Methods and devices for facilitating synchronized transmission from multiple transmission points

Abstract

A method for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the UE and comprises: obtaining (701, 703, 704) configuration related to detection of an offset associated with signals received from different transmission points; receiving (705) reference signals from two or more different transmission points; transmitting (709) a calibration report to the network indicative of the offset as detected based on the received reference signals, wherein the calibration report is 0 configured according to at least one report rule based on the configuration.

Description

[0001] METHODS AND DEVICES FOR FACILITATING SYNCHRONIZED TRANSMISSION FROM MULTIPLE TRANSMISSION POINTS

[0002] Technical field

[0003] This disclosure relates to methods and devices in a wireless communication system, in which wireless devices may communicate with a wireless network.

[0004] Specifically, solutions are provided for facilitating synchronization of signal transmission from a plurality of transmission points of the wireless network to the same wireless device.

[0005] Background

[0006] In radio communication systems, such as various generations provided through the 3rd Generation Partnership Project (3GPP), various specifications have been provided for setting up common rules for setting up and operating both a wireless radio interface between a wireless device and a network (NW), and various levels of operation of the network. In 3GPP documentation, a wireless device is commonly referred to as User Equipment (UE), a term that will be used throughout this disclosure. Such UEs are connectable to a core network by means of a Radio Access Network (RAN), which includes one or more network nodes, operative to provide radio access to UEs within a cell. Such network nodes may also be referred to as an access node or a base station, and various terms are used in 3GPP for different types of systems or specifications, such as gNB in New Radio (NR), developed to support 5G RAN. Each access node of the wireless network may comprise at least one Transmit / Receive Point (TRP), at which an antenna system of the access node is arranged for radio communication with UEs.

[0007] A well-established technology used in wireless communication is MIMO, Multiple-Input Multiple-Output, which uses an antenna system with multiple antennas at both the transmitter and receiver of each TRP to improve communication performance. This may enhance data rates, signal quality, and network efficiency. MIMO may be used to obtain increased data throughput by transmitting multiple data streams simultaneously using spatial diversity, also referred to as beamforming.A further development of the MIMO concept is so called DMIMO, Distributed Multiple-Input Multiple-Output, wherein multiple spatially separated antennas, or TRPs, are used to transmit and receive signals, to further enhance network performance. Other terms used for labelling this general wireless communication principle are cell-free MIMO (CF-MIMO), (CF-MIMO), CF massive MIMO, and Coordinated MultiPoint systems. For the sake of simplicity, the term DMIMO will be used herein to describe this general concept. Unlike, or in extension to, conventional MIMO, where antennas are co-located in an antenna system at a single TRP, DMIMO places antennas or antenna systems across different locations. Such a system configuration may, inter alia, help reducing dead zones and improve connectivity in challenging environments, and may support more UEs by reducing interference and enabling better frequency reuse.

[0008] A basic version of D-MIMO already exists in 5G and goes by the name of coherent joint transmission (CJT). However, various limitations of CJT in its current form must be overcome before this technology can genuinely meet requirements identified for 6G, which may include peak data rates of 200 Gbps and reliabilities of up to 99.99999%. One such limitation is the assumption of ideal, perfectly synchronized backhaul links between the TRPs. Challenges thus arise for avoiding disruption in synchronization, which may lead to, inter alia, reduced throughput, increased latency, decreased reliability, or loss of connectivity.

[0009] Summary

[0010] In view of these challenges, various solutions are provided herein and set out in the independent claims. Further aspects and examples of the proposed solution are set out in the dependent claims, in the following description, and in the drawings.

[0011] According to one aspect, the proposed solution relates to a method carried out in a UE for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to the UE, wherein the method comprises: obtaining configuration related to detection of an offset associated with signals received from different transmission points;

[0012] receiving reference signals from two or more different transmission points;transmitting a calibration report to the network indicative of the detected offset associated with the received reference signals. The calibration report may be configured according to at least one report rule based on the configuration.

[0013] Brief description of the drawings

[0014] Fig. 1 schematically illustrates a general setup of communication between a TRP of a wireless network and a UE in a wireless communication system.

[0015] Fig. 2 schematically illustrates a UE configured to operate according to various embodiments outlined herein.

[0016] Fig. 3 schematically illustrates a TRP of the wireless network, configured to operate according to various embodiments outlined herein.

[0017] Fig. 4 schematically illustrates a setup wherein a UE is configured to communicate with multiple TRPs, which may be configured according to DMIMO.

[0018] Fig. 5 shows a signaling diagram schematically illustrating various aspects related to reporting in association with continuous joint transmission from a plurality of TRPs to UE.

[0019] Fig. 6A shows an example of configuration of uplink control information for reporting delay offset.

[0020] Fig. 6B visualizes quantization of delay offset usable upon reporting according to Fig. 6A.

[0021] Fig. 7 shows a signaling diagram schematically illustrating various aspects of the proposed solution, in association with offset reporting to facilitate synchronization between downlink transmission from different TRPs.

[0022] Detailed description

[0023] The invention will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.It will be understood that, when an element is referred to as being “connected” to another element, it can be directly connected to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” to another element, there are no intervening elements present. Like numbers refer to like elements throughout. It will furthermore be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0024] Well-known functions or constructions may not be described in detail for brevity and / or clarity. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense expressly so defined herein.

[0025] Embodiments of the invention are described herein with reference to schematic illustrations of idealized embodiments of the invention. As such, variations from the shapes and relative sizes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes and relative sizes of regions illustrated herein but are to include deviations in shapes and / or relative sizes that result, for example, from different operational constraints and / or from manufacturing constraints. Thus, the elements illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention.

[0026] Before going into further detail, a general presentation is provided with reference to the drawings of the communication entities of the wireless system in which the proposed solution may be set out.Fig. 1 schematically illustrates a wireless communication system including a wireless network 100, and a UE 1 configured to wirelessly receive radio signals from the wireless network 100. The wireless network may be a radio communication network operating under general and specific regulations and limits published by the 3GPP, such as a New Radio (NR) network. The wireless network 100 may include a core network 110, which is connected to other networks 130, such as the Internet. The wireless network 100 further includes an access network, such as a RAN, which may comprise a plurality of access nodes, of which access node 120 is shown in Fig. 1. An access node is an entity executing the wireless connection with wireless UEs 10. As such, the access node 120 comprises or is connected to a Transmit / Receive Point (TRP) including an antenna arrangement, or antenna system, for transmitting and receiving radio signals. The access node 120 may also be referred to as a base station and may be a gNB.

