Robert A. Rutledge

Performance data for a six-sample look-ahead

This paper is a sequel to a previous papcr which described the (1,7)ML channel with five-sample look-ahcad detection algorithm. It presents a modification to the prevoins (I ,7)ML algorithm, which requires six-sample look-ahead and improves the performance in the presence of non-lincarities and other non-Gaussian noise components. The paper also pre- sents data comparing the (I ,7)ML channel to the convcntional peakdetection channel.

Fault-tolerant memory simulator

Memory systems in modern computers employ a variety of methods to achieve fault tolerance, such as single- or double-error correction, page deallocation, or the use of spare chips or cells. Such methods ensure that the failure rate of the system is considerably less than the sum of the failure rates of the components. However, these methods also complicate the task of evaluating system reliability. The memory reliability function is too intractable to handle analytically, and we must turn to Monte Carlo methods. This paper describes the Fault-Tolerant Memory Simulator (FTMS), an interactive APL program which uses Monte Carlo simulation to evaluate the reliability of fault-tolerant memory systems.

Error correcting codes for satellite communication channels

This paper addresses the problem of efficient forward error correction on differentially encoded, quadriphase-shift-keying (DQPSK) channels. The approach is to design codes to correct the most probable error patterns. First the probability distribution of error patterns is derived. Then a class of convolutional codes that correct any single two-bit error is described. Finally a threshold decodable code that corrects all single, and many double, two-bit errors is presented.