Path-diversity for phase detection in low-cost sensor networks

Wireless sensor networks are composed by a high number of very simple nodes. A paradigm for the nodes transceiver technology is to be energy aware and cost conscious. In this paper we consider a nonlinear transceiver structure which is a key technology for low-cost and power efficient network nodes. We use a phase detection receiver with a branch dependent metric which benefits from the knowledge of the channel fading coefficients. Therefore we introduce a method to estimate the complex coefficients based on samples of the phase detector output. Since most routing concepts for sensor networks envisage multipath routing with simple forwarding strategies (e.g. flooding), it is not far from that to make use of path diversity techniques in order to improve the network reliability. We show that remarkable diversity gains can be achieved also with the nonlinear receiver structure. By means of simulations we examine path diversity techniques for 2PSK, 4PSK and 8PSK modulation where we make use of common transmit diversity schemes. For 2PSK we propose a slight modification of the Alamouti scheme (Alamouti (1998)) to improve the performance.