SLR needed a modern and reliable digital communication system to replace its out-of-date radio system. SLR does not possess any LTE radio frequencies itself, but in 2018 the government approved the building of the railway IRTS based on MCPTT (Mission Critical Push-to-Talk) over LTE technology.

The IRTS covers the entire railway network including all the stations, trains, level crossings, SLR maintenance and security units, and the three regional control centres in Colombo, Nawalapitiya and Anuradhapura. It provides voice and data communications for onboard train staff, railway station staff, railway maintenance staff and control room dispatchers and managers. It supports seamless communications for trains operating up to speeds of 160 km/h.

The main purposes of the IRTS are: to achieve safer train operations by avoiding collisions and other disruptive occurrences; to enhance railway operations by providing better train control and related decision making; to maintain good coordination between train operations staff; and to enable better management decisions relating to train operations.

Sri Lankan mobile network operator Dialog won the bid to build the IRTS. Hytera was chosen as Dialog's business partner to provide the end-to-end MCPTT railway dispatching service, along with all the required radio and telephone devices.

A key reason for Hytera's selection is that it is one of the few communications vendors able to provide an end-to-end solution for railways covering train cab radios, handheld push-to-talk (PTT) mobile phones, indoor IP telephones, an MCPTT-compliant network management and service platform, and a railway dispatching system.

Hytera was awarded the contract thanks to its ability to provide this end-to-end solution, along with its strong track record in meeting the communication needs of mass transit systems, including railways and metros. SLR also appreciated Hytera's customer-oriented approach and flexibility over supporting the introduction of customized railway specifc features, as well as the overall value provided by its cost effective solution.

Hytera supplied 20 dispatching controllers, three system management devices, three voice recording devices, 1,239 $D1000 IP telephones with MCPTT features for indoor use, 275 CZT902 train cab radios. and 1,951 PNC550 PTT handheld mobile phones.

All the devices enable individual, group and emergency calling, and text messaging, to provide flexible and effcient communications over LTE based on the Android operating system. Priority is built into the solution to ensure the most urgent calls are transmitted frst based on an agreed priority hierarchy set by SLR.

The system supports individual calls between dispatching controllers and station masters, train drivers and train quards, The dispatching controller can also make a broadcast call to all station masters and train drivers.

The CZT902 train cab radio supports dual SlM, GPs location services and consumes less power than the previous model. Train drivers can make MCPTT private and group calls to controllers, other drivers in the area, rail staff on the same train, and make MCPTT emergency calls to dispatching controllers.

The cab radio also supports a number of railway specifc features like: location dependent addressing, which enables the driver to call a different controller depending on the location ofthe train; functional addressing, which allows a call to be made to based on job function, such as train driver or guard; link assurance signal, which provides reassurance to the driver that the radio link is working; shunting mode and shunting emergency calling; and so on - all based on MCPTT technology over LTE.

The PNC550 ruggedized (MlL-STD-810 G and lP68) mobile PTT handsets are used by station staff, maintenance crews and security quards. The PNC550 integrates full smartphone functionality and features a long battery life of around 18 hours talk time. Dual cameras allow users to send multimedia messages.

The three railway control centres use the Hytera dispatching system, system monitoring device, and voice recording device.For railway stations, SD1000 lP desk telephones were applied. As the latest model IP telephone that supports WAN/LAN and LTE and features a 10.1-inch IPs multi-touch screen, SD1000 enables conference calls, hands free talking, caller lD display and caller switching among other features.

The dispatching device provides call lists and request functions and the ability to list calls according to priority. Dispatchers can send and receive text messages, make emergency calls, and have an override function. The system monitoring device enables users to log in/out, provides security, network topology, alarm and subscriber management. The voice recording device records all calls, user lDs, along with search facilities to locate historical voice and messaging.