Method for generating OVSF codes in CDMA multi-rate system
AssigneeAccton Technology Corporation
InventorGuu-Chang Yang
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Abstract
In this invention, a new tree-structured generation method for obtaining orthogonal variable spreading factor (OVSF) codes that preserve orthogonality between different rates and spreading factors (SF) based on Gray code labels in a CDMA system is presented. Each OVSF code is uniquely associated with a Gray code label. An efficient method for deciding if the code is a mother code or children code of the other code without searching an entire code tree is proposed. Furthermore, by taking advantage of the Gray code labeling, each OVSF code can be generated directly from a generating matrix instead of being generated recursively using a tree structure. An OVSF code reassignment method with Gray code labeling is also given.
Claims11
A spreading method for use in a CDMA multi-rate system, comprising the steps of:
- (A) coding message codes using Gray codes;
- (B) generating a generating matrix, Gi, based on formed Gray codes;
- and
- (C) multiplying the message coded by the Gray codes with the generating matrix for generating an OVSF codes with a specific length.
A method for determining a mother code and a children code in a CDMA multi-rate system, comprising the steps of:
- (A) using a plurality of Gray codes as labels of a plurality of OVSF codes;
- and
- (B) determining whether a first OVSF code and a second OVSF code have a relation of a mother code and a children code by determining whether a label of said first OVSF code is a prefix of a label of said second OVSF code.
A method for exchanging OVSF codes in a CDMA multi-rate system, comprising the steps of:
- (A) using a plurality of Gray codes as labels of a plurality of OVSF codes;
- (B) performing a modulo-2 operation on the Gray code label of a first OVSF code and the Gray code label of a second OVSF code for generating a label of a third OVSF code;
- and
- (C) performing a modulo-2 operation on said third OVSF code and said first OVSF code for generating said second OVSF code.
Dependencies are inferred from the claim text.