This article was written after the Manchester Commonwealth Games in 2002, and it depicts how we provided over 5000 radios in a multi-trunk solution, over numerous sites, to create a secure and reliable communications system for the events. Read on and learn how we approached a job of such size, and how it's still relevant today when supplying for big events.
The Commonwealth Games Manchester 2002 Radio Solution.
- From the outset of our involvement with the Games Organisers in the Summer of 2001 it became apparent that there were many conflicting requirements for the radio systems of which some examples are given as follows:
- Field of Play officials and Technical Results staff wanted radios that were simple to operate and similar to basic walkie talkies.
- Victory Ceremony Teams, logistics and technical support required radios that would work at all and any venues and talk to any other radio user on venue.
- Road Events needed radios that would work in Manchester itself, and also on the far side of Rivington Peak in two different locations.
- The Police and Safety officials had a requirement that a missing Games radio could be switched off. This was essentially to prevent a hoax radio message (bomb threat or similar) causing a Stadium Evacuation.
- Transport needed radios that would work city wide, and communicate with staff at the venues.
- Management and other staff required radios that could call individuals as well as groups and make and receive telephone calls.
- The system had to have redundancy and reliability with the capacity to add extra channels if required at short i.e. 2-hour notice.
- System installation and commissioning had to commence at Easter with full completion by 1st June.
- The final requirement was flexibility – no one knew all that was required, or how requirements would change, but what ever it was we had to provide it.
The system proposed to meet these requirements was a 12 site MPT1327 trunked radio system at UHF. Standard trunking protocols and facilities would meet security needs, and provide private and group calls with telephone connect. Two of the sites were not interconnected, Bisley and Rivington, although the Rivington system was installed in a double decker bus which was located on Rivington Pike. The bus was needed so that the system could be easily relocated – the mountain bike events were far enough away from the road bike events, that with a large ridge in the land between the two, the radio system had to move to obtain adequate coverage of the track, but remain in contact with control at the local school in the valley. Bisley was more conventional, a single site trunk and one of our trailer masts. The 10 remaining sites in Manchester were all linked in a star network centered on Main Stadium, which had the central switch, and 6 landlines connected to the system.
To meet reliability requirements, all sites had 2-hour battery backup, and we kept a spare 6 channel trunk (on UK short term hire trunk channels) at the main logistics warehouse, together with spare base stations / cards / antenna combining etc. The idea of the spare trunk was 2-fold, if a calamity happened and we "lost a system”, the spare trunk could simply have been moved to a site and switched on. Alternatively, if we had a traffic capacity issue on any venue, this trunk would have been connected to the existing trunk at the venue, and the extra channels used.
Intersite traffic levels were difficult to predict, and we knew that once the Games started we would have no opportunity to increase network capacity so an early decision was made to utilise Fylde infrastructure with their new E1 link cards. This meant that the sites could all be linked by microwave and E1 mega stream circuits, and if we needed more than the predicted 4 inter-site channels per venue we could simply add another PCM card at the remote site for an additional 4 circuits. By utilising digital links, with digital switches, multi-site group calls also had a far lower noise floor than the conventional analogue approach. We already had great experience of Fylde equipment and its reliability and the new "softpot” computer aligned Super Trunk 3 significantly reduced our build time for each site. This was important, as we had roughly 5 days to build the system for each site, 2 days to install, and then move on to the next site. Over a 3-month period we built and commissioned a 7 to 18 channel trunked site every week! One of our more difficult installations was at Athletes Village, where the two equipment racks had to be lifted by chain hoist 60 feet into a plant room on the 20th floor of a tower block.
For good audio quality and reliability, we selected Motorola MTR2000 base stations, these gave adequate power to overcome antenna combining losses, and with the audio companding switched on in these and the corresponding Motorola GP640 and GP680 portables together with the digital switch gave a really good sounding radio system.
