WO2024156366A1

WO2024156366A1 - Timing synchronization enhancement for a network

Info

Publication number: WO2024156366A1
Application number: PCT/EP2023/052037
Authority: WO
Inventors: Dhruvin PATEL; Alexey SHAPIN; Torsten DUDDA; Zhenhua Zou
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2023-01-27
Filing date: 2023-01-27
Publication date: 2024-08-02

Abstract

A method, network node and wireless device (WD) for timing synchronization enhancement for networks are disclosed. According to one aspect, a method in a WD includes determining a propagation delay compensation (PDC) accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates. The method also includes transmitting the determined PDC accuracy measurements to the network node.

Description

TIMING SYNCHRONIZATION ENHANCEMENT FOR A NETWORK

TECHNICAL FIELD

The present disclosure relates to wireless communications, and in particular, to timing synchronization enhancement for a network.

BACKGROUND

The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD), as well as communication between network nodes and between WDs. The 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks.

5G-time sensitive networking (TSN) integrated networks are foreseen to support future Industrial Internet of things (loT) applications covering a wide range of communication services. The 5G system today supports TSN time synchronization functions using a quality of service (QoS) flow (within a packet data unit (PDU)- session) dedicated for relaying generalized precision time protocol (gPTP) signaling carried within Ethernet frames. The 5G system is modelled as a time aware system compliant IEEE standard 802. IAS. This ensures accurate measurement of 5G residence time experienced during delivery of gPTP signaling from the TSN grand master (GM) to TSN end stations. There are typically two-time synchronization processes running in parallel in an integrated 5G-TSN network:

1. 5GS synchronization; and

2. TSN time synchronization.

For the most demanding applications, time errors introduced when relaying gPTP signaling between the TSN GM clock and a TSN end station may be as low as 1 microsecond in a 5G-TSN integrated network. 3GPP Technical Specification Group Service and System Aspects (TSG SA) Working Group WG1 (SAI) has defined 900ns as the allowable error contribution of 5G systems within the 1 micro second end-to-end limitation. Support of mobility in integrated 5G-TSN network

Mobility is a fundamental aspect to be considered when integrating a 5G system with TSN networks. Mobility in smart manufacturing encompasses mobile robots and automated guided vehicles (AGV). In a large factory, such AGV may operate in an area not covered by single base station or a single transmission reception point (TRP). In this case, the WD will be required to handover its connection between different base stations or TRPs. In such scenarios, end-to-end (E2E) time synchronization in integrated 5G-TSN network, where such WDs are mobile, must be supported.

Support for wide area time synchronization beyond 5G

Moving toward 6G, it is envisioned the such deterministic communication ensured by 5G-TSN integration will be expanded for wide area networks. In discussions about 6G, there may be found requirements on supporting time synchronization among widely scattered devices with no distance limitation comparable to that of an industrial closed network. Such feature of time synchronization over a wide area network may support actuation of a cyber physical system.

Legacy layer 3 handover mechanism

The legacy Open Systems Interconnection (OSI) Layer 3 (referred to herein as “layer 3” or “L3”) mobility mechanism includes the following handover (HO) procedure where a WD is required to follow the “break before make” principle of operation due to being unable to simultaneously support Rx/Tx operation in two different cells:

1. The WD is in connected mode with the source network node. The source network node decides based on the layer 3 (L3) radio resource control (RRC) measurement report to handover WD to the target network node;

2. If the target network node admits the WD, a handover acknowledgement indication is sent to the source network node;

3. Source network node sends HO command (RRC message) to WD;

4. The WD performs procedure for switching the cell. This includes the WD resetting medium access layer (MAC), performing PRACH, re-establishing REC layer, re-establishing PDCP and changing security keys (if needed); and

5. After successful attachment, the WD sends target network node a HO completed notification using RRC signaling. There are two main processes running in the procedure. The first process is the handover triggering process. Here, the WD performs periodically reference signal received power (RSRP)/reference signal received quality (RSRQ) measurement based on the reference signals from serving and strongest neighboring cells. The second process is the handover process which is performed independently of the data transmission and needs to be fast enough to avoid excessive mobility related interruption of the user plane data transmission. FIG. 1 is an example of a legacy layer 3 handover mechanism.

L1/L2 mobility

Support of multi panel transmissions in 5G NR enables physical layer mobility such that the WD may not interrupt connections. Rather, the WD may be moved between base stations logically representing one cell with the same parameters. In 3GPP Technical Release 15 (3GPP Rel-15), intra-cell multi-TRP transmission is supported so that the WD may switch the communication from one TRP to another TRP. In 3GPP Rel-17, inter-cell multi-TRP transmission is supported, while the anchoring cell does not change (i.e., no handover). There is ongoing discussion on specify mobility based on OSI layer 1/layer 2 (L1/L2) signaling instead of L3 signaling.

5G time resiliency

There is currently ongoing discussion as to how to inform the WD and Application Function (AF) about the network time synchronization status. Some proposals describe how the WD and AF are being informed by the 5G system concerning the degradation of the timing failures. Considering the mobility scenario where WD may be connected and handed over to any base station in the network, the 5G RAN must ensure that time synchronization requirements are met. However, there is no such mechanism available. Propagation delay compensation

Delivery of internal 5G reference time over the radio network is an essential component in supporting an internal 5G end-to-end time synchronization solution.

One mechanism specified by 3GPP is based on the existing synchronized operation inherent to the 5G radio access network, where the WD and base station maintain synchronization for NR frame transmission. These frames are identified by system frame number (SFN). The base station (gNB) acquires the internal 5G reference time value from the 5G GM and maintains this acquired 5G reference time on an ongoing basis as well as periodically projecting the value it will have when a specific reference point in the system frame structure occurs at the BS antenna reference point (ARP). A System Information Block (SIB)/ Radio Resource Control (RRC) unicast message embeds this information that includes the internal 5G reference time value and the corresponding reference point (reference SFN) and transmits this information to a WD. The frequency of this message may depend on implementation.

A challenge to distributing reference timing is how to compensate the propagation delay over the radio interface. Depending on the cell size, it may be necessary to adjust the 5G reference time to reflect the downlink propagation delay experienced by a WD at the point in time to which the 5G reference time applies. Hence, compensation for propagation delays is an important function and depends upon on the cell size and target end-to-end synchronization requirement.

