Spread-spectrum techniques for distributed space-time communication in sensor networks

Communication is widely acknowledged as a fundamental bottleneck in sensor networks with large numbers of low-cost, low-power nodes. We consider cooperative transmission of a common message signal from a cluster of sensor nodes to a remote receiver, under realistic transmission models accounting for timing and frequency synchronization offsets across the nodes. The purpose is to obtain range extension by combining the powers of the nodes in a cluster and to obtain robustness against channel impairments by exploiting the diversity naturally arising from the spatial distribution of the sensor nodes. For a simple scheme in which all nodes asynchronously transmit the same signal, we analyze the available diversity gains using an information theoretic analysis of outage capacity for wideband systems. We show that standard modulation formats can be adapted to realize diversity gains in the presence of synchronization errors. We propose simple receiver architectures that realize diversity gains and have desirable scaling properties as the number of sensors increases.