Interleavers for digital communications

Details Interleavers for digital communications Interleavers for digital communications

1983-07-28

1985-12-17

Atkinson, Charles E.

Excavating

371 40, G06F 1110

Patent

active

045596255

ABSTRACT:
An improved method and apparatus for interleaving block codes exploits helical symmetry whereby correspondingly positioned code symbols of code words of length n interleaved to depth i, i<n, are separated on the channel by .alpha.i+.beta. symbol intervals where 1+.gamma..gtoreq.i is averaged over the i correspondingly positioned symbols and .alpha.and .vertline..beta..vertline. are integers >1. The requirement for synchrony is reduced to a period counted modulo n instead of mod (n.times.i). For the case i=n-1, the total interleaving delay is reduced to 2(n-1)n and phase dependence of burst error onset is minimized. The performance of the de-interleaver is enhanced through a pseudo fade detector implemented by creating erasures prior to decoding, at certain positions for codewords subsequent to confirmed error. Synchronization of interleaver and de-interleaver is accomplished in apparatus which inspects all c contiguous bit patterns corresponding to a c bit synch symbol. To each c contiguous bit pattern of the data stream there is associated a probability counter for incrementing when the synch pattern is detected and decremented otherwise. Maximum probability establishes synch.

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Ramsey, John L., Realization of Optimum Interleavers, IEEE Trans. Inf. Theo., V.IT-16, No. 3, pp. 338-345, 1970.
Clark and Cain, Error-Correction Coding for Digital Communications, Plenum Press, 1981, pp. 345-352.

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