OVSF code system and methods
AssigneeInterDigital Communications Corporation
InventorsYounglok Kim, Jung-Lin Pan
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Abstract
A code indexing method for orthogonal variable spreading factor (OVSF) codes introduces a single number mapped to the each code. The new code number itself not only provides the code signature, but it is also used for the OVSF code generation. In addition, it provides easy and fast generation of the available code list without the help of look-up table. This capability improves the dynamic code assignment.
Claims15
In a communications system where OVSF codes are selected from a set of Walsh codes represented as a binary tree having multiple layers such that a zeroth layer has one Walsh code and each successive layer has twice the number of Walsh codes as the layer it succeeds, the method comprising:
- selecting an OVSF code from the set of Walsh codes using an index p where p represents the (p+1)−2i th Walsh code of the ith layer of Walsh codes where i is an integer such that 2i≦p<2i+1.
In a communications system where OVSF codes are used and selected based upon a spreading factor SF where SF is a positive power of 2, the method comprising:
- selecting an OVSF code using an index p from a set of codes where:
- for each integer p>3 the corresponding code is defined by C(p)=C(m+2)⊕C(k), with p=2·k+m, where k and m are integers with m=0 or 1, and
- the codes corresponding to p=1, 2, or 3 are C(1)=[1], C(2)=[1,1], and c(3)=[1, −1]
- whereby each p represents the (p+1)−2i th code of an ith layer of codes for SF=2i where i is the unique integer such that 2i≦p<2i+1.
Dependencies are inferred from the claim text.