TTC: A new Canadian TETRA operator

Toronto Transit Commission has picked TETRA as its metro communications technology. Richard Martin paid it a visit to hear about its progress so far 

Toronto's metro, bus and trolley-car service - the third-most-heavily used transit system in North America, after those of New York and Mexico City - is operated by the Toronto Transit Commission (TTC). The TTC metro system consists of four lines and 69 stations, and the company has selected a TETRA communications technology as its new LMR solution. 

The transit system has grown with the city, overloading the metro's legacy analogue and MPT1327 systems. After looking at narrow banding options, TTC realised that the greater capacity of a trunked digital system would be needed to make the best use of the available frequencies. It looked at a range of digital LMR systems such as DMR, dPMR and P25, but found TETRA to be the best fit for its requirements. TTC wanted to use an established technology supported by open standards to avoid being locked into one supplier, and  it needed full interoperability. The technology had to be one with a long service life and with a proven record in transit. Its engineering team wrote a specification based on TETRA, and seven companies responded. Sepura won the contract and supplied TTC with 34 base stations. 

TTC enabled an impressive 535 million journeys in 2014 

TTC's view of the TETRA programme 
The key members of TTC's communications engineering team responsible for TETRA are project manager Milan Vignjevic and senior designer Jeff Thurston. They have been involved with the programme from the outset and in the early days attended TETRA-related workshops in North America and overseas. 

"TTC relies heavily on radio communications to communicate with subway trains, track-level workers and surface vehicles. From a high-level perspective, many of our requirements fit within the critical communications/mission-critical models, including high-availability network with built- in redundancy, high reliability, point-to-multi-point (group calls), and fast set-up time for emergency calls," say Vignjevic and Thurston. 

TTC notes TETRA's capability to set priorities and segment the network into groups, both of which are important in communicating in emergency situations. 

TETRA can be adapted for transit operators. It was very important to TTC to have an open API to interface to a customised despatch system, and to reuse the existing control system and processes. 

Currently, only maintenance teams are using the TETRA handsets while the radios are installed in the trains. 

How is the TETRA network used today in terms of voice and data? "We require both voice and data capability. While the trend in data is toward ever-increasing speeds, a lot of our applications are for telemetry and control, which can fit within low-data-rate communications. Currently, data over radio is used to communicate telemetry and events from our subway trains to servers. This will soon go over TETRA. Beyond that, we see growing applications in SCADA and device monitoring where data over TETRA may be more economical than terrestrial communications. 

"With respect to the subway system, TTC's major challenge is to provide uninterrupted transit service during regular service hours. This makes maintaining the system in good state of repair a challenge as maintenance crews working in the tunnel must not delay trains. Radio communications are used extensively among work crews and train operators, and this ability to communicate at track level is paramount to TTC operations and safety protocols. TETRA addresses these requirements and was found to be the best solution for TTC," say Vignjevic and Thurston. 

Deployment and commissioning
All TETRA base stations are now installed and most are active. "The installation process and SAT testing went very smoothly. Separating procurement into two contracts for the infrastructure and terminals had a positive impact as it focused attention on key objectives and helped force all parties to keep the system open-sourced - a key objective in our decision to go TETRA," the team adds. Existing TTC communication sites, towers and underground antenna feeders were reused for TETRA. The supplier was asked to provide a certain coverage percentage of the surface area, and could select which existing sites would be best to use. TTC prepared the sites and took responsibility for the performance of the underground RF system; the manufacturer simply supplies base stations at a defined RF power output. 

The competitive terminals contract was awarded to PowerTrunk, a Sepura company, last year and it recently supplied TTC with 600 mobile and 1,000 portable radios. 

The roll-out of the terminals is under way. The first mobile terminals are being installed in some 250-plus Paratransit (wheelchair-friendly) buses, with portables deploying in the spring of 2016 once the first software update to the control system is complete. On the existing analogue system, radio users share the same channels. With TETRA, channels become virtual talk groups and TTC can provide more talk groups/virtual channels to its users. Talk groups will be fine- tuned over the first few weeks as it becomes clearer which groups need to communicate. Several iterations of this process are expected and the reprogrammable pods in the depots will make this evolutionary process much easier. This remote programming ability was written into the specification as a key requirement. 

TTC has 700 rail cars, which usually run as six-car trains 150m long. The trains are double-ended with a radio at each end, as the trains do not turn around at the end of the line. TETRA radios are being installed into an on-board communications Unit (OCU) to interface with other train cab equipment. 

These installations will begin line by line in the summer of 2016, again with a software upgrade to the despatch system. The programme is expected to be completed by the end of the year, at which point the MPT1327 and analogue systems will be switched off. 

A new system is being developed in which TETRA will be used to transmit data from the trains' data system to the depot, using the control channel. The condition of critical systems such as brakes and motors will be monitored, and any problems quickly identified and resolved. 

In terms of security, TTC does not require the encryption used by public safety agencies such as police, but terminals are authenticated onto the system when they are switched on. TTC sees radio identity and authentication as a very useful TETRA feature. The current analogue system has occasionally been used by unauthorised users, which has caused problems. The terminal kill function is available to controllers in the event of a radio being lost or stolen. 

