Precoding Tracking for Cell-Free Massive MIMO

Abstract

A method may include sending, by a network node within a wireless network, a first precoded tracking signal to a reference node based on estimated precoding weights, the estimated precoding weights being estimated to provide a predetermined signal at the reference node; receiving, by the network node, a message from the reference node comprising information regarding whether the predetermined signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node; if the predetermined signal is not received at the reference node, adjusting, by the network node, one or more transmission parameters of the network node that are estimated to more accurately provide the predetermined signal at the reference node; and sending, by the network node, a second precoded tracking signal based on the adjusted transmission parameters.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 947,097, filed on December 12, 2019, entitled “PRECODING TRACKING FOR CELL FREEMASSIVE MIMO,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] This specification relates to wireless communications. Background Art

[0004] A communication system may be a facility that enables communication between two or more nodes or devices (such as fixed or mobile communication devices). Signals may be carried on wired or wireless carriers.

[0005] An example of a cellular communication system is the architecture standardized by the Third Generation Partnership Project (3GPP). The latest development in this area is generally referred to as the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology. EUTRA (Evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), called enhanced nodes AP (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices or mobile stations are called user equipment (UEs). LTE has included many improvements or developments. Various aspects of LTE are also constantly being improved.

[0006] The development of 5G New Radio (NR) is part of the ongoing mobile broadband evolution process to meet the requirements of 5G, similar to the earlier evolution of 3G and 4G wireless networks. In addition to mobile broadband, 5G also targets emerging use cases. One goal of 5G is to significantly improve wireless performance, which can include higher levels of data rate, latency, reliability and security. 5G NR can also be extended to efficiently connect the massive Internet of Things (IoT) and can provide new mission-critical services. For example, ultra-reliable low-latency communication (URLLC) equipment may require high reliability and very low latency. Summary of the Invention

[0007] According to an example embodiment, a method may include: sending, by a network node within a wireless network, a first precoded tracking signal to a reference node based on estimated precoding weights, the estimated precoding weights being estimated to provide a predetermined signal at the reference node; receiving, by the network node, a message from the reference node including information regarding whether the predetermined signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node; if the predetermined signal is not received at the reference node, adjusting, by the network node, one or more transmission parameters of the network node that are estimated to more accurately provide the predetermined signal at the reference node; and sending, by the network node, a second precoded tracking signal based on the adjusted transmission parameters.

[0008] According to another example embodiment, a method may include sending, by a network node within a wireless network, a first precoded tracking signal to a reference node based on estimated precoding weights, the estimated precoding weights being estimated to provide a predetermined signal at the reference node; receiving, by the network node, feedback from the reference node, the feedback relating to precoding performance based at least on the first precoded tracking signal; and adjusting, based on the received feedback, one or more transmission parameters of the network node that were estimated to more accurately provide the predetermined signal at the reference node.

[0009] According to another example embodiment, a method may include receiving, by a reference node, a first signal based at least in part on a first precoded tracking signal received by the reference node from at least one network node; determining, by the reference node, whether the first signal is a predetermined signal; sending, by the reference node, a message to at least one network node, the message relating to whether the predetermined signal is received at the reference node; and if the predetermined signal is not received at the reference node, receiving, by the reference node, a second signal based at least in part on an adjusted transmission parameter for at least one network node, the adjusted transmission parameter being adjusted in response to the message.

[0010] According to another example embodiment, a method may include receiving, by a reference node, a first signal based at least in part on a first precoded tracking signal received by the reference node from at least one network node, wherein the first signal is provided at the reference node based on a collaborative joint transmission of precoded signals from a plurality of network nodes; determining, by the reference node, whether the first signal is a predetermined signal; and sending, by the reference node, a message to at least one network node, the message relating to whether the predetermined signal was received at the reference node.

[0011] According to another example embodiment, a method may include receiving, by a wireless node within a wireless network, an instruction from a network node to transmit a phase tracking reference signal on behalf of the network node; and transmitting, by the wireless node, the phase tracking reference signal to one or more user equipment based on the instruction.

[0012] Additional example embodiments are provided or described for each of the example methods, including: a component for performing any of the example methods; a non-transitory computer-readable storage medium including instructions stored thereon, which, when executed by at least one processor, are configured to cause a computing system to perform any of the example methods; and an apparatus including at least one processor and at least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least perform any of the example methods.

[0013] The details of one or more examples of embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a block diagram of a wireless network according to an example embodiment.

[0015] Figure 2 is a diagram of a system in which a reference node may track precoding performance from one or more network nodes and provide feedback on precoding performance according to an example embodiment.

[0016] Figure 3 is a diagram illustrating the operation of a network according to an example embodiment.

[0017] Figure 4 is a diagram illustrating an antenna system including a plurality of antenna elements according to example embodiments.

[0018] Figure 5 is a diagram illustrating the strongest multipath components (MPCs) from multiple network nodes (or TRPs).

[0019] Figure 6 is a diagram illustrating one or more reference nodes transmitting a wide beam phase tracking reference signal to one or more user equipments according to an example embodiment.

[0020] Figure 7 is a flow chart illustrating the operation of a network node according to an example embodiment.

[0021] Figure 8 is a flow chart illustrating the operation of a network node according to another example embodiment.

[0022] Figure 9 is a flowchart illustrating the operation of a reference node according to an example embodiment.

[0023] Figure 10 is a flowchart illustrating the operation of a reference node according to another example embodiment.

[0024] Figure 11 is a flow chart illustrating the operation of a wireless node according to an example embodiment.

[0025] Figure 12 is a block diagram of a wireless station, wireless node, or network node (e.g., a network node, AP, BS, RAN node, gNB, UE or user equipment, receiver device, or other network node) according to an example embodiment. DETAILED DESCRIPTION

[0026] Figure 1 is a block diagram of a wireless network 130 according to an example embodiment. Figure 1 In a wireless network 130, user devices 131, 132, 133, and 135 (also referred to as mobile stations (MSs) or user equipment (UEs)) can connect to (and communicate with) a base station (BS) 134, which can also be referred to as an access point (AP), an enhanced Node B (eNB), a BS, a next-generation Node B (gNB), a next-generation enhanced Node B (ng-eNB), or a network node. The terms user device or user equipment (UE) can be used interchangeably. The BS can also include or be referred to as a RAN (Radio Access Network) node, and can include a portion of a BS or a portion of a RAN node, such as (for example, such as a central or centralized unit (CU) and / or a distributed unit (DU) in the case of a split BS). At least a portion of the functionality of a BS (e.g., an access point (AP), a base station (BS), or an (e)Node B (eNB), a BS, a RAN node) can also be performed by any node, server, or host that can be operably coupled to a transceiver (such as a remote radio head). BS (or AP) 134 provides wireless coverage within cell 136, including to user equipment (or UE) 131, 132, 133, and 135. Although only four user equipment (or UE) are shown as connected or attached to BS 134, any number of user equipment may be provided. BS 134 is also connected to core network 150 via an S1 interface or NG interface 151. This is just one simple example of a wireless network, and other wireless networks may be used.

[0027] A base station (e.g., such as BS 134) is an example of a radio access network (RAN) node within a wireless network. A BS (or RAN node) may be or may include (or may alternatively be referred to as), for example, an access point (AP), a gNB, an eNB, or a portion thereof (such as a centralized unit (CU) and / or a distributed unit (DU) in the case of a split BS or split gNB), or other network node.

[0028] According to an illustrative example, a BS node (e.g., BS, eNB, gNB, CU / DU, etc.) or a radio access network (RAN) may be part of a mobile telecommunications system. The RAN (radio access network) may include one or more BSs or RAN nodes that implement a radio access technology, for example, to allow one or more UEs to access a network or core network. Thus, for example, a RAN (RAN node, such as a BS or gNB) may reside between one or more user devices or UEs and a core network. According to an example embodiment, each RAN node (e.g., BS, eNB, gNB, CU / DU, etc.) or BS may provide one or more wireless communication services to one or more UEs or user devices, for example, to allow the UEs to wirelessly access the network via the RAN node. Each RAN node or BS may perform or provide wireless communication services, for example, such as to allow the UEs or user devices to establish a wireless connection to the RAN node and to send data to and / or receive data from one or more of the UEs. For example, after establishing a connection to a UE, a RAN node (e.g., a base station (BS), eNB, gNB, CU / DU, etc.) may forward data received from the network or core network to the UE and / or forward data received from the UE to the network or core network. RAN nodes (e.g., BS, eNB, gNB, CU / DU, etc.) may perform various other wireless functions or services, such as broadcasting control information (e.g., such as system information) to the UE, paging the UE when data is available for delivery, assisting the UE in handovers between cells, scheduling resources for uplink data transmission from (multiple) UEs and downlink data transmission to (multiple) UEs, sending control information for configuring one or more UEs, and so on. These are just a few examples of one or more functions that a RAN node or BS may perform. A base station may also be the DU (distributed unit) portion of an IAB (integrated access and backhaul) node (also known as a relay node). The DU facilitates access link connectivity for the IAB node. A transmitter receiver point (TRP) may include any network node capable of transmitting and / or receiving signals.

[0029] A user device (user terminal, user equipment (UE), mobile terminal, handheld wireless device, etc.) may refer to a portable computing device including a wireless mobile communication device operating with or without a subscriber identity module (SIM), including but not limited to the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handheld device, a device using a wireless modem (alarm or measurement device, etc.), a laptop and / or touch screen computer, a tablet computer, a tablet phone, a game console, a notebook computer, a vehicle, a sensor and multimedia device, or any other wireless device. It should be understood that a user device may also be (or may include) an almost exclusively uplink-only device, an example of which is a camera or camcorder that uploads images or video clips to a network. A user device may also be the MT (mobile terminal) portion of an IAB (integrated access and backhaul) node (also known as a relay node). The MT facilitates the backhaul connection of the IAB node.

[0030] In LTE (as an illustrative example), the core network 150 may be referred to as an evolved packet core (EPC), which may include a mobility management entity (MME) that may handle or assist mobility / handover of user equipment between BSs, one or more gateways that may forward data and control signals between the BS and a packet data network or the Internet, and other control functions or blocks. Other types of wireless networks, such as 5G (which may be referred to as new radio (NR)), may also include a core network.

[0031] Furthermore, as illustrative examples, the various example embodiments or techniques described herein may be applied to various types of user devices or data service types, or may be applied to user devices on which multiple applications may be running, each of which may be of different data service types. New Radio (5G) developments may support a variety of different applications or a variety of different data service types, such as machine type communication (MTC), enhanced machine type communication (eMTC), Internet of Things (IoT) and / or narrowband Internet of Things (NB-IoT) user devices, enhanced mobile broadband (eMBB), and ultra-reliable low latency communication (URLLC). Many of these new 5G (NR) related applications may require higher performance than previous wireless networks.

[0032] The IoT can refer to the growing group of objects that can have internet or network connectivity, allowing them to send and receive information to other network devices. For example, many sensor-type applications or devices can monitor physical conditions or states and send reports to servers or other network devices, such as when events occur. For example, machine-type communication (MTC, or machine-to-machine communication) can be characterized by fully automated data generation, exchange, processing, and actuation between intelligent machines, with or without human intervention. Enhanced mobile broadband (eMBB) can support higher data rates than currently available in LTE.

