Fast dynamic code assignment in next generation wireless access networks

In this paper, a fast dynamic code assignment (FDCA) algorithm is proposed to assign a single Orthogonal Variable Spreading Factor (OVSF)-code for a data rate requirement in next generation wireless access networks. Our algorithm uses the code assignment operation to evaluate the cost for an OVSF-code allocation. The cost is determined by maintaining the data structure that keeps track the number of available and occupied descendant codes of the code. Based on the cost assignment operation, FDCA algorithm can assign an OVSF-code by reassigning occupied descendant codes for a requested data rate. The OVSF-codes assigned by our algorithm is unrestricted with decreasing spreading factor. Moreover, two types of simulations and experimental measurements are presented. First, the proposed algorithm is applied on the OVSF-code assignment of restricted spreading vector. Our experimental results show that the number of reassigned OVSF-codes within FDCA algorithm is reduced comparing to other scheme proposed in the literature. Then, for serving higher data rate requirements, our scheme also shows significant improvement on the spectral efficiency over fixed code assignment scheme. q 2003 Elsevier Science B.V. All rights reserved.