The 9,000 or so buses that make up the London Buses fleet rely for their in-cab communications on a private MPT 1327 analogue trunked professional mobile radio (PMR) network.
The network is made up of 10 base stations provided by Tait Communications deployed around the London. The network provides 76 VHF radio channels, of which 10 are used for control channels. However, with increased demand the network is experiencing severe call handling issues.
‘We need to upgrade our private radio system primarily because of the capacity issues,’ says Dr Dimitris Kaltakis, Radio Services Manager at London Buses. ‘We have exhausted the current system’s resources.’
London Buses, part of Transport for London (TfL), has managed to repurpose and flex the original system and the current radio system assets. ‘We even did some frequency re-use at Hornchurch and Faggs Road near Heathrow Airport in November 2015,’ recalls Kaltakis, ‘this successfully increased capacity, but the extra space created was immediately taken up. We are running at an excess of 65,000 calls per day now going through the system, which was originally designed for some 32-35,000.’
The organisation has also carried out some consultancy work to look at the radio usage patterns to analyse why drivers are making so many calls and whether they were making unnecessary or overly long calls which might be clogging up the available resources.
‘The research revealed that drivers were not using it for purposes other than what they needed to - mostly route control issues caused by diversions and to keep headway between buses to maintain appropriate intervals,’ says Kaltakis. ‘So, the vast majority of them were not wasteful calls; they genuinely needed to use the radio.
‘We had issued guidelines for radio usage especially for busy times to the effect that service controllers should try and be brief with their calls,’ he continues. ‘In fact, the average call duration did actually drop as a result. The routes were busier so they needed to make more calls, but they are actually efficiently issuing messages, mostly 24 to 25 seconds per call during busy times, so they are what I would refer to as proper radio calls.’
He adds that London Buses has looked at the possibility of acquiring additional frequencies to augment the current system, so long as that did not require it to do upgrade work on the network. Ministry of Defence (MoD) spectrum was one possibility, but Kaltakis says the MoD is not going to release appropriate spectrum any time soon.
London Buses did consider frequencies that Ofcom indicated were available, but the problem is it would need to change the bus antennas in order to utilise these. ‘That’s a big cost,’ says Kaltakis. ‘You need two people and it takes a long time to disconnect the antennas as the wiring is all sealed in. It is possible that this will have to be done at some point, but it probably won’t happen until the iBus system is replaced around 2020-22.’
The iBus system
The iBus system provided by Trapeze (formerly Siemens) provides real-time location data to track where the buses are and is used to measure bus operator performance. It leverages a variety of technologies including satellite (GPS), gyroscopes, accelerometers, odometers and mapping systems to pinpoint the buses’ location in almost real time.
GPRS (2G) is used to send the location data every 30 seconds to control rooms, garages and is also used to feed the Countdown bus arrival system at bus stops and mobile devices.
The Trapeze contract is still very much fit for purpose and was renewed in 2015 for five years with the option for two further one-year extensions - hence the 2020-22 date for the renewal of the system. ‘That is when changes to the bus on-board-units will happen,’ says Kaltakis.
The original Siemens contract provided the entire operating system including the radio, but the latter part is going to have to be separated out and replaced much earlier. ‘One reason we have to go for radio upgrade now is that we cannot wait until 2020-22 to migrate to another possible solution, as our call usage is forecast to increase still further in the years to come.’
London Buses has been keeping a close eye on what is happening with the UK’s new Emergency Services Network (ESN), which will see fire, police and ambulance moving onto mobile network operator EE’s 4G LTE network beginning in September 2017. London Underground is due to be tied into the ESN coverage umbrella, which is why London Buses has been looking to see if it might join in to provide a united TfL communications network.
However, this is not going to happen at this stage, partly because of the pressing need to upgrade the London Buses radio communication system and also because of the time needed to align all TfL radio networks,. ‘In any case,’ says Kaltakis, ‘running a critical communications service on a public commercial mobile network is not that appealing, today.
‘What would be the cost of that for us to be a Tier 1 customer? This is unknown,’ he points out. ’How much would data, including voice packets, cost us? So, all these considerations explain why we need to move to upgrade our radio network now, go digital first but with an eye to a potential LTE service in future years. We’ll see how ESN plays out for the public safety users and wait for the dust to settle on the first LTE services.’
He adds that in any case, having a private radio network for operational critical voice, which is cheap to run on its own resources is something that cannot be replicated for London Buses at this stage. A Digital Mobile Network (DMR) Tier III trunked two-way radio system makes the most sense at this juncture, says Kaltakis.
‘By moving to DMR we will utilise the existing frequencies we already own. We can reuse base stations sites and antennas and by moving to digital we get double the number channels. It also saves on training as the users are familiar with trunked radio systems, although they might need a bit on dealing with digital voice.
