Region division and improving performance of dynamic code assignment scheme

Abstract

Most of CDMA wireless networks require the use of orthogonal variable spreading factor (OVSF) codes. OVSF codes are the limited resources at the downlink of CDMA networks. Code blocking is the major limitation of the OVSF codes. The efficient single code assignment scheme named dynamic code assignment with region division is proposed to minimize the code blocking. In the proposed scheme, the OVSF code tree is divided into two regions namely primary region and secondary region. Prior to be handled by secondary region, the call is kept in the primary region and optimal code finding starts in the secondary region. The code checking starts at the call arrival unlike traditional dynamic code assignment where offline table is maintained for finding optimal vacant code. The scheme is divided into two parts. In the first part, the best code is found using crowded first assignment. If not possible, dynamic code assignment with region division is used. The primary and secondary region management is also discussed. Simulation results illustrate the superiority of the proposed design with existing novel methods.