Title :
Capacity analysis for parallel and sequential MIMO equalizers
Author :
Zhang, Xinying ; Kung, S.Y.
Author_Institution :
Princeton Univ., NJ, USA
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. 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 outweighs 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, irrespective 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.
Keywords :
MIMO systems; channel capacity; equalisers; fading channels; intersymbol interference; least mean squares methods; ISI; MMSE; SNR regions; capacity gaps; channel capacity; closed-form formulas; flat-fading channels; frequency band slicing; infinitesimal stripes; multiple-input-multiple-output channels; parallel equalizers; ratios; sequential MIMO equalizers; zero-forcing equalizers; Channel capacity; Equalizers; Filters; Frequency; H infinity control; Integrated circuit modeling; Interference; MIMO; Mathematical model; Vectors;
Conference_Titel :
Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03). 2003 IEEE International Conference on
Print_ISBN :
0-7803-7663-3
DOI :
10.1109/ICASSP.2003.1202653