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This paper considers the Z-channel, which is known as a channel model for photon communication or semiconductor memory. A new decoding algorithm is proposed and discussed. Recently, studies have been made from various viewpoints on the asymmetrical error-correcting code suited to the Z-channel, which is considered interesting. One of the basic problems in the Z-channel is the performance and the decoding method when the cyclic code with various features is applied, but it has been investigated little. This paper presents first a maximum-likelihood decoding algorithm which is highly efficient for the cyclic code on the Z-channel. It is then shown that by providing a certain threshold for the algorithm, a higher-speed decoding is realized. It is shown also that by setting the threshold above a certain value, the computational complexity can be improved without sacrificing the maximum-likelihood property. Finally, it is demonstrated by numerical calculation that the decoding error probability is improved greatly by the decoding algorithm proposed in this paper, together with a drastic improvement in the computational complexity. [ABSTRACT FROM AUTHOR]

Submarine optical-fiber transmission systems are finding greater application in supporting an increasing volume of global-level data transmissions. As a result of this development, the power feeding equipment that supplies power to submarine repeaters now plays a key role in the operation of communication systems. To ensure that a constant current is maintained, pulse frequency modulation (PFM) is being used to control series resonant converters commonly employed in power feeding [1]. Power feeding systems supply rated current during stable operation. However, when they start supplying current, power feeding systems must gradually increase current from zero to the rated current. If cable failures occur, a dc current lower than the rated current or the dc current overlaid with an ac current is used to detect fault locations and wiring routes. PFM control must control operating frequencies from zero frequency to control output current from zero amperes. However, controlling the frequency from zero leads to such problems as the requirement of large smoothing filters, saturation of the transformer core, and generation of acoustic noise. To date, a number of solutions have been suggested. However, most of these solutions require the addition of components that handle electric power [2–5]. This paper reports a series resonant converter that employs PFM around rated current, and pulse width modulation (PWM) below the rated current to avoid inverter transformer saturation and acoustic noise at low frequencies and to make the use of small filler circuits practical [6, 7]. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(1): 1–10, 1999 [ABSTRACT FROM AUTHOR]