Synchronized reference path selection for BI / multi-static radar operation in cellular networks

Abstract

A method, network node and wireless device (WD) for synchronous reference path selection for bistatic and multistatic radar operations in a cellular network are disclosed. According to one aspect, a method in a WD or radio base station comprises selecting, via a first reconfigurable repeater, a first synchronization reference path for synchronization between a first network node and a second network node, the first synchronization reference path being resolvable from a second synchronization path comprising a second reconfigurable repeater, the first synchronization reference path is selected to be parsable from the object. The method further comprises using the second synchronization reference path for synchronization between the first network node and the second network node via the second reconfigurable reference path in the event of interference or congestion in the first synchronization reference path.

Description

Technical Field

[0001] The present disclosure relates to wireless communication and, more particularly, to the selection of a synchronization reference path for bistatic radar operation and multistatic radar operation in a cellular network. Background Art

[0002] The Third Generation Partnership Project (3GPP) has developed and is developing standards for fourth-generation (4G) (also known as Long-Term Evolution (LTE)) wireless communication systems and fifth-generation (5G) (also known as New Radio (NR)) wireless communication systems. Among other features, such systems provide broadband communication between network nodes such as base stations and mobile wireless devices (WDs), as well as communication between network nodes and between WDs. 3GPP is also developing standards for sixth-generation (6G) wireless communication networks.

[0003] Joint communication and sensing (JCAS) is an emerging research area that has been standardized in the Institute of Electrical and Electronics Engineers (IEEE) standard IEEE802.11, which has been discussed in 3GPP, and is expected to be an essential component element in 6G. Sensing in a JCAS system can be done in radar or using channel state information (CSI). In radar, one or more pulses are sent for the purpose of range and Doppler measurements. Even though the use of radar in a line-of-sight (LoS) propagation environment is very effective, its deployment in an environment with strong non-line-of-sight (NLOS) characteristics has become challenging. In contrast, CSI-based sensing has the potential to overcome some of these limitations by measuring the CSI of the underlying channel between the transmitter and the receiver. In this scheme, inference about the presence of an object (which is not necessarily a device) and / or any other quantity of interest is done by changing the CSI at different time instances or by appropriate processing of the CSI of one instance. In the literature, this form of sensing is referred to as device-free sensing (DFS). Here, the word "free" is related to the fact that the object is not necessarily a device and it only exists in the physical space of interest.

[0004] Conceptually, the simplest form of sensing is monostatic sensing. Monostatic sensing is identified as the case where both the TX and the RX are placed at the same physical location and operate in full-duplex (FD) mode. Due to the technical challenges and complexity of FD nodes in monostatic sensing, bistatic sensing has been considered as an alternative option. In bistatic sensing, the TX and the RX are geographically separated when operating in the same radio time domain resource. Another extension is multistatic sensing, where multiple geographically separated transmitters are sending signals that are sensed by multiple geographically separated receivers.

[0005] The focus of the present disclosure is on bistatic sensing and its extension to multistatic sensing. The operating principle of bistatic sensing is in Figure 1is shown in. As Figure 1 shown in the example of, there are a transmitting node (TX) and a receiving node (RX). The TX transmits a sensing signal, which is collected from the receiver after they propagate in the existing environment. Assuming that there is only one object and assuming that the TX and RX are synchronized in time, the RX can measure the time of flight (ToF) at the output of the matched filter. From the ToF (T object ), the bistatic distance (D tot-object ) is obtained. The bistatic distance is the distance between the TX and the object (D TX-object ) plus the distance between the object and the RX (D object-RX ). In the literature, it is well known that without knowing the angle of departure (AoD) in the TX and the angle of arrival (AoA) in the RX, it can be concluded from the bistatic distance that the object is placed somewhere on the surface of an ellipsoid with foci in the TX and RX. In contrast, if the AoD and / or AoA are available, more precise or accurate knowledge of the object's position on the ellipse can be extracted. In both cases, it is assumed that the distance between the TX and RX is known.

[0006] The effective operation of bistatic sensing depends on the time synchronization between the TX and RX. Compared with monostatic radar that shares a common clock source and common time close to the radio unit and its antenna reference points for the transmitter and receiver, achieving accurate synchronization between physically separated TX and RX nodes is a key challenge.

[0007] Time synchronization will be required to accurately determine T object and for determining D tot-object , that is, the receiver will need to accurately correlate the reflected reception time (T rx_object ) with the transmission time (T tx ) at the TX node. A time error of only 3 ns between the transmitter and the receiver will roughly correspond to a 1 m distance inaccuracy.

[0008] Radio frequency (RF) carrier phase synchronization is required to detect object mobility and estimate its speed by detecting changes in the RF carrier phase in the reflection path. A relative RF frequency error of 3 ppb between the TX and RX nodes at 3.5 GHz will correspond to a frequency difference of approximately 10 Hz, which will then be similar to the Doppler shift of a pedestrian and will thus limit the lowest possible speed that can be safely detected. It is worth noting that the base station frequency accuracy required by 3GPP for communication is ±50 ppb, that is, a relative difference of 100 ppb between the TX and RX nodes.

[0009] There are different components for synchronizing physically separated base stations. For example, there are separate local Global Navigation Satellite System (GNSS) synchronization receivers, and a common timing source such as a GNSS synchronization receiver with Precision Time Protocol (PTP) and / or SyncE to distribute time and frequency to nodes. The distribution path typically involves multiple nodes and components, and each node and component contributes to the total error up to the antenna reference point. Therefore, achieving very strict inter-node synchronization is challenging and complex considering the required wired infrastructure that needs to be installed. Improved frequency accuracy and stability of local oscillators beyond what is required for communication incur additional costs. A Global Navigation Satellite System (GNSS) synchronization receiver would require an installation that allows for a free view of the sky, which is not always possible or requires expensive installations. Additionally, blocking of GNSS receivers is a recognized problem.

[0010] Using various forms of air synchronization and especially direct synchronization between TX and RX is likely the most promising approach for achieving accurate and cost-effective synchronization for bistatic and multistatic radars. For direct synchronization, the sensing signal sent from the TX node is used for object sensing and synchronization at the receiver. The synchronization path can be a Line-of-Sight (LOS) path or a controlled (well-characterized) Non-Line-of-Sight (NLOS) path. This scheme will also benefit from eliminating errors or variations common to the reflection path and the synchronization path in the TX / RX nodes, such as errors / variations within the radio TX and RX chains, like delays or phase changes.

[0011] As Figure 2 shown in the example, in the case of a strong LoS synchronization reference path between TX and RX in a bistatic radar deployment or a multistatic radar deployment, the receiver is exposed to signals that have propagated through the LoS and through reflections created by objects in the environment. Clearly, since the bandwidth and thus the resolution in the receiver will be limited, objects with reflections arriving (T rx_object ) or temporally close to the strong LOS reference path (T rx_ref ) may be difficult to distinguish from the direct path. Avoiding this will be difficult in a bistatic radar setup because objects close to the LOS path still need to be illuminated to be detected by reflection. A multistatic radar scheme with multiple TX-RX pairs can be complementary to each other, i.e., one set of TX-RX pairs can cover objects that appear in the LOS directions between other TX-RX pairs.

