Distributed Cooperative Beamforming in Wireless Networks

Abstract

Devices, systems, and methods for cooperative wireless communication in a wireless network are described. One example method includes: performing communication by a first node of a plurality of nodes with at least a second node of the plurality of nodes; receiving by the first node a probe from a destination node of the plurality of nodes; calculating a phase of a strongest tap of a channel estimate between the first node and the destination node based on the probe; calculating a phase correction based on the phase of the strongest tap and a phase difference between a first phase of the first node and a second phase of a reference node, the phase difference being based on the communication; and transmitting a message with the phase correction to the destination node.

Description

[Technical field]

[0001] This document is directed to cooperative wireless communication between nodes in a wireless network.

[0002] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Patent Application No. 16 / 513,642, filed July 16, 2019, which is incorporated by reference in its entirety and for all purposes.

[0003] [background] Ad-hoc networks may include spatially distributed single-antenna, power-limited radio nodes that may be dynamic, need not be fully connected, and may operate in a multipath fading propagation environment. These nodes can cooperate to relay messages to remotely located radio nodes (those that are unreachable by linear communication protocols).

[0004] [Summary] This document relates to methods, systems and devices for distributed cooperative beamforming in wireless networks. Embodiments of the disclosed technology can be configured to provide range extension (i.e., the ability to cooperatively relay messages to remote nodes that are otherwise unreachable by a single local radio or even by multiple radios transmitting simultaneously in a phase-noncoherent manner). The distributed cooperative beamforming technology disclosed in this document can be implemented in a variety of devices, including wireless communication receivers in wireless communication systems (e.g., including wireless communication devices, mobile devices, and hotspots in broadband wireless networks).

[0005] In one example aspect, a method for cooperative wireless communication is disclosed. The method includes: performing communication by a first node of a plurality of nodes with at least a second node of the plurality of nodes; receiving, by the first node, a probe from a destination node of the plurality of nodes; calculating a phase of a strongest tap of a channel estimate between the first node and the destination node based on the probe; calculating a phase correction based on the phase of the strongest tap and a phase difference between a first phase of the first node and a second phase of a reference node, the phase difference being based on the communication; sending a message with the phase correction to the destination node; Equipped with.

[0006] In another example aspect, a method for cooperative wireless communication is disclosed, the method comprising: performing communication by a first node of a plurality of nodes with at least a second node of the plurality of nodes; calculating a plurality of phase differences between the first node and each node of the plurality of nodes based on the communication; receiving a first probe from a first destination node of the plurality of nodes; calculating a first channel estimate between the first node and the first destination node based on the first probe; selecting a reference node from the plurality of nodes based on the plurality of phase differences; subsequent to selecting the reference node, calculating a first phase correction based on (i) the first channel estimate and (ii) a phase difference between a first phase of the first node and a second phase of the reference node; transmitting a message based on the first phase correction; and Equipped with.

[0007] In yet another exemplary aspect, a system for cooperative wireless communication is disclosed, the system comprising a plurality of nodes, Each of the plurality of nodes - receiving a message from a source node; - performing bidirectional communication with at least one other node of said plurality of nodes; - calculating a plurality of phase differences between each of said plurality of nodes and each other of said plurality of nodes based on said bidirectional communication; receiving a probe from a destination node different from said source node and each of said plurality of nodes; - calculating the phase of the strongest tap of a channel estimate between said each of said plurality of nodes and said destination node based on said probes; - selecting a reference node from said plurality of nodes based on said plurality of phase differences; - subsequent to selecting the reference node, calculating a phase correction based on the phase of the strongest tap and on a phase difference between the first phase of each of the plurality of nodes and a second phase of the reference node; - transmitting said message with said phase correction to said destination node in parallel with each other node of said plurality of nodes; It is configured as follows.

[0008] In yet another exemplary aspect, the above-described methods are implemented in the form of processor executable code and stored on a computer readable program medium.

[0009] In yet another exemplary aspect, a device configured or operable to perform the above-described method is disclosed.

