Indoor Radio Performance – Addressing the next operator challenge

The importance of adding small cells to complement the macro network is growing in importance, especially indoors, as the networks need to get denser to reuse the scarce spectrum and improve channel quality.

When do you think about your mobile broadband connection? As long as you can grab your smartphone to instantly connect with your friends on Facebook, enjoy your favorite Netflix TV-show on your tablet, upload and browse your Instagram photos or challenge your colleagues in a game of Ruzzle-you typically never do.

When we do think about our mobile broadband it is when that important call is suddenly dropped, the video stalls, or we get frustrated at being unable to do what we like with our mobile devices – anywhere and anytime, instantly and seamlessly – at home, shopping in the galleria, taking the subway to work or killing time waiting in line at the supermarket or train station. We care about application coverage – being able to use our applications whenever and wherever we want, not being restricted by being located in a “bad spot”.

Accelerated consumer expectations drive the need to improve coverage in the networks. As applications and services become more demanding, the need to provide high data rates and sufficient capacity increases. This can be achieved by improving and densifying the outdoor macro network where local conditions allow. However, the importance of adding small cells to complement the macro network is growing in importance, especially indoors, as the networks need to get denser to reuse the scarce spectrum and improve channel quality.

If you happened to visit the Ericsson Integrated Small Cells area at the Mobile World Congress (MWC) 2014, you might have seen our Indoor Performance Demonstrator. Through visualization of radio network simulations, we explored what application coverage is achieved in an urban city area covered by an outdoor LTE 20 MHz macro network, as traffic steadily increases.

With increased traffic demand, the importance of having good indoor coverage increases. We demonstrated that if this problem is not properly addressed, high concentrations of users in a large building, such as an office or mall, that is poorly covered by the outdoor macro network, will ruin the performance not only for the users in that particular building, but also for outdoor users connected to the same cell.

Hence, poor indoor coverage not only affects indoor users, it also affects outdoor users. Indoor users, with a weak received-signal, attenuated by walls, will consume more radio resources, leaving fewer resources for outdoor users to transmit on, despite a stronger received-signal.

By deploying indoor systems, where there are high concentrations of users and poor outdoor-in coverage, we showed that by offloading less than 10 percent of the most demanding users from the macro with indoor systems, the overall number of users in the network capable of watching HD video streaming increased from 30 to 60 percent. Adding indoor systems resulted in excellent data rates and coverage indoors, which is intuitive, but it also frees up resources in the macro cells, improving performance also for users connected to the outdoor macro cells.

Putting indoor systems in any house, without considering the surrounding network and user density, can give rather limited effects on the overall network, although the indoor coverage in the particular building still is excellent.

If we look around us, it is quite clear that most buildings are very different – footprint, height, wall materials and the amount of people inside a particular building can greatly vary. It is quite natural to expect a mall or an indoor stadium to be more crowded than a residential building or warehouse. So, in this same way, there is no one-solution-fits-all when it comes to heterogeneous networks and indoor deployments.

It might be efficient to traditionally cover smaller residential buildings from the outside-in with powerful outdoor macro basestations, while medium to large buildings, such as office buildings and malls, can efficiently be served by indoor solutions like the Radio Dot System (RDS)-which received a lot of attention from operators during MWC.

New, innovative solutions like the LAN CAT 5/6/7 cable fed Radio Dot System, creates completely new ways to provide cost effective indoor coverage and capacity in a wide range of buildings. At the same time, this makes it feasible to evolve the network to meet the growing traffic demands of the future. For example, we showed how to evolve a Radio Dot System in a 24-floor office building by splitting the radio cells, adding capacity capable of handling the estimated 2020 enterprise traffic.

At Ericsson Research we are working to find the best possible solutions for the heterogeneous networks of the future, where the typical consumer never has to think about their mobile broadband. They are simply connected – anywhere and anytime, seamlessly, wherever they are.

Håkan Andersson, Ericsson Research

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