Multiple Sequence Multicarrier CDMA for Interference-free Multiple Access

This paper shows a general structure for multicarrier (MC) CDMA that avoids multiuser interference even over fading channels. The technique converts a multi-access interference (MAI) channel into an inter symbol interference (ISI) channel for every user. ISI does not pose as big a problem as MAI does due to the absence of the near-far effect. Conventional equalization techniques can be used to remove the effects of ISI. The technique is based on transmitting multiple sequences for each user over the same channel. Even though each sequence of a given user interferes with sequences of other users, the sum of the interferences of the multiple sequences of the user is identically equal to zero. The system is designed such that the total number of users supported is the same as that supported by conventional MC-CDMA