[0010] These and other aspects and their implementations are described in more detail in the drawings, description and claims. [Brief description of the drawings]

[0011] [Figure 1A] We present existing approaches and implementations for distributed cooperative beamforming. [Figure 1B]We present existing approaches and implementations for distributed cooperative beamforming. [Figure 1C] We present existing approaches and implementations for distributed cooperative beamforming. [Figure 2A] 1 illustrates stages of an example embodiment for distributed cooperative beamforming in accordance with the techniques of this disclosure. [Figure 2B] 1 illustrates stages of an example embodiment for distributed cooperative beamforming in accordance with the techniques of this disclosure. [Figure 2C] 1 illustrates stages of an example embodiment for distributed cooperative beamforming in accordance with the techniques of this disclosure. [Figure 2D] 1 illustrates stages of an example embodiment for distributed cooperative beamforming in accordance with the techniques of this disclosure. [Diagram 3] 1 illustrates a flowchart of an example method for cooperative wireless communication, in accordance with an embodiment of the techniques of this disclosure. [Figure 4A] 1 illustrates a flowchart of another example method for cooperative wireless communication, in accordance with an embodiment of the techniques of this disclosure. [Figure 4B] 1 illustrates a flowchart of another example method for cooperative wireless communication, in accordance with an embodiment of the techniques of this disclosure. [Diagram 5] 1 is a block diagram representation of a portion of a radio that can be used to implement embodiments of the techniques of this disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A Mobile Ad-Hoc Network (MANET) is a continuously self-configuring, infrastructure-less network of wirelessly connected mobile devices. MANETs typically include spatially distributed single-antenna, power-limited radio nodes (which may or may not be land-based). In one example, the network may be dynamic (nodes move) and may be completely disconnected (complete network coverage may require multiple hops). In another example, the radios may operate in a multipath fading propagation environment and may employ constant envelope (CE) modulation for increased power efficiency.

[0013] Distributed cooperative beamforming was originally proposed to improve the data leakage capability of sensor networks consisting of static low-power nodes with narrowband (low data rate) measurements. The benefits included increased energy efficiency and therefore increased operational lifetime.

[0014] Embodiments of the techniques of this disclosure exploit another aspect of distributed cooperative beamforming: range extension, i.e., the ability to cooperatively relay messages to remote (or destination) nodes that would otherwise be unreachable by a single local radio, or even by multiple radios transmitting simultaneously in a phase-noncoherent manner. The benefits of range extension can also be translated into other desirable attributes (higher rates to the destination, lower required transmit power, etc.).

[0015] To realize the coherence gains offered by distributed cooperative beamforming, the radio frequency (RF) arrival phase of individual transmissions must be aligned to the intended destination. Unlike traditional beamforming that relies on co-located transmitters, in distributed cooperative beamforming, the RF transmission phase is different (and typically unknown or unestimable) for each participating transmitter. Thus, a process of phase cooperation (also called self-coherence) is required across multiple radios. This process typically compensates for phase changes due to mobility as well as RF impairments (oscillator frequency offset, drift, phase noise, etc.).

[0016] Section headings are present in this document to improve the readability of the description and do not in any way limit the discussion or embodiments (and / or implementations) to only the corresponding section.

[0017] [Existing methods for distributed cooperative beamforming]

[0018] The implementation of distributed cooperative beamforming focuses on phase calibration or phase adjustment, and there are several mechanisms by which phase calibration for distributed cooperative beamforming can be achieved.

[0019] 1A shows an example of master-slave analog synchronization in which narrowband calibration beacons exchanged between the radios are used to match the RF carrier phase to an available phase-locked loop (PLL) circuit. This approach is not feasible for all radio front-ends, including modern tactical radios with integrated transceiver architectures that offer limited or no control over the RF PLL to enable such synchronization.

[0020] Figure 1B shows an example of a closed-loop digital phase control approach where the destination node (DST) manages the phase of each radio individually. This approach is not suitable for MANET tactical operations because it requires a high-power uplink from each radio (which is a direct consequence of the per-radio management of phase). This can result in increased detectability of the radios, which can jeopardize tactical operations. Another disadvantage of the closed-loop approach is the complexity burden imposed on the destination node (which may not have the processing power), which limits the applicable use cases.

[0021] 1C shows an example of an open-loop approach that requires the radios to first achieve phase calibration locally (i.e., with respect to a given local reference radio (or node)) and then leverage downlink (from the destination node to each other node) signals to beamform to the destination. The entire beamforming phase calibration is achieved with low dependency on the destination node, improving overall system robustness, but requires the specification (or establishment) of a reference node before beamforming can begin.

[0022] It is noted that with respect to existing approaches and in this document, "open-loop" does not mean that the destination is not involved at all. That is, "open-loop" does not mean "destination-blind." Rather, it means that the phase calibration to the destination involves signaling in only one direction (only the "downlink") from the destination to the local network (as opposed to two-way signaling, which requires the local node to also transmit to the destination, called the closed-loop option).

[0023] Exemplary embodiments of distributed cooperative beamforming

[0024] Embodiments of the techniques of this disclosure provide phase adjustment methods to enable distributed beamforming in relevant scenarios with real-world radio constraints, RF impairments and multipath propagation. Furthermore, local mechanisms for cooperative transmission and data sharing with coarse timing synchronization between radios that are typically available in various wireless networking technologies are leveraged.

