Code-only dependent asynchronous CDMA receivers for MUI elimination and mitigation of unknown multipath

The use of CDMA communication systems over frequency selective channels requires channel estimation or complex receiver structures to mitigate multi-user interference (MUI). Different classes of codes such as Gold codes or wavelet packets have been adopted. But new codes, called Lagrange codes, have been designed which include OFDM and multi-carrier transmissions as special cases. With simple linear (so called Vandermonde) receivers, Lagrange codes offer complete MUI cancellation independent of the channels´ impulse responses, by converting the effect of frequency selective channels into flat fading. We analyze the performance of CDMA-Lagrange transmitters and Vandermonde receivers, when each user transmits differentially encoded binary symbols. With differential demodulation at the receiver, we circumvent residual flat fading effects, while deep channel fades are handled via a root hopping technique.