Research On Coverage And Interference Coexistence Issues In Rail Transportation Communication Systems

With the widespread deployment of rail transportation systems, the continuous development of the mobile internet and the further evolution of wireless communication technologies, there are many communication systems such as LTE, Wi-Fi were introduced in the specific communication scenario. To solve the communication problems of passengers in rail transportation systems represented by the high-speed rail and the metro has become a hotspot research in recent years. Although there are many researches about the coverage problem in rail transportation communication systems, the researches on coverage and interference coexistence issues in rail transportation communication systems from the spectrum view are still at its infancy and far too immature to guide the deployment of the communication network. Therefore, from the coexistence perspective, this paper introduces interference coexistence problems when the communication networks of high-speed rails and metros are deployed.1) For the hig h-speed railway scenarios, this paper uses the TDD-LTE High-speed Railway Private Network (HRPN) to realize high quality communication for high-speed trains and researches the interference coexistence problems between HRPN and Co-located Cellular Networks (CCN). To be specific, we first considerably improve the modeling of HPRN by introducing a new topology which can completely cover the long and narrow railway, new statistics which can precisely analysis every position’s performance during trains’ forward process, and finally a new shadow fading model with spatial correlation which can decrease the fluctuation between two adjacent positions. Subsequently, we propose two new anti-interference approaches to solve the serious problem of downlink interference between HPRN and CNN. Extensive simulation studies are performed which show that compared to existing approaches our improved modeling results in a more realistic and precise description of HPRN. It is also shown that the proposed anti-interference approaches are very effective.2) For the metro scenarios, this paper studies the interference on the Communication Based Train Control (CBTC) system when the passengers in carriages using MiFi devices to provide the personal Wi-Fi access. To be specific, we first investigate the coexistence scenario and system models. Then, based on the models, the performance loss of the CBTC downlink and the effectiveness of a proposed anti-interference algorithm with the Constant Contention Window (CCW) are studied. Research results show that the metro train indeed may be forced to stop by MiFi devices with the growth of the MiFi devices and the MiFi Data Frame Length (DFL). Additionally, our anti-interference algorithm can reduce the performance loss of the CBTC system without any change of the existing CBTC hardware equipments.In conclusion, this paper focuses on the research of the coverage and interference coexistence problems in rail transportation communication systems by selecting two typical scenarios:the high-speed rail and the metro. From the tepological structure, this paper covers the ground and underground; from the speed, this paper covers high and low speeds; from the network, this paper covers the centralized distribution network like HRPN and the distributed distribution network like the MiFi devices in the carriages. Therefore, this paper describes a comprehensive study sample for the coverage and interference coexistence research in rail transportation communication systems and also provides a good reference for future studies.