Low-Complexity Decoding of Block Turbo-Coded System with Antenna Diversity
- PDF / 773,792 Bytes
- 11 Pages / 600 x 792 pts Page_size
- 30 Downloads / 178 Views
Low-Complexity Decoding of Block Turbo-Coded System with Antenna Diversity Yanni Chen Department of Electrical and Computer Engineering, University of Minnesota, 200 Union Street, Minneapolis, MN 55455, USA Email: [email protected]
Keshab K. Parhi Department of Electrical and Computer Engineering, University of Minnesota, 200 Union Street, Minneapolis, MN 55455, USA Email: [email protected] Received 29 January 2003 and in revised form 30 April 2003 The goal of this paper is to reduce the decoding complexity of space-time block turbo-coded system with low performance degradation. Two block turbo-coded systems with antenna diversity are considered. These include the simple serial concatenation of error control code with space-time block code, and the recently proposed transmit antenna diversity scheme using forward error correction techniques. It is shown that the former performs better when compared to the latter in terms of bit error rate (BER) under the same spectral efficiency (up to 7 dB at the BER of 10−5 for quasistatic channel with two transmit and two receive antennas). For the former system, a computationally efficient decoding approach is proposed for the soft decoding of space-time block code. Compared to its original maximum likelihood decoding algorithm, it can reduce the computation by up to 70% without any performance degradation. Additionally, for the considered outer code block turbo code, through reduction of test patterns scanned in the Chase algorithm and the alternative computation of its extrinsic information during iterative decoding, extra 0.3 dB to 0.4 dB coding gain is obtained if compared with previous approaches with negligible hardware overhead. The overall decoding complexity is approximately ten times less than that of the near-optimum block turbo decoder with coding gain loss of 0.5 dB at the BER of 10−5 over AWGN channel. Keywords and phrases: block turbo code, space-time block code, low-complexity decoding, soft decoding.
1.
INTRODUCTION
One of the major challenges in wireless communications is the severe channel fading caused by multipath and movement in radio link. Recently, in order to explore the improved capacity of multiple-in multiple-out (MIMO) system over flat Rayleigh fading channel [1], different transmit diversity techniques have been developed to benefit from antenna diversity in the downlink while placing the diversity burden on the base station [2, 3]. Although space-time block code (STBC) has attracted a lot of attention, few papers have been published on its hardware implementation. The authors in [4] addressed the hard decoding of STBCs, which is based on the maximum likelihood decoding algorithm presented in [3]. STBC provides the maximum possible diversity advantage for multiple transmit antenna system with a very low complexity decoding algorithm. However, in order to achieve significant coding gain, it should be concatenated with a
powerful outer code [5, 6, 7]. The current powerful error control codes use iterative soft-input soft-output (SISO) decoding to achi
Data Loading...
