| 1. |
- Griffiths, Wayne, et al.
(författare)
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APP Decoding of Block Codes Over Prime Fields on Non-Binary Gilbert-Elliott Channels
- 2008
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Konferensbidrag (refereegranskat)abstract
- We present an a-posteriori probability (APP) decoding algorithm for linear block codes over prime fields when used on non-binary Gilbert-Elliott channels (GECs). The proposed approach is based on a single-sweep APP decoding technique that uses matrix multiplications. The trellis-based decoding algorithm incorporates the channel-induced error process by modeling it as a stochastic automaton. It is applicable to high rate block codes over prime fields on channels with memory such as the non-binary GEC. It allows simple implementation in the spectral domain.
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| 2. |
- Griffiths, Wayne, et al.
(författare)
-
APP Decoding of Non-Binary Block Codes on Gilbert-Elliott Channels Using Generalized Weight Polynomials
- 2008
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we present an a-posteriori probability (APP) decoding algorithm for non-binary block codes on non-binary Gilbert-Elliott channels (GECs) using generalized weight polynomials. The proposed approach is based on a single-sweep APP decoding technique that utilizes matrix multiplications. By fixing the crossover probability in the `bad' state of the non-binary GEC such that for a given transmitted symbol, all symbols are equally likely to be received, an APP decoding decision can efficiently be reached by evaluating trivariate polynomials. In this case, the non-binary GEC is described by three variables that are referred to as the average fade to connection time ratio, the burst factor, and the channel reliability factor. The application of the generalized weight polynomial approach is demonstrated with respect to numerical performance results obtained for simple non-binary block codes from computer simulations.
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| 3. |
- Rohani, Behrooz, et al.
(författare)
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Monitoring of In-Service Perceptual Speech Quality in Modern Cellular Radio Systems
- 2008
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Konferensbidrag (refereegranskat)abstract
- A method for in-service monitoring of the end-user perceptual speech quality in modern cellular radio systems is proposed. This method incorporates the perceptual evaluation of speech quality (PESQ) algorithm to monitor the quality experienced by the end-user. Here, the monitoring is carried out at the transmitting side. In this case, the speech signal received by the end-user is approximated at the transmitter in accordance with a feedback signal. The performance of the proposed scheme has been investigated through extensive computer simulations for the Universal Mobile Telecommunication System (UMTS) using different speech coding rates and channel conditions. The results indicate that the proposed scheme can predict the end-user quality with a root-mean-squared error (RMSE) of at most 0.15 using the mean opinion score (MOS) rating scheme. Such accuracy can be beneficial in applications such as network maintenance and radio resource management for satisfying desired level of quality of service.
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| 4. |
- Shaheem, Asri, et al.
(författare)
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Enhanced Channel Shortened Turbo Equalization
- 2008
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Konferensbidrag (refereegranskat)abstract
- In this paper, the use of a channel shortening prefilter in conjunction with a maximum a-posteriori probability (MAP) based turbo equalizer is considered. The prefilter shortens the effective channel, thereby reducing the number of equalizer states. As a result of channel shortening, residual intersymbol interference (ISI) appears at the input to the turbo equalizer and the noise becomes colored. To account for the ensuing performance loss, two enhancements to the scheme are proposed. Firstly, a feedback path is used to cancel residual ISI. Secondly, a carefully selected value for the variance of the noise assumed by the MAP-based turbo equalizer is used. Simulations are performed over the highly dispersive Proakis C channel. It is shown that the proposed enhancements give an improvement of approximately 0.65 dB with respect to the unmodified channel shortened turbo equalizer at a bit error rate (BER) of 10E-5.
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