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We propose two techniques for the low-density parity-check (LDPC) coded partial response channel with run-length-limited (RLL) constraints. The first is a modification of the selective flipping technique so that side information is not needed. The second is based on the estimation of flipped bits for the selective flipping technique. The second technique can achieve significant performance improvement over the simple selective flipping technique either with side information or without side information. We also incorporate these two techniques into a known technique to design LDPC coded recording systems that can meet strict RLL constraints without performance degradation. Index Terms--Constrained codes, low-density parity-check (LDPC) codes, recording, run-length-limited (RLL) codes.

Repeated clipping and filtering (RCF) is a simple method for reducing the peak-to-average power ratio (PAPR) of the signal in the orthogonal frequency-division modulation (OFDM) system. We propose to modify RCF by limiting the distortion on each tone of the OFDM so that both low PAPR and low error can be achieved. Index Terms--Bounded distortion (BD), clipping and filtering, orthogonal frequency-division modulation (OFDM), peak-to-average power ratio (PAPR).

In this correspondence, it is shown that some convolutional codes with distinct memory sizes of minimal encoders are equivalent in the sense that the minimal trellises of these codes are the shifted versions of one another. For an (n, k) binary convolutional code, the weight spectrum obtained from the minimal trellis may be slightly different from that obtained from the conventional code trellis with n-bit branches. Code search is conducted to find some good (n, n - 1) binary convolutional codes. Bounds on the trellis complexity, measured by the number of states and the number of branches in the minimal trellis module, of any convolutional code and its equivalent codes are also derived. Index Terms--Error-correction coding, convolutional codes, minimal trellis, minimal trellis module, trellis complexity.

It is already known that a trellis code T, which is constructed by using the encoder of a convolutional code C with short constraint length followed by a delay processor and a signal mapper, is equivalent to a trellis code with large constraint length. In this paper, we derive a new lower bound on the free distance of T, which, in some cases, is better than the previously derived bound. Moreover, instead of the decoding used in earlier publications, we apply iterative decoding on both tailbiting and zero-tail representations of T to take advantage of the new lower bound and, in the meantime, to decrease the associated error coefficient caused by the decoding used in earlier publications. Comparisons among various designs of such a trellis code and some well-known coding methods are also provided. Index Terms--Convolutional codes, trellis-coded modulation (TCM), trellis codes.

We show that the state complexity profile of a convolutional code C is the same as that of the reciprocal of the dual code of C in case that minimal encoders for both codes are used. Then, we propose an optimum permutation for any given (n, n - 1) binary convolutional code that will yield an equivalent code with the lowest state complexity. With this permutation, we are able to find many (n, n - 1) binary convolutional codes which are better than punctured convolutional codes of the same code rate and memory size by either lower decoding complexity or better weight spectra. Index Terms--Convolutional codes, decoding, trellis codes.

This paper presents a new upperbound on the pairwise error probability of MPSK sequences for the Rayleigh fading channel when channel state information (CSI) is unavailable. This bound is derived by adding weight factors in computing symbol metrics. Simulation results show that the weight factors which optimize the upperbound likely optimize the error rate as well. Multilevel coded MPSK schemes for the Rayleigh fading channel are also devised. Results show that the added weight factors improve the error performances of these schemes in the case that CSI is unavailable. Index Terms - Coded modulation, fading channel, multilevel coding.

Runlength-limited (RLL) codes are used in magnetic recording. The error patterns that occur with peak detection magnetic recording systems when using a runlength-limited code consist of both symmetric errors and shift errors. We will refer to shift errors and symmetric errors collectively as mixed-type errors. In this correspondence, a method of providing error control for mixed-type errors that occur in a runlength-limited code comprised of (d, k) constrained sequences is examined. The coding scheme is to choose parity blocks to insert in the constrained information sequence. The parity blocks are chosen to satisfy the constraints and to provide some error control. The cases of single error detection and single error correction are investigated, where the single error is allowed to be a shift error or a symmetric error. Bounds are discussed on the possible lengths for the parity blocks. It is shown that the single error-detection codes are the best possible in terms of the length of the parity blocks. Index Terms - Error-correction coding, error-detection coding, RLL codes.

We show that decision-feedback differential phase detection (DFDPD) is equivalent to a technique which generates a phase reference by averaging several primitive phase references. We then modify DFDPD into a differential phase detection (DPD) technique which generates the phase reference using a simple recursive form. The proposed technique can be easily implemented and has satisfactory error performance. Index Terms - Differential detection, phase detection, phase-shift keying.