[0033] Ultra-Reliable Low Latency Communication (URLLC) is a new data service type or new use case that the New Radio (5G) system can support. This enables emerging new applications and services such as industrial automation, autonomous driving, vehicle safety, e-health services, etc. As an illustrative example, 3GPP aims to provide connectivity with reliability corresponding to a block error rate (BLER) of 10-5 and a U-plane (user / data plane) latency of up to 1ms. Thus, for example, a URLLC user equipment / UE may require a significantly lower block error rate (BLER) and low latency (with or without a simultaneous high reliability requirement) than other types of user equipment / UE. Thus, for example, a URLLC UE (or a URLLC application on a UE) may require shorter latency than an eMBB UE (or an eMBB application running on a UE).

[0034] Various example embodiments may be applied to a variety of wireless technologies or wireless networks, such as LTE, LTE-A, 5G (New Radio (NR)), cmWave and / or mmWave band networks, IoT, MTC, eMTC, eMBB, URLLC, etc., or any other wireless network or wireless technology. These example networks, technologies, or data service types are provided as illustrative examples only.

[0035] A network node (e.g., a base station or gNB, a DU, a CU, a user equipment terminal or receiver device, a relay station or relay node, a transmitter receiver point (TRP), a remote radio head (RRH), or other network node) can employ beamforming, wherein a set of antenna weights can be applied to generate a specific antenna beamwidth and shape for transmission or reception (e.g., to obtain beamforming gain), rather than using an omnidirectional antenna. An antenna (or antenna array) can include multiple antenna elements, wherein a specific beam (e.g., including a beam direction and / or beamwidth) can be generated or obtained by applying a set of antenna weights (e.g., each antenna weight including an amplitude and a phase) to the antenna array, with different weights applied to each antenna element. For example, the direction of a beam from a phased antenna array can be changed by adjusting the phase of the signal applied to each element in the antenna array. Thus, for example, a transmit beam can be generated for transmitting signals, and / or a receive beam can be generated for receiving signals, e.g., to provide beamforming gain for the received signals.

[0036] In addition, for example, the UE (or user equipment or receiver device) can be configured to send a measurement report (e.g., a channel state information measurement report) to the BS (or other network node). For example, the BS can configure the UE to measure one or more quantities of one or more resources or beams (e.g., reference signal received power (RSRP), determine channel state information (CSI), or determine or measure other information or quantities). Thus, the measurement report configuration can indicate one or more quantities to be measured for one or more specific resources or beams. For example, the UE can be configured to measure and report one or more quantities, such as CSI and / or RSRP for a channel state information reference signal (CSI-RS) beam and / or a synchronization signal block (SSB) beam. As an illustrative example, the UE can measure one or more signal parameters (e.g., link quality) of a reference signal received from the BS and can send a channel state information (CSI) report to the BS. An example CSI report may include, for example, one or more of: RSRP (reference signal received power); a rank indicator (RI), which is the appropriate number of transmission layers for a downlink (DL) transmission; a precoder matrix indicator (PMI), which may indicate to a device (e.g., a UE) what is estimated to be an appropriate precoder matrix based on the selected rank; and a channel quality indication (or channel quality indicator) (CQI), which may express or indicate the BS-UE channel or link quality measured by the UE. The CQI may indicate what the UE estimates to be an appropriate channel coding rate and modulation scheme based on the selected precoder matrix. In general, precoding may include the UE (or other node) applying a set of precoding weights (each weight including an amplitude and / or phase) to a signal or antenna (e.g., to change the amplitude and / or phase of a transmitted signal), for example, based on the channel quality between the UE and the BS or network node.

[0037] In addition, in some cases, wireless networks may employ coordinated joint transmission, which may include (e.g., simultaneous) transmission of data or signals from multiple transmitters (e.g., from multiple network nodes) to the same receiver device (e.g., UE). A non-limiting example of coordinated joint transmission may include joint transmission coordinated multi-point (JT-COMP). For example, in the case of coherent joint transmission, the network may have knowledge of the properties of the corresponding channel between the receiver device and each transmitter. This channel knowledge may be provided to the transmitter or network, for example, based on CSI measurement reports sent by the UE (or receiver device) to each transmitter (BS or other network node). A precoder (e.g., provided at a BS, a central unit (CU), or other network node or other location) may estimate precoding weights to be applied by each transmitter (BS or network node) for the coordinated joint transmission, for example, to increase the SINR or performance of the jointly transmitted signal received at the receiver device while reducing interference at other locations. Thus, for example, precoding weights may be designed by a precoder and provided to each transmitter or network node such that, for example, constructive superposition of transmitted signals at a receiver (or UE) may improve the SINR of the signals and reduce interference.

[0038] However, for cooperative transmission, such as cooperative joint transmission (e.g., such as Joint Transmission Coordinated Multipoint (JT-COMP)), performance degradation may occur, at least in some cases, due to asynchronization of the amplitude, phase, and / or timing of the transmitted signals between the transmitters. For example, in order to provide constructive superposition of signals at a receiver (and thus improve SINR or other performance metrics), and to provide destructive superposition elsewhere, the amplitude, phase, and / or timing of the signals at the receiver should be synchronized.

[0039] However, the equipment (or electronic devices) of the wireless transmitter (e.g., of a UE, BS, or other network node) may have various performance limitations or defects, which may reduce or limit the transmission performance, either for a single transmitter, and / or for the case of multiple cooperating transmitters (e.g., cooperative joint transmission). For example, parasitic effects may cause performance degradation in many cases. Parasitic effects can be based on parasitic capacitance or stray capacitance, which causes unwanted capacitance between components (e.g., conductors) of an electronic device or integrated circuit due to the close proximity of the conductors. For example, although not designed as capacitors, there can typically be a non-zero capacitance between two conductors of an electronic circuit or device. Parasitic effects may be particularly problematic at higher frequencies. For example, parasitic effects or parasitic capacitance may reduce performance by causing, for example, radio frequency (RF) local oscillator (LO) frequency drift, LO phase noise, time synchronization errors, channel estimation errors, CSI quantization errors, CSI prediction errors, and / or other errors. Thus, for example, parasitic effects at one or more transmitters (e.g., a BS, a transmitter receive point (TRP), a relay node, or other network node) may cause a lack of synchronization between the transmitters in terms of amplitude, phase, and / or timing of signals received at a receiver or UE as part of a coordinated joint transmission. Parasitic effects are just one example of errors, problems, or inaccuracies that may arise in wireless signal transmission or with a transmitter, and other problems may also arise.

[0040] Thus, according to example embodiments, precoding weights may be determined for transmissions from one or more network nodes (e.g., by a precoder or by a controller or central unit) to provide a predetermined signal at a reference node (e.g., which may be a UE, user equipment, or other node). The predetermined signal may be any signal having predetermined (or known) properties. For example, the predetermined signal may be, for example, a notch signal having an amplitude less than a first threshold for one or more subcarriers; or a peak signal having an amplitude greater than a second threshold for one or more subcarriers. Thus, a notch signal or a peak signal are examples of a predetermined signal that may be detected by the reference node. For example, the precoding weights for at least one network node (e.g., as part of a coordinated joint transmission from a plurality of network nodes) may be based on channel properties of a respective channel between the reference node and each network node participating in the coordinated joint transmission (e.g., based on CSI measurement reports from the reference node).

[0041] Thus, for example, each network node may transmit a precoded tracking signal (e.g., based on a precoding weight designed to provide a predetermined signal at a reference node or reference point based on the corresponding channel). The reference node may track the predetermined signal (e.g., a notch signal or a peak signal) by determining whether the predetermined signal is present (or has been detected) at the tracking node. Thus, the precoding weights may be designed, for example, by a precoder or a central unit (CU) or a controller based on the corresponding channel properties so as to provide (e.g., based on a superposition of the transmitted signal) the predetermined signal (e.g., a notch signal or a peak signal) at the reference node. In an example embodiment, the reference node may determine whether the received signal (e.g., which may be a signal based on a superposition of signals received from multiple network nodes for cooperative joint transmission) is the predetermined signal. Thus, if the predetermined signal is a notch signal, the reference node may determine whether the received signal has an amplitude less than a first threshold.

[0042] However, according to example embodiments, at least in some cases, if precoding performance is poor, for example, if a received signal (having precoding weights designed to provide a predetermined signal) is not the predetermined signal, this may (at least in some cases) be due to (or result from) parasitic effects or other inaccuracies at one or more network nodes participating in the transmission (e.g., participating in a coordinated joint transmission from multiple network nodes). Thus, for example, adjustments to transmission parameters may be performed at one or more network nodes, and then the reference node may determine whether a subsequent received signal is the predetermined signal. This process may be repeated until the predetermined signal is ultimately received at the reference node. The adjustments to the network node transmission parameters (e.g., between initial transmissions based on channel conditions or channel reports until the predetermined signal is detected by the reference node) may be due to or result from parasitic effects or other inaccuracies at one or more network nodes. Thus, these adjustments to the transmission parameters performed by the network node during this process may be used by the network node when transmitting to one or more UEs in a cell or coordinated area, for example, to improve transmission performance.

[0043] According to an example embodiment, in order to provide information or an indication of whether the predetermined signal is received, the reference node may then send a message to one or more network nodes (and / or to a precoder, a central unit, or a controller that may determine precoding weights for one or more network nodes) regarding whether the predetermined signal is received by the reference node. For example, the message may include information such as: an indication of whether the predetermined (e.g., notch) signal is received; (measured) signal parameters, such as, for example, an amplitude, phase, and / or delay or timing of the signal received by the reference node (e.g., if the amplitude on one or more specific subcarriers is greater than or equal to a first threshold, it will indicate that the notch signal is not received, and if the amplitude of the received signal is less than the first threshold, it will indicate that the notch signal is received); a signal parameter of at least one multipath component (MPC) of the signal received by the reference node associated with (e.g., transmitted from) at least one network node, including at least one of the following: amplitude, phase, or delay; a delta or difference between corresponding signal parameters of the strongest multipath components of multiple network nodes (e.g., a difference in amplitude of two signals or MPCs received from two different network nodes as part of a coordinated joint transmission, or a difference in phase of two signals or MPCs received from two different network nodes, or a difference or delta between the timing or delay of two signals or two MPCs received from two different network nodes of a coordinated joint transmission); and / or a suggested change or suggested adjustment to one or more precoding weights estimated to more accurately provide a predetermined signal at a reference node.

[0044] In an example embodiment, (multiple) network nodes and / or precoders or a central unit may receive the message and may then adjust one or more transmission parameters for one or more network nodes for a second cooperative joint transmission. For example, the network node or precoder (or central unit) may adjust (e.g., based on the received message) one or more transmission parameters for one or more network nodes by, for example, adjusting at least one of the precoding weights (each of which may include amplitude and / or phase) or local oscillator (LO) frequency of the one or more network nodes to move or adjust the position of the predetermined signal. The network node may then send a second signal (a second cooperative joint transmission) based on the adjusted transmission parameters (e.g., based on the adjusted LO frequency and / or adjusted precoding weights designed to more accurately provide a predetermined (e.g., notch or peak) signal at the reference node), including a second precoded tracking signal from each network node. For example, the reference node may receive the second signal based on the second precoded tracking signal from each network node and may determine whether the second signal is the predetermined signal (e.g., a notch or peak signal). If the predetermined signal (eg, notch signal or peak signal) is not received at the reference node, the reference node may send a message to the controller and / or one or more network nodes indicating that the predetermined signal is received or detected by the reference node.

