ORTHOGONAL VARIABLE SPREADING FACTOR (OVSF) CODE ASSIGNMENT
The invention includes a system and methods for orthogonal variable spreading factor (OVSF) code assignment, de-allocation and code tree pruning. The invention also includes OVSF code identification and storage schemes. Embodiments are provided for code tree pruning, code assignment and de-allocation. These embodiments apply to both slotted and non-slotted code division multiple access systems.
1 . A method for reassigning codes of an orthogonal variable spreading factor (OVSF) code tree, the method comprising:
assigning a unique integer identifier to each code in the code tree;
creating a vector, wherein an integer index associated with each value stored in the vector corresponds to the unique integer identifier assigned to each code in the code tree; and
storing in a location of the vector a code word, wherein the code word indicates an assignment status of the corresponding code.
2 . The method of claim 1 , wherein the code word comprises two bits.
3 . The method of claim 2 , wherein a first bit of the code word represents if the code corresponding to the code word is blocked from assignment.
4 . The method of claim 3 , wherein a value of zero in the first bit of the code word indicates that the code corresponding to the code word is not blocked from assignment.
5 . The method of claim 4 , wherein if the first bit of the code word has a value of zero and the second bit of the code word has a value of one, the code corresponding to the code word is not available for assignment in a time slot for which codes are being assigned.
6 . The method of claim 3 , wherein a value of one in the first bit of the code word indicates that the code corresponding to the code word is blocked from assignment.
7 . The method of claim 2 , wherein a second bit of the code word represents a number of nodes blocking the code corresponding to the code word.
8 . The method of claim 7 , wherein a value of zero in the second bit of the code word indicates that the code corresponding to the code word is blocked by one node in the code's sub-tree.
9 . The method of claim 7 , wherein a value of one in the second bit of the code word indicates that the code corresponding to the code word is blocked from assignment by two nodes in the code's sub-tree.
10 . The method of claim 1 wherein the unique integer identifiers assigned to codes belonging to a single spreading factor are contiguous.
11 . A radio network controller (RNC) configured to:
reassign codes of an orthogonal variable spreading factor (OVSF) code tree comprising:
a processor configured to:
assign a unique integer identifier to each code in the code tree and create a vector, wherein an integer index associated with each value stored in the vector corresponds to the unique integer identifier assigned to each code in the code tree;
a memory configured to store the vector and a code word, wherein the code word indicates an assignment status of the corresponding code.
12 . The RNC of claim 11 , wherein the code word comprises two bits.
13 . The RNC of claim 12 , wherein a first bit of the code word represents if the code corresponding to the code word is blocked from assignment.
14 . The RNC of claim 13 , wherein a value of zero in the first bit of the code word indicates that the code corresponding to the code word is not blocked from assignment.
15 . The RNC of claim 14 , wherein if the first bit of the code word has a value of zero and the second bit of the code word has a value of one, the code corresponding to the code word is not available for assignment in a time slot for which codes are being assigned.
16 . The RNC of claim 13 , wherein a value of one in the first bit of the code word indicates that the code corresponding to the code word is blocked from assignment.
17 . The RNC of claim 12 , wherein a second bit of the code word represents a number of nodes blocking the code corresponding to the code word.
18 . The RNC of claim 17 , wherein a value of zero in the second bit of the code word indicates that the code corresponding to the code word is blocked by one node in the code's sub-tree.
19 . The RNC of claim 17 , wherein a value of one in the second bit of the code word indicates that the code corresponding to the code word is blocked from assignment by two nodes in the code's sub-tree.
20 . The RNC of claim 10 wherein the unique integer identifiers assigned to codes belonging to a single spreading factor are contiguous.