The emergency button on all radios was a key requirement in the specification and receives the highest priority if used. Track workers are often working during train operation times and radio communication is vital to ensure safety. "TTC is very safety-centric. In fact, if the radio system is down, the trains won't run," say Vignjevic and Thurston. 

The gateway to link TETRA with the analogue network is complete, and the legacy MPT1327 system gateway will be completed in the early spring of 2016. To operate at track level with a TETRA radio, the link to the trains is essential as MPT1327 is still being used on the trains for the next few months. Once a user has a TETRA radio, the intention is that they will not have to use any other radios, and so these gateways are essential during the transition period. Not all of the TTC operations are planned to be on TETRA at this time; for example, the bus network will remain on analogue for now [with the exception of the Paratransit buses]. 

"From a TETRA feature perspective, we did find a couple of scenarios where TETRA radios could not be configured to match our operational functional requirements. One was in how we deal with emergency calls at track level, which, in our current MPT1327 solution, any emergency call on a line will be communicated to all radios on the line only (workers, trains) as well as the line dispatcher. With TETRA, this became a challenge. As workers move between lines and the surface, the emergency destination changes and we could not achieve the desired functionality without customisation," say Vignjevic and Thurston. 

A special assignment feature has been developed as part of the contract, which links track maintenance teams with train cabs on the same line and other critical personnel as necessary to ensure the safety of the workers. Emergencies involving either the track maintenance teams or the trains are automatically patched to the other groups. This capability has been built into the TETRA infrastructure, rather than the terminals. This is important to TTC as it means that the application is not locked to any one terminal manufacturer. TTC prefers that any future applications will also be installed on the infrastructure. The mobile radios in the trains tend to have a long life and TTC is more open to using custom applications on these. 

The company has a separate Integrated Communication System (ICS) that links transit control to all emergency services and other communications media, i.e. radio, PA and TTC's internal private branch exchange (PBX) telephone system. A very large task within the TETRA project was interfacing the ICS to the TETRA infrastructure. A PBX link directly to the TETRA infrastructure is being considered, but is balanced against frequency and usage constraints. 

TTC has its own transit police, who will use TETRA, but there are no plans to link with Toronto City's emergency services agencies at the RF level. In the event of an incident requiring emergency services, the ICS controller will contact them by phone. The location and ID of the transit officers with TETRA handsets will be of significant value especially in emergency situations. One conundrum to solve is officers' preference to listen to the whole network, and then be on a private channel once an incident is in progress. This is a concern that many groups share, and will be part of the learning in development talk groups. 

Thurston tell us that "feedback has been largely positive. If there is a negative, it's that users find the radio more complex to use than the traditional TTC analogue radios. This is a fair if not unexpected point and underscores our view that new features need to be rolled out slowly to the end-user so that the features grow with the user's comfort and ability. However, users are not rejecting the new radios but actively requesting TETRA radios, saying a lot about their preference of technology. A recurring comment is that the voice quality is far superior to the older system." 

Teams that were having problems with the legacy system were the first and most enthusiastic adopters of TETRA. The system was used during the Pan Am Games, and a number of teams have been using the radios since. This dry-run testing has provided key insights. TTC has found that ease of adoption depends on how urgently the teams need an improvement in communications. 

Plans for the future 
The TETRA system will fit within TTC's ongoing station transformation programme, which will increase the automation of stations and replace ticket booths with an electronic system. Station staff will use their TETRA radios to receive calls from intercoms in the station or make PA announcements. Other information currently available to them in the ticket booth may be transmitted to their TETRA radio. In the future, single-operator trains may be enabled: a handheld radio would be provided in the cab to be used when the operator leaves the cab for any reason, for example when changing ends at the end of the line. New applications may be made available on the in-cab mobile radios, and these are expected to remain in service for many years and so special applications will be cost-effective. 

Are there any plans for using TETRA for metro signalling? "No, TTC is in the process of upgrading the signalling system (ATC), which will not be using TETRA. In the future, TETRA could be included in the existing SCADA project, perhaps to connect some units which cannot be connected to existing fibre access points," says Vignjevic. 

Will the system be expanded in the future, and are there plans to incorporate LTE or other data services into the overall communications system? "There are other projects that involve TETRA which could involve expansion, but we cannot discuss them at this time." 

Vignjevic notes that the extension of cellular and Wi-Fi coverage into underground areas will open up the possibility of broadband communications to complement TETRA. Public Wi-Fi is available to passengers in several stations at this time, and will be extended to all stations eventually. 

Currently, video is recorded on the train for use in investigation of incidents or training. If the intercom on the train is pushed, the video feed from the nearest camera on the train can be seen by the guard on their monitor. Providing a live feed of the video back to the dispatcher on a broadband link is being considered for the future. 

TTC has an ongoing project to upgrade the bus communications system and TETRA is being considered for this. TETRA is already used by bus supervisors and support staff. LTE may also be included in this programme to provide video feeds. 

TETRA is already widely used by train and metro operators in Europe and Asia; the TTC deployment is a significant step forward in the adoption of TETRA in North America. The company is clearly open to learning from early experience and adapting the TETRA system, as well as investigating broadband technologies to work alongside. It will be interesting to see how its communications evolve as the city and its transit network grow.