Single-Carrier Cooperative DF Relay Using Adaptive Modulation

Abstract— A throughput performance significantly degrades near the cell edge due to the path loss, shadowing loss, and multipath-fading. A cooperative relay is a well-known technique to increase the cell-edge throughput. In the cooperative relay, it is expected that assigning different levels of data modulation for mobile terminal (MT) and relay station (RS) may improve the throughput performance. In this paper, we propose a 2-time slot single-carrier (SC) cooperative decode-and-forward (DF) relay using adaptive modulation and evaluate, by computer simulation, its throughput performance. It is shown that the cooperative DF relay using adaptive modulation can reduce the normalized total transmit signal-tonoise power ratio (SNR) by about 1.5 dB compared to the cooperative DF relay using fixed modulation for a required throughput of 0.5 bps/Hz and can reduce the normalized total transmit SNR by about 9 dB compared to the direct transmission for a required throughput of 0.8 bps/Hz.