Clustered coherent distributed spatial multiplexing in wireless communication networks - Patents.com

Abstract

Embodiments of the disclosed technology are directed to spatially multiplexing different digital data streams generated in a distributed network (e.g., MANET, cellular, or Wi-Fi) and transmitted simultaneously toward a destination wireless device having multiple antenna elements. An exemplary method for cooperative communication includes clustering multiple nodes into multiple clusters, such that each of the multiple clusters communicates with a separate antenna of the multiple antennas, and performing distributed beamforming in each of the multiple clusters to transmit corresponding messages of the multiple messages directed to the separate antennas. The described embodiments allow improved performance over existing systems, e.g., increased outage capacity with increasing cluster size.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 294,292, filed December 28, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] TECHNICAL FIELD This specification relates generally to wireless networks, and more specifically to mobile ad-hoc networks (MANETs) configured to implement spatial multiplexing. [Background technology]

[0003] Mobile ad-hoc networks (MANETs) may include spatially distributed, single-antenna, power-limited wireless nodes that may be dynamic, not fully connected, and operate in multipath fading propagation environments that may be clustered and / or coordinated to relay different messages to destination nodes with multiple antennas. Summary of the Invention

[0004] Embodiments of the disclosed technology are directed to multiplexing different digital data streams generated within a MANET and transmitted simultaneously towards a destination radio having multiple antenna elements ("antennas").

[0005] In one example aspect, a system for cooperative communication includes a plurality of nodes and a destination node with a plurality of antennas. According to the disclosed technology, the system is configured to group the plurality of nodes into a plurality of clusters, such that each of the plurality of clusters is configured to simultaneously transmit a separate message directed to a corresponding antenna of the plurality of antennas. Herein, each node in each of the plurality of clusters is configured to receive a probe from a corresponding antenna and generate a corresponding separate message by applying a phase correction before transmitting the corresponding separate message, the calculating the phase correction being based on the probe.

[0006] In another example aspect, a method for cooperative communication from a plurality of nodes to a destination node equipped with a plurality of antennas includes clustering the plurality of nodes into a plurality of clusters, such that each of the plurality of clusters communicates with a distinct antenna of the plurality of antennas, and performing distributed beamforming in each of the plurality of clusters to transmit a corresponding message of the plurality of messages directed to the distinct antenna.

[0007] In yet another example, the above-described methods are embodied in the form of processor executable code and stored on a computer readable program medium.

[0008] In yet another example, a device configured or operable to perform the above-described method is disclosed.

[0009] The above examples and other aspects and their implementations are described in more detail in the drawings, description, and claims. [Brief description of the drawings]

[0010] [Figure 1A] 1 shows an example of distributed spatial multiplexing. [Figure 1B] 1 shows an example of distributed spatial multiplexing.

[0011] [Figure 2A] 1 illustrates steps of an exemplary distributed beamforming (DBF) method. [Figure 2B] 1 illustrates steps of an exemplary distributed beamforming (DBF) method. [Figure 2C] 1 illustrates steps of an exemplary distributed beamforming (DBF) method. [Figure 2D] 1 illustrates steps of an exemplary distributed beamforming (DBF) method.

[0012] [Diagram 3] 1 illustrates an example of a radio frequency (RF) model for implementing clustered coherent distributed spatial multiplexing (CC DSM).

[0013] [Figure 4A] 1 illustrates an exemplary frame structure for implementing the uplink in a CC DSM.

[0014] [Figure 4B] 1 shows an exemplary frame structure for implementing uplink and downlink in CC DSM.

[0015] [Figure 5A] 1 shows exemplary numerical results comparing the performance of the CC DSM with other existing cooperative communication implementations. [Figure 5B] 1 shows exemplary numerical results comparing the performance of the CC DSM with other existing cooperative communication implementations. [Figure 5C] 1 shows exemplary numerical results comparing the performance of the CC DSM with other existing cooperative communication implementations. [Figure 5D] 1 shows exemplary numerical results comparing the performance of CC DSM with other existing cooperative communication implementations.

[0016] [Figure 6] 1 is a flow chart of an example method of cooperative communication. [Figure 7] 1 is a flow chart of an example method of cooperative communication.

[0017] [Figure 8] 1 is a block diagram representation of a portion of a wireless device that may be used to implement embodiments of the disclosed technology. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A Mobile Ad-Hoc Network (MANET) is a continuously self-configuring, infrastructure-free network of wirelessly connected mobile devices. MANETs typically include spatially distributed, single-antenna, power-limited wireless nodes that can be both terrestrial and non-terrestrial. In one example, the network may be dynamic (nodes are moving) and may not be fully connected (multiple hops may be required for complete network coverage). In another example, wireless devices may operate in a multipath fading propagation environment and may use constant envelope (CE) modulation for improved power efficiency.

[0019] Section headings are used herein to improve readability of the description and are not intended to limit the discussion and embodiments (and / or implementations) to only the respective sections.

[0020] 1 Overview of Distributed Beamforming (DBF) and Clustered Coherent Distributed Spatial Multiplexing (CC DSM)

[0021] In various implementations and operating scenarios, nodes (wireless devices) in a MANET wish to send information to a specific location, a "destination node" (or "sink"). The general move to send a common message to a destination in a phase-coherent manner from a distributed set of wireless nodes is called distributed beamforming (DBF). Coherent reception significantly improves received power compared to non-coherent reception and is desirable for various reasons. One possibility is to reach a remotely located destination node that is not reachable via a simple non-coherent communication protocol. The destination is therefore assumed to be very remote, where "remote" may be interpreted to mean far outside the network diameter. Distributed beamforming was originally proposed to improve the data evacuation capabilities of sensor networks consisting of static low-power nodes with narrowband (low data rate) measurements. Its benefits included improved energy efficiency and, as a result, extended operational lifetime. In conventional DBF systems, the destination node typically included a single antenna element.

