Precoded Block-Spread CDMA with Maximum User Support and Frequency-Domain Equalization

Block-spread code-division multiple access (BS- CDMA) is a bandwidth efficient method by which multiple users can utilize a transmission medium simultaneously. One special property of BS-CDMA transmissions is that they facilitate the use of low-complexity frequency-domain equalization (FDE) at the receiver. Recently, it was shown that this property can only be preserved for multi-user interference (MUI) free reception when the number of simultaneously transmitting users does not exceed [
M
/2], where M is the length of the block spreading code. In this paper, a novel BS-CDMA technique is presented whereby user-specific preceding is employed along with special spreading codes to ensure MUI-free reception for
M
simultaneous users, while preserving the properties of the transmission that facilitate FDE at the receiver.