Abstract
Many data services are available in third-generation (3G) mobile communication systems and may have different data rates on transmission. It is important to maintain the link quality and performance when higher data rate is served. For example, real time video service is one of the services which require high data rate and high transmission quality. Unfortunately, the higher data rate we use, the lower processing gain we get, and fewer ability of anti-multiple- access-interference (MAI) we will have. Not only the processing gain, but also the carrier-to-interference ratio (CIR) will influence system performance. Simply speaking, when the CIR degrades due to either traveling away from the base-station (BS) or being shadowed by structures, the service rate must decrease to increase the processing gain for better link quality. By observing BER, we can discuss the relationship between propagation length and maximum available data rate under the forward link assumption for 3G systems. The results can be used to limit user’s data rates according to user’s positions. It is a helpful reference to resource management problems.