A round-trip time (RTT)-based method may be utilized to estimate the propagation delay from network node to WD. It is based on the 3GPP physical layer measurement capabilities. This mechanism may be controlled by the network node higher layers and leads to precise estimation of the propagation delay (PD).

In 3 GPP Rel-17, the two methods considered for determining PD have been the Timing Advance (TA) based method considered in 3 GPP Rel-16 and an alternative Round-Trip Time (RTT) based method. It should be noted that the RTT based method is the only method that may satisfy the 900 ns error budget requirement for the case of two radio interfaces in the end-to-end path (i.e., a Grandmaster clock at an end station connected to a WD).

A Timing Advance command is typically utilized in cellular communication for uplink transmission synchronization. It may be classified as two types:

1. In the beginning, at connection setup, an absolute timing advance command is communicated to a WD in the medium access control (MAC) packet data unit (PDU) Random Access Response (RAR) or in the Absolute Timing Advance Command MAC Control Element (CE) of the message B (MSGB); and

2. After connection setup, a relative timing correction may be sent to a WD using a Timing Advance Command MAC CE (e.g., WDs may move or there may be multi-path that changes with a changing environment).

The downlink Propagation Delay may be estimated for a given WD by (a) first summing the TA value indicated by the RAR (random access response) or the latest subsequent TA value sent using the MAC CE and (b) taking some portion of the total TA value resulting from summation of all the TA values (e.g., assuming, the downlink and uplink propagation delays are essentially the same, 50% could be used).

Round trip time-based methods is facilitated using the propagation delay measurements of both downlink (DL) and uplink (UL) paths. The framework itself is based on the existing definitions of WD receive-transmit (Rx -Tx) time difference and network node Rx - Tx time difference introduced for the purpose of positioning. Both network node-based propagation delay compensation (PDC) (i.e., network node precompensation) and WD-based PDC are supported in the 3GPP Rel-17, which may be selected via RRC. The WD and the network node are responsible to measure the Rx-Tx time difference at the WD and the network node, correspondingly. The PD is the summation of the two time difference measurements divided by two. Upon receiving a configuration of DL reference signals (i.e., either positioning reference signal (PRS) or channel state information reference signal (CSLRS) for tracking (i.e., tracking reference signal (TRS))) for PDC, the WD starts to measure the WD-side Rx-Tx time difference.

According to the 3 GPP standards, for WD-based PDC:

• The WD measures on DL reference signals (PRS or TRS), sends UL reference signals (SRS), receives the network node-rx-tx time difference, and with its own calculated WD rx-tx time difference, the WD calculates the propagation delay estimate, and applies it to the received reference time;

For network node-based PDC:

• The WD measures on DL reference signals (PRS or TRS), sends UL reference signals (SRS), calculates its own WD rx-tx time difference, and sends it to the network node, then the network node calculates the network node rx-tx time difference and the network node calculates the propagation delay estimate and applies it to the reference time transmitted to the WD; and

• The WD rx-tx time difference measurement is reported by an explicit request. The request may be one shot or periodic. The smallest periodicity is 80 milliseconds. FIG. 2 is an example of WD-based PDC (from Figure 16.8-1 of the 3GPP Technical Standard (TS) 38.300 V17.0.0).

In a network node with multi-TRP, only a single TRP is used to deliver the time and calculate the PD. For RTT-based PDC, the transmission of DL TRS/PRS, UL sounding reference signal (SRS) and reference time information are associated with a same TRP.

The radio link is one of the major contributors for time uncertainty introduced when using the 5G time reference delivery mechanism introduced by 3 GPP. Therefore, the accuracy of measuring 5G residence time used to adjust TSN GM clocks relayed through a 5G system is directly affected.

A wide range of industrial applications require time synchronization mechanisms. To support such requirement, 5G standards have introduced a mechanism through which an accurate time reference is delivered to all the connected WDs. The most demanding time synchronization error requirement is 900 ns, which is imposed between ingress and egress of the 5G system (e.g., two WDs). With 3GPP Rel-18, timing of the 5G system to be used by the connected device (e.g., smart grid, financial sector) to increase the resiliency of their own timing has been considered. This will push the 5G time error budget even lower.

So far there is no specification or feature being discussed within 3GPP which ensures wide area time synchronization considering mobility of the devices.

Current handover mechanisms do not take into consideration the time error budget of the 5G-TSN integrated network or any other industrial application time error budget requirement. Also, current candidate cell selection methods do not support cell selection based on the time error budget requirement and stability radio link characteristics, which indirectly ensure time reference delivery with stable accuracy. Furthermore, when multiple transmission-reception points (TRPs) are available, it is unclear which TRP is selected and how it is used for propagation delay compensation.

In other words, the WD may be in reach of different base stations and antennas (TRPs) with different radio conditions and parameters which indirectly affects propagation delay and resulting time error budget.

SUMMARY Some embodiments advantageously provide methods, network nodes and wireless devices for timing synchronization enhancement for networks.

In some embodiments, a network is configured to select a base station and antenna (TRP) for the WD to ensure a stable link and to maintain a time error budget for time synchronization applications running on higher layers.

Methods are disclosed to select the best reference signal path (herein defined as an antenna, TRP, beam or cell to be used for propagation delay compensation to achieve an accurate time synchronization between a WD and the network. As further described below, in some embodiments, a method includes measurements for propagation delay compensation accuracy by the WD, measurement reporting to a network node, network selection of a best antenna/TRP or cell and reconfiguration of the WD.

According to one aspect, a method in a wireless device, WD, configured to communicate with a network node is provided. The method includes determining a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates; and transmitting the determined PDC accuracy measurements to the network node.