[0022] When a destination node possesses more than a single antenna element, the degrees of freedom extend to that number, and spatial multiplexing is possible. The general theory is known by the broad term "MIMO" (multiple-input, multiple-output), which typically implies co-located transmit antennas and co-located receive antennas. Co-located transmit antennas can measure and utilize full channel matrix information (full "CSI"), in which case a process known as singular value decomposition (SVD) can be used to provide maximum capacity utilization. However, in a MIMO system, the number of (N T ,N R) A complete knowledge of the channel matrix is ​​essential for the implementation of SVD. With co-located transmit antennas, such information can be made available in a common baseband system at the transmitter. However, when the nodes (and their antennas) are distributed in space, sharing such information is burdensome. The channel gains need to be collected separately at the various nodes and then transmitted to a common processing center that implements SVD, and then the appropriate control information needs to be sent back to all transmitting nodes. Then, all transmitting nodes need to implement vector transmission (with SVD formulation) on a commonly known message, rather than just phasor adjustment of the transmit parameters. In general, SVD is considered cumbersome even for collocated transmit antennas, and is practically impossible in distributed systems. However, it is possible in principle and can be considered as an upper limit of the achievable performance. On the other hand, DBF implemented from a large number of transmitting nodes launching the same message towards a single antenna receiver via phasor adjustment can be proven to be simple and practical. The difference, of course, is that SVD achieves multiplexing of many streams (as many as the channel profile certainly allows), whereas DBF (described in Section 2) sends only one stream at a time.

[0023] The described embodiments are directed to spatially multiplexing different digital data streams generated in a distributed mobile ad-hoc network (MANET) and transmitted simultaneously towards a destination wireless device having multiple apertures or antennas (and denoted as a "receiving array"). As used herein, the term "distributed spatial multiplexing" (DSM) refers to any broad system of simultaneous multi-stream transmission in the context of a MANET due to the spatially distributed aspect of the transmitting MANET nodes. In DSM as illustrated in FIG. 1A, multiple data streams carrying different data (messages) are transmitted synchronously to a destination, which is capable of receiving and demultiplexing these multiple streams through appropriate processing due to the multiplicity of co-located receiving elements (antennas) at the destination site. In one example, the destination node supports two or more antennas, while the distributed transmitting wireless devices (nodes) each possess a single antenna. In another example, each transmitting node may possess two or more antennas.

[0024] The transmitter coordination and cooperation framework described herein allows multiple transmitters to cooperate in an open-loop fashion and transmit over a single antenna (N R This is based on DBF (described in Section 2) for the scenario in which all transmitters in a network send identical messages to destination receivers with the same QoS (i.e., QoS constraints). Each of the transmitters in Section 2 owns a common (single) data stream ("message") and transmits it to the destination receiver (node).

[0025] An embodiment of the disclosed technology is a multi-hop node having two or more antennas (N R >1) and N T We extend the distributed beamforming framework to include scenarios in which the transmitters collectively and simultaneously transmit two or more data streams. In one example, the number of streams is N R Furthermore, N T The transmitter transmits N rThe C antennas are first grouped into C clusters via a predefined protocol before using distributed beamforming (including some form of phase matching) within each cluster to transmit separate messages to corresponding ones of the C antennas. Figure 1B shows an example of clustered network nodes implementing clustered coherent distributed spatial multiplexing (CC DSM) for a receive array with multiple antennas. The described embodiment multiplexes two or more data streams simultaneously to advantageously provide enhanced sum rates over the channel versus single stream transmission.

[0026] Although the present disclosure considers clustered coherent distributed spatial multiplexing (CC DSM) in the context of MANETs where mobile nodes cooperate to communicate with separate antennas of a receiving array, the described embodiments are applicable to cellular systems (e.g., 3GPP, 4G, 5G, 5G-NR) where wireless devices (e.g., cell phones) cooperate to communicate with multiple antennas at a base station (e.g., eNB, gNB), and Wi-Fi networks (e.g., IEEE 802. family) where wireless devices cooperate to communicate with multiple antennas at a local router or Wi-Fi access point (AP). In addition, low power Internet of Things (IoT) applications can leverage the described embodiments to provide solutions for intelligent transportation networks, for example, to perform tasks including parking, autonomous driving, lane changing, etc.

[0027] 2. Exemplary Embodiment of DBF

[0028] In some embodiments, the wireless network nodes N are spatially distributed toward a remote cooperating wireless destination node D. i The method of distributed beamforming (DBF) from a set of i=1,2,...,K includes four steps.

[0029] Stage 1. Each network node owns a common message sent by a source S, which is a message to be beamformed towards a destination D.

[0030] Phase 2. The network nodes self-coherently through a sequence of bidirectional signaling exchanges (or a combination of signaling and message exchanges) between selected pairs of nodes, resulting in all nodes in the network being included in the self-coherence process and phase correction values ​​being derived and stored.

[0031] Phase 3. Each network node receives a broadcast probe signal from 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 timeslot or within adjacent timeslots).

[0032] Phase 4. Each network node quasi-synchronously (e.g., within a predefined turnaround time upon receiving the destination probe) transmits a common message with a total correction phase 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 phase 2) and the phase (argument) of the strongest complex-valued tap (estimated in phase 3).

[0033] In some embodiments, for constant envelope (CE) 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 characteristic of the transmitted signal.

