Delay Sensitivity Based Assignment of OVSF Codes for the Downlink DCH in WCDMA

Abstract

Abstract. A significant problern that deteriorates the performance of 3G W-CDMA systems is code blocking. The complete elimination of this phenomenon is accomplished only if a code reassignment procedure is employed. However, the relatively high total signaling delay for a single OVSF code reassignment combined with the strict delay requirements of some services makes the reassignment of some OVSF codes impractical. In other words, that a reassignment procedure cannot always be performed and therefore code blocking cannot be eliminated. In this paper, we introduce a new code selection scheme, named Delay Sensitivity Based Assignment (DSBA) , which takes into account the different delay requirements of the incoming calls. The performance of the proposed scheme is evaluated through event driven simulation and the results show a significant decrease in code blocking probability, especially for high rate calls, compared to other previously proposed schemes.