wherein the signal received from the first base station is associated with the first cell and the signal received from the second base station is associated with the second cell.

3. The repeater according to any one of claims 1 to 2, wherein: Performing the cell measurement includes measuring a first power of a signal received from the first base station and a second power of a signal received from the second base station; or Measuring the time difference includes measuring a time difference of arrival between a signal received from the first base station and a signal received from the second base station. 4 . The relay according to claim 1 , wherein the information indicating the cell measurement comprises a measurement event achieved by the cell measurement. 5 .

5. The repeater according to any one of claims 1 to 4, wherein the component is further configured to perform: receiving a Msg2 assignment from the first base station for use by each of the plurality of user equipments in a random access procedure skipping Msg1 between each of the user equipments and the second base station; and The Msg2 assignment is relayed to each of the user equipments.

6. The repeater according to any one of claims 1 to 4, wherein the component is further configured to perform: receiving an uplink grant from the first base station for use by each of the plurality of user equipments in a random access procedure skipping Msg1 and Msg2 between each of the user equipments and the second base station; and The uplink grant is relayed to each of the user equipments.

7. The repeater according to claim 6, wherein: The receiving the uplink grant further comprises: receiving the time difference or timing advance used by the respective user equipment for uplink communication with the second base station; and The relaying the uplink grant further comprises: relaying the received timing advance or the received time difference to the user equipment.

8. The repeater according to any one of claims 1 to 7, wherein the communication between the plurality of user equipments and the first base station is relayed in a radio frequency domain, And wherein the component is further configured to perform a synchronization signal block search during a burst period for measuring the time difference and for performing the cell measurement.

9. A device comprising the repeater according to any one of claims 1 to 8.

10. A first base station, comprising components for performing the following: Communicate with multiple user devices through repeaters, receiving information from the repeater, the information indicating a time difference measured by the repeater between a signal received from the first base station and a signal received from a second base station, and indicating a cell measurement performed by the repeater on the signal received from the first base station and the signal received from the second base station; and A handover decision is made for the plurality of user equipments based at least on the received information indicative of the cell measurements.

11. The first base station according to claim 10, wherein: In response to a handover decision made by the first base station for the multiple user equipment from the first base station to the second base station based at least on the received information indicating the cell measurement, one or more handover request messages are sent to the second base station, wherein the one or more handover request messages include information for identifying the multiple user equipment and for enabling the second base station to determine a timing advance used by the multiple user equipment for uplink communication with the second base station.

12. The first base station according to claim 11, wherein the information used to enable the second base station to determine the timing advance used by the plurality of user equipments for uplink communication with the second base station comprises: the time difference measured by the repeater between a signal received from the first base station and a signal received from the second base station; as well as A timing advance for use by the plurality of user equipments for uplink communications with the first base station.

13. A first base station according to claim 12, wherein the following are sent in a single handover request message: the information identifying the multiple user equipments; the time difference measured by the repeater between the signal received from the first base station and the signal received from the second base station; and the timing advance used by the multiple user equipments for uplink communication with the first base station.

14. The first base station according to claim 12, wherein the one or more handover request messages include respective handover request messages corresponding to respective user equipments of the plurality of user equipments, and wherein the respective handover request messages include: Information for identifying each user equipment of the plurality of user equipments; The time difference between a signal received from the first base station and a signal received from the second base station measured by the relay, and a timing advance used by the respective user equipment for uplink communication with the first base station.

15. The first base station according to claim 11, wherein: The component is further configured to perform: determining respective timing advances for the plurality of user equipment based on timing advances used by the plurality of user equipment for uplink communication with the first base station and based on the time difference measured by the repeater between a signal received from the first base station and a signal received from the second base station; The one or more handover request messages include respective handover request messages corresponding to respective user equipments of the plurality of user equipments, and wherein the respective handover request messages include: Information used to identify each user equipment; The information enabling the second base station to determine the timing advances for the plurality of user equipments comprises the determined respective timing advances corresponding to the respective user equipments.

16. The first base station of claim 14, wherein the component is further configured to perform: sending the time difference measured by the repeater between the signal received from the first base station and the signal received from the second base station to each user equipment, Wherein said transmission of said time difference is transmitted to said respective user equipment in a message comprising an uplink assignment, or said transmission is broadcasted from said first base station and is intended for a group of user equipments of which said respective user equipment is a member.

17. The first base station of claim 15, wherein the component is further configured to perform: A timing advance is sent to the respective user equipment for use by the respective user equipment for uplink communication with the second base station, wherein the timing advance is sent in a medium access control message using a search space specific to the respective user equipment.

18. The first base station according to any one of claims 16 or 17, wherein the component is further configured to perform: receiving an indication that a handover of each of the plurality of user equipments from the first base station to the second base station is confirmed by the second base station, the indication comprising an uplink grant for use by each of the user equipments in a random access process skipping Msg1 and Msg2 between each of the user equipments and the second base station; and A message including the uplink grant is sent to each of the user equipments.

19. An apparatus comprising the first base station according to any one of claims 10 to 18.

20. A repeater according to any one of claims 1 to 7 or a first base station according to any one of claims 10 to 18, wherein the component comprises: at least one processor; as well as At least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause execution of the apparatus.

21. A method comprising: relaying, by a repeater, communications between a plurality of user equipments and the first base station; measuring, by the repeater, a time difference between a signal received from the first base station and a signal received from a second base station; performing, by the repeater, cell measurement of a signal received from the first base station and a signal received from the second base station; as well as Information indicating the measured time difference and the cell measurement is sent by the relay to the first base station.

22. A method comprising: The first base station communicates with multiple user equipments through a repeater, receiving information from the repeater, the information indicating a time difference measured by the repeater between a signal received from the first base station and a signal received from a second base station, and indicating a cell measurement performed by the repeater on the signal received from the first base station and the signal received from the second base station; as well as A handover decision is made for the plurality of user equipments based at least on the received information indicative of the cell measurements.

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