Turbo Trellis-Coded Hierarchical-Modulation Assisted Decode-and-Forward Cooperation

Hierarchical modulation (HM), which is also known as layered modulation, has been widely adopted across the telecommunication industry. Its strict backward compatibility with single-layer modems and its low complexity facilitate the seamless upgrading of wireless communication services. The potential employment of HM in cooperative communications has the promise of increasing the achievable throughput at low power consumption. In this paper, we propose a single-relay-aided hierarchical-modulation-based cooperative communication system. The source employs a pair of turbo trellis-coded modulation (TTCM) schemes relying on specially designed HM, whereas the relay invokes the decode-and-forward (DAF) protocol. We have analyzed the system's achievable rate, as well as its bit error ratio (BER), using Monte Carlo simulations. The results demonstrate that the power consumption of the entire system is reduced to 3.62 dB per time slot (TS) by our scheme.