Cloud RAN as an innovation for 5G
Is it disruptive or incremental?
The telecommunication industry has undergone tremendous change over the last 30 years, starting from 1G, where the consumer had access to voice only. 5G is the fifth-generation wireless technology that brings to the table new features for consumers, such as low latency (responsiveness), wider channels (speed) and extra bandwidth (for connecting a lot more devices at once). In the backdrop of 5G wireless technology, Cloud RAN (C-RAN) has been one of the major advancements in architecture for cellular networks.
How Cloud RAN architecture works
Traditional Radio Access Networks (RANs) consist of multiple standalone Base Transceiver Stations (BTS). Each BTS is used to provide cellular coverage to the proximate regions, and similarly, groups of BTS can cover large continuous areas. Each BTS is a standalone system, with its backhaul transportation and monitoring system. During the advent of 3G, this transitioned into a distributed base station. The radio function unit was separated from the baseband unit. With the next level of evolution, Cloud RAN placed all the baseband units in an architecture that is similar to a data center, wherein each baseband unit is connected to one or more radio function units or remote radio head.
The overview of C-RAN architecture with three main components, that are part of C-RAN architecture. A BBU (Base-Band Unit) pool, RRU (Remote Radio Unit) network and Transport Network (more commonly known as Fronthaul). The main function of each component is summarized below:
- BBU Pool:
The location of the BBU Pool is at a Cloud or a Data Center. It consists of multiple BBU nodes with large computational and storage capabilities. The BBUs perform the task of processing the resources as well as dynamically allocating them to different RRUs based on existing network needs.
- RRU Network:
These are essentially the wireless network that connects wireless devices like towers or access points in traditional cellular networks.
- Fronthaul or Transport Network:
This is the connecting layer between a BBU and a set of RRUs for providing high bandwidth links to handle the need of multiple RRUs. A Fronthaul can be implemented using different technologies, such as optical fibre communication, cellular or millimeter wave communication. For C-RAN architecture, optical fibre communication is ideal as it offers the best bandwidth requirement.
Advantages of deploying C-RAN architecture
The C-RAN architecture introduced a lot of advantages the primary one being resource virtualization. The earlier implementations required specific dedicated hardware, in most cases, single-vendor solutions. Because of virtualization, the baseband unit pool can be built using open hardware, e.g. x86, or ARM. Software stacks from different vendors can be executed on top of this open hardware to provision and provide different features. This shifted focus for a lot of hardware vendors like Ericsson (Mirantis) and Nokia (CloudBand) who have been providing the complete suite of products from servers to software stacks for Cloud RAN. Mirantis and CloudBand (the Cloud RAN suites) are built using OpenStack, an open source platform.
A host of such offerings are dependent on OpenStack, an open standard cloud computing platform. OpenStack was started in 2010 as a joint project between NASA and Rackspace. Network function virtualization, the core concept of Cloud RAN, is built on top of OpenStack. Because C-RAN solutions are built on top of OpenStack, the continuous advancements in the latter will lead to newer features, thereby, opening doors for a lot of indirect improvement in Cloud RAN.
In hindsight, we can see how back in 2018, Nokia was able to think of sourcing OpenStack from its open source community instead of going with a RedHat version. This move led towards Nokia introducing the features and fixes to be marketed faster, thereby, cutting down the time taken to get the enhanced version in the hands of the end consumer.
What is resource virtualization in C-RAN?
From a Cloud RAN standpoint, each baseband unit is virtualized in the form of Network Function Virtualization (NFV). NFV defines the high and low-level network functions on a virtual instance or a set of virtual instances. The network functions such as firewalls, network address translation, gateways, etc. running on the instances provide the radio access network functionality. The virtualization enables the logical isolation of resources while the underlying physical resources are shared in a dynamic and scalable way.
The baseband units in Cloud RAN share a common resource pool and hence are more resource-efficient. Adding or removing a baseband unit becomes as simple as turning a virtual machine on or off. The baseband units are connected to Remote Radio Heads (RRH) using Common Public Radio Interface (CPRI) or Open Base Station Architecture Initiative (OBSAI). This reduces dependence on costly and bulky equipment to increase network coverage and capacity.
One of the areas for development of the 5G network includes NFV. The concept of separating network functions from hardware effectively reduces the cost of network infrastructure equipment. This also enables thef telco network to respond quickly to any changes in network traffic or outages. The time to market for new services is also shorter due to network function virtualization. Anticipating a great demand for the 5G services in the future, some of the leading global companies are aggressively competing for patent filing and receiving the final grant on it.
One can say that Cloud RAN has been a game-changer for the telecommunication industry. Some challenges such as security and latency need to be taken care of. Since the basis of Cloud RAN is the implementation of software stacks, the security vulnerabilities of these software stacks will be carried into the Cloud RAN implementation. One of the primary aspects to take care of is latency. Latency higher than the current cellular communications can cause a major disruption in emergency services as well. However, with the implementation of RAN over Cloud, the advantages are immeasurable.
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