Enhanced over-the-air phase alignment of transmission / reception points via auxiliary nodes

Abstract

Over-the-air alignment of a first network node with a third network node via a second network node can be performed. The first network node can transmit (340) a first reference signal, using a beamformer, to the third network node via the second network node. The first network node can further receive (350) a second reference signal, using the beamformer, from the third network node via the second network node. The first network node can further calibrate (370) a transmission of the first network node based on the second reference signal.

Description

P112049W001ENHANCED OVER-THE-AIR PHASE ALIGNMENT OF TRANSMISSION / RECEPTION POINTS VIA AUXILIARY NODESTECHNICAL FIELD

[0001] The present disclosure is related to wireless communication systems and more particularly to enhanced over-the-air (“OTA”) phase alignment of transmi ssion / recepti on points (“TRAs”) via auxiliary nodes.BACKGROUND

[0002] FIG. 1 illustrates an example of a new radio (“NR”) network (e.g., a 5th Generation (“5G”) network) including a 5G core (“5GC”) network 130, network nodes 120a-b (e.g., 5G base station (“gNB”)), multiple communication devices 110 (also referred to as user equipment (“UE”)).

[0003] Distributed multiple-input-multiple output (“D-MIMO”) is a strong sixth generation (“6G”) candidate technology. Some types of D-MIMO operation rely on phase-coherent operation of large numbers of antennas that are distributed over a large area, which enables performance of coherent joint transmissions (“CJTs”). Practical D-MIMO systems can include multiple panels (e.g., multiple transmission / reception points (“TRPs”) or access points (“APs”)) and each panel includes multiple antenna elements.SUMMARY

[0004] According to some embodiments, a method of operating a first network node in a wireless communications network that further comprises a second network node and a third network node is provided. The method includes transmitting a first reference signal, using a beamformer, to the third network node via the second network node. The method further includes receiving a second reference signal, using the beamformer, from the third network node via the second network node. The method further includes calibrating a transmission of the first network node based on the second reference signal.

[0005] According to other embodiments, a method of operating a third network node in a wireless communications network that further comprises a first network node and a second network node is provided. The method includes receiving a pilot signal from the second network node. The method further includes determining a beamformer based on the pilot signal. The method further includes receiving a first reference signal, using the beamformer, from the first network node via the second network node. The method further includes transmitting aP112049W001 second reference signal, using the beamformer, to the first network node via the second network node.

[0006] According to other embodiments, a method of performing over-the-air alignment of a first network node with a third network node via a second network node is provided. The method includes transmitting, by the first network node using a first beamformer, a first reference signal to the third network node via the second network node. The method further includes receiving, by the third network node using a second beamformer, the first reference signal from the first network node via the second network node. The method further includes transmitting, by the third network node using the second beamformer, a second reference signal to the first network node via the second network node. The method further includes receiving, by the first network node using the first beamformer, the second reference signal from the third network node via the second network node. The method further includes determining a phase difference between the first reference signal and the second reference signal. The method further includes calibrating a transmission of the first network node based on the second reference signal.

[0007] According to other embodiments, a communication device, a network node, a computer program, a computer program product, a host, a system, or a non-transitory computer- readable medium is provided to perform one of the above methods.

[0008] Certain aspects of these embodiments may provide technical advantages. In some embodiments, the proposed over-the-air (“OtA”) phase alignment procedure does not require centralized phase reference or wired interconnections between transmission / reception points (“TRPs”). In additional or alternative embodiments, more robust inter-TRP phase alignment for coherent joint transmission (“CJT”) accuracy is achieved, even when there is no strong direct link (e.g., line-of-sight (“LOS”)) between the two TRPs. In some examples, the procedure provides beamforming gains at the involved TRPs, which increases the link budget / link reliability between TRPs and the auxiliary node N and therefore increases the phase alignment accuracy (which may be a problem in current user equipment (“UE”)-aided phase-alignment schemes).

[0009] In additional or alternative embodiments, proposed procedures have wide applicability, since the intermediary node can be embodied in many different ways (e.g., a repeater, a third TRP, a UE, or a reflective intelligent surface (“RIS”)).P112049W001BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate certain non-limiting embodiments. In the drawings:

[0011] FIG. 1 is a schematic diagram illustrating an example of a 5thgeneration (“5G”) network;

[0012] FIG. 2 is a signal flow diagram illustrating an example of a protocol for OTA phase alignment of TRPs via an auxiliary node in accordance with some embodiments;

[0013] FIG. 3 is a flow chart illustrating an example of operations performed by a first network node in accordance with some embodiments;

[0014] FIG. 4 is a flow chart illustrating an example of operations performed by a third network node in accordance with some embodiments;

[0015] FIG. 5 is a flow chart illustrating an example of operations performed by a system in accordance with some embodiments;

[0016] FIG. 6 is a block diagram of a communication system in accordance with some embodiments;

[0017] FIG. 7 is a block diagram of a user equipment in accordance with some embodiments;

[0018] FIG. 8 is a block diagram of a network node in accordance with some embodiments; and

[0019] FIG. 9 is a block diagram of a virtualization environment in accordance with some embodiments.DETAILED DESCRIPTION

[0020] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art, in which examples of embodiments are shown. Some embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of present inventive concepts to those skilled in the art. It should also be noted that these embodiments are not mutually exclusive. Components from one embodiment may be tacitly assumed to be present / used in another embodiment.P112049W001

[0021] Under the assumption of channel reciprocity, channel state information (“CSI”) required for CJTs from different TRPs may be derived from uplink (“UL”) channel soundings. This operation mode is typically referred to as reciprocity-based operation and the main benefit is that, for large (distributed) antenna systems, much smaller training overheads are needed to learn the downlink (“DL”) CSI compared to performing a full DL beam / antenna sweep (plus feedback of the measured DL signals / channels to the gNB side). Reciprocity-based operation is especially suitable for time-division duplex (“TDD”) systems since full (amplitude and phase) channel reciprocity can be exploited if the UL training and DL data transmissions are performed within a time smaller than the coherence time of the channel (e.g., within an orthogonal frequency division multiplexing (“OFDM”) slot of the 3GPP new radio (“NR”) standard).

