Enhanced performance for an approximately MAI-free multiaccess OFDM transceiver by code selection
A new code selection scheme is proposed to reduce the MAI of the approximately MAI-free OFDM transceiver that is known as repetitively coded multicarrier CDMA (RCMC-CDMA). If we use M/2 symmetric codewords or anti-symmetric codewords of the M Hadamard-Walsh codes, then the MAI of the system can be greatly reduced. With this code selection scheme, the requirement of a sufficiently large number of subchannels to achieve the MAI-free property can be relaxed so that the approximately MAI-free property still holds when the number of subchannels is relatively small.