[0045] In example embodiments, at least in some cases, adjustment (or adaptation) of one or more transmission parameters may provide (or may be associated with) an indication of parasitic effects or other errors or inaccuracies of the network node(s). Thus, in example embodiments, based on the adjusted transmission parameters, or based on the amount of adjustment performed at the network node (e.g., based on adjustment of the LO frequency, and / or change or adjustment (e.g., adjustment of amplitude and / or phase) to one or more precoding weights), for example, at least in some cases, one or more network nodes may transmit data to the reference node or to other UEs in the cell or cooperative area (e.g., to UEs that may be near or proximate to the reference node), which may accommodate or compensate for at least some portion of the parasitic effects (or other issues or inaccuracies) of the network node.

[0046] Thus, in an example embodiment, from the perspective of a network node, a method may be performed, the method comprising: determining, by the network node within a wireless network, estimated precoding weights estimated to provide a predetermined signal (e.g., which may be a notch signal, a peak signal, or other predetermined signal) at a reference node for signal transmission from at least the network node based at least on a channel state information (CSI) measurement report received from the reference node; sending, by the network node, a first precoded tracking signal to the reference node based on the estimated precoding weights (the first precoded tracking signal from the network node may be one of precoded tracking signals that may be transmitted by multiple network nodes as part of a coordinated joint transmission that may be designed to provide the predetermined signal at the reference node); receiving, by the network node, a message from the reference node comprising information regarding whether the predetermined signal was received at the reference node based at least in part on the first precoded tracking signal sent by the network node; the network node may adjust one or more transmission parameters of the network node (e.g., LO frequency and / or precoding weights) that were estimated to more accurately provide the predetermined signal at the reference node; and sending, by the network node, a second precoded tracking signal based on the adjusted transmission parameters.

[0047] According to an example embodiment, the network node may adjust a transmission parameter based on control information received from another node (e.g., an indication of a precoding weight adjustment or LO frequency adjustment for the network node), such as a DU (distributed unit), another BS or TRP, a controller, a precoder, or other node that may participate in or control the calculation or determination of precoding weights for cooperative joint transmission. In an example embodiment, the adjustment of the transmission parameter of the network node may include, for example, adjusting the amplitude and / or phase of at least one precoding weight of the network node; adjusting the transmission delay or transmission timing of the network node; or adjusting or tuning the frequency of a local oscillator of the network node.

[0048] According to an example embodiment, a message relating to whether a predetermined signal is received at a reference node may include measured signal parameter information, an indication of whether the predetermined signal is received, and / or a recommended adjustment to one or more transmission parameters of one or more network nodes. Thus, for example, the message may include information such as one or more of the following: an amplitude of a signal received by the reference node based at least in part on a first precoded tracking signal transmitted by the network node; and an amplitude and phase of a signal received by the reference node based at least in part on the first precoded tracking signal transmitted by the network node; a signal parameter of a signal received by the reference node based at least in part on the first precoded tracking signal transmitted by the network node, the signal parameter comprising at least one of the following: amplitude, phase, or delay of at least one multipath component associated with the network node; a strongest signal of a plurality of network nodes; a difference between corresponding signal parameters of the multipath components; an indication of whether a notch signal is received at the reference node based at least in part on a first precoded tracking signal sent by the network node, the notch signal having an amplitude less than a first threshold for one or more subcarriers; an indication of whether a peak signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, the peak signal having an amplitude greater than a second threshold for one or more subcarriers; or a suggested change or adjustment to one or more precoding weights that are estimated to more accurately provide a predetermined signal at the reference node.

[0049] According to another example embodiment, for example, from the perspective of a reference node, a method may be performed, the method comprising: receiving, by the reference node, a first signal based at least in part on a first precoded tracking signal received by the reference node from at least one network node; determining, by the reference node, whether the first signal is a predetermined signal; sending, by the reference node, a message to at least one network node regarding whether the predetermined signal was received at the reference node; and if the predetermined signal was not received at the reference node, receiving, by the reference node, a second signal based at least in part on an adjusted transmission parameter for the at least one network node, the adjusted transmission parameter being adjusted in response to the message. Further illustrative examples and example embodiments will now be described.

[0050] Figure 2is a diagram of a system according to an example embodiment in which a reference node can track precoding performance from one or more network nodes and provide feedback regarding the precoding performance. According to an example embodiment, any error in precoding performance (e.g., any difference between a signal actually received at a reference node and an expected predetermined signal) may be at least partially, or at least in some cases, due to parasitic effects or other errors or inaccuracies at one or more network nodes. Thus, to improve signal transmission performance, feedback regarding precoding performance (e.g., providing information regarding whether a predetermined signal was detected at the reference node based on a received signal and an expected predetermined signal, or signal parameter information, or suggested transmission parameter adjustments) can be provided from the reference node to the controller 202, for example, to allow the controller to adjust one or more transmission parameters (such as the LO frequency and / or one or more precoding weights of the network node), for example, to compensate for such parasitic effects, errors, or inaccuracies that may be present at one or more network nodes. Thus, in this manner, for example, the reference node can track (or detect the presence of) a predetermined signal (e.g., a notch signal or a peak signal, or other predetermined signal) based on a precoding tracking signal sent by one or more network nodes (e.g., multiple collaborative joint transmissions), and can provide feedback on precoding performance (e.g., providing feedback to (multiple) network nodes and / or controller 202 on whether the predetermined signal is received or detected at the reference node).

[0051] like Figure 2As shown, for example, a controller 202 (e.g., which may be located in the cloud, or at (or as part of) a BS, AP, gNB, a central unit (CU) of a distributed base station, a core network or network node, or other location) may be connected to or in communication with one or more network nodes, such as network nodes 210, 220, and 230. For example, each network node may be a transmitter receiver point (TRP), a distributed unit (DU) of a split or distributed base station, a BS, a gNB, a remote radio head (RRH), a relay node, a RAN node, or other network node. One or more reference nodes (such as reference nodes 250 and / or 260) may be provided to determine or measure the precoding performance of controller 202 and / or the network nodes, for example, based on determining whether a predetermined signal is received or detected by the reference node and / or by measuring one or more signal parameters of the received signal. Each network node may include a local oscillator (LO), including LO1 for network node 210, LO2 for network node 220, and LO3 for network node 230. Feedback on precoding performance may be provided, for example, by the reference node(s) sending a message regarding whether a predetermined signal is received or detected by the reference node(s) to one or more network nodes and / or the controller 202. Each network node may perform both, for example, based on one or more precoding weights and beamforming.

[0052] According to an example embodiment, each (or one or more) of network nodes 210, 220, and / or 230 may receive CSI measurement reports from each of one or more reference nodes 250, 260 (and possibly also from a UE). For example, reference node 250 may receive a CSI-RS signal from network node 210 and a CSI-RS signal from network node 220. Based on the CSI-RS signal from network node 210, reference node 250 may send a CSI measurement report to network node 210 (e.g., to indicate a channel or channel properties between reference node 250 and network node 210). Similarly, network node 210 may also send a CSI measurement report to network node 220, e.g., to indicate a channel or channel properties of a channel between reference node 250 and network node 220. In addition, reference node 260 may similarly receive CSI-RS signals from network nodes 220 and 230 and may send corresponding CSI measurement reports to network nodes 220 and 230. In an example embodiment, CSI reports or channel information may be sent from one or more network nodes to controller 202. Although operations for or with respect to reference nodes 250 and 260 may be the same or similar, operations with respect to reference node 250 will be described in more detail as an illustrative example.

[0053] Thus, according to an example embodiment, precoding weights may be determined by the controller 202 for signal transmissions from one or more network nodes, the precoding weights being estimated (e.g., by the controller 202) to provide a predetermined signal at a reference node (e.g., which may be a UE, user equipment, or other node). The predetermined signal may be, for example, a notch signal or a peak signal or other signal. In an example embodiment, the controller 202 may determine the precoding weights for a coordinated joint transmission of multiple network nodes, e.g., where the precoded tracking signals transmitted by each network node are estimated to provide the predetermined signal at the reference node (e.g., via a superposition of received signals at the reference node).

[0054] Thus, for example, as part of a coordinated joint transmission to a reference node, network node 210 may transmit a precoding tracking signal 212 to reference node 250, and network node 220 may transmit a precoding tracking signal 222 to reference node 250, based on precoding weights provided by controller 202. Reference node 250 may measure or determine the precoding performance of controller 202 or the network node based on the received signal at the reference node. If the predetermined signal is received at reference node 250, this may indicate that the precoder is performing well. However, according to example embodiments, at least in some cases, if the precoding performance is poor, for example, if the received signal (which has been transmitted based on precoding weights designed to provide the predetermined signal) is not the predetermined signal, this may (at least in some cases) be due to (or result from) parasitic effects, errors, or other inaccuracies at one or more network nodes participating in the (e.g., coordinated joint) transmission. Thus, for example, the reference node may send a message to the controller 202 via line (or communication link) 270 (and similarly, the reference node 260 may send a message to the controller 202 via line or communication link 280) that provides feedback regarding the precoding performance determined by the reference node 250, such as including information regarding whether a predetermined signal was received by the reference node 250. The message may include different types of information related to precoding feedback and / or whether a predetermined (e.g., notch or peak) signal was received.

[0055] According to an example embodiment, as described above, reference node 250 may send a message to one or more of network nodes 210 and 220 regarding whether a predetermined signal is received by the reference node, which message may then be forwarded to controller 202. For example, the message may include information such as: an indication as to whether a predetermined (e.g., notch) signal is received; (measured) signal parameters, e.g., indicative of the amplitude, phase, and / or delay or timing of the signal received by the reference node (e.g., where the amplitude on one or more specific subcarriers is greater than or equal to a first threshold, it will indicate that the notch signal is not received, and where the amplitude of the received signal is less than the first threshold, it will indicate that the notch signal is received); signal parameters of at least one multipath component (MPC) of the signal received by the reference node associated with (e.g., transmitted from) at least one network node, including At least one of: amplitude, phase, or delay; a delta or difference between corresponding signal parameters of the strongest multipath components of a plurality of network nodes (e.g., a difference in amplitude of two signals or MPCs received from two different network nodes as part of a coordinated joint transmission, or a difference in phase of two signals or MPCs received from two different network nodes, or a difference or delta between timing or delay of two signals or two MPCs received from two different network nodes of a coordinated joint transmission); and / or a proposed change or proposed adjustment to one or more precoding weights that are estimated to more accurately provide a predetermined signal at a reference node.