[0012] In some scenarios, as Figure 3The use of a well-characterized and stable NLOS synchronization reference path as shown will be an alternative to the LOS synchronization path. For example, in some deployments, there may not even be an available LOS path between the TX node and the RX node. Another advantage is that the receiver does not experience a large signal dynamic between a strong LOS path and weaker reflections. The NLOS reference path will have the same problem as the LOS synchronization path, that is, it may be difficult to separate reflections from objects close to the NLOS synchronization path, so these reflections arrive simultaneously or are close in time to the NLOS reference path. The beamforming capability in the receiving node can separate reflections that arrive simultaneously in the spatial domain (similar to object B in Figure 3 ), but the beamforming resolution is also limited. Therefore, objects (object A) at or near the NLOS reflection point may not be distinguishable.

[0013] Another problem is the availability and criticality of the synchronization reference path. The bi- or multi-static sensing function can be used for critical infrastructure such as monitoring traffic cross-sections. The synchronization reference path may be blocked or interfered with (either unintentionally or deliberately blocked), so a robust solution is needed. Similar to the above problem, that is, in order to detect and distinguish objects at the NLOS reflection point close to the synchronization reference path, the reflections from such objects may also affect the receiver's ability to distinguish and accurately resolve the synchronization reference. This results in uncertainty in the reception time, thus reducing radar sensing. SUMMARY OF THE INVENTION

[0014] Some embodiments advantageously provide methods, network nodes, and WDs for selecting a synchronization reference path for bi-static and multi-static radar operations in a cellular network.

[0015] Some embodiments employ reconfigurable repeaters, such as reconfigurable intelligent surfaces (RISs) for the synchronization path.

[0016] Some embodiments solve the problem of objects close by by configuring the RIS to detect or track objects close to the RIS and by changing the characteristics of the synchronization reference by at least one or more of the following: · Changing or disabling the reflection synchronization reference path to the bi-static receiver and enabling an alternative synchronization path, for example, by using another RIS or redirecting the path through another reflector in the environment; and · Changing the delay for the synchronization path through the RIS by a known and accurate amount.

[0017] Some embodiments use a reconfigurable intelligent surface (RIS) to increase the robustness and / or performance of the synchronization path by selecting an alternative second RIS or changing the path through the first RIS, where the receiver monitors the quality of the synchronization path and can be based on the condition of selecting the best available path.

[0018] In some embodiments, an object reflection sensing path is detected in a bistatic / multistatic radar scenario having resolution degradation or air-synchronized reference path synchronization degradation. The degradation is due to the channel similarity and proximity of arrival times of the sensing and synchronization paths related to the receiver resolution limitations.

[0019] In some embodiments, a reconfigurable intelligent surface (RIS) is provided to mitigate the limitations by configuring and using alternative synchronization paths that depend on the relative positions of the object and the RIS.

[0020] In addition, the RIS can be used to increase the robustness and performance of the synchronization path. The receiver can periodically monitor the quality of different reference path alternatives created by the RIS and select the most suitable alternative. The monitoring can include checking the relative arrival times between different paths to detect interference spoofing that attempts to manipulate the arrival time of one of the synchronization paths.

[0021] According to one aspect, a first network node is provided that is configured to communicate with a second network node. The first network node is configured to: use a first synchronization reference path via a first reconfigurable repeater for synchronization between the network node and the WD, the first synchronization reference path being resolvable from a second synchronization path including a second reconfigurable repeater, the first synchronization reference path being selected to be resolvable from an object. The first network node is further configured to, in the event of interference or blockage in the first synchronization reference path, use a second synchronization reference path via a second reconfigurable reference path for synchronization between the first network node and the second network node.

[0022] According to this aspect, in some embodiments, the first network node is configured to track an object using a first synchronization reference path. In some embodiments, the handover between the first synchronization reference path and the second synchronization reference path occurs according to a pattern that is at least partially based on the latency allowed for detecting the object during a radar scan. In some embodiments, one of the first synchronization reference path and the second synchronization reference path is selected at least partially based on at least one of time of arrival (ToA) and time of flight (ToF). In some embodiments, the decision to handover between the first synchronization reference path and the second synchronization reference path is at least partially based on a prediction of the future position of the object. In some embodiments, the first network node is configured to monitor a plurality of synchronization reference paths and select a reference path at least partially based on the resolvability of the object for each synchronization reference path. In some embodiments, the first network node is further configured to monitor the time of arrival for each of the first synchronization reference path and the second synchronization reference path to prevent interference spoofing. In some embodiments, at least one of the first synchronization reference path and the second synchronization reference path includes a passive reflector. In some embodiments, using the second synchronization reference path includes changing the reference path angle or latency for the second synchronization reference path. In some embodiments, the first network node is one of a WD and a radio base station, and the second network node is one of a WD and a radio base station.

[0023] According to another aspect, a method implemented in a first network node configured to communicate with a wireless device WD is provided. The method includes: selecting, via a first reconfigurable repeater, a first synchronization reference path for synchronization between the first network node and a second network node, the first synchronization reference path being resolvable from a second synchronization path including a second reconfigurable repeater, the first synchronization reference path being selected to be resolvable from an object. The method includes: in the case of interference or blockage in the first synchronization reference path, using, via a second reconfigurable reference path, the second synchronization reference path for synchronization between the first network node and the second network node.

[0024] According to this aspect, in some embodiments, the method includes tracking an object using a first synchronization reference path. In some embodiments, the switch between the first synchronization reference path and the second synchronization reference path occurs according to a pattern that is at least partially based on the allowable latency for detecting the object during a radar scan. In some embodiments, one of the first synchronization reference path and the second synchronization reference path is selected at least partially based on at least one of time of arrival (ToA) and time of flight (ToF). In some embodiments, the decision to switch between the first synchronization reference path and the second synchronization reference path is at least partially based on a prediction of the future position of the object. In some embodiments, the method includes monitoring a plurality of synchronization reference paths and selecting a reference path at least partially based on the resolvability of the object for each synchronization reference path. In some embodiments, the method includes monitoring the time of arrival for each of the first synchronization reference path and the second synchronization reference path to prevent interference spoofing. In some embodiments, at least one of the first synchronization reference path and the second synchronization reference path includes a passive reflector. In some embodiments, using the second synchronization reference path includes changing the reference path angle or latency for the second synchronization reference path. In some embodiments, the first network node is one of a WD and a radio base station, and the second network node is one of a WD and a radio base station. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] A more complete understanding of the present embodiments and their attendant advantages and features will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0026] Figure 1 An example of bistatic sensing is shown;

[0027] Figure 2 A short-range obstacle and a line-of-sight reference path are shown;

[0028] Figure 3 An alternative path with a reflector is shown;

[0029] Figure 4 is a schematic diagram showing an example network architecture of a communication system connected to a host computer via an intermediate network according to the principles in the present disclosure;

[0030] Figure 5 is a block diagram of a host computer communicating with a wireless device via a network node through at least a partially wireless connection according to some embodiments of the present disclosure;