[0022] However, even though the propagation channel between a TRP and a UE is reciprocal, the presence of the analog front-end circuitry in the radio transceivers of the TRPs and UEs complicates the situation and makes the baseband-to-baseband channel non-reciprocal. Hence, in order to make use of the reciprocity assumption and rely on the uplink reference signals to compute downlink precoding coefficients, the non-reciprocal transceiver responses need to be phase aligned. More specifically, and as it is well known in the literature, only the TRP non-reciprocal responses need to be phase aligned (and not the UE transceiver responses).

[0023] In some embodiments herein, the terms phase alignment and calibration are used interchangeably.

[0024] There currently exists several challenges with regards to some procedures. In some examples, phase alignment between TRPs can be performed via wired connections between TRPs. This is a very expensive solution and highly impractical to deploy and maintain. This motivates over-the-air (“OtA”) methods for inter- TRP phase alignment.

[0025] In additional or alternative examples, some procedures for OtA phase alignment exchange signals directly between TRPs. However, these need a strong direct link (e.g., line of sight (“LOS”)) between the TRPs. If the direct link is weak (e.g., the LOS is blocked), the performance of OtA phase alignment suffers significantly.

[0026] In additional or alternative examples, phase alignment can alternatively be performed by involving UEs in order to facilitate gNBs to exchange OtA signaling for phase alignment. However, sometimes a UE doesn’t have enough UL and (or DL) link budget to ensure robust inter- TRP calibration. Moreover, not all UEs have the capability to support OTA TRP calibration.

[0027] Various embodiments described herein disclose a protocol for over-the-air (“OTA”) phase alignment between two TRPs via an auxiliary node N (e.g., a relay / repeater, a third TRP, aP112049W001RIS, or a UE). In some embodiments, reciprocal beamforming at both TRPs (towards the auxiliary node) is employed to increase the link budget, and therefore increase the calibration accuracy. In some examples, the term “phase alignment” will be used, but this term can also refer to “phase and amplitude alignment” between two TRPs, which can be used for spatial nullforming.

[0028] In additional or alternative embodiments, the first TRP beamforms a PhaseAlign signal (e.g., with beamformer b^) to the auxiliary node N, which receives and forwards it to the second TRP. The second TRP receives the signal with beamformer b2and processes it in order to obtain a second reference signal. The second TRP then beamforms the second reference signal (with beamformer b\, where b is the transpose of ft2) back to N which then forwards it to the first TRP. Upon reception with beamformerthe first TRP estimates the relative phase offset between the TRPs, and uses this phase offset to phase align the two TRPs (e.g. for CJT later on). In some examples, the procedure can operate without any need for reciprocity calibration of the auxiliary node N. In additional or alternative examples, the procedure works even though the auxiliary node yields different (phase) responses when forwarding signals towards different link directions.

[0029] In additional or alternative embodiments, b and b2may be the complex conjugates of the (estimated) channels between the first TRP and N, and the second TRP and N, respectively.

[0030] In additional or alternative embodiments, prior to phase alignment, the auxiliary node (N) first transmits one or more pilots; the TRPs use these pilots to estimate the channels between the respective TRP and N and based on the so-obtained channel estimate, obtain their respective beamformers to it, b and b2.

[0031] FIG. 2 illustrates an example of signal flow within a system including a first network node (gNBl), a second network node (auxiliary node N), and a third network node (gNB2). The signal flow includes operations that can exchange measurements between two TRPs (the first network node and the third network node) via the second network node (auxiliary node N) for OTA phase alignment. In some examples, the TRPs do not have any direct link between them that is reliable enough for calibration. In this example, the TRPs communicate using the auxiliary node N.

[0032] In some embodiments, it can be assumed that the different pilot transmissions involved in operations 210-270 are included in a time / frequency grid where the transmit chain response and receive chain response from TRP1 and TRP2, represented by t1(r1(t2, r2, are roughly time- and frequency-invariant.P112049W001

[0033] In additional or alternative embodiments, the auxiliary node can be assumed to have a single antenna, but the functionality disclosed can be generalized for the case that the auxiliary node has, for example, two antenna ports as the case of a two-panel repeater.

[0034] In additional or alternative embodiments, each TRP / gNB has multiple antennas / radio frequency (“RF”) chains and it is assumed that all RF chains / antennas within each TRP are locally calibrated for reciprocity (which can be performed with proprietary massive MIMO calibration methods). In these examples, the final component to be able to perform CJT from the two locally calibrated TRPs may be to determine one calibration coefficient which mitigates the impact of a phase (and amplitude) offset between the TRPs.

[0035] In operation 204, the auxiliary node N may transmit a pilot signal to the first TRP and / or to the second TRP. In operation 206, the first TRP may estimate the corresponding channel to N. In operation 208, the second TRP may estimate the corresponding channel to N. From these corresponding channel estimates, the first and / or second TRP may compute beamforming vectors to be used in the next protocols steps, namely b and / or b2.

[0036] The beamformers b and b2may be any beamforming vectors. Accordingly, some embodiments do not include operation 204. Instead, in operation 206 and operation 208, beamformers b and b2may be determined by each of the TRPs. However, it can be preferable that they are aligned with the propagation channel towards the auxiliary node in order to harvest beamforming gain so that larger calibration accuracy is attained. Therefore, as illustrated in FIG. 2, b and b2may be the complex conjugate of the channels estimated from N to TRP 1 and TRP2, respectively. In additional or alternative embodiments, b may be the DFT vector that is best aligned with the strongest path between TRP1 and N, and b2may be a DFT vector that is aligned with the strongest path between TRP2 and N.

