Abstract
To prolong the lifetime of wireless sensor networks (WSNs), an energy-efficient method is required to minimize the energy consumption while meeting the throughput and delay requirements. In this thesis, we first analyze the energy efficiency of multiple-input multiple-output (MIMO) transmission with the consideration of both the number of antennas and the constellation size. Secondly, we extend our analysis results to a cooperative MIMO WSN where individual single-antenna sensor nodes are cooperating to form multiple-antenna transmission and reception. Furthermore, we optimize the number of antennas and the constellation size for transmission/reception such that the energy consumption is minimized for the cooperative MIMO WSN. As compared to previous cooperative MIMO schemes for WSNs, the proposed one achieves a higher energy efficiency and has a smaller critical distance above which a cooperative MIMO approach outperforms a single-input single-output (SISO) approach. In the end, the previous analysis results of energy-efficient cooperative MIMO are extended to multi-hop WSN scenarios. By jointly considering the number of hops and hop length, a new energy-efficient multi-hop model is proposed. Numerical results show that the proposed model can not only balance the energy consumption but also save energy significantly.