Integer Spreading Rotation Matrices for Qam Constellations and Its Application to Decode-Remodulate-Forward Cooperative Communication Strategy

摘要

Diversity techniques are commonly used in wireless communications to combat multi-path fading. Recent interests in ultra-wideband technology focus on multi-band OFDM systems that can explore the high diversity due to the independent frequency bands. To achieve full diversity with high data rate, a system (800), apparatus (500) and method that uses coded modulation with spreading rotation of transmitted signals. A 2×2 integer rotation matrix for QAM signals, 3×3 and 4×4 integer rotation matrices for QAM signals are provided. Compared with the non-regular QAM shape for real rotation matrices, each of these integer rotation matrices makes the regular QAM shape after rotation. The systematic design of these spreading matrices can be used to simplify the receiver structure such as simplified ML, MMSE and ZF, and then reduce their decoding complexity. Further, the present invention achieves cooperative diversity not only from distributed users but also from the signal space diversity of each user. An embodiment is provided for a cooperative system (100) in which different rows of integer rotation matrices are used by a source and relays as a modulation scheme to increase cooperative diversity.