An improved recursive algorithm for BLAST
Introduction
V-BLAST (Bell Labs layered space time) architecture [1] is a multiple-input multiple-output (MIMO) wireless communication system achieving very high spectral efficiency in rich multipath environments through exploiting the extra space dimension. In [2] a fast algorithm for V-BLAST is proposed, and in this paper, its efficiency is further improved and the speedups in the number of multiplications and additions are 1.47 and 1.2, respectively. As a comparison, the speedups of the original recursive algorithm [2] over the original square-root algorithm [3] are 1.54 and 1.89, respectively.
Section snippets
System description
The V-BLAST system considered consists of M transmit antennas and N (⩾M) receive antennas in a rich-scattering and flat-fading wireless channel. At the transmitter, the data stream is de-multiplexed into M streams, and each sub-stream is encoded and fed to its respective transmit antenna. Each receive antenna receives the signals from all M transmit antennas. At each time, the received signal is given by where is the N×M complex channel matrix with
Recursive V-BLAST algorithm
The conventional V-BLAST detection detects M elements of s iteratively with an optimal ordering. With reference to (2), (1), the “best” detected element of s would be the one with the smallest error variance, i.e. the smallest diagonal elements Qii of Q. It can be used to improve the detection of the remaining M−1 signals. Suppose that the order of the entries of s is arranged such that this best detected element of s is corresponding to the Mth entry sM. Treating sM as a known quantity, we
Improvement of the recursive algorithm
From the steps of the recursive algorithm in last section, it can be found that some of the matrixes, such as R and Q and their deflated sub-matrices are Hermitian matrixes. Furthermore, there are intermediate results generated during the recursive process are not fully utilized (which will become clearer in later part of this section). By carefully exploring the structure of Hermitian matrixes and reusing intermediate results, the computation complexity of the recursive algorithm can be
Complexity evaluation
In a summary, the improved recursive algorithm requires multiplications and additions. If M=N, the improved recursive algorithm requires of multiplications and additions, while the original recursive algorithm requires multiplications and additions [2]. The speedups of the improved recursive algorithm over the original recursive algorithm in the number of multiplications and additions are and ,
Conclusions
In this paper, an improved recursive algorithm for a V-BLAST system has been proposed. The speedups of the improved recursive algorithm over the original recursive algorithm in the number of multiplications and additions are 1.47 and 1.2 respectively. As to the “quick and dirty” flops comparison, the original recursive algorithm needs 40% more flops than the improved recursive algorithm.
References (4)
- P.W. Wolniansky, G.J. Foschini, G.D. Golden, R.A. Valenzuela, V-BLAST: an architecture for realizing very high data...
- J. Benesty, Y. Huang, J. Chen, A fast recursive algorithm for optimum sequential signal detection in a BLAST system,...
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