[0037] In some examples, the auxiliary node N transmits a reference signal on its own in pre-determined time / frequency resources which are known to one or two TRPs. The reference signal can be internally synthesized at N (e.g., if N is a third TRP, or a UE which supports this capability and was previously configured by the network to do so), or if this reference signal transmission is the result of repeating an already ongoing reference signal transmission (e.g., if N is a repeater, RIS, or a UE that supports this capability and was previous configured by the network to do so).

[0038] The above description of FIG. 2 assumes that that the same pilot signal is used by TRP1 and TRP2, however, in some embodiments the auxiliary node N transmits two different pilot signals (e.g., one to the first TRP and one to the second TRP in different (time / frequency) instances).P112049W001

[0039] At operation 220, the first TRP, TRP1, transmits a first reference signal using a beamformer b17and the auxiliary node N receives it and forwards or retransmits it to the second TRP. In some examples, the auxiliary node N is configured a priori by the TRPs in order to be able to perform measurements in certain time / frequency resources (e.g., physical resource blocks (“PRBs”)). The configuration may be done wirelessly via radio resource control (“RRC”) or downlink control information (“DCI”) (e.g., using 3GPP network controlled repeater (“NCR”)’s framework). In additional or alternative examples, this configuration is performed via a wired or wireless interface between N and the network. In additional or alternative examples, the auxiliary node N is able to instantaneously re-transmit what it is currently measuring, preferably while applying some amplification to the signal.

[0040] In some embodiments, the functionality of the intermediary node is that of an amplify-and-forward repeater (“AFR”), which retransmits its received signal instantaneously (as in the network-controlled repeaters functionality specified in NR). In additional or alternative embodiments, the auxiliary node can be a relay which can amplify the received first reference signal and forwards it to the second TRP instantaneously. In additional or alternative embodiments, the auxiliary node can be a reflective intelligent surface (“RIS”) which reflects the received first reference signal towards the second TRP - the reflection patterns of the RIS may be set apriori to ensure that the signal is reflected in correct directions.

[0041] In additional or alternative embodiments, the disclosed protocol may also be executed if N does not have the capability to instantaneously measure and retransmit a signal just like an AFR, but instead it has the capability of retransmitting the measured signal at a later time instance than when it has measured it. In that example, the auxiliary node N may be able to store measurements or information representative of the measurements, locally in a storage memory. This can include the auxiliary node having down-conversion and sampling capabilities, via carrier mixer components and / or analog-to-digital converters (“ADCs”). In additional or alternative examples, the auxiliary node N is able to transmit what it has stored in memory, for example, by applying some amplification to the signal.

[0042] The signal model of operation 220 is as follows. The first reference signal transmitted by the first TRP can be denoted as and the reciprocal channel between the first TRP and the auxiliary node N can be denoted as G CA, where A is the number of antennas at the first TRP. Then the received signal at N isP112049W001 where rNand are the complex valued responses of the receive and transmit chains of the auxiliary node N and the first TRP, respectively. Sinceis a pilot scalar which is assumed to be known to both the TRPs, it can be set to 1 without loss of generality. Therefore, yWi= rNhT1b1t1(2)

[0043] However, the protocol holds even for any reference signal (scalar or vector) with appropriate processing. Therefore, the innovations can be used with any kind of reference signal that can be used for single antenna or multi antenna TRPs and auxiliary nodes.

[0044] As partly addressed previously, the phase misalignment across the two TRPs can result from the fact that the transmit and receive chains’ responses of TRP1, namely Zqand r15drift (over time) independently of the transmit and receive chains’ responses of TRP2, namely t2, r2. (As previously mentioned, it can be assumed that all RF chains within one TRP have been locally calibrated, so that the remaining ambiguities are the “per- TRP” transmit and receive chain responses, i.e.for TRP 1, and t2and r2for TRP 2). Some embodiments include calibrating the differences of these responses so that coherent reciprocity -based DL beamforming can be done by these 2 TRPs.

[0045] In some embodiments, the TRPs’ transceiver gainsr15t2and r2are frequency invariant to a large extent (e.g., typically vary over much larger than typical bandwidths assigned to wireless communication, such as 5MHz). Thus, the calibration protocols may be executed only in a much smaller portion of the bandwidth in which it is desired to phase align the transceiver gains.

[0046] At operation 230, upon measuring the first reference signal, the measurement being denoted by yN1, the auxiliary node N retransmits / forwards it to the second TRP. The overall contribution to the repeated signal by the auxiliary node can be the cascade of its receive and transmit gains tNrN, which jointly take into account any phase shift and / or amplification applied (e.g., see eq. (3)).

[0047] At operation 240, upon receiving the signal forwarded by N, the second TRP applies a beamformer b2to obtain a complex scalar as follows:= T b h tNrNh{b t , (3) where h G CBis the (reciprocal) channel between N and the second TRP, B is the number of antennas at the second TRP, tNand r2are the complex valued responses of the transmit and receive chains of N and the second TRP, respectively.P112049W001

[0048] The propagation channels between the first TRP and N (i.e., h^), and the second TRP and N (i.e., h2)arereciprocal (i.e., the propagation channel between the TRP j and N is the same as that between N and TRP j., where j belongs to { 1, 2}). This implies that the entire signaling procedure may be executed within a channel coherence time / frequency interval.

