Several factors are driving the market for greater in-building coverage. So which technology stands to meet businesses' and operators' demands? Step forward Active DAS, says Keith Dyer
When it comes to providing coverage and capacity in-building, things used to be relatively simple for mobile operators. First off, although coverage has always been a key element, capacity demand wasn't that high. The use of mobiles was for voice only, and in fact with the price premium still evident, and limited distribution of mobile numbers as a primary contact number, the number of calls being made to and from mobiles in a business setting was relatively low.
Then came mass penetration of mobile phones, mobile and single-contact numbers on business cards, the expectancy of being able to reach anyone, anytime. Text increased as a business tool. No matter, where it was really necessary to support a business on campus, or in an area of poor coverage, additions could be made to the macro coverage. But then came 3G, which delivered a triple whammy. First, on the service side, it became vital to support the use of mobile devices, wherever they were, for email and other enterprise applications. Then, as 3G in Europe used higher frequencies, clearly penetration of steel, concrete, reinforced glass buildings was going to be an issue. Finally, the nature of W-CDMA cells, with their breathability and near-far power ratios, meant that just chucking extra cells into a plan wasn't necessarily the best answer. It was also a lot more expensive, and site permissions a lot harder to come by.
So several situations presented themselves. For smaller solutions, picocells proved a viable answer. Then there was DAS (Distributed Antenna Systems), which worked by taking a donor feed from the macro cell, or from a repeater, and then distributing that over fibre through the building. Typically, these systems consist of components such as coaxial and radiating cables, power splitters, directional couplers and indoor antennas.
And it is active DAS that is currently driving the market, according to ABi Research. ABI research says that the provision of coverage in the largest buildings will drive active DAS systems growth at a compound annual growth rate of 28% through 2013.
According to ABI, active DAS systems deliver the greatest cost benefit in very large buildings. Below 500,000 square feet, passive systems such as repeaters and passive DAS systems start to become more cost-effective. But with data services becoming a greater portion of wireless services ARPU, capacity becomes an equally relevant design factor.
ABI Research principal analyst Dan Shey, says, "Capacity is playing an increased role in the design of in-building wireless systems. As buildings get smaller, and with the presence of older passive systems, solutions will utilize a toolkit of options including repeaters, femtocells, picocells, and passive and active DAS systems. Interestingly, this solution complexity will also create a very competitive supplier environment."
In-building wireless systems will also provide the communications infrastructure to serve the needs resulting from other growing trends such as public safety coverage and environmental concerns. Says Shey, "As in-building wireless systems become more useful to building owners and enterprises, reliability, throughput, and manageability will become important design factors. This will drive product development in all related equipment and will create more managed services opportunities, ultimately growing the in-building wireless ecosystem and revenues."
Andrea Casini, Vice President, Europe, Middle East, North Africa Sales and Marketing, Andrew, says that Andrew is seeing increased demand.
"As European markets are flattening out as far as new network rollouts are concerned, operators are now seeking new ways to boost revenues. We have seen a number of operators looking towards in-building and special coverage projects as a means to do just this. In fact, this is driven by network optimisation activities by operators trying to address interference, capacity, and dead coverage spots. Improvement in high-speed data performance is also an important factor. In general, we are seeing an accelerated trend in network performance improvements.
Enterprises are certainly looking to provide wireless coverage in office buildings as growing numbers of staff demand wireless coverage wherever they happen to be within the business site, and owners of public buildings are now also beginning to realise the benefits of indoor coverage. Organisers of large events now demand seamless wireless coverage, and with technology having developed to deal with much higher capacity than a few years ago, wireless vendors now need to optimise their services to provide a multi-operator, peak capacity service, with minimal visual impact, and at a competitive price in order to stay ahead of the game."
John Spindler, VP Product Management, ADC, says that increased data usage and applications are driving that demand, spurred on by increased 3G coverage.
"There's more data usage, 3G systems are now rolling out everywhere, and the higher frequencies of those systems attenuate more quickly. Just as users need better coverage and capacity, the frequencies bringing them these new services need more help with in-building systems. In addition, in-building systems help mitigate the problem of cell phones "hunting" between multiple macro towers in dense urban areas by providing a stronger signal from inside the building," Spindler says.
