MIMO with Energy Recycling

Multiple input single output (MISO) point-to-point communication system is considered where the transmitter is designed such that, each antenna can transmit information or harvest energy at any given point in time. We evaluate the achievable rate by this system, subject to an average power constraint and show that, by careful switching of antennas between transmission and harvesting modes, it is possible to exceed the capacity of the non-harvesting counterpart. We find that, the optimal harvesting antenna scheduling algorithm has complexity that grows exponentially with the number, M , of antennas. Therefore, we provide a scheduling algorithm whose complexity O(M logM) with a minimal loss in the achievable rate. Moreover, we provide a hardware setup and experimental results for a 4-antenna transmitter with uniform linear array (ULA). We provide hardware measurements for the power recycled from the transmitting antennas and the power received at the target receiver for different array spacing and different selection of the active antennas subset. We measure the impact of antenna coupling due to recycling on the amount of received power and feed these findings to obtain a well-educated performance evaluation of the system.