Design of Hierarchical Modulation for Wireless Relay Networks

Two designs of un-uniformed constellations for wireless relay networks are considered. The first design is concerned with the unequal error protection issue, in which two data streams to be transmitted from a source to a destination are protected at two different levels. Based on a simple approximation of the average bit-error-rate (BER), a design parameter is obtained in a closed form. The second design focuses on minimizing the average BER of the combined data stream at the destination. Developed are two near optimal designs for 4/16-QAM and 4/64-QAM hierarchical modulation schemes. Simulation results confirm the superiority of the proposed designs as well as the advantages of the relay-assisted transmission with a hierarchical modulation over the conventional point-to-point transmission.