SK Telecom boosts upload rates with Uplink CoMP roll-out April 08 2014

By Caroline Gabriel, Research Director, Maravedis-Rethink

Innovative cellcos and their suppliers are increasingly competing to be first to support key elements of LTE-Advanced. While commercial deployments labelled LTE-A are almost always, in fact, confined to the carrier aggregation elements of the extensive standards menu, operators are starting to explore the potential of other items such as CoMP, advanced MIMO and others.

Korea’s SK Telecom is often claiming the laurels in these contests, and increasingly, its key partner is Nokia NSN. Their latest joint achievement is the first commercial deployment of Uplink CoMP (Coordinated Multipoint), 18 months after Huawei claimed the first trial of the technology.

The Korean carrier plans to apply this enhancement to all its LTE base stations in the course of this year, boosting data upload speeds by 20% at the edge of the cell. Devices can be upgraded via an over-the-air software update. Huawei, in its 2012 trial, said upload rates could be doubled for a single user at the edge – an indication of the gap between trials and real world usage.

CoMP is a critical element in improving the efficiency, performance and cost effectiveness of macro base stations, helping operators to enhance quality of experience, especially at the cell edge. In many cases, carriers are looking to CoMP to prolong the life of their LTE macro sites, perhaps postponing investment in other performance improvements such as small cells. CoMP has been cited as a motivation for operators to roll out elements of distributed or Cloud RANs, since it works by combining signals from several nearby base stations.

Uplink CoMP enables signals coming from devices to be received by more than one base station, and then combined to increase signal strength. SK Telecom said the technology would be increasingly important to the user experience as photo and video uploads became common practice.

Other important SK/NSN collaborations in the past year have included early deployments of a virtualized evolved packet core, and of the vendor’s Liquid Apps technology for delivering applications from the base station. But CoMP is a particularly critical element of 3GPP Release 11, though one unlikely to be adopted in the mainstream until late 2015 and beyond, according to Maravedis-Rethink’s RAN service forecasts, because of its great complexity.

The technology makes it possible to coordinate the optimization of transmission and reception from multiple distribution points (cells or remote radios), and also enable joint transmission and/or reception to mobile devices. This will reduce interference, improve cell-edge performance, lower power consumption and increase capacity. Indeed, CoMP will be the most important enabler of complex HetNets and is a primary motivation for operators to take an interest in Cloud-RAN.

Because of its complexity, CoMP has been split into separate downlink and uplink standards, though both use the same overall schemes – joint processing (transmission or reception) and coordinated scheduling/beamforming. Both these are being tested and, in SKT’s case, implemented, but in the very early stages. There are two major approaches to CoMP – to prolong the life of conventional homogeneous macro networks by increasing capacity and efficiency, thus enabling an operator to delay investment in small cells and new HetNet architectures; or conversely, to support and justify a HetNet and/or Cloud-RAN project. The 3GPP has two homogeneous and two HetNet use cases and over the next couple of years, we will see these start to have a significant influence on the network plans of the major carriers.