Inside out?

01 April 2011 |


With continual technological advances in femtocells and small cells, Angela Partington asks whether femtocells will move out of the home into enterprise, public and rural arenas. And as they do, what impact will their introduction have on network planning?

Femtocell and small cell technology has largely focussed upon the immediate benefits which they can bring to the consumer by extending service coverage indoors. Accordingly, the adoption of femtocells in our homes has been steadily gaining ground; a factor doubtless driven by a number of major telcos making the technology readily – and in some cases, freely – available to targeted customers suffering from connection problems. As Mike McRoberts, director of IP and in-building solutions at Sprint, explains: “Where the coverage from the macro network does not effectively give end users what they need in the home, we provide femtocells as our solution in order to give them the coverage they’re looking for.”

There has certainly been a marked growth in their availability. In February 2011, there were 21 commercial services in operation, with a further 34 companies making deployment commitments. At the end of 2010, the Femto Forum estimated that, in the US alone, there were 350,000 femtocells, as opposed to 250,000 macrocell sites. During this year, the worldwide number of femtocells is expected to exceed that of macrocells. While this certainly doesn’t mean that they are to be found in every home, the shape of our mobile network has changed radically.

Yet interestingly, while they are happy to sing the praises of femtocells, many service providers making the femtocells commercially available are reticent to disclose exactly how many units are in the public domain. This may be in a pragmatic attempt to limit the number of free femtocells requested by the public, focussing the benefit onto those with particularly heavy data requirements. Or there may be a latent anxiety that the benefit intrinsically suggests a need for remedial activity which implies weaknesses in the macro network.

A more targeted approach

Not surprisingly, the Femto Forum is a strident advocate of the technology. Research it conducted last year across six countries upon the factors which influenced consumers in rating the services of their operator most highly, showed that consistent service coverage came number one. And the same research showed that the largest motivating factor in the decision to have a femtocell was also consistent coverage.

One of the key defining features of the technology is that it allows coverage to be provided in a targeted way from within the building. Indoor coverage can easily be problematic. Stelios Savvides, mobile access manager at Vodafone Qatar, stresses the particular architectural challenges faced in his region – the thick walls and heat-reflective glass which can have such a negative effect on signal strength and result in significant attenuation of mobile coverage. But this problem isn’t confined to particular geographies or buildings. Guaranteeing a high-quality signal indoors, whether in residential properties, shopping malls, train stations or offices, can present a universal challenge. As Yannick Dupuch, director of GM of the small cell product unit at Alcatel-Lucent, says: “If you take a macrocell network, you will see that between two macrocells you sometimes have deep holes of coverage, and all buildings located there – whether the home, the enterprise or public buildings – suffer from poor indoor signals. The first application of femtocell technology is to boost coverage at a lower cost.”

Carriers are definitely beginning to broaden their horizons when it comes to the application of femtocell technology. As McRoberts says: “At the moment, femtocells are generally limited to 5,000 ft2. But as the technology improves, I think that you’ll see femtocells move into larger and larger building areas, and there’s a real chance that they can become the predominant way to cover buildings.”
But while the majority of telcos still focus their use in residential properties, a few are adopting some truly innovative applications. Network Norway has just completed a year-long test of femtocells in enterprises and is now introducing the technology commercially (see box below); while Sprint is also working on solutions for the enterprise environment. Softbank in Japan is using a satellite backhaul femtocell to provide coverage in remote and rural areas; extensive field trials in 2010 have shown it to reach the voice quality and stability of a traditional base station. Most significantly, Softbank claims that it takes just a few days to deploy a femtocell as opposed to a year for traditional methods, while implementation costs are eight times lower. Other telcos, including Vodafone Qatar, are also planning to engage in outdoor trials of femtocells over the next 12 to 18 months.

Simon Saunders, chairman of the Femto Forum, agrees that telcos are taking a more diverse approach: “Whereas last year all the deployments were residential, now about a third of them are specifically targeting enterprises, and we’ve got a small sprinkling of cases where femtocells are being deployed for public usage in shopping centres, convention centres and retail premises. It’s definitely diversifying.” The larger power and larger capacity of some femtocells, particularly those for use in the enterprise environments, means that they are now able to carry 16, 32 or even 64 simultaneous voices with a range that will span a couple of kilometres. “These will be more like the deployment model of microcells,” says Saunders. “They are all building on the underlying femto technology; whether you choose to call them femtocells, picocells or microcells, they’re based on the standards and ecosystem developed originally for residential femtocells.”

Another major development is the growing emphasis being placed on data coverage. Initially, the benefits of femtocells were largely seen in voice, but increasing numbers of operators are providing femtocells as a 3G solution. “As far as data capacity is concerned,” says Saunders, “a residential femtocell provides all the data capacity of a 3G carrier, which is effectively the same data capacity as you’d get on a whole sector of a macrocell.”

An emergency response?