We propose a trellis-coding scheme for which large free distances and low decoding complexities can be easily achieved. The proposed trellis-coding scheme is a generalization of the trellis-coding scheme proposed by Hellstern. With the proposed trellis-coding scheme, we have the flexibility of controlling the decoding delay. Index Terms - Binary codes, coded modulation, codes, multilevel coding, trellis coding.

We provide useful results on two classes of convolutional codes: binary codes and nonbinary codes. The best codes or the best known codes for these two classes of convolutional codes are found by computer search. Some of them are better than those found in the past. We specify these codes by their transfer function matrices, distance spectra, and information-weight spectra. Furthermore, we derive an upper bound on the free distances of binary-to-M-ary codes and q-ary-to-M-ary codes. Numerical values of this bound closely fit the computer-searched values. Index Terms - Codes, convolutional codes, distance spectra, information-weight spectra, linear codes.

We propose a hybrid ARQ scheme which uses QPSK modulation for the first transmission and BPSK modulation for retransmissions. The throughput performance of the proposed ARQ scheme is better that those of ARQ schemes purely using QPSK modulation or purely using BPSK modulation for transmissions. Furthermore, the proposed scheme does not require any operation of error correction as usually required in hybrid ARQ schemes. Therefore, the ARQ scheme proposed in this paper can be easily implemented.

We propose a new trellis coded modulation scheme which is constructed by combining a convolutional code and a variation of block coded modulation called block coded modulation with interblock memory. In the proposed scheme, each coded multidimensional signal point has a kind of two-fold dependency on other coded multidimensional signal points. In addition to the dependency on other coded multidimensional signal points described by the trellis of a convolutional code, each coded multidimensional signal point has another form of dependency on one previously coded multidimensional signal point. The additional dependency comes from the design of block coded modulation with interblock memory. Index Terms - Coded modulation, trellis coded modulation, block coded modulation, coset codes, interblock memory.

In this paper, we propose a coded modulation scheme with interblock memory. The proposed scheme has a multi-stage coding structure. However, at some coding stage, the coding designs for every two adjacent blocks are related. Compared to coded modulation schemes for which each block is independent of the others, the introduction of interblock coding provides us with additional flexibility in the design. In this way, for the proposed scheme, we can achieve large minimum Euclidean distance while the number of nearest neighbors is not too large. We also design a multi-stage decoding algorithm, which is optimum in each stage and has low decoding complexity. Three specific examples are provided to demonstrate the advantages of the proposed scheme.

This letter shows several methods for improving the decoding of noncoherent trellis-coded M-ary phase-shift keying. We propose two new metrics for basic decision-feedback algorithm. These metrics are derived based on the idea of reducing the effect of incorrect amplitude of the reference signal. We also propose a new decoding algorithm that uses a simple way to estimate the metric of the future sequence. Index Terms--Coded modulation, decoding, noncoherent detection.

A trellis code encoded by using the encoder of a convolutional code C with a short constraint length followed by an additional processing unit is equivalent to a trellis code with a large constraint length. In 1993, Hellstern proposed a trellis coding scheme for which the processing unit consists of a delay processor and a signal mapper. With Hellstern's scheme, trellis codes with large free distances can be constructed. In this paper, we propose two trellis coding schemes. For the first scheme, the processing unit is composed of multiple pairs of delay processors and signal mappers. For the second scheme, the processing unit is composed of a convolutional processor and a signal mapper, where a convolutional processor is a rate 1 convolutional code. The trellis code constructed from each of the proposed schemes can be suboptimally decoded by using the trellis of the convolutional code C with some feedback information. Either of the proposed schemes can produce a trellis code that has a larger bound on free distance and better error performance as compared to the trellis code constructed from Hellstern's scheme based on the same convolutional code C. Index Terms--Convolutional codes, trellis-coded modulation, trellis codes.

The A^\ast algorithm for decoding linear block codes is an efficient tree-search method for decoding short linear block codes. The information contained in the parity bits are potentially useful for reducing the edges needed in the tree search. We propose to extract the information embedded in the parity bits by considering sums of parity bits which can be decided by part of the message bits. Analysis for the number of required message bits for obtaining sums of parity bits is provided. The information contained in the parity bits can help to reduce the number of search tree edges. [ABSTRACT FROM PUBLISHER]