SK Telecom to deploy Elastic Cell by 2016 July 25 2014

Working with Ericsson, Korean operator builds improved performance into CoMP technology to enhance cell edge experience

By Caroline Gabriel

Scarcely a week goes by without a vendor, operator or start-up proposing a new architecture for the mobile network. Sometimes these are part of the growing attempts to influence what '5G' will look like, but many are generic changes which could be applied to current networks and then might ease the transition to a future platform. Small and even-smaller cells, in multiple layers or meshes, and going right down to ad hoc personal cells formed for as long as an individual needs them; virtualized RANs with distributed radios; new approaches to distributed antennas, to update the venerable DAS.

The wave of creativity indicates how fervently operators are looking for ways to harness a wide range of spectrum sources, and eke maximum capacity and flexibility out of those frequencies, in their desperate bid to keep up with data demands while reducing galloping capex and opex costs. But there is also an equally urgent need to improve overall user experience, in terms of capacity and coverage, but also in terms of personalized services - certain quality levels, data speeds and optimized applications automatically delivered by a network aware of each customer's location and preferences, for instance.

That is leading to a change of emphasis in new network designs, from cell-centric to user-centric, as SK Telecom of Korea, often the first to try a new idea, puts it. SK is referring to 'Elastic Cell' a technology which it recently demonstrated with Ericsson, and which it calls a "key enabler for 5G". How anyone can know that, when 5G is not yet defined, is uncertain, but what does ring true is that many inventions which are developed now, and pioneered in current networks, will then feed into the next generation. 5G, Ericsson radio chief Ulf Ewaldsson, and many others, believe must be on a continuum with LTE, harnessing and intensifying trends like smaller cells rather than starting with a clean slate.

This means that many areas of current R&D will remain relevant in the next decade too, if they can be proven to work well and cost-effectively. Elastic Cell is one of many technologies which aims to end the difference in QoS at the cell edge, and to deliver uniform service wherever a user is located. LTE-Advanced features such as CoMP (Coordinated Multipoint) have the same end in view.

SK Telecom says that Elastic Cell (also called Flexible Cell) can boost cell edge data rates by 50%, and it will deploy the system commercially by 2016. It enables multiple cells near the handset to cooperate for every transmission, rather than confining a device to a single cell. A serving base station receives information on nearby cells from the handset and selects a group of cells that can improve the network quality at the edge for transmission, while temporarily turning off other nearby cells that would cause interference.

This approach is not brand new, but builds on CoMP, which also allows multiple cells to work together through joint scheduling and transmission, to improve performance at the edge. SK Telecom has operated CoMP in its LTE-A network since 2012 on the downlink and since April on the uplink. Elastic Cell is seen as a step forward from CoMP, improving the base standard's scheduling, energy efficiency and cost efficiency. Other similar projects include China Mobile's Amorphous Cell.

The trials will feed into the recently announced partnership between SK Telecom and Ericsson to research 5G technologies, and in turn into the European Union's alliance with Korea's R&D agencies for the same purpose.