Efficient dual-association resource allocation model of train-ground communication system based on TD-LTE in urban rail transit

Wireless Local Area Network (WLAN) is currently used in the train-ground communication for the urban rail transit systems. Due to the high speed and limited frequency band, WLAN cannot satisfy the demands of city and intercity rail transit in the future. Time Division-Long Term Evolution (TD-LTE) technology allows to construct a flexible service environment compared with current WLAN based system. But with the development of the urban rail transit, the requirements of train-ground communication are increasing rapidly. So, if there are more than two trains running in the same RRU coverage area at the same time, the throughput capability is hard to satisfy the total requirements of the trains. In this paper, we first calculate the real throughput which includes no overhead. Then, a novel dual-association model based on TD-LTE is given. The novel model takes advantage of the fact that users can be associated with more than one RRU at the same time. The coverage diameter of single RRU, the overlap area of two neighbor RRUs and the headway distance are also considered in the novel model synthetically. The simulation results illustrate the effectiveness of the novel dual-association which can decrease the stress of the serving RRU obviously.