[0056] Based on the feedback received from the reference node 250 (e.g., based on the above-mentioned message), the controller 202 and / or the network node 210 or 220 may determine adjustments to be made to one or more transmission parameters at one or more of the network nodes 210, 220 to improve precoder performance and / or to be estimated to more accurately provide a predetermined signal at the reference node 250. As an example, the controller 202 may then provide or indicate the modified or updated one or more transmission parameters (e.g., an updated LO frequency and / or one or more updated precoding weights for at least one network node) to the network node 210 via line 203A, to the network node 220 via line 203B, and / or to the network node 230 via line 203C. Thus, in this example, network node 210 and / or network node 220 will apply adjusted transmission parameters, which may include an adjusted LO frequency (e.g., an adjusted LO frequency of LO1 of network node 210 and / or an adjusted LO frequency of network node 220) and / or adjusted precoding weight(s) for one or both of network nodes 210, 220. The network nodes may then transmit a second or additional joint cooperation signal to reference node 250 by each network node transmitting a second precoded tracking signal based on the adjusted transmission parameters. This process may be repeated, wherein reference node 250 may determine whether the predetermined signal was received and then send a message or feedback to one or more network nodes or a controller to allow further adjustment of one or more transmission parameters at one or more network nodes, for example, to more accurately provide the predetermined signal at the reference node.

[0057] Reference again Figure 2 , there are multiple (e.g., three in this example) different RF LOs, so each LO may have its own phase noise and frequency drift. If the parasitic effects are large, the performance of the JT CoMP precoder will degrade, possibly even severely. To track any precoding degradation, the reference node (or tracking receiver) observes (or detects) the transmission results caused by the predefined JT cooperation area wide JT CoMP precoder (e.g., provided at the controller 202), for example, which ideally generates a notch signal at each reference node 250, 260 (e.g., at each tracking receiver location, or at each reference point).

[0058] According to example embodiments, such notched signals may be sensitive to any parasitic effects and may therefore be a good indicator of any parasitic effects that degrade JT CoMP performance. To correct (or compensate for) such undesirable effects, the reference nodes 250, 260 (or tracking receivers) send or transmit feedback related to the (e.g., JT-CoMP) precoding performance (e.g., precoding performance of the coordinated joint transmission) of signals transmitted from one or more network nodes.

[0059] refer to Figure 2 In an example embodiment, a machine learning (ML) instance or model (208), or an artificial intelligence (AI) neural network (which may be referred to as an AI model, a neural network model, or an ML model) may be provided to determine (or even optimize) transmission parameters or transmission parameter adjustments that should be performed for one or more of the network nodes 210, 220 based on precoding performance feedback or message(s) received from the network nodes in order to more accurately provide a predetermined (e.g., notched) signal at the reference node (and thereby provide transmission parameters that may be used for data transmission, which may compensate for parasitic effects, inaccuracies, or errors at the network node transmitter).

[0060] Thus, ML instance 208 may be or may include a machine learning (ML) algorithm. An ML algorithm may be, for example, a computer-implemented algorithm or logic (which may be hardware and / or software) that builds or generates a model (e.g., a computational model) based on sample data (referred to as "training data") in order to make predictions or decisions (e.g., adjusting transmission parameters to more accurately provide a predetermined signal at a reference node, as an illustrative example). An ML algorithm may also be referred to as an artificial intelligence (AI) neural network, a neural network model, an AI neural network model, an AI model, etc.

[0061] According to example embodiments, an ML algorithm or neural network may include a model, such as a computational model composed of nodes organized in layers. A node may also be referred to as an artificial neuron, or simply a neuron, and performs a function on a provided input to produce a certain output value. A neural network may require a training period to learn parameters, such as weights, for mapping inputs to desired outputs. The mapping occurs via a function. Weights may be used for the mapping function of the neural network. Each AI (or neural network) model can be trained for a specific task (e.g., for determining or adjusting one or more transmission parameters).

[0062] For example, the ML instance 208 may first be trained using a particular JT-COMP signal that will result in a predetermined signal being in a different location, or having different properties, and then, after feedback, the ML instance may be trained to know that a particular transmission parameter adjustment (e.g., a particular adjustment to the LO frequency and / or precoding weights) will result in a particular improvement or change in the predetermined signal location.

[0063] Figure 3 is a diagram illustrating the operation of a network according to an example embodiment. Figure 3 As shown, a reference (or tracking) node 250 can communicate with a set of network nodes 210, 220 (as an illustrative example). At 310, each network node 210, 220 transmits a CS-RS (reference signal) to the reference node 250. At 312, the reference node sends a CSI measurement report to each network node (or TRP) 210, 220. At 313, the network node (which, at least in some embodiments, can be assisted by the controller 202) can determine precoding weights based on the CSI measurement reports and, accordingly, can precode data for transmission to the UE and can precode a predetermined (e.g., notch) signal based on a set of precoding weights. At 316, the network node can transmit a JT-COMP signal by each network node sending a precoded tracking signal designed to provide the predetermined (e.g., notch) signal at the reference node 250. At 318, the reference node 250 can measure or determine whether the predetermined (e.g., notch) signal is received. Alternatively, at 318, the reference node may create or simulate a received signal based solely on the strongest MPC from each network node (e.g., based on the superposition of the strongest or largest magnitude MPC from each network node involved in the JT-COMP transmission to the reference node 250). At 320, feedback, such as a message related to a predetermined (e.g., notched) signal, is sent by the reference node 250 to one or more network nodes and / or to the controller 202, for example, to provide information related to parasitic effects (or other errors or inaccuracies of one or more network nodes). At 322, one or more network nodes (and / or the controller 202) may adjust one or more transmission parameters of one or more of the network nodes 210, 220 (e.g., adjusting the LO frequency and / or one or more precoding weights). At 324, the transmission parameter adjustments of the network node 210 may be performed for both the notched (or predetermined) signal transmission to the reference node and for data transmission from the network node(s) to the UE. In this manner, precoding performance feedback or information regarding whether a predetermined signal (e.g., a notched signal) is received at a reference node can be used to make adjustments (e.g., adjusting the LO frequency and / or adjusting one or more precoding weights) at one or more network nodes, for example, to accommodate parasitic effects, errors, or inaccuracies in performance at one or more network nodes. In this manner, signal transmission performance can be improved.

[0064] According to example embodiments, the controller 202 and / or a plurality of network nodes (e.g., TRP, BS, ...) may, for example, periodically or even continuously perform or transmit a coordinated joint transmission (e.g., JT COMP), wherein a set of JT-COMP precoding weights is provided to and applied by a set of network nodes (e.g., network nodes 210, 220, ...) that are designed to provide a predetermined signal (e.g., a notch signal, a peak signal, or other signal with known or predetermined properties) at a reference node 250 or reference point. For example, in order to provide a notch signal, such as a signal having an amplitude (with respect to a subcarrier frequency) less than a threshold (e.g., which may be zero power in some cases), the multiple signals need to be of the same amplitude and out of phase so as to provide destructive superposition at the reference node 250 or reference point. For example, any variation in amplitude, phase (or frequency), and / or timing may affect the superposition, thereby causing the signal at the reference node or reference point to be above the threshold (and therefore not the predetermined notch signal), wherein such variation may, at least in some cases, be attributable to parasitic effects of one or more network nodes.

[0065] Thus, adjustments to the LO frequency and / or precoding weights (in response to feedback from a reference node or tracking station) that result in a predetermined signal being more accurately provided, generated, or generated at a reference node or reference point (or even calculated or simulated based on the strongest MPC from multiple network nodes) can be used and applied by the network node to compensate for such parasitic effects and perform data transmission to UEs within the cell or cooperative area. In this way, signal transmission performance can be improved. To provide such operation, one or more reference (e.g., tracking nodes) can be provided within the cell or cooperative area, where each reference (tracking) node can have a communication (e.g., wired or wireless) link back to one or more network nodes and / or controller 202 to provide feedback. For example, the reference node can be implemented as a user equipment or UE, or other node, and can be a mobile node, or can be a node with a fixed location. For feedback, the reference node can have a fast backhaul connection, for example, via a wired or air / wireless PUCCH (Physical Uplink Control Channel) connection to the gNB / network node precoder or to the central unit (or controller 202) of the cooperation area, so that a shorter round-trip time can be achieved. Based on the reported precoding performance results for multiple reference (tracking) node locations, the controller 202 or central unit, at least in some cases and / or for some example implementations, can estimate the root cause of precoding errors such as relative RF-LO phase noise offset, frequency offset, transmission timing delay, etc. based on the feedback from the network nodes. Based on this feedback, the cooperation area precoder (e.g., controller 202) can then be re-tuned for one or more network nodes to offset these parasitic effects, for example, by re-tuning one or more RF oscillators, changing precoding weights, etc.

[0066] In an example embodiment, in order to find the best reaction or response (or action) to the observed precoding error (e.g., the best or optimal adjustment of the LO frequency and / or precoding weights of the network node) (e.g., based on specific feedback from the reference node(s), a root cause analysis may be performed by the controller 202, e.g., relying on a machine learning (ML) algorithm, e.g., which may be provided by the ML instance 207. Thus, for example, the ML instance (or AI neural network) may predict the impact of parasitic effects on other active UEs in the cooperation area based on feedback from one or more reference nodes.

[0067] refer to Figure 2For example, each cell or each site may have only one RF local oscillator (LO), so that all beams of the site are affected by the same parasitic effects of the LO. Assuming a maximum size of the cooperation area of three sites, the number of tracking parameters will be very limited, such as phase (frequency) deviation and delay per site, which equals six or nine parameters.

[0068] Figure 4 is a diagram illustrating an antenna system 408 including a plurality of antenna elements in which JT-COMP precoding weights have been designed or provided, e.g., estimated to provide a predetermined signal (e.g., a notched signal) at a center antenna element 410 of a reference node 250. The center antenna element 410 is an example, and any reference point or any antenna element may be used as a reference point for providing precoding weights estimated to provide a notched signal at the reference point. In this example, 17 antenna elements are provided in the antenna system, including the center antenna element 410, 4 antenna elements for an inner ring 412 of antenna elements, and 13 antenna elements provided for an outer ring 414 of antenna elements. Very suitable as part of a tracking receiver or reference node is a method according to Figure 4 Receive (Rx) antenna arrangement, Figure 4 The diagram illustrates an example spatial structure of a notched signal generated, for example, from four cooperating transmission stations (four network nodes as part of a coordinated joint transmission) in this case. In this example, precoding weights are applied at the network node, which are estimated to provide a notched signal at the center antenna element 410 (as an example reference point, but other reference points can be used). Thus, for example, to provide improved signal or notch tracking, the reference node 250 can include one or even two antenna element rings (e.g., 412, 414) next to the center antenna element 410 at the exact location of the expected notch signal, which can allow for complete reconstruction of a spatial field close to the ideal notch. This has two benefits: first, for an ideal notch, at least in some circumstances or scenarios, the received signal will be zero or approximately zero and can therefore be masked by receive (Rx) noise and interference.

