Multi-stream distributed co-phasing: Design and analysis

In this paper, we develop and analyze a distributed co-phasing technique for physical layer fusion of common data across a wireless sensor network using multi stream communication, when the fusion center (FC) is equipped with multiple receive antennas. In this two-phase scheme, sensors first estimate their respective channels to the FC antennas by using pilots transmitted by the FC; following which they simultaneously transmit multiple streams of data symbols by pre-rotating them according to the estimated channel phases to the different receive antennas. The mutual information between transmit nodes and the FC is presented, which helps to quantify the gains obtainable by multi stream communication. In order to aid data detection at the receiver, we propose an iterative blind channel estimation algorithm at the FC. It is found using simulations that the proposed blind channel estimation algorithm achieves a symbol error probability (SEP) close to that with perfect channel state information (CSI) at the FC. The SEP of the proposed scheme is theoretically analyzed. The system performance is evaluated via numerical simulation and is observed to be in close agreement with the derived expressions.