[0025] This paper describes a spatially distributed wireless network node i We now describe distributed cooperative beamforming from a set of (i=1,2,...,K) towards a remote cooperative wireless destination node D. In some embodiments, a method for distributed cooperative beamforming in a network including multiple network nodes (or nodes or radios) includes four stages.

[0026] Stage 1 Each network node gets a “common message” sent by a “source S”, which is the message to be beamformed towards a destination D.

[0027] Stage 2 Each network node "self-coheres" through a sequence of bidirectional signal exchanges (or a combination of signal and message exchanges) performed between selected pairs of nodes, so that all nodes in the network are included in the self-coherence process to derive and store phase correction values.

[0028] Stage 3 Each network node receives a broadcast probe signal from a destination node D. Based on this probe, each network node estimates a complex-valued multipath fading baseband channel model, identifies the strongest tap in the channel model, and calculates the phase (argument) of the strongest complex-valued tap. In some embodiments, all network nodes receive the probe from the destination at approximately the same time (e.g., within a time slot or within adjacent time slots).

[0029] Stage 4 Each network node transmits quasi-synchronously (e.g., within a predefined turnaround time upon receiving the destination probe) a common message with a "total correction phase" that is added to the phase (argument) of the complex baseband value representing the information stream (of the common message). The total correction phase is equal to the negative of the sum of the node's phase correction value (derived in stage 2) and the phase (argument) of the strongest complex-valued tap (estimated in stage 3).

[0030] In some embodiments, for constant envelope modulated signals, baseband phase correction can be implemented simply by an index shift into a lookup table that generates information carrying a digital phase sequence, thereby maintaining the constant envelope property of the transmitted signal.

[0031] In some embodiments, a network node may perform these four stages in an order other than the order described above, so long as stage 4 (which includes the actual beamforming operation) is performed last. For example, a network node may first receive a probe from the destination to calculate the phase of the strongest tap of the channel estimate (stage 3), then receive a common message (stage 1), then participate in a self-coherence process with other network nodes to derive its phase correction value (stage 2), and finally perform a beamforming operation (stage 4). As another example, a network node may first participate in a self-coherence process with other network nodes to derive its phase correction value (stage 2), then receive a probe from the destination to calculate the phase of the strongest tap of the channel estimate (stage 3), then receive a common message (stage 1), and finally perform a beamforming operation (stage 4).

[0032] In some embodiments, the four stages of processing described above produce a composite (jointly transmitted and superimposed) signal at the destination node that has a greater signal-to-noise ratio (SNR) than would have been received if each node had jointly transmitted in a phase non-coherent manner, thereby producing distributed beamforming gain.

[0033] In some embodiments, the four stage process described above may be adapted to distribute a common message to multiple destinations simultaneously.

[0034] 2A-2D illustrate four stages of an example embodiment for distributed cooperative beamforming in accordance with the techniques of this disclosure.

[0035] FIG. 2A shows an example of a first message sharing stage, where K network nodes (shaded gray) get a common message from a source (S). In some embodiments, the message may be distributed via a broadcast transmission by one of the network nodes (which also acts as the source in this first stage). In other embodiments, the message may be broadcast by a source outside the network of K nodes (e.g., a drone or satellite broadcasting this common message to a land network so that the land network can further relay the message to D that is otherwise unreachable by the source). In yet other examples, the message may be shared over a backbone type network different from a wireless network (e.g., a high-speed optical network).

[0036] 2B shows an example of a second self-coherence stage. In some embodiments, the objective of the self-coherence processing is to find the matrix Δφ={δφ ij};i≠j;i,j=1,2,…,K, where δφ ij =2(∂ i -∂ j ), and ∂ i is wireless node N i is the phase of a free-running carrier generating oscillator of . By definition, δφ for any i ii = 0. In one example, this is accomplished via a sequence of bidirectional probe signal exchanges (or signal and message exchanges) between a pair of nodes (i,j), as shown in FIG. 2B.

[0037] Once the matrix Δφ is fully computed, a selection process identifies suitable columns that have the desired characteristics. These columns are called reference nodes N r For example, the column [δφ 1r , δφ 2r ,…,δφ Kr ] is calculated and stored in each node. ir (i=1,2,...,K) contains the set of required correction phases used in the beamforming stage (stage 4).