[0027] Fig. 2 schematically illustrates an embodiment of the UE 1 for use in a wireless network 100 as presented herein, and for carrying out the method steps as outlined. The UE 1 may comprise a radio transceiver 213 for communicating with other entities of the radio communication network 100, such as the access node 120. The transceiver 213 may thus include a receiver and a transmitter for communicating by radio over an air interface.

[0028] The UE 1 may further comprise an antenna system 214, which may include one or more antennas, antenna ports or antenna arrays. The antenna system 214 is connected to the transceiver for wireless communication of radio signals. The antenna system 214 may be configured for beamforming. The antenna system 214 may thus be configured to employ an anisotropic sensitivity profile of the antenna system to communicate radio signals in a particular direction, so called beam steering.

[0029] The UE 1 further comprises logic circuitry 210 configured to control communication of data and control signals, via the radio transceiver 213, on a physical channel 140 with the wireless communication network 100. The logic circuitry 210 may further be configured to control the antenna system 214 for beamforming and beam steering.

[0030] The logic circuitry 210 may include a processing device 211, including one or multiple processors, microprocessors, data processors, co-processors, and / or some other type of component that interprets and / or executes instructions and / or data. The processing device 211 may be implemented as hardware (e.g., a microprocessor, etc.) ora combination of hardware and software (e.g., a system-on-chip (SoC), an applicationspecific integrated circuit (ASIC), etc.). The processing device 211 may be configured to perform one or multiple operations based on an operating system and / or various applications or programs.

[0031] The logic circuitry 210 may further include memory storage 212, which may include one or multiple memories and / or one or multiple other types of storage mediums. For example, the memory storage 212 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and / or some other type of memory. The memory storage 212 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.). The memory storage 212 is configured for holding computer program code, which may be executed by the processing device 211, wherein the logic circuitry 210 is configured to control the UE 1 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and / or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic circuitry 210.

[0032] Obviously, the UE 1 may include other features and elements than those shown in the drawing or described herein, such as a power supply, a casing, a user interface, sensors, etc., but these are left out for the sake of simplicity.

[0033] Fig. 3 schematically illustrates a radio node in the form of an access node 120 of the wireless network 100 as presented herein, and for carrying out the method steps as outlined. In some examples, a plurality of access nodes 120 may be configured to carry out synchronized transmission to a common, i.e., the same, UE 1, as will be exemplified with reference to Fig. 4. In such context, uplink transmission from said UE 1 may be carried out to one specific access node 120 among said plurality of access nodes, for connection with network 100. In some examples, various access points may thus be referred to as transmission points 120, which are at least configured for radio transmission and optionally for uplink reception. In some examples, the access node, or transmission point, may be a TRP. In various embodiments, the access node 120 is a base station for operation in the radio communication network 100, to serve one or more UEs, such as the UE 1.The access node 120 may comprise a wireless transceiver 313, such as a radio transceiver for communicating with other entities of the radio communication network 100, such as the terminal 10. The transceiver 313 may thus include a radio receiver and a radion transmitter for communicating through at least an air interface.

[0034] The access node 120 may further comprise, or be connected to, an antenna system 314, which may include a plurality of antennas, such as an antenna array. The antenna system 214 may be configured to control the radio transceiver to employ an anisotropic sensitivity profile to transmit radio signals in a particular transmit direction.

[0035] The access node 120 further comprises logic circuitry 310 configured to control the access node 120 to communicate with the UE 1 via the radio transceiver 313 on a physical channel 140.

[0036] The logic circuitry 310 may include a processing device 311, including one or multiple processors, microprocessors, data processors, co-processors, and / or some other type of component that interprets and / or executes instructions and / or data. Processing device 311 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an applicationspecific integrated circuit (ASIC), etc.). The processing device 311 may be configured to perform one or multiple operations based on an operating system and / or various applications or programs.

[0037] The logic circuitry 310 may further include memory storage 312, which may include one or multiple memories and / or one or multiple other types of storage mediums. For example, memory storage 312 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and / or some other type of memory. Memory storage 312 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.).

[0038] The memory storage 312 is configured for holding computer program code, which may be executed by the processing device 311, wherein the logic 310 is configured to control the access node 120 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and / or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic 310.The access node 120 may further comprise an interface 315, configured for communication with the core network 110. Obviously, the access node 120 may include other features and elements than those shown in the drawing or described herein, such as a power supply and a casing etc.

[0039] Fig. 4 illustrates an example of a setup in which signals transmitted by three TRPs: TRP1, TRP2, and TRP3 are controlled to combine coherently at the receive antennas 214 of UE 1. The drawing may be used to visualize a network which employs CJT. CJT was introduced in Rel-18 to enhance data rates supported by 5G networks. By allowing signals to combine coherently at the receiver, signal-to-noise ratio of the resulting composite link can be dramatically increased while reducing interference toward other UEs in the cell. In some examples, the solutions proposed herein may be set out in the context of a DMIMO system in which a plurality of UEs is served by a plurality of TRPs in the same time-frequency resources. Also such an example may be visualized by Fig. 4, where said three TRPs are shown to serve the same UE 1. In this context, each of said TRPs may be configured in accordance with the access node 120.

[0040] To enable coherent combining, at the UE 1, the network 100 must acquire precise channel state information (CSI) to construct precoding matrices applied by the collaborating TPRs. To this end, enhancements to CSI acquisition were introduced in Rel-18. However, said enhancements assumed ideal backhaul and synchronization between the TRPs. This assumption places quite stringent requirements on the time and frequency synchronization among the TRPs, particularly inter-site deployments or deployments with distributed remote radio heads (RRHs), which drives up the cost of rolling out and maintaining networks. It also limits the number of TRPs that can collaborate, as synchronization errors tend to grow for TRPs located further apart. To alleviate this restriction, Rel-19 has been tasked with introducing calibration of inter-TRP time misalignment and frequency / phase offset measurement and reporting, as identified in 3GPP document RP-242394. Various aspect and examples associated with CJT calibration reporting of delay offset, i.e., time delay offset between reception of signals from different TRPs, will be outlined going forward. For the sake of simplicity, focus will be on procedures facilitating calibrating away delay offsets between TRPs. Nevertheless, corresponding procedures may be configured for calibrating frequency offsets between TRPs and DL / UL phase offset differences for TDD reciprocity.Fig. 5 schematically illustrates the calibration procedure for facilitating synchronization, which comprises the following steps:

[0041] 501. The NW 100 configures the requested CJT calibration (CJTC) report(s). This step includes providing the UE 1 with a set of TRPs (e.g., TRP1, TRP2, TRP3) and associated reference signal (RS) time-frequency resources to measure, as well as configuration parameters. For the case of CJTC of delay offset, these parameters include: i) the range of the delay offsets that the UE can report and ii) the quantization level. Further parameters and associated parameter limits may be included.