[0034] In some embodiments, a network node may perform the four stages in a different order than that 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, calculate the phase of the strongest tap of the channel estimate (stage 3), then receive a common message (stage 1), subsequently join a self-coherence process with other network nodes to derive its phase correction value (stage 2), and finally perform the beamforming operation (stage 4). In another example, a network node may first join a self-coherence process with other network nodes to derive its phase correction value (stage 2), then receive a probe from the destination, calculate the phase of the strongest tap of the channel estimate (stage 3), subsequently receive a common message (stage 1), and finally perform the beamforming operation (stage 4).

[0035] In some embodiments, the four-step process described above results in a composite (co-transmitted, superimposed) signal at the destination node that has a greater signal-to-noise ratio (SNR) than would have been received if the nodes co-transmitted in a phase non-coherent manner, thereby resulting in distributed beamforming gain.

[0036] In some embodiments, the four-step process described above can be adapted to distribute a common message to multiple destinations simultaneously.

[0037] 2A-2D illustrate four stages of an exemplary embodiment for distributed cooperative beamforming in accordance with the disclosed technique.

[0038] 2A shows an example of a first message sharing stage in which K network nodes (shaded in grey) own a common message from a source (S). In some embodiments, the message can 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 can be broadcast by a source outside the network of K nodes (e.g., a drone or satellite broadcasts this common message to a terrestrial network, which can further relay the message to D that is otherwise not reachable by the source). In still other embodiments, the message can be shared over a backbone type network different from a wireless network (e.g., a high-speed optical network).

[0039] 2B illustrates an example of a second self-coherence stage. In some embodiments, the purpose of the self-coherence process is to: matrix

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[0040] matrix

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[0041] In some embodiments, the matrix

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[0042] In another embodiment, the matrix

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[0043] In yet another embodiment, the matrix

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[0044] The matrix in the above embodiment

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[0045] Bidirectional signal exchange. In some embodiments, node N i and N j A pure two-way exchange between node N i First, a signal, e.g. a tone-like probe, i.e.

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[0046] In complex envelope notation, a tone is

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[0047] In this exemplary purely two-way exchange, node N j is the baseband, full phase

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[0048] In some embodiments, the node N j can be notified of this value via a messaging protocol. j teeth,

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[0049] But in principle, in practice

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[0050] Message and signal exchange. In some embodiments, a mixture of signal exchange and message exchange may occur between nodes N i starts to send probes, and as mentioned above, node N j but

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[0051] In some embodiments, as described in the context of bidirectional signal exchange, a node may j The process can be repeated from the start of the

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[0052] 2C shows an example of a third phase estimation stage per node. In some embodiments, the destination node (D) broadcasts a probe, and each of the network nodes computes a tap-spaced complex-valued baseband channel model in response to receiving the probe from the destination node. At each node, the estimated tap magnitudes are compared and the largest one is selected, and then the argument (phase) estimate for each node i=1,2,...,K is calculated.

number

[0053] FIG. 2D illustrates an example of a fourth destination beamforming stage. In some embodiments, node N i The transmission from

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[0054] In some embodiments, the distributed cooperative beamforming process described in the context of Figures 2A-2D results in a destination node D receiving multiple taps. The taps arriving at D are (i) subjected to processing in stage 3, and then each node N i From the appropriate phase

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[0055] 2.1 Additional Embodiments of DBF

[0056] In some embodiments, all network nodes are fully connected. Since all nodes are within hearing range of the reference node, the selection of the reference node may be performed in the selected sequence, completing stage 2 with all nodes individually. The selection of the reference node may relate to the best average link SNR (averaged over all other nodes). More generally, any function (e.g., average, median, maximum, etc.) of the link quality metric (e.g., SNR, SINR, etc.) may be used in the network node selection decision. In this embodiment, it is further assumed that the link quality information is available to all nodes, and that all nodes share and periodically update it.

[0057] In some embodiments, the reference node may have good access to some but not all nodes of the network due to some poor quality links. The reference node may identify such impaired link nodes and request the help of neighboring nodes via appropriate messages (e.g., send a request for those neighboring nodes to conduct a bidirectional exchange with the impaired link node with more favorable link conditions and thus help complete the full reference sequence via said identification information).

[0058] In some embodiments, there may be information about the nature of the links (e.g., Line-of-Sight (Los) or Non-Loss (NLos)), which may be used by each node in the process of filling the phase matrix to determine which links should be used in its bidirectional exchanges (e.g., only Loss links may be used).

[0059] In some embodiments, the initial node may be selected randomly or via a quality metric (e.g., best link SNR between the nodes) and is called “node 1.” Node 1 is then assigned to a second node (“node 2”).

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[0060] In some embodiments, the individual terms

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[0061] In some embodiments, individual links may be subject to significant interference (e.g., due to jamming). The elements of the matrix corresponding to such corrupted links may be excluded from the two-way signal exchange (phase measurement) process. Instead, such elements may be filled in through the use of other measurements on the associated uncorrupted links and the aforementioned identities (e.g., trigonometric identities).

[0062] In some embodiments, a network node may use separate oscillator phases for transmit and receive modes.

[0063] In some embodiments, the term

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[0064] In some embodiments, the term

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[0065] In some embodiments, various methods may be employed in selecting the strongest channel tap for calculating the respective phase. In one example, the strongest channel tap is the maximum gain value directly among the taps. In another example, the complex channel tap is calculated via an interpolation method among the taps estimated using observed samples (measurements) of the channel estimation process.

