A Cooperative Transmission Strategy using Hierarchical Modulation

In this paper, a novel forward link cooperation scheme using hierarchical modulation is proposed. We define a cooperative unit cell as a unit which includes base-station (BS), fixed relay-station (FRS) and two types of mobile-station (MS) being the relay-assisted mobile-station (RAMS) and the non-relay-assisted mobile-station (NRAMS). We describe how to exploit the hierarchical modulation for the proposed cooperation between BS-FRS-RAMS link and BS-NRAMS link in the unit cell. The proposed scheme yields an improved throughput due to the characteristics of hierarchical modulation such as simultaneous transmission and multi-level protection layer. Simulation results and simple throughput analysis show that the proposed cooperation scheme outperforms the conventional cooperative and non-cooperative communication schemes with respect to the throughput performance.