[0038] In some embodiments, the matrix Δφ is calculated by selecting the reference nodes a priori and the reference column [δφ 1r , δφ 2r ,…,δφ Kr ] is calculated by calculating only

[0039] In other embodiments, the matrix Δφ is calculated by performing a round-robin calculation. Starting from a selected "start" node and proceeding in sequence, each node i in the sequence selects its pair-partner node j based on the highest SNR from all links connected to it, and this is repeated with j (unless the next pair-partner node has not been covered before), and so on until all nodes are covered. In other examples, other link measures (e.g., highest signal-to-interference-and-noise ratio (SINR)) may be used to select the next pair-partner node.

[0040] In yet another embodiment, some of the entries of the matrix Δφ are determined by the identity 2Δθ ij =-2Δθ ji and 2Δθ ij =2Δθ ik +2Δθ kj (the latter termed "trigonometric identity"). Alternatively, all entries of Δφ may be determined using the above identities plus the estimate δφ ij It is calculated using an estimate of the quality (error variance).

[0041] The computation of the matrix Δφ in the above-described embodiments does not require a fully connected network (e.g., multiple hop wireless nodes can participate) nor a static network (e.g., the computation may include dynamic phase tracking). In some embodiments, the value δφ ij can be computed in one of two ways: via a purely two-way exchange of signals, or via a mixture of signaling and message exchange.

[0042] Bidirectional signal exchange In some embodiments, the node N i and N j A pure two-way exchange between the first signaling node N i (e.g., tone-like probes, i.e., s i pb (t) = cos(2πf c t+∂ i ).

[0043] In complex envelope notation, the tone

number

number

number

[0044] In this exemplary purely two-way exchange, node N j is the negative of the total phase at baseband, -θ i→j total =-∂ i -∂ i→j ch+∂ j (called "conjugation" or "phase inversion") j ), propagation through a reciprocal channel (with phase ∂ i→j ch and hence the term -∂ i→j ch ) and node N i Down-conversion (phase ∂ i When subtracting i The total phase at the radio baseband is θ i←→j total =(-∂ i -∂ i→j ch +∂ j )+∂ j +∂ i→j ch -∂ i =2(∂ j -∂ i )=-δφ ij It is.

[0045] In some embodiments, the node N j In another embodiment, the node N j is δφ ji To calculate j It may also initiate its own two-way exchange with

[0046] In principle, δφ ji =-δφ ij However, in practice, such estimates may be noisy. In some embodiments, the network protocol may allow for message exchange between the nodes to determine δφ by averaging the individual estimates by both nodes. ij A better estimate of may be generated.

[0047] Message and signal exchange In some embodiments, the mix of signaling and message exchange is as before, with node N i starts to send probes, and node Nj is θ i→j total =∂ i +∂ i→j ch -∂ j In this embodiment, the node N j is node N i Nico's θ i→j total At the same time, node N j sends out a probe signal, which i is the phase θ j→i total =∂ j +∂ j→i ch -∂ i Assuming channel reciprocity, we can calculate ∂ i→j ch =∂ j→i ch Thus, node N i θ j→i total Similarly, θ i→j total possess knowledge of θ i←→j total =θ j→i total -θ i→j total =-δφ ij It can be easily deduced that

[0048] In some embodiments, and as described in the context of bidirectional signal exchange, each node j This process can be repeated starting from δφ ij An estimate of can be shared via messaging.

[0049] 2C illustrates an example of a third per-node phase estimation stage. In some embodiments, a destination node (D) broadcasts a probe, and each network node computes a tap-spaced complex-valued baseband channel model in response to receiving the probe from the destination node. At each node, the magnitudes of the estimated taps are compared and the largest one is selected, after which an argument (phase) estimate ∂ for each node i=1,2,...,K is calculated. i str_tap is used to calculate

[0050] FIG. 2D illustrates an example of a fourth destination beamforming stage. In some embodiments, node N i The transmission from ∂ i total_corr =-∂ i str_tap -δφ ir The correction is performed with a total correction phase given by:

[0051] In some embodiments, a destination node D receives multiple taps as a result of the distributed cooperative beamforming process described in the context of FIGS. 2A-2D. The taps arriving at D are (i) subjected to stage 3 processing, and then each node N i From the appropriate phase ∂ i total_corr and (ii) all other taps not processed for stage 3 (i.e., all taps except the strongest one selected). All selected and processed taps that contribute to the superimposed (jointly transmitted) baseband channel model at destination node D are then summed to δφ rD and therefore δφ rD The other, unselected and unprocessed channel taps coming from all nodes contributing to superimposed channels in D act as noncoherent taps and provide noncoherent power gain but no beamforming gain.