[0042] 502. The TRPs transmit RSs. By measuring the RSs sent by different TRPs and comparing them, the UE 1 can estimate the relevant estimation parameters, such as delay offset, frequency offset, and DL / UL phase offset difference. To enable CJTC for delay offset, the TRPs may be configured with tracking reference signals (TRSs).

[0043] 503. According to the procedures suggested in Rel-19, CJTC reports can be triggered asynchronously, i.e., the NW 100 must explicitly trigger each report instance as needed, e.g., by activating a pre-configured trigger state via a DO transmission. The DO may also contain time-frequency resources to use by the UE 1 for sending the report requested by the trigger.

[0044] 504. The UE 1 prepares the requested CJTC report according to the configuration of step 501 and sends it to the NW 100 (via TRP1 exemplified in the drawing), e.g., using resources scheduled by the DO in step 503.

[0045] Examples of RRC (Radio Resource Control) parameters of said configuration are shown in Table 1 below, associated with delay offset.

[0046]

[0047] Table 1.

[0048] Herein, range of delay offset, AD, refers to a measure of time, whereas the values indicated for providing said measure refer to different configurable upper endpoints of the range. The values in this example are provided based on configured Cyclic Prefix(CP) length. Configurable ranges in this example are thus 0 to 0.5CP and 0 to 1CP. Values of ADsmaller than 0.5CP may further be possible, such as 0.25CP or 0.1CP. In other examples, the delay range may be expressed using other units representing time, such as in microseconds. The different configurations of the number of codepoints, MD, represents the granularity of indicating the offset (i.e., the delay), i.e., the quantization.

[0049] Table 2 below shows examples of parameters reported in the CJTC report of step 504. The report may be provided in an Uplink Control Information (UCI) message. Moreover, / VTRPG {2, 3, 4} denotes the number of TRPs configured by the NW 100.

[0050]

[0051] Table 2.

[0052] In one example configured according to what was outlined in tables 1 and 2, it may be assumed that the NW 100 configures the UE 1 with VTRP= 4 TRPs whose delay offsets are to be measured. It may further be assumed that AD= CP, and MD= 64. One of the TRPs may be indicated, or allowed to be selected by the UE 1, as a reference TRP, whose index may be denoted by nref. Note that two bits are needed to encode the UE selection of the reference TRP. The UE 1 computes the delay offset between each of the remaining TRPs and the reference TRP, i.e., the UE computes n, offset

[0053]

[0054] > >

[0055] where Dnis the estimated delay between the n-th TRP and the UE 1. The reported delay offset values are obtained by quantizing Dn offset, n = 1, ... , VTRP, n A nref, using B bits where B is such that MD= 2s. In other words, the higher the configured MDis, the more accurately the calculated delay offset can be quantized for a given time length AD. An inside / outside flag dnindicates whether the impulse response of the channel between the n-th TRP and the UE is within one CP window.Fig. 6A illustrates an example of the UCI message which may be reported in step 504. For the provided example, the message consists of 23 bits, where the UE 1 has set nref 0.

[0056] Fig. 6B schematically illustrates quantization of the delay offset. The quantization procedure uses MD— 1 same-size intervals in the range [0, dD] and assigns a codepoint to each of them. The MD-th codepoint is used to provide an ‘out-of-range’ indication to the NW. In this context, the UE 1 may deem a TRP to be ‘out-of-range’ if its delay offset from the reference TRP is larger than the maximum delay offset that can be reported, i.e., AD.

[0057] Although it is outside the scope of the proposed solution, it is worthwhile to briefly mention how the NW 100 uses the delay offset information, obtained in step 504. Upon receiving a CJT calibration report of the delay offset, the NW 100 precompensates PDSCH (Physical Downlink Shared Channel) transmissions to the UE 1 by the delay offset quantities reported for each of the TRPs - except for the reference TRP, to which no delay offset precompensation needs to be applied. Moreover, when reporting precoding matrix information (PMI) to the NW 100, the UE 1 must precompensate the received reference signals with the reported delay offsets. The UE 1 may send the PMI to the NW 100 using a CSI measurement report, which is different from CJT calibration reports.

[0058] Therefore, it can be understood that when the UE 1 reports an out-of-range indication, the NW 100 does not know how to precompensate the signals transmitted by the relevant TRP. Furthermore, if the value of the range parameter, AD, was configured as AD= CP, the UE might not be able to properly receive CJT transmissions from the TRPs as some signals may end up outside the CP window. Under such conditions, the quality of CJT transmissions may experience considerable degradation.

[0059] It may thus be noted that challenges arise in association with determining how the NW 100 should handle an ‘out-of-range’ indication from the UE 1. Currently, at least two possible options are considered. A first option includes that the NW 100 can trigger an RRC reconfiguration procedure. This procedure may entail configuring a new set of CJT TRPs and / or setting theDparameter to a larger value, if possible. For example, the parameterDmay be increased from 0.25CP to 0.5CP. The disadvantage of this method is that RRC implies slow signaling and thus disruptions in the DL data flows arelikely to occur. A second option is for the NW 100 to attempt to avoid the ‘out-ofrange’ situation for as long as possible by configuring dDto its maximum possible value, for example CP. However, to obtain a suitable resolution for the reported delay offsets, large values of MDmay also need to be configured, which leads to unnecessarily large payloads since, most of the time, a smallerDmay be sufficient to fit the delay offsets and, thus, smaller values of MDmay also be used. Now, the NW may countervail the increased payload overhead by reducing the frequency of the CJT calibration reports. This measure, however, also has an adverse effect: by reducing the frequency of the CJT calibration reports, one increases the probability of late detection of ‘out-ofrange’ events, which may cause severe disruptions of the CJT transmissions.

[0060] Based on the foregoing, the proposed solution provides a mechanism for facilitating synchronization of signal transmission from a plurality of transmission points to a UE 1. Specifically, various mechanisms are provided which serve to minimize the risk of deterioration or even disruptions of connectivity based on coherent joint transmission from two or more transmission points of the NW 100.

[0061] Fig. 7 schematically illustrates a signaling diagram, which depicts actions taken in, and signaling carried out between, the UE 1 and the network 100, in accordance with the proposed solution. In this context, the network 100 is represented by TRP1, TRP2 and TRP3, corresponding to Fig. 4.

[0062] According to one aspect, the proposed solution relates to a method for facilitating synchronization of signal transmission to a UE 1 from a plurality of transmission points of a wireless network 100. In some examples, the method is carried out in the UE 1 and may comprise one or more of the following three general steps I-III:

[0063] I. Obtaining 701, 703, 704 configuration related to detection of an offset associated with signals received from different transmission points.

