Adaptive Fuzzy-based Power Control and Transmission Rate Management in Multimedia CDMA Cellular Systems

Y.-L. Chen, Y.-S. Lin, J.-W. Wang, and J.-H. Wen (Taiwan)

Keywords

Adaptive fuzzybased, power control, and transmission rate.

Abstract

For non-real time services, since delay is not a crucial constraint, they can be transmitted by using variable rates. On the other hand, in CDMA systems, different transmission rates have different impact on received signal-to-interference ratios (SIRs), which in turn affect the power control adjustments. This fact raises the problem of how to adjust the power and rates for individual users so that higher spectral efficiency can be achieved. Therefore, combining power and rate control is necessary in a multi-rate multimedia system. Recently, this issue has been receiving much attention [2-5]. In the literature, a number of fuzzy-based power control schemes have been proposed for systems with a single service. However, emerging CDMA cellular systems are expected to include multimedia services. In such systems, different services have different quality of service (QoS) requirements, such as minimum transmission rates and tolerable delays. This paper introduces a novel adaptive fuzzy-based power control that is associated with a transmission rate management scheme to support multimedia services in CDMA cellular systems. Simulation results show that the new scheme outperforms the original selective power control (SPC) method in several performance measurements, such as outage probability, average transmission rate, probability of unsuccessful transmission, and probability of changes in transmission rates. DS-CDMA systems may use one of the following techniques to support multi-rate transmission. One technique uses different chip rates to achieve multi-rate transmission. Another technique spreads different transmitted signals with different transmission rates for different services over a same amount of bandwidth; this is the system considered in this paper. Although many researchers deal with the various transmission rates as a real value, in practical applications, feasible transmission rates are limited to some discrete values. Thus, in this paper, we will focus on power control problems with discrete rate values.

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