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

We address decentralized consensus frequency operation in distributed antenna arrays considering realistic system implications. Distributed antenna arrays consist of separate wireless nodes that are coherently coordinated to enable distributed beamforming. Primary among the coordination requirements is the synchronization of the internal oscillators on the platforms to ensure that all nodes transmit or receive at the same frequency. Previous analyses were based on an undirected (bidirected) networks where frequency information is passed simultaneously between a given node pair. More realistically, we consider a directed (feedback free) network where one node passing frequency information to another node does not necessarily receive information back. We further consider the case where each node can only update its frequency in discrete (quantized) frequency steps. We assess the performance through numerical simulations and experimental results from a 915 MHz hardware testbed implementation with an undirected, fully connected network and a directed, partially connected network. We demonstrate that frequency consensus can be achieved in both networks with quantized frequency states, and that high levels of coherent beamforming gain are possible to obtain in both cases.