[0064] In some examples, obtaining the configuration comprises receiving 701, 703 at least some information elements of the configuration from the network, which may include decoding said information elements.

[0065] In some examples, receiving information elements of the configuration may comprise receiving system information broadcast by the network 100. This may be included in the step 701 of information exchange in the drawing.

[0066] In some examples, receiving information elements of the configuration from the network comprises receiving 703 a message from the network, wherein the informationelements are dedicated for said UE. In some examples, said message is an RRC message. In some examples, the network is configured to transmit 703 such a message responsive to UE capabilities, obtained in the information exchange 701, are indicative of the UE 1 being capable of CJT.

[0067] In some examples, obtaining the configuration comprises retrieving 704 at least some predetermined information elements of the configuration from storage in the UE. Such predetermined information elements may have been stored in the UE, e.g., in memory 212, based on received 701 system information. In some examples, the predetermined information elements are prestored in the memory 212, and prescribed by a technical specification as a mandatory or optional feature. In some examples, the retrieved 704 predetermined information elements are usable in combination with the received 703 message.

[0068] In any of the mentioned examples, one information element of the configuration may be indicative of parameters to be reported by the UE associated with coherent joint transmission in the network 100.

[0069] In any of the mentioned examples, one information element of the configuration is indicative of at least one signal parameter to be detected.

[0070] In some examples, the signal parameter is at least one of delay, frequency, and UL / DL phase offset.

[0071] In any of the mentioned examples, one information element of the configuration is indicative of at least one offset parameter, to be reported.

[0072] In any of the mentioned examples, one information element of the configuration is indicative of an offset range, of a signal parameter, to be reported.

[0073] In any of the mentioned examples, one information element of the configuration is indicative of a granularity for indicating a value of the offset parameter.

[0074] In any of the mentioned examples, one information element of the configuration is indicative of at least two report configurations for configuring a calibration report to the network.

[0075] In any of the mentioned examples, one information element of the configuration is indicative of a manner of indicating, by the UE, a used report configuration for a calibration report to the network.

[0076] II. Receiving 705 reference signals from two or more different transmission points.In some examples, the configuration determines one or more signal parameters for the UE 1 to measure on the received signals.

[0077] In some examples, the configuration controls the UE 10 to detect the offset associated with the received reference signals.

[0078] In some examples, the configuration controls the UE 10 to detect one or more of time offset, frequency offset, and phase offset difference, between the received reference signals.

[0079] III. transmitting 709 a calibration report to the network indicative of the detected offset associated with the received reference signals.

[0080] The calibration report may be configured according to at least one report rule based on the configuration.

[0081] In some examples, one of said information elements of the configuration is indicative of the report rule.

[0082] In any of the mentioned examples, the configuration controls the UE 10 to indicate, in the calibration report, an offset value representing the offset, as detected by the UE 10 based on the received reference signals.

[0083] According to some aspects, the proposed solution further provides a method for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to a UE, wherein the method is carried out in the UE and comprises:

[0084] obtaining 701, 703, 704 configuration related to detection of an offset associated with signals received from different transmission points;

[0085] receiving 705 reference signals from two or more different transmission points; transmitting 709 a calibration report to the network indicative said offset as detected based on the received reference signals, wherein the calibration report is configured according to at least one report rule based on the configuration.

[0086] According to some aspects, the proposed solution further provides a method for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0087] configuring 701, 703 the UE with configuration related to detection of an offset associated with signals received from different transmission points;transmitting 705, for reception in the UE, reference signals from two or more different transmission points;

[0088] receiving 709, from the UE, a calibration report indicative of said offset as detected based on the transmitted reference signals, wherein the calibration report is configured according to at least one report rule based on the configuration.

[0089] It should be understood that not all actions and signaling steps shown in Fig. 7 need to be included in every example of the proposed solution. Indeed, different embodiments will be described going forward, with reference to the same signaling diagram.

[0090] A first embodiment relates to UE-initiated calibration reporting, which may be used in the context of transmitting 709 a CJT calibration report. With reference to the foregoing, the calibration report is configured according to at least one report rule, wherein the report rule is configured to trigger the UE to transmit the calibration report based on determining that at least one trigger criterion associated with said configuration is satisfied.

[0091] In a broad context, the first embodiment thus comprises a method carried out in a UE 1 which may be useful for facilitating synchronization of signal transmission to the UE 1 from a plurality of transmission points of a wireless network 100, such as in the context of CJT. The method according to the first embodiment may comprise:

[0092] obtaining 701, 703, 704 configuration associated with detection of an offset between signals received from different transmission points;

[0093] receiving 705 reference signals from two or more different transmission points; transmitting 709, based on determining that at least one trigger criterion associated with said configuration is satisfied for UE-initiated reporting, a calibration report to the network indicative of said offset as detected between the received reference signals.

[0094] Various aspects of the first embodiment are outlined below.

[0095] According to some examples, the method comprises detecting 707 that at least one trigger criterion for UE-initiated reporting is satisfied, and initiating the transmission 709 upon said detection 707.

[0096] One or each of the trigger criteria may be defined as a condition that, when fulfilled, triggers a CJT calibration report by the UE. In some examples, the network100 may configure 701, 703 the UE with one or more of said conditions. One or more of the conditions may be predetermined, and retrieved 704 from storage 212.

[0097] According to some examples, the configuration comprises an information element indicative of an instruction for the UE 1 of UE-initiated CJT calibration reporting. This information element may be obtained by any of the aforementioned methods 701, 703, 704.

[0098] According to some examples, an information element of the configuration comprises one or more trigger criterion or condition. This information element may be obtained by any of the aforementioned methods 701 or 703, but may typically be provided by receiving 704 a message from the network.

[0099] According to some examples, the at least one trigger criterion comprises that an offset of a signal parameter is detected to have changed more than a threshold value compared to a reference value. As long as the offset, e.g., delay offset, does not change beyond said threshold value, which may correspond to what the network 100 considers significant to generate a report, no reports need to be sent by the UE 1.

[0100] According to some examples, such a trigger criterion may be formulated as the UE 1 being triggered to transmit the report based on one or more Dnoffset, changing by an amount that exceeds a threshold ADth.

[0101] According to some examples, the reference value is an offset value of a most recent calibration report transmission by the UE, associated with the same signal parameter and transmission points, such as same TRPs.

[0102] According to some examples, the reference value is an offset value detected upon a previous reference signal transmission received by the UE, associated with the same signal parameter and transmission points. By way of example, the offset value detected upon an occasion 705-2 of receiving the reference signal is compared to the corresponding offset value detected upon a preceding occasion 705-2 of receiving the reference signal. One trigger criterion may thus comprise that the offset has changed more than the threshold value between said occasions 705-1 and 705-2.

