Decentralized Frequency Synchronization in Distributed Antenna Arrays With Quantized Frequency States and Directed Communications

Ouassal, Hassna; Rocco, Torre; Yan, Ming; Nanzer, Jeffrey A.

doi:10.1109/tap.2020.2977751

Cited by 25 publications

(14 citation statements)

References 31 publications

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“…A drawback of this primary-secondary architecture is that it fails whenever the primary node fails. Thus the authors in [12], [13] proposed a decentralized algorithm for nodes synchronization in open-loop CDAs. The decentralized topology overcomes the shortcomings of the centralized one, and makes the system easily scalable.…”

Section: Introductionmentioning

confidence: 99%

“…The decentralized topology overcomes the shortcomings of the centralized one, and makes the system easily scalable. However, the work in [12], [13] only considered frequency synchronization of the oscillators in open-loop CDAs, whereas in practice the phases of the oscillators also undergo random drift and phase jitter over time and thus need to be synchronized as well.…”

Section: Introductionmentioning

confidence: 99%

“…Joint frequency and phase synchronization is also considered in [22], [23], but the proposed methods do not synchronize the frequencies and phases of the nodes to the average of their initial values. Average consensus is a decentralized algorithm used in [12], [13], [24] for frequency synchronization that requires iterative exchanges between the nodes to reach a globally agreed upon value which is the average of their initial values. We use this algorithm herein to synchronize the frequencies and phases of the nodes in an open-loop CDA.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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%

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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“…Coherent distributed arrays (CDAs) are a particular form of distributed wireless system where individual wireless elements coordinate at the level of the radio frequency (RF) phase to enable distributed beamforming [6], [11], [12]. Coordination of separate moving nodes is a challenging problem, in which the following three fundamental coordination tasks must be accomplished: frequency synchronization to ensure all elements are operating at the same reference frequency [13]- [16]; time alignment to ensure that there is sufficient overlap of the information at the target destination [17]- [19]; and phase alignment to enable constructive interference at the target. Phase alignment presents the most challenges due to the extremely small tolerance to errors at microwave frequencies.…”

Section: Introductionmentioning

confidence: 99%

Multi-Node Open-Loop Distributed Beamforming Based on Scalable, High-Accuracy Ranging

2022

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We present a distributed antenna array supporting open-loop distributed beamforming at 1.5 GHz. Based on a scalable, high-accuracy internode ranging technique, we demonstrate open-loop beamforming experiments using three transmitting nodes. To support distributed beamforming without feedback from the destination, the relative positions of the nodes in the distributed array must be known with accuracies below λ/15 of the beamforming carrier frequency to ensure that the array maintains at least 90% coherent beamforming gain at the receive location. For operations in the microwave range, this leads to range estimation accuracies of centimeters or lower. We present a scalable, high-accuracy waveform and new approaches to refine range measurements to significantly improve the estimation accuracy. Using this waveform with a three-node array, we demonstrate high-accuracy ranging simultaneously between multiple nodes, from which phase corrections on two secondary nodes are implemented to maintain beamforming with the primary node, thereby supporting open-loop distributed beamforming. Upon movement of the nodes, the range estimation is used to dynamically update the phase correction, maintaining beamforming as the nodes move. We show the first openloop distributed beamforming at 1.5 GHz with two-node and three-node arrays, demonstrating the ability to implement and maintain phase-based beamforming without feedback from the destination.

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“…Among the synchronization signals, frequency locking and phase alignment have the most stringent requirements [20], and are the focus of this work. In other works, wireless frequency synchronization has been achieved in various ways, including using coupled-oscillators [21], optically-locked voltage controlled oscillators [22], and trading of data packets [8], [23], [24], among others. These techniques, however, are either not feasible for long inter-node separations, have discretization errors which contribute to significant phase errors, allow small frequency drifts between the frequency update intervals, or produce phase shifts which are not possible to track in a dynamic array setting.…”

Section: Introductionmentioning

confidence: 99%

Adaptive Distributed Transceiver Synchronization Over a 90 Meter Microwave Wireless Link

Mghabghab¹,

Schlegel²,

Nanzer³

2020

Preprint

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We present an adaptive approach for synchronizing both the phase and frequency of radio-frequency transceivers over long-range wireless links to support distributed antenna array applications. To enable distributed beamforming between separate wireless nodes, the oscillators in the transceivers must operate at the same frequency, and their phases must be appropriately aligned to support phase-coherent beamsteering. Based on a spectrally-sparse waveform, a self-mixing circuit, and an adaptive control loop, we present a system capable of synchronizing the RF oscillators in separate transceivers over distances of nearly 100 m. The approach is based on a spectrally-sparse waveform for joint inter-node ranging and frequency transfer. A frequency reference is modulated onto one signal of a two-tone waveform transmitted by the primary node which is demodulated and used to lock the oscillator of the secondary node. The secondary node retransmits the two-tone signal which the primary node uses for a high-accuracy range measurement. From this range, the phase of the two transceivers can be aligned to support beamforming. We furthermore implemented an adaptive phase control approach to support high-accuracy phase coordination in changing environmental conditions. We demonstrate continuous high accuracy links over a 90 m distance in an outdoor environment for durations up to seven days, demonstrating sufficient phase coordination in changing weather conditions to support distributed beamforming at frequencies up to 3 GHz.

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Decentralized Frequency Synchronization in Distributed Antenna Arrays With Quantized Frequency States and Directed Communications

Cited by 25 publications

References 31 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

Multi-Node Open-Loop Distributed Beamforming Based on Scalable, High-Accuracy Ranging

Adaptive Distributed Transceiver Synchronization Over a 90 Meter Microwave Wireless Link

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