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We investigate the joint source-channel coding problem of transmitting nonuniform memoryless sources over binary phase-shift keying-modulated additive white Gaussian noise and Rayleigh fading channels via turbo codes. In contrast to previous work, recursive nonsystematic convolutional encoders are proposed as the constituent encoders for heavily biased sources. We prove that under certain conditions, and when the length of the input source sequence tends to infinity, the encoder state distribution and the marginal output distribution of each constituent recursive convolutional encoder become asymptotically uniform, regardless of the degree of source nonuniformity. We also give a conjecture (which is empirically validated) on the condition for the higher order distribution of the encoder output to be asymptotically uniform, irrespective of the source distribution. Consequently, these conditions serve as design criteria for the choice of good encoder structures. As a result, the outputs of our selected nonsystematic turbo codes are suitably matched to the channel input, since a uniformly distributed input maximizes the channel mutual information, and hence, achieves capacity. Simulation results show substantial gains by the nonsystematic codes over previously designed systematic turbo codes; furthermore, their performance is within 0.74-1.17 dB from the Shannon limit. Finally, we compare our joint source-channel coding system with two tandem schemes which employ a fourth-order Huffman code (performing near-optimal data compression) and a turbo code that either gives excellent waterfall bit-error rate (BER) performance or good error-floor performance. At the same overall transmission rate, our system offers robust and superior performance at low BERs ([less than or equal to] [10.sup.-4]), while its complexity is lower. Index Terms--Additive white Gaussian noise (AWGN) and Rayleigh fading channels, joint source-channel coding, nonsystematic turbo codes, nonuniform independent and identically distributed (i.i.d.) sources, Shannon limit.

This paper proposes a performance evaluation technique for iteratively (turbo) equalized magnetic recoding systems. The technique decomposes the bit-error rate (BER) function into an integral of two functions. The first function has a closed form expression and is determined by the characteristics of the noise. The second function depends on the parameters of the concatenated system and can be approximated using an interpolation between sample points that rely on a small number of simulations. We present numerical and simulated BER results for coded PR4 and EPR4 channels with turbo equalization. In the 'waterfall region' of the BER curves, the calculated and simulated results are within about 0.1 dB. Index Terms--Iterative equalization, magnetic recording systems, partial response channels, performance evaluation.

This paper proposes a low-complexity signal detection scheme for multitrack recording channels. The performance of the detector in a turbo-coded architecture is investigated on the [ME.sup.2] PR channel used for high-density recording with strong intertrack interference. Simulation results indicate that the proposed system operates successfully in moderate signal-to-noise ratio ranges even for a large number of heads and tracks. Index Terms--Detection for multitrack recording systems, intertrack interference and partial response channels, iterative equalization, turbo codes.

We investigate the joint source-channel coding problem of transmitting nonuniform memoryless sources over binary phase-shift keying-modulated additive white Gaussian noise and Rayleigh fading channels via turbo codes. In contrast to previous work, recursive nonsysteniatic convolutional encoders are proposed as the constituent encoders for heavily biased sources. We prove that under certain conditions, and when the length of the input source sequence tends to infinity, the encoder state distribution and the marginal output distribution of each constituent recursive convolutional encoder become asymptotically uniform, regardless of the degree of source nonuniformity. We also give a conjecture (which is empirically validated) on the condition for the higher order distribution of the encoder output to be asymptotically uniform, irrespective of the source distribution. Consequently, these conditions serve as design criteria for the choice of good encoder structures. As a result, the outputs of our selected nonsystematic turbo codes are suitably matched to the channel input, since a uniformly distributed input maximizes the channel mutual information, and hence, achieves capacity. Simulation results show substantial gains by the nonsystematic codes over previously designed systematic turbo codes; furthermore, their performance is within 0.74-1.17 dB from the Shannon limit. Finally, we compare our joint source-channel coding system with two tandem schemes which employ a fourth-order Huffman code (performing near-optimal data compression) and a turbo code that either gives excellent waterfall bit-error rate (BER) performance or good error-floor performance. At the same overall transmission rate, our system offers robust and superior performance at low BERs (≤ 10-4), while its complexity is lower. [ABSTRACT FROM AUTHOR]

Studies linear complexity detection with iterative processing for space-time coded systems by researchers from Montreal, Quebec. Examination on wireless data transmission over multi-input, multi-output (MIMO) channels when only the receiver has perfect channel state information; Derivation of the linear-complexity space-time detector in the context of the turbo-code-based space-time transmitter and iterative processing; Elucidation that the proposed receivers suitable for uplink transmission perform at a level within 2 to 3 decibel of the ergonomic channel capacity on MIMO channels.

Describes an ambiguity zone detection based iterative decoder, operating on generalized erasures, as an alternative for concatenated systems where turbo decoding cannot be performed. Application of the techniques to selected wireless communication and digital recording systems; Simulation results; Information on decoding gains.