Cloud-Based Networking: Cloud Radio Access Networks
Cloud Radio Access Networks (Cloud-RAN) is a new type of wireless access network architecture based on the trend of current network conditions and technological progress. As a type of clean system, C-RAN is based on the Centralized Processing, Collaborative Radio, and Real-time Cloud Infrastructure. Its essence is to cut down the number of base station and reduce the energy consumption, adopt the collaboration and virtualization technology to realize the resources sharing and dynamic scheduling, improve the spectrum efficiency, and achieve low cost, high bandwidth, and flexible operation. C-RAN’s overall goal is to address the various challenges brought by the rapid development of mobile networks, such as energy consumption, construction and operation and maintenance costs, and spectrum resources., pursuing a sustainable business and profit growth in the future [2].
As shown in Fig. 2.4, C-RAN architecture mainly consists of the following three components:
- Distributed network consisting of a Remote Radio Unit (RRU) and an antenna.
- Optical transmission network with high bandwidth and low latency which connects the RRU and the Bandwidth-Based Unit (BBU).
- Centralized base band processing pool consisting of high performance general processor and real-time virtual technology.
C-RAN architecture includes the following advantages:
- The centralized approach can greatly reduce the number of base stations and the energy consumption of the air conditioning systems.
- Due to the high-density RRU, the distance from RRU to the users is shortened for reducing the emission power without affecting the overall network coverage. Low transmission power means that the terminal’s battery life will be longer and the power consumption of wireless access networks will be reduced.
Different from the traditional distributed base station, C-RAN breaks the fixed connection relationship between RRU and BBU that each RRU does not belong to any BBU. Sending and receiving signals in RRU is in a virtual BBU, while the processing capacity of the virtual base station is supported by the assigned processors in the real-time virtual allocation base band pool.
In the C-RAN architecture, the sites of BBU can be reduced by one to two orders of magnitude. Centralized base band pool and related auxiliary equipment can be placed in some key central machine room for simple operation and management.
Though the number of RRU is not reduced in C-RAN, due to the small size and low power consumption of these devices, they can be easily deployed in a limited space with the power supply system and without the frequent maintenance. As a result, it can accelerate the speed of the operational network construction.