According to this aspect, in some embodiments, the reference signal path is one of a transmission and reception point, TRP, a cell, a beam and an antenna. In some embodiments, the method includes receiving from the network node an indication of a reference signal path to be used for PDC. In some embodiments, the method includes selecting a reference signal path for PDC from a preconfigured list of reference signal paths based at least in part on a measurement condition specified by the network node. In some embodiments, the measurement condition is a reference signal measurement exceeding a first threshold. In some embodiments, the method includes deactivating a previously activated reference signal path for PDC. In some embodiments, the method includes transmitting a first indication of a signal to interference plus noise ratio, SINR, upon which the PDC accuracy measurements are based. In some embodiments, the method includes receiving from the network node a second indication of a serving cell to use for PDC accuracy measurements. In some embodiments, the method includes, in an event of a handover of the WD to another cell, determining a PDC accuracy measurement for each of the at least one candidate reference signal path after the handover. According to another aspect, a wireless device, WD, configured to communicate with a network node is provided. The WD includes processing circuitry configured to determine a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates. The WD also includes a radio interface in communication with the processing circuitry and configured to transmit the determined PDC accuracy measurements to the network node.

According to this aspect, in some embodiments, the reference signal path is one of a transmission and reception point, TRP, a cell, a beam and an antenna. In some embodiments, the radio interface is configured to receive from the network node an indication of a reference signal path to be used for PDC. In some embodiments, the processing circuitry is configured to select a reference signal path for PDC from a preconfigured list of reference signal paths based at least in part on a measurement condition specified by the network node. In some embodiments, the measurement condition is a reference signal measurement exceeding a first threshold. In some embodiments, the processing circuitry is configured to deactivate a previously activated reference signal path for PDC. In some embodiments, the radio interface is configured to transmit an first indication of a signal to interference plus noise ratio, SINR, upon which the PDC accuracy measurements are based. In some embodiments, the radio interface is configured to receive from the network node a second indication of a serving cell to use for PDC accuracy measurements. In some embodiments, the processing circuitry is further configured to, in an event of a handover of the WD to another cell, determine a PDC accuracy measurement for each of the at least one candidate reference signal path after the handover.

According to yet another aspect, a method in a network node configured to communicate with a wireless device, WD, is provided. The method includes receiving a propagation delay compensation, PDC, accuracy measurement for each of at least one transmission and reception point, reference signal path, based at least in part on a number of propagation delay estimates performed by the WD. The method includes selecting at least one candidate reference signal path for use by the WD for PDC, the selecting being based at least in part on the received PDC accuracy measurements. The method also includes transmitting to the WD an indication of the selected at least one candidate reference signal path for use by the WD for PDC. According to this aspect, in some embodiments, the reference signal path is one of a transmission and reception point, TRP, a cell, a beam and an antenna. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC is further based at least in part on a signal to interference plus noise ratio, SINR, upon which the received PDC accuracy measurements are based. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC includes determining a PDC measurement accuracy based at least in part on the received PDC accuracy measurements. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC is further based at least in part on a topology of a network comprising the network node. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC further includes determining a list of candidate reference signal paths ranked according to at least one criteria. In some embodiments, the method includes triggering a cell change when a current reference signal path being used by the WD for PDC results in a less accurate PDC estimate than another candidate in the list of candidate reference signal paths. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC includes determining an integral metric for each candidate reference signal path of the at least one candidate reference signal path, the integral metric being based at least in part on a weighting of selection criteria. In some embodiments, the method includes pre-configuring the WD with a list of candidate reference signal paths and at least one condition for selection of a candidate reference signal path from the list for use by the WD for PDC. In some embodiments, the at least one condition includes a downlink reference signal being greater than a first threshold. In some embodiments, the method includes, in an event of a handover of the WD to another cell, configuring the WD to determine a PDC accuracy measurement for each of the at least one candidate reference signal path after the handover. In some embodiments, the method includes determining a stability of synchronization accuracy based at least in part on the received PDC accuracy measurements, and triggering a cell change when the stability of synchronization accuracy falls below a second threshold.

According to another aspect, a network node configured to communicate with a wireless device, WD, is provided. The network node includes a radio interface configured to receive a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path, based at least in part on a number of propagation delay estimates performed by the WD. The network node also includes processing circuitry in communication with the radio interface and configured to select at least one candidate reference signal path for use by the WD for PDC, the selecting being based at least in part on the received PDC accuracy measurements. The radio interface is further configured to transmit to the WD an indication of the selected at least one candidate reference signal path for use by the WD for PDC.

According to this aspect, in some embodiments, the reference signal path is one of a transmission and reception point, TRP, a cell, a beam and an antenna. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC is further based at least in part on a signal to interference plus noise ratio, SINR, upon which the received PDC accuracy measurements are based. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC includes determining a PDC measurement accuracy based at least in part on the received PDC accuracy measurements. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC is further based at least in part on a topology of a network comprising the network node. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC further includes determining a list of candidate reference signal paths ranked according to at least one criteria. In some embodiments, the processing circuitry is further configured to trigger a cell change when a current reference signal path being used by the WD for PDC results in a less accurate PDC estimate than another candidate in the list of candidate reference signal paths. In some embodiments, selecting the at least one candidate reference signal path for use by the WD for PDC includes determining an integral metric for each candidate reference signal path of the at least one candidate reference signal path, the integral metric being based at least in part on a weighting of selection criteria. In some embodiments, the processing circuitry is further configured to pre-configure the WD with a list of candidate reference signal paths and at least one condition for selection of a candidate reference signal path from the list for use by the WD for PDC. In some embodiments, the at least one condition includes a downlink reference signal being greater than a first threshold. In some embodiments, the processing circuitry is further configured to, in an event of a handover of the WD to another cell, configure the WD to determine a PDC accuracy measurement for each of the at least one candidate reference signal path after the handover. In some embodiments, the processing circuitry is further configured to: determine a stability of synchronization accuracy based at least in part on the received PDC accuracy measurements; and trigger a cell change when the stability of synchronization accuracy falls below a second threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is an example of a legacy layer 3 handover mechanism;

FIG. 2 is an example of WD-based PDC;

FIG. 3 is a schematic diagram of an example network architecture illustrating a communication system connected via an intermediate network to a host computer according to the principles in the present disclosure;

FIG. 4 is a block diagram of a host computer communicating via a network node with a wireless device over an at least partially wireless connection according to some embodiments of the present disclosure;

FIG. 5 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for executing a client application at a wireless device according to some embodiments of the present disclosure;

FIG. 6 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for receiving user data at a wireless device according to some embodiments of the present disclosure;

FIG. 7 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for receiving user data from the wireless device at a host computer according to some embodiments of the present disclosure;

FIG. 8 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for receiving user data at a host computer according to some embodiments of the present disclosure; FIG. 9 is a flowchart of an example process in a network node for timing synchronization enhancement for networks; and

FIG. 10 is a flowchart of an example process in a wireless device for timing synchronization enhancement for networks.

