As data usage on mobile networks continues to grow, small cells will have an increasingly important role to play in supporting mainstream network providers, and boosting signal in areas where coverage is weak.
Already, there are large parts of the UK where consumers and businesses struggle to get good 3G coverage, due to base stations being too far apart or because the topography prevents radio signals from reaching particular areas. These areas are commonly known as “not-spots”.
With 4G technology expected to arrive in the UK on a wide scale in 2014, the data demand on mobile networks will become even greater, as use of bandwidth-hungry applications such as media streaming and video calls increases, as well as new applications like machine-to-machine (M2M).
The unprecedented growth of mobile data traffic means that data demand is outstripping network capacity. As a result, Juniper Research predicts that small cell and WiFi systems will carry nearly 60 percent of all mobile traffic over the next five years.
Small cells – such as femtocells, picocells, and microcells – are miniature base stations that provide a low-power signal in confined areas, such as indoor environments and remote outdoor locations, resulting in better voice quality, higher data performance and better battery life.
Ofcom has indicated that small cells will have to be incorporated into the 4G Long Term Evolution (LTE) network infrastructure if mobile operators are to cope with the massive surge in demand for data.
By offloading mobile data traffic onto available complementary networks, operators can optimise the available network resources and reduce the bottlenecking of services. But are small cells advanced enough to deal with the LTE onslaught?
LTE small cells come in many form factors; as well as femto, pico and microcells, there are also small cells optimised for indoor or outdoor use, those that support Time Division Duplex (TDD) and Frequency Division Duplex (FDD) variations of LTE, and those that operate at specific frequencies.
Jayanta Dey, vice president and head of R&D and consultancy for telecoms at Wipro Technologies, said that the versatility of LTE small cells is an advantage, because it means they can be used in a wide range of situations, but also creates challenges from a product engineering point of view.
One way to resolve this issue is to use a scalable software architecture for various deployment configurations. Wipro offers its own software architecture that can be easily ported to the different types of small cells.
“You need a common software that will run across the various hardware configurations, whether it is femto, pico, micro, metro, indoor or outdoor,” he said.
Dey said that, small cells is both a growth market and highly competitive. In order to succeed, therefore, it is essential to have the right price-performance ratio.
“That can only happen if you have a very tight integration between the software, the hardware, and the the mechanical design,” he said. “It is not just about the software, it is how you do a tight integration across the various components for optimum system performance.”
As small cells evolve, an important development will be the integration of multiple technology support within the same box, according to Dey.
“You don't want separate boxes – one box supporting LTE small cells, one supporting 3G small cells and a third for WiFi. You want one integrated box which supports all this technology,” he said.
Interference management is also an important area of R&D, because the amount of cellular coverage area subject to inter-cell interference grows from 25 percent with macro cells to 40 percent with macro and small cells. To prevent interference, the macro and small cells need to be coordinated, said Dey.
Finally, usability needs to be improved, in order to enable self-installation and allow organisations and individuals to actively monitor these devices. This should lead to more widespread integration of small cells into the 4G network.
Wipro is also developing a lightweight packet core for public safety, defence, large enterprises and rural markets. The company said these use cases require a small footprint and ruggedised systems that support multiple mobile broadband technologies.
“In a situation where commandos need to enter a public building, like a hotel or a hospital, and they are involved in some sort of combat with a terrorist group for example, they need to be able to set up a network to communicate with the central team,” said Dey.
“The central team could be using a base station in a jeep that is right outside the building, and the commandos have these units which are transporting video images to the central unit so that it aids in making better decisions. We are seeing this type of usage for public safety.”
An enterprise example could be an oil drilling company needing to set up a small LTE network to communicate with employees in remote locations and send large packets such as videos.
“For these type of enterprises that operate in remote areas but have some critical operations, small networks may become very important,” said Dey.
At this year's Mobile World Congress, carrier and vendor executives warned that standardisation of small cells is still a work in progress. There may be hidden costs, they warned, and carriers may end up fighting over spots to set them up.
Even though the cells cost much less than macro equipment, each still needs to be installed and have a fast backhaul connection, which is usually wired. Small cells mean more cells in a given area, so more wires and bandwidth charges for the mobile carrier.
“Even though the cells cost much less than macro equipment, each still needs to be installed and have a fast backhaul connection, which is usually wired,” said Ovum analyst Daryl Schoolar. “Small cells mean more cells in a given area, so more wires and bandwidth charges for the mobile carrier.”
Small cells may be the key to enabling the mobile networks of the future, providing an underlay to support the world's macro networks. However, there is still a lot of work to be done before their full potential can be realised.