Open-Loop Distributed Beamforming Using Wireless Frequency Synchronization

Mghabghab, Serge R.; Nanzer, Jeffrey A.

doi:10.1109/tmtt.2020.3022385

Cited by 37 publications

(11 citation statements)

References 33 publications

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“…However, closedloop methods are only suitable for scenarios where such meaningful feedback is available from the destination, for instance, in communication applications, thus limiting its ability to arbitrary steer the beam to any destination. On the other hand, in the open-loop methods, such as the synchronization methods in [12]- [15], the nodes coordinate with each other to synchronize their transceivers without using any feedback from the destination. As such, the open-loop methods are also suitable for the remote sensing [16], [17] and radar applications [18].…”

Section: Introductionmentioning

confidence: 99%

“…For open-loop CDAs, a centralized topology based transceiver synchronization method is proposed in [15], [19] where a primary node transmits a reference signal to one or more secondary nodes, and the secondary nodes use a frequency locking circuit with the phase-locked loops to synchronize with the primary node. A drawback of this primary-secondary architecture is that it fails whenever the primary node fails.…”

Section: Introductionmentioning

confidence: 99%

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Frequency and Phase Synchronization in Distributed Antenna Arrays Based on Consensus Averaging and Kalman Filtering

Rashid¹,

Nanzer²

2022

Preprint

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A decentralized approach for joint frequency and phase synchronization in distributed antenna arrays is presented. The nodes in the array locally broadcast signals to share their frequencies and phases with their neighboring nodes, and use consensus averaging to align these parameters across the array. The architecture is fully distributed, requiring no centralization. Each node has a local oscillator and we consider a signal model where intrinsic frequency and phase errors of the local oscillators on each node caused by the frequency drift and phase jitter as well as the frequency and phase estimation errors at the nodes are included and modeled using practical statistics. A decentralized frequency and phase consensus (DFPC) algorithm is proposed which uses an average consensus method in which each node in the array iteratively updates its frequency and phase by computing an average of the frequencies and phases of their neighboring nodes. Simulation results show that upon convergence the DFPC algorithm can align the frequencies and phases of all the nodes up to a residual phase error that is governed by the oscillators and the estimation errors. To reduce this residual phase error and thus improve the synchronization between the nodes, a Kalman filter based decentralized frequency and phase consensus (KF-DFPC) algorithm is presented. The total residual phase error at the convergence of the KF-DFPC and DFPC algorithms is derived theoretically. The synchronization performances of these algorithms are compared to each other in light of this theoretical residual phase error by varying the duration of the signals, connectivity of the nodes, the number of nodes in the array, and signal to noise ratio of the transmitted signals. Simulation results demonstrate that the proposed KF-DFPC algorithm Manuscript received 2022.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Frequency and Phase Synchronization in Distributed Antenna Arrays Based on Consensus Averaging and Kalman Filtering

Rashid¹,

Nanzer²

2022

Preprint

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“…Wireless frequency synchronization has been achieved using bursts of synchronization packets [17], coupled-oscillators [18], optically-locked voltage controlled oscillators [19], and global positioning system (GPS) phase information [20], among other approaches. Here we consider a general architecture where PLLs are used to synchronize the frequency on a set of secondary nodes to a reference signal transmitted by a primary node [11], [24], [25]. Specifically, we are interested in both topologies, open-loop and closed-loop, that fit the model in Fig.…”

Section: Reference Pll Secondarymentioning

confidence: 99%

“…It is assumed that the antennas used for wireless frequency synchronization are not used for other wireless functions in this work; beamforming could be implemented with the same antennas or could use separate antennas. The frequency synchronization signals are considered as both continuous wave (CW) and pulsed signals which can be generated using the approach described in [11], [24], [25], where an adjunct self mixing circuit is used to demodulate a 10 MHz reference signal from a CW two-tone signal. The coherent gain is investigated for array sizes of N = 2, 10, 20, and 100 for the case where phase, frequency, and timing errors are present.…”

Section: Reference Pll Secondarymentioning

confidence: 99%

“…In either topology, there are many factors that influence the ability to coherently transmit a signal from a collection of separate nodes, involving the system hardware, the internode coordination, and the environment. Coordination errors are critical, and have been studied extensively, for instance relating to time synchronization [9], [10] and frequency synchronization in closed-loop distributed beamforming [5]- [7], [12]- [14], and in open-loop distributed beamforming [11]. In some of the closed-loop approaches referenced above, channel errors are also corrected; for open-loop systems, far-field beamforming in media that varies little over the domain of the nodes can mitigate the effects of channel differences.…”

Section: Introductionmentioning

confidence: 99%

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Impact of VCO and PLL Phase Noise on Distributed Beamforming Arrays With Periodic Synchronization

Mghabghab

Nanzer

2021

IEEE Access

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Distributed beamforming between separate wireless nodes in a distributed antenna array requires significant coordination of the relative electrical states of the systems to achieve and maintain a phase-coherent state. A principal factor impacting distributed phase coherence is the relative stability of the local oscillators on each node. Ensuring a coherent state requires the distribution of a reference frequency such that all nodes are operating on the same basis frequency. To support distributed beamforming, the reference frequency must furthermore be distributed wirelessly, typically using a phase-locked loop (PLL) on the secondary nodes. In large arrays, the wireless link used for frequency distribution will have limited capacity, necessitating intermittent updates during which the oscillators are locked, and between which their frequencies will drift. The stability of the oscillator therefore plays an important role in the overall performance relative to the update time. In this paper, we discuss the sources of phase noise generated by the reference oscillator and the PLL, and analyze the impacts of phase noise and update interval on distributed beamforming performance. We provide a framework for analyzing distributed beamforming performance from oscillator and PLL parameters in general, and we analyze beamforming performance for two specific cases using nominal high-quality and low-quality voltage-controlled oscillators, with parametric comparison between their impact on beamforming performance.

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Time and phase synchronization using clutter observations in airborne distributed coherent aperture radars

Chen

Wang

Liu

et al. 2022

Chinese Journal of Aeronautics

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Open-Loop Distributed Beamforming Using Wireless Frequency Synchronization

Cited by 37 publications

References 33 publications

Frequency and Phase Synchronization in Distributed Antenna Arrays Based on Consensus Averaging and Kalman Filtering

Frequency and Phase Synchronization in Distributed Antenna Arrays Based on Consensus Averaging and Kalman Filtering

Impact of VCO and PLL Phase Noise on Distributed Beamforming Arrays With Periodic Synchronization

Time and phase synchronization using clutter observations in airborne distributed coherent aperture radars

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