[0066] 3. Exemplary embodiments of CC DSM

[0067] The CC DSM framework first supports N TIt is assumed that the transmitters are grouped into C clusters, each of which has a different data stream to transmit to the destination node. The different data streams are known to each node in that particular cluster, which may be achieved by sharing the specific different data streams (e.g., similar to the DBF operation described with reference to FIG. 2B). Following clustering, each cluster beamforms to a separate and distinct element of the receive array at the destination node (e.g., similar to the DBF operation described in Section 2 with reference to FIG. 2C and FIG. 2D). For example, cluster 1 performs DBF on antenna 1 of the receive array, cluster 2 performs DBF on antenna 2 of the receive array, and so on until all clusters are mapped to all receive elements. In one example, the mapping from clusters to receive elements may be predefined. In another example, the mapping is based on pairwise link quality (e.g., SNR, SINR) such that a certain utility metric (e.g., sum rate) is maximized. In yet another example, each antenna element is associated with a unique pilot or probe signal, and a cluster that identifies itself with a particular probe / pilot signal is consequently associated with that antenna element. However, the described embodiment requires that each cluster is mapped to a unique receiving element, i.e., two clusters with different messages are not mapped to the same receiving element.

[0068] In some embodiments, cluster formation is static, e.g., node membership is pre-determined, while in other embodiments, cluster formation is dynamic. In one example, clusters may be formed based on link quality and / or message availability between nodes, e.g., nodes that can "listen" to a particular source are part of the same cluster. Alternatively, if one or more nodes can listen to multiple messages, different protocols can be used to allocate nodes to clusters. In one example, nodes are allocated such that differences in cardinality are minimized (i.e., clusters are approximately equal size per node count). In another example, the protocol is based on average SNR per cluster, i.e., nodes are allocated as a function of the SNR they create at the destination, such that each cluster (message) corresponds to a similar SNR. In yet another example, node allocation to clusters is performed to maximize angular separation between clusters relative to the destination, using available location information, e.g., location information provided by a positioning system, e.g., GPS.

[0069] In some embodiments, the clustering step may be performed using a control channel, and the transmission of the phase alignment messages may be over a data channel that is different from the control channel. In other embodiments, the various metrics (e.g., both local and remote sensing observables) used to determine the optimal cluster for the transmitting node may be accessible through an application programming interface (API) that advantageously allows third parties to use the underlying CC DSM framework in certain scenarios.

[0070] With respect to simultaneous joint transmission of a message by a cluster to a destination node having multiple receiving elements, the power allocated to cooperating nodes in the cluster may be determined in several ways.

[0071] In one example, the total power used by all cooperating nodes in a cluster is limited to a predefined amount that is the same for all clusters. Herein, a reference node (or cluster head) is a node that is connected to the cluster by a certain number of nodes in the cluster (N t,i ) to all nodes in the cluster, and each node receives 1 / N of its maximum power. t、i , so that the power transmitted by each cluster is constant (and does not depend on the number of nodes per cluster).

[0072] In another example, the total power used by all cooperating nodes in a cluster is not constrained. Herein, each cluster uses a total transmit power that is simply the sum of the transmit powers of the individual nodes in that cluster, and each node is configured to transmit at maximum power when using a continuous phase modulation (CPM) waveform. If another waveform is used, the transmit power can be adjusted (e.g., backed off) accordingly.

[0073] 3.1 Example of RF communication model for CC DSM

[0074] In some embodiments, a network implementing a CC DSM includes N T In addition to the spatially distributed single-antenna transmitters, multiple (N R The system includes a privileged destination receiver with C (number of) antennas. The transmitters are grouped into C clusters such that each cluster owns a different data stream (message). The clusters may represent separate subnets of the network, and source nodes in each cluster emit messages that are heard by nodes in that cluster, for example by broadcast transmission. Alternatively, the messages for each cluster may be different segments of a data stream generated by a single source node and are available to all sending nodes in the network.

[0075] As an example, and to deploy various aspects of the disclosed technology, the number of clusters is equal to the number of destination receive antennas, i.e., C=N R and for simplicity, each cluster is exactly

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[0076] Figure 3 shows the C=N R =4 and

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[0077] The propagation channel is assumed to be either a narrowband signal that does not resolve RF reflections, or frequency-nonselective, representing the individual subcarriers of a wideband multi-carrier signal such as OFDM. Using complex baseband equivalent notation, the line-of-sight (LoS) component of the propagation channel from transmitter t to destination antenna r is:

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[0078] During the ceremony,

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[0079] is the loss angle of arrival (AoA),

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[0080] During the ceremony,

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[0081] is the AoA component of the mth NLos component (the difference with the Loss component is

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[0082] where κ≧0 is the Rice coefficient.

[0083] Baseband modulation symbol x of transmitter t t undergoes frequency up-conversion, RF channel conversion (6), and frequency down-conversion before digitization at the destination. Thus, the overall (baseband-to-baseband) channel between the transmitter digital chain and the destination radio is:

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[0084] In the formula, θ t is the phase of the local carrier generated by transmitter t, independently across transmitters, and θ D is the phase of the local carrier generated by the destination wireless device, common to the receive chains associated with each antenna (eg, defined relative to the start of the codeword on transmit and receive).

[0085] In the case of clustered DSM, the vector of co-transmitted modulation symbols

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[0086] In the formula, s=[s1,...,s C ] T is a vector of data symbols, one per stream per cluster,

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[0087] is |(P DSM )t,c |=1 (t∈c) is the distributed precoding matrix of . We define the overall uplink channel as

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[0088] The complex baseband signal model for the clustered DSM is:

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[0089] During the ceremony,

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[0090] is the overall DSM channel experienced by the vector of data symbols s,

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[0091] Assuming uniform emitted power across the distributed transmitters, P s Let t denote the average received signal power at each destination antenna due to a single transmission. The average signal-to-noise ratio (SNR) of the link between transmitter t and destination antenna r is: Link-SNR=P s / P w (14)

[0092] When the individual transmissions are subjected to uncorrelated channels, the SNR experienced by any single data stream (denoted Stream-SNR and upper bounded by the SNR experienced by each stream at the output of any spatial filtering for stream separation) is:

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[0093] The described embodiment adapts the standard DBF for a single receive antenna to the case of multiple receive antennas, with the transmitters in each cluster forming coherent beams targeting different elements of the destination array. The distributed precoding matrix associated with the CC DSM is:

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[0094] During the ceremony,

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[0095] As can be seen in (17) above, the non-coherent gain is available to all other receiver apertures outside the beam.

