New transmission scheme with hierarchical modulation in dual-hop wireless relaying systems

Dual-hop transmission is a technique by which the channel from the source to the destination is split into two possibly shorter links using other nodes. The source transmits signals to the destination via a group of nodes that act as relays. It is an effective technique when the direct link between the source and the destination is in deep fading, severe shadowing, or non-line-of-sight (NLOS) environment. In this network, the reliability of the communications is improved whereas the throughput might go down since the transmission is performed by two times. In this paper, we propose a scheme that uses hierarchical modulation at the source and selective modulation based on cyclic redundancy check (CRC) code at the relays. Simulation results show that our scheme outperforms conventional schemes in terms of the bit error rate (BER) and throughput performances.