SPCp1-03: Orthogonal Codes for MAI-Free MC-CDMA with Carrier Frequency Offsets (CFO)

The performance of MC-CDMA in the presence of carrier frequency offsets (CFO) can be severely degraded due to multiaccess interference (MAI). It is shown in this work that a properly chosen subset of real Hadamard-Walsh or exponential codes can achieve zero MAI in a CFO environment. For a channel of length L and a number G of power of 2 with G ges L, we prove that 1 + log₂ (iV/G) Hadamard-Walsh codewords or N/G exponential codewords can achieve zero MAI under any CFO level. Simulation results are given to corroborate derived theoretical results and evaluate the performance of MC-CDMA with a variable number of users in a CFO environment.