Space-Time Spreading Aided Distributed MIMO-WSNs

In this letter, we consider the plaguing, yet rarely handled problem of interference resulting from superposition of multiple sensor signals in time, when sent over a multiple access channel (MAC) in wireless sensor networks (WSNs). We propose space-time spreading (STS) of local sensor decisions before reporting them over a MAC to i) minimize interference and ii) reduce energy required for combating interference due to superposition of sensor decisions. Each sensor decision is encoded on appropriately indexed space-time block of fixed duration using dispersion vectors, such that a single sensor is activated over each space-time block while all the other sensors are silent. At the receive side of the reporting channel, we assume a multi-antenna decision fusion center (DFC), thereby representing a distributed multiple-input-multiple-output (MIMO) communication scenario. We formulate and compare optimum and sub-optimum fusion rules for fusing sensor decisions at the DFC to arrive at a reliable conclusion. Simulation results demonstrate gain in fusion performance with STS-aided transmission by 3 to 6 times over performance without STS.

Automated summary

This letter addresses the issue of interference caused by superposition of multiple sensor signals in wireless sensor networks, and proposes the use of space-time spreading (STS) to minimize interference. By applying STS to sensor decisions before transmission, the performance of the transmission is significantly improved.