DETAILED DESCRIPTION

Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to timing synchronization enhancement for networks. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Like numbers refer to like elements throughout the description.

As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. 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 will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication. In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and/or wireless connections.

The term “network node” used herein may be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi -standard radio (MSR) radio node such as MSR BS, multi-cell/multicast coordination entity (MCE), integrated access and backhaul (IAB) node, relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node.

In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The WD herein may be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as wireless device (WD). The WD may also be a radio communication device, target device, device to device (D2D) WD, machine type WD or WD capable of machine to machine communication (M2M), low-cost and/or low-complexity WD, a sensor equipped with WD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device, etc.

Also, in some embodiments the generic term “radio network node” is used. It may be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell/multicast Coordination Entity (MCE), IAB node, relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH). Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and/or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

Note further, that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and/or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, may be distributed among several physical devices.

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 disclosure belongs. It will be further understood that terms used herein 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 unless expressly so defined herein.

As used herein, the term reference signal path refers to a transmission/reception point (TRP), a cell, a beam, an antenna panel and/or antenna.

Some embodiments provide timing synchronization enhancement for networks.

Returning now to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 3 a schematic diagram of a communication system 10, according to an embodiment, such as a 3 GPP -type cellular network that may support standards such as LTE and/or NR (5G), which comprises an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include many more WDs 22 and network nodes 16.

Also, it is contemplated that a WD 22 may be in simultaneous communication and/or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a WD 22 may have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, WD 22 may be in communication with an eNB for LTE/E-UTRAN and a gNB for NR/NG-RAN.

The communication system 10 may itself be connected to a host computer 24, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 24 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 26, 28 between the communication system 10 and the host computer 24 may extend directly from the core network 14 to the host computer 24 or may extend via an optional intermediate network 30. The intermediate network 30 may be one of, or a combination of more than one of, a public, private or hosted network. The intermediate network 30, if any, may be a backbone network or the Internet. In some embodiments, the intermediate network 30 may comprise two or more subnetworks (not shown).

The communication system of FIG. 3 as a whole enables connectivity between one of the connected WDs 22a, 22b and the host computer 24. The connectivity may be described as an over-the-top (OTT) connection. The host computer 24 and the connected WDs 22a, 22b are configured to communicate data and/or signaling via the OTT connection, using the access network 12, the core network 14, any intermediate network 30 and possible further infrastructure (not shown) as intermediaries. The OTT connection may be transparent in the sense that at least some of the participating communication devices through which the OTT connection passes are unaware of routing of uplink and downlink communications. For example, a network node 16 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 24 to be forwarded (e.g., handed over) to a connected WD 22a. Similarly, the network node 16 need not be aware of the future routing of an outgoing uplink communication originating from the WD 22a towards the host computer 24.

A network node 16 is configured to include a TRP selection unit 32 which is configured to select at least one candidate reference signal path for use by the WD for PDC, the selecting being based at least in part on the received PDC accuracy measurements. A wireless device 22 is configured to include a PDC measurement unit 34 which is configured to determine a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates.

Example implementations, in accordance with an embodiment, of the WD 22, network node 16 and host computer 24 discussed in the preceding paragraphs will now be described with reference to FIG. 2. In a communication system 10, a host computer 24 comprises hardware (HW) 38 including a communication interface 40 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 10. The host computer 24 further comprises processing circuitry 42, which may have storage and/or processing capabilities. The processing circuitry 42 may include a processor 44 and memory 46. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 42 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 44 may be configured to access (e.g., write to and/or read from) memory 46, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).

Processing circuitry 42 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by host computer 24. Processor 44 corresponds to one or more processors 44 for performing host computer 24 functions described herein. The host computer 24 includes memory 46 that is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software 48 and/or the host application 50 may include instructions that, when executed by the processor 44 and/or processing circuitry 42, causes the processor 44 and/or processing circuitry 42 to perform the processes described herein with respect to host computer 24. The instructions may be software associated with the host computer 24.

The software 48 may be executable by the processing circuitry 42. The software 48 includes a host application 50. The host application 50 may be operable to provide a service to a remote user, such as a WD 22 connecting via an OTT connection 52 terminating at the WD 22 and the host computer 24. In providing the service to the remote user, the host application 50 may provide user data which is transmitted using the OTT connection 52. The “user data” may be data and information described herein as implementing the described functionality. In one embodiment, the host computer 24 may be configured for providing control and functionality to a service provider and may be operated by the service provider or on behalf of the service provider. The processing circuitry 42 of the host computer 24 may enable the host computer 24 to observe, monitor, control, transmit to and/or receive from the network node 16 and or the wireless device 22.

The communication system 10 further includes a network node 16 provided in a communication system 10 and including hardware 58 enabling it to communicate with the host computer 24 and with the WD 22. The hardware 58 may include a communication interface 60 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 10, as well as a radio interface 62 for setting up and maintaining at least a wireless connection 64 with a WD 22 located in a coverage area 18 served by the network node 16. The radio interface 62 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers. The communication interface 60 may be configured to facilitate a connection 66 to the host computer 24. The connection 66 may be direct or it may pass through a core network 14 of the communication system 10 and/or through one or more intermediate networks 30 outside the communication system 10.

In the embodiment shown, the hardware 58 of the network node 16 further includes processing circuitry 68. The processing circuitry 68 may include a processor 70 and a memory 72. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 68 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 70 may be configured to access (e.g., write to and/or read from) the memory 72, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read- Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read- Only Memory).

Thus, the network node 16 further has software 74 stored internally in, for example, memory 72, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 74 may be executable by the processing circuitry 68. The processing circuitry 68 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by network node 16. Processor 70 corresponds to one or more processors 70 for performing network node 16 functions described herein. The memory 72 is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software 74 may include instructions that, when executed by the processor 70 and/or processing circuitry 68, causes the processor 70 and/or processing circuitry 68 to perform the processes described herein with respect to network node 16. For example, processing circuitry 68 of the network node 16 may include a TRP selection unit 32 which is configured to select at least one candidate reference signal path for use by the WD for PDC, the selecting being based at least in part on the received PDC accuracy measurements.

