Are we going to see more of Cloud RAN (C-RAN) in future?

China Mobile was in news a few times the last month with regards to Metrocells and C-RAN. The first item from TelecomAsia:

Alcatel-Lucent has unveiled a new TD-LTE metro base station for its lightRadio product line that will be deployed by China Mobile, which co-developed it.

 

The compact lightRadio Metro Radio – revealed at this year’s Mobile World Congress in Barcelona – houses two lightRadio cubes, fully integrated with a directional antenna, with an output of 5W.

 

Alcatel-Lucent says the design allows it to “provide the coverage normally associated with a much bulkier, heavier remote radio unit linked to an external antenna via an RF coaxial cable.”

 

China Mobile will deploy the 2.6 GHz Metro Radio in its TD-LTE network in Shanghai, Nanjing and Qingdao – specifically, in busy indoor and outdoor locations like shopping centers where macro coverage can suffer either from building density or too many people trying to access the network.

 

The Metro Radio is the first product to result from a co-creation agreement signed by Alcatel-Lucent and China Mobile just over a year ago to conduct joint development and test activities on lightRadio TD-LTE projects.

An article on the same topic in Rethink-wireless throws a bit more light:

The TDD lightRadio Metro Radio houses two of ALU's now-famous 'cubes' (highly compact radios which can be installed on lamp posts) integrated with a directional antenna. This enables a level of coverage which would normally require a far larger remote radio unit linked to an external antenna via cable, claimed ALU.

China Mobile's first trial TD-LTE network using the lightRadio product covers 13 cities including Shanghai, Nanjing and Qingdao. The base station will be deployed in busy indoor and outdoor locations, such as retail malls and sports stadia. As well as C-RAN, Mobile also plans to deploy compact metrocells combining 3G, 4G and Wi-Fi on a massive scale in future.

Another one:

ASOCS Ltd., a Silicon IP provider of software defined radio solutions and CMRI, Research Institute of China Mobile (CMCC) Ltd., the world's largest mobile operator, have signed a strategic memorandum of understanding for the joint development, commercialization, testing and deployment of large-scale baseband processing units for China Mobile's next generation Cloud-RAN network.

Earlier trials undertaken by leading mobile operators, identified the bottleneck of Centralized Base-band Units, consisting of general purpose CPU, to perform major baseband calculations in cost and power efficient management. The solution was to introduce significant offloading capabilities of such calculations with highly specialized Modem Processing Units (MPU).

Today there is a growing understanding in the industry that such MPU should support a wide range of system partitioning, topologies and real time system performance, including large scale Collaborative Multi-point communications (COMP) and massive MIMO. Since communication algorithms are evolving over time, and since the C-RAN concept provisions on-the-fly reconfiguration of the BBU to support a variety of mobile communication standards, an MPU solution which is re-configurable at runtime has a great advantage over traditional hard-wired designs.

China Mobile (CMCC) has been pushing the cloud agenda for a long time. A whitepaper from them on the same topic is available here.

Picture source: NTT Docomo press release

NTT Docomo is another operator who believes very much in C-RAN. Occasionally it refers to the C-RAN as Centralized RAN. There were couple of announcements from their side:

The first one was a press release from Docomo here:

NTT DOCOMO, INC., Japan’s leading mobile operator and provider of integrated services centered on mobility, announced today it will begin developing high-capacity base stations built with advanced C-RAN architecture for DOCOMO’s coming next-generation LTE-Advanced (LTE-A) mobile system. The new architecture will enable quick, efficient deployment of base stations, especially in high-traffic areas such as train stations and large commercial facilities, for significantly improved data capacity and throughput.

Advanced C-RAN architecture, a brand new concept proposed by DOCOMO, will enable small “add-on” cells for localized coverage to cooperate with macro cells that provide wider area coverage. This will be achieved with carrier aggregation technology, one of the main LTE-Advanced technologies standardized by the Third Generation Partnership Project (3GPP). The small add-on cells will significantly increase throughput and system capacity while maintaining mobility performance provided by the macro cell.

High-capacity base stations utilizing advanced C-RAN architecture will serve as master base stations both for multiple macro cells covering broad areas and for add-on cells in smaller, high-traffic areas. The base stations will accommodate up to 48 macro and add-on cells at launch and even more later. Carrier aggregation will be supported for cells served by the same base station, enabling the flexible deployment of add-on cells. In addition, maximum downlink throughput will be extendible to 3Gbps, as specified by 3GPP standards.

Another one from Rethink-wireless here:

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.

If you are wondering what 'LTE-B' or the 'true 4G' is, see this post here.

In South Korea, both KT and SK Telecom have announced C-RAN strategies for their LTE deployments, dubbed Cloud Communications Center (CCC) and Smart Cloud Access Network (SCAN) respectively. As early as June 2011, SKT had deployed 1,772 RRHs and 609 baseband units within its LTE network in capital Seoul. The lower amount of baseband units suggests an average of almost three RRHs per baseband unit, assuming each RRH is single sector.

The above two pictures are from the Small Cells Standardization presentation here.

An old article from Rethink-wireless mentions the following:

This is the central concept of C-RAN, deconstructing the traditional base station to leave a low power unit at the cell site, integrating antenna and radio, while centralizing all the baseband activity and supporting hundreds or thousands of sites flexibly from the cloud. KT calls its LTE approach its Cloud Communications Center (CCC) architecture, and it has been co-developed with Samsung and Intel. The latter is leaping on the opportunity to bring its expertise in servers and data centers to the telco network, and in this case its platforms are integrated with Samsung modems to create a centralized exchange for signals communications processing. This is linked by fiber (essential for C-RAN) to the cell sites.

As seen in vendor strategies like ALU's lightRadio and Nokia Siemens' Liquid Radio, the CCC also harnesses virtualization technology so that the central processing resources can be allocated flexibly according to the peaks and troughs of demand in different sites. Yung Kim, senior EVP head of strategy planning at KT, told TelecomAsia: "For example, at a sports stadium you can dynamically allocate more resources for that area during a game on a millisecond basis." The design also improves coverage at the cell edge, he added, claiming twice the capacity per cell, on average, because of better improved edge management.

The CCC architecture can manage 144 base stations per server and accommodate 1,000 servers in each data center, all them acting as a central processing entity. Most tasks are run on off-the-shelf processors rather than dedicated ASICs, also a key trend to reduce the cost of data networks and to converge the norms of the IT data center with those of telecoms. The performance and power advantages of modern computer processors are now up to the task of massive telecoms networks, believe carriers like KT, hence the intense interest of Intel, although some ARM-based chip vendors like Marvell and Freescale are also pushing from the network into the data center.

Do you have an opinion on the C-RAN architectures in the future? If yes, we would like to hear.