[0031] Figure 6 is a flowchart showing an example method for executing a client application at a wireless device implemented in a communication system including a host computer, a network node, and a wireless device according to some embodiments of the present disclosure;

[0032] Figure 7 is a flowchart showing an example method for receiving user data at a wireless device implemented in a communication system including a host computer, a network node, and a wireless device according to some embodiments of the present disclosure;

[0033] Figure 8 is a flowchart showing an example method for receiving user data at a host computer from a wireless device implemented in a communication system including a host computer, a network node, and a wireless device according to some embodiments of the present disclosure;

[0034] Figure 9 is a flowchart showing an example method for receiving user data at a host computer implemented in a communication system including a host computer, a network node, and a wireless device according to some embodiments of the present disclosure;

[0035] Figure 10 is a flowchart of an example process for synchronous reference path selection for bistatic radar operation and multistatic radar operation in a cellular network in a network node or a wireless device (WD);

[0036] Figure 11 is a flowchart of another example process for synchronous reference path selection for bistatic radar operation and multistatic radar operation in a cellular network in a network node or a wireless device (WD);

[0037] Figure 12 shows bistatic sensing via a RIS;

[0038] Figure 13 shows an alternative synchronous reference path;

[0039] Figure 14 shows another set of alternative synchronous reference paths;

[0040] Figure 15 is a flowchart of an example scanning process; and

[0041] Figure 16 is a flowchart of an example tracking process. Detailed Description

[0042] Before describing example embodiments in detail, it should be noted that the embodiments mainly relate to a combination of apparatus components and processing steps related to synchronous reference path selection for bistatic radar operation and multistatic radar operation in a cellular network. Accordingly, components are represented by conventional symbols in the drawings where appropriate, and only those specific details relevant to understanding the embodiments are shown so as not to obscure the present disclosure with details that will be readily apparent to those of ordinary skill in the art who have benefited from the description herein. Throughout the specification, the same numerals refer to the same elements.

[0043] As used herein, relational terms such as "first" and "second", "top" and "bottom", etc. may be used solely to distinguish one entity or element from another entity or element, and do not necessarily require or imply any physical or logical relationship or order between these entities or elements. The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the concepts described herein. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It will be further understood that the terms "comprises", "comprising", "includes", and / or "including", when used herein, specify the presence of the 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.

[0044] In the embodiments described herein, connection terms such as "communicating with" may be used to indicate electrical communication or data communication, which may be achieved, for example, by physical contact, induction, electromagnetic radiation, wireless signaling, infrared signaling, or optical signaling. Those of ordinary skill in the art will understand that multiple components may interoperate, and variations and alternatives for achieving electrical and data communication are possible.

[0045] In some embodiments described herein, the terms "coupled", "connected", etc. may be used herein to indicate a connection, although not necessarily a direct connection, and may include a wired connection and / or a wireless connection.

[0046] The term "network node" as used herein can be any kind of network node included in a radio network, which can also include a base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), gNodeB (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as an MSR BS, multi-cell / multicast coordination entity (MCE), integrated access and backhaul (IAB) node, relay node, donor node controlling the relay, radio access point (AP), transmission point, transmission node, remote radio unit (RRU), remote radio head (RRH), core network node (e.g., mobility management entity (MME), self-organizing network (SON) node, coordination node, positioning node, MDT node, etc.), external node (e.g., third-party node, node external to the current network), node in a distributed antenna system (DAS), spectrum access system (SAS) node, element management system (EMS), etc. A network node can also include a test device. The term "network node" as used herein can also be used to represent a wireless device (WD) or a radio base station.

[0047] In some embodiments, the non-limiting terms wireless device (WD) or user equipment (UE) can be used interchangeably. A WD herein can be any type of wireless device capable of communicating with a network node or another WD via radio signals, such as a wireless device (WD). A WD can also be a radio communication device, a target device, a device-to-device (D2D) WD, a machine type WD or a WD capable of machine-to-machine communication (M2M), a low-cost and / or low-complexity WD, a sensor equipped with a WD, a tablet, a mobile terminal, a smart phone, a laptop embedded equipment (LEE), a laptop mounted equipment (LME), a USB dongle, a customer premise equipment (CPE), an Internet of Things (IoT) device or a narrowband IoT (NB-IoT) device, etc.

[0048] Moreover, in some embodiments, the general term "radio network node" is used. It can be any kind of radio network node, which can include any one of a 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).

[0049] Note that although terms from a particular wireless system (such as, by way of example, 3GPP LTE and / or New Radio (NR)) may be used in this disclosure, this should not be construed as limiting the scope of the disclosure to the foregoing systems. Other wireless systems (including but not limited to Wideband 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 in this disclosure.

[0050] It should also be noted that the 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 nodes and wireless devices described herein are not limited to the performance of a single physical device and may in fact be distributed among several physical devices.

[0051] 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 should also be understood that the 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.

[0052] Some embodiments provide a method for selecting a synchronization reference path for bistatic radar operation and multistatic radar operation in a cellular network.

[0053] Some embodiments employ Over-the-Air (OTA) synchronization by using the same transmit signal as the illumination of an area in a bistatic radar deployment / multistatic radar deployment for receiver synchronization. This has several synchronization advantages required for accurate ranging and mobility detection through RF carrier phase change. With this scheme, reflections from objects arriving at or near the synchronization reference path in time may be masked and difficult to distinguish. This may lead to degradation in sensing of objects present at reflection points near the synchronization path or to degradation of synchronization.

[0054] Through some embodiments, accurate and robust over-the-air synchronization for radar sensing is achieved for bistatic-multistatic sensing.

[0055] Some embodiments include methods for mitigating such sensing degradation and providing robust synchronization by using Reconfigurable Intelligent Surfaces (RIS).

[0056] Referring again to the drawings, in which like elements are represented by like reference numerals, in Figure 4FIG. 0 shows a schematic diagram of a communication system 10 according to an embodiment, such as a 3GPP-type cellular network that may support standards such as LTE and / or NR (5G), which includes an access network 12 such as a radio access network and a core network 14. The access network 12 includes a plurality of network nodes 16a, 16b, 16c (collectively referred to as network nodes 16), such as NB, eNB, gNB, or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (collectively referred to as coverage areas 18). Each network node 16a, 16B, 16c may be connected to the core network 14 via a wired or wireless connection 20. A first wireless device (WD) 22a located in the coverage area 18a is configured to wirelessly connect to or be paged by the corresponding network node 16a. A second WD S22 in the coverage area 18b may wirelessly connect to the corresponding network node 16b. Although a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are shown in this example, the disclosed embodiments are equally applicable to the case where there is a single WD in the coverage area or a single WD is connected 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 more WDs 22 and network nodes 16.

[0057] Furthermore, it is conceivable that the WD 22 may communicate simultaneously and / or be configured to communicate with more than one network node 16 and more than one type of network node 16, respectively. For example, the WD 22 may have a dual connection with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, the WD 22 may communicate with an eNB for LTE / E-UTRAN and a gNB for NR / NG-RAN.