[0052] [Example embodiment with multiple destinations]

[0053] An embodiment of the disclosed technique is a method for detecting a plurality of destinations (D1, D2, ..., D L , may be used to simultaneously transmit the "same" common message to multiple devices (denoted as , , , ). In this embodiment, assume the following: ○ The self-coherence stage of stage 2 is executed, and the reference node N r is selected and the column [δφ 1r , δφ 2r ,…,δφ Kr ] is calculated and stored; and ○D1,D2,…,D L beacons from are received and processed by each node according to stage 3. In some embodiments, the order in which the beacons are received by each network node without mutual interference may be different. In one example, they may arrive in time as a sequence (e.g., a random access scheme with destination identification). In another example, they may include multiple mutually orthogonal beacons (e.g., modulated by orthogonal spreading codes as in CDMA).

[0054] Each node N i Then, according to stage 4 above, l Transmit total correction phase corresponding to (l=1,2,…,L)

number

[0055] For multi-destination beamforming, each node N i is a complex phasor

number

[0056] where the constant

number

number

[0057] [Additional exemplary embodiments of the technology of the present disclosure]

[0058] In some embodiments, each network node is fully connected. Since all nodes are within hearing range of the reference node, the selection of the reference node (completing stage 2 with all nodes individually) may be performed in that order of selection. The selection of the reference node may be related to the best average link SNR (averaged over all other nodes). More generally, any function (e.g., mean, median, maximum, etc.) of a link quality measure (e.g., SNR, SINR, etc.) may be used to determine the selection of the network node. In this embodiment, it is further assumed that the link quality information is available to all nodes, which share it and update it periodically.

[0059] In some embodiments, the reference node may have good access to some network nodes, but not all network nodes, due to some poor quality links. The reference node may identify such faulty link nodes and request the assistance of neighboring nodes via appropriate messages (e.g., they may send a request to perform a bidirectional exchange with the faulty link nodes with more favorable link conditions, thereby assisting in the completion of the entire reference sequence via said identification information).

[0060] In some embodiments, information about the nature of the links (e.g., line-of-sight (LoS) or non-line-of-sight (NLoS)) may be present, and this may be used by each node in the process of filling out the phase matrix to determine which links should be used for their own bidirectional exchanges (e.g., only LoS links are available).

[0061] In some embodiments, the "initial" node may be selected randomly or via a quality metric (e.g., best link SNR among the nodes) and is referred to as "node 1." Node 1 is connected to a second node ("node 2," which may be a node within hearing range of node 1 that has the highest link SNR among all links from node 1) and δφ 12 The pair (1,2) is announced via a short message so that all nodes in the network know which pairs have been covered. Then, node 2 shares δφ 23 , the pair is announced, and so on. This process ends when all nodes within hearing range (e.g., one-hop nodes) are done. If there are nodes within hearing range that are part of the network (e.g., in a network of at least two hops), a node from the second hop will request to join the self-coherence process. The node(s) hearing this will escalate the process to that node, which then completes the process for those within hearing range of the second hop, and this process is repeated until all hops are covered. Thus, distributed cooperative beamforming is applicable to multi-hop networks (not fully connected), provided that the entire multi-hop network is within the probe range of destination D for the subsequent stage.

[0062] In some embodiments, the individual term δφ ijThe estimate of may be realized by a quality measure, giving the sense of the estimating node's confidence in the quality of the term (e.g., the estimated error variance). Various quality measures may be distributed in the message exchange and then used to refine the estimate when completing the matrix Δφ, i.e., when incorporating the weighting terms in the calculation, either through the use of identities (such as trigonometric identities) or when refining the final estimates of the reciprocal links ((i → j) and (j → i)), assuming that the protocol allows both calculations. The final quality measures for all relevant phase difference qualities may be used to select the reference node (e.g., as the one whose column possesses the highest average quality measure). The estimate δφ ij Links whose quality is deemed unacceptable (too noisy) may have their estimates discarded and a different sequence of nodes in the computational process selected.

[0063] In some embodiments, individual links may experience substantial interference (e.g., due to jamming). The elements of the matrix corresponding to such degraded links may be removed from the bidirectional signal exchange (phase measurement) process. Instead, the elements may be filled in via other measurements on the associated non-degraded links and the use of identities (e.g., trigonometric identities) as described above.

[0064] In some embodiments, a network node may use separate oscillator phases for transmit and receive modes.

[0065] In some embodiments, the term δφ ij is computed not only by two-way signal exchange between nodes, but also by a mix of signal and message exchange, whereby messages carry the (quantized) value of the estimated baseband phase of the radio that received the signal and computed such phase. ij The final estimate of is calculated by an appropriate combination of the signal phase and message-carrying phase values.