[0069] By tracking the received signal near the expected location (e.g., the center antenna element 410) to receive the notched signal, the antenna system of the reference node 250 can reconstruct or determine the ideal notch location. A second aspect is that based on tracking the notched signal or the predetermined signal at multiple locations (e.g., at different antenna elements of the antenna system and / or detecting the signal at different network nodes sent from the JT-COMP), different root causes of certain received signal deviations can be detected or determined. For example, each reference node can detect the signal parameters (e.g., amplitude, phase, timing) of the signal received at each of the multiple antenna elements (e.g., for the signal received at the center element 410, and for the signals received at one or more other antenna elements at the reference node 450). The reference node 250 can then provide this signal information for one or more antenna elements as feedback to the network node or controller 202. Alternatively, the reference node 250 can calculate the strongest (e.g., highest amplitude) multipath component (MPC) of the signal received from each network node (or for each network node) at the reference point (e.g., the center antenna element 410). These signal parameters for each MPC (or each network node, for the strongest MPC) can be reported to the network node or controller 202. Alternatively, the reference node can calculate the difference or delta between the corresponding signal parameters of the (e.g., strongest) MPCs of different network nodes (e.g., the amplitude difference of the MPCs received from network node 210 and network node 220, the amplitude difference received from different network nodes, or the timing difference of the MPCs of different network nodes). These deltas or differences can be reported to the network node and / or controller and can be used by, for example, the controller 202 and / or the ML instance 208 to determine the root cause of the precoding error and / or improve the actions or adjustments made to the LO frequency and / or precoding weights in response to a particular signal received by the reference node. This precoding performance feedback information can be fed back or transmitted from each or one or more of the reference nodes 250, 260, etc. to the network node and / or controller 202, for example, so that the controller and / or network node can adjust one or more transmission parameters to more accurately provide a predetermined (e.g., notched) signal at the reference node(s) or reference location(s). Furthermore, such transmission parameter adjustments (based on feedback) performed by one or more network nodes 210, 220, etc. may also be used to compensate for parasitic effects on data or signal transmissions to one or more UEs (eg, UE1, UE2) in a cell or cooperation area.

[0070] Furthermore, according to example embodiments, one or more of the reference nodes 410 (or tracking receivers) may be at fixed (and / or known) locations, for example, because it may be useful to separate the temporal variance of the radio channel itself from parasitic effects of the network node transmitter. According to example embodiments, the system (e.g., controller 202 and / or reference nodes) may determine which network node / gNB (e.g., RF LO or precoding weights) parasitic effect(s) are causing a change or degradation in precoder performance for a particular precoder. Observations of the spatial field surrounding the notched signal (e.g., measurements of signals from one or more antenna elements of the reference node) may then provide inferences, such as that time-varying reflections of the radio channel from a certain direction will have different effects on a number of Rx antennas, which then, combined with phase deviations of the gNB / network node LOS (line-of-sight) link, may result in an alternative transmit position. Furthermore, in some cases, machine learning (ML) may be used to perform inferences on the combined received signal (e.g., ML instance 208 may determine transmission parameter adjustments based on feedback from one or more reference nodes). Furthermore, a specific training phase for the ML instance 208 can be performed, for example, where the gNB / network node sequentially transmits certain sets of deviations regarding LO phase, frequency, and / or tx (transmit) time. Thus, the ML instance 208 can learn how and / or which transmission parameters (or transmission parameter adjustments, such as to LO frequency and / or precoding weights) affect the overall spatial structure around the notched signal, including, for example, how various adjustments to LO frequency and / or precoding weights affect one or more signal parameters received at one or more antenna elements (e.g., amplitude, phase, and timing, or MPC amplitude, phase, and / or timing). In another example embodiment, the ML instance can be provided at one or more network nodes, at one or more reference nodes, or both. If located at the gNB, the reference node (or tracking receiver) can typically report received signals from one or more Rx antennas, or even all Rx antennas.

[0071] According to an example embodiment, precoding performance feedback can be provided from multiple reference nodes (or tracking receivers). The controller or network node and / or ML instance 208 can combine the feedback from all or multiple reference nodes to infer or determine the transmission parameter adjustment of the network node, for example, to obtain a more reliable inference or a more reliable or accurate transmission parameter adjustment to correct or compensate for the parasitic effects of each network node (e.g., each BS or each TRP). The higher the number of reference nodes (or tracking receivers), the more helpful or accurate the ML instance 208 is in determining the characteristics of the parasitic effects of each network node (and the corresponding transmission parameter adjustment that can be used to compensate for the parasitic effects of each network node).

[0072] According to an example embodiment, assuming (as an illustrative example) three transceivers (three network nodes or TRPs), a specific tracking mode frame may be defined and transmitted, such as: i) sequentially transmitting tracking (precoded) signals (TRs) transmitted from stations (network nodes / TRPs) 1, 2, and 3, respectively. 1,2,3 ), then sending a joint transmission, ii) precoded signal TR1 (from network node 1), plus TR2 (from network node 2), then TR1 plus TR3, and finally iii) a joint transmission of TR1, TR2, and TR3 (from network nodes 1-3, respectively). In this way, relative parameter deviations (e.g., between network nodes / TRPs) are compared and the network node / TRP with the strongest phase drift of the LO is determined, for example. It may be necessary to measure parasitic effects and compensate for them, and in this way, the system (e.g., controller 202 and / or network nodes) may be able to determine which network node(s) / TRPs may be causing the problem or deviating frequency, phase, or time delay, for example, so that a notched signal does not appear at a reference point or reference node.

[0073] In one embodiment, the reference node may track a notch (or other predetermined) signal for only the strongest or direct LOS path of the multipath components (e.g., the strongest MPC from each network node) including the channel components, while the reflected multipath components (which may typically be delayed and have lower amplitudes) are suppressed (ignored or filtered by the reference node in the calculation to determine whether the predetermined signal is provided at the reference node). To determine the strongest MPC for the signal received from each network node, a signal profile may be used, which may provide accurate parameter estimates for all relevant multipath components, such as the delay τ of the time domain channel impulse response, for example. i , amplitude α i and phase This can be helpful in time-varying radio channels, where typically only the LOS path is stable, while the reflected multipath components (e.g., having lower amplitude than the LOS MPC) typically fluctuate.

[0074] Figure 5 is a diagram illustrating the strongest multipath components (MPCs) from multiple network nodes or TRPs. i Several MPCs are shown. Figure 5 The strongest MPC 512 (among the multiple MPCs) from TRP1 and the strongest MPC 512 from TRP2 are shown. iThe strongest MPC 514 of the network node / TRP is determined by the reference node 250. In an example embodiment, in a first step, all TRPs transmit their tracking reference signals - or CSI-RS - simultaneously on orthogonal resource elements. Based on these reference signals, the reference node 250 (or tracking receiver) calculates the summary time-domain channel impulse response (CIR) for each channel component and identifies the parameters of the strongest multipath component (e.g., see strongest MPC 512, 514). By combining these strongest multipath components, for example, by the reference node 250 superimposing a simulation of such strongest MPC from each network node / TRP into a virtual Rx signal - or by adding the signal of each TRP into a common Rx signal, the network node can perform notch signal tracking for only these strongest MPCs. Note that the CSI reporting for notch precoding can also take into account only the strongest multipath components (MPCs).

[0075] In this way, notches (notch signals) can be tracked on multiple predefined subcarriers at certain predefined physical resource blocks (PRBs) (for example, detecting whether a notch is present at a reference point and / or whether a notch is present at other locations outside the reference point (such as another antenna element)). In a special case, this may include all subcarriers, thereby providing corresponding noise reduction and accuracy gains, but overhead must also be considered. As an illustrative example, notch signals can be generated for three reference nodes (or tracking receivers) at three spatial locations (reference points) in the cooperation area, and such notches are sent at each TTI or PRB of 168 resource elements and every tenth PRB in 100 PRBs (=20MHz bandwidth). In such an example, the associated tracking overhead is about 0.2%. This allows accurate tracking every millisecond, so that phase slope changes of up to about 0.1 to 1KHz can be ideally tracked.

[0076] In another embodiment, instead of using a specific fixed reference node (or tracking transceiver), a network node (TRP or gNB) can identify a suitable UE from the currently active UEs in the cooperation area as a reference node or tracking transceiver. For example, a suitable UE can be one with low mobility, good LOS connectivity with one or more (or all) network nodes, etc. This has the advantage that no specific pre-installation of a reference node (or tracking transceiver) is required.

[0077] In example embodiments, network nodes (e.g., gNB, TRP) and UEs may generally include beamforming gain as far as possible (e.g., applying beamforming at both the transmitter and receiver) with the goal of minimizing resource usage and maximizing tracked SINR, but this may be partially included in the precoder calculation.

[0078] Figure 61 is a diagram illustrating one or more reference nodes that transmit wide-beam phase tracking reference signals to one or more user equipment / UEs according to an example embodiment. A UE may typically receive PTRS from one or more BSs, and the UE may detect the phase rotation of the received signal, and the UE may correct the phase rotation. Thus, the PTRS may be used by the UE for phase correction (the phase rotation on the transmitted PTRS may be detected) for demodulation (DL demodulation). The UE may adjust its phase for DL (downlink) demodulation based on the received PTRS. In a typical case, a BS or cell may typically transmit a phase tracking reference signal (PTRS) to a UE via each of multiple (e.g., 32) beams using beam sweeping, which may create a large signaling overhead for the BS, for example, to provide PTRS to a group of UEs within (multiple) cells. For example, PTRS may typically be transmitted by a BS via each of multiple beams to obtain beamforming gain, thereby allowing the PTR to fully reach UEs even far from the BS, or UEs at the cell edge. However, requiring the BS to transmit beam PTRS via each of the multiple beams may generate significant signaling overhead for the BS.

[0079] Thus, according to example embodiments, one or more reference nodes (250, 260) may be provided and may be in proximity to one or more UEs (e.g., UE1, UE2). Thus, according to example embodiments, instead of (or in lieu of) a BS / network node transmitting PTRS (or in addition to the BS transmitting PTRS), reference nodes 250 and / or 260 may transmit PTRS. For example, one or more reference nodes may transmit PTRS via a wide beam (a transmit beam wider than the beamwidth used by the BS to transmit PTRS) or via an omnidirectional antenna (e.g., the reference node does not use a directional beam to transmit PTRS). For example, an omnidirectional antenna (e.g., no transmit beam) or a wide beam may be used by the reference node(s) to transmit PTRS because, for example, the reference node(s) may be near a group of one or more UEs to which the PTRS is directed. For example, reference nodes may be provided at different locations within a cell or a cooperation area so that PTRS may be transmitted by different reference nodes, thereby enabling all or many UEs to receive PTRS from the reference node (e.g., rather than from the BS(s)). In an example embodiment, the subcarriers used to transmit PTRS may be fixed or established by a standard or a core network, but the carrier frequency used to transmit PTRS may vary.

[0080] about Figure 6In a first illustrative example, two (or more) reference nodes 250, 260 may transmit PTRS (via a wide or large beam, or omnidirectional transmission) on the same frequency band or carrier (e.g., 28 GHz). One or more reference nodes may transmit PTRS via a wide beam or via multiple wide beams (e.g., wider than a standard or typical beam used by a BS to transmit PTRS) and / or via fewer beams than the BS. Thus, by providing one or more reference nodes to transmit PTRS (e.g., via a wide or large beam, or via omnidirectional transmission), PTRS signaling overhead may be reduced (e.g., fewer beams may be required) and / or signaling overhead may be shifted to one or more reference nodes. In an example embodiment, as described above, an omnidirectional antenna may be used (e.g., rather than using a directional beam for transmission), for example, to allow a reference node to transmit in all directions with one PTRS transmission.