[0058] In some embodiments, the network node 16 and / or the WD 22 may be configured for bistatic sensing or multistatic sensing using a reconfigurable repeater (such as a RIS 35) in a synchronization reference path.

[0059] The communication system 10 itself can be connected to a host computer 24, which can be embodied in the hardware and / or software of a stand-alone server, a cloud-implemented server, a distributed server, or as processing resources in a server farm. The host computer 24 can be under the ownership or control of a service provider, or can be operated by or on behalf of a service provider. The connections 26, 28 between the communication system 10 and the host computer 24 can extend directly from the core network 14 to the host computer 24, or can extend via an optional intermediate network 30. The intermediate network 30 can be one or a combination of more than one of a public network, a private network, or a managed network. The intermediate network 30 (if any) can be a backbone network or the Internet. In some embodiments, the intermediate network 30 can include two or more sub-networks (not shown).

[0060] Figure 1 The communication system as a whole implements the connectivity between one of the connected WDs 22a, 22b and the host computer 24. This connectivity can 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 transmit signals via the OTT connection using the access network 12, the core network 14, any intermediate network 30, and possibly other infrastructure (not shown) as intermediaries. The OTT connection can be transparent in the sense that at least some of the participating communication devices through which the OTT connection passes are unaware of the routing of the uplink communication and the downlink communication. For example, the network node 16 may not be notified or need not be notified about the past routing of the input downlink communication, where data originating from the host computer 24 is to be forwarded (e.g., switched) to the connected WD 22a. Similarly, the network node 16 does not need to know the future routing of the output uplink communication originating from the WD 22a towards the host computer 24.

[0061] The network node 16 is configured to include a reference path selector 32, which is configured to scan for objects that are not resolvable in terms of one of distance, time, and angle from the location of a second reconfigurable intelligent surface (RIS) 35 using a first synchronization reference path via the first reconfigurable intelligent surface (RIS) 35. Similarly, the WD 22 can include a reference path selector 34, which is configured to scan for objects that are not resolvable in terms of one of distance, time, and angle from the location of a second reconfigurable intelligent surface (RIS) 35 using a first synchronization reference path via the first reconfigurable intelligent surface (RIS) 35. In some embodiments, the reference path selectors 32, 34 are configured to use a second synchronization reference path via a second reconfigurable reference path for synchronization between the network node and the WD in the event that the first synchronization reference path is interfered with or blocked.

[0062] Now reference will be made toFigure 5 Describe an example implementation of the WD 22, network node 16, and host computer 24 discussed in the foregoing paragraphs according to an embodiment. In the communication system 10, the host computer 24 includes hardware (HW) 38, and the hardware (HW) 38 includes a communication interface 40 configured to establish and maintain a wired or wireless connection with interfaces of different communication devices of the communication system 10. The host computer 24 further includes a processing circuit 42, which may have storage and / or processing capabilities. The processing circuit 42 may include a processor 44 and a memory 46. In particular, in addition to or instead of a processor (such as a central processing unit) and a memory, the processing circuit 42 may include an integrated circuit for processing and / or control, for example, one or more processors and / or processor cores and / or an FPGA (field programmable gate array) and / or an ASIC (application specific integrated circuit) suitable for executing instructions. The processor 44 may be configured to access (e.g., write to and / or read from) the memory 46, which may include any kind of volatile and / or non-volatile memory, such as a cache and / or a buffer memory and / or a RAM (random access memory) and / or a ROM (read only memory) and / or an optical memory and / or an EPROM (erasable programmable read only memory).

[0063] The processing circuit 42 may be configured to control any one of the methods and / or processes described herein and / or cause such methods and / or processes to be executed, for example, by the host computer 24. The processor 44 corresponds to one or more processors 44 for performing the functions of the host computer 24 described herein. The host computer 24 includes a memory 46 configured to store data, programming 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 the processing circuit 42, cause the processor 44 and / or the processing circuit 42 to execute the processes described herein with respect to the host computer 24. The instructions may be software associated with the host computer 24.

[0064] The software 48 can be executed by the processing circuitry 42. The software 48 includes a host application 50. The host application 50 can be operable to provide services to remote users, such as the WD 22 connected via an OTT connection 52 terminated at the WD 22 and the host computer 24. When providing services to remote users, the host application 50 can provide user data transmitted using the OTT connection 52. "User data" can be the data and information described herein for implementing the described functions. In one embodiment, the host computer 24 can be configured to provide control and functionality to a service provider and can be operated by or on behalf of the service provider. The processing circuitry 42 of the host computer 24 can enable the host computer 24 to observe the network node 16 and / or the wireless device 22, monitor the network node 16 and / or the wireless device 22, control the network node 16 and / or the wireless device 22, send to and / or receive from the network node 16 and / or the wireless device 22.

[0065] The communication system 10 further includes a network node 16 that is provided in the communication system 10 and includes hardware 58 that enables it to communicate with the host computer 24 and the WD 22. The hardware 58 can include a communication interface 60 for establishing and maintaining a wired or wireless connection for interfaces with different communication devices of the communication system 10, and a radio interface 62 for establishing and maintaining at least a wireless connection 64 with the WD 22 located in a coverage area 18 served by the network node 16. The radio interface 62 can be formed as or can include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The communication interface 60 can be configured to facilitate a connection 66 to the host computer 24. The connection 66 can be direct, or it can be through the core network 14 of the communication system 10 and / or through one or more intermediate networks 30 external to the communication system 10.

[0066] In the illustrated embodiment, the hardware 58 of 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 a memory, the processing circuitry 68 may include an integrated circuit for processing and / or control, for example, one or more processors and / or processor cores and / or FPGA (Field Programmable Gate Array) and / or ASIC (Application Specific Integrated Circuit) suitable for executing instructions. The processor 70 may be configured to access (e.g., write to and / or read from) the memory 72, which may include any kind of volatile memory and / or non-volatile memory, such as 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).

[0067] Accordingly, network node 16 also has software 74 stored internally, for example, in memory 72 or stored in an external memory (e.g., database, storage array, network storage device, etc.) accessible by 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 one of the methods and / or processes described herein and / or cause such methods and / or processes to be executed, for example, by network node 16. The processor 70 corresponds to one or more processors 70 for performing the functions of network node 16 described herein. The memory 72 is configured to store data, programming 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 the processing circuitry 68, cause the processor 70 and / or the processing circuitry 68 to execute the processes described herein with respect to network node 16. For example, the processing circuitry 68 of network node 16 may include a reference path selector 32 configured to scan for objects that are not resolvable in one of distance, time, and angle from the location of a second reconfigurable intelligent surface (RIS) 35 using a first synchronization reference path via a first RIS 35. In some embodiments, the reference path selector 32 is configured to use a second synchronization reference path via a second reconfigurable reference path for synchronization between the network node and the WD in the event that the first synchronization reference path is interfered with or blocked.

[0068] The communication system 10 further includes the aforementioned WD 22. The WD 22 may have hardware 80, which may include a radio interface 82 configured to establish and maintain a wireless connection 64 with a network node 16 serving the coverage area 18 where 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.