[0066] In some embodiments, the term δφ ijis estimated via parameter tracking methods that account for mobility and phase noise impairments. Such phase tracking methods can also be used to fill in the estimates (e.g., by prediction) when processing is briefly interrupted. In one example, these tracking methods can also be used to reduce the frequency of two-way exchanges, thereby lowering the network overhead traffic required to support the embodiments described herein.

[0067] In some embodiments, various methods can be employed in selecting the strongest channel tap to calculate each phase. In one example, the strongest channel tap is the tap with the largest direct gain value. In another example, the complex channel tap is calculated via interpolation between taps estimated using observed samples (measurements) of the channel estimation process.

[0068] [Method of distributed cooperative beamforming]

[0069] 3 illustrates a flow chart of an example method 300 for cooperative wireless communication. The method 300 includes, at step 310, performing communication by a first node of a plurality of nodes with at least a second node of the plurality of nodes.

[0070] The method 300 includes, at step 320, receiving, by a first node, a probe from a destination node of the plurality of nodes.

[0071] The method 300 includes, at step 330, calculating a phase of the strongest tap of a channel estimate between the destination node and the first node based on the probe.

[0072] The method 300 includes, at step 340, calculating a phase correction based on the phase of the strongest tap and a phase difference between a first phase of the first node and a second phase of the reference node, where the phase difference is based on the communication.

[0073] The method 300 includes, at step 350, sending a message with the phase correction to a destination node.

[0074] In some embodiments, an ith node of the plurality of nodes is configured to calculate an ith phase correction, and the plurality of nodes are configured to transmit messages with the corresponding phase correction in parallel, in one example, the parallel transmissions from each node are substantially simultaneous (e.g., accounting for timing errors due to hardware mismatch, processing delays, etc.).

[0075] In some embodiments, the phase differences are entries of a phase matrix, and the (i,j)th entry of the phase matrix comprises twice the phase difference between the phase of the ith node and the phase of the jth node, where the ith node and the jth node are different from the destination node. In one example, the reference node is selected from the multiple nodes after at least one row or at least one column of the phase matrix is ​​determined. In one example, the at least one row or at least one column of the determined phase matrix is ​​the same row or column in each of the multiple nodes, thereby enabling each of the multiple nodes to select the same reference node.

[0076] In another example, the entries of the phase matrix corresponding to the first node and the third node are determined based on (i) the entries of the phase matrix corresponding to the first node and the fourth node, and (ii) the entries of the phase matrix corresponding to the third node and the fourth node.

[0077] In some embodiments, the method 300 further includes determining at least one link quality measure between one or more pairs from the plurality of nodes and selecting a reference node based on a function of the at least one link quality measure. In one example, the determination is based on pilot signals or tones. In another example, the at least one link quality measure is a signal-to-noise ratio (SNR) or a signal-to-interference-and-noise ratio (SINR) of a channel between a reference node and a corresponding node of the plurality of nodes. In yet another example, the function is a mean, median, or maximum of the at least one link quality measure.

[0078] In some embodiments, method 300 further includes receiving information corresponding to the message from (a) a third node of the plurality of nodes, (b) a backbone type network, or (c) a source node different from each of the plurality of nodes.

[0079] In some embodiments, the communication includes two-way communication performed with each of the multiple nodes.

[0080] In some embodiments, the communication or probe comprises a constant envelope signal.

[0081] 4A and 4B show a flowchart of another example of a method 400 for cooperative wireless communication. The method 400 includes, at step 410, performing communication by a first node of the plurality of nodes with at least a second node of the plurality of nodes.

[0082] The method 400 includes, at step 420, calculating a plurality of phase differences between the first node and each node of the plurality of nodes based on the communication.

[0083] The method 400 includes, at step 430, receiving a first probe from a first destination node of the plurality of nodes.

[0084] The method 400 includes, at step 440, calculating a first channel estimate between the first node and the first destination node based on the first probe.

[0085] The method 400 includes, at step 450, selecting a reference node from the plurality of nodes based on the plurality of phase differences.

[0086] The method 400 includes, in step 460, following selecting a reference node, calculating a first phase correction based on (i) the first channel estimate and (ii) a phase difference between a first phase of the first node and a second phase of the reference node.

[0087] The method 400 includes, at step 470, transmitting a message based on the first phase correction.

[0088] In some embodiments, the multiple phase differences correspond to a row or column of a phase matrix, and the (i,j)th entry of the phase matrix comprises twice the phase difference between the phase of the ith node and the phase of the jth node.

