C-RAN (Centralized Radio Access Network)

C-RAN is a centralized, cloud computing-based architecture for radio access networks that supports 2G, 3G, 4G and future wireless communication standards.

Traditional cellular, or Radio Access Networks (RAN), consist of many stand-alone base stations (BTS). Each BTS covers a small area, whereas a group BTS provides coverage over a continuous area. Each BTS processes and transmits its own signal to and from the mobile terminal, and forwards the data payload to and from the mobile terminal and out to the core network via the backhaul. Each BTS has its own cooling, back haul transportation, backup battery, monitoring system, and so on. Because of limited spectral resources, network operators 'reuse' the frequency among different base stations, which can cause interference between neighboring cells.

There are several limitations in the traditional cellular architecture:

Each BTS is costly to build and operate.

Moore's law helps reduce the size and power of an electrical system, but the supporting facilities of the BTS are not improved quite as well.

2.When more BTS are added to a system to improve its capacity, interference among BTS is more severe as BTS are closer to each other and more of them are using the same frequency.

3.Because users are mobile, the traffic of each BTS fluctuates (called 'tide effect'), and as a result, the average utilization rate of individual BTS is pretty low. However, these processing resources cannot be shared with other BTS.

Therefore, all BTS are designed to handle the maximum traffic, not average traffic, resulting in a waste of processing resources and power at idle times.

C-RAN may be viewed as an architectural evolution of the distributed base station system. It takes advantage of many technological advances in wireless, optical and IT communications systems. For example, it uses the latest CPRI standard, low cost DWDM technology, and mWave to allow transmission of baseband signal over long distance thus achieving large scale centralized base station deployment.

It applies recent Data Centre Network technology to allow a low cost, high reliability, low latency and high bandwidth interconnect network in the BBU pool.

It utilizes open platforms and real-time virtualization technology rooted in cloud computing to achieve dynamic shared resource allocation and support multi-vendor, multi-technology environments.

C-RAN architecture has the following characteristics that are distinct from other cellular architectures:

1. Large scale centralized deployment: Allows many RRHs to connect to a centralized BBU pool. The maximum distance can be 20 km in fiber link for 4G (LTE/LTE-A) systems, and even longer distances (40 km~80 km) for 3G (WCDMA/TD-SCDMA) and 2G (GSM/CDMA) systems.

2. Any BBU can talk with any other BBU within the BBU pool with very high bandwidth (10Gbit/s and above) and low latency (10us level).

TELEKOM MALAYSIA (TM) has deployed C-RAN solution using DWDM.

The design as below:

WDM_OTN