[0096] Baseband phase rotation, also called DBF phase calibration

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[0097] The above CC DSM formulation allows us to compare the performance of the CC DSM with other existing cooperative communication implementations, as described in Section 3.3, where the CC DSM is compared with the Clustered Non-coherent DSM (CI-DSM) and Distributed Singular Value Decomposition (D-SVD).

[0098] In some embodiments, the CC DSM is configured to use an exemplary frame structure shown in Figure 4A. As shown therein, the frame structure of the CC DSM includes a network control time slot (denoted as "Net ctrl") used for scheduling, time and / or frequency synchronization, and / or clustering, a message sharing time slot (similar to the DBF time slot shown in Figure 2B), a DBF control time slot (denoted as "DBF ctrl") used by nodes in a cluster to receive probes (or more generally, downlink signals) from a destination node, and an uplink transmission time slot for uplink beamformed co-transmissions from each of the C clusters. As shown in Figure 4A, each beamformed co-transmission from a cluster includes a probe (e.g., a separate sequence per cluster used for channel estimation by the destination node), a header (e.g., for cluster id and message id), and a message (e.g., encoded source data).

[0099] In some embodiments, downlink probes (e.g., from a destination node in a "DBF ctrl" time slot to a node in a cluster) are associated with a cluster and / or spatial stream. In one example, this may be achieved implicitly based on a TDMA schedule (or any "round robin" schedule) in a time division multiple access (TDMA) system. In another example, this may be achieved implicitly by using different probes issued by each of the different antennas (e.g., using simultaneous orthogonal codes or orthogonal training sequences). In yet another example, this may be achieved explicitly by a downlink transmission that includes a short message indicating the cluster ID (or equivalently, the issuing antenna ID) in addition to the probe.

[0100] 3.2 Downlink Transmission in the CC DSM Framework

[0101] In certain operating scenarios, separate messages from each of multiple clusters need to be delivered to each of the other clusters. In these cases, the uplink CC DSM framework described above can be combined with downlink transmissions from a destination node with multiple antennas.

[0102] In a simple implementation that does not utilize the CC DSM embodiments described herein, each of the C clusters uses a separate time slot to send its message to the destination node, thereby requiring C time slots. The destination node then uses C time slots to broadcast each of the messages in its own time slot. Thus, a simple implementation uses 2×C time slots.

[0103] Alternatively, the C clusters use CC DSM to send all messages to the destination node in a single time slot, and the destination node then broadcasts each message in its own time slot (as in the case above) using C time slots. This implementation, leveraging the CC DSM implementation described herein and using the frame structure shown in Figure 4B (which shows only one of the C time slots used by the destination node), requires C+1 time slots.

[0104] Alternatively, the C clusters use CC DSM (as above) to send messages to the destination node in a single time slot, and the destination node then uses one time slot to beamform each source message to the remaining (non-source) C-1 clusters individually. This implementation also requires C+1 time slots, but each cluster receives messages of other clusters with a higher fidelity metric, e.g., higher SNR, than the previous alternative.

[0105] 3.3 Numerical results illustrating the effectiveness of CC DSM

[0106] The performance of the described CC DSM embodiments is compared to that of Clustered Non-coherent DSM (CI-DSM), Distributed Singular Value Decomposition (D-SVD), and Barrage Relay networking (BRn).

[0107] BRn is a communication protocol in which wireless devices cooperate autonomously by relaying common messages received and decoded at the previous hop, providing spatial diversity in the form of non-coherent co-transmission of a single message stream. Details of the BRn framework and example implementations can be found at least in U.S. Patent Nos. 8,964,629, 8,588,126, 8,897,158, 9,054,822, and 9,629,063.

[0108] In CI-DSM, the cluster distributes each data stream to N R The precoding matrix for CI-DSM is:

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[0109] This results in the overall DSM channel matrix being:

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[0110] In the formula, g r,t is the propagation channel of (6). Note that beyond message sharing and network time / frequency synchronization, CI-DSM incurs no overhead.

[0111] D-SVD is a fictitious protocol that provides an upper bound on the performance of CC-DSM. It computes the singular value decomposition (SVD) of the entire uplink channel (10).

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[0112] where v i and u i are orthogonal sets of eigenvectors for the transmitter and receiver, respectively, and the corresponding nonzero singular values ​​{λ i}, and λ i ≧λ i+1 >0. Mimicking a MIMO system with co-located transmit apertures, the D-SVD protocol transmits each of the C distinct data streams on a different spatial eigenmode. The overall channel for D-SVD is

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[0113] It can be derived as follows, through which the C data streams are received without crosstalk. Note that unlike the CC DSM, all senders in the D-SVD protocol have access to all C data streams, perform message mixing, and are required to exhibit the maximum level of diversity of user cooperation.

[0114] 5A-5D are exemplary numerical results comparing the performance of the CC DSM with the CI-DSM and D-SVD in several exemplary scenarios consisting of:

[0115] (i) Number C, and orientation

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[0116] (ii) Number per cluster

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[0117] (iii) a channel model specified via the Rice coefficient, κ, that is applied uniformly across each link according to (6); and

[0118] (iv) A finite alphabet of data symbols for each stream.