[0049] At operation 250, upon obtaining y22, the second TRP processes it and obtains a second reference signal. One example of such processing is the inversion of y22.1723=T221 =• 7’ . . . 7 . . > ) r2 b2h2tNrNh b4t

[0050] Another part of the processing may concern power normalization of y23. Explained shortly, y23will be transmitted in operation 260 by TRP2, thus y23may be amplitude renormalized to satisfy a predetermined transmit power constraint, e.g. in order to ensure that the normalized signal y23is transmitted at maximum power by TRP 2. In such a case, the coefficient associated with this power re-normalization may or may not be transmitted from TRP2 to TRP1 over a (backhaul) control channel or a dedicated proprietary channel. If such a coefficient is transmitted, TRP1 may then use this information later to “correct” for this power normalization in the received signal in operation 280. More specifically, if in operation 250 a normalization factor a is used so that the transmitted signal is effectively ay23, in operation 270 the correction to the received signal should be y^ / a. This correction may not be important if only phase-alignment between TRPs is to be achieved, and thus transmitting the normalization coefficient from TRP 2 to TRP 1 may be skipped in this case. However, this correction can be important in case amplitude and phase-allignment between TRPs is to be achieved (e.g. if both TRPs would like to jointly perform spatial nullforming). Thus, in one embodiment, TRP2 transmits to TRP1 the power normalization factor applied over a (backhaul) control channel or dedicated proprietary channel.

[0051] At operation 260, the second TRP transmits the second reference signal y23in (4) with beamformer b2which is received by the auxiliary node N as:

[0052] At operation 270, the auxiliary node N forwards / retransmits the second reference signal yN4in (5) to the first TRP. This operation is similar to operation 230, but in the reverse link direction.P112049W001

[0053] At operation 280, the first TRP receives the second reference signal yW4from the auxiliary node N and combines it with beamformer b4as715

[0054] Upon obtaining y15, the first TRP estimates the phase (and amplitude) difference between the transmitted first reference signal and the received second reference signal. However, the desired calibration coefficient for coherent joint transmissions from the two TRPs is exactly the measurement performed in operation 280, namely y15- this turns out to be the correct calibration coefficient for CJT. Thus, in one embodiment, TRP1 uses directly the measurement of eq. (6) as calibration coefficient.

[0055] As previously stated, if any power normalization a was applied in operation 250 to y23, then the reverse effect can be applied in operation 280 by dividing y15by a.

[0056] At operation 290, the estimated phase difference is used to phase-align the two TRPs and CJT can be done from them for several purposes. A few examples are: Wireless power transfer to an energy neutral device, beamformed data transfer from distributed TRPs to a UE, precoded data transfer from distributed TRPs to multiple UEs.

[0057] Operations of a network node 800 (implemented using the structure of FIG. 8) will now be discussed with reference to the flow charts of FIGS. 3-5 according to some embodiments of inventive concepts. For example, modules may be stored in memory 804 of FIG. 8, and these modules may provide instructions so that when the instructions of a module are executed by the respective network node processing circuitry 802, network node 800 performs respective operations of the flow charts.

[0058] FIG. 3 illustrates an example of operations performed by a first network node in a wireless communications network that includes a second network node and a third network node. In some examples, the second network node is at least one of a communication device (e.g., a user equipment), a TRP, a RIS, and a repeater.

[0059] At block 310, processing circuitry 802 transmits, via communication interface 806, a request for a pilot signal to the second network node.

[0060] At block 320, processing circuitry 802 receives, via communication interface 806, a pilot signal from the second network node.

[0061] At block 330, processing circuitry 802 determines a beamformer based on the pilot signal. In some embodiments, determining the beamformer comprises performing complex conjugation of the pilot signal.P112049W001

[0062] At block 340, processing circuitry 802 transmits, via communication interface 806, a first reference signal, using the beamformer, to the third network node via the second network node.

[0063] At block 350, processing circuitry 802 receives, via communication interface 806, a second reference signal, using the beamformer, form the third network node via the second network node.

[0064] At block 360, processing circuitry 802 receives, via communication interface 806, an indication of a re-scaling factor used by the third network node to generate the second reference signal.

[0065] At block 370, processing circuitry 802 calibrates a transmission of the first network node based on the second reference signal. In some embodiments, calibrating the transmission of the first network node includes: determining a phase difference between the first reference signal and the second reference signal; and phase-aligning the first network node and the third network node based on the phase difference. In some examples, calibrating the transmission of the first network node includes, subsequent to phase-aligning the first network node and the third network node, performing a coherent joint transmission, CJT, with the third network node.

[0066] In additional or alternative embodiments, calibrating the transmission of the first network node based on the second reference signal includes amplitude-aligning the first network node and the third network node based on the re-scaling factor.

[0067] FIG. 4 illustrates an example of operations performed by a third network node in a wireless communications network that includes a first network node and a second network node. In some examples, the second network node is at least one of: a communication device (e.g., a user equipment), a TRP, a RIS, and a repeater.

[0068] At block 410, processing circuitry 802 transmits, via communication interface 806, a request for a pilot signal to the second network node.

[0069] At block 420, processing circuitry 802 receives, via communication interface 806, a pilot signal from the second network node.

[0070] At block 430, processing circuitry 802 determines a beamformer based on the pilot signal. In some embodiments, determining the beamformer includes performing complex conjugation of the pilot signal.

[0071] At block 440, processing circuitry 802 receives, via communication interface 806, a first reference signal, using the beamformer, from the first network node via the second network node.P112049W001

[0072] At block 445, processing circuitry 802 determines a second reference signal by taking an inverse of the first reference signal. In some embodiments, determining the second reference signal further includes applying a re-scaling factor to satisfy a power constraint.

[0073] At block 450, processing circuitry 802 transmits, via communication interface 806, the second reference signal, using the beamformer, to the first network node via the second network node.

[0074] At block 480, processing circuitry 802 transmits, via communication interface 806, an indication of the re-scaling factor to the first network node.

[0075] At block 495, processing circuitry 802 performs a CJT with the first network node.

[0076] FIG. 5 illustrates an example of operations performed by a system in a wireless communications network that includes a first network node, a second network node, and a third network node. In some examples, the second network node is at least one of: a communication device (e.g., a user equipment), a TRP, a RIS, and a repeater. In some embodiments, the system includes one or more of the first network node, the second network node, and the third network node.

