Title :
High performance Viterbi decoder for OFDM systems
Author :
Akay, Enis ; Ayanoglu, Ender
Author_Institution :
Dept. of Electr. Eng. & Comput. Sci., California Univ., Irvine, CA, USA
Abstract :
For systems that deploy conventional convolutional codes, a Viterbi decoder is the best solution, in the maximum likelihood sense, to decode an information sequence. Typically, a Viterbi decoder uses the Euclidean or Hamming distance as a metric. The use of a conventional metric leads to a high performance for systems that are employed for frequency nonselective channels (e.g., additive white Gaussian noise, AWGN, or Rayleigh fading ). However, if the system is based on orthogonal frequency division multiplexing (OFDM) and the channel has frequency selective multipath fading, then the performance can be further improved. We propose a simple modification to the conventional Viterbi metric (Euclidean distance) that improves the performance substantially if the channel is frequency selective. Simulation results on the IEEE 802.11a wireless local area network (WLAN) standard show that the performance is improved about 10 dB when the proposed metric is used. Furthermore, the proposed metric gives the same high performance as the conventional Viterbi metric if the channel is AWGN or flat fading.
Keywords :
AWGN channels; OFDM modulation; Rayleigh channels; Viterbi decoding; convolutional codes; data communication; maximum likelihood decoding; multipath channels; wireless LAN; AWGN channels; Euclidean distance; Hamming distance; IEEE 802.11a WLAN; IEEE 802.11a wireless local area network; OFDM; OFDM systems; Rayleigh fading channels; Viterbi decoder; additive white Gaussian noise channels; convolutional codes; flat fading channels; frequency nonselective channels; frequency selective fading; maximum likelihood decoder; multipath fading; orthogonal frequency division multiplexing; wireless data communications; AWGN; Additive white noise; Convolutional codes; Euclidean distance; Hamming distance; Maximum likelihood decoding; OFDM; Rayleigh channels; Viterbi algorithm; Wireless LAN;
Conference_Titel :
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th
Print_ISBN :
0-7803-8255-2
DOI :
10.1109/VETECS.2004.1387967