One of the real difficulties for carriers lies in forecasting data requirements accurately enough to cater for demand which is growing rapidly and unpredictably. “Exactly how fast mobile broadband usage is growing in any particular area is basically unknown and unknowable,” says Saunders. “The planning cycle for a macrocell upgrade is at least 12 months, but you can put in a femtocell overnight.” Instead of spending significant amounts of capex on a macrocell deployment, femtocells allow carriers to apply a laser focus to the problem and put the right size and shape of small cell into the exact location where it’s needed.”

It is also becoming increasingly expensive and difficult to find locations to construct new macro cells, making it a challenge for suppliers to tackle capacity issues using cell towers alone. “One view of femtocells is that they are just a sort of band aid for macrocells, mending particular places at particular times,” says Saunders. But many suppliers now regard small cells as a way to enhance and refine their network intrinsically. “Most people believe that with existing macro-style technology, you won’t be able to achieve the data capacity that you need in enough density to meet the growing demand,” says Lyndon Campbell-Black, manager of offer and product strategy at Ubiquisys. “The natural corollary of that is to produce more small cells, closer together.”

The expense and complexity of planning and constructing macrocell sites is not lost on anyone, and of course regional complexities only add to the difficulties. Savvides complains that, although 85% of the Qatari population lives in the capital Doha, neither Vodafone Qatar nor the incumbent QTel has received a permit to build a new cell site for over a year. “We have had to resort to deployments of temporary cell sites – cells on wheels. The femto is a quick and economic solution, but it doesn’t avoid our long-term strategy which is to get a much better network and ensure that indoor coverage is available everywhere.”

Integration with the macro

With the femtocell playing an increasing role in providing a targeted and evolving network, managing the integration of the femto and macro technologies is vital. Gordon Mansfield, executive director for radio access network delivery at AT&T says: “You can’t consider your femto network totally in isolation from the macro; it is absolutely integrated into it as another layer.” McRoberts refers to the femtocell as: “an in-building version of our macro network. We’re not claiming that femtocells are a silver bullet, but they’re one of the tools in our tool bag to give customers the coverage they’re looking for.”

Femtocells can certainly enable users to achieve substantially higher data rates than can be obtained purely with a macro network. By transferring high-data traffic off the macro network where possible and releasing pressure on the network, femtocell deployments can provide significant increases in capacity, perhaps by multiples of as much as 10 or 100, leaving high mobility traffic to hop up to the macro cell layer. Dupuch refers to the drastic improvements in the exchange of information between femtocells, allowing a mobile call to move directly from one femto to another, without needing to jump to the macrocell during transit.

With a proliferation of smaller cells, this requires greater sophistication in terms of management and control. There is increasing reliance on smart technology, with small cells ‘self-organising’ to extract the most capacity from the integrated platforms. As Campbell-Black puts it: “This management could be quite an additional burden if the cells weren’t reasonably smart; if they didn’t have the intelligence to do their own radio frequency tuning; if they didn’t have the ability to look at the radio environment and decide what power level they should be operating at, to provide the best coverage with minimum interference to the macro radio environment.” With much of this configuration taking place automatically, workloads for both the end user and the carrier are reduced.

Financial opportunities

The femtocell is a low cost device, which costs very little to manage; backhaul and radio network expenditure is near zero because it exists on a broadband network. Analysis by the Femto Forum shows that the overall lifetime value of a non-atypical residential setting is increasing by a factor of two or three to the operator. “There’s a very sharp increase in capability,” explains Saunders, “and a reduction in the cost of delivery. If it costs perhaps $8 to $10 to deliver a gigabyte of traffic on a macro network today, it probably costs only a dollar or two to deliver the same traffic over a femtocell. And as femtocells are managed intelligently to offload the traffic fully, that cost drops to only a few cents per megabyte.” Where carriers still have spare capacity on the wide area networks, there is little incentive to invest in another technological layer; but as traffic increases, this will provide an avenue for exploration.

Other opportunities exist in the potential for additional services. Ubiquisys believes that the market might not be ready for these yet, but NTT DoCoMo is doing interesting work in Japan with an alert service that emails or texts parents when their children get home from school. The Femto Forum has recently announced standards for advanced mobile applications based on femto technology, designed to enable developers to promote a broader usage of the technology. Aditya Kaul, practice director, mobile networks at ABI Research, explained some other possible uses: “The basic functionality of the femtocell is that it picks up your presence when you walk in. You could sync your mobile phone with your home media system; you could control lights and security cameras while you’re away from home; you can use your phone to remotely access content on your PC.” Perhaps of more significance is the prospect of LTE femtocells. In October 2010, the Femto Forum published a set of application programming interfaces for femtocell devices. China Telecom has been particularly aggressive in its call for the development of this technology, according to Saunders: “China Telecom threw down the gauntlet to vendors and said we will deploy these in large numbers but we need them soon. If you can provide them, we’ll use them.” The market is definitely watching this area with interest.

When reviewing the future of femtocells in our network, a common theme to emerge is the huge amount of capacity which is wasted just in penetrating the outside walls of buildings. To add to this concern, most in the industry believe that the proportion of traffic consumed indoors is likely to rise significantly over the next few years. With our networks being placed under increasing strain by growth in data usage, femtocell technology offers service coverage an easier route into our homes.