Extending Lifetime of the Network and Crucial Node by Multiple Diversity Combining

We introduce the crucial nodes in sensor networks, whose energy consumption affects the network lifetime greatly. Due to the relative high traffic load at the crucial nodes, energy loss occurs when packet collision and/or retransmission. We propose a LMMSE collision separation technique by combining the space diversity provided by antenna array and network diversity provided by the Media Access Control (MAC) layer. In our solution, collided packets, at the collector, are not discarded but combined with network diversity on-demand to separate data packets from different users and improve the network performance. Using analysis and computer simulations, we demonstrate that the space and network diversity combining (SNDC) scheme for cross-layer and MMSE collision resolution is energy efficient.