[0103] According to some examples, the configuration is indicative of an offset range ADof a signal parameter, such as delay, frequency, and / or UL / DL phase offset difference, wherein the at least one trigger criterion comprises that an offset of said signal parameter is detected to be closer than a threshold value from an end point of said offset range.According to some examples, wherein said offset is a time delay offset, the end point is an upper end point of a time delay offset rangeD.

[0104] According to some examples, such a trigger criterion may be formulated as the UE 1 being triggered to transmit the report based on one or more delay offsets being ld, <5th, to the upper limit of the configured delay offset range, i.e.,

[0105]

[0106] > According to some examples, the at least one trigger criterion comprises that an amount of time has elapsed which exceeds a report threshold time value since a preceding calibration report transmission by the UE, e.g., that time AT > Tthhas elapsed since the last CJT calibration report sent by the UE 1, associated with the same transmission point.

[0107] According to some examples, the UE 1 monitors the delay offsets of the transmission points configured for CJT and sends a CJT calibration report to the network 100 whenever one or more trigger of the conditions, i.e., trigger criteria, are satisfied.

[0108] According to some examples, the trigger criterion configures the UE to comprise, in the calibration report, only detected offset values for which said at least one trigger criterion was satisfied, and / or only to the transmission points which transmitted the reference signals for which said at least one trigger criterion was satisfied. By means of the report only including those offsets for which a trigger condition is satisfied, payload size of the report may be optimized. For the remaining offsets, last reported offset values apply.

[0109] According to some aspects, the first embodiment further provides a method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0110] configuring 701, 703 the UE with configuration associated with detection of an offset between signals received from different transmission points;

[0111] transmitting 705 reference signals from two or more different transmission points for reception in the UE;

[0112] receiving 709 a calibration report, indicative of said offset as detected between said reference signals, wherein the configuration controls the UE to transmit thecalibration report based on the UE determining that at least one trigger criterion is satisfied for UE-initiated reporting.

[0113] The aspects and examples outlined above related to the first embodiment are equally applicable to the method as carried out in the network.

[0114] In some examples, the method is carried out in an access node 120, which may comprise or be connected to at least one of said transmission points TRP1, TRP2, TRP3.

[0115] The first embodiment as outlined above, wherein the UE 1 is configured to initiate calibration reporting based on at least one trigger criterion, provides an improved mechanism for allowing the network 100 to obtain and react to calibration reports prior to reaching an out-of-range scenario.

[0116] A second embodiment relates to the UE 1 being configured with more than one report configuration, wherein the UE 1 may indicate, to the network 100, which report configuration is used in the context of transmitting 709 a CJT calibration report. With reference to the foregoing, the calibration report is configured according to the report rule to indicate configuration of an offset range of a signal parameter, based on which the detected offset is indicated.

[0117] In a broad context, the second embodiment thus comprises a method carried out in a UE 1, which method may be useful for facilitating synchronization of signal transmission to the UE 1 from a plurality of transmission points of a wireless network 100, such as in the context of CJT. The method according to the second embodiment may comprise:

[0118] obtaining 701, 703, 704 configuration related to detection of an offset associated with signals received from different transmission points;

[0119] receiving 705 reference signals from two or more different transmission points; transmitting 709 a calibration report to the network indicative of said offset as detected based on the received reference signals,

[0120] wherein the calibration report is configured to indicate configuration of an offset range of a signal parameter, based on which the detected offset is indicated.

[0121] Various aspects of the second embodiment are outlined below.

[0122] According to some examples, the configuration is indicative of at least two report configurations for configuring the calibration report.According to some examples, the configuration further indicates transmission points or combinations of transmission points for which the UE is enabled to indicate used report configuration for indicating detected offset.

[0123] According to some examples, each report configuration is defined by a set of configuration parameters.

[0124] According to some examples, wherein one of said configuration parameters is offset range to use for indicating detected offset in the calibration report.

[0125] According to some examples, the at least two report configurations are indicative of different offset ranges of the same signal parameter.

[0126] According to some examples, the calibration report is configured to indicate the used report configuration.

[0127] According to some examples, each of the at least two report configurations comprise an associated report granularity, which may be indicated by number of codepoints MD, for quantizing a delay value.

[0128] According to some examples, between a couple of the at least two report configurations, the report configuration having a longer offset range has lower granularity.

[0129] According to some examples, the calibration report is configured to indicate the used report configuration by a flag contained in the calibration report. Said flag may indicate which of two or more different sets of configuration parameters, e.g., sets A and B, applies to the calibration report. The flag may comprise, or consist of, one bit in the calibration report.

[0130] According to some examples, each report configuration may be indicative of an associated report size of the calibration report.

[0131] According to some examples, the at least two report configurations may be indicative of the same report granularity but different offset ranges of the same signal parameter, wherein the calibration report has different associated report size based on the used report configuration.

[0132] According to some examples, the calibration report is configured to indicate the used report configuration by configuring the report size of the calibration report.

[0133] In some examples, the size, e.g., number of bits, of the calibration report may be telling of the report configuration being used. Thus, when the UE 1 is configured with two different report configurations with different associated report size, no extra flag bitis needed. By way of example, the network 100, e.g. one of the transmission points, may be configured to assign a fixed number of resources (e.g., a fixed number of resource blocks) for receiving 709 the calibration report. Rate matching can then be applied to "fit" the report into the given set of resources. Thus, a different amount of redundancy would be used depending on the report size, which may indicate the report size and thus the used report configuration. Based on established report configuration, indicated delay in the calibration report may be associated to the correct delay range.

[0134] According to some examples, the configuration configures the UE 1 to indicate the detected offset based on the smallest selectable offset range of a signal parameter, such as time delay or frequency, within which the detected offset fits.

[0135] According to some examples, the transmission 709 is initiated upon receiving 707 a report trigger from the network 100. This may be carried out in accordance with what was described with reference to Fig. 5.

[0136] According to some examples, the transmission 709 is initiated upon detecting 707 that at least one trigger criterion for UE-initiated reporting is satisfied, and initiating the transmission 709 upon said detection 707. This may be carried out in accordance with what was described for the first embodiment.

[0137] According to some examples of the second embodiment, the UE 1 is configured with at least two report configurations for configuring the calibration report. This may involve configuring two or more different values of the range parameter,D. In accordance with some of the examples outlined above, the UE 1 may be configured with both AD= 0.25CP and AD= 0.5CP. According to some examples, the UE 1 is, for each CJT calibration report, configured to use the smallest selectable offset range, i.e., AD= 0.25CP, if the delay offsets fit within the range or interval [0, 0.25CP], or dD= 0.5CP, otherwise.

