Isotropic air-interface in TD-SCDMA: uplink synchronization control and its environment-dependent performance analysis

This paper addresses the issues on implementation of an isotropic air-link technology- for future 4G wireless. One straightforward way is to use open-loop and closed-loop uplink synchronization (ULS) control techniques to turn asynchronous uplink back to synchronous operation mode. The use of ULS control can greatly enhance bilateral data transmission throughput in both uplink and downlink channels of a mobile cellular as a direct result from improved transmission imparity between them. This is especially important for some applications where the traffic in the both links should be made equally high, such as video conferencing. This paper will also introduce a modeling method to analyze performance of ULS control in a mobile cellular system. It should be noted that, although this paper's study is carried out under the TD-SCDMA framework, the method can be equally applicable to any TDD-based 3G and 4G wireless systems that choose ULS control as the means to achieve isotropic air-link transmission. A numerical analysis based on propagation delay estimation will be used to derive probability of successful ULS control under consideration of the impact of different channel environments, such as reflection coefficients, propagation patterns, attenuation gradient and cell size, etc.