24 July 2012
Will mobile operators be amongst the winners at the London Olympics?
Are you one of the lucky few with Olympics tickets? Well, you may need to come out on top in another lottery, should you wish to share your experience with friends via your smartphone or iPad.
The reason? There are mixed signals emerging about whether coverage at the Olympic Park – with all its venues and expected throng of visitors – will be up to speed. The problems are likely to be most extreme at peak times and key moments, when everyone will be trying to send photos, access data, tweet and attempt video streaming – not to mention making calls.
All the mobile network operators contacted were adamant the intense planning, extra investments (estimated at more than £30 million) in antennae and basestation gear and thorough testing they have carried out means there will be no lack of coverage over the whole site.
To help planning and execution, the operators formed the Joint Operator Olympic Group (JOOG) to coordinate their efforts. The group includes: BT, which will be providing much of the IT infrastructure as well as wireless networking capabilities; Ofcom, the UK's communications and spectrum regulator; LOCOG, the organising committee; and Airwave, which has developed and installed a TETRA based Private Mobile Network operating at 385MHz dubbed Apollo. This will be used exclusively by the organisers running the events at all sites, as well as by the emergency services.
The target was to share as much infrastructure as feasible, which is important as the area around the Olympic Park did not have much in the way of cellular coverage, having long been largely an underdeveloped site.
The word 'legacy' has been bandied around since London won the bid, and Dave Fraley, a radio design manager at O2 seconded to JOOG, told New Electronics 'this partnership model amongst normally keen competitors could be a great legacy for mobile network operators'. However, he also cautions that no decisions have yet been taken of how much of the infrastructure installed will be used after the games, nor how much of the overlay gear and antennas would be redeployed.
Fraley also said that while, from a technology point of view, the whole ethos has been to use tried and trusted equipment and known designs, 'we have actually come up with some real innovations in ensuring there will be sufficient capacity to meet the most extreme demand'.
The spectrum planning was coordinated by Ofcom. It estimates, for example, that 350 wireless microphones will be needed, 75 HD video streams (three of them airborne) and 800 talkback channels. To meet demand, Ofcom has borrowed spectrum from the likes of the Ministry of Defence and will use frequencies freed up following the switchover to digital tv. More contentiously, it has allocated the 2.6GHz spectrum range – earmarked for the UK's so called 4G, or Long Term Evolution mobile broadband service – for the use of wireless cameras during the events.
Auctioning off the 2.6GHz spectrum, which is also mired in a major stand off between the network operators and regulators, is now expected later this year, later than in most other European countries.
One of the toughest challenges for Ofcom has been to ensure there is no interference from rogue transmitters at the Olympics venues, particularly those at the Park. It has worked for years to specify a system to manage access and installed a huge sensor network to police and identify any interference problems. This has been a boon to many unidentified test and measurement equipment suppliers.
The regulator plans to double its team of 'expert engineers' for real time monitoring of all transmitters during the games. It expects a major strain on the wireless infrastructure around the Park with so many frequencies being deployed at the same time.
"There will be a huge demand for wireless cameras, for instance, but these technologies are well understood and we are confident that the regime we have put in place will cope efficiently with the demand," said Peter Bury, director of spectrum policy at Ofcom. Bury added that even though the regulator is not responsible for the mobile network operators' preparations and performance, "from what we have seen, their plans to share infrastructure, including antennas, basestations and backhaul will cope fine."
One of the most important of these plans has been a project running for the past two years under the auspices of the JOOG and including radio engineers from across the UK mobile network sector. This project has designed and implemented the radio (physical) layer required to deal with all contingencies at the Olympic Park.
While the Olympic arena was being constructed, the group used London's 82,000 capacity Twickenham stadium as a 'test bed' for trialling and testing what Fraley suggested was the key to providing an order of magnitude increase in capacity over the existing system. "We soon decided we needed to dramatically improve the sectorisation of cells at traffic hotspots within the Park."
A cell/sector is the physical area over which the antennae of mobile basestations provide coverage on a specific channel. In a typical 3G network, all channels may be reused in every sector, provided there is sufficient isolation between sectors to prevent interference.
"The Twickenham tests indicated we would need a ten fold increase on the four sectors serving that stadium to achieve the anticipated demand at the Olympics. From a radio point of view, this was hugely challenging and the key enabler proved to be a specialised antenna system devised specially for stadia, but not previously deployed in the way we have and not on such a major scale."