The communication system 10 further includes the WD 22 already referred to. The WD 22 may have hardware 80 that may include a radio interface 82 configured to set up and maintain a wireless connection 64 with a network node 16 serving a coverage area 18 in which the WD 22 is currently located. The radio interface 82 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers.

The hardware 80 of the WD 22 further includes processing circuitry 84. The processing circuitry 84 may include a processor 86 and memory 88. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 84 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 86 may be configured to access (e.g., write to and/or read from) memory 88, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).

Thus, the WD 22 may further comprise software 90, which is stored in, for example, memory 88 at the WD 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the WD 22. The software 90 may be executable by the processing circuitry 84. The software 90 may include a client application 92. The client application 92 may be operable to provide a service to a human or non-human user via the WD 22, with the support of the host computer 24. In the host computer 24, an executing host application 50 may communicate with the executing client application 92 via the OTT connection 52 terminating at the WD 22 and the host computer 24. In providing the service to the user, the client application 92 may receive request data from the host application 50 and provide user data in response to the request data. The OTT connection 52 may transfer both the request data and the user data. The client application 92 may interact with the user to generate the user data that it provides.

The processing circuitry 84 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by WD 22. The processor 86 corresponds to one or more processors 86 for performing WD 22 functions described herein. The WD 22 includes memory 88 that is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software 90 and/or the client application 92 may include instructions that, when executed by the processor 86 and/or processing circuitry 84, causes the processor 86 and/or processing circuitry 84 to perform the processes described herein with respect to WD 22. For example, the processing circuitry 84 of the wireless device 22 may include a PDC measurement unit 34 which is configured to determine a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates. In some embodiments, the inner workings of the network node 16, WD 22, and host computer 24 may be as shown in FIG. 4 and independently, the surrounding network topology may be that of FIG. 3.

In FIG. 4, the OTT connection 52 has been drawn abstractly to illustrate the communication between the host computer 24 and the wireless device 22 via the network node 16, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the WD 22 or from the service provider operating the host computer 24, or both. While the OTT connection 52 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

The wireless connection 64 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the WD 22 using the OTT connection 52, in which the wireless connection 64 may form the last segment. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and/or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc.

In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 52 between the host computer 24 and WD 22, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 52 may be implemented in the software 48 of the host computer 24 or in the software 90 of the WD 22, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 52 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 48, 90 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 52 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the network node 16, and it may be unknown or imperceptible to the network node 16. Some such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary WD signaling facilitating the host computer’s 24 measurements of throughput, propagation times, latency and the like. In some embodiments, the measurements may be implemented in that the software 48, 90 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 52 while it monitors propagation times, errors, etc.

Thus, in some embodiments, the host computer 24 includes processing circuitry 42 configured to provide user data and a communication interface 40 that is configured to forward the user data to a cellular network for transmission to the WD 22. In some embodiments, the cellular network also includes the network node 16 with a radio interface 62. In some embodiments, the network node 16 is configured to, and/or the network node’s 16 processing circuitry 68 is configured to perform the functions and/or methods described herein for preparing/initiating/maintaining/supporting/ending a transmission to the WD 22, and/or preparing/terminating/maintaining/supporting/ending in receipt of a transmission from the WD 22.

In some embodiments, the host computer 24 includes processing circuitry 42 and a communication interface 40 that is configured to a communication interface 40 configured to receive user data originating from a transmission from a WD 22 to a network node 16. In some embodiments, the WD 22 is configured to, and/or comprises a radio interface 82 and/or processing circuitry 84 configured to perform the functions and/or methods described herein for preparing/initiating/maintaining/supporting/ending a transmission to the network node 16, and/or preparing/terminating/maintaining/supporting/ending in receipt of a transmission from the network node 16.

Although FIGS. 3 and 4 show various “units” such as TRP selection unit 32, and PDC measurement unit 34 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

FIG. 5 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIGS. 3 and 4, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIG. 4. In a first step of the method, the host computer 24 provides user data (Block SI 00). In an optional substep of the first step, the host computer 24 provides the user data by executing a host application, such as, for example, the host application 50 (Block SI 02). In a second step, the host computer 24 initiates a transmission carrying the user data to the WD 22 (Block SI 04). In an optional third step, the network node 16 transmits to the WD 22 the user data which was carried in the transmission that the host computer 24 initiated, in accordance with the teachings of the embodiments described throughout this disclosure (Block SI 06). In an optional fourth step, the WD 22 executes a client application, such as, for example, the client application 92, associated with the host application 50 executed by the host computer 24 (Block SI 08).

FIG. 6 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIG. 3, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIGS. 3 and 4. In a first step of the method, the host computer 24 provides user data (Block SI 10). In an optional substep (not shown) the host computer 24 provides the user data by executing a host application, such as, for example, the host application 50. In a second step, the host computer 24 initiates a transmission carrying the user data to the WD 22 (Block SI 12). The transmission may pass via the network node 16, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step, the WD 22 receives the user data carried in the transmission (Block SI 14).

FIG. 7 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIG. 3, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIGS. 3 and 4. In an optional first step of the method, the WD 22 receives input data provided by the host computer 24 (Block SI 16). In an optional substep of the first step, the WD 22 executes the client application 92, which provides the user data in reaction to the received input data provided by the host computer 24 (Block SI 18). Additionally or alternatively, in an optional second step, the WD 22 provides user data (Block S120). In an optional substep of the second step, the WD provides the user data by executing a client application, such as, for example, client application 92 (Block S122). In providing the user data, the executed client application 92 may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the WD 22 may initiate, in an optional third substep, transmission of the user data to the host computer 24 (Block S124). In a fourth step of the method, the host computer 24 receives the user data transmitted from the WD 22, in accordance with the teachings of the embodiments described throughout this disclosure (Block S126).

