Joint Movable-Antenna Position and Sensor Angle Optimization for Wireless Sensor Networks

In uplink communications of sensor networks, by utilizing the movable-antenna (MA) array, the access point (AP) can flexibly reconfigure the wireless channel between itself and each sensor to improve the system performance. However, relying solely on the MA technology still cannot achieve overly desirable performance, especially in two extreme scenarios: i) The total antenna span at the AP is relatively small, for which the channel reconfiguration ability is weak; ii) The angle of arrivals (AoAs) to the AP at some sensors are close, for which the correlation between any two of these uplink channels remains strong, no matter how the MA array is deployed. Motivated by these considerations, in this correspondence we propose to simultaneously utilize the MA technology and adjustability of AoAs to sufficiently reconfigure channel conditions. Specifically, we aim to maximize the sum rate by jointly optimizing antenna positions and the receive beamforming at the AP, and concurrently the AoA to the AP at each sensor (which can be adjusted in a certain range by optimizing the deployment of each sensor beforehand). The formulated problem is highly non-convex. To tackle it, we derive the optimal minimum mean-square error (MMSE) receive beamforming given fixed antenna positions and all AoAs, based on which we further adopt the alternating optimization to iteratively handle another two types of variables. We also present the special case of two sensors to reveal insightful conclusions. Finally, we perform simulations to show the potential advantages of our proposed scheme compared to the current MA technology.