[0077] At block 502, the first network node receives a first pilot signal from the second network node.

[0078] At block 504, the first network node determines the first beamformer based on the first pilot signal.

[0079] At block 506, the third network node receives a second pilot signal from the second network node. In some examples, the first pilot signal is different from the second pilot signal. In other examples, the first pilot signal is the same as the second pilot signal.

[0080] At block 508, the third network node determines the second beamformer based on the second pilot signal.

[0081] At block 510, the first network node transmits, using a first beamformer, a first reference signal to the third network node via the second network node.

[0082] At block 520, the third network node receives, using a second beamformer, the first reference signal from the first network node via the second network node.

[0083] At block 522, the third network node determines a second reference signal by taking an inverse of the first reference signal and applying a re-scaling factor (e.g., to satisfy a power constraint).

[0084] At block 530, the third network node transmits, using the second beamformer, the second reference signal to the first network node via the second network node.P112049W001

[0085] At block 540, the first network node receives, using the first beamformer, the second reference signal from the third network node via the second network node.

[0086] At block 560, processing circuitry 802 determines a phase difference between the first reference signal and the second reference signal.

[0087] At block 570, processing circuitry 802 calibrates a transmission of the first network node based on the second reference signal. In some embodiments, calibrating the transmission of the first network node includes phase-aligning the first network node and the third network node based on the phase difference. In some examples, calibrating the transmission of the first network node further comprises, subsequent to phase-aligning the first network node and the third network node, performing a coherent joint transmission, CJT, with the third network node.

[0088] In additional or alternative embodiments, calibrating the transmission of the first network node includes amplitude-aligning the first network node and the third network node based on the re-scaling factor.

[0089] Various operations from the flow chart of FIGS. 3-5 may be optional with respect to some embodiments of network nodes and related methods.

[0090] Example embodiments are described below.

[0091] Embodiment 1. A system with two TRPs and an auxiliary node (N) where: the first TRP uses a beamformer b to transmit a first reference signal that is received and retransmitted by N, and received at the second TRP with beamformer b2, the second TRP processing the received first reference signal to obtain a second reference signal; the second TRP transmitting the second reference signal with beamformer b2such that it is received and retransmitted by N, and then received at the first TRP; the first TRP receiving the second reference signal with beamformer b and estimating the phase difference between the transmitted first reference signal and the received second reference signal; and the estimated phase difference is used to phase-align the two TRPs.

[0092] Embodiment 2. The system of Embodiment 1, where prior to the first TRP transmitting a reference signal, N transmits a pilot that is used at the first TRP to compute b1.

[0093] Embodiment 3. The system of Embodiment 1, where prior to the first TRP transmitting a reference signal, N transmits a pilot that is used at the second TRP to compute b2.

[0094] Embodiment 4. The system of any of Embodiments 2-3, where the same pilot is received at TRP1 and TRP2 to compute brand b2. respectively.P112049W001

[0095] Embodiment 5. The system of Embodiment 1, where the processing by the first and second TRP to compute b and b2is phase reversal (complex conjugation) of the received pilot signal.

[0096] Embodiment 6. The system of Embodiment 1, where processing the received first reference signal consists of taking the inverse (=complex conjugate and inverting the amplitude) of the first received reference signal. The amplitude of this signal could also be re-scaled to satisfy a power constraint.

[0097] Embodiment 7. The system of Embodiment 6, where the re-scaling factor, if applied, is communicated by TRP2 to TRP1.

[0098] Embodiment 8. The system of Embodiment 1, where N is a relay / repeater, or a UE, or a TRP, or a RIS.

[0099] Embodiment 9. The system of Embodiment 1, where amplitude-aligning of the two TRPs is done by TRP1 by taking into account the scaling factor communicated by TRP2.

[0100] FIG. 6 shows an example of a communication system 600 in accordance with some embodiments.

[0101] In the example, the communication system 600 includes a telecommunication network 602 that includes an access network 604, such as a radio access network (RAN), and a core network 606, which includes one or more core network nodes 608. The access network 604 includes one or more access network nodes, such as network nodes 610a and 610b (one or more of which may be generally referred to as network nodes 610), or any other similar 3rdGeneration Partnership Project (3 GPP) access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network 602 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 602 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network 602, including one or more network nodes 610 and / or core network nodes 608.

[0102] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU- CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-realP112049W001 time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an 0-2 interface defined by the O-RAN Alliance or comparable technologies. The network nodes 610 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 612a, 612b, 612c, and 612d (one or more of which may be generally referred to as UEs 612) to the core network 606 over one or more wireless connections.

[0103] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 600 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. The communication system 600 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0104] The UEs 612 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with the network nodes 610 and other communication devices. Similarly, the network nodes 610 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 612 and / or with other network nodes or equipment in the telecommunication network 602 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunication network 602.

[0105] In the depicted example, the core network 606 connects the network nodes 610 to one or more host computing systems, such as host 616. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 606 includes one more core network nodesP112049W001(e.g., core network node 608) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 608. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0106] The host 616 may be under the ownership or control of a service provider other than an operator or provider of the access network 604 and / or the telecommunication network 602. The host 616 may host a variety of applications to provide one or more services. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0107] As a whole, the communication system 600 of FIG. 6 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0108] In some examples, the telecommunication network 602 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 602 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 602. For example, the telecommunications network 602 may provide Ultra Reliable Low Latency Communication (URLLC) services toP112049W001 some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs.