[0119] Associated with each scenario is a distribution of the entire channel as a function of the distribution of the remaining system parameters that are randomized across the channel instances. In all scenarios, the destination wireless device receives the signal at a normalized interval Δ R = 1 / 2 N R = C antennas. In the case of CC DSM, cluster c beamforming is performed with destination aperture c, i.e., r c =C.

[0120] The main metric for the performance comparison is the ε-outage capacity. The outage capacity results are complemented by coded block error rate (BLER) estimates from simulations using a quasi-static model of the channel application. The performance differences are explained through the statistics of two auxiliary metrics: the energy metric

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[0121] describes the energy per data stream, and the rank metric

number

[0122] shows the relative strength of the spatial eigenmodes across the DSM channel. Figures 5A-5D correspond to scenarios 1-4, respectively.

[0123] Scenario 1 consists of C=2 clusters (with two nodes per cluster), cluster separation of 60° and 120°, strong LoS condition defined by κ=10 dB, and QPSK signal set. Figure 5A displays the outage capacity and BLER as a function of link SNR. CC DSM performs similarly to D-SVD with nearly the same energy and rank statistics as shown by Table I. In comparison, CI-DSM suffers rank and energy loss, affecting both the slope and shift of the performance curve. The BRn protocol, which delivers a single spatial stream to all four transmitters, enjoys limited diversity due to the strong LoS nature of the link. [Table 1]

[0124] Scenario 2 differs from Scenario 1 only in the channel model, which assumes weak LoS conditions with κ = -10 dB. Figure 5B displays the outage capacity and BLER as a function of link SNR. While CC-DSM performs within a few dB of the theoretical D-SVD, both schemes suffer rank loss relative to Scenario 1, as shown in Table II. [Table 2]

[0125] Scenario 3 reconstructs Scenario 2 with cluster separations of 75° and 105°. As a result of the reduced cluster separation, all DSM variants rank worse, as shown in Table III. Figure 5C shows that CC-DSM still performs within a few dB of D-SVD. [Table 3]

[0126] Scenario 4 is for a cluster

number

[0127] As shown in Figures 5A-5D and discussed above, the CC DSM yields higher multiplexing gain (more messages relayed per channel usage) than plain noncoherent co-transmission of a single message, effectively capturing the receiver aperture degrees of freedom. The CC DSM gain is nearly comparable to the global idealization gain of SVD, demonstrating that it is a simple, yet highly effective means of realizing the broader vision of virtual MIMO in distributed ad-hoc networks.

[0128] 4. Exemplary implementations of the disclosed technology

[0129] 6 illustrates a flowchart of an example method for cooperative communication. The method 600 includes grouping a plurality of nodes into a plurality of clusters, at operation 610. Various mechanisms used to group the nodes into clusters are described in Section 3.

[0130] The method 600 includes receiving, by a node in the cluster, a probe from a corresponding one of a plurality of antennas at the destination node, at operation 620. In one example, this is similar to stage 3 of the DBF described in Section 2 with reference to FIG.

[0131] The method 600 includes, at operation 630, generating, by the nodes in the cluster, a separate message by applying a phase correction to the message, the phase correction being calculated based on the probe.

[0132] The method 600 includes simultaneously transmitting, by the nodes of each cluster, a separate message directed to a corresponding one of the multiple antennas, at operation 640. The simultaneous transmission is based on the clusters implementing distributed beamforming, as detailed in Section 2.

[0133] 7 shows a flowchart of another exemplary method for cooperative communication. The method 700 includes, at operation 710, clustering a plurality of nodes into a plurality of clusters, such that each of the plurality of clusters communicates with a separate antenna of the plurality of antennas. Various mechanisms used to group the nodes into clusters are described in Section 3.

[0134] The method 700 includes, at operation 720, performing distributed beamforming in each of the plurality of clusters to transmit corresponding ones of the plurality of messages directed to the separate antennas. The performance of beamforming is described in more detail in Section 2.

[0135] The described embodiments provide, inter alia, the following technical solutions:

[0136] 1. A method for cooperative communication comprising: a plurality of nodes; and a destination node having a plurality of antennas; the system is configured to group the plurality of nodes into a plurality of clusters such that each of the plurality of clusters is configured to simultaneously transmit a separate message directed to a corresponding antenna of the plurality of antennas; and each node in each of the plurality of clusters is configured to receive a probe from a corresponding antenna and generate a corresponding separate message by applying a phase correction before transmitting the corresponding separate message, the method comprising: calculating a phase correction based on the probe.

[0137] 2. The system of solution 1, wherein grouping the nodes into clusters is based on the average signal-to-noise ratio (SNR) of each cluster.

[0138] 3. The system of solution 1, wherein grouping multiple nodes into multiple clusters is based on the angular separation between each cluster and the destination node.

[0139] 4. The system according to solution 3, where the angular separation is based on the angle between a given node and the destination node in the cluster.

[0140] 5. The system of solution 4, where the given node is the node closest to the geographic center of the cluster.

[0141] 6. The system of solution 4, wherein the predetermined node is determined based on the location of each node in the cluster and the location of the corresponding antenna.

[0142] 7. The system of Solution 1, wherein grouping multiple nodes into multiple clusters is based on minimizing the difference between the sizes of the multiple clusters.

[0143] 8. A system described in any one of Solutions 1 to 7, wherein the multiple clusters include a first cluster that sends a first message and a second cluster that sends a second message.

[0144] 9. The system of solution 8, wherein the first message is from a first source and the second message is from a second source different from the first source.

[0145] 10. The system of solution 8, wherein the first message is a first part of a common message from a source, and the second message is a second part of the common message that does not overlap with the first part of the common message.

