IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 21, NO. 10, DECEMBER 2003
Handoff Algorithms in Dynamic Spreading WCDMA
System Supporting Multimedia Traffic
, Student Member, IEEE
, Jonathan C. L. Liu
, Senior Member, IEEE
, and Yuehao Cen
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.
Dynamic spreading factor, multimedia traffic,
power control, quality-of-service (QoS), soft handoff, wideband
code-division multiple-access (WCDMA).
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
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
, 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