[0081] Different embodiments are possible. In a first example embodiment, the reference node within the cell or collaboration area may send PTRS only on a higher frequency band or higher carrier frequency (e.g., 28 GHz). Alternatively, in a second example embodiment, the reference node may send only on a lower frequency band or lower carrier frequency of 3.5 GHz, for example, to reach UEs that may be far away from the reference node. In a third example embodiment, a certain (some) reference node within the cell or collaboration area may send PTRS via a higher frequency band or higher carrier frequency (e.g., 28 GHz), while (multiple) other reference nodes may send PTRS via a lower frequency band or lower carrier (e.g., 3.5 GHz). Thus, the reference node may send PTRS on a higher frequency band (or higher carrier), on a lower frequency band (or higher carrier), or on both a higher frequency band and a lower frequency band within the cell or collaboration area. Now, some UEs may be farther away, so different frequency bands may also be used.

[0082] In an example embodiment, each reference node may receive an instruction (e.g., PTRS configuration) from a network node (or gNB or TRP) to transmit PTRS on behalf of the network node, and the signaling or control instruction may indicate the frequency band or carrier (e.g., higher frequency band, lower frequency band, or both) on which the reference node should transmit PTRS. For example, reference node 250 may receive an instruction from network node 210 to transmit PTRS via a lower frequency band, such as PTR_Lo 1,2,3 The reference node can also receive a control instruction from the network node 230 to send PTRS via a higher frequency band, such as PTR_Hi 1,2,3In an illustrative example, the reference node may be a UE, and the network node(s) may send control instructions or PTRS configurations to one or more UEs to configure the UEs to transmit PTRS signals on a default or understood frequency band (thus, without indicating a carrier band / bands for PTRS transmission), or to transmit PTRS signals on an indicated frequency band or carrier frequency.

[0083] In an example embodiment, for example, a reference node (e.g., 250) transmitting PTRS on a low frequency band (e.g., 3.5 GHz) or a non-standard frequency band may use a frequency divider to divide the frequency of the PTRS so that the low (or non-standard) frequency band (e.g., at 3.5 GHz) PTRS transmission will have the same phase as the standard PTRS signal that may be transmitted on a standard frequency band / carrier frequency of 28 GHz. Thus, as Figure 6 As shown in the example of , the reference node 250 can use a 1 / 8 divider to divide the 28 GHz PTRS carrier frequency down to a 3.5 GHz carrier frequency or band, for example, so that the phase of the PTRS at the receiving UE will be the same for both bands of PTRS. Thus, in the example embodiment, the PTRS transmitted by the reference node 250 via the lower carrier frequency of 3.5 GHz and the PTRS transmitted by the reference node 260 at the higher carrier frequency of 28 GHz will both provide the same phase information to the UE(s), even though transmitted via different carrier frequencies / bands.

[0084] Therefore, in an example embodiment, reference nodes or tracking stations (e.g., 250, 260) can transmit reference signals (such as PTRS) from a single site or multiple sites, which would otherwise have to be transmitted multiple times for multiple beams, with correspondingly large BS / network overhead. This is particularly relevant for higher FR2 frequency bands, where the number of beams can be high and time-domain beam scanning is required due to the limited coverage of this frequency without beamforming gain.

[0085] Figure 6 Two different approaches are indicated in FIG, where at the bottom, the reference node 260 (or tracking receiver) sends a signal for TRP TRP 1,2,3 Signal PTR_hi 1,2,3 .PTR_hi 1,2,3 Transmitted in the same RF band as conventional beam-based PTRS and directly coupled or derived from the corresponding LO of the TRP / network node. 1,2,3There may be similar coverage issues as transmitting directly from the TRP / network node. One option is to use some type of power boosting, or use single frequency network transmission from the reference node plus wide beam (or omnidirectional transmission) from the network node / TRP. In addition, the reference node may be closer to the UE.

[0086] Furthermore, in an example embodiment, down-conversion and up-conversion of the PTRS RF frequency from 28 GHz to 3.5 GHz and back to 28 GHz may be combined in some cases to obtain coverage gain. The reference node may then provide TRP TRP at an RF frequency of, for example, 3.5 GHz instead of 28 GHz. 1,2,3 Send down-converted PTRS signal PTR_lo 1,2,3 , and provide correspondingly greater FR1 band coverage for all UEs. The associated overhead of the downconverted FR1 band is therefore very small, as most empty frames are transmitted in addition to the PTR signal. The relative frequency should be doubled, as this makes it easier to achieve strict phase coupling between the bands. This concept also allows for carrier aggregation (CA).

[0087] Ideally, based on the precoding results from one or more reference nodes (e.g., based on detecting whether a predetermined signal is detected or provided at the reference node, based on receiving a signal, or only from certain MPC nodes of one or more networks), transmission parameter adjustments that may be useful for improving network node transmission can be detected, such as by determining LO frequency and / or precoding weight adjustments for one or more network nodes, which may, for example, indicate parasitic effects at the network node. In some cases, these adjusted transmission parameters can then be used to transmit data or signals to one or more UEs within a cell or cooperation area. In this way, parasitic effects affecting the entire cooperation area of all active UEs can be corrected.

[0088] These network nodes or tracking transceivers may be placed, for example, in hotspot areas where maximum efficiency may be most important.

[0089] For solutions where JT CoMP precoding is limited to the strongest MPC, tracking of a predetermined signal (e.g., a notch signal) can provide a robust solution because the analysis and feedback at the reference node relies on, for example, the strongest MPC from each of the multiple network nodes that are part of the JTCoMP transmission. In this way, channel fluctuations of the NLOS (non-line-of-sight) channel and its reflections can be reduced.

[0090] Compared to the expected predetermined (e.g., notched) signal, the frequency domain and / or time domain multi-notched signal (e.g., a notch at each of a plurality of subcarriers, or a notched signal at each of a plurality of reference nodes) as the actual received signal may be useful for accurately estimating the parasitic effects of one or more transmission network nodes, such as relative phase noise, frequency offset, or time delay between cooperating cells or sites / cooperating network nodes. Therefore, such transmission parameter adjustments performed based on precoding performance feedback can be used for transmissions to one or more UEs, including JT CoMP data transmissions to one or more UEs.

[0091] Predefined transmit parameter variations allow for identification of the root cause of notch degradation during the training phase and later based on the spatial field close to the tracking receiver.

[0092] For example embodiments of UL tracking, the reference node may, for example, transmit only one PTR per cell or per site for all beams (e.g., via a wide beam or omnidirectional transmission), which is a significant reduction in PTRS signaling overhead in the case of a large number of beams, as it may be the case for FR2 bands. Combined with down-conversion and up-conversion of the PTR RF frequency from 28 GHz to 3.5 GHz and back to 28 GHz, the tracking transceiver can provide additional high FR1 coverage for all UEs. Without this up- and down-conversion, at least in some cases, the transceiver may need to be located near the UE hotspot or have to use some type of power boost.

[0093] Example 1. Figure 7 is a flow chart illustrating the operation of a network node according to an example embodiment. Operation 710 includes, by a network node within a wireless network, transmitting a first precoded tracking signal to a reference node based on estimated precoding weights, the estimated precoding weights being estimated to provide a predetermined signal at the reference node. Operation 720 includes, by the network node, receiving a message from the reference node including information regarding whether the predetermined signal was received at the reference node based at least in part on the first precoded tracking signal transmitted by the network node. Operation 730 includes, if the predetermined signal was not received at the reference node, performing, by the network node, the following: adjusting one or more transmission parameters of the network node, which were estimated to more accurately provide the predetermined signal at the reference node; and transmitting, by the network node, a second precoded tracking signal based on the adjusted transmission parameters.

[0094] Example 2. The method according to Example 1 further includes: the network node determining, for signal transmission at least from the network node, the estimated precoding weight estimated to provide the predetermined signal at the reference node based at least on a channel state information measurement report received from the reference node.

[0095] Example 3. The method of any one of Examples 1 to 2, wherein the adjusting comprises adjusting at least one of the following to adjust the position of the predetermined signal: a precoding weight or a local oscillator frequency of the network node.

[0096] Example 4. The method according to any one of Examples 1 to 3 further includes: the network node sending data to one or more user equipment within the wireless network based on the adjusted transmission parameters.

[0097] Example 5. A method according to any one of Examples 1 to 4, wherein the predetermined signal includes at least one of the following: a notch signal, the notch signal having an amplitude less than a first threshold at a reference point for one or more subcarriers; or a peak signal, the peak signal having an amplitude greater than a second threshold at the reference point for one or more subcarriers.

[0098] Example 6. A method according to any one of Examples 1 to 5, wherein receiving, by the network node, a message including information about whether the predetermined signal is received at the reference node includes receiving, by the network node, information including at least one of the following: an amplitude of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node; an amplitude and phase of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node; a signal parameter of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node, the signal parameter including information related to the network node at least one of the following: amplitude, phase, or delay of at least one multipath component of a plurality of network nodes; a difference between corresponding signal parameters of the strongest multipath components of a plurality of network nodes; an indication of whether a notch signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, the notch signal having an amplitude less than a first threshold for one or more subcarriers; an indication of whether a peak signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, the peak signal having an amplitude greater than a second threshold for one or more subcarriers; a recommended change or adjustment to one or more precoding weights that is estimated to more accurately provide the predetermined signal at the reference node.

[0099] Example 7. The method according to any one of Examples 1 to 6 further includes: receiving, by the network node, an additional message from the reference node, the additional message indicating that the predetermined signal is received at the reference node at least partially based on the second precoded tracking signal; and sending, by the network node, data to one or more user devices within the wireless network based on the adjusted transmission parameters.

[0100] Example 8. A method according to any one of Examples 1 to 7, wherein adjusting one or more transmission parameters of the network node by the network node includes the network node performing one or more of the following adjustments: adjusting the amplitude and / or phase of at least one precoding weight for the network node; adjusting the transmission delay or transmission timing for the network node; or adjusting or tuning the frequency of a local oscillator for the network node.

[0101] Example 9. A method according to any one of Examples 1 to 8, wherein the network node includes a first network node, and wherein the predetermined signal is a signal provided at the reference node based on a collaborative joint transmission of precoded signals from multiple network nodes, the collaborative joint transmission including the transmission of the first precoded signal from the first network node and the transmission of another precoded signal from at least one other network node.

[0102] Example 10. A method according to any one of Examples 2 to 9, wherein determining, by the network node for a signal transmission at least from the network node, estimated precoding weights estimated to provide the predetermined signal at the reference node includes: receiving, by the network node, the estimated precoding weights from a centralized unit or controller.

[0103] Example 11. A method according to any one of Examples 1 to 10, wherein the message received by the network node from the reference node, and whether the predetermined signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, includes: at least one signal parameter of at least one multipath component associated with the network node, of a signal received by the network node, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node.

[0104] Example 12. A method according to any one of Examples 1 to 11, wherein the first precoded tracking signal sent by the network node includes multiple multipath components, and wherein receiving a message by the network node from the reference node regarding whether the predetermined signal is received at the reference node includes: receiving a message by the network node from the reference node, the message at least indicating whether the predetermined signal is simulated at the reference node at least in part based on the strongest multipath component among the multiple multipath components of at least the first precoded tracking signal sent by the network node, and the network node simultaneously ignoring one or more other multipath components among the multiple multipath components of the first precoded tracking signal sent by the network node.

[0105] Example 13. A method according to any one of Examples 1 to 12, wherein the predetermined signal is a signal that is simulated or calculated by the tracking node based on a superposition of at least one multipath component received from each of a plurality of network nodes, the superposition being part of a collaborative joint transmission of precoded signals from the plurality of network nodes.