[0146] 11. The system according to any one of solutions 1 to 7, wherein grouping multiple nodes into multiple clusters uses a control channel.

[0147] 12. The system according to solution 11, wherein transmitting the corresponding separate message uses a data channel that is different from the control channel.

[0148] 13. A system according to any one of solutions 1 to 7, wherein each of the multiple nodes is a mobile node in an ad hoc network and the destination node is a receiving array including multiple antennas.

[0149] 14. A system according to any one of solutions 1 to 7, wherein each of the plurality of nodes is a wireless cellular device and the destination node is a base station.

[0150] 15. The system according to solution 14, wherein the base station is an eNodeB (eNB), a gNodeB (gNB), an en-gNB, or an ng-eNB.

[0151] 16. A system described in any one of Solutions 1 to 7, wherein each of the multiple nodes is a wireless device using a Wi-Fi protocol and the destination node is a Wi-Fi router or a Wi-Fi access point (AP).

[0152] 17. A method for cooperative communication from a plurality of nodes to a destination node equipped with a plurality of antennas, the method including: clustering the plurality of nodes into a plurality of clusters, such that each of the plurality of clusters communicates with a distinct antenna of the plurality of antennas; and performing distributed beamforming in each of the plurality of clusters to transmit a corresponding message of a plurality of messages directed to the distinct antenna.

[0153] 18. The method of solution 17, wherein performing distributed beamforming includes receiving a probe from a corresponding separate antenna by each of a plurality of clusters, and a corresponding message is generated by applying a phase correction, and calculating the phase correction is based on the probe.

[0154] 19. The method of solution 17, wherein the multiple messages include multiple non-overlapping portions of a common message.

[0155] 20. The method of solution 17, further comprising receiving, by the destination node, a plurality of messages from a plurality of clusters in the first time slot.

[0156] 21. The method of solution 20, wherein a destination node receives a plurality of messages by receiving a corresponding message from each of a plurality of clusters in a first time slot.

[0157] 22. The method of solution 20, wherein the number of clusters is an integer C greater than or equal to 2, the number of messages is C, and the number of antennas is an integer NR greater than or equal to C.

[0158] 23. The method of solution 22, further comprising transmitting, from a destination node, a corresponding one of the C plurality of messages to the multiple clusters in each of the C time slots following the first time slot by broadcasting the corresponding message using the NR antennas.

[0159] 24. The method of solution 22, wherein the plurality of messages includes a first message received from a first cluster, and the method further includes transmitting, from the destination node, the first message to at least one of the plurality of clusters in a second time slot following the first time slot.

[0160] 25. The method of solution 24, wherein NR is equal to C, and transmitting the first message includes using NR antennas to broadcast the first message to each of the multiple clusters.

[0161] 26. The method of solution 24, wherein NR is equal to K×C, C is equal to 3, the plurality of messages further includes a second message received from the second cluster and a third message received from the third cluster, and transmitting the first message further includes operating the first K antennas in a first directional mode to transmit the first message to the second cluster, and the method further includes transmitting the second message to the third cluster by operating the second K antennas in the second directional mode in a second time slot, and transmitting the third message to the first cluster by operating the third K antennas in a third directional mode in the second time slot.

[0162] 27. A method according to any one of Solutions 17 to 26, wherein (a) each of the plurality of nodes is a mobile node in an ad-hoc network and the destination node is a receiving array including multiple antennas, or (b) each of the plurality of nodes is a wireless cellular device and the destination node is a base station, or (c) each of the plurality of nodes is a wireless device using a Wi-Fi protocol and the destination node is a Wi-Fi router or a Wi-Fi access point (AP).

[0163] 28. A method of cooperative communication implemented using a system according to one or more of solutions 1 to 16.

[0164] 29. An apparatus for wireless communication comprising a processor configured to implement the methods described in one or more of solutions 17 to 27.

[0165] 30. A non-transitory computer-readable program storage medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a method as described in one or more of Solutions 17 to 27.

[0166] 8 is a block diagram representation of a portion of a wireless device according to some embodiments of the techniques of this disclosure. The wireless device 811 may include processor electronics 801, such as a microprocessor, that implements one or more of the techniques (including, for example, methods 600 and 700) presented in this patent document. The wireless device 811 may include transceiver electronics 803 for transmitting and / or receiving wireless signals by one or more communication interfaces, such as an antenna 809. The wireless device 811 may include other communication interfaces for transmitting and receiving data. The wireless device 811 may include one or more memories 807 configured to store information, such as data and / or instructions. In some implementations, the processor electronics 801 may include at least a portion of the transceiver electronics 803. In some embodiments, at least some of the disclosed techniques, modules, or functions are implemented using the wireless device 811.

[0167] Implementations of the subject matter and functional operations described in this patent document can be implemented in various systems, digital electronic circuits, or in computer software, firmware, or hardware, or a combination of one or more of them, including the structures disclosed herein and their structural equivalents. Implementations of the subject matter described herein can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible and non-transitory computer-readable medium for execution by or for controlling the operation of a data processing device. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter affecting a machine-readable propagated signal, or a combination of one or more of them. The term "data processing unit" or "data processing device" encompasses all apparatus, devices, and machines for processing data, including, as examples, a programmable processor, a computer, or multiple processors or multiple computers. An apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, such as code that constitutes a processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0168] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including standalone programs or modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in several coordinated files (e.g., files that store one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer, or on several computers located at one site or distributed across several sites and interconnected by a communication network.

