spaper11 - 1652 IEEE JOURNAL ON SELECTED AREAS IN...

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1652 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 21, NO. 10, DECEMBER 2003 Handoff Algorithms in Dynamic Spreading WCDMA System Supporting Multimedia Traffic Ju Wang , Student Member, IEEE , Jonathan C. L. Liu , Senior Member, IEEE , and Yuehao Cen Abstract— The undergoing third-generation wireless network needs to support the integration of voice and multimedia data services with varying quality-of-service (QoS) requirements. It is critical that the least bit-error rate (BER) for voice traffic, World Wide Web (WWW) traffic, and streaming video traffic be guaran- teed at all time. In this paper, we discussed the integration of soft handoff and dynamic spreading factor in wideband code-division multiple-access system in supporting multimedia traffic. The contribution of our work is twofold. First, the processing time of the handoff request is analyzed. We found that intensive mobile handoff might consume significant amount of access channel time and increase the delay of handoff. We, therefore, proposed a batch mechanism such that multiple handoff requests could be processed simultaneously. The average delay is reduced from 1.12 s to 800 ms at heavy handoff rate. Our second contribution is a new resource allocation algorithm, where the spreading factor and transmission power for the handoff mobiles are jointly considered to maximize the throughput. The BER requirements for the handoff mobiles and the target cell are maintained during the handoff process. The original problem is formulated into a nonlinear programming format. We proposed a procedure to simplify it into a linear constraint problem, which is solved by a revised simplex method. Numerical results show a 25% increase in throughput for WWW traffic and a 26% improvement for the video traffic. Index Terms— Dynamic spreading factor, multimedia traffic, power control, quality-of-service (QoS), soft handoff, wideband code-division multiple-access (WCDMA). I. INTRODUCTION E NCOURAGED by the success of second-generation (2G) cellular wireless network, researchers are now pushing the third-generation (3G) standard to support a seamless integration of multimedia data services, as well as voice service. However, multimedia data traffic is more demanding than voice service, both in data rate and maximum tolerated bit-error rate (BER). For example, streaming video requires a low BER, less than 10 and a moderate data rate (usually higher than 64 kb/s). The bottom-line is that the minimum BER and data rate require- ments for all admitted connections must be satisfied at any time. Otherwise, the system will not guarantee the performance. Code-division multiple-access (CDMA) systems have been intensively studied in the literature, and was considered as a major player in the undergoing 3G system. In our previous study [7], we had proposed a dynamic spreading scheme such that Manuscript received October 15, 2002; revised May 1, 2003. J. Wang is with Virginia Commonwealth University, Richmond, VA 23284
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This note was uploaded on 11/30/2011 for the course CIS 6930 taught by Professor Staff during the Fall '08 term at University of Florida.

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spaper11 - 1652 IEEE JOURNAL ON SELECTED AREAS IN...

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