Hierarchical modulation with vector rotation for multimedia broadcasting

Hierarchical modulation (HM) offers an important coverage/throughput tradeoff for wireless communication, which involves a “base-layer” (BL) and an “enhancement-layer” (EL) bit streams. Generally, HM suffers from the severe performance degradation of the less protected EL stream. In this paper, HM with vector rotation operation introduced to EL stream is proposed, in order to improve the performance of EL stream. With the proper interleaving in frequency domain, this operation can exploit the inherent diversity gain from the frequency-selective channel. In this way, HM with vector rotation can effectively enhance video quality of multimedia broadcasting in wideband systems. In the experimental results with the assumption that scalable video coding (SVC) is taken at the source, the significant benefit in video quality is shown in comparison with the conventional HM and alternative schemes.