This paper introduces a type-I hybrid ARQ scheme for the Z-channel, based on a class of codes which can correct t asymmetric errors and further detect d (d > t) more. The specific parameters of the ARQ schemes are considered and an upper bound on the probability of undetected error is derived. We give a couple of detailed examples based on classic inner error correcting codes. They show good behavior of this scheme in terms of error rate and throughput

Corrupted packets that cause retransmission requests in automatic retransmission request (ARQ) systems can be reused. They can be combined with additional stored copies of the transmitted packet in order to obtain a single packet which is more reliable than any of the constituents. A scheme which suits the Z-channel is proposed here and the performance is analyzed under different coding assumptions.

Bose and Lin introduced a class of systematic codes for the detection of asymmetric errors (or equivalently, unidirectional errors). The determination of the probability of undetected error for these codes has been an open problem for many years. In this correspondence, the undetectable errors are characterized and the probability of undetected error is determined. Some detailed examples are given.

Bose and Lin introduced a class of systematics codes for the detection of unidirectional errors (or equivalently, asymmetric errors). The codes are described, the undetectable errors are characterized, and the probability of undetected error for these codes is determined.

In ARQ systems packets that cause retransmission requests can be reused. A diversity combining scheme for the Z-channel is proposed here, which significantly improves the throughput and the accepted packet error rate of a pure ARQ protocol using asymmetric error detection.

The errors in optical communication are of the asymmetric type. Using the Z-channel model, the Bose-Lin asymmetric error detecting codes are analyzed as part of a feedback communication system. The probabilities of detectable and undetectable errors are derived from the code construction using certain properties of the information and check sequences. This is done for two check bits initially, then generalized for any number of check bits. Based on these probabilities, the accepted packet error rate and the throughput can be calculated for pure ARQ protocols. The results obtained show very good performance, in terms of error rate and throughput efficiency, for optical networks.