[0169] The processes and logic flows described herein may be implemented by one or more programmable processors executing one or more computer programs to perform functions by manipulating input data and generating output. The processes and logic flows may also be implemented by, and an apparatus may be implemented as, special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0170] Processors suitable for executing computer programs include, by way of example, both general purpose and special purpose microprocessors, as well as any one or more processors of any kind of digital computer. Generally, a processor receives instructions and data from a read-only memory or a random access memory, or both. The essential elements of a computer are a processor for carrying out instructions and one or more memory devices for storing instructions and data. Generally, a computer also includes one or more mass storage devices, such as magnetic disks, magneto-optical disks, or optical disks, for storing data, or is operatively coupled to receive data from or transfer data to them, or both. However, a computer need not have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, by way of example, semiconductor memory devices, such as EPROM, EEPROM, flash memory devices. The processor and memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0171] Although this patent document contains many details, these should not be construed as limitations on any invention that may be claimed or on the scope of what may be claimed, but rather as descriptions of features that may be specific to certain embodiments of a particular invention. Certain features described in this patent document in the context of separate 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 even initially be claimed as such, one or more features from a claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0172] Similarly, although operations are shown in the figures in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown, or in any sequential order, or that all of the illustrated operations be performed, to achieve desired results. Further, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.

[0173] Only some implementations and examples have been described; other implementations, extensions, and variations can be made based on what is described and illustrated in this patent document.

Claims

1. 1. A system for cooperative communication, comprising: A plurality of nodes; a destination node equipped with a plurality of antennas; The system comprises: configured to group the plurality of nodes into a plurality of clusters, each cluster configured to simultaneously transmit a distinct message directed to a corresponding one of the plurality of antennas; each node in each of the plurality of clusters, before transmitting a corresponding separate message; receiving a probe from the corresponding antenna; 10. A system configured to generate the corresponding separate message by applying a phase correction, wherein calculating the phase correction is based on the probe.

2. The system of claim 1 , wherein the grouping of the plurality of nodes into the plurality of clusters is based on an average signal-to-noise ratio (SNR) of each cluster.

3. grouping the plurality of nodes into the plurality of clusters based on an angular separation between each cluster and the destination node; The angular separation is based on an angle between a given node in a cluster and the destination node, the given node being (a) the node closest to the geographic center of the cluster; or (b) determined based on the location of each node in the cluster and the location of the corresponding antenna; is one of the nodes The system of claim 1 .

4. The system of claim 1 , wherein grouping the plurality of nodes into the plurality of clusters is based on minimizing differences between sizes of the plurality of clusters.

5. The system of claim 1 , wherein the plurality of clusters includes a first cluster that sends a first message and a second cluster that sends a second message.

6. 6. The system of claim 5, wherein the first message is (a) from a first source and the second message is from a second source different from the first source, or (b) is a first portion of a common message from a source and the second message is a second portion of the common message that does not overlap with the first portion of the common message.

7. The system of claim 1 , wherein grouping the plurality of nodes into the plurality of clusters uses a control channel.

8. The system of claim 7 , wherein transmitting the corresponding separate message uses a data channel that is different from the control channel.

9. The system of claim 1 , wherein each of the plurality of nodes is a mobile node in an ad hoc network, and the destination node is a receiving array including the plurality of antennas.

10. 2. The system of claim 1, wherein each of the plurality of nodes is a wireless cellular device, the destination node is a base station, and the base station is an eNodeB (eNB), a gNodeB (gNB), an en-gNB, or an ng-eNB.

11. The system of claim 1 , wherein each of the plurality of nodes is a wireless device using a Wi-Fi protocol, and the destination node is a Wi-Fi router or a Wi-Fi access point (AP).

12. 1. A method for cooperative communication from multiple nodes to a destination node equipped with multiple antennas, the method comprising: clustering the plurality of nodes into a plurality of clusters, each cluster communicating with a distinct antenna of the plurality of antennas; performing distributed beamforming in each of the plurality of clusters to transmit corresponding messages of the plurality of messages directed to the distinct antennas; performing the distributed beamforming includes receiving, by each of the plurality of clusters, a probe from a corresponding separate antenna; the corresponding message is generated by applying a phase correction, and calculating the phase correction is performed based on the probe. method.

13. The method of claim 12 , wherein the plurality of messages comprises multiple non-overlapping portions of a common message.

14. The method of claim 12 , further comprising receiving, by the destination node, the plurality of messages from the plurality of clusters in a first time slot.

15. 15. The method of claim 14, wherein the destination node receives the plurality of messages by receiving the corresponding message from each of the plurality of clusters in the first time slot.

16. The number of the plurality of clusters is an integer C equal to or greater than 2, the number of the plurality of messages is C, and the number of the plurality of antennas is an integer N equal to or greater than C. Ｒ The method of claim 14, wherein

17. N Ｒ 17. The method of claim 16, further comprising transmitting, from the destination node, a corresponding one of the C messages to the plurality of clusters in each of C time slots following the first time slot by broadcasting the corresponding message using the antennas.

18. the plurality of messages includes a first message received from a first cluster, and the method further comprises:

17. The method of claim 16, further comprising transmitting the first message from the destination node to at least one of the plurality of clusters in a second time slot subsequent to the first time slot.

19. N Ｒ is equal to C, and the transmitting the first message comprises: Ｒ 20. The method of claim 18, comprising using antennas.

20. and transmitting the first message to the N clusters such that C-1 beams are formed to transmit the first message to each of the plurality of clusters other than the first cluster. Ｒ 20. The method of claim 18, comprising operating an antenna.

21. (a) each of the plurality of nodes is a mobile node in an ad hoc network, and the destination node is a receiving array including the plurality of antennas; or (b) each of the plurality of nodes is a wireless cellular device and the destination node is a base station; or 13. The method of claim 12, wherein (c) each of the plurality of nodes is a wireless device using a Wi-Fi protocol, and the destination node is a Wi-Fi router or a Wi-Fi access point (AP).

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