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In the mobile handset world, there has long been a drive towards smaller more powerful devices. And even though the rise of the smartphone has seen a return to larger screen sizes, today’s handsets are still remarkably compact.
Now it seems that as we move towards a data driven, bandwidth hungry 4G or LTE world, small is finally becoming beautiful for the mobile networks as well – beautiful not only in terms of coverage and capacity, but also in terms of cost.
It is a fact that nothing boosts network capacity like spectrum re-use; and capacity gains are more effectively achieved by the use of small cells than by any other technology. So for next generation high-speed mobile data networks to deliver the throughput and penetration required in congested city centers, operators will be looking to deploy a tight pattern of potentially overlapping small cells within the overlay macro network.
This approach has been christened the het-net – short for “heterogeneous network.” Up until relatively recently, the economics of building a cellular network involved getting the right locations to throw large-scale radio footprints across wide areas to create the coverage needed to stimulate demand. However, with the world trade body – the GSM Association – predicting as many as 50 billion connected devices by 2020, demand stimulation is no longer the main concern in network planning and design: satisfying the current and predicted demand for mobile data is now the driving force.
The vision of the “het-net” is the technical solution to the demand equation. A large-footprint macro network containing a pattern of “ever-decreasing circles” giving additional targeted capacity. These circles will drill down through urban and metro layers to individual offices, shops, homes and high traffic areas such as railway stations, airports and sports venues.
In the Unites States, AT&T Mobility has already experienced the benefits of targeting coverage at individual locations with its 3G MicroCell – the world’s largest roll-out of a consumer small cell solution.
The lessons we have learned from helping to roll out AT&T Mobility’s nationwide consumer femtocell deployment, and also from working with more than 60 mobile operators on public small cell deployments worldwide, are proving to be crucial to the het-net vision and also to the economic arguments.
LTE networks, for example, are envisioned as self-organising but the rollout of high capacity city center LTE networks with a dense pattern of small-cells in a het-net configuration will present a new and complex series of challenges that engineers will need to address in order to successfully deliver the coverage and capacity benefits.
The good news is that private small cell deployments in consumer homes already depend on self-optimisation techniques built into each unit, enabling them to listen to and adjust to their surrounding radio environments. These capabilities will be a vital attribute in future mobile network design – in a network with a large number of small cells, RF tuning of individual cell sites must be as automated as possible.
In addition, we know that each small cell deployment is different. That sometimes seemingly unconnected changes have unforeseen impact on performance – a new software upgrade for a popular smartphone, for example, might affect the radio performance characteristics of the network and require some manual intervention. Automated optimisation built into small cells works very effectively most of the time, but network planners will need to be able to gather detailed information from the small cell layer, analyze it and react quickly across the network to maintain the standards that consumers will demand and expect.
Network engineers will have to master and utilise self-organizing network technologies alongside other intervention and network orchestration techniques including remote diagnostics and spectrum management in order to be able to fine tune and improve performance.
But amid all these requirements to learn new techniques and adjust to new challenges, there is also good news for the operator community as it cements its plans for the 4G world. The small-cell led roll-out of LTE networks will have a major impact on network investment costs – and in a good way.
Indeed, the small cell, het-net, approach to network roll-out will change forever the way that wireless networks are built and – despite the resultant surge in the number of deployed cell sites – the investment cost of network construction can actually become lower and more manageable.
The rise and success of the consumer femtocell has helped drive down manufacturing costs of these targeted coverage and capacity solutions – but it doesn’t end there; because they can use all-IP transit to connect back to the core network, the supporting infrastructure costs for these cells is also much lower. What’s more, small cells can be deployed with pinpoint accuracy to exactly match network demand resulting in a much faster return on network infrastructure investment.
What all this means is that as the base cost of a cell site falls to hundreds of dollars rather than tens of thousands of dollars, the savviest network operators will be able to quickly react to network demands, adding additional capacity to match their roll-out much closer to their returns.
The core technology of the consumer femtocell – originally conceived as a home market solution to black-spots in mobile network coverage – now finds itself in great demand as network operators face up to the challenge of building the advanced networks required to deliver levels of capacity that were beyond the wildest dreams of the most optimistic analyst even just a few short years ago.
Building and managing those networks will mean taking the lessons of large-scale consumer femtocell deployments into the heart of network management planning and design. After all – within a year after launch, there were already more private small cells on the AT&T Mobility network than had been built in some 30 years across all the U.S. mobile networks combined – that’s how fast the small cell revolution is taking hold.
