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# Data Coding Technique Using Low Correlation Sequences

IP.com Disclosure Number: IPCOM000074457D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 60K

IBM

## Related People

Hsiao, MY: AUTHOR [+1]

## Abstract

Conventional data coding techniques such as used on tapes or disks are of the following format: (Image Omitted)

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Data Coding Technique Using Low Correlation Sequences

Conventional data coding techniques such as used on tapes or disks are of the following format:

(Image Omitted)

The binary data bits are first converted into ECC (error correcting code) form by adding redundancy bits and then using any kind of recording technique, such as NRZI, PM, FM, MZR, etc. to convert the ECC and sync. bit into analogy waveforms. In decoding, the process is reversed as follows:

(Image Omitted)

In the present arrangement, the binary data is converted directly into the analogy waveform with built-in ECC capability. This is accomplished by using low-correlation sequences. The correlation coefficient p of two sequences A = (a(1), a(2)...a(n)) and B = (b(1), b(2),...b(n)) is defined as follows: Rho = # of agreement - # of disagreement over n If Rho is equal to zero, then the set of sequences is called orthogonal, e. g., the following Hadamard matrix sequence set. CD(1) = 1 1 1 1 -1 -1 -1 -1 CD(2) = 1 -1 1 -1 -1 1 -1 1 CD(3) = 1 1 -1 -1 -1 -1 1 1 CD(4) = 1 -1 -1 1 -1 1 1 -1 CD(5) = -1 -1 -1 -1 -1 -1 -1 -1 CD(6) = -1 1 -1 1 -1 1 -1 1 CD(7) = -1 -1 1 1 -1 -1 1 1 CD(8) = -1 1 1 -1 -1 1 1 -1.

Another example of low-coefficient sequence is a PN (Pseudo-noise) sequence which has p = 1/n. Both sequences are of low-correlation coefficient. In general, Rho </- 0.5 is considered to be low. The technique is applicable to all low-correlation sequences but the error correction or noise immunity capability of different sequences varies with Rho. The encoding process operates as follows: Let the binary data sequence of 8 bits (= 1 character) to be r...