Turning radio networks inside out
Fibre distributed antenna systems (DAS) for in-building wireless coverage are taking off as operators turn networks inside out. Ian Brown, of Axell Wireless, explains
The rapid uptake of smartphone technology has undoubtedly led to a huge increase in mobile data usage. With EE spearheading the launch of LTE in the UK, this trend is only set to continue.
With around 80 per cent of mobile data usage now occurring within buildings, the UK regulator, Ofcom, recently stipulated that in-building LTE coverage must be made available to 98 per cent of the UK population by the beginning of 2017.
This demand has, in turn, stimulated the in-building wireless market. Indeed, a recent report from ABI Research has revealed that the global market for in-building wireless equipment is on course to exceed $2 billion by 2013.
In the UK, the in-building wireless market is witnessing increasingly high levels of investment from operators and the wider telecoms industry. The realization that the vast majority of mobile data usage is emanating from within buildings – from office blocks and shopping centres, from airport terminals and sports stadia – has gone a long way towards prompting this increased investment. It has led to a situation in which many operators are now building their networks from the ‘inside out’ rather than the ‘outside in’, which represents a substantial change in mind-set from a few years ago.
However, it should be noted that this increased investment is not solely the result of an LTE ‘gold rush.’ While Ofcom is releasing the 800 MHz and 2600 MHz bands to provide operators with a much-needed increase in spectrum to help support newly introduced LTE services, in-building coverage systems will still need to support multiple frequency bands, including existing 2G and 3G services. In addition, operators are seeking to re-farm 2G and 3G frequency bands such as 900 and 1800 MHz, to free more spectrum for high-speed LTE services. Therefore, it is critical that the in-building system allows 2G, 3G and 4G services to coexist within the same frequency band.
Fibre, a flexible solution
Today, many buildings are constructed from materials that reflect radio frequency (RF) signals, and the only way to ensure seamless coverage for users is to install an in-building coverage system. Furthermore, the extensive range of data applications now running on smartphones requires good signal levels to work effectively.
Femtocell or picocell solutions can be used in small-scale deployments such as home offices, but these solutions offer only limited levels of connectivity. For larger structures, a fibre distributed antenna (DAS) solution should be deployed, providing in-building coverage for multiple frequency bands and technologies while facilitating the management of additional capacity in times of high usage.
The key component of a fibre DAS solution is the optical master unit (OMU). This can support RF frequency bands from FM, VHF, UHF and multiple cellular bands up to and including 2·6 GHz. Wireless signals are fed into the OMU from a base station or base stations, which may be situated in the vicinity of the structure or connected via a fibre link from as far as several kilometres away. Another option is to use a digital off-air repeater to pick up signals off-air from outside the building and feed them into the OMU.
The OMU itself converts the RF carriers into modulated light for distribution over an in-building fibre network to a series of optical remote units located throughout the structure. At these remote units, the optical transmission is converted back into RF signals for propagation within the building via directly connected antennas – mounted on ceilings, for example. The OMU and optical remotes cover all major frequency bands and support all wireless technologies, allowing the system to support multiple operators and services.
Operators can therefore work together in a shared infrastructure to bring whatever coverage and technologies they want within a building. Fibre DAS systems support a combination of high- and low-power remotes in a single system, providing flexibility within an office block. For example, a large central mezzanine may be served by a high-power remote, while in adjacent offices and smaller rooms, lower-power remotes can be deployed, propagating coverage.
The ability to mix and match various remotes enables operators and building owners to install tailored DAS systems that can meet the exact requirements of individual structures. Supporting both cellular and public safety remotes from one optical master unit, fibre DAS systems can eliminate the cost of deploying multiple DAS solutions in larger structures where – for example – the emergency services may require radio communications in addition to the cellular operators.
The future’s bright
With the industry placing an ever-increasing onus on the importance of delivering cellular coverage in-building, it is imperative that operators consider the most cost-effective and efficient way of supporting mobile data usage within buildings. The flexibility and economic viability of fibre DAS technology is revolutionizing the field of in-building wireless coverage. Fibre DAS now represents the fastest growing sector of the in-building wireless market and ABI Research estimates that revenue from active DAS systems will soon exceed $1 billion, representing some 50 per cent of in-building spending.
Fibre DAS systems provide a long-term solution for the propagation of signals and the provision of capacity in medium and large structures. Operators can now deploy technology that gives them the flexibility to deal effectively with a wide range of installation and spectrum challenges.
With Ofcom’s recent stipulations, a huge investment in ‘in-building’ wireless technology is required on behalf of the operators. The ability to deploy a single, adaptable solution within complex structures that would have previously required multiple installations, is of huge financial and operational benefit to the operators.
Mobile data is undoubtedly moving indoors and fibre DAS solutions now offer operators a robust, flexible and cost effective way of solving that challenge.
How fibre RF triumphed at the Games
For the 2012 Olympic and Paralympic Games, Axell Wireless worked closely with the UK’s leading mobile operators to deliver seamless mobile phone service across the entire Olympic Park and its associated venues. “Visitors to the Olympics experienced continuous mobile connectivity for the duration of the events”, said Ian Brown, of Axell Wireless. “A wireless network of a level of sophistication never seen before was deployed across the Olympic venues, setting the benchmark for future events of this size and importance.”
Faced with this challenge, the network operators adopted a fibre distributed antenna system (fibre DAS) supplied by Axell. Multiple base stations installed in a single location – a ‘base station hotel’ – were directly connected into the Axell fibre DAS system to propagate cellular coverage throughout the park.
Fibre DAS systems from Axell were also deployed across many other Olympic venues throughout the UK and in total over 300 of Axell’s MBF family of optical remotes were installed, 46 of them in the main Olympic Stadium alone. Mobile operator EE led the project to provide coverage around the 80 000-seat stadium, and Axell Wireless worked with EE to ensure that the fibre DAS system was configured support all the major frequencies used by the UK’s mobile operators.“The London Olympics was an unprecedented event, and warranted an in-building wireless deployment of equal measure”, commented Richard Caul, responsible for network and service operations at EE. “Visitors to the games received a seamless mobile experience, which contributed to the success of the Olympics. The UK mobile operators demonstrated their capability to support one of the most challenging events ever likely to be staged anywhere in the world.”
Axell Wireless also provided on-site and remote monitoring support during the games. “From our network operations centre, based just outside of London, we rarely got the chance to watch the athletics, as our time was spent watching the performance of the network”, said Ian Brown. “Our objective from the outset was to remain unnoticed in the background. We achieved a reliable and consistent level of coverage throughout the duration of the games, and were able to remain fully behind the scenes as we had planned.”