[0089] In some embodiments, the method 400 further includes receiving a second probe from a second destination node, calculating a second channel estimate between the first node and the second destination node based on the second probe, and calculating a second phase correction based on the second channel estimate and the phase difference subsequent to selecting a reference node, where transmitting the message is further based on the second phase correction. In one example, calculating the first and second channel estimates includes calculating phases of the strongest taps of the first and second channel estimates, respectively.

[0090] In some embodiments, calculating the plurality of phase differences is further based on tracking a phase of at least one node of the plurality of nodes.

[0091] In some embodiments, the method 400 further includes updating at least one of the plurality of phase differences based on one or more of an oscillator frequency offset, an oscillator frequency drift, and a phase noise.

[0092] In some embodiments, and in the context of methods 300 and 400, each node of the plurality of nodes is operable as a source node, a relay node, or a destination node. For example, each node may be a handheld radio in an ad-hoc network capable of originating a first transmission, relaying a received second transmission, and receiving a third transmission without further relaying because it is the destination of the third communication.

[0093] FIG. 5 is a block diagram representation of a portion of a radio in accordance with some embodiments of the techniques of this disclosure. The radio 511 may include processor electronics 501 (such as a microprocessor) that implements one or more of the techniques presented in this document. The radio 511 may include transceiver electronics 503 for transmitting and receiving wireless signals via one or more communication interfaces, such as antenna(s) 509. The radio 511 may include other communication interfaces for transmitting and receiving data. The radio 511 may include one or more memories 507 configured to store information, such as data and / or instructions. In some implementations, the processor electronics 501 may include at least a portion of the transceiver electronics 503. In some embodiments, at least a portion of the techniques, modules, or functions of this disclosure (including but not limited to methods 300 and 400) are implemented using the radio 511.

[0094] The specification and drawings are intended to be considered illustrative only, and by illustrative I mean examples, and do not imply ideal or preferred embodiments unless otherwise stated. As used herein, "or" is intended to include "and / or" (unless the context clearly dictates otherwise).

[0095] Some embodiments described herein are described in the general context of a method or process, which in one embodiment may be implemented by a computer program product embodied in a computer-readable medium including computer-executable instructions (such as program code) executed by a computer in a network environment. The computer-readable medium may include removable and non-removable storage devices, including but not limited to read-only memory (ROM), random access memory (RAM), compact disks (CDs), digital versatile disks (DVDs), and the like. Thus, the computer-readable medium may include non-transitory storage media. Generally, program modules may include routines, programs, objects, components, data structures, and the like that perform particular tasks or implement particular abstract data types. Computer-executable or processor-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. A particular permutation of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

[0096] Some of the disclosed embodiments can be implemented as devices or modules using hardware circuits, software, or a combination thereof. For example, hardware circuit implementations can include discrete analog and / or digital components integrated, for example, as part of a printed circuit board. Alternatively or additionally, the disclosed components or modules can be implemented as ASIC (Application Specific Integrated Circuit) and / or FPGA (Field Programmable Gate Array) devices. Some implementations can additionally or alternatively include digital signal processors (DSPs), which are specialized microprocessors with architectures optimized for the operational needs of digital signal processing related to the disclosed functionality of the present application. Similarly, various components or subcomponents within each module may be implemented in software, hardware, or firmware. Connectivity between modules and / or components within a module may be provided using any one of the connection methods and mediums known in the art, including, but not limited to, communication via the Internet, wired, or wireless networks using appropriate protocols.

[0097] Although this document contains many specifics, these should not be construed as limiting the scope of the invention as described or as it may be claimed, but as describing features specific to a particular embodiment. Certain features described in this document in the context of different embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in a particular combination and may initially be claimed as such, one or more features from the claimed combination may be deleted from the combination in some cases, and the claimed combination may be directed to a subcombination or variation of the subcombination. Similarly, although operations are shown in the figures in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or sequentially, or to perform all of the illustrated operations in order to achieve desired results.

[0098] Only some implementations and examples are described; other implementations, extensions, and variations are possible based on what is described and illustrated in this disclosure.

Claims

1. 1. A method for cooperative wireless communications, comprising: performing communication by a first node of a plurality of nodes with at least a second node of the plurality of nodes; receiving, by the first node, a probe from a destination node of the plurality of nodes; calculating a phase of a strongest tap of a channel estimate between the first node and the destination node based on the probe; calculating a phase correction based on the phase of the strongest tap and a phase difference between a first phase of the first node and a second phase of a reference node, the phase difference being based on the communication; sending a message with the phase correction to the destination node; Equipped with the phase difference being an entry of a phase matrix, the (i,j)th entry of the phase matrix comprises twice the phase difference between the phase of the ith node and the phase of the jth node; the i-th node and the j-th node are different from the destination node; the reference node is selected from the plurality of nodes after at least one row or at least one column of the phase matrix is ​​determined; method.