[0069] The hardware 80 of the WD 22 further includes a processing circuit 84. The processing circuit 84 may include a processor 86 and a memory 88. Specifically, in addition to or instead of a processor (such as a central processing unit) and a memory, the processing circuit 84 may include an integrated circuit for processing and / or control, for example, one or more processors and / or processor cores and / or FPGA (Field Programmable Gate Array) and / or ASIC (Application Specific Integrated Circuit) suitable for executing instructions. The processor 86 may be configured to access (e.g., write to and / or read from) the memory 88, which may include any kind of volatile memory and / or non-volatile memory, such as 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).

[0070] Thus, the WD 22 may further include software 90 stored, for example, in the memory 88 at the WD 22 or in an external memory accessible to the WD 22 (such as a database, a storage array, a network storage device, etc.). The software 90 may be executed by the processing circuit 84. The software 90 may include a client application 92. The client application 92 may be operable to provide services to a human or non-human user via the WD 22 while supporting the host computer 24. In the host computer 24, the executing host application 50 may communicate with the executing client application 92 via an OTT connection 52 terminated at the WD 22 and the host computer 24. When providing services 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 transmit both the request data and the user data. The client application 92 may interact with the user to generate the user data it provides.

[0071] The processing circuitry 84 may be configured to control any one and / or enable any one of the methods and / or processes described herein, such as being performed by the WD 22. The processor 86 corresponds to one or more processors 86 for performing the WD 22 functions described herein. The WD 22 includes a memory 88 configured to store data, programming 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 the processing circuitry 84, cause the processor 86 and / or the processing circuitry 84 to perform the processes described herein with respect to the WD 22. For example, the processing circuitry 84 of the wireless device 22 may include a reference path selector 34 configured to scan for objects that are non-resolvable in one of distance, time, and angle from the position of a second reconfigurable intelligent surface (RIS) 35 via a first synchronization reference path using a first RIS 35. In some embodiments, the reference path selector 34 is configured to use a second synchronization reference path via a second reconfigurable reference path for synchronization between the network node and the WD in the event that the first synchronization reference path is interfered with or blocked.

[0072] In some embodiments, the internal workings of the network node 16, the WD 22, and the host computer 24 may be as Figure 5 shown, and independently, the surrounding network topology may be Figure 4 of the network topology.

[0073] In Figure 5 , the OTT connection 52 has been drawn abstractly to show the communication between the host computer 24 and the wireless device 22 via the network node 16 without explicitly referring to any intermediate devices and the exact routing of the messages via these devices. The network infrastructure may determine the routing, which may be configured to hide from the WD 22 or from the service provider operating the host computer 24 or both. When the OTT connection 52 is active, the network infrastructure may further decide that it dynamically changes the routing (e.g., based on network load balancing considerations or reconfiguration).

[0074] 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 the OTT service provided to the WD 22 using the OTT connection 52, where 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 latency, relaxed restrictions on file size, better responsiveness, extended battery life, etc.

[0075] In some embodiments, a measurement process can be provided for the purpose of monitoring data rate, latency, and other factors that improve in one or more embodiments. In response to changes in the measurement results, there can also be optional network functions for reconfiguring the OTT connection 52 between the host computer 24 and the WD 22. The measurement process and / or network function for reconfiguring the OTT connection 52 can be implemented in the software 48 of the host computer 24 or in the software 90 of the WD 22 or in both. In an embodiment, sensors (not shown) can be deployed in or associated with the communication device through which the OTT connection 52 passes; the sensors can participate in the measurement process by supplying values of the monitored quantities illustrated above or other physical quantities from which the software 48, 90 can calculate or estimate the monitored quantities. The reconfiguration of the OTT connection 52 can include message format, retransmission settings, preferred routing, etc.; the reconfiguration need not affect the network node 16, and the network node 16 may not know or sense it. Some such processes and functions may be known and practiced in the art. In certain embodiments, the measurement can involve proprietary WD signaling that facilitates the host computer 24's measurement of throughput, propagation time, latency, etc. In some embodiments, the measurement can be implemented because the software 48, 90 causes messages, especially empty messages or "dummy" messages, to be sent using the OTT connection 52 while it monitors propagation time, errors, etc.

[0076] Thus, in some embodiments, the host computer 24 includes a processing circuit 42 configured to provide user data and a communication interface 40 configured to forward the user data to a cellular network for transmission to the WD 22. In some embodiments, the cellular network also includes a network node 16 having a radio interface 62. In some embodiments, the network node 16 is configured to and / or the network node 16 processing circuit 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 a reception of a transmission from the WD 22.

[0077] In some embodiments, the host computer 24 includes a processing circuit 42 and a communication interface 40 configured to receive user data originating from a transmission from the WD 22 to the network node 16. In some embodiments, the WD 22 is configured to and / or includes a radio interface 82 and / or a processing circuit 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 a reception of a transmission from the network node 16.

[0078] Although Figure 4 and Figure 5Various "units" such as reference path selector unit 32 and reference path selector unit 34 are shown as being within the respective processors, but it is contemplated that these units can be implemented such that a portion of the unit is stored in the corresponding memory within the processing circuitry. In other words, the unit can be implemented in the processing circuitry in hardware or in a combination of hardware and software.

[0079] Figure 6 is a flowchart showing an example method implemented in a communication system such as, for example, Figure 4 and Figure 5 The communication system can include a host computer 24, a network node 16, and a WD 22, which can be those described with reference to Figure 5 In a first step of the method, the host computer 24 provides user data (block S100). In an optional sub-step of the first step, the host computer 24 provides user data by executing a host application (e.g., host application 50) (block S102). In a second step, the host computer 24 initiates a transmission of the user data to the WD 22 (block S104). In an optional third step, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 16 sends the user data carried in the transmission initiated by the host computer 24 to the WD 22 (block S106). In an optional fourth step, the WD 22 executes a client application associated with the host application 50 executed by the host computer 24, such as client application 92 (block S108).

[0080] Figure 7 is a flowchart showing an example method implemented in a communication system such as, for example, Figure 4 The communication system can include a host computer 24, a network node 16, and a WD 22, which can be those described with reference to Figure 4 and Figure 5 In a first step of the method, the host computer 24 provides user data (block S110). In an optional sub-step (not shown), the host computer 24 provides user data by executing a host application (e.g., host application 50). In a second step, the host computer 24 initiates a transmission of the user data to the WD 22 (block S112). In accordance with the teachings of the embodiments described throughout this disclosure, the transmission can be relayed via the network node 16. In an optional third step, the WD 22 receives the user data carried in the transmission (block S114).

[0081] Figure 8 is a flowchart showing an example method implemented in a communication system such as, for example, Figure 4 The communication system can include a host computer 24, a network node 16, and a WD 22, which can be those described with reference toFigure 4 and Figure 5 as described. In an optional first step of the method, the WD 22 receives input data provided by the host computer 24 (block S116). In an optional sub-step of the first step, the WD 22 executes the client application 92, which provides user data in response to the received input data provided by the host computer 24 (block S118). Additionally or alternatively, in an optional second step, the WD 22 provides user data (block S120). In an optional sub-step of the second step, the WD provides user data by executing a client application (e.g., client application 92) (block S122). When providing user data, the executed client application 92 may also consider user input received from the user. Regardless of the specific manner of providing user data, the WD 22 may initiate the transmission of the user data to the host computer 24 in an optional third sub-step (block S124). In a fourth step of the method, the host computer 24 receives the user data sent from the WD 22 according to the teachings of the embodiments described throughout this disclosure (block S126).

