MOBILE TRAIN RAILWAY COMMUNICATION

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1.1 INTRODUCTION

Mobile Communications Principles

Each mobile uses a separate, temporary radio channel to talk to the cell site. The cell site talks to many mobiles at once, using one channel per mobile. Channels use a pair of frequencies for communication. One for transmitting from the cell Site, the forward link, and one frequency for the cell site to receive calls from the users, the reverse link. Communication between mobile units can be either half-duplex or full-duplex. In case of half-duplex, transmit and receive communications between the mobile units are not at the same time.


1.2 WHAT IS GSM/R
GSM-R is GSM for Railways, a Global Communication Platform integrating the railways transport world wide. This GSM-Rail web-site provides information on the GSM-R Industry Group, its role as a conveyor of the GSM-R technology all over the world, its company members and representatives and its activities.
Additionally this site gives you overall information on the GSM-R technology, the associated EIRENE (European Integrated Radio Enhanced Network) standards and specifications, its advantages and the magnitude of the technology spread in the railway world.


1.3 The Mobile Station

The Mobile Station (MS) is the user equipment in GSM. The MS is what the user can see of the GSM system, the cellular phone itself. Production of Mobile Stations is done by many different manufacturers, and there will almost always be a wide range of different Mobile Stations in a mobile network. Therefore the specifications specify the workings of the MS in great detail. On the radio interface the specifications series 05 specify the workings of the link-level, defining the frequencies and the access methods between the MS and the network. Series 04 specifies the higher layers of the radio-interface, defining signaling procedures for call control, and information exchange. The radio-interface will be described in . In order to verify the conformal of the specifications by Mobile Stations, equipment must obtain type approval from the standardization body.


The Base Transceiver Station
The Base Transceiver Station (BTS) is the entity corresponding to one site communicating with the Mobile Stations. Usually, the BTS will have an antenna with several TRXs (radio transceivers) that each communicate on one radio frequency. The link-level signaling on the radio-channels is interpreted in the BTS, whereas most of the higher-level signaling is forwarded to the BSC and MSC. Speech and data-transmissions from the MS is recoded is the BTS from the special encoding used on the radio interface to the standard 64 Kbit/s encoding used in telecommunication networks. Like the radio-interface, the Abis interface between the BTS and the BSC is highly standardized, allowing BTSs and BSCs from different manufacturers in one network.