Acquired from Australian antenna specialist Argus, the large flat panel array has exceptionally sharp roll off in the gain profile and a 50 x 50° beam width, allowing good sized sectors. Importantly, the antennae – of which 40 have been installed throughout the stadium – also feature low sidelobes (unwanted extraneous radiation), so the result is very highly focused signals targeting very small sections of the seating. "This means we can deploy many more of these side by side with not too much overlap, reducing interference from other cells significantly, including from the smaller, conventional, low power in-building antennae we needed to use for in fill coverage in the bowl area," said Fraley.
Dealing with limited space
Numerous macrocells have also been deployed throughout the Park, which also proved to be a 'challenging planning exercise to ensure these do not interfere with each other or the networks surrounding the Park'.
Another tricky problem was that the space within the venues is quite limited and the operators needed a lot of basestation equipment to feed all these antennae. "We got round this by devising a so called Basestation Hotel situated in the Park. From there, we feed the antennae in the venue sites using conventional radio over fibre gear that links into BT's total fibre network. As far as possible, we have followed the principles of resilience and used techniques such as diverse routing to minimise the possibility of interference or losing service."
Operators used their traditional switch suppliers within basestations; for instance, 02 deployed gear from Nokia Siemens Networks and Vodafone its normal gear from Ericsson.
"I would say we have faced and overcome numerous challenges in design an implementation, and we believe have done successfully," O2's Fraley told New Electronics.
"All the necessary infrastructure has been installed and tested and we can say capacity will not be an issue, the radio over fibre links are up and running to ease the expected huge demand at peak times and we believe we have identified and catered for all contingencies with the necessary spare gear and backups," he added.
Measurements taken during test events indicate voice success rates are pretty well 100% throughput and, perhaps more importantly, the data experience was hitting 99.9% accessibility and very high throughput.
Asked whether the group has managed to stress test the infrastructure at really peak demand, for instance very soon after the 100 metres men's final, or the opening ceremony, Fraley conceded this has not been possible. "Of course, you never really know how something like this will perform at such a time, but with all the planning that has gone into this, with all our previous experience, with all the trials, we are pretty confident about the resilience of the mobile network."
In retrospect, perhaps the most positive legacy the Olympics may provide is the push, by Wi-Fi network operators such as BT and the mobile network operators, to deploy free wireless networking – not just at the event sites, but also throughout most of London. Access points have been installed in the most unlikely places, hugely increasing the whole mobile coverage and easing congestion for the cellular networks.
BT, for instance, has promised there will be 50,000 hotspots throughout London by the time of the opening ceremony. Within the Olympic Park, the operator is funding a huge Wi-Fi overlay network, with optional wholesale access for other operators.
In preparation for the Olympics, O2 acquired rights to use many street assets, for example lampposts in several London boroughs, and has deployed more than 100 Wi-Fi access points, using gear from Ruckus Wireless. The network went live late last month and the company said that, as well as giving it important sites in key locations, it hopes to use these when deploying other small cells for increasing 3G and LTE coverage.
Londoners may also have noticed Wi-Fi availability at large Underground stations, the result of a monopoly contract won last year by Virgin Media against tough competition. The plan is to connect 82 mainly central stations by the end of July, with a further 30 stations due to get platform only level internet access by the end of the year. The service will be free during the Olympics and then available free only to Virgin Media customers.
Let's leave the last handover to Mike Short, vice president for public affairs at 02 and current president of the IET, who told New Electronics: "London 2012 has given the UK's mobile industry a huge opportunity to show off its radio engineering capabilities to the full and we have certainly stepped up to the challenge. The readiness of the network operators to fully collaborate in such a complex project also bodes well for the future."
The basestation hotel concept
A basestation hotel is the key component of a specific cellular architecture in which basestations belonging to multiple operators and offering multiple technologies (such as 2G, 3G and TETRA) are located at a central facility for ease of installation, integration, commissioning and maintenance.
The basestations are connected to a network of rf repeater units over a greater geographical area, such as a large building, campus or metropolitan area.
The wideband repeaters support all operators and require a much smaller footprint than individual operator basestations. They are connected over an optical fibre network and provide the rf drive power to numerous distributed antennas within each location.
From Olympic Park's point of view, the basestation hotel concept has been essential due to high security and therefore limited operational access during the games.
Remote Radio Units, which convert the fibre analogue feeds into rf modulated signals, are connected to a distributed antenna system in the venue to deliver rf coverage and capacity to the target areas.