Joint energy beamforming and bandwidth allocation for cooperative localization in passive sensor networks

Abstract

Passive sensor networks (PSNs) harvest continuous radio-frequency (RF) energy to work. However, the location information is difficult to maintain with unstable power supply for each passive sensor node. Cooperative localization is a promising solution utilizes the cooperation between the nodes with unknown positions to maintain the location information. And the localization performance relies on the attained energy from the energy access point (E-AP) and also the allocated bandwidth for each node. In this paper, we analyze the impacts of energy beamforming and bandwidth allocation on the cooperative localization performance of PSNs. We formulate the Fisher information matrix (FIM) and deduce the squared position error bound (SPEB) for the proposed network. Then, we propose an alternative optimization method for jointly energy beamforming and bandwidth allocation. Firstly, we employ the first-order Taylor expansions based on the trust region method to allocate the bandwidth of each node. Secondly, the Lagrangian multiplier based energy beamforming strategy is proposed. Then, the bandwidth allocation and energy beamforming calculations are executed alternatively and iteratively until the global optimal solution is achieved. The simulation results indicate that our proposed two-step method can achieve high precision positioning in different scenarios, and the SPEBs of proposed method reach 10−3 m2.