Spreading code selection methods for MC-CDMA under carrier frequency offset

Carrier frequency offset (CFO) may cause multiple access interference (MAI) among users in multi-carrier code division multiple access (MC-CDMA) system. In the paper the code sensitivity of spreading codes and its correlative to the CFO is observed. An interesting property of orthogonality invariant for spreading codes under CFO has been presented. Based on the properties of code sensitivity, several algorithms of selecting the spread codes that will decrease the MAI caused by frequency offset are proposed. Using the presented code selection methods, the system capacity of MC-CDMA can be effectively increased without increasing the system complexity.