[0109] In some examples, the UEs 612 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 604 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 604. Additionally, a UE may be configured for operating in single- or multi -RAT or multi -standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved- UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0110] In the example, the hub 614 communicates with the access network 604 to facilitate indirect communication between one or more UEs (e.g., UE 612c and / or 612d) and network nodes (e.g., network node 610b). In some examples, the hub 614 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 614 may be a broadband router enabling access to the core network 606 for the UEs. As another example, the hub 614 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 610, or by executable code, script, process, or other instructions in the hub 614. As another example, the hub 614 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 614 may be a content source. For example, for a UE that is a VR device, display, loudspeaker, or other media delivery device, the hub 614 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 614 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 614 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0111] The hub 614 may have a constant / persistent or intermittent connection to the network node 610b. The hub 614 may also allow for a different communication scheme and / or schedule between the hub 614 and UEs (e.g., UE 612c and / or 612d), and between the hub 614 and the core network 606. In other examples, the hub 614 is connected to the core network 606 and / or one or more UEs via a wired connection. Moreover, the hub 614 may be configured to connect to an M2M service provider over the access network 604 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the networkP112049W001 nodes 610 while still connected via the hub 614 via a wired or wireless connection. In some embodiments, the hub 614 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to the network node 610b. In other embodiments, the hub 614 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 610b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0112] FIG. 7 shows a UE 700 in accordance with some embodiments. The UE 700 presents additional details of some embodiments of the UE 612 of Figure 1. As used herein, a UE refers to a device capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage / playback device, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), an Augmented Reality (AR) or Virtual Reality (VR) device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0113] A UE may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle- to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0114] The UE 700 includes processing circuitry 702 that is operatively coupled via a bus 704 to an input / output interface 706, a power source 708, a memory 710, a communication interface 712, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in FIG. 7. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multipleP112049W001 instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0115] The processing circuitry 702 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 710. The processing circuitry 702 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 702 may include multiple central processing units (CPUs).

[0116] In the example, the input / output interface 706 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 700. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0117] In some embodiments, the power source 708 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 708 may further include power circuitry for delivering power from the power source 708 itself, and / or an external power source, to the various parts of the UE 700 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging the power source 708. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 708 to make the power suitable for the respective components of the UE 700 to which power is supplied.P112049W001

[0118] The memory 710 may be or be configured to include memory such as random-access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable readonly memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 710 includes one or more application programs 714, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 716. The memory 710 may store, for use by the UE 700, any of a variety of various operating systems or combinations of operating systems.

[0119] The memory 710 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini -dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory 710 may allow the UE 700 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 710, which may be or comprise a device-readable storage medium.

[0120] The processing circuitry 702 may be configured to communicate with an access network or other network using the communication interface 712. The communication interface 712 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 722. The communication interface 712 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 718 and / or a receiver 720 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 718 and receiver 720 may be coupled to one or more antennas (e.g., antenna 722) and may share circuit components, software or firmware, or alternatively be implemented separately.P112049W001

[0121] In the illustrated embodiment, communication functions of the communication interface 712 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short- range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0122] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 712, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0123] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

[0124] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicleP112049W001 charging station, a smart watch, a fitness tracker, a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and / or software in dependence of the intended application of the loT device in addition to other components as described in relation to the UE 700 shown in FIG. 7.

[0125] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3 GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0126] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[0127] FIG. 8 shows a network node 800 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR. NodeBs (gNBs)), O-RAN nodes or components of an O-RAN node (e g., O-RU, O-DU, O-CU).

[0128] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling aP112049W001 relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0129] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi -standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0130] The network node 800 includes a processing circuitry 802, a memory 804, a communication interface 806, and a power source 808. The network node 800 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 800 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair may in some instances be considered a single separate network node. In some embodiments, the network node 800 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 804 for different RATs) and some components may be reused (e.g., a same antenna 810 may be shared by different RATs). The network node 800 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 800, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 800.

[0131] The processing circuitry 802 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logicP112049W001 operable to provide, either alone or in conjunction with other network node 800 components, such as the memory 804, to provide network node 800 functionality.

[0132] In some embodiments, the processing circuitry 802 includes a system on a chip (SOC). In some embodiments, the processing circuitry 802 includes one or more of radio frequency (RF) transceiver circuitry 812 and baseband processing circuitry 814. In some embodiments, the radio frequency (RF) transceiver circuitry 812 and the baseband processing circuitry 814 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 812 and baseband processing circuitry 814 may be on the same chip or set of chips, boards, or units.

[0133] The memory 804 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 802. The memory 804 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry 802 and utilized by the network node 800. The memory 804 may be used to store any calculations made by the processing circuitry 802 and / or any data received via the communication interface 806. In some embodiments, the processing circuitry 802 and memory 804 are integrated.

[0134] The communication interface 806 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, the communication interface 806 comprises port(s) / terminal(s) 816 to send and receive data, for example to and from a network over a wired connection. The communication interface 806 also includes radio front-end circuitry 818 that may be coupled to, or in certain embodiments a part of, the antenna 810. Radio front-end circuitry 818 comprises filters 820 and amplifiers 822. The radio front-end circuitry 818 may be connected to an antenna 810 and processing circuitry 802. The radio front-end circuitry may be configured to condition signals communicated between antenna 810 and processing circuitry 802. The radio front-end circuitry 818 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 818 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 820 and / or amplifiers 822. TheP112049W001 radio signal may then be transmitted via the antenna 810. Similarly, when receiving data, the antenna 810 may collect radio signals which are then converted into digital data by the radio front-end circuitry 818. The digital data may be passed to the processing circuitry 802. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0135] In certain alternative embodiments, the network node 800 does not include separate radio front-end circuitry 818, instead, the processing circuitry 802 includes radio front-end circuitry and is connected to the antenna 810. Similarly, in some embodiments, all or some of the RF transceiver circuitry 812 is part of the communication interface 806. In still other embodiments, the communication interface 806 includes one or more ports or terminals 816, the radio front-end circuitry 818, and the RF transceiver circuitry 812, as part of a radio unit (not shown), and the communication interface 806 communicates with the baseband processing circuitry 814, which is part of a digital unit (not shown).

[0136] The antenna 810 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 810 may be coupled to the radio front-end circuitry 818 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 810 is separate from the network node 800 and connectable to the network node 800 through an interface or port.

