Turbo equalization for EDGE system with DDF-SOVA
Xiang-guo Tang; Zhi Ding
Signals, Systems and Computers, 2001. Conference Record of the Thirty-Fifth Asilomar Conference on
Volume 1, Issue , 2001 Page(s):295 - 299 vol.1
Digital Object Identifier 10.1109/ACSSC.2001.986924
Summary:As one of the 3G wireless communication standards, EDGE (enhanced
data rates for global evolution) adopts 8PSK modulation to provide
higher data rates using the existing TDMA system infrastructure of GSM.
We study a receiver scheme which improves the detection performance
through iterative equalization and decoding. Due to the 8-ary 8PSK
alphabet of EDGE modulation, the number of states in a trellis for a
full turbo equalizer is prohibitively high. Hence, a delayed decision
feedback (DDF) approach is used to reduce the number of trellis states.
A non-binary soft output Viterbi algorithm (SOVA) is developed to
calculate the soft value of 8PSK channel input symbols. Iterative
channel estimation is also applied to improve the accuracy of channel
estimation. In addition, a prefilter is designed to "shorten" the ISI
(intersymbol interference) channel length. Simulation results show our
turbo equalization approach can achieve about 2 dB BER (FER) performance
gain compared with non-turbo detection after 5 detection
iterations
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