Research On Train-ground Communication In Urban Rail Transit Based On IEEE802.11n

Now WLAN technology based on IEEE802.11a/b/g standard has beenincreasingly used in train-ground communication system of urban rail transit.However, with the increase of more new business requirements, put forward higherrequest for the train-ground communication technology. IEEE802.11n is a newwireless local area networks standard after IEEE802.11g, in order to improve thetransmission rate and throughput, IEEE802.11n standard improves the physical layerand MAC layer, The physical layer adopts MIMO-OFDM technology to increase thedata transfer rate, while the enhanced throughput of the network by optimizing thedata frame structure on the MAC layer. So it is applied in train-groundcommunication system of urban rail transit in this paper. We have carefully discussedthe possible problems and the corresponding solutions during the process of theimplementation of this standard in train-ground communication system.In this paper, we first introduce the key technologies used in IEEE802.11nstandard physical layer and MAC layer. Meanwhile we further study the compositionof train-ground communication system, and analyze and compare three businesssubsystems require train-ground wireless communication in urban rail transit, andcalculate the total bandwidth occupied by three business subsystems. Then we furtherverify the feasibility and superiority of the IEEE802.11n standards applied in thetrain-ground communication system in urban rail transit by comparing the simulationresults based on IEEE802.11g and IEEE802.11n train-ground communication system.Aiming to the problems existing in the traditional handoff scheme, we propose aon-board double antenna seamless handoff mechanism based on IEEE802.11n in thisthesis. In this scheme, the deployment of ground AP adopts cross double networkmode, both the front and rear of the vehicle install wireless transceiver devices, whichwork simultaneously in different networks, when a device performs handoff process,another is responsible for communicating with the ground AP. So it can ensure that atleast one train-ground communication data transmission channel at any time. Finally,the mathematical analysis and experimental simulation show that the proposedscheme in this paper can effectively reduce communication interrupt rate and delaycaused by the traditional handoff process, thus assuring the continuity of thetrain-ground communication data transmission and improving the performance of thetrain-ground communication network.