[0138] To indicate the used one of the two configured report configurations to the network 100, the UE may include an extra flag in the CJT calibration report, as described. As further exemplified above, an alternative way of indicating the used report configurations to the network 100 may be to configure the size of the calibration report accordingly.

[0139] According to some examples, as described above, each report configuration may comprise a set of parameters. By way of example, at least two sets of parameters are configured for the UE 1 to select from. By way of example, the different configuredparameter set may be {AD= 0.25CP, MD= 64} and {AD= 0.5CP, MD= 256}, or {4D= 0.1 CP, MD= 64} and {4D= 0.5 CP, MD= 64}. In the latter example, the granularity is reduced if the longer 4Dis used and there is a clear edge of configuring two usable sets: one high granularity for small AD, and one low granularity in case a large 4Dis needed to fit the detected offset. By configuring MDin addition to the range 4D, reduced payload size may be obtained when larger range is applied, compared to using the same MD.

[0140] According to some aspects, the second embodiment further provides a method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0141] configuring 701, 703 the UE with configuration associated with detection of an offset between signals received from different transmission points;

[0142] transmitting 705 reference signals from two or more different transmission points for reception in the UE;

[0143] receiving 709, from the UE, a calibration report to the network indicative of said offset as detected based on said reference signals,

[0144] wherein the calibration report is configured to indicate configuration of an offset range of a signal parameter, based on which the detected offset is indicated.

[0145] The aspects and examples outlined above with respect to the UE 1 related to the second embodiment are equally applicable to the method as carried out in the network.

[0146] In some examples, the method is carried out in an access node 120, which may comprise or be connected to at least one of said transmission points TRP1, TRP2, TRP3.

[0147] The second embodiment as outlined above, wherein the UE 1 is configured to select and indicate, in the calibration report, an offset range of a signal parameter, provides an improved mechanism for allowing the network 100 to obtain and react to calibration reports prior to reaching an out-of-range scenario.

[0148] A third embodiment relates to the UE 1 facilitating synchronization upon the UE 1 determining an ‘out-of-range’ situation, with respect to the obtained configuration for calibration reporting.As has been explained in the foregoing, when an ‘out-of-range’ indication is reported in the transmission of the 709 calibration report, the network 100 and the UE 1 become out-of-synch. The network 100 no longer knows the delay offset used by the UE 1 to precompensate received reference signals for computing the PMI of the associated PDSCH. Consequently, the network side (of the associated PDSCH) and UE side (of the reference signals associated with PMI calculation) precompensations may differ. In fact, the behavior of the network 100 and the UE 1 when such an event occurs is currently left undefined.

[0149] In broad context, the third embodiment comprises a method carried out in a UE 1, which method may be useful for facilitating synchronization of signal transmission to the UE 1 from a plurality of transmission points of a wireless network 100, such as in the context of CJT. The method according to the third embodiment may comprise: obtaining 701, 703, 704 configuration related to detection of an offset associated with signals received from different transmission points;

[0150] receiving 705 reference signals from two or more different transmission points; transmitting 709, to the network, a calibration report configured to indicate said offset as detected based on at least some of the received reference signals;

[0151] transmitting 711 a further message to the network,

[0152] wherein, upon a detected offset of a signal parameter not fitting within a configured offset range, the UE applies offset precompensation of some of the received reference signals using an assumed predetermined offset, i.e., offset value, of said signal parameter for computing said further message.

[0153] According to some examples, receiving 705 reference signals may include receiving a first signals, e.g., TRSs, configured for establishing the calibration report, and second signals used for computing said further message. The second signals may be the same as the fist signals. In other examples, the second signals are different from the first signals. In some examples, the second signals are CSI-RS.

[0154] According to some examples, the calibration reports comprises an out-of-range indication for the offset, to indicate that the detected offset does not fit within the configured offset range.

[0155] According to some examples, the signal parameter is at least one of time delay and frequency.According to some examples, said predetermined offset is a latest reported offset value within the configured offset range. This may refer to the latest report offset value before the reporting of an "out-of- range" event,

[0156] According to some examples, said predetermined offset is a maximum offset value of the configured offset range. This may include a maximum delay offset value, i.e., AD.

[0157] According to some examples, said further message is a Channel State Information, CSI, measurement report.

[0158] According to some examples, computing said further message comprises computing a report of Precoding Matrix Information, PMI.

[0159] According to some examples, the further message is transmitted based on report criterion, such as a configured time or periodicity of reporting.

[0160] According to some examples, the further message is transmitted based on report criterion for PMI reporting.

[0161] The third embodiment thus involves an agreement between the network 100 and the UE 1, to apply an assumed predetermined offset, upon the UE 1 not being able to report the detected offset within the configured offset range.

[0162] According to some examples, this agreement is indicated by the configuration as obtained in the UE 1 in any of the steps 701, 703, 704.

[0163] According to some examples, this agreement is applied as the mentioned predetermined rule.

[0164] This embodiment provides that, while the use of the predetermined assumed offset cannot permanently solve the problem at hand, it can temporarily minimize the impact of the ‘out-of-range’ event. This is accomplished by enforcing the assumed predetermined delay value for precompensation to the network 100 and the UE 1. This may facilitate reception of PDSCH packets, as indicated by step 715 in Fig. 7, at least while or until the network 100 executes an RRC reconfiguration procedure 717, if so required or deemed appropriate by the network 100. Rather than dropping packets and optionally assigning new transmission points for CJT in an immediate RRC reconfiguration procedure 717, successful transmission 715 of already buffered packets, e.g., on PDSCH, has a good chance of succeeding even when using the assumed predetermined delay value, since an ‘out-of-range’ event is unlikely to occur without the delay offset still being close to the maximum range.According to some aspects, the third embodiment further provides a method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0165] configuring 701, 703 the UE with configuration associated with detection of an offset between signals received from different transmission points;

[0166] transmitting 705 reference signals from two or more different transmission points for reception in the UE;

[0167] receiving 709, from the UE, a calibration report configured to indicate said offset as detected based on at least some of said reference signals;

[0168] receiving 711 a further message from the UE;

[0169] transmitting 715 data to the UE,

[0170] wherein, upon the calibration report not including a value representing a detected offset of a signal parameter, the network applies 713 offset precompensation using an assumed predetermined offset of said signal parameter for transmitting 715 the data.

[0171] In some examples, applying 713 offset precompensation may comprise configuring precoding based on the assumed predetermined offset.

[0172] In some examples, said further message was computed by the UE using said assumed predetermined offset.

[0173] In some examples, the further message is a PMI report.

[0174] In some examples, wherein the calibration report indicates a value representing detected offset of the signal parameter, the network applies 713 offset precompensation using the indicated offset of said signal parameter for transmitting 715 the data.

