Low complexity and fractional coded cooperation for wireless networks

Wireless networks, and especially wireless sensor networks, have complexity and energy constraints, within which they must confront the challenging wireless fading environment. In this paper, fractional cooperation is introduced, which is shown to provide energy-efficient and low-complexity diversity gains for constant energy costs per bit throughout the network. To minimize complexity, cooperation is based on demodulate- and-forward, wherein the relay nodes encode demodulated, not decoded symbols. A scheme is presented for cooperative error- control coding in complexity-constrained networks, using low- density generator-matrix codes and repeat-accumulate codes, both chosen for being simple to encode, as well as for their easily adaptable rates. It is shown that these codes, coupled with fractional cooperation, are robust to system parameters and conditions, and introduce little added complexity at the receiver, while providing excellent performance.