There has been a drive towards the use of fronthaul in recent years due to the advent of 5G densification and related use cases. Fronthaul is essential to 5G small cell optimisation, improving capacity, managing interference, improving reliability and lowering cost per bit of data intensive distributed 5G applications. In this blog we’ll discuss what 5G fronthaul is, its advantages and the value an integrated mmWave fronthaul platform can bring to it.
What is fronthaul?
Fronthaul can often be confused with backhaul, which is the network link between the core network and the edge. For example, when supplying connectivity to large numbers of home broadband users, the system would use a backhaul somewhere in the delivery to your home. Fronthaul on the other hand, uses a network to transport packetized frame structures that are used to join a 5G modem processing pipeline, it’s not a generic network.
Fronthaul connections are part of an architecture that splits the 5G wireless modem processing pipeline into separate standardised stages connected by standard networking interfaces. A fronthaul architecture typically connects many radio units (RU) to a single distribution unit (DU), so that there is a fork into multiple distributed 5G air interfaces.
Fronthaul architectures use several standard splits to the physical RUs, so that different levels of control of the air interface is possible. The types of splits are standardised in the Open RAN architecture specifications. The lower the split the more bandwidth required along with tighter timing and latency constraints. Typically, lower fronthaul splits (Split-7 and 8) use fibre-based networks where the demanding requirements are catered for.
For instance, Split-6 fronthaul uses a single DU to construct multiple transport block frames populated from previously backhauled network packets. The DU sends these block frames to multiple remote 5G RUs which collectively process them for transmission on-air. These highly coordinated collections of 5G RUs, tightly managed by the DU, provide optimisation opportunities for better management of proximity of 5G RU small cells.
What is driving the need for fronthaul?
There is a significant industry move to Neutral Host 5G infrastructure using disaggregated Open RAN technology. The standardised networked components provide a mix and match of supplier of interoperable components to lower the costs for a given 5G application.
Open RAN and related, standardises many advanced fronthaul feature benefits of 5G. These features, known as ‘CoMP’ (Coordinated Multi Point), significantly improve performance and thereby adding additional capacity, which is critical in the push for 5G densification in urban scenarios. The efficiencies that CoMP brings are well worth the cost of the additional complexity and infrastructure and are in wide usage in larger macro base stations in many cities today.
The benefits of mmWave technology for Open Ran fronthaul
Previously a fronthaul network uses dedicated optical fibre that extends over many kilometres out from a centralised macro base station installation. However, in recent times it has become possible to place more compact infrastructure components directly onto street furniture for more numerous localised lower cost sites. However, the economics of a using fibre distribution makes this uneconomic with an often-lengthy costly process that involves seeking permissions to dig up the street and then lay the fibre.
Using a mmWave wireless technology to provide the fronthaul connections from the DU to RUs provides a cost-efficient alternative to fibre with almost no additional infrastructure requirements over and above access to street furniture and power. Installations using secure Self Optimising Networks (SON) wireless nodes simplify installation, with setups being measured in days and additionally enabling remote NMS management and telemetry.
Recent spectrum management authorities have made large swathes of both licensed and unlicensed mmWave spectrum available. However, the copious 14GHz of unlicensed spectrum known as the 60GHz “V” band, provides six 2GHz wideband channels, dwarfing any licensed band and providing a variety of options for closely packed non-interfering channels. This removes licensing costs, making this technology option very attractive.
Using 2GHz wideband channels not only provides high-performance highly directional beamformed links but are also inherently low power (the reason why it’s unlicensed). The low power makes the overall system physically smaller and more manageable for integration into low cost 5G small cell street furniture.
Blu Wireless’s mmWave fronthaul platform technology
Even though the recent fronthaul specifications have been adapted to become more friendly to network technologies other than fibre, fronthaul’s exacting demands are still impossible to implement with many generic mmWave backhaul technologies on the market today. The mmWave technology platform must have sufficient system performance and flexibility in its design to meet the tight latency and other specification requirements.
Blu Wireless has built a mmWave technology platform specifically so the most demanding of applications can be implemented on it. Each of the programmable technology layers, from the antenna, through the PHY, MAC and network layers have been carefully designed and integrated so that they can all be adapted for specific applications.
These layers are orchestrated with an Intelligent Control Plane (ICP), which provides a programmable integration between the mmWave beam management and software defined networking. The ICP provisions standalone plug and play mmWave nodes that can be placed ad-hoc onto street furniture which autonomously form secure optimised fronthaul networks without intervention.
In this case, the Blu Wireless mmWave platform has been specifically adapted for Split-6 fronthaul. The requirements for low latency, timing and control of transport block frames have been carefully developed and tested for reliability in a variety of system implementations.
Integration of Open RAN technology with unlicensed mmWave systems drives down capital-intensive deployment costs by removing the need for excessive fibre. This enables the scale up of multi-node 5G Small Cells for new economically attractive business opportunities for 5G densification.
If you’re interested in learning more about how Blu Wireless can help with your fronthaul project, contact us today.