[0082] Figure 9 is a flowchart showing an example method implemented in a communication system such as, for example Figure 4 of a communication system. 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 Figure 4 and Figure 5 as described. In an optional first step of the method, according to 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 the 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 S132).

[0083] Figure 10It is a flowchart of an example process for synchronous reference path selection for bistatic radar operation and multistatic radar operation in a cellular network in network node 16 or wireless device 22. One or more of the boxes described herein may be performed by one or more elements of network node 16, such as by processing circuits 68 or 84 (including reference path selection units 32 or 34), processors 70 or 86, radio interfaces 62 or 82, and / or communication interface 60. The process includes scanning for objects that are not resolvable in one of distance, time, and angle from the location of a second reconfigurable intelligent surface (RIS) 35 using a first synchronous reference path via the first RIS 35 (block S134). The process includes, when an object that is not resolvable from the location of the second RIS 35 is detected, selecting the first synchronous reference path for subsequent detection of the object (block S136). In some embodiments, the method further includes tracking the object using the first synchronous reference path. In some embodiments, the method includes switching between a first synchronous reference path via the first RIS 35 and a second synchronous reference path via the second RIS 35. In some embodiments, the switching occurs according to a pattern that is at least partially based on the latency allowable for detecting an object during a radar scan. In some embodiments, the second synchronous path is selected based at least in part on at least one of time of arrival (ToA) and time of flight (ToF). In some embodiments, the decision to switch between the first synchronous reference path and the second synchronous reference path is at least partially based on a prediction of the future location of the object. In some embodiments, the method includes monitoring multiple synchronous reference paths and selecting a reference path based on the resolvability of the object for each synchronous reference path. In some embodiments, the method further includes monitoring the time of arrival for each of the multiple synchronous reference paths to prevent interference spoofing. In some embodiments, the method includes ensuring that objects close to the RIS do not affect the synchronous path by causing degradation of the synchronous path resolution. In some embodiments, the method includes selecting a reference path that does not have degradation of synchronous resolution due to nearby objects.

[0084] Figure 11It is a flowchart of another example process for selecting a synchronization reference path for bistatic radar operation and multistatic radar operation in a cellular network in the first network nodes 16, 22 and the second network nodes 16, 22. One or more of the boxes described herein may be performed by one or more elements of the network node 16 or the wireless device 22, such as by the processing circuit 68 or 84 (including the reference path selection unit 32 or 34), the processor 70 or 86, the radio interface 62 or 82, and / or the communication interface 60. The process includes: selecting a first synchronization reference path via a first reconfigurable repeater for synchronization between the first network nodes 16, 22 and the second network nodes 16, 22, the first synchronization reference path being resolvable from a second synchronization path including a second reconfigurable repeater, the first synchronization reference path being selected to be resolvable from an object (block S138). The method includes: in the case where the first synchronization reference path is interfered with or blocked, using a second synchronization reference path via a second reconfigurable reference path for synchronization between the first network node and the second network node (block S140).

[0085] According to this aspect, in some embodiments, the method includes using the first synchronization reference path to track an object. In some embodiments, the switching between the first synchronization reference path and the second synchronization reference path occurs according to a pattern that is at least partially based on the allowable delay for detecting an object during a radar scan. In some embodiments, one of the first synchronization reference path and the second synchronization reference path is selected at least partially based on at least one of the time of arrival ToA and the time of flight ToF. In some embodiments, the decision to switch between the first synchronization reference path and the second synchronization reference path is at least partially based on a prediction of the future position of the object. In some embodiments, the method includes monitoring a plurality of synchronization reference paths and selecting a reference path at least partially based on the resolvability of the object for each synchronization reference path. In some embodiments, the method includes monitoring the time of arrival for each of the first synchronization reference path and the second synchronization reference path to prevent interference spoofing. In some embodiments, at least one of the first synchronization reference path and the second synchronization reference path includes a passive reflector. In some embodiments, using the second synchronization reference path includes changing the reference path angle or delay for the second synchronization reference path. In some embodiments, the first network node is one of a WD and a radio base station, and the second network node is one of a WD and a radio base station.

[0086] Having described the general process flow of the arrangement of the present disclosure and having provided examples of the hardware arrangement and the software arrangement for implementing the processes and functions of the present disclosure, the following sections provide details and examples of the arrangement for selecting a synchronization reference path for bistatic radar operation and multistatic radar operation in a cellular network.

[0087] If the NLOS synchronization reference path has a stable and well-characterized channel (e.g., measured by TX and RX node round trip time (RTT)), the NLOS synchronization reference path can be created from base objects that already exist in the environment, or it can be artificially created by placing reflectors at known and suitable locations in the area. It is assumed here that the direction and ToF (T ref_path ) is known. As mentioned above and as Figure 12 As shown, reflections from objects that arrive or are close in time (which depends on the bandwidth and receiver resolution) and in the spatial direction of the reference path may be indistinguishable from reflections from the synchronized reference path.

[0088] exist Figure 12 Having two passive conventional reflectors in the scenario shown will likely not resolve the problem of resolving objects close to the reflection point of the synchronous paths. As an example, using NLOS2 instead of NLOS1 (where the paths are separated in time, T NLOS1 ≠T NLOS2 ) for detecting object "A" may still result in reflections from NLOS1 occurring when illuminating object "A", and vice versa for detecting object "B". By using NLOS1, reflections from NLOS2 will still be present and interfere with reflections from object B.

[0089] Instead, a method using a reconfigurable smart surface (RIS 35) is disclosed for a synchronization path. The method includes the possibility of reconfiguring the RIS 35 in some cases to detect or track objects close to the RIS 35, and to change the characteristics of the synchronization reference path. For example, the method may include one or both of the following: For object "A", disable the synchronization reference path reflected by RIS1 to the bistatic receiver and enable an alternative synchronization path by using another RIS 35 (RIS2) or creating an alternative path from RIS1, e.g. through a passive reflector; • changing the delay for the synchronization path by a known amount via the RIS 35; and • Changing the reference path angle and / or delay for the new synchronization reference path.

[0090] exist Figure 13 In the example shown, available configuration options and specific characteristics for each available synchronization path may be known for both the TX node and the RX node. Such characteristics may include direction and ToF (T ref_path ), either by the known position of the node in the path or by pre-characterization, such as by over-the-air RTT measurements. Alternative synchronization paths to the receiver can be made at time (Tref_path ) or direction of arrival (AoA) or both with different channel performances (depending on the time domain resolution and the spatial domain resolution of the bistatic system) for detecting objects close to the reflection points of the synchronization path.

