Dynamic simulation to study forward link capacity improvement methodologies for wireless CDMA systems.

摘要

The ever increasing portability in everyday life due to today's widespread use of portable computing devices such as notebook PCs, Handheld PCs and PDAs, etc. has pushed the wireless industry, once a realm of only voice communications with minimal data requirements to a wireless environment with access requirements for a mix of different wireless bearer services in addition to voice conversations; including but not limited to packet data, video telephony, telemetry, audio and video streaming, Telnet, voice messaging, web browsing, email, navigation, remote control services, monitoring, FTP, DB access, frozen pictures, paging, Usenet and many other interactive and non-interactive applications. In most such environments, it is expected that the user will require more capacity data for the forward link than for the reverse link. This makes forward link capacity the system capacity bottleneck. Most of the third generation wireless systems being deployed to support such capabilities use CDMA schemes.; This research investigates means to increase the forward link capacity of the CDMA wireless systems. This increase is achieved through degradation of other system performance metrics such as data rate, coverage, blocking and dropout probability. To reach this goal a comprehensive dynamic system simulator that can evaluate these system performance metrics simultaneously was suggested and implemented.; Two methods to enhance forward link capacity by degrading the quality of service (dropping the data rate) are suggested and compared for different propagation environments. The results show that in sever propagation environments dropping the data rate for mobile terminals requiring the highest base station forward link power will increase the forward link capacity the most.; Methods to increase forward link capacity by degrading coverage and other performance metrics are also presented. Results showing a compromise between capacity and coverage as a function of the base station power, maximum connection power and percentage of the base station power are presented.; It is also shown that soft handoff threshold can be used to make this compromise between the capacity and coverage in the forward link and that blocking. threshold plays an important role in deciding capacity, blocking probability and the dropout rate in the forward link.; A simple and powerful mathematical model for the forward link power based blocking in CDMA systems is also developed. In comparing the simulation results obtained from the developed dynamic system simulator to the data obtained from this mathematical model it is clear that both the dynamic system simulator and the mathematical model are in good agreement and results obtained using both methods are a very close fit.; Thus, this work should serve as a good treatise with practical implications that the CDMA wireless industry could readily apply as a means of increasing forward link capacity and measuring the level of any detrimental quality of service and coverage impacts for the networks and customers in this ever-increasing competitive service oriented wireless environment.