We derive an upper bound on the undetected error probability of binary (n, k) block codes used on channels with memory described by Markov distributions. This bound is a generalization of the bound presented by Kasami et al. (1984) for the binary symmetric channel, and is given as an average value of some function of the composition of the state sequence of the channel. It can be extended in particular cases of Markov-type channels. As an example, such an extended bound is given for the Gilbert-Elliott (1960, 1963) channel and Markov channels with deterministic errors determined by the state. We develop a recursive technique for the exact calculation of the undetected error probability of an arbitrary linear block code used on a Markov-type channel. This technique is based on the trellis representation of block codes described by Wolf (1978). Results of some computations are presented.

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), Blackwell's 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.>

A two step coding scheme for peak-shift correction in (d, k)-constrained sequences is described. The first step is based on q-ary (q=k-d+1 is a prime) block codes that allow correction of specific types of double errors caused by single peak-shifts. The second step is a simple conversion of q-ary symbols to binary strings of the type 00. . .01. The concatenation of these strings satisfies the (d,k)-constraint within the codeword and in concatenation with neighboring words. The length of the codewords is controlled and, if necessary, can be fixed. The rate R/sub 1/ of the overall encoding approaches (2 log/sub 2/ (k-d+1)/(k+d+2) for large codeword lengths. Codes for correction of peak-shift, deletions, and insertions of zeros are presented as well. Encoding and decoding are done by simple algorithms without using look-up tables, enumeration or denumeration procedures and, therefore, the codelength may be large.>