Adaptive modulation for cooperative wireless communication systems

Cooperative wireless communication network provides diversity by emulating multi-input and multi-output (MIMO) system for devices that are spatially too small to harbor multiple antennas. Since mobility and easy handling require terminal miniaturization, cooperative communication is required to fill the gap for MIMO. Conventional cooperative protocols such as amplify-and-forward (AF) and decode-and-forward (DF) attain diversity gain at the cost of reduced spectral efficiency which as a result brings about reduced throughput. In this paper, adaptive modulation is applied to improve the throughput performance of AF wireless cooperative strategy. The source and relay respond to the channel state information (CSI) obtained from the destination as a feedback to change M-QAM types. Simulation results show that modulation adaptive cooperation performs better than the non adaptive counterpart in overall throughput.