In the modern day, MPEG-4 image compression technique have been commonly applied in various indoor wireless communication systems. The efficient system design mostly relies on the joint source channel coding algorithms, which aim to reduce the complexity of channel coding process, while maintaining the quality of the receiving images. In this paper, we design the MAP source-controlled channel decoders with both random and semirandom interleavers for Rician slow flat block-fading channels. The MAP-Viterbi decoder employs the residual redundancy from zerotree symbol sequences of MPEG-4 HFS packets. The interleaving processes are done after the overall channel coding process to combat the block-fading effects. The computer simulations summarize the system performance in terms of average WER and PSNR (dB). With the interleavers, the significant improvement in PSNR of about 15-17 dB is obtained for both ML and MAP decoding. Also in many cases, we obtain more improvement of about 0.2-0.4 dB for using MAP decoding with the interleavers.

In this letter, a theoretical analysis of bit error probability for 4-state convolutional code with Max-Log-maximum a posteriori probability (MAP) decoding is presented. This technique employs an iterative calculation of probability density function of the state metric per one transition, and gives the exact bit error probability for all signal-to-noise power ratio.

Reliability-based hybrid ARQ (RB-HARQ) is a kind of incremental-redundancy ARQ recently introduced. In the RB-HARQ, the receiver returns both NAK signal and set of unreliable bit indices if the received sequence is not accepted. Since each unreliable bit index is determined by the bitwise posterior probability, better approximation of that probability becomes crucial as the number of retransmissions increases. Assuming the systematic code for the initial transmission, the proposed RB-HARQ scheme has the following two features: (a) the sender retransmits newly encoded and interleaved parity bits corresponding to the unreliable information bits; (b) the retransmitted parity bits as well as the initial received sequence are put all together to perform the message passing decoding i.e. the suboptimal MAP decoding. Finally, simulation results are shown to evaluate the above two features.

A new algorithm for the LogMAP decoding of linear block codes is considered. The decoding complexity is evaluated analytically and by computer simulation. The proposed algorithm is an improvement of the recursive LogMAP algorithm proposed by the authors. The recursive LogMAP algorithm is more efficient than the BCJR algorithm for low-rate codes, but the complexity grows considerably large for high-rate codes. The aim of the proposed algorithm is to solve the complexity explosion of the recursive LogMAP algorithm for high-rate codes. The proposed algorithm is more efficient than the BCJR algorithm for well-known linear block codes.

Turbo coding is widely known as one of effective error control coding techniques in various digital communication systems since this coding method has proposed by C. Berrou, etc in 1993. In digital magnetic recording, it has been cleared that the error correcting capability of turbo coding is superior to most of conventional recording codes as a matter of course. But, the performance of a partial response maximum-likelihood (PRML) system combined with any recording code is degraded by many undesirable factors or effects. To improve the performance of the PRML system in high areal density recording, it is useful to adopt a higher order PRML system or high rate code in a general case. In this paper, the rate 32/34 turbo code combined with an enhanced extended class-4 partial response (E2PR4) is proposed. We call this trellis coded partial response (TCPR) system the rate 32/34 turbo-coded E2PR4 (32/34 TC-E2PR4). Our proposed TCPR system can be expected to get large coding gain and improve the performance of PRML system. As a result, the proposed coding system provides a good performance compared with the conventional systems. In especial, our system can achieve a BER of 10-5 with SNR of approximately 1.5 dB less than the conventional 8/9 maximum transition run (MTR) coded E2PR4ML system at a normalized linear density of 3.

A new algorithm for the maximum a posteriori (MAP) decoding of linear block codes is presented. The proposed algorithm can be regarded as a conventional BCJR algorithm for a section trellis diagram, where branch metrics of the trellis are computed by the recursive MAP algorithm proposed by the authors. The decoding complexity of the proposed algorithm depends on the sectionalization of the trellis. A systematic way to find the optimum sectionalization which minimizes the complexity is also presented. Since the algorithm can be regarded as a generalization of both of the BCJR and the recursive MAP algorithms, the complexity of the proposed algorithm cannot be larger than those algorithms, as far as the sectionalization is chosen appropriately.

New algorithms for the MAP (also known as the APP) decoding and the MAX-LogMAP decoding of linear block codes are presented. The algorithms are devised based on the structural properties of linear block codes, and succeeds in reducing the decoding complexity without degrading the error performance. The proposed algorithms are suitable for the parallel and pipeline processing which improves the throughput of the decoder. To evaluate the decoding complexity of the proposed algorithms, simulation results for some well-known codes are presented. The results show that the algorithms are especially efficient than the conventional BCJR-based algorithms for codes whose rate are relatively low.

In various digital wireless communication systems, it is known that turbo coding provides an error rate performance within a few tenths of a dB of the theoretical Shannon limit. The error correcting capability of turbo coding is attractive for a recording code in a digital magnetic recording system. The performance of a partial response maximum-likelihood (PRML) system with any recording code is degraded by many undesirable factors such as linear and nonlinear distortions. For improving the performance of the PRML system, it is useful to adopt a high-order PRML system or high rate code in general. In this paper, the two-track recording system using turbo coding which can increase the coding rate over 1 and improve the performance is proposed. Turbo-coding provides a near-ML performance by the suboptimum symbol-by-symbol maximum a posteriori probability (MAP) decoding algorithm. Our proposed turbo-coded class 4 partial response (PR4) systems use the rate 4/6, 8/10 and 16/18 turbo codes for high-density two-track digital magnetic recording. The error rate performance is obtained by computer simulation, taking account of the partial erasure which is a prominent nonlinear distortion in high-density recording. As a result, the proposed systems are hardly affected by partial erasure and maintains good performance compared with the conventional NRZ coded PR4ML system.