FIG. 8 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIG. 3, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIGS. 3 and 4. In an optional first step of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 16 receives user data from the WD 22 (Block S128). In an optional second step, the network node 16 initiates transmission of the received user data to the host computer 24 (Block S130). In a third step, the host computer 24 receives the user data carried in the transmission initiated by the network node 16 (Block SI 32).

FIG. 9 is a flowchart of an example process in a network node 16 for timing synchronization enhancement for networks. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 68 (including the TRP selection unit 32), processor 70, radio interface 62 and/or communication interface 60. Network node 16 such as via processing circuitry 68 and/or processor 70 and/or radio interface 62 and/or communication interface 60 is configured to receive a propagation delay compensation, PDC, accuracy measurement for each of at least one transmission and reception point, reference signal path, based at least in part on a number of propagation delay estimates performed by the WD 22 (Block SI 34). The method includes selecting at least one candidate reference signal path for use by the WD 22 for PDC, the selecting being based at least in part on the received PDC accuracy measurements (Block S136). The method also includes transmitting to the WD 22 an indication of the selected at least one candidate reference signal path for use by the WD 22 for PDC (Block S138). According to this aspect, in some embodiments, the reference signal path is one of a transmission and reception point, TRP, a cell, a beam and an antenna. In some embodiments, selecting the at least one candidate reference signal path for use by the WD 22 for PDC is further based at least in part on a signal to interference plus noise ratio, SINR, upon which the received PDC accuracy measurements are based. In some embodiments, selecting the at least one candidate reference signal path for use by the WD 22 for PDC includes determining a PDC measurement accuracy based at least in part on the received PDC accuracy measurements. In some embodiments, selecting the at least one candidate reference signal path for use by the WD 22 for PDC is further based at least in part on a topology of a network comprising the network node 16. In some embodiments, selecting the at least one candidate reference signal path for use by the WD 22 for PDC further includes determining a list of candidate reference signal paths ranked according to at least one criteria. In some embodiments, the method includes triggering a cell change when a current reference signal path being used by the WD 22 for PDC results in a less accurate PDC estimate than another candidate in the list of candidate reference signal paths. In some embodiments, selecting the at least one candidate reference signal path for use by the WD 22 for PDC includes determining an integral metric for each candidate reference signal path of the at least one candidate reference signal path, the integral metric being based at least in part on a weighting of selection criteria. In some embodiments, the method includes pre-configuring the WD 22 with a list of candidate reference signal paths and at least one condition for selection of a candidate reference signal path from the list for use by the WD 22 for PDC. In some embodiments, the at least one condition includes a downlink reference signal being greater than a first threshold. In some embodiments, the method includes, in an event of a handover of the WD 22 to another cell, configuring the WD 22 to determine a PDC accuracy measurement for each of the at least one candidate reference signal path after the handover. In some embodiments, the method includes determining a stability of synchronization accuracy based at least in part on the received PDC accuracy measurements, and triggering a cell change when the stability of synchronization accuracy falls below a second threshold.

FIG. 10 is a flowchart of an example process in a wireless device 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of wireless device 22 such as by one or more of processing circuitry 84 (including the PDC measurement unit 34), processor 86, radio interface 82 and/or communication interface 60. Wireless device 22 such as via processing circuitry 84 and/or processor 86 and/or radio interface 82 is configured to determine a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates (Block S140). The process also includes transmitting the determined PDC accuracy measurements to the network node 16 (Block SI 42)

According to this aspect, in some embodiments, the reference signal path is one of a transmission and reception point, TRP, a cell, a beam and an antenna. In some embodiments, the method includes receiving from the network node 16 an indication of a reference signal path to be used for PDC. In some embodiments, the method includes selecting a reference signal path for PDC from a preconfigured list of reference signal paths based at least in part on a measurement condition specified by the network node 16. In some embodiments, the measurement condition is a reference signal measurement exceeding a first threshold. In some embodiments, the method includes deactivating a previously activated reference signal path for PDC. In some embodiments, the method includes transmitting a first indication of a signal to interference plus noise ratio, SINR, upon which the PDC accuracy measurements are based. In some embodiments, the method includes receiving from the network node 16 a second indication of a serving cell to use for PDC accuracy measurements. In some embodiments, the method includes, in an event of a handover of the WD 22 to another cell, determining a PDC accuracy measurement for each of the at least one candidate reference signal path after the handover.

Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for timing synchronization enhancement for networks. In some embodiments, the network may be a wide area network, but implementation are not limited solely to wide area networks.

Methods are disclosed for selecting the best antenna, TRP, beam or cell (reference signal path) to be used for propagation delay compensation for accurate time synchronization between WD 22 and the network. Applications of the disclosed method include a factory deployment where multiple TRPs or cells are available for the WD 22 to connect to, but have different propagation delays and/or the stability and accuracy of the estimation of the propagation delays may have a sudden delay estimation change. Propagation delays may include or be caused by blockers or temporary blockers, change of non-line of sight connection. Also, a poor radio connection may impact the accuracy of the rx-tx time difference measurements. For example, some reference signal paths may have a line of sight connection, which may be preferable from a propagation delay estimation point of view. Some embodiments identify the most suitable reference signal path in the network, with which an accurate propagation delay estimate may be achieved.

Both variants of the propagation delay compensation (PDC) described above are considered.

Measurements for propagation delay compensation accuracy

In some embodiments, for the WD-based RTT PDC, the WD 22 saves the last X calculated propagation delay estimates and calculates a value representing an accuracy and/or other metrics which may impact accuracy, such as stability or variability of PDC estimates, e.g., the variance or standard deviation. This calculation is done specifically for one antenna (TRP) or cell. How many measurements (X) may be taken may be configured for the WD 22 by the network node 16.

In some embodiments, it may be assumed that the WD 22 is aware of its own movement and use this information to adjust a number of past propagation delay estimates taken into account to calculate stability criteria. In other words, number of measurements X (window size) may vary depending on WD 22 movement. For example, if the WD 22 is stationary for a given time period T, the WD 22 may use the standard deviation of the measurement within the period T to estimate the propagation delay compensation accuracy. In another example, if the WD 22 is moving, then the WD 22 may choose a longer time period to first estimate the trajectory of the movement, and then later evaluate the standard deviation of the measurements along the trajectory. In some embodiments, for the network node-based RTT PDC, the network node 16 performs the calculation of the propagation delay accuracy estimate, based at least in part on the information received from the WD 22, e.g., the WD 22 rx-tx time difference. The WD 22 may calculate a value representing an accuracy and/or other metrics about the WD 22 Rx-Tx time difference measurement.

