標題: Reducing internal and external fragmentations of OVSF codes in WCDMA systems with multiple codes
作者: Chao, CM
Tseng, YC
Wang, LC
資訊工程學系
電信工程研究所
Department of Computer Science
Institute of Communications Engineering
關鍵字: mobile communication;OVSF;personal communication services;third generation (3G);WCDMA;wireless communication
公開日期: 1-七月-2005
摘要: In the third-generation partnership project technical specification, orthogonal variable spreading factor (OVSF) codes are used as channelization codes. The use of OVSF codes can provide variable data. rates,to flexibly support applications with different bandwidth requirements. Most works in the literature assume that only one single OVSF code is used to support one connection. This may sometimes waste the scarce wireless bandwidth since the allocated bandwidth will increase exponentially as the spreading factor decreases, i.e., a user may be "overserved". In this paper, we consider the possibility of using multiple OVSF codes to support a connection. We show how using multiple codes can reduce the internal and external fragmentations of an OVSF code tree. The tradeoff between bandwidth utilization and hardware complexity of a multicode system is analyzed. The result shows that using two or three codes will be quite cost effective. Several multicode assignment and reassignment strategies, namely, random, leftmost, crowded-first-space, and crowded-first-code, are proposed based on such an environment. Our simulation results show significant increase in code tree utilization and significant reduction in code blocking probability by using the crowded-first-space and crowded-first-code schemes.
URI: http://dx.doi.org/10.1109/TWC.2005.850332
http://hdl.handle.net/11536/13525
ISSN: 1536-1276
DOI: 10.1109/TWC.2005.850332
期刊: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS
Volume: 4
Issue: 4
起始頁: 1516
結束頁: 1526
顯示於類別:期刊論文


文件中的檔案:

  1. 000232116500035.pdf