Antenna combining was made by Aerial Facilities, and was faultless in operation. The smaller sites (7 to 8 channels) used hybrid combining, but Main Stadium had an 18-cavity system. Despite our own 90 duplex channel pairs, 20 simplex pairs and countless broadcasters with their own transmitters and radio talkback we had no interference problems whatsoever. I’d like to think this was due to our equipment and planning and help from the Radio Communications Agency, but I think that an element of luck crept in somewhere!
User requirements for simple radio operation was achieved by using the GP640 in the talk-group select mode – to the user these appeared to operate like a conventional radio with a channel change (really a talk-group change). This simplified radio training and migration of users from conventional to trunking systems.
"Power users” had GP680 radios, with all facilities enabled.
Venue Control rooms were using various GM series trunked radios as trigger bases, together with a message handling dispatcher at Main Stadium.
Control of the system was retained by using the Fylde Syscon trunked control program to enable or disable features on a radio by radio basis. Thus, a radio user who was not originally allowed to have telephone connect (or other feature), could have it enabled at a later date with out reprogramming the radio. This was a very important requirement for our own health and sanity, as we had to program and issue some 3000 radios, all of which had different programming, and we wanted to minimise reprogramming work. The radios were all programmed to a master matrix issued by the Games. This specified the user, type of radio, pre-programmed talk groups, sites the radio was authorised for use on, and radio facilities such as telephone connect. Again, all radios were authorised in their own network fields for use on all sites, but restricted (where required) by Syscon to specific sites.
In operational terms the worst overhead that we suffered at the Games was radio reprogramming as the Games sites went fully operational at the start of July. Planned radio matrix’s can never be correct, despite test events, as users discover other radio users that they needed to contact operationally were not programmed in their radios. The GP680s were easier in this respect, as the user himself can add other groups / contacts to the dial list. Over the air Dynamic regrouping was used in some cases, but the bulk of the GP640 changes had to be made via a laptop at each venue.
Although we had a few infrastructure failures during the Games period, our customer was unaware of all but one. The sites would report an equipment or power failure back to the Syscon terminal, which if unattended, was set up to send an SMS message to our engineer’s cellphones who could then go direct to site and rectify the problem. This was usually a mains failure caused by a "helpful” hand switching off the circuit breakers!
Most trunk systems were located on venue except Portland Tower which provided wide area coverage for users travelling between sites, and of course coverage for the road events teams when they moved into Manchester for the Marathon and Triathalon. This gave a minimum effective signal level of 2uv through out Manchester, but also meant that we needed to set effective "vote now” periods and sites, with careful setting of the radios own "hunting” thresholds to ensure that where possible radios did not "hang” on the Portland Tower site, but instead stayed on the local venue channels. This also helped to reduce inter site traffic.
There were a very few users, such as the Queens Jubilee Baton Relay which did not use the trunk – for a road event travelling the UK a trunk was not considered suitable, but it did have 3 mobile repeaters and used the new Motorola GP344 for its size and weight advantages. The Baton runners were escorted by Police runners equipped with inductive loop earpieces and GP344s in covert shoulder holsters.
Finally, was the radio communications system a success? The statistics probably answer this, the 102 trunked channels handled over 1.2M calls during the Games period, with an average call duration of 42 seconds. Main Stadium with an 18-channel system only ever reached full capacity with call queuing, for 2 short periods – both lasting no more than 3 minutes, during the opening and closing ceremonies. Some sites were never to reach full capacity. In a similar fashion, we over estimated the inter-site traffic – probably 2 links from most sites would have been adequate, but in this case our customer preferred overcapacity to cuing calls.
Interestingly upon analysing the user traffic itself, the most prolific and consistent users of the system were the Security Groups, and Site Safety. All other user Groups had their usage peaks and troughs dependent upon competition.
Lessons learnt?
When assessing staff and engineering requirements, double your projections for the period when the sites go live operationally until commencement of the Games.
In the final week of the Games halve your staff projections.
Keep a great deal of extra equipment on site for those last-minute requests, it will be at least twice the quantity that you and your customer budgeted for.