In addition, the network node 16 or the WD 22 may use other channel quality metrics which may help to estimate PDC accuracy, e.g., measurements based on different reference signals (primary synchronization signal (PSS), secondary synchronization signal (SSS), demodulation reference signal (DMRS), channel state information reference signal (CSI-RS), CSI interference measurement (CSI-IM), TRS, PRS, SRS, etc.) derived from CSI reports from the WD 22 or from measurements performed by the network node 16. For example, a WD 22 may report channel quality indicator (CQI) values that fluctuate, which may indirectly indicate that the link is unstable. Or, the WD 22 may perform UL data transmission with DMRSs and the network node 16 that receives the DMRS may estimate doppler shift or delay spread to be used to adjust the PDC accuracy estimate.

In some embodiments, of the above-described configurations of two WD- based or network node-based RTT PDC, the WD 22 is configured with more than one PRS/TRS, while each PRS/TRS is associated with one reference signal path for PDC. Only one PRS/TRS is activated for PDC. For other PRS/TRS, the WD 22 measures the signal quality. The signal quality measurements may include at least one of received signal strength indicator (RS SI), reference signal received power (RSRP), reference signal received quality (RSRQ), signal to noise ratio (SNR), signal to interference plus noise ratio (SINR), fading characteristics such as delay spread or doppler shift frequency, detection of line of sight (LOS)/non-line of sight (NLOS).

In some embodiments, to measure PDC accuracy, the WD 22 derives the boundary of the system frame exclusively from the reference signal path for which the WD 22 is configured/activated to receive DL PRS/TRS or transmit UL SRS. This boundary of the system frame might be different from the boundary of the system frame that the WD 22 uses for data transmission (the WD 22 may use multiple reference signal paths or the TRP with synchronization signal block (SSB) received). In this embodiment, the WD 22 may measure the PDC accuracy when using WD- based RTT PDC. Measurement reporting to network

When the WD 22 performs PDC accuracy measurements, the WD 22 reports the calculated propagation delay accuracy measurements to the network node 16. The reporting may be triggered periodically, on explicit request by the network node 16 or based on configured measurement triggers, such as if the accuracy falls below a certain threshold where the threshold is explicitly configured.

In the case of event-triggered measurement reporting, if the accuracy falls below a certain threshold, the WD 22 may also report the candidate reference signal paths or cells for reference time delivery. In one example, the WD 22 reports the RSRP/RSRQ/SINR of all the PRS/TRS that the network has previously configured (but not activated) for PDC. In another example, the WD 22 reports the RSRP/RSRQ/SINR of the PRS/TRS that the network has previously configured (but not activated) for PDC provided that the RSRP/RSRQ/SINR value is larger than a configurable threshold.

The WD 22 measurement may be reported on a RRC message or in uplink control information (UCI) which may be further transmitted on a physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH). In some embodiments, an explicit request by the network node 16 may be contained in an RRC message, MAC CE or downlink control information (DCI) command.

Principles disclosed herein may be extended to when the WD 22 does not perform PDC accuracy measurements, but provides the WD Rx-Tx time difference for network node-based PDC.

In addition to reporting measurements, the WD 22 may inform the network node 16 that time synchronization accuracy is below expectations agreed between the WD 22 and the network node 16 via of a time stability status report, which may be used for triggering a cell/TRP re-selection.

Network selection of best antenna/TRP or cell and reconfiguration of the WD

For selecting the best antenna (TRP) or cell for the WD 22, the network node 16 may consider one or more of the following criteria:

• The propagation delay accuracy estimate (e.g., variance or stability) calculated and sent to network node 16 by the WD 22, or the calculated value by the network node itself;

• Bandwidth and/or SINR on the reference signals the calculation was based on; • Network topology known to the network node 16, e.g. delay/jitter between network node/base-band unit and antenna point/remote radio unit. Also asynchronicity between DL and UL delay/jitter may be taken into account;

• network node hardware;

• UE hardware and capabilities;

• the CQI/SINR/RSRP/RSRQ of the reference signals, and/or stability of CQI/SINR/RSRP/RSRQ in time;

• fading conditions, e.g., lowest doppler shift or lowest delay spread;

• delay/jitter between network node baseband unit and antenna point/remote radio unit;

• a bandwidth that the network node 16 may allocate for the PDC;

• sub-carrier spacing (SCS), because PDC error is less for higher subcarrier spacing (SCS); and/or

• penalty due to past events, e.g., a candidate may be temporarily de-prioritized if the WD 22 was served by a TRP/cell and re-selection happened in the past 10 seconds. Or the candidate may be temporarily de-prioritized if an accuracy estimate just recently became the best, but the network node 16 may take 10 seconds to make sure the metric is not changing. Thus, in some embodiments, a candidate must have the best metrics of among a set of candidates for a minimum time.

The network node 16 may build a list of candidates, (TRPs and/or cells including current serving TRP/cell) and rank them according to one or a combination of the criteria above. For the case when a combination of criteria is used, TRPs/cells may be ranked according to the most important criteria first, and if more than one TRPs/cells are the same according to a first criteria, the second criteria may be used, etc. Alternatively, weighting coefficients may be used to calculate an integral metric of each TRP/cell and the candidates may be sorted according to the integral metrics.

Once reference signal path or cell change is triggered, the network node 16 may select the best candidate based on the ranking list, e.g., reference signal path with the best accuracy estimate or cell with the most bandwidth for PDC.

The network node 16 may sequentially configure various reference signal paths for the WD 22 in order for the WD 22 to perform the measurements and for the network node 16 to establish a basis for selecting the most suitable reference signal path: • The network node 16 may pre-configure various reference signal paths (with associated PRS/TRS and SRS) for WD 22 in an RRC message. After receiving a measurement report on UCI, the network node 16 may activate the reference signal path for transmission by a DCI or an MAC CE message;

• After receiving this message, the WD 22 may consider the previous reference signal path to be no longer activated for PDC while the new reference signal path is activated for PDC; and/or

• In another example, the network node 16 pre-configures a list of reference signal paths with a list of associated conditions for activation. In all those reference signal paths, the network node 16 transmits the DL reference signals while the UL reference signal transmissions are determined by the WD 22. If a condition is satisfied (e.g., the signal quality is larger than a threshold), then the WD 22 may activate that reference signal path, by for example, transmitting SRS on that reference signal path.

