Multiplex communications – Generalized orthogonal or special mathematical techniques – Particular set of orthogonal functions
Reexamination Certificate
1999-08-05
2004-03-02
Nguyen, Chau (Department: 2663)
Multiplex communications
Generalized orthogonal or special mathematical techniques
Particular set of orthogonal functions
C370S335000, C370S342000
Reexamination Certificate
active
06700864
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to the field of generating orthogonal codes.
2. Description of Related Art
Orthogonal code generators for Quadratic Residue, Walsh-Hadamard, Twin Prime, etc. codes are well known in the art. However, each code generator has requirements that restrict the code length to specific values. For example, for the Walsh-Hadamard code, code lengths of 2
N
for integer N>0 are defined. Code lengths of non-powers of 2 are undefined. Thus, there is a need for new technology to generate code lengths for orthogonal codes with greater flexibility.
SUMMARY OF THE INVENTION
The invention relates to a generalized apparatus and method for generating orthogonal codes to desired lengths by a new overspreading technique. Overspread orthogonal codes are generated by code-multiplying input orthogonal codes. The input orthogonal codes may be generated by any method and the overspread orthogonal code length is the product of the lengths of the input orthogonal codes. In telecommunication application, for example, a communication signal may be spread by a first orthogonal code and then overspread by a second orthogonal code. The output of the overspreading process may be further overspread by a third orthogonal code and so on until a desired code length is obtained. Thus, orthogonal code lengths unobtainable by any of the known orthogonal code generators may be generated using the overspreading technique with code-multiplication using codes generated by the same or different orthogonal code generators to obtain a desired code length. Additionally, different orthogonal codes of the same lengths may be generated using the overspreading technique.
REFERENCES:
patent: 5103459 (1992-04-01), Gilhousen et al.
patent: 5815527 (1998-09-01), Erving et al.
patent: 5995497 (1999-11-01), Gerakoulis
patent: 6041034 (2000-03-01), Fukumasa et al.
Gerakoulis Diakoumis Parissis
Ghassemzadeh Saeed S.
AT&T Corp.
Brendzel Henry T.
Hyun Soon-Dong
Nguyen Chau
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