OVSF code assignment schemes at the forward link of WCDMA

Abstract

In 3G and beyond wireless networks orthogonal variable spreading factor (OVSF) codes are used to handle multimedia rates. These codes suffer from code blocking limitation which reduces the throughput and spectral efficiency of the system. Also, real time calls suffer from call processing delay. We propose a single OVSF code assignment design which utilizes offline optimum code selection algorithm so that the optimum code is available at the arrival of new call. The design finds the optimum code using a variable code index for all the parents of the available vacant codes. If a tie occurs for two or more parents for code index, the parent with the higher code index is chosen. The procedure repeats till a unique solution is reached. If still tie is not resolved the average elapse time of busy children of these parents can be used to choose single optimum code option. newline