Highly Reliable Information and Communication Networks.

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As for Spread Spectrum (SS) Communication Systems, M-ary SS communication systems robust to carrier frequency offsets have been investigated. When there exist carrier frequency offsets, it is known that transimmted signal powers are decreased and sprious components appear at the receiving ends. In order to cope with these phenomina, it is required that the frequency spectrums after multiplication process at the receiver are 1) well spread, 2) have no peaks and 3) have low power desity spectrums. As orthogonal codes to realize these properties, cyclic H matrices, whose core matrices are made of M sequences are found to be adequate. Togehter with receivers designed for these codes, it is found that the total system is quite robust to carrier frequency offsets.The design of self-checking checkers for Hadamard codes have also been investigated. Hadamard codes are known to be quite useful in communication systems, signal processings and so forth. However, self-checking checker design for these codes have never been proposed. It is found that this design can be made by using the properties of difference sets when the degreee of Hadamard matrices are prime numbers of the form p=8m+3Finally, in the study of LSI tests, it is very important to have test inputs with strong randomness properties. Various randomness properties of partial fractions cut out from 2 dimensional random plane (M-plane) have been investigated to have quite excellent properties, superior than the sequences obtained from 1-dimensional M sequences.