Structured MMSE equalization for synchronous CDMA with sparse multipath channels

We present chip-level MMSE equalizers for the forward link in CDMA that exploit the underlying channel structure, specifically the fact that the channel impulse response is sparse. The assumption we make is that the channel vector lies in the subspace associated with the pulse shaping filter convolution matrix. We can then project the chip-level MMSE equalizers onto a much lower dimensional subspace due to the sparseness of the channel. The simulations demonstrate that this low-rank MMSE equalizer converges very quickly to the asymptotic SINR, even where the underlying assumption is not valid