Code hopping multiple access (CHMA) is a newly emerging multiple access technique with its potential to implement high security communications. Unfortunately, orthogonality amongst user signals in existing CHMA schemes can be preserved only in synchronous channels under an assumption that neither multipath interference (MI) nor multiple access interference (MAI) exists. Exploiting their ideal orthogonality, we apply orthogonal complementary codes to CHMA systems to overcome the problems with existing CHMA schemes. In particular, we will show that the application of orthogonal complementary codes can significantly improve the performance of a CHMA system due to its unique collision resistant capability. The properties and BER performance of the proposed system are analyzed for both uplink and downlink applications, where the system may suffer MI and MAI simultaneously. Simulation results show that the complementary coded CHMA with channel coding offers a high capacity as a robust PHY for futuristic wireless communications.
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