5G RAN

- 5G RAN

Radio access networks have evolved over the years as cellular technology is now at 5G. Today, RANs can support multiple-input, multiple-output (MIMO) antennas, wide spectrum bandwidths, multi-band carrier aggregation and more. This evolution of RAN for 5G will have a huge impact on wireless technologies, including enabling Mobile Edge Computing (MEC) and network slicing. These RANs of the future will also contribute to the lower latency that makes 5G so powerful.

There is a lot of flexibility built into the network architecture of 5G that enables it to address a wide range of use cases that are beyond the capabilities of 4G. The flexibility includes things such as the desegregation of the control and user plains of the network and also migration towards distributed baseband processing and the radio access network (RAN). In turn, this leads to opportunities for virtualization of RAN network functions and it enables the convergence of the RAN into the data center space. 

While many of the baseband functions in 5G architecture become virtualized, some of them may still require some hardware acceleration and it’s for this reason that a logical move would be to co-locate some of the architecture with other data center infrastructure, and with things like mobile edge compute.

- C-RAN Architecture

As 5G is capable of transmitting petabytes of data, it is more cost-effective for mobile network operators (MNOs) when handling these large volumes of traffic to deploy C-RANs, in addition to improving network performance via low-latency connections. 

The components of a C-RAN architecture include: a centralized baseband unit (BBU) pool, remote radio unit (RRU) networks, and fronthaul or transport network:

• The BBU pool is located at a centralized site and functions as a cloud or a data center. Its multiple BBU nodes dynamically allocate resources to RRUs based on current network needs.
• Wireless devices connect to the RRU network, similar to how they connect to access points or towers in traditional cellular networks.
• The Fronthaul/transport network serves as the connection layer between a BBU and a set of RRUs. It uses optical fiber communication, cellular communication, or millimeter wave (mmWave) communication to provide high-bandwidth links for multiple RRUs.

- BBU and RRH

A mobile network divides a region into cells, with each cell covered by a radio base station. These base stations are typically mounted on towers (or tall buildings), with the sites owned by tower companies and the equipment owned by telecoms in most developed countries. Mobile devices (smartphones, tablets etc.) within each cell communicate with the nearest base stations via radio for voice and data communication, where the signal is then transmitted to the core network either via cables or high-frequency radio links to a terminal (edge router) 

A radio base station can be functionally separated into:

• BBU (baseband unit, or a digital unit), which generates and processes a digitized baseband RF signal
• RRH (remote radio head, aka RRU, remote radio unit), which creates the analog transmit RF signal from the baseband signal and sources it to the antenna respectively, digitizes the RF receive signal

In brief, BBU possesses the “digital” function, RRH possesses the analog.

5G will require a tremendous increase in the number of base stations since 5G would be using much-higher-frequency spectrum. In the traditional RAN (radio access network) architecture, each cell site requires its own dedicated BBU and RHH, along with the associated power, cooling and routing functionality. The tremendous increase in base stations will cause major capital expenditure and operating expense concerns, which would significantly limit the number (and locations too) of base stations could be deployed. Without a rapid and massive deployment, the sparse high-frequency 5G base stations will be incapable to accommodate.