[0175] In some examples, the calibration reports comprises an out-of-range indication for the offset, to indicate that the calibration report does not include a value representing detected offset.

[0176] In some examples, the method is carried out in an access node 120, which may comprise or be connected to at least one of said transmission points TRP1, TRP2, TRP3. The aspects and examples outlined above with respect to the UE 1 related to the third embodiment are equally applicable to the method as carried out in the network 100.

[0177] Various details and aspects related to the proposed solution have been outlined in the foregoing. It shall be noted that any of the three embodiments described, and theassociated examples, may be used in combination. The proposed solution may further be embodied in accordance with any combination of the items set out below, and in accordance with the appended claims.

[0178] Item 1. A method for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the UE and comprises:

[0179] obtaining (701, 703, 704) configuration related to detection of an offset associated with signals received from different transmission points;

[0180] receiving (705) reference signals from two or more different transmission points; transmitting (709) a calibration report to the network indicative of said offset as detected based on the received reference signals, wherein the calibration report is configured according to at least one report rule based on the configuration.

[0181] Item 2. The method of item 1, wherein the report rule is configured to trigger the UE to transmit the calibration report based on determining that at least one trigger criterion associated with said configuration is satisfied.

[0182] Item 3. A method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the UE and comprises:

[0183] obtaining (701, 703, 704) configuration associated with detection of offset between signals received from different transmission points;

[0184] receiving (705) reference signals from two or more different transmission points; transmitting (709), based on determining that at least one trigger criterion associated with said configuration is satisfied for UE-initiated reporting, a calibration report to the network indicative said offset as detected between the received reference signals.

[0185] Item 4. The method of item 2 or 3, wherein the at least one trigger criterion comprises that an offset of a signal parameter is detected to have changed more than a threshold value compared to a reference value.

[0186] Item 5. The method of item 4, wherein the reference value is an offset value of a most recent calibration report transmission by the UE, associated with the same signal parameter and transmission points.Item 6. The method of item 4, wherein the reference value is an offset value detected upon a previous reference signal transmission received by the UE, associated with the same signal parameter and transmission points.

[0187] Item 7. The method of any of items 2-6, wherein the configuration is indicative of an offset range of a signal parameter, wherein the at least one trigger criterion comprises that an offset of said signal parameter is detected to be closer than a threshold value from an end point of said offset range.

[0188] Item 8. The method of any of items 3-7, wherein the signal parameter is at least one of time delay, frequency, and UL / DL phase.

[0189] Item 9. The method of item 7, wherein said offset is a time delay offset, and wherein the end point is an upper end point of a time delay offset range.

[0190] Item 10. The method of any of items 2-9, wherein the at least one trigger criterion comprises that an amount of time has elapsed which exceeds a report threshold time value since a preceding calibration report transmission by the UE.

[0191] Item 11. The method of any of items 2-10, wherein the trigger criterion configures the UE to comprise, in the calibration report, only detected offset values for which said at least one trigger criterion was satisfied, and / or only to the transmission points which transmitted the reference signals for which said at least one trigger criterion was satisfied.

[0192] Item 12. The method of any preceding item, wherein the calibration report is configured according to the report rule to indicate configuration of an offset range of a signal parameter, based on which said offset as detected is indicated.

[0193] Item 13. A method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the UE and comprises:

[0194] obtaining (701, 703, 704) configuration associated with detection of an offset between signals received from different transmission points;

[0195] receiving (705) reference signals from two or more different transmission points; transmitting (709) a calibration report to the network indicative of said offset as detected based on the received reference signals,

[0196] wherein the calibration report is configured to indicate configuration of an offset range of a signal parameter, based on which the detected offset is indicated.Item 14. The method of item 12 or 13, wherein the configuration is indicative of at least two report configurations for configuring the calibration report.

[0197] Item 15. The method of item 12 or 13, wherein the configuration is indicative of at least two report configurations comprising different offset ranges of the same signal parameter, wherein the calibration report is configured to indicate the used report configuration.

[0198] Item 16. The method of item 14 or 15, wherein the configuration indicates transmission points or combinations of transmission points for which the UE is enabled to indicate used report configuration for indicating detected offset.

[0199] Item 17. The method of any of items 14-16, wherein each of the at least two report configurations comprise an associated report granularity.

[0200] Item 18. The method of item 17, wherein, between a couple of the at least two report configurations, the report configuration having a longer offset range has lower granularity.

[0201] Item 19. The method of any of items 12-18, wherein the UE is configured to indicate the detected offset based on the smallest selectable offset range of a signal parameter, within which the detected offset fits.

[0202] Item 20. The method of any preceding item, further comprising:

[0203] transmitting (711) a further message to the network,

[0204] wherein, upon a detected offset of a signal parameter not fitting within a configured offset range associated with the calibration report, the UE applies offset precompensation of at least some of the received reference signals using an assumed predetermined offset of said signal parameter for computing said further message.

[0205] Item 21. A method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the UE and comprises:

[0206] obtaining (701, 703, 704) configuration associated with detection of an offset between signals received from different transmission points;

[0207] receiving (705) reference signals from two or more different transmission points; transmitting (709), to the network, a calibration report configured to indicate said offset as detected based on at least some of the received reference signals;

[0208] transmitting (711) a further message to the network,wherein, upon a detected offset of a signal parameter not fitting within a configured offset range, the UE applies offset precompensation of at least some of the received reference signals using an assumed predetermined offset of said signal parameter for computing said further message using.

[0209] Item 22. The method of item 20 or 21, wherein said predetermined offset is a latest reported offset value within the configured offset range.

[0210] Item 23. The method of item 20 or 21, wherein said predetermined offset is a maximum offset of the configured offset range.

[0211] Item 24. The method of any of items 20-23, wherein said further message is a Channel State Information, CSI, measurement report.

[0212] Item 25. The method of any of items 20-24, wherein computing said further message comprises computing a report of Precoding Matrix Information, PMI.

[0213] Item 26. The method of any of items 20-25, comprising:

[0214] configuring (710) precoding based on the assumed predetermined offset to receive the further message.

[0215] Item 27. The method of any preceding item, wherein obtaining the configuration comprises receiving at least some information elements of the configuration from the network.

[0216] Item 28. The method of any preceding item, wherein obtaining the configuration comprises retrieving at least some predetermined information elements of the configuration from storage in the UE.

[0217] Item 29. The method of any preceding item, wherein the method is carried out to obtain coherent joint transmission to the UE.

