Energy-Efficiency of MIMO and Cooperative MIMO Techniques in Sensor Networks

TLDR

Sensor networks rely on battery‑powered nodes, so minimizing total energy—transmission plus circuitry—while meeting throughput and delay constraints is essential. The study aims to determine the optimal modulation and transmission strategy that minimizes the energy required to send a specified number of bits. The authors evaluate the energy efficiency of MIMO using Alamouti diversity and then extend the analysis to cooperative single‑antenna nodes forming virtual multiple‑antenna transmitters or receivers. Joint transmission and reception can yield substantial energy savings beyond a threshold distance, and in certain ranges cooperative MIMO simultaneously reduces energy consumption and delay.

Abstract

We consider radio applications in sensor networks, where the nodes operate on batteries so that energy consumption must be minimized, while satisfying given throughput and delay requirements. In this context, we analyze the best modulation and transmission strategy to minimize the total energy consumption required to send a given number of bits. The total energy consumption includes both the transmission energy and the circuit energy consumption. We first consider multi-input-multi-output (MIMO) systems based on Alamouti diversity schemes, which have good spectral efficiency but also more circuitry that consumes energy. We then extend our energy-efficiency analysis of MIMO systems to individual single-antenna nodes that cooperate to form multiple-antenna transmitters or receivers. By transmitting and/or receiving information jointly, we show that tremendous energy saving is possible for transmission distances larger than a given threshold, even when we take into account the local energy cost necessary for joint information transmission and reception. We also show that over some distance ranges, cooperative MIMO transmission and reception can simultaneously achieve both energy savings and delay reduction.