‘By using DMR our investment in our existing assets is retained and we will be using the same kind of form factor, so installation will be easy. We can just swap out the radios, although the interfaces will need to fit with the existing Automatic Vehicle Locator (AVL) system of course,’ says Kaltakis.
He adds that while some work needs to be done with the new radio supplier in order to interface the new system with the existing AVL and other systems, it shouldn’t be a big challenge. ‘As regards the addressing scheme, there will need to be talks between the AVL supplier and the new radio supplier,’ he says.
So, what will the new DMR radio contract look like? This is still under discussion, and will form part of a future procurement, but Kaltakis reveals that it might be let to more than one supplier. ‘We want to promote competition between suppliers, but maybe not for the core network as that probably needs to be one supplier. But for the in-vehicle mobile radios we may have more than one supplier. We are very much in favour of open standards, so that should be achievable with DMR.’
One option being looked at is to let the contract in phases. For example, the first Lot to go to tender might be for the core network plus some radios and then maybe more lots for the approximately 9,000 vehicles that need fitting out. However, Kaltakis emphasises that this is not decided yet.
What will the transition look like as the DMR system is rolled out? ‘It’s a 24-hour system so buses will be coming out of service for the upgrade over quite a long period, so unless a supplier comes up with some amazing solution both the old analogue and the new digital systems will have to work concurrently,’ points out Kaltakis.
‘However, most new digital systems support both analogue and digital and maybe we can use gateways for interoperability. But it is up to the suppliers to come up with the solution; we don’t want to over specify. Sure, we have our own ideas about how to do it, but we want to get industry’s ideas too.’
Kaltakis says that London Buses will undertake an on-frequency migration from analogue to digital, which needs to be managed in such a way that neither the analogue or digital systems gets congested in the process.
‘We want the extra capacity to be there in the digital system,’ he says. ‘I have an idea of the critical number of buses that need to go first, but we want to see supplier proposals as industry may have good ideas,’ he reiterates.
Hand portable radios
Kaltakis says London Buses has carried out consultancy research on the need for hand portable radio use. ‘We got consultants to issue some questionnaires to bus station controllers and bus operator staff from the bus franchisees like Arriva, Go Ahead, Tower Transit and others, as to what the appetite was to have hand portable radios.’
He confesses he was surprised to find out that there appears to be a genuine need to use hand portables despite the fact that the current system was not explicitly designed for their use – the power output of the network is geared to the higher output Wattage of mobile radios, rather than the less powerful hand portables.
‘The majority of people asked said they would consider using hand portables for group calls, PTP communications and monitoring control room updates. It is not a huge number of people, but there is a genuine need for it. However, it doesn’t justify specifying a hand portable network, but I could see a place for a specialised device that sits on the network with a push-to-talk function that might use cellular or Wi-Fi, for example, with a bridge back to the core network..
‘We could use a commercial bearer for device to gateway and onto the DMR network, or to talk directly to the buses. Or, you could even use the DMR base station directly if you are near enough. In the future, we anticipate that the buses will have a multi-bearer gateway/router on board anyway,’ says Kaltakis.
London Buses has not made a decision on whether the hand portable solution will be part of the main contract or something that might be added later. One advantage of having such a solution is that it could also be offered to staff on the DLR network, Croydon Tramlink, or anyone within TfL who might use a hand portable.
As Kaltakis points out, it is really just a device cost. Wi-Fi networks are already installed at garages and the core radio infrastructure will be the same one provided for the buses, so additional costs will be low.
The tender process is not yet fully established. Funding has been allocated for the new DMR radio system and for the AVL upgrade, and the internal approval process is almost completed, according to Kaltakis.
However, the proposal still needs to gain formal TfL funding approval. Kaltakis hopes it will be presented to the board in late summer. If the go-ahead is given at that time, then London Buses aims to commence procurement in September/October – if everything else goes to plan.
‘We plan to have an Industry open day for suppliers, so they can see the interfaces and check out the buses and the functionality, which we expect to be the same as the MPT 1327 system plus all the additional features that a DMR system can offer. That way suppliers can get an idea of what will appear in the Invitation to Tender (ITT),’ reveals Kaltakis.
He adds that London Buses wants the new radio system to be as future proof as possible. ‘That means we want standard interfaces like Ethernet, Wi-Fi and Bluetooth without having to specify proprietary interfaces.
‘In the future, there will be a vehicle hub supporting all the different onboard systems and with the capability to decide what has priority over what and what needs to communicate with what. That might all happen wirelessly, which would be good,’ says Kaltakis.
There are very few examples of DMR Tier III trunking systems implemented for transportation systems yet, certainly not on the massive scale of the London Bus system. So, the London Buses contract will be a both a great opportunity for DMR manufacturers, as well as a considerable showcase for what the young DMR Tier III digital trunking standard can deliver.