NSN and Panasonic to take Docomo to LTE-A

Next week's Mobile World Congress will see various operators showing off their LTE-Advanced roadmaps. Carriers like NTT Docomo, SK Telecom and Telstra are always in the vanguard of new networks and for LTE-A, they will be joined by AT&T and other US players in early adoption of at least a few elements of the diffuse standard. In the run-up to the show, Japan's Docomo has selected the vendors, Nokia Siemens and Panasonic, which will upgrade its network with certain LTE-A features like carrier aggregation.

This is a good win for NSN, which has not featured as heavily as Ericsson and Alcatel-Lucent in the most advanced LTE roll-outs to date. Breaking into the Japanese carriers is tough, since Docomo in particular tends to rely on trusted local suppliers with which it has long-standing development alliances.

Panasonic, of course, falls into that category - it has worked with the operator since 2007 on LTE network infrastructure, but NSN was also brought into that project at an early stage and its efforts have borne fruit. The European vendor will supply its Liquid Radio multiple standard RAN. Like Docomo's LTE network, there will be heavy use of remote radio heads, with baseband processing virtualized in the cloud, as well as increasing roll-out of small cells to increase indoor and outdoor capacity. NSN says the base stations will deliver capacity of 300Mbps.

In future, the two vendors will support Docomo's own particular definition of Cloud-RAN, a concept which is being pioneered in China, Japan and South Korea, and which takes the idea of remote radio heads and shared basebands to a new level. Docomo says it favors C-RAN because the cell site equipment, consisting of radio and antenna, is compact and low power, and so can be deployed quickly in high traffic areas like train stations. It calls its architecture Advanced C-RAN and this will rely on some HetNet principles, including a separate layer of 'add-on' small cells adding localized capacity while cooperating with macrocells.

In the C-RAN, there will be high capacity master base stations supporting multiple macrocells plus the local small cells. The master BTSs will handle up to 48 macro and small cells at launch and more later. Carrier aggregation will be supported for cells served by the same base station. The carrier says it will boost peak downlink speed to 3Gbps over time, hitting 'true 4G' and 3GPP LTE-B standards.

One of Docomo's interests in LTE-A is to support carrier aggregation in a standardized way. Although CA is an old concept, 3GPP Releases 10 and 11 (LTE-A) provide standard ways to combine frequencies in the same or different bands, to create channels up to 100MHz wide. The Japanese cellco recently acquired 700MHz spectrum and so will have three LTE bands as well as its 3G spectrum, so its interest in CA is rising.

With its multiband situation in mind, it has also announced that it has developed its own base station antenna to support all five of its frequencies, including the newly allocated 700MHz (although that will not be freed up for commercial LTE use until 2015). The new antenna is no larger than Docomo's existing four-band antennas for 800MHz, 1.5GHz, 1.7GHz and 2GHz but the firm said adding the extra frequency was challenging because mutual interference increases as bands are added.