52
Evaluation of Variance Mismatch of Serial Turbo Codes 359
Journal of Engineering Science and Technology September 2010, Vol. 5(3)
6. Conclusions
The issue of variance mismatch on the performance of serial turbo codes (SCCC)
using the log-MAP and max-log-MAP constituent decoders was investigated in
impulsive noise channel. The log-MAP algorithm requires knowledge of the
channel reliability for the metric calculation, whereas the max-log-MAP
algorithm obviates this side information as a result of using an approximation.
However, both traditionally designed algorithms failed to perform in impulse
noise interference. Therefore, talwar penalty function was introduced and reported
to effectively curb against outliers of impulse noise reported in [9]. By setting
appropriate value for cutoff parameter v, the entries of undesired outliers from
impulse noise is blocked and cut off prior to the computation of channel transition
probability
α
(s΄, s). Therefore, LOG-MAP and MAX-LOG-MAP algorithms of
SCCC can be used in determine extrinsic information L
e
for inner and outer
component decoders.
As for the increasing importance of using PLC for internet and information
sharing [14], the study of variance mismatch for SCCC in impulsive noise
channel for next generation communication system is crucial to the researchers
and engineers in the field. Talwar penalty function enables and extends the
excellent performance of MAP based SCCC to a new technology frontier.
References
1. Berrou, C.; Glavieux, A.; and Thitimajshima, P. (1993). Near Shannon limit
error-correcting coding: Turbo-codes (1). Proc. IEEE Int. Conf. Commun.,
Geneva, Switzerland , 1064-1070.
2. Lee, L.N.; Hammons, A.R.; Jr., Sun, F.W.; and Eroz, M. (2000). Application
and standardization of turbo codes in third-generation high-speed wireless
data services. IEEE Transactions in Vehicular Technology, 49(6), 2198-2207.
3. Benedetto, S.; and Montorsi, G. (1996). Iterative decoding of serially
concatenated convolutional codes. Electronics Letters, 32(13), 1186-1188.
4. Hrasnica, H.; Haidine, A.; and Lehnert, R. (2004), Broadband powerline
communication network design. (1st Ed.), Wiley.
5. Robertson, P.; and Hoeher, P. (1997). Optimal and sub-optimal maximum a
posteriori algorithms suitable for turbo decoding. European Transactions on
Telecomminications, 8(2), 119-125.
6. Summers, T.A.; and Wilson, S.G. (1998): SNR mismatch and online
estimation in turbo decoding. IEEE Transactions on Communications, 46(4),
421-423.
7. Jordan, M.A.; and Nichols, R.A. (1996). Effects of channel characteristics on
turbo code performance. Conference Proceedings Military Communications
Conference, 1996. MILCOM '96, Washington, DC, 1, 17-21.
8. Ho, M.S.C.; and Pietrobon, S.S. (2000). A variance mismatch study for
serial concatenated turbo codes. Proc. of 2
nd
Int. Symp. on Turbo Codes and
Related Topics, Brest, France.
9. Chuah, T.C.; and Pu, C.H. (2005). Serial turbo decoder for robust
communication. Electronics Letters, 41(7), 427-429.