Chip-Level MMSE Equalization for CDMA Downlink

This work is focused on the structure design of MMSE linear equalizers in the downlink of CDMA-based multi-user communication systems. Previous work was mostly focused on the performance comparison between ZF and MMSE linear equalizers and the conclusion is that the performance based on MMSE criterion is much better than that based on ZF one. In this paper, we only discuss MMSE equalizer and a new block structure of MMSE linear equalizer is derived from the traditional structure of this kind of equalizer. Furthermore, a block MMSE linear equalizer is improved through using the overlap-save technique. Simulation results show that the average performance of improved block MMSE linear equalizers is better than those of the block MMSE equalizers and traditional MMSE equalizers. At the same time, the computation complexity of all these MMSE equalizers is given. It is shown that the complexity of proposed block MMSE equalizers is lower than that of the traditional equalizers with optimal delay, D, when the length of the filter in traditional MMSE equalizers equals the block size of block MMSE equalizers.