[0137] The antenna 810, communication interface 806, and / or the processing circuitry 802 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, the antenna 810, the communication interface 806, and / or the processing circuitry 802 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0138] The power source 808 provides power to the various components of network node 800 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 808 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 800 with power for performing the functionality described herein. For example, the network node 800 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 808. As a further example, the power source 808P112049W001 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0139] Embodiments of the network node 800 may include additional components beyond those shown in FIG. 8 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node 800 may include user interface equipment to allow input of information into the network node 800 and to allow output of information from the network node 800. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 800. In some embodiments providing a core network node, such as core network node 608 of FIG. 6, some components, such as the radio front-end circuitry 818 and the RF transceiver circuitry 812 may be omitted.

[0140] FIG. 9 is a block diagram illustrating a virtualization environment 900 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 900 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 900 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface. Virtualization may facilitate distributed implementations of a network node, UE, core network node, or host.

[0141] Applications 902 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 900 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.P112049W001

[0142] Hardware 904 includes processing circuitry, memory that stores software and / or instructions executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 906 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 908a and 908b (one or more of which may be generally referred to as VMs 908), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. The virtualization layer 906 may present a virtual operating platform that appears like networking hardware to the VMs 908.

[0143] The VMs 908 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 906. Different embodiments of the instance of a virtual appliance 902 may be implemented on one or more of VMs 908, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0144] In the context of NFV, a VM 908 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 908, and that part of hardware 904 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 908 on top of the hardware 904 and corresponds to the application 902.

[0145] Hardware 904 may be implemented in a standalone network node with generic or specific components. Hardware 904 may implement some functions via virtualization. Alternatively, hardware 904 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 910, which, among others, oversees lifecycle management of applications 902. In some embodiments, hardware 904 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In someP112049W001 embodiments, some signaling can be provided with the use of a control system 912 which may alternatively be used for communication between hardware nodes and radio units.

[0146] Although the computing devices described herein (e.g., UEs, network nodes) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0147] In certain embodiments, some or all of the functionalities described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionalities may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionalities are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

Claims

P112049W001CLAIMSWhat is claimed is:

1. A method of operating a first network node in a wireless communications network that further comprises a second network node and a third network node, the method comprising: transmitting (340) a first reference signal, using a beamformer, to the third network node via the second network node; receiving (350) a second reference signal, using the beamformer, from the third network node via the second network node; and calibrating (370) a transmission of the first network node based on the second reference signal.

2. The method of Claim 1, further comprising: receiving (320) a pilot signal from the second network node; and determining (330) the beamformer based on the pilot signal.

3. The method of Claim 2, further comprising: transmitting (310) a request for the pilot signal to the second network node.

4. The method of any of Claims 2-3, wherein determining the beamformer comprises performing complex conjugation of the pilot signal.

5. The method of any of Claims 1-4, wherein calibrating the transmission of the first network node comprises: determining a phase difference between the first reference signal and the second reference signal; and phase-aligning the first network node and the third network node based on the phase difference.

6. The method of Claim 5, wherein calibrating the transmission of the first network node further comprises, subsequent to phase-aligning the first network node and the third network node, performing a coherent joint transmission, CJT, with the third network node.P112049W0017. The method of any of Claims 1-6, further comprising: receiving (360) an indication of a re-scaling factor used by the third network node to generate the second reference signal.

8. The method of Claim 7, wherein calibrating the transmission of the first network node based on the second reference signal comprises amplitude-aligning the first network node and the third network node based on the re-scaling factor.

9. The method of any of Claims 1-8, wherein the second network node comprises at least one of: a communication device; a transmission / reception point, TRP; a reflective intelligent surface, RIS; and a repeater.

10. A method of operating a third network node in a wireless communications network that further comprises a first network node and a second network node, the method comprising: receiving (420) a pilot signal from the second network node; and determining (430) a beamformer based on the pilot signal; receiving (440) a first reference signal, using the beamformer, from the first network node via the second network node; and transmitting (450) a second reference signal, using the beamformer, to the first network node via the second network node.

11. The method of Claim 10, further comprising: subsequent to transmitting the second reference signal, performing (495) a coherent joint transmission, CJT, with the first network node.

12. The method of any of Claims 10-11, wherein determining the beamformer comprises performing complex conjugation of the pilot signal.P112049W00113. The method of any of Claims 10-12, further comprising: determining (445) the second reference signal by taking an inverse of the first reference signal.

14. The method of Claim 13, wherein determining the second reference signal further comprises applying a re-scaling factor to satisfy a power constraint.

15. The method of Claim 14, further comprising: transmitting (480) an indication of the re-scaling factor to the first network node.

16. The method of any of Claims 10-15, wherein the second network node comprises at least one of: a communication device; a transmission / reception point, TRP; a reflective intelligent surface, RIS; and a repeater.

17. A method of performing over-the-air alignment of a first network node with a third network node via a second network node, the method comprising: transmitting (510), by the first network node using a first beamformer, a first reference signal to the third network node via the second network node; receiving (520), by the third network node using a second beamformer, the first reference signal from the first network node via the second network node; transmitting (530), by the third network node using the second beamformer, a second reference signal to the first network node via the second network node; receiving (540), by the first network node using the first beamformer, the second reference signal from the third network node via the second network node; determining (560) a phase difference between the first reference signal and the second reference signal; and calibrating (570) a transmission of the first network node based on the second reference signal.P112049W00118. The method of Claim 17, wherein calibrating the transmission of the first network node comprises phase-aligning the first network node and the third network node based on the phase difference.

19. The method of Claim 18, wherein calibrating the transmission of the first network node further comprises, subsequent to phase-aligning the first network node and the third network node, performing a coherent joint transmission, CJT, with the third network node.