[0091] To detect objects in the environment, the TX node and the RX node will periodically perform bistatic radar scans of the surrounding environment, as Figure 12 shown. Figure 12 Examples are included for changing the reference path to avoid problems of detecting objects reflected close to the reference path. The switching period and mode can be set based on the maximum allowed delay for detecting such objects during the radar scan.

[0092] Figure 15 An example process of the scan mode of the bistatic radar is shown in. In the first step, the characteristics of the available synchronization reference paths are obtained (block S142). If scanning using the active synchronization reference path does not result in active objects (block S144), then an alternative synchronization reference path is tried (block S146). If no alternative synchronization reference path leading to resolvable objects is found, the scanning device (i.e., network node 16 or WD 22) coordinates with other transmit-receive pairs to track the object (block S148). Once a synchronization reference path enabling object resolution is found, the scanning device is configured to use that synchronization reference path to detect objects (block S150).

[0093] When the bistatic radar operates in the tracking mode, i.e., when it tracks objects detected at regular intervals, the bistatic radar knows the direction of arrival (AoA) and the ToF (T object ) of the reflection path for the object, and can use this information to select the most appropriate synchronization reference path. In some cases, when one or the other is not available, the path can be selected based on either the ToA or the ToF. In a tracking scenario for a moving object, it is known when the tracked object has changed to a position where the synchronization reference path needs to be switched. In such cases, considering the system range resolution, it is allowed to change the reference path characteristics before such an event and ensure that the objects can still be separated, and spatial domain resolution can occur. The selection of the reference path for the tracked object can also be based on the prediction of the future position of the object through velocity estimation, and there is a hysteresis to avoid overly frequent switching.

[0094] Figure 16An example process of the tracking mode of a bistatic radar is shown. In a first step, the characteristics of available synchronization reference paths are obtained (block S142). Time-of-Flight (ToF) or airspace data for each tracked object is obtained (block S154). Optionally, the tracking device (network node 16 or WD 22) may obtain speed information of the tracked object (block S156). For each tracked object, a synchronization reference path that can be resolved from the object is selected (block S158). When the tracked object is approaching and cannot be resolved by the synchronization reference path (block S160), an alternative path is searched for (block S162). If no alternative path is found, the scanning device (i.e., network node 16 or WD 22) coordinates with other transmit-receive pairs to track the object (block S164). Once a synchronization reference path enabling object resolution is found, the scanning device is configured to use this synchronization reference path to detect the object (block S166).

[0095] The bistatic radar operation can periodically change the roles of the TX node and the RX node (i.e., at certain times, one node in the pair acts as the TX and the other as the RX, and at another time, the roles are reversed), and the TX and RX can share radar information with each other. The reference path used can change with the role change, and thus, each receiver can use the same reference path and sensing limitations in a certain bistatic sensing direction, which may not exist in another direction when different synchronization paths are used in different directions. As used hereinafter, the TX and RX can be network node 16 and / or wireless device 22.

[0096] The RIS 35 can be controlled and configured by the TX, RX, or a central node, and for the previously described bistatic TX-RX roles, the change can depend on the direction of the reference path.

[0097] The synchronization path may be blocked by objects in the environment and / or be subject to unintentional or intentional interference. Similar to the problem of detecting and differentiating objects near the NLOS reflection points of the synchronization reference path, the reflections from such objects may also affect the receiver's ability to distinguish and accurately resolve the synchronization reference. This may create uncertainty in its reception time, thus degrading the radar sensing of all objects. Therefore, as used in Figure 13 and Figure 14 shown, Figure 4 and Figure 5 shown, the RIS 35 can be used to increase the robustness and performance of the synchronization path. The receiver can periodically monitor the quality of the reference path alternatives created by the RIS 35 and select the most suitable reference path. The monitoring can also include checking the relative arrival times between different paths to detect interference spoofing that attempts to manipulate the arrival time of one of the synchronization paths. Thus, in some embodiments, the synchronization reference path is selected to avoid blocking and / or interference.

[0098] Some embodiments may include one or more of the following:

[0099] Embodiment A1. A network node configured to communicate with a wireless device (WD), the network node configured to and / or include a radio interface and / or include a processing circuit, the processing circuit configured to: Scan for an object that is not resolvable in one of distance, time, and angle from the location of a second reconfigurable intelligent surface (RIS) using a first synchronization reference path via a first RIS; and When an object that is not resolvable from the location of the second RIS is detected, select the first synchronization reference path for subsequent detection of the object.

[0100] Embodiment A2. The network node according to Embodiment A1, wherein the processing circuit is further configured to track the object using the first synchronization reference path.

[0101] Embodiment A3. The network node according to any one of Embodiments A1 and A2, wherein the processing circuit is further configured to switch between a first synchronization reference path via the first RIS and a second synchronization reference path via the second RIS.

[0102] Embodiment A4. The network node according to Embodiment A3, wherein the switching occurs according to a pattern that is at least partially based on a latency allowable for detecting an object during a radar scan.

[0103] Embodiment A5. The network node according to any one of Embodiments A3 and A4, wherein the second synchronization path is selected at least partially based on at least one of time of arrival (ToA) and time of flight (ToF).

[0104] Embodiment A6. The network node according to any one of Embodiments A3 to A5, wherein the decision to switch between the first synchronization reference path and the second synchronization reference path is at least partially based on a prediction of the future location of the object.

[0105] Embodiment A7. The network node according to any one of Embodiments A1 to A6, wherein the processing circuit is further configured to monitor a plurality of synchronization reference paths and select a reference path based on the resolvability of the object for each synchronization reference path.

[0106] Embodiment A8. The network node according to Embodiment 7, wherein the processing circuit is further configured to monitor the time of arrival for each of the plurality of synchronization reference paths to prevent interference spoofing.

[0107] Example A9. The network node according to any one of Examples A1 to A8, wherein the network node is one of a wireless device (WD) and a radio base station.

[0108] Example B1. A method implemented in a network node, the network node being one of a wireless device (WD) and a radio base station, the method comprising: Scanning for an object that is not resolvable in one of distance, time, and angle from the location of a second reconfigurable intelligent surface (RIS) using a first synchronization reference path via a first RIS; and When an object that is not resolvable from the location of the second RIS is detected, selecting the first synchronization reference path for subsequent detection of the object.

[0109] Example B2. The method according to Example A1, further comprising tracking the object using the first synchronization reference path.

[0110] Example B3. The method according to any one of Examples A1 and A2, further comprising: switching between a first synchronization reference path via the first RIS and a second synchronization reference path via the second RIS.

[0111] Example B4. The method according to Example A3, wherein the switching occurs according to a pattern that is at least partially based on a delay allowable for detecting an object during a radar scan.

[0112] Example B5. The method according to any one of Examples A3 and A4, wherein the second synchronization path is selected based at least in part on at least one of time of arrival (ToA) and time of flight (ToF).

[0113] Example B6. The method according to any one of Examples A3 to A5, wherein the decision to switch between the first synchronization reference path and the second synchronization reference path is at least partially based on a prediction of the future position of the object.

[0114] Example B7. The method according to any one of Examples A1 to A6, further comprising: monitoring a plurality of synchronization reference paths and selecting a reference path based on the resolvability of the object for each synchronization reference path.

