C-RAN (Cloud-RAN) , sometimes referred to as Centralized-RAN , is the proposed architecture for future mobile networks. It was first introduced by the China Mobile Research Institute in April 2010 in Beijing, China, 9 years after it was disclosed in a patent application filed by a US company. In short, C-RAN is a centralized cloud computing architecture for radio access networks that supports 2G, 3G, 4G and future wireless communications standards. Its name comes from four 'C in the main characteristics of the C-RAN system, "Clean, Centralized processing, Collaborative radio, and Cloud Cloud real-time Access Network".
Video C-RAN
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Traditional cellular, or Radio Access Network (RAN), consists of many stand-alone base stations (BTS). Each BTS covers a small area, while the BTS group provides coverage over a continuous area. Each BTS processes and sends its own signal to and from the mobile terminal, and passes the charge of data to and from the cellular terminal and out to the core network via the backhaul. Each BTS has its own cooling, reverse transport, backup battery, monitoring system, and so on. Because of limited spectrum resources, network operators 'reuse' frequencies between different base stations, which can cause interference between neighboring cells.
There are some limitations in traditional mobile architecture. First, every BTS is expensive to build and operate. Moore's Law helps reduce the size and power of the electrical system, but BTS support facilities are also not increasing. Second, when more BTSs are added to the system to increase their capacity, interference between BTSs is heavier because BTSs are closer to each other and more of them use the same frequency. Thirdly, as the user moves, the traffic of each BTS fluctuates (called a 'tide effect'), and as a result, the average utilization rate of individual BTS is quite low. However, these processing resources can not be shared with other base stations. Therefore, all BTSs are designed to handle maximum traffic, not average traffic, resulting in a waste of processing resources and power at idle time.
Maps C-RAN
Evolution of Base Station Architecture
All-in-One Macro Base Station
In 1G and 2G cellular networks, base stations have an all-in-one architecture. Analog, digital, and power functions are accommodated in a single cabinet the size of a refrigerator. Usually base station cabinets are placed in a special room along with all necessary support facilities such as power, backup battery, air conditioning, environmental monitoring, and backhaul transmission equipment. RF signals are generated by the base station's RF unit and spread through the RF cable pairs to the antenna on top of the base station tower or other mounting point. This all-in-one architecture is mostly found in macro cell deployment.
Distributed Base Station
For 3G, distributed base station architecture was introduced by Ericsson, Nokia, Huawei, and other leading telecom equipment vendors. In this architecture the radio function unit, also known as the remote radio head (RRH), is separated from the digital function unit, or baseband unit (BBU) by the fiber. Digital baseband signals are carried over fiber, using the Open Base Station Architecture Initiative (OBSAI) or the common Common Public Radio Interface (CPRI). RRH can be mounted at the top of the tower close to the antenna, reducing losses compared to traditional base stations where RF signals must travel through the cable length of the base station cabinet to the antenna at the top of the tower. Fiber connections between RRH and BBU also allow for more flexibility in network planning and deployment as they can be placed a few hundred meters or several kilometers away. Most modern base stations now use this separated architecture.
C-RAN/Cloud-RAN
C-RAN can be seen as the evolution of the distributed base station system architecture above. It takes advantage of many technological advances in wireless, optical and IT communications systems. For example, it uses the latest CPRI standard, low-cost or Dense Wavelength Division Multiplexing (CWDM/DWDM) technology, and mmWave to enable the transmission of baseband signals over long distances to achieve centralized central station deployment on a large scale. This applies Data Center Network technology recently to enable low cost networks, high reliability, low latency and high bandwidth interconnection in BBU pools. It leverages open platform and real-time virtualization technology rooted in cloud computing to achieve dynamic shared resource allocation and multi-vendor support, multi-technology environment.
Architecture Overview
The C-RAN architecture has the following characteristics that are different from other mobile architectures:
- Large-scale centralized deployment: Allow hundreds of thousands of RRH to connect to a centralized BBU pool. The maximum distance can be up to 20 km in fiber connection for 4G (LTE/LTE-A) systems, even longer distances (40 km ~ 80 km) for 3G (WCDMA/TD-SCDMA) and 2G (GSM/CDMA) systems. There are reports that some Asian operators have the deployment of a C-RAN system with 1200 RRH centralized to a central office.
- Genuine support for Collaborative Radio technology: Each BBU can talk with other BBUs in a pool of BBU with very high bandwidth (10Gbit/sec and above) and low latency (level 10us). This is made possible by the BBU interconnection in the pool. This is one major difference from BBU Hotelling, or hotelling base station; in the latter case, the BBU from different base stations is simply stacked together and has no direct relationship between them to allow coordination of the physical layer.
- Real-time virtualization capabilities based on open platforms: This differs from traditional base stations built on proprietary hardware, where software and hardware are closed sources and are provided by a single vendor. The C-RAN Pool BBU is built on open hardware, such as an x86/ARM CPU-based server, plus an interface card for handling fiber links to RRH and inter-connection in the pool. Real-time virtualization ensures resources in the pool can be dynamically allocated to the base station software pile, for example 4G/3G/2G function modules from different vendors according to network load. However, to meet the strict timing requirements of wireless communication systems, real-time performance for C-RAN is at a 10-second microsecond rate, which is twice the height of the 'real-time' level of millisecond performance typically seen in Cloud Computing environments.
Similar Architectures and Systems
Korean Telecom introduced the Cloud Computing Center (CCC) system on 3G (WCDMA/HSPA) and 4G (LTE/LTE-A) networks in 2011 and 2012. The CCC concept is basically the same as C-RAN.
