Queue-aided BLRU scheme for orthogonal variable-spreading-factor code assignment in 3G WCDMA

In 3G WCDMA, orthogonal variable-spreading-factor (OVSF) codes are valuable and scarce resources. Some single-code and multicode assignment algorithms have been proposed to support as many users as possible. Most of the algorithms suffer from a "code-set fragmentation" problem, which definitely increases the call blocking probability (CBP) of a system. In order to resolve this issue, code-exchange and reassignment policies is applied, but system complexity is also increased. In this paper, we propose a queue-aided best-fit LRU (QBLRU) code assignment scheme to improve system utilization and to obtain lower CBP than that of dynamic optimal reassignment schemes. Simulation results show that the QBLRU scheme has the lowest CBP and the highest utilization and it is an efficient OVSF code assignment scheme.