Recently, a new diversity scheme called spatial phase coding (SPC) have been introduced. In conventional SPC, it was assumed that the channel phases between the transmit antennas and the receive antenna independently vary. However, practical channel phase dependently vary between neighboring subcarriers. In this letter, a feedback design method which is more efficient than conventional SPC is proposed. Furthermore, the scheme to improve the BER performance of conventional SPC using 1-bit feedback is suggested.

Dual-hop wireless transmission is a technique by which the channel from the source to the destination is divided into two shorter links using relays. By using this transmission, the communications reliability is improved whereas the throughput might go down since the dual-hop transmission is performed by two times. In this letter, we propose a scheme that uses hierarchical modulation at the source and adaptive modulation based on cyclic redundancy check (CRC) code at the relays. The proposed scheme is evaluated in terms of the bit error rate (BER) and throughput performances.