SK Telecom has also deployed Smart Cloud Access Network (SCAN) and Advanced-SCAN on 4G (LTE/LTE-A) networks in Korea by 2012.
In 2014 Airvana (now CommScope) introduced OneCell, a small C-RAN-based cell system designed for companies and public spaces.
Competing Architectures in Cellular Network Evolution
All-in-one BTS
One of the main alternative solutions that address similar RAN challenges, is the small size, all-in-one outdoor BTS. Thanks to the achievements of the semiconductor industry, now all BTS functions, including RF, baseband processing, MAC processing, and packet level processing can be implemented in volume & lt; 50 liters. Making small and weatherproof systems also reduces the difficulty of location selection and BTS construction, eliminating air conditioning requirements and thereby reducing operational costs.
However, since each base station is still working on its own, it can not easily utilize a collaboration algorithm to reduce interference between adjacent BTSs. It is also relatively difficult to upgrade or improve because the all-in-one BTS unit is usually installed near the antenna. More processing units in less protected environments also imply higher failure rates compared to C-RANs, which only have RRUs used outdoors.
The Cloud RAN advantage lies in its ability to deploy LTE-Advanced features such as Coordinated MultiPoint (CoMP) with very low latency among multiple radio heads. However, the economic benefits of improvements such as CoMP can be negated by higher backhaul costs for some operators.
Small Cell
The main competition between small cell and C-RAN occurs in two deployment scenarios: outdoor hotspot coverage and indoor coverage.
Players and Activities
China Mobile began to promote the idea of ​​C-RAN publicly in April 2010. It is also very active in various international standards organizations on R & D in C-RAN.
According to public information, the following companies have signed a MoU on C-RAN collaboration with CMRI on April 23, 2010: ZTE, IBM, Huawei, Intel.
At the recent 4th International Mobile Internet Conference on December 13 and 14, 2010, six additional companies joined: Orange, Chuanhua Telecom, Alcatel-Lucent, Datang Mobile, Ericsson, Nokia Siemens Networks.
In October 2011, the 40th ITU Telecom Exhibition in Geneva, Switzerland, China Mobile showcased four distinct sets of C-RAN Evidence Systems developed with partners including IBM, Huawei, ZTE, Beijing's Orange Labs, Beijing University of Posts and Telecommunications. Over-the-air 2G/3G/4G communications with commercial terminals and test terminals have been demonstrated. Two of the four systems are based on an open platform and two of them are based on a proprietary platform.
NGMN formed a working group called P-CRAN in April 2011 to learn the requirements, solution suggestions and C-RAN standardization. NGMN has issued D3 Suggestions on Potential Solutions for Contribution Contribution CRAN and D4 to 3GPP ETSI on Radio Collaboration MIMO ORI Interface as the output of this project.
Green Touch has received a preliminary proposal of key C-RAN technology research in June 2012.
Mr. Bill Huang, the GM China Mobile Research Institute was invited to give a speech at the World Mobile Congress in February 2012
In Linely's recent conference [Linley Tech Carrier Conference 2012] pm 5 and 6 June 2012, ASOCS announced the Silicon IP product, CR2100, accelerating Intel x86-based processing. ASOCS & amp; China Mobile signed a Memorandum of Understanding on February 25, 2013, announcing a joint development program to create a viable commercial solution for Cloud RAN.
Since October 2012, the C-RAN has been widely discussed in the 7th Base Station Conference in London, England. Operators, vendors, and analysts have provided various views on C-RAN in the overall evolution of RAN.
While the x86 platform is considered by many to be the prevailing platform. The ARM-based platform may be available during 2017 and beyond. A hint in that direction can be seen in the joint Press release created by ARM and ASOCS at ARMTeCon 2013.
Relationship to Virtualization Network Functions
The Networking Virtualization function treats C-RAN as one of its applications. Topics defined in test case # 6. ASOCS recently announced the development of a full virtual base station as part of this test case. C-RAN can also enable cell virtualization, a technique for virtualization of wireless spectrum resources.
Academic Research and Publications
As one of the promising evolution paths for future mobile network architecture, C-RAN has attracted high academic research interest. Meanwhile, due to the native support of the cooperative radio capabilities built into the C-RAN architecture, it also enables many advanced algorithms that are difficult to implement on mobile networks, including Multi-Point Cooperative Transmission/Receipts, Network Coding, etc.
In October 2011, 27 Wireless World Research Forum was held in Germany, when China Mobile was invited to give C-RAN presentation.
In August 2012, the IEEE C-RAN 2012 workshop was held in Kunming, China.
CRC Press published a book, "Green Communications: Theorical Fundamentalsals, Algorithms and Applications", and has the 11th chapter: "C-RAN: A Green RAN Framework".
In December 2012, the IEEE GlobalCom 2012 conference, the International Workshop on Cloud-Based and Large-scale Cooperative Communication Station, was held in California, USA.
The European Committee Frame Project 7 has sponsorship and currently handles many issues related to the evolution of cellular network architecture. Many of these projects have used C-RAN as one of the future mobile network architectures, such as the Mobile Cloud Network project.
References
External links
- The official C-RAN website at China Mobile Research Institute
- the first C-RAN international workshop website, in Chinese
- ASOCS Confirms that C-RAN is a Superior Implementation
- ASOCS & amp; ARM announced the cloud-ran reference design
- asocs and Windriver (INTC) popularize Virtual Base Stations
- CommScope Definition: What is C-RAN?
- Virtualization Cells with C-RAN Small Cell
Source of the article : Wikipedia
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