Modified MAP algorithm incorporated with PSA techniquefor turbo codes in Rayleigh fading channels

Li, K.L.; Cheung, Siu Wun

doi:10.1049/el:19990404

Cited by 3 publications

(3 citation statements)

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“…Of course and are not perfectly known at the receiver. Again assuming that the channel is slowly varying, (13) can be approximated by (14) where is the estimated channel gain associated with the pilot symbol located closest to .…”

Section: B Noise Variance Estimationmentioning

confidence: 99%

“…Reference [12] shows that the same holds true for turbo-coded systems. A branch metric suitable for turbo-coded systems using PSAM is presented in [13], although this metric requires knowledge of the carrier phase. In [12] and [13], all of the estimation was performed prior to the first iteration of turbo decoding.…”

Section: Introductionmentioning

confidence: 99%

“…A branch metric suitable for turbo-coded systems using PSAM is presented in [13], although this metric requires knowledge of the carrier phase. In [12] and [13], all of the estimation was performed prior to the first iteration of turbo decoding. However, since turbo decoding is an iterative process, performance can be improved by re-estimating the channel after each decoder iteration [14].…”

Section: Introductionmentioning

confidence: 99%

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Iterative channel estimation and decoding of pilot symbol assisted turbo codes over flat-fading channels

Valenti

Woerner

2001

IEEE J. Select. Areas Commun.

259

166

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Abstract-A method for coherently detecting and decoding turbo-coded binary phase shift keying (BPSK) signals transmitted over frequency-flat fading channels is discussed. Estimates of the complex channel gain and variance of the additive noise are derived first from known pilot symbols and an estimation filter. After each iteration of turbo decoding, the channel estimates are refined using information fed back from the decoder. Both hard-decision and soft-decision feedback are considered and compared with three baseline turbo-coded systems: 1) a BPSK system that has perfect channel estimates; 2) a system that uses differential phase shift keying and hence needs no estimates; and 3) a system that performs channel estimation using pilot symbols but has no feedback path from decoder to estimator. Performance can be further improved by borrowing channel estimates from the previously decoded frame. Simulation results show the influence of pilot symbol spacing, estimation filter size and type, and fade rate. Performance within 0.49 and 1.16 dB of turbo-coded BPSK with perfect coherent detection is observed at a bit-error rate of 10 4 for normalized fade rates of = 0 005 and = 0 02, respectively.

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Section: B Noise Variance Estimationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%