[0106] Example 14. A method according to any one of Examples 1 to 13, wherein: the network node includes at least one of the following: a transmitter receiver point TRP, a base station BS, an access point AP, a distributed unit DU, a remote radio head RRH, or a relay node; the reference node includes at least one of the following: a user equipment UE, a user device, a base station BS, or a relay node.

[0107] Example 15. Figure 8 8 is a flow chart illustrating operation of a network node according to another example embodiment. Operation 810 includes, by a network node within a wireless network, transmitting a first precoded tracking signal to a reference node based on estimated precoding weights estimated to provide a predetermined signal at the reference node; receiving, by the network node, feedback from the reference node, the feedback relating to precoding performance based on at least the first precoded tracking signal; and adjusting, based on the received feedback, one or more transmission parameters of the network node estimated to more accurately provide the predetermined signal at the reference node.

[0108] Example 16. The method according to Example 15 also includes: the network node determines, for signal transmission at least from the network node, the estimated precoding weight estimated to provide the predetermined signal at the reference node based at least on a channel state information measurement report received from the reference node.

[0109] Example 17. The method of any one of Examples 15 to 16, further comprising: transmitting, by the network node, a second precoded tracking signal based on the adjusted transmission parameter.

[0110] Example 18. A method according to any one of Examples 15 to 17, wherein the receiving feedback includes: receiving, by the network node, a message from the reference node including information regarding whether the predetermined signal is received at the reference node at least in part based on the first precoded tracking signal sent by the network node.

[0111] Example 19. An apparatus comprising components for performing the method according to any one of Examples 1 to 18.

[0112] Example 20. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by at least one processor, are configured to cause a computing system to perform the method according to any one of Examples 1 to 18.

[0113] Example 21. An apparatus comprising: at least one processor; and at least one memory comprising computer program code; the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least perform a method according to any one of Examples 1 to 18.

[0114] Example 22. Figure 9 9 is a flow chart illustrating operation of a reference node according to an example embodiment. Operation 910 includes receiving, by a reference node, a first signal based at least in part on a first precoded tracking signal received by the reference node from at least one network node; determining, by the reference node, whether the first signal is a predetermined signal; and sending, by the reference node, a message to the at least one network node, the message relating to whether the predetermined signal was received at the reference node; and if the predetermined signal was not received at the reference node, receiving, by the reference node, a second signal based at least in part on an adjusted transmission parameter for the at least one network node, the adjusted transmission parameter being adjusted in response to the message.

[0115] Example 23. The method of Example 22, wherein the receiving the second signal comprises: receiving the second signal by the reference node at least in part based on a second precoded tracking signal received from the at least one network node, the second precoded tracking signal being based on an adjusted transmission parameter for the at least one network node that is adjusted in response to the message.

[0116] Example 24. A method according to any one of Examples 22 to 23, wherein the adjusted transmission parameters include at least one of the following: an adjusted precoding weight or a local oscillator frequency of the network node, which is estimated to more accurately provide the predetermined signal at the reference node.

[0117] Example 25. A method according to any one of Examples 22 to 24, wherein the predetermined signal includes at least one of the following: a notch signal, the notch signal having an amplitude less than a first threshold at a reference point for one or more subcarriers; a peak signal, the peak signal having an amplitude greater than a second threshold at the reference point for one or more subcarriers.

[0118] Example 26. A method according to any one of Examples 22 to 25, wherein sending a message by the reference node to the at least one network node regarding whether the predetermined signal is received at the reference node includes sending a message by the reference node to the at least one network node including information, the information including at least one of the following: the amplitude of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node; the amplitude and phase of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node; and signal parameters of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node, the signal parameters including The method comprises at least one of: an amplitude, phase, or delay of at least one multipath component associated with the network node; a difference between corresponding signal parameters of the strongest multipath components of multiple network nodes; an indication of whether a notch signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, the notch signal having an amplitude less than a first threshold for one or more subcarriers; an indication of whether a peak signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, the peak signal having an amplitude greater than a second threshold for one or more subcarriers; or a suggested change or adjustment to one or more precoding weights that are estimated to more accurately provide the predetermined signal at the reference node.

[0119] Example 27. The method of any one of Examples 22 to 26 further includes: determining, by a reference node, that the second signal is the predetermined signal; and sending, by the reference node, a message to the at least one network node, the message indicating that the predetermined signal is received at the reference node.

[0120] Example 28. A method according to any one of Examples 22 to 27: wherein the first signal is a first signal provided at the reference node based on a collaborative joint transmission of precoded signals from multiple network nodes; and wherein receiving the second signal includes: receiving, by the reference node, a second signal provided at the reference node based on a collaborative joint transmission of precoded signals from the multiple network nodes in response to the message, the precoded signal being based on the adjusted transmission parameters.

[0121] Example 29. The method of any one of Examples 22 to 28, further comprising: receiving, by the reference node, data from the at least one network node based on the adjusted transmission parameters.

[0122] Example 30. A method according to any one of Examples 22 to 29, wherein the sending of a message related to whether the predetermined signal is received at the reference node includes: selecting, by the reference node, at least one multipath component received from the at least one network node within the first signal; estimating whether the predetermined signal has been received by the reference node based on the at least one selected multipath component received from the at least one network node; and sending, by the reference node, a message to the at least one network node, the message related to whether the predetermined signal is received at the reference node.

[0123] Example 31. The method of Example 30: wherein the first signal received by the reference node is based on the superposition of multiple multipath components, and the multiple multipath components include at least one multipath component received by the reference node from each of a plurality of network nodes; wherein the selection includes: selecting the strongest multipath component among the multiple multipath components received from each of the plurality of network nodes.

[0124] Example 32. A method according to any one of Examples 22 to 31, wherein: the network node includes at least one of the following: a transmitter receiver point (TRP), a base station (BS), an access point (AP), a distributed unit (DU), a remote radio head (RRH) or a relay node; the reference node includes at least one of the following: a user equipment (UE), a user device, a base station (BS) or a relay node.

[0125] Example 33. The method according to any one of Examples 22 to 32 further includes: the reference node receiving the following instructions from the network node: sending a reference signal on behalf of the network node; and the reference node sending a reference signal to one or more user devices based on the instructions.

[0126] Example 34. A method according to any one of Examples 22 to 33, wherein the reference signal includes a phase tracking reference signal.

[0127] Example 35. A method according to any one of Examples 33 to 34, wherein receiving the instruction includes: the reference node receiving an instruction and an indication of a frequency band from the network node, the instruction being to send a phase tracking reference signal on behalf of the network node, and the phase tracking reference signal should be sent within the frequency band.

[0128] Example 36. The method of Example 35, wherein the sending a reference signal comprises sending, by the wireless node, a phase tracking reference signal to one or more user equipment via the indicated frequency band.

[0129] Example 37. Figure 10 10 is a flow chart illustrating operation of a reference node according to another example embodiment. Operation 1010 includes receiving, by the reference node, a first signal based at least in part on a first precoded tracking signal received by the reference node from at least one network node, wherein the first signal is provided at the reference node based on a coordinated joint transmission of precoded signals from a plurality of network nodes; determining, by the reference node, whether the first signal is a predetermined signal; and sending, by the reference node, a message to the at least one network node regarding whether the predetermined signal was received at the reference node.

[0130] Example 38. A method according to Example 37, wherein the predetermined signal includes at least one of the following: a notch signal, the notch signal having an amplitude less than a first threshold at a reference point for one or more subcarriers; a peak signal, the peak signal having an amplitude greater than a second threshold at the reference point for one or more subcarriers.

[0131] Example 39. A method according to any one of Examples 37 to 38, wherein sending a message by the reference node to the at least one network node regarding whether the predetermined signal is received at the reference node includes: sending a message by the reference node to the at least one network node including information, the information including at least one of the following: the amplitude of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node; the amplitude and phase of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node; a signal parameter of a signal, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node, the signal parameter including The method comprises at least one of: an amplitude, phase, or delay of at least one multipath component associated with the network node; a difference between corresponding signal parameters of the strongest multipath components of multiple network nodes; an indication of whether a notch signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, the notch signal having an amplitude less than a first threshold for one or more subcarriers; an indication of whether a peak signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node, the peak signal having an amplitude greater than a second threshold for one or more subcarriers; or a suggested change or adjustment to one or more precoding weights that are estimated to more accurately provide the predetermined signal at the reference node.

[0132] Example 40. The method according to any one of Examples 37 to 39 further includes: the reference node receiving the following instructions from the network node: sending a reference signal on behalf of the network node; and the reference node sending a reference signal to one or more user devices based on the instructions.

[0133] Example 41. A method according to any one of Examples 37 to 40, wherein the reference signal includes a phase tracking reference signal.

[0134] Example 42. A method according to any one of Examples 40 to 41, wherein receiving the instruction includes: the reference node receiving an instruction and an indication of a frequency band from the network node, the instruction being to send a phase tracking reference signal on behalf of the network node, and the phase tracking reference signal should be sent within the frequency band.

[0135] Example 43. The method of Example 42, wherein the sending a reference signal comprises sending, by the wireless node, a phase tracking reference signal to one or more user equipment via the indicated frequency band.

[0136] Example 44. An apparatus comprising components for performing the method of any one of Examples 22 to 43.

[0137] Example 45. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by at least one processor, are configured to cause a computing system to perform the method according to any one of Examples 22 to 43.

[0138] Example 46. An apparatus comprising: at least one processor; and at least one memory comprising computer program code; the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least perform a method according to any one of Examples 22 to 43.

[0139] Example 47. Figure 11 1 is a flow chart illustrating operation of a wireless node according to an example embodiment. Operation 1110 includes receiving, by a wireless node within a wireless network, an instruction from a network node to transmit a phase tracking reference signal on behalf of the network node; and transmitting, by the wireless node based on the instruction, a phase tracking reference signal to one or more user equipment.

[0140] Example 48. A method according to Example 47, wherein the receiving includes: the wireless node receiving an instruction and an indication of a frequency band from the network node, the instruction being to send a phase tracking reference signal on behalf of the network node, and the phase tracking reference signal should be sent within the frequency band.

[0141] Example 49. The method of Example 48, wherein the sending comprises sending, by the wireless node based on the instruction, a phase tracking reference signal to one or more user equipment via the indicated frequency band.

[0142] Example 50. The method according to any one of Examples 47 to 49 further includes: the wireless node performing down-conversion or up-conversion of the phase tracking reference signal to the indicated frequency band to maintain the phase information of the phase tracking reference signal sent on the indicated frequency band.

[0143] Example 51. The method of Example 50, wherein a frequency divider is used by the wireless node to downconvert the frequency band from a first frequency band to a second frequency band while maintaining the phase information of the phase tracking reference signal.

[0144] Example 52. The method of any one of Examples 47 to 51, wherein the wireless node comprises one of: a user device, a user equipment (UE), or other wireless node.

[0145] Example 53. An apparatus comprising components for performing the method of any one of Examples 47 to 52.

[0146] Example 54. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by at least one processor, are configured to cause a computing system to perform a method according to any one of Examples 47 to 52.

[0147] Example 55. An apparatus comprising: at least one processor; and at least one memory comprising computer program code; the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least perform a method according to any one of Examples 47 to 52.

