### Abstract

It is well known that linear MMSE can outperform its zero-forcing counterpart. In combination with a successive interference canceller, MMSE can fully exploit the capacity of MIMO (Multiple-Input-Multiple-Output) channels [1, 2]. In practice, however, such an advantage is compromised due to its implementation complexity and the requirement of accurate SNR estimate. Thus other equalizers such as zero-forcing may present an attractive alternative as long as the performance gap is tolerable. This motivates a need to quantify the tradeoff between MMSE and zero-forcing in both parallel and sequential structures. In this paper, the capacity performance of different equalization schemes is investigated, with closed-form formulas provided in terms of two key measures: capacity gaps and ratios. We also conclude that the capacity gain via structural choice (between parallel and sequential) far out-weights that via filter choice (between zero-forcing and MMSE). Indeed, the latter is found to be almost negligible for most practical SNR regions. It is also shown that the sequential zero-forcing equalizers can asymptotically reach the channel capacity when SNR approaches infinity, irrelevant of the detection order. Although this paper is focused on the flat-fading channels, the result is directly extendable to the ISI case by slicing the frequency band into infinitesimal stripes, each of which can be treated as flat.

Original language | English (US) |
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Pages (from-to) | 357-360 |

Number of pages | 4 |

Journal | ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings |

Volume | 4 |

State | Published - Sep 25 2003 |

Event | 2003 IEEE International Conference on Accoustics, Speech, and Signal Processing - Hong Kong, Hong Kong Duration: Apr 6 2003 → Apr 10 2003 |

### All Science Journal Classification (ASJC) codes

- Electrical and Electronic Engineering
- Signal Processing
- Acoustics and Ultrasonics