Quick Insight: Cloud RAN (C-RAN)

24 Oct


As all Telco engineers know that in a typical mobile deployment, each base station serves all the mobile devices within its reach. Each base station has its digital component manage its radio resources, handoff, data encryption and decryption and an RF component which transforms the digital information into analog RF. The RF elements are connected to a passive antenna that transmits the signals to the air. Each base station should be placed in the geographical center of its coverage area. But even when such locations are selected, the mobile operators may have difficulty in renting the real estate, finding proper powering options, securing the location and protecting the equipment from weather conditions. Those cell sites carry with them a continuous stream of OPEX to address the high rental rates for real estate, electrical expenses, cost of backhaul for the cell site and security measures to protect the location from intruders.

Enter the latest architectural paradigm : C RAN !!! The basic premise of Cloud RAN is to change the traditional RAN architecture so that it can take advantage of technologies like cloud computing, Software-Defined Network (SDN) approaches, and advanced remote antenna/radio head techniques.C-RAN architecture is not bound to a single RAN air interface technology. In essence, conventional terrestrial cell site base stations are replaced with remote clusters of centralized virtual base stations which can support up to a hundred remote radio / antenna units. This is achieved by centralizing RAN functionality into a shared resource pool or “cloud” (the digital unit – DU, or baseband unit – BBU) which is then connected via fibre to advanced remote radio heads (“Radio Units” – RU) sited in different geographical locations in order to provide full coverage of an area. The radical concept can even use banks of x86 servers to connect cellular calls rather than traditional wireless base stations.

From a business perspective,C-RAN will deliver significant reductions in Opex and Capex due to reduced upgrading costs. A major reason for this is the aggregation and pooling of the DU computing power which can be assigned specifically where needed e.g. the load situation over time and space for indoor/outdoor cells, am/pm hours, weekday/weekend, and so on. As a result, single cells do not need to be dimensioned for peak hour demands, but rather the processing power can be pooled and assigned on an on-demand basis. The processing power savings achieved should also leave processing headroom for any further potential technology enhancements (e.g., LTE-A features) without the need for further CAPEX. C-RAN skips the need for a high-bandwidth, low latency (X2), synchronized interface between the geographically distributed base station because the computing resources of the multiple transmission points’ BBUs are all located within the same hardware.

Furthermore, interference management will also benefit from C-RAN network architecture as technologies like dynamic eICIC schemes will be enabled, especially in a HetNet deployment.Heterogeneous networks will require small cells to be independent, intelligent and ubiquitous to avoid the cross- interference mayhem, yet be in synch and orchestrated with macro cells (including Cloud – RAN topology).Small cells are poised to become the most commonly used node for cellular access in the next-generation HetNet. C RANs will likely take their place beside traditional base stations and emerging small-cell base stations as another tool for building cellular nets.

According to Maravedis Cloud-RAN economics only be realized by harnessing standards to ensure interoperability and reduce cost. That, in turn, will create a whole new ecosystem, and operators must resist any attempts by their suppliers to hijack standards for software-defined networking or cell site equipment. Otherwise, this fledgling architecture will remain confined to a few pioneers with the resources to build their own ecosystems, like China Mobile.

China Mobile, the world’s largest carrier with 700 million subscribers, has been spearheading trials and plans to deploy systems as early as 2015. Japan’s NTT Docomo said it will follow in 2016, and a third unnamed carrier is now preparing plans for C-RANs. China Mobile aims to lower the cost of C-RANs to less than $30 per LTE sector, down from about $10,000 two years ago. It will start a second round of trials later this year using servers equipped with PCI Express cards to handle baseband processing. Each card will pack four FPGAs using silicon cores, each FPGA capable of handling 12 LTE sectors.

Pure C-RAN faces many barriers, such as over-reliance on fiber to link sites and basebands and immature standards, but most operators will inch towards C-RAN using hybrid models. Development of microwave fronthaul technologies will be critical to improve the C-RAN business model . Whatever the challenges C-RAN offers a revolutionary approach to next-generation cellular networks deployment, management and performance.

As MNOs face rising CAPEX bills to meet mobile data demand combined with falling ARPU, they must explore radical new network designs. With Cloud-RAN, they can virtualize baseband processing functions for hundreds of sites on a server or base station hotel. By consolidating individual Base-station processing into a single or regional server farm Investments on Cloud Radio Access Network (RAN) Infrastructure are expected to exceed $6 Billion by 2020, according to a new report from SNS Research. Distributed antenna technologies ( DAS ) will get a new lease on life, supporting coverage extension for C-RAN sites. This sector will open up $1.3bn in new revenues for antenna providers.

Sadiq Malik ( Telco Strategist )

Source: http://maliksadiq13.wordpress.com/2013/10/23/quick-insight-cloud-ran-c-ran/


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