Long distance radio networks solution

General radio communication principles

Radio communication covering the distance of a number of kilometers or whole regions can be dealt with in a number of ways. The reason for this is the necessity of dispatching – vehicle or dispatching – stop panels or other kinds of communication. The following kinds of communication are taken into account:

•  private radio network PMR (private mobile radio), e.g. the EPIS_FDNET supplied by our company
•  GSM/GPRS/3G networks of various mobile network operators
•  TETRA radio communication system
•  today the newly developed LTE system is also possible (the technology is being introduced to the market)

Choosing the right radio network depends on the size of the area and on the requirements regarding the safety and reliability of the communication system in exceptional situations in the area.

Private network of transport companies

Private radio networks can be used to transfer both voice and data. They are usually used to transfer sound, a (phonic) network in the form of a trunk network, i.e. a network containing one control channel and a number of voice channels. The control channel is used to manage voice communication on the other channels.

Today’s dispatching systems requiring vehicle position surveillance also have to obtain data regarding e.g. the position of the vehicle, etc… This is the reason why we have developed a new combined radio network EPIS_FDNET (EPIS Fonique Data NETwork) for public transportation companies. This network is based on technologies integrating voice and data transfers on one channel including solving preference at crossroads.

By using this network, it is possible to significantly lower expenses on building two radio networks – a phonic network and a data network – because they are built as a single network using one vehicle radio station. This is made possible by using a radio communication adapter and a radio modem in the vehicle.  The modem can be supplied as a separate unit or it can be a part of the EPIS units (both the EPIS 2.45 multipurpose digital annunciators and the EPIS 4.0x on-board computers).

The main advantages of the EPIS_FDNET radio network supplied by our company:

•  a new radio network can be built gradually on the basis of the current network.
•  one vehicle radio station is used for both voice and data communication.
•  only the bought frequencies have to be paid for (a low-cost system).
•  a possibility of communication using short data messages of the size from 160 characters up (SMS) or coded messages
•  quick and regular detection of vehicle positions and other telemetric information
•  a possibility of managing crossroads preference at a reserved frequency (switching the transmitted performance according to the frequency).
•  managing the radio network from multiple radio bases
•  a customized solution – the supplier is also the creator of the control HW and SW, therefore it is possible to modify the radio network according to the needs of the user.
•  an IP technology used to transfer data or voice between the dispatching and the base(s).
•  a radio modem and a communication adapter are integrated in the EPIS system or it can be supplied as an independent unit, it can also be embedded in a radio station (company vehicles).
•  various data transfer speeds according to the required function (calling, reading a short tachograph loop, generating automatic messages, etc.)
•  calling the vehicles to determine their positions at the speed of up to 150 vehicles / 10 seconds depending on how the radio channels are organized.
•  higher vehicle safety – if the server stops working the radio network works independently in emergency mode using voice communication.
•  automatic roaming (base switching) – a radio base for both data and voice communication is chosen automatically based on the quality of received signal.

To use the above possibilities successfully it is necessary to use a radio station that is able to start transmitting data in a few milliseconds. The description of the EPIS FD NET radio network can be found here.

Pic. no.1: The structure of a realized FDNET network using three radio bases.

Presently we are starting to study digital radio networks for the purposes of using them in transportation information systems in city agglomerations using the ETSI standard (European Telecommunications Standards Institute) and the DMR system (Digital mobile radio). We will inform you about the suitability of using this system in our FD NET radio network.

GSM/GPRS networks

Using GSM/GPRS/3G networks is suitable when the size of the required area is such that it is not possible to cover it using multiple radio bases and building these bases would be too expensive. The second reason can be the amount of transferred data because this type of networks has significantly higher capacity than classic radio networks.

 From the point of view of data transfers we have three possibilities:

• using a public IP address which is very expensive and cannot be used for the purposes of vehicle surveillance.
• using „mini internet“ networks, where device IP addresses create a virtual data network. These addresses are assigned by the operator and they are bound to SIM cards. The operator usually demands “some” payments.
• APN systems (Access Point Name), where outer objects (vehicles, panels, etc.) are parts of the inner network of the operator. The APN point creates a gate between the virtual inner network inside GPRS (UMTS/3G) and the network of the operator (another data network).

The “mini internet“ principle is used for small networks where it is not necessary to build an access channel and all data communication is realized via individual GSM modems (If one is central it is necessary to reserve a much higher amount of data for it). It is suitable for using a small number of stations integrated in this type of network.

Using the APN access point is suitable for large systems (e.g. 10 and more stations) where the communication units can be run in the scope of one network and their IP addresses can be solved using “a radius server” (assigns IP addresses according to an IMEI identificator – the number of a modem in a communication device).

We run both types described above and we are able to propose a suitable solution according to the demands of the customer.

TETRA radio communication system

The TETRA (TErestrial Trunked RAdio) network is a professional communication network used in some areas in the Czech Republic. The TETRA technology is based on the principles of modern TDMA networks of the GSM type with the difference that it enables the user to combine the main advantages of classic analog radio networks with the advantages of stations communicating in digital networks. One of the biggest advantages of TETRA radio stations is their independence of the network in mobile traffic. This advantage was borrowed from classic radio stations.

Our devices can be connected to this type of network by using a suitable interface (most often the RS 232 interface – so called COM).

LTE networks

LTE (a shortcut of the English 3GPP Long Term Evolution) is a technology developed for high-speed wireless connection. Formally, it is a technology belonging to the 3G standard. The theoretical download speed (downlink) is 172,8 Mbps and the upload speed (uplink) is 57,6 Mbps.

Using an LTE network is suitable in cases when it is necessary to transfer large amounts of data. Using LTE networks in the Czech Republic is limited because of the insufficient mobile network operator signal coverage.