In cases of carrier aggregation, the network node 16 may configure the WD 22 to use another serving cell to acquire the timing (e.g., derive the system frame number). The indication may be in an RRC message along with the updated timing information from the serving cell. In the case of dual connectivity, the network node 16 may configure the WD 22 to use the secondary cell group (SCG) instead of the default master cell group (MCG).

In the following discussion, assume that there is a single cell and so the timing is from the primary cell (Pcell). For this scenario, where a handover is required for the WD 22 to connect to another antenna or another cell, the network node 16 may trigger handovers sequentially for the WD 22 to connect to the other cell, in order for the WD 22 to carry out the measurements, and report to the network node 16 in order for the network node 16 to establish a basis for selecting the most suitable cell eventually.

If the network node 16 receives a time stability status report which indicates that time synchronization accuracy is below expectations, the network node 16 may trigger the TRP/cell change. Triggering may happen when:

• The network node 16 periodically checks whether current TRP/cell is the best in the list of candidates. Once it is no longer the best, the network node 16 triggers TRP change or handover; • The network node 16 periodically checks how the current TRP/cell compared to other candidates in the list. If the difference in metrics/criteria is outside a configured margin or threshold, the network node 16 triggers TRP change or handover;

• If one or more metric/criteria passes a configured threshold for the current TRP/cell, e.g., accuracy is below a defined level or variance or the tx-rx time difference is above threshold; and/or

• If the time stability status report from the core network or from the WD 22 indicates that time synchronization stability is below expectations.

As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and/or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and/or functionality described herein may be performed by, and/or associated to, a corresponding module, which may be implemented in software and/or firmware and/or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD- ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

Some embodiments are described herein with reference to flowchart illustrations and/or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer readable memory or storage medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

It is to be understood that the functions/acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments may be combined in any way and/or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

1. A method in a wireless device, WD (22), configured to communicate with a network node (16), the method comprising: determining (SI 40) a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates; and transmitting (S142) the determined PDC accuracy measurements to the network node (16).

2. The method of Claim 1, wherein the reference signal path is one of a transmission and reception point, TRP, a cell, a beam and an antenna.

3. The method of Claims 1 or 2, further comprising: receiving from the network node (16) an indication of a reference signal path to be used for PDC.

4. The method of Claims 1 or 2, further comprising: selecting a reference signal path for PDC from a preconfigured list of reference signal paths based at least in part on a measurement condition specified by the network node (16).

5. The method of any of Claims 1-4, further comprising: deactivating a previously activated reference signal path for PDC.

6. The method of any of Claims 1-5, further comprising: in an event of a handover of the WD (22) to another cell, determining a PDC accuracy measurement for each of the at least one candidate reference signal path after the handover.

7. A wireless device, WD (22), configured to communicate with a network node (16), the WD (22) comprising: processing circuitry (84) configured to determine a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path based at least in part on a number of propagation delay estimates; and a radio interface (82) in communication with the processing circuitry (84) and configured to transmit the determined PDC accuracy measurements to the network node (16).

8. The WD (22) of Claim 7, wherein the processing circuitry (84) and the radio interface (82) are further configured to perform the method according to any of Claims 2 to 9.

9. A method in a network node (16) configured to communicate with a wireless device, WD (22), the method comprising: receiving (SI 34) a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path, based at least in part on a number of propagation delay estimates performed by the WD (22); selecting (SI 36) at least one candidate reference signal path for use by the WD (22) for PDC, the selecting being based at least in part on the received PDC accuracy measurements; and transmitting (SI 38) to the WD (22) an indication of the selected at least one candidate reference signal path for use by the WD (22) for PDC.

10. The method of Claim 9, wherein selecting the at least one candidate reference signal path for use by the WD (22) for PDC is further based at least in part on: at least one of a bandwidth and a signal to interference plus noise ratio, SINR, upon which the received PDC accuracy measurements are based; and/or a topology of a network comprising the network node (16).

11. The method of Claims 9 or 10, wherein selecting the at least one candidate reference signal path for use by the WD (22) for PDC further includes: determining a PDC measurement accuracy based at least in part on the received PDC accuracy measurements, and/or determining a list of candidate reference signal paths ranked according to at least one criteria.

12. The method of Claim 11, further comprising triggering a cell change when a current reference signal path being used by the WD (22) for PDC results in a less accurate PDC estimate than another candidate in the list of candidate reference signal paths.

13. The method of any of Claims 9-12, wherein selecting the at least one candidate reference signal path for use by the WD (22) for PDC includes determining an integral metric for each candidate reference signal path of the at least one candidate reference signal path, the integral metric being based at least in part on a weighting of selection criteria; and the method further comprising: pre-configuring the WD (22) with a list of candidate reference signal paths and at least one condition for selection of a candidate reference signal path from the list for use by the WD (22) for PDC.

14. The method of any of Claims 9-13, further comprising: determining a stability of synchronization accuracy based at least in part on the received PDC accuracy measurements; and triggering a cell change when the stability of synchronization accuracy falls below a second threshold.

15. A network node (16) configured to communicate with a wireless device, WD (22), the network node (16) comprising: a radio interface (62) configured to receive a propagation delay compensation, PDC, accuracy measurement for each of at least one reference signal path, based at least in part on a number of propagation delay estimates performed by the WD (22); processing circuitry (68) in communication with the radio interface (62) and configured to select at least one candidate reference signal path for use by the WD (22) for PDC, the selecting being based at least in part on the received PDC accuracy measurements; and the radio interface (62) further configured to transmit to the WD (22) an indication of the selected at least one candidate reference signal path for use by the WD (22) for PDC.

16. The network node (16) of Claim 15, wherein the radio interface (62) and the processing circuitry (68) are further configured to perform the method according to any of Claims 9 to 14.