| 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 2x2 integer rotation matrix for QAM signals, 3x3 and 4x4 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. |