[0148] Figure 12 1 is a block diagram of a wireless station or network node (e.g., AP, BS, gNB or user equipment / UE, or other network node) 1200 according to an example embodiment. The wireless station 1200 may include, for example, one or more (e.g., Figure 12 The wireless station also includes two RF (radio frequency) or wireless transceivers 1202A and 1202B, each of which includes a transmitter for sending signals and a receiver for receiving signals. The wireless station also includes a processor or control unit / entity (controller) 1204 for executing instructions or software and controlling the transmission and reception of signals, and a memory 1206 for storing data and / or instructions.

[0149] The processor 1204 may also make decisions or determinations, generate frames, packets, or messages for transmission, decode received frames or messages for further processing, and perform other tasks or functions described herein. For example, the processor 1204, which may be a baseband processor, may generate messages, packets, frames, or other signals for transmission via the wireless transceiver 1202 (1202A or 1202B). The processor 1204 may control the transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by the wireless transceiver 1202). The processor 1204 may be programmable and capable of executing software or other instructions stored in a memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. The processor 1204 may be (or may include), for example, hardware, programmable logic, a programmable processor executing software or firmware, and / or any combination thereof. For example, using other terminology, the processor 1204 and the transceiver 1202 may be considered together as a wireless transmitter / receiver system.

[0150] In addition, reference Figure 12, the controller (or processor) 1208 can execute software and instructions and can provide overall control for the station 1200 and can Figure 12 Other systems not shown provide controls, such as controlling input / output devices (e.g., display, keypad), and / or may execute software for one or more applications that may be provided on wireless station 1200, such as an email program, audio / video applications, a word processor, voice over IP applications, or other applications or software.

[0151] Additionally, a storage medium may be provided that includes stored instructions that, when executed by a controller or processor, may cause the processor 1204 or other controller or processor to perform one or more of the functions or tasks described above.

[0152] According to another example embodiment, the RF or wireless transceiver(s) 1202A / 1202B may receive signals or data and / or transmit or send signals or data. The processor 1204 (and possibly the transceiver 1202A / 1202B) may control the RF or wireless transceiver 1202A or 1202B to receive, transmit, broadcast or send signals or data.

[0153] However, the embodiments are not limited to the systems given as examples, but those skilled in the art may apply the solutions to other communication systems. Another suitable example of a communication system is a 5G system. It is assumed that the network architecture in 5G will be very similar to that of Advanced LTE. 5G may use multiple-input multiple-output (MIMO) antennas, more base stations or nodes than LTE (the so-called small cell concept), including macro sites operating in collaboration with small base stations, and may also adopt various radio technologies to achieve better coverage and enhanced data rates.

[0154] It should be understood that future networks will likely utilize network function virtualization (NFV), which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that can be operationally connected or linked together to provide services. A virtualized network function (VNF) may include one or more virtual machines that use standard or general-purpose types of servers rather than customized hardware to run computer program code. Cloud computing or data storage may also be used. In radio communications, this may mean that node operations may be performed at least in part in a server, host, or node that is operatively coupled to a remote radio head. Node operations may also be distributed among multiple servers, nodes, or hosts. It should also be understood that the division of work between core network operations and base station operations may be different from LTE or even non-existent.

[0155] The embodiments of the various technologies described herein may be implemented in a digital electronic circuit system, or in computer hardware, firmware, software, or in a combination thereof. The embodiments may be implemented as a computer program product, i.e., a computer program tangibly implemented in an information carrier, for example, in a machine-readable storage device or in a propagation signal, for execution by a data processing device (e.g., a programmable processor, a computer or multiple computers) or for controlling the operation of the data processing device. The embodiments may also be provided on a computer-readable medium or a computer-readable storage medium that may be a non-transient medium. The embodiments of the various technologies may also include embodiments provided via transient signals or media, and / or downloadable programs and / or software embodiments via the Internet or (multiple) other networks (wired networks and / or wireless networks). In addition, the embodiments may be provided via machine type communication (MTC) or via the Internet of Things (IOT).

[0156] A computer program may be in source code form, object code form, or some intermediate form, and may be stored on a carrier, distribution medium, or computer-readable medium, which may be any entity or device capable of carrying the program. Examples of such carriers include recording media, computer memory, read-only memory, optical and / or electrical carrier signals, telecommunications signals, and software distribution packages. Depending on the required processing power, a computer program may be executed on a single electronic digital computer or distributed across multiple computers.

[0157] Furthermore, embodiments of the various techniques described herein may utilize cyber-physical systems (CPS) (systems of cooperating computing elements that control physical entities). CPS can implement and utilize a large number of interconnected ICT devices (sensors, actuators, processors, microcontrollers, etc.) embedded in different locations in physical objects. Mobile cyber-physical systems (where the physical system in question has inherent mobility) are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robots and electronic devices that are transported by humans or animals. The popularity of smartphones has increased interest in the field of mobile cyber-physical systems. Therefore, various embodiments of the techniques described herein may be provided via one or more of these techniques.

[0158] Computer programs such as the aforementioned (multiple) computer programs may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as stand-alone programs or as modules, components, subroutines, or other units or portions thereof suitable for a computing environment. A computer program may be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[0159] The method steps may be performed by one or more programmable processors executing a computer program or portion of a computer program to perform functions by operating on input data and generating output. The method steps may also be performed by, and apparatus may be implemented as, special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0160] Processors suitable for executing a computer program include, for example, general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer, chip, or chipset. Typically, the processor will receive instructions and data from a read-only memory or a random access memory, or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer may also include, or be operatively coupled to receive data from, or send data to, or both, one or more mass storage devices (e.g., magnetic, magneto-optical, or optical disks) for storing data. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD ROM and DVD-ROM disks. The processor and memory may be supplemented by, or incorporated in, special-purpose logic circuitry.

[0161] To provide interaction with a user, embodiments may be implemented on a computer having a display device (e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor) for displaying information to the user and a user interface (e.g., a keyboard and a pointing device, e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices may also be used to provide interaction with the user; for example, feedback provided to the user may be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including sound, voice, or tactile input.

[0162] Embodiments may be implemented in a computing system that includes a back-end component, such as a data server; or a middleware component, such as an application server; or a front-end component, such as a client computer with a graphical user interface or a web browser through which a user can interact with the embodiments; or any combination of such back-end components, middleware components, or front-end components. The components may be interconnected by any form or medium of digital data communication, such as a communication network. Examples of communication networks include local area networks (LANs) and wide area networks (WANs), such as the Internet.

[0163] While certain features of the described embodiments have been described herein, numerous modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It should therefore be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the various embodiments.

Claims

1. A method of communication, comprising: transmitting, by a network node within the wireless network, a first precoded tracking signal to a reference node based on estimated precoding weights estimated to provide a predetermined signal at the reference node; receiving, by the network node from the reference node, a message comprising information regarding whether the predetermined signal is received at the reference node based at least in part on the first precoded tracking signal sent by the network node; as well as adjusting one or more transmission parameters of the network node, which are estimated to more accurately provide the predetermined signal at the reference node, if the predetermined signal is not received at the reference node; and sending, by the network node, a second precoded tracking signal based on the adjusted transmission parameter; wherein the predetermined signal is a signal provided at the reference node based on a coordinated joint transmission of precoded signals from a plurality of network nodes, the coordinated joint transmission comprising the transmission of the first precoded signal from the network node and the transmission of another precoded signal from at least one other network node; Wherein receiving, by the network node, the message from the reference node comprising information regarding whether the predetermined signal is received at the reference node comprises receiving, by the network node, a difference between corresponding signal parameters of the strongest multipath components of the plurality of network nodes.

2. The method according to claim 1, wherein the predetermined signal comprises at least one of the following: a notch signal having an amplitude less than a first threshold at a reference point for one or more subcarriers; or A peak signal having an amplitude greater than a second threshold at the reference point for one or more subcarriers.

3. The method of claim 1 , wherein receiving, by the network node, a message from the reference node including information regarding whether the predetermined signal is received at the reference node comprises receiving, by the network node, signal parameters including a signal received by the reference node based at least in part on the first precoded tracking signal sent by the network node, the signal parameters including at least one of the following: amplitude, phase, or delay of at least one multipath component associated with the network node.

4. The method according to claim 1, further comprising: receiving, by the network node, a further message from the reference node, the further message indicating that the predetermined signal is received at the reference node based at least in part on the second precoded tracking signal; as well as Data is sent by the network node to one or more user equipments within the wireless network based on the adjusted transmission parameters.

5. The method of claim 1 , wherein adjusting, by the network node, one or more transmission parameters of the network node comprises the network node performing one or more of the following adjustments: adjusting an amplitude and / or phase of at least one precoding weight for the network node; adjusting a transmission delay or transmission timing to the network node; or The frequency of a local oscillator for the network node is adjusted or tuned.

6. The method according to any one of claims 1 to 5, wherein: The network node includes at least one of the following: a transmitter receiver point TRP, a base station BS, an access point AP, a distributed unit DU, a remote radio head RRH, or a relay node; The reference node includes at least one of the following: user equipment, a base station BS, or a relay node.

7. A device for communication, comprising: at least one processor; and at least one memory including computer program code; The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform the method according to any one of claims 1 to 6.

8. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by at least one processor, are configured to cause a computing system to perform the method according to any one of claims 1 to 6.

9. A method of communication, comprising: receiving, by a reference node, a first signal based at least in part on a first precoded tracking signal received by the reference node from at least one network node; determining, by the reference node, whether the first signal is a predetermined signal; sending, by the reference node, a message to the at least one network node, the message being related to whether the predetermined signal is received at the reference node; as well as receiving, by the reference node, a second signal based at least in part on an adjusted transmission parameter for the at least one network node, the adjusted transmission parameter being adjusted in response to the message, if the predetermined signal is not received at the reference node; wherein the first signal is a first signal provided at the reference node based on coordinated joint transmission of precoded signals from a plurality of network nodes; wherein receiving a second signal comprises: receiving, by the reference node, a second signal provided at the reference node based on a coordinated joint transmission of precoded signals from the plurality of network nodes in response to the message, the precoded signal being based on the adjusted transmission parameter; And wherein sending, by the reference node, the message to the at least one network node regarding whether the predetermined signal is received at the reference node comprises sending a difference between corresponding signal parameters of strongest multipath components of a plurality of network nodes.

10. The method according to claim 9, wherein the predetermined signal comprises at least one of the following: a notch signal having an amplitude less than a first threshold at a reference point for one or more subcarriers; A peak signal having an amplitude greater than a second threshold at the reference point for one or more subcarriers.

11. The method of claim 9 , wherein sending, by the reference node, a message regarding whether the predetermined signal is received at the reference node to the at least one network node comprises sending, by the reference node, signal parameters of a signal to the at least one network node, the signal being received by the reference node based at least in part on the first precoded tracking signal sent by the network node, the signal parameters comprising at least one of the following: an amplitude, a phase, or a delay of at least one multipath component associated with the network node.

12. The method according to any one of claims 9 to 11, further comprising: determining, by the reference node, that the second signal is the predetermined signal; A message is sent by the reference node to the at least one network node, the message indicating that the predetermined signal is received at the reference node.

13. An apparatus for communication, comprising: at least one processor; and at least one memory including computer program code; The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform the method according to any one of claims 9 to 12.

14. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by at least one processor, are configured to cause a computing system to perform the method according to any one of claims 9 to 12.

Images