Abstract: Among spatial diversity scheme, orthogonal space-time block code (OSTBC) and cyclic delay diversity (CDD) have been widely studied for the cooperative wireless relaying system. However, conventional OSTBC and CDD cannot cope with change in the number of relays owing to low throughput or error performance. In this paper, we propose a cooperative cyclic delay diversity (CDD) scheme that use hierarchical modulation at the source and adaptive modulation based on cyclic redundancy check (CRC) code at the relays.
Abstract: Space-time block code(STBC) has been studied to get
full diversity and full rate in multiple input multiple output(MIMO)
system. Achieving full rate is difficult in cooperative communications
due to the each user consumes the time slots for transmitting
information in cooperation phase. So combining MIMO systems
with cooperative communications has been researched for full diversity
and full rate. In orthogonal frequency division multiple access
(OFDMA) system, it is an alternative way that each user shares their
allocated subchannels instead of using the MIMO system to improve
the transmission rate. In this paper, a Decode-and-forward (DF)
based cooperative communication scheme is proposed. The proposed
scheme has improved transmission rate and reliability in multi-path
fading channel of the OFDMA up-link condition by modified STBC
structure and subchannel sharing.