Andrew's Casini says, "There is no doubt that data usage has increased over recent years. Businesses now demand instant access to a range of communication methods including e-mail, instant messaging, and voice and video over IP, all of which require a high-speed broadband connection to work efficiently. It is no longer acceptable for large service providers to provide an unreliable connection, especially as the market becomes more crowded. In dense urban areas the competition for wireless coverage is amplified significantly, which is why operators need to consider deployment of advanced in-building solutions."
So what solutions does Casini see as providing the answer?
"Complex buildings such as large office blocks, airports and shopping malls require dedicated coverage and capacity. The subscriber profile will dictate adequate traffic resources, most normally with micro and pico base stations complemented by passive and/or active DAS. At times, and particularly so in suburban areas, backhaul could be a limiting factor.
"Typical network planning is bi-dimensional, hence normally missing out the third dimension of vertical buildings. This factor often skews the visibility of potential high-traffic (and revenue) pockets, that are simply neglected or overlooked. As a consequence, networks may face huge traffic crowding and blocking, with lost calls and poor accessibility.
A correct assessment of those potential risks is a key factor to accelerate positive customer experience and revenue growth in today's competitive ecosystem. Andrew provides appropriate tools to accurately measure network quality and lost traffic, and flexible wireless coverage solutions to efficiently address those issues."
ADC's Spindler says it is about finding the right mix of solutions. "Operators have used DAS and remote radio heads for years to mitigate the problem. Extending macro coverage is very expensive and time-consuming compared with deploying DAS or small radio heads to provide spot coverage in areas where macro coverage is poor. Pico cells are relatively new, but they make it possible for carriers to expand capacity inside a structure in a very cost-effective way when they are deployed in conjunction with a DAS. Previously, carriers would either deploy a small base station at a site or use roof-mounted antennas to grab signal from the macro space and relay it to amplifiers (BDAs) and DAS inside the building. Pico cells are far less expensive and easier to deploy, and they can use standard TDM or DSL connection for backhaul, which also saves the operator money."
Andrew's Casini highlights the economic, as well as technical efficiency, of building shared systems in dense environments. "Our solutions are adopted in a number of dense urban areas, e.g., in Canary Wharf and in Glasgow's West End, both in order to overcome the limiting factors of wireless propagation in confined environments – i.e., typical coverage extension – and/or to optimise the distribution of network capacity by providing an additional street-level wireless layer (typically low-power, low-impact antennas invisibly installed on light poles) that offloads urban traffic from the macro network in areas of high density of subscribers.
"Those solutions become extremely attractive from both an economical and a technical point of view because of their intrinsic ability to provide a shared infrastructure that can be efficiently used by multiple wireless operators and services. While the cost-sharing factor is obvious, it is also worth noting that the technical advantages of a shared solution with reliably consistent radio performance contribute to reduce interferences and maximise capacity and efficiency, particularly so in WCDMA technology. A robust O&M system allows independent access to status information by each participant to the system, including third parties in charge of the system itself."
Active and Passive DAS
A DAS can serve one or several operators and one/or several bands (e.g. GSM 900, GSM 1800 and WCDMA). In some cases the DAS can be used to concurrently distribute both cellular and non-cellular bands, e.g. both GSM and WLAN in one and the same antenna system. The most commonly deployed DASs are the passive coaxial cable solutions. These consist typically of a micro or a macro base station that is connected to a number of distributed antennas via coaxial cables and combining equipment such as power splitters, power tappers, combiners, multi casting matrixes etc. The DAS can support one or several mobile operators and one or several mobile technologies (GSM, WCDMA, CDMA2000, TETRA etc). But the DAS can consist of either passive or active components. When both active and passive components are used in a DAS, it is often referred to as a hybrid solution.
Some advantages of a dedicated RBS connected to a DAS, are that it is possible to ensure both dedicated coverage and capacity, confine the signals, prevent spillage and interference and thus enhance the quality for both speech and data services. In addition for enabling new traffic in previous non-covered areas, the solution also off-loads the macro network in overlapping coverage areas. The RBSs are normally owned by mobile operators.
Some of the biggest advantages of an active DAS, compared with passive coaxial DASs, are the much longer distribution distances as well as the smoothness and ease with which one may install the optical fibres. The initial cost of the system as well as the operation and maintenance costs are commonly higher than for a passive solution.
Single-operator DASs are typically owned by the mobile operator, while multi- operator DASs tend to be owned by other players in the market, such as neutral host providers, building owners, government authorities and enterprises