Energy efficient MIMO transmission with high order modulations for wireless sensor network

Energy efficiency emerges as a big concern in wireless sensor networks, where the lifetime of the system depends heavily on energy consumption. In a sensor network, the energy is consumed both by the circuit and the radio link. The radio link performance can be improved by using spatial multiplexing, but the conventional way of spatial multiplexing requires large antenna space and consumes more energy. Thus single RF MIMO transmission is proposed, which maps MIMO symbols on the radiation patterns to reduce power consumption. This paper presents the energy efficiency analysis over different schemes, which extends single RF MIMO capability with 16-QAM constellation though compact ESPAR antenna with only 2 elements. A detailed analysis on the minimal required energy is given, which shows that the proposed single RF MIMO with 16-QAM signaling has similar bit error rate performance with better energy efficiency.