[0115] Example B8. The method according to Example 7, further comprising monitoring the time of arrival for each of the plurality of synchronization reference paths to prevent interference spoofing.

[0116] As those skilled in the art will appreciate, the concepts described herein can be embodied as a method, a data processing system, a computer program product, and / or a computer storage medium storing executable computer programs. Thus, the concepts described herein can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software aspects and hardware aspects, all of which are generally referred to herein as "circuits" or "modules" in this document. Any process, step, action, and / or function described herein can be performed by and / or associated with a corresponding module, which can be implemented in software and / or firmware and / or hardware. In addition, the present disclosure can take the form of a computer program product on a tangible computer-usable storage medium having computer program code embodied in the medium that can be executed by a computer. Any suitable tangible computer-readable medium can be utilized, including a hard disk, a CD-ROM, an electronic storage device, an optical storage device, or a magnetic storage device.

[0117] Some embodiments are described herein with reference to flowcharts and / or block diagrams of methods, systems, and computer program products. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer (thereby creating a special-purpose computer), a special-purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions executed via the processor of the computer or other programmable data processing apparatus create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0118] These computer program instructions can also be stored in a computer-readable memory or storage medium, which can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0119] The computer program instructions can 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 executed on the computer or other programmable apparatus provide steps for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0120] It should be understood that the functions / actions indicated in the boxes may not occur in the order indicated in the operating instructions. For example, depending on the functions / actions involved, two consecutively shown boxes may actually be executed substantially simultaneously, or the boxes may sometimes be executed in the reverse order. Although some of the figures include arrows on the communication paths to indicate the main communication direction, it should be understood that the communication may occur in the direction opposite to the depicted arrows.

[0121] Computer program code for performing the operations of the concepts described herein may be written in an object-oriented programming language (such as Python, or C++). However, the computer program code for performing the operations of the present disclosure may also be written in a conventional procedural programming language (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 may be connected to an external computer (e.g., using an Internet service provider via the Internet).

[0122] Numerous different embodiments have been disclosed herein in connection with the above description and the drawings. It should be understood that it would be inappropriate to repeat and obscure each combination and sub-combination of these embodiments by literal description and illustration. Accordingly, all embodiments may be combined in any manner and / or combination, and this specification (including the drawings) should be construed as constituting a complete written description of all combinations and sub-combinations of the embodiments described herein, and the manner and process of making and using them, and should support claims to any such combination or sub-combination.

[0123] Those skilled in the art will understand that the embodiments described herein are not limited to what has been specifically shown and described above. Additionally, unless stated to the contrary above, it should be noted that all of the drawings are not drawn to scale. Various modifications and variations can be made in accordance with the above teachings without departing from the scope of the appended claims.

Claims

1. A first network node (16, 22), configured to communicate with a second network node (16, 22) via a radio frequency channel, the first network node (16, 22) being configured to: Select a first synchronization reference path via a first reconfigurable repeater for synchronization between the first network node (16, 22) and the second network node (16, 22), the first synchronization reference path being resolvable from a second synchronization path including a second reconfigurable repeater, the first synchronization reference path being selected to be resolvable from an object; and In the case where the first synchronization reference path is interfered with or blocked, use the second synchronization reference path via the second reconfigurable reference path for synchronization between the first network node (16, 22) and the second network node (16, 22).

2. The first network node (16, 22) according to claim 1, wherein the first network node (16, 22) is configured to use the first synchronization reference path to detect and track an object.

3. The first network node (16, 22) according to any one of claims 1 and 2, wherein the switching between the first synchronization reference path and the second synchronization reference path occurs according to a pattern based at least in part on the allowable delay for detecting an object during a radar scan.

4. The first network node (16, 22) according to any one of claims 1 to 3, wherein one of the first synchronization reference path and the second synchronization reference path is selected at least in part based on at least one of time of arrival ToA and time of flight ToF.

5. The first network node (16, 22) according to any one of claims 1 to 4, wherein the decision to switch between the first synchronization reference path and the second synchronization reference path is based at least in part on a prediction of the future position of the object.

6. The first network node (16, 22) according to any one of claims 1 to 5, wherein the first network node (16, 22) is configured to monitor a plurality of synchronization reference paths and select a reference path at least in part based on the resolvability of the object for each synchronization reference path.

7. The first network node (16, 22) according to any one of claims 1 to 6, wherein the first network node (16, 22) is further configured to monitor the time of arrival for each of the first synchronization reference path and the second synchronization reference path to prevent interference spoofing.

8. The first network node (16, 22) according to any one of claims 1 to 7, wherein at least one of the first synchronization reference path and the second synchronization reference path includes a passive reflector.

9. The first network node (16, 22) according to any one of claims 1 to 8, wherein using the second synchronization reference path includes changing the reference path angle or delay for the second synchronization reference path.

10. The first network node (16, 22) according to any one of claims 1 to 7, wherein the first network node (16, 22) is one of a WD (22) and a radio base station, and the second network node is one of a WD (22) and a radio base station.

11. A method implemented in a first network node (16, 22), the first network node (16, 22) being configured to communicate with a second network node (16, 22), the method comprising: Selecting (S138) a first synchronization reference path via a first reconfigurable repeater for synchronization between the first network node (16, 22) and the second network node (16, 22), the first synchronization reference path being resolvable from a second synchronization path including a second reconfigurable repeater, the first synchronization reference path being selected to be resolvable from an object; And In the case where the first synchronization reference path is interfered with or blocked, using (S140) the second synchronization reference path via the second reconfigurable reference path for synchronization between the first network node (16, 22) and the second network node (16, 22).

12. The method according to claim 11, further comprising using the first synchronization reference path to track an object.

13. The method according to any one of claims 11 and 12, wherein the switching between the first synchronization reference path and the second synchronization reference path occurs according to a pattern based at least in part on a delay allowable for detecting an object during a radar scan.

14. The method according to any one of claims 11 to 13, wherein one of the first synchronization reference path and the second synchronization reference path is selected based at least in part on at least one of time of arrival ToA and time of flight ToF.

15. The method according to any one of claims 11 to 14, wherein the decision to switch between the first synchronization reference path and the second synchronization reference path is based at least in part on a prediction of the future position of the object.

16. The method according to any one of claims 11 to 15, further comprising: Monitoring a plurality of synchronization reference paths and selecting a reference path based at least in part on the resolvability of the object for each synchronization reference path.

17. The method according to any one of claims 11 to 15, further comprising: Monitoring the time of arrival for each of the first synchronization reference path and the second synchronization reference path to prevent interference spoofing.

18. The method according to any one of claims 11 to 17, wherein at least one of the first synchronization reference path and the second synchronization reference path includes a passive reflector.

19. The method according to any one of claims 11 to 18, wherein using the second synchronization reference path includes changing a reference path angle or delay for the second synchronization reference path.

20. The method according to any one of claims 11 to 19, wherein the first network node (16, 22) is one of a wireless device WD (22) and a radio base station, and the second network node is one of a WD (22) and a radio base station.

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