A. J. Han Vinck

On the capacity of generalized write-once memory with state transitions described by an arbitrary directed acyclic graph

The generalized write-once memory introduced by Fiat and Shamir (1984) is a q-ary information storage medium. Each storage cell is expected to store one of q symbols, and the legal state transitions are described by an arbitrary directed acyclic graph. This memory model can be understood as a generalization of the binary write-once memory which was introduced by Rivest and Shamir (1982). During the process of updating information, the contents of a cell can be changed from a 0-state to a 1-state but not vice versa. We study the problem of reusing a generalized write-once memory for T successive cycles (generations). We determine the zero-error capacity region and the maximum total number of information hits stored in the memory for T consecutive cycles for the situation where the encoder knows and the decoder does not know the previous state of the memory. These results extend the results of Wolf, Wyner, Ziv, and Korner (1984) for the binary write-once memory.

Wiretap Channel With Side Information

This correspondence gives an achievable rate equivocation region for the discrete memoryless wiretap channel with side information. We extend our results to the Gaussian case. The main contribution of this correspondence is that, for the Gaussian wiretap channel, the side information helps to get a larger secrecy capacity and a larger rate equivocation region.

Performance bounds for optimum and suboptimum reception under Class-A impulsive noise

The transmission over the memoryless additive white Class-A noise (AWCN) channel is considered. For uncoded transmission, an exact expression for the symbol error rate is derived. For coded transmission, the Chernoff bound on the pairwise error probability is calculated and the performance achieved on the real and the complex AWCN channels is compared. Moreover, a low-complexity, suboptimum decoding metric is derived and analyzed employing the cutoff rate as a performance criterion.

Power line communications: an overview

We give a systems level overview of power line communications. Topics covered, include feasible applications of power line communications, and the impact of the currently evolving international standards on power line communications. The power line communications channel is discussed at some length. Existing communications systems and solutions are discussed. The results of some measurements on the channel, are presented.

On constant-composition codes over Z/sub q/

A constant-composition code is a special constant-weight code under the restriction that each symbol should appear a given number of times in each codeword. In this correspondence, we give a lower bound for the maximum size of the q-ary constant-composition codes with minimum distance at least 3. This bound is asymptotically optimal and generalizes the Graham-Sloane bound for binary constant-weight codes. In addition, three construction methods of constant-composition codes are presented, and a number of optimum constant-composition codes are obtained by using these constructions.

Successive impulsive noise suppression in OFDM

We consider orthogonal frequency division multiplexing (OFDM) for high data rate narrowband power line communication (PLC) in the frequency bands up to 500 kHz. In narrowband PLC, the performance is strongly influenced by the impulsive noise with very large amplitudes with short durations. Simple iterative impulsive noise suppression algorithms can effectively improve the error rate performance in OFDM systems. However, the convergence speed depends on the number of subcarriers, N. For N ≤ 256, the algorithms converge slowly or not even at all. In this paper, we extend the iterative receiver design to enable a fast convergence for N ≫ 64 and to improve the error rate performance for N ≤ 64. These extensions include 1) a clipping and nulling technique at the input of the iterative algorithm 2) a novel low complexity syndrome decoder which uses the redundancy that is transmitted for synchronization or other purposes. Simulation results are provided to show the improvement in error rate

Cooperative multihop power line communications

Data communication over power line networks has a number of similarities with communication using wireless transmission. This (probably) goes back to fact that neither power lines nor wireless channels were designed for carrying communication signals. As a result, a number of techniques successfully used in wireless communications have found their way into power line communications (PLC). This has recently been extended to relaying, or more generally, cooperative communications. In this paper, we first show that, different from the wireless domain, cooperative communication does not provide a diversity advantage for typical PLC networks. Secondly, we introduce and compare different approaches of multihop transmission known from wireless communications to PLC. We compare their performances and, supported by numerical results, conclude that cooperative multihop is the preferred choice in terms of end-to-end transmission rate.

On the constructions of constant-weight codes

Two methods of constructing binary constant-weight codes from (1) codes over GF(q) and (2) constant-weight codes over GF(q) are presented. Several classes of binary optimum constant-weight codes are derived from these methods. In general, we show that binary optimum constant-weight codes, which achieve the Johnson bound, can be constructed from optimum codes over GF(q) which achieve the Plotkin bound. Finally, several classes of optimum constant-weight codes over GF(q) are constructed.

On the general defective channel with informed encoder and capacities of some constrained memories

From an information-theoretical point of view the write once memory (WOM), the unidirectional memory (WUM), the write isolated memory (WIM), the memory with address faults (MAF), Blackwells broadcast channel, and some other constrained memories and channels with an informed encoder can be considered as particular cases of the general defective channel (GDC) introduced by Kuznetsov (1983) as a generalization of a memory with defects. Using the concept of the GDC we consider a unified approach to the investigation of different types of natural and artificial channels with a finite number of states known to the encoder, but unknown to the decoder. To illustrate the usefulness of this approach we derive the capacities of the above-mentioned constrained memories (WOM, WUM, WIM, MAF) as corollaries of lower and upper bounds for the number of messages transmitted over the GDC. >

On the construction of maximal prefix-synchronized codes

We present a systematic procedure for mapping data sequences into codewords of a prefix-synchronized code (PS-code), as well as for performing the inverse mapping. A PS-code, proposed by Gilbert (1960), belongs to a subclass of comma-free codes and is useful to recover word synchronization when errors have occurred in the stream of codewords. A PS-code is defined as a set of codewords with the property that each codeword has a known sequence as a prefix, followed by a coded data sequence in which this prefix is not allowed to occur. The largest PS-code among all PS-codes of the same code length is called a maximal prefix-synchronized code (MPS-code). We develop an encoding and decoding algorithm for Gilberts MPS-code with a prefix of the form 11...10 and extend the algorithm to the class PS-codes of which the prefix is self-uncorrelated. The computational complexity of the entire mapping process is proportional to the length of the codewords.