[0218] Item 30. A method for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0219] configuring (701, 703) the UE with configuration related to detection of an offset associated with signals received from different transmission points;

[0220] transmitting (705), for reception in the UE, reference signals from two or more different transmission points;

[0221] receiving (709), from the UE, a calibration report indicative of said offset as detected based on said reference signals, wherein the calibration report is configured according to at least one report rule based on the configuration.Item 31. A method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0222] configuring (701, 703) the UE with configuration associated with detection of an offset between signals received from different transmission points;

[0223] transmitting (705) reference signals from two or more different transmission points for reception in the UE;

[0224] receiving (709) a calibration report, indicative of detected offset between said reference signals, wherein the configuration controls the UE to transmit the calibration report based on the UE determining that at least one trigger criterion associated with said configuration is satisfied for UE-initiated reporting.

[0225] Item 32. A method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0226] configuring (701, 703) the UE with configuration associated with detection of an offset between signals received from different transmission points;

[0227] transmitting (705) reference signals from two or more different transmission points for reception in the UE;

[0228] receiving (709), from the UE, a calibration report to the network indicative of said offset as detected based on said reference signals,

[0229] wherein the calibration report is configured to indicate configuration of an offset range of a signal parameter, based on which the detected offset is indicated.

[0230] Item 33. A method for managing synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:

[0231] configuring (701, 703) the UE with configuration associated with detection of offset between signals received from different transmission points;

[0232] transmitting (705) reference signals from two or more different transmission points for reception in the UE;

[0233] receiving (709), from the UE, a calibration report configured to indicate said offset as detected based on at least some of said reference signals;

[0234] receiving (711) a further message from the UE,

[0235] transmitting (715) data to the UE,wherein, upon the calibration report not including a value representing detected offset of a signal parameter, the network applies offset precompensation using an assumed predetermined offset of said signal parameter for transmitting the data.

Claims

CLAIMS1. A method for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the UE and comprises:obtaining (701, 703, 704) configuration related to detection of an offset associated with signals received from different transmission points;receiving (705) reference signals from two or more different transmission points; transmitting (709) a calibration report to the network indicative of said offset as detected based on the received reference signals, wherein the calibration report is configured according to at least one report rule based on the configuration.

2. The method of item 1, wherein the report rule is configured to trigger the UE to transmit the calibration report based on determining that at least one trigger criterion associated with said configuration is satisfied.

3. The method of item 2, wherein the at least one trigger criterion comprises that an offset of a signal parameter is detected to have changed more than a threshold value compared to a reference value.

4. The method of item 3, wherein the reference value is an offset value of a most recent calibration report transmission by the UE, associated with the same signal parameter and transmission points.

5. The method of item 3, wherein the reference value is an offset value detected upon a previous reference signal transmission received by the UE, associated with the same signal parameter and transmission points.

6. The method of any of items 2-6, wherein the configuration is indicative of an offset range of a signal parameter, wherein the at least one trigger criterion comprises that an offset of said signal parameter is detected to be closer than a threshold value from an end point of said offset range.

7. The method of any of items 2-6, wherein the signal parameter is at least one of time delay, frequency, and UL / DL phase.

8. The method of item 6, wherein said offset is a time delay offset, and wherein the end point is an upper end point of a time delay offset range.

9. The method of any of items 2-8, wherein the at least one trigger criterion comprises that an amount of time has elapsed which exceeds a report threshold time value since a preceding calibration report transmission by the UE.

10. The method of any of items 2-9, wherein the trigger criterion configures the UE to comprise, in the calibration report, only detected offset values for which said at least one trigger criterion was satisfied, and / or only to the transmission points which transmitted the reference signals for which said at least one trigger criterion was satisfied.

11. The method of any preceding item, wherein the calibration report is configured according to the report rule to indicate configuration of an offset range of a signal parameter, based on which said offset as detected is indicated.

12. The method of item 11, wherein the configuration is indicative of at least two report configurations for configuring the calibration report.

13. The method of item 11, wherein the configuration is indicative of at least two report configurations comprising different offset ranges of the same signal parameter, wherein the calibration report is configured to indicate the used report configuration.

14. The method of item 12 or 13, wherein the configuration indicates transmission points or combinations of transmission points for which the UE is enabled to indicate used report configuration for indicating detected offset.

15. The method of any of items 12-14, wherein each of the at least two report configurations comprise an associated report granularity.

16. The method of item 15, wherein, between a couple of the at least two report configurations, the report configuration having a longer offset range has lower granularity.

17. The method of any of items 11-16, wherein the UE is configured to indicate the detected offset based on the smallest selectable offset range of a signal parameter, within which the detected offset fits.

18. The method of any preceding item, further comprising:transmitting (711) a further message to the network,wherein, upon a detected offset of a signal parameter not fitting within a configured offset range associated with the calibration report, the UE applies offset precompensation of at least some of the received reference signals using an assumed predetermined offset of said signal parameter for computing said further message.

19. The method of item 18, wherein said predetermined offset is a latest reported offset value within the configured offset range.

20. The method of item 18, wherein said predetermined offset is a maximum offset of the configured offset range.

21. The method of any of items 18-20, wherein said further message is a Channel State Information, CSI, measurement report.

22. The method of any of items 18-21, wherein computing said further message comprises computing a report of Precoding Matrix Information, PMI.

23. The method of any of items 18-22, comprising:configuring (710) precoding based on the assumed predetermined offset to receive the further message.

24. The method of any preceding item, wherein obtaining the configuration comprises receiving at least some information elements of the configuration from the network.

25. The method of any preceding item, wherein obtaining the configuration comprises retrieving at least some predetermined information elements of the configuration from storage in the UE.

26. The method of any preceding item, wherein the method is carried out to obtain coherent joint transmission to the UE.

27. A method for facilitating synchronization of signal transmission from a plurality of transmission points of a wireless network to a User Equipment, UE, wherein the method is carried out in the network and comprises:configuring (701, 703) the UE with configuration related to detection of an offset associated with signals received from different transmission points;transmitting (705), for reception in the UE, reference signals from two or more different transmission points;receiving (709), from the UE, a calibration report indicative of said offset as detected based on said reference signals, wherein the calibration report is configured according to at least one report rule based on the configuration.

28. The method of claim 27, wherein the configuration controls the UE to transmit the calibration report based on the UE determining that at least one trigger criterion associated with said configuration is satisfied for UE-initiated reporting.

29. The method of claim 27, wherein the calibration report is configured to indicate configuration of an offset range of a signal parameter, based on which the detected offset is indicated.

30. The method of claim 27, further comprising:receiving (711) a further message from the UE;transmitting (715) data to the UE,wherein, upon the calibration report not including a value representing detected offset of a signal parameter, the network applies offset precompensation using an assumed predetermined offset of said signal parameter for transmitting the data.

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