Downlink orthogonal variable spreading factor code assignment method and base station system using the same

摘要

A downlink orthogonal variable spreading factor (OVSF) code assignment method is provided. It is determined whether a spreading factor required by a service request is greater than a remaining capacity of assignable spreading factors of a code tree. If not, the code tree is searched from a root until a node of a layer corresponding to the required spreading factor is reached and thus defined as a first node. During the searching, when a searched node is unassigned, the searching continues leftward in a lower layer; and when the searched node is in an assigned state, the searching continues rightward in a same layer of the searched node. It is determined, from the first node, whether any assignable code is available in the layer corresponding to the required spreading factor. If available, an assignable code is assigned to a communication service corresponding to the service request.

主权项

1. A downlink orthogonal variable spreading factor (OVFS) code assignment method, for use in a code division communication system, the method comprising:
a) in response to a service request, determining whether a spreading factor required by the service request is greater than a remaining capacity of assignable spreading factors of a code tree; b) when it is determined that the required spreading factor is smaller than the remaining capacity, searching the code tree from a root of the code tree until a node of the code tree in a layer corresponding to the required spreading factor is reached and thus defined as the first node; during the searching of the code tree: when a searched node of the code tree is in an unassigned state, the searching continues leftward in a lower layer of the code tree with respect to the searched node; and when the searched node is in an assigned state, the searching continues rightward in a same layer of the searched node; c) determining, from the first node, whether any assignable code is available in the layer corresponding to the required spreading factor; d) when the determination in step (c) is positive, assigning an available assignable code to a communication service corresponding to the service request; and e) when the determination in step (c) is negative, searching a layer that is k layer lower than the layer corresponding to the required spreading factor, from a layer for k=1 to a last layer of the code tree, until 2k assignable codes are found, and assigning the 2k assignable codes to the communication service corresponding to the service request.