Cross-layer optimization with cooperative communication for minimum power cost in packet error rate constrained wireless sensor networks

This paper addresses the problem of joint design of routing, medium access control (MAC), and physical layer protocols with cooperative communication to achieve minimum power cost in packet error rate (PER) constrained wireless sensor networks (WSNs). The problem is solved in two steps. First, we calculate the minimum power cost with a specified PER objective between any two nodes, assuming either cooperative (with a single relay node) or direct communication between the two nodes. It is shown that the minimum per-hop power cost is found in 2M and log2 M steps for cooperative and direct communication, respectively, where M is the number of power levels. Second, we formulate the cross-layer design problem as a linear optimization problem to minimize the power cost of the whole network, using the minimum per-hop power cost determined in the first step as input and assuming time division multiple access (TDMA) at the MAC layer. Numerical results show that, at a desired end-to-end PER objective, cross-layer optimization with cooperative communication achieves up to 70% of power savings compared to that without cooperative communication.