20. The method of any of Claims 17-19, further comprising: receiving (502) , by the first network node, a first pilot signal from the second network node; determining (504), by the first network node, the first beamformer based on the first pilot signal; receiving (506), by the third network node, a second pilot signal from the second network node; and determining (508), by the third network node, the second beamformer based on the second pilot signal.

21. The method of Claim 20, wherein the first pilot signal is different from the second pilot signal.

22. The method of Claim 20, wherein the first pilot signal is the same as the second pilot signal.

23. The method of any of Claims 17-22, further comprising: determining (522), by the third network node, the second reference signal by taking an inverse of the first reference signal and applying a re-scaling factor to satisfy a power constraint.

24. The method of Claim 23, wherein calibrating the transmission of the first network node comprises amplitude-aligning the first network node and the third network node based on the rescaling factor.P112049W00125. The method of any of Claims 17-24, wherein the second network node comprises at least one of: a communication device; a transmission / reception point, TRP; a reflective intelligent surface, RIS; and a repeater.

26. A first network node (1100) configured to perform operations comprising: transmitting (340) a first reference signal, using a beamformer, to a third network node via a second network node; receiving (350) a second reference signal, using the beamformer, from the third network node via the second network node; and calibrating (370) a transmission of the first network node based on the second reference signal.

27. The first network node of Claim 26, the operations further comprising any of the operations of Claims 2-9.

28. A computer program comprising program code to be executed by processing circuitry (1102) of a first network node (1100), whereby execution of the program code causes the first network node to perform operations comprising: transmitting (340) a first reference signal, using a beamformer, to a third network node via a second network node; receiving (350) a second reference signal, using the beamformer, from the third network node via the second network node; and calibrating (370) a transmission of the first network node based on the second reference signal.

29. The computer program of Claim 28, the operations further comprising any of the operations of Claims 2-9.

30. A computer program product comprising a non-transitory storage medium (1106) comprising program code to be executed by processing circuitry (1102) of a first network nodeP112049W001(1100), whereby execution of the program code causes the first network node to perform operations comprising: transmitting (340) a first reference signal, using a beamformer, to a third network node via a second network node; receiving (350) a second reference signal, using the beamformer, from the third network node via the second network node; and calibrating (370) a transmission of the first network node based on the second reference signal.

31. The computer program product of Claim 29, the operations further comprising any of the operations of Claims 2-9.

32. A third network node (1100) configured to perform operations comprising: receiving (420) a pilot signal from a second network node; and determining (430) a beamformer based on the pilot signal; receiving (440) a first reference signal, using the beamformer, from a first network node via the second network node; and transmitting (450) a second reference signal, using the beamformer, to the first network node via the second network node.

33. The third network node of Claim 32, the operations further comprising any of the operations of Claims 11-16.

34. A computer program comprising program code to be executed by processing circuitry (1102) of a second network node (1100), whereby execution of the program code causes the third network node to perform operations comprising: receiving (420) a pilot signal from a second network node; and determining (430) a beamformer based on the pilot signal; receiving (440) a first reference signal, using the beamformer, from a first network node via the second network node; and transmitting (450) a second reference signal, using the beamformer, to the first network node via the second network node.P112049W00135. The computer program of Claim 34, the operations further comprising any of the operations of Claims 11-16.

36. A computer program product comprising a non-transitory storage medium (1106) comprising program code to be executed by processing circuitry (1102) of a third network node (1100), whereby execution of the program code causes the third network node to perform operations comprising: receiving (420) a pilot signal from a second network node; and determining (430) a beamformer based on the pilot signal; receiving (440) a first reference signal, using the beamformer, from a first network node via the second network node; and transmitting (450) a second reference signal, using the beamformer, to the first network node via the second network node.

37. The computer program product of Claim 36, the operations further comprising any of the operations of Claims 11-16.

38. A system configured to perform operations comprising: transmitting (510), by a first network node using a first beamformer, a first reference signal to a third network node via a second network node; receiving (520), by the third network node using a second beamformer, the first reference signal from the first network node via the second network node; transmitting (530), by the third network node using the second beamformer, a second reference signal to the first network node via the second network node; receiving (540), by the first network node using the first beamformer, the second reference signal from the third network node via the second network node; determining (560) a phase difference between the first reference signal and the second reference signal; and calibrating (370) a transmission of the first network node based on the second reference signal.

39. The system of Claim 38, the operations further comprising any of the operations of Claims 18-25.P112049W00140. A computer program comprising program code to be executed by processing circuitry (1102) of a system, whereby execution of the program code causes the system to perform operations comprising: transmitting (510), by a first network node using a first beamformer, a first reference signal to a third network node via a second network node; receiving (520), by the third network node using a second beamformer, the first reference signal from the first network node via the second network node; transmitting (530), by the third network node using the second beamformer, a second reference signal to the first network node via the second network node; receiving (540), by the first network node using the first beamformer, the second reference signal from the third network node via the second network node; determining (560) a phase difference between the first reference signal and the second reference signal; and calibrating (370) a transmission of the first network node based on the second reference signal.

41. The computer program of Claim 40, the operations further comprising any of the operations of Claims 18-25.

42. A computer program product comprising a non-transitory storage medium (1106) comprising program code to be executed by processing circuitry (1102) of a system, whereby execution of the program code causes the system to perform operations comprising: transmitting (510), by a first network node using a first beamformer, a first reference signal to a third network node via a second network node; receiving (520), by the third network node using a second beamformer, the first reference signal from the first network node via the second network node; transmitting (530), by the third network node using the second beamformer, a second reference signal to the first network node via the second network node; receiving (540), by the first network node using the first beamformer, the second reference signal from the third network node via the second network node; determining (560) a phase difference between the first reference signal and the second reference signal; andP112049W001 calibrating (370) a transmission of the first network node based on the second reference signal.

43. The computer program product of Claim 42, the operations further comprising any of the operations of Claims 18-25.

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