2. the i-th node of the plurality of nodes is configured to calculate an i-th phase correction; the plurality of nodes are configured to transmit the messages with corresponding phase corrections in parallel; The method of claim 1.

3. determining at least one link quality measure between one or more pairs of nodes from the plurality of nodes; selecting the reference node based on a function of the link quality measure; The method of claim 1 further comprising:

4. The method of claim 3 , wherein the determining is based on a pilot signal or a tone.

5. The method of claim 3, wherein the link quality measure is a signal-to-noise ratio (SNR) or a signal-to-interference-and-noise ratio (SINR) of a channel.

6. The method of claim 3 , wherein the function is a mean, a median or a maximum of the at least one link quality measure.

7. 2. The method of claim 1, wherein the entries of the topological matrix corresponding to the first node and the third node are determined based on (i) entries of the topological matrix corresponding to the first node and the fourth node, and (ii) entries of the topological matrix corresponding to the third node and the fourth node.

8. 2. The method of claim 1, further comprising receiving information corresponding to the message from: (a) a third node of the plurality of nodes; (b) a backbone type network; or (c) a source node different from each of the plurality of nodes.

9. The method of claim 1 , wherein the communication comprises bidirectional communication performed with each of the plurality of nodes.

10. The method of claim 1 , wherein the communication or the probe comprises a constant envelope signal.

11. 1. A method for cooperative wireless communication in a network including a plurality of nodes, the method comprising: performing communication, by a first node of the plurality of nodes, with at least a second node of the plurality of nodes; calculating a plurality of phase differences between the first node and each node of the plurality of nodes based on the communication; receiving a first probe from a first destination node among the plurality of nodes; calculating a first channel estimate between the first node and the first destination node based on the first probe; selecting a reference node from the plurality of nodes based on the plurality of phase differences; subsequent to selecting the reference node, calculating a first phase correction based on (i) the first channel estimate and (ii) a phase difference between a first phase of the first node and a second phase of the reference node; transmitting a message based on the first phase correction; and Equipped with the phase difference being an entry of a phase matrix, the (i,j)th entry of the phase matrix comprises twice the phase difference between the phase of the ith node and the phase of the jth node; the i-th node and the j-th node are different from the first destination node; the reference node is selected from the plurality of nodes after at least one row or at least one column of the phase matrix is ​​determined; method.

12. The method of claim 11 , wherein the plurality of phase differences corresponds to a row or a column of the phase matrix.

13. receiving a second probe from a second destination node; calculating a second channel estimate between the first node and the second destination node based on the second probe; subsequent to selecting the reference node, calculating a second phase correction based on the second channel estimate and the phase difference; Further equipped with transmitting the message further comprises: The method of claim 11.

14. 14. The method of claim 13, wherein calculating the first and second channel estimates comprises calculating a phase of a strongest tap of the first and second channel estimates, respectively.

15. The method of claim 11 , wherein calculating the plurality of phase differences is further based on tracking a phase of at least one node of the plurality of nodes.

16. The method of claim 11 , further comprising updating at least one of the plurality of phase differences based on at least one of an oscillator frequency offset, an oscillator frequency drift, and a phase noise.

17. 1. A system for cooperative wireless communications, comprising: A plurality of nodes are provided. Each of the plurality of nodes - receiving a message from a source node; - performing bidirectional communication with at least one other node of said plurality of nodes; - calculating a plurality of phase differences between each of said plurality of nodes and each other of said plurality of nodes based on said bidirectional communication; receiving a probe from a destination node different from said source node and each of said plurality of nodes; - calculating the phase of the strongest tap of a channel estimate between said each of said plurality of nodes and said destination node based on said probes; - selecting a reference node from said plurality of nodes based on said plurality of phase differences; - subsequent to selecting the reference node, calculating a phase correction based on the phase of the strongest tap and on a phase difference between a first phase of each of the plurality of nodes and a second phase of the reference node; - transmitting said message with said phase correction to said destination node in parallel with each other node of said plurality of nodes; It is configured as follows: the phase difference being an entry of a phase matrix, the (i,j)th entry of the phase matrix comprises twice the phase difference between the phase of the ith node and the phase of the jth node; the i-th node and the j-th node are different from the destination node; the reference node is selected from the plurality of nodes after at least one row or at least one column of the phase matrix is ​​determined; system.

18. 20. The system of claim 17, wherein the source node is (a) one of the plurality of nodes, (b) a backbone type network node, or (c) a different node from the plurality of nodes.

19. The system of claim 17 , wherein the bidirectional communication or the probe comprises a constant envelope signal.

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