5G will need to have a range of tricks up its sleeve to deliver, however. One such trick is an evolved fronthaul – technology that has proven itself through the years by morphing as needed to take on telecom’s most complex challenges.
Key to understanding the role fronthaul will play in next-gen networks is understanding the demands that will be made of it in 5G environments. In this two-part blog series, we’ll explore these new requirements, track the evolution of the fronthaul interface to 5G radio units, highlight the challenges faced along the way and the solutions that will help assure the promises being made on 5G’s behalf.
Fronthaul’s journey to the frontlines of innovation
Assuring the performance of 5G requires the complex transmission of video, data and voice over the Radio Access Network, from the core network to end devices, at ultra-fast speeds of 1Gbps and ultra-low latency of 1-5ms.
The air interface between the antenna and devices is defined by 5G New Radio (5G NR) standards, which support a wide range of frequency bands and use cases. Transport between the 5G core network and the 5G NR must also be enhanced to support higher bandwidth, lower latency, and increased capacity and reliability.
Initially, that transport network was separated into fronthaul and backhaul transmission networks. Fronthaul was defined as the transmission between the baseband processing and RF transceiver parts of the base station and the backhaul connected the baseband unit to the core network. But over time, the transport network evolved to take advantage of flexible, shared network architectures like Ethernet and fiber connectivity. These advancements have enabled increased performance and cost savings through centralized baseband processing and distributed radio units.
The distributed 5G Cloud RAN
5G Cloud RAN (also known as C-RAN), separates the radio elements of the base station from the elements processing the baseband signal. The baseband units, called Centralized Units or CUs, contain the main RAN intelligence and can be centralized in a single location or virtualized into the cloud. This can simplify deployments by decreasing equipment footprints and improving network efficiency by allowing for centralized management of resources. It also reduces the complexity of the radio equipment at the network edge. As a result, fronthaul can connect a cluster of radios to create ultra-dense 5G macro and small cell networks close to the end user.
Meeting performance challenges with 5G Cloud RAN
The 5G Cloud RAN must meet backhaul link latency requirements of about 40ms and middlehaul link latency of just 1ms and tight fronthaul latency of 100 µs to enable the lauded 5G user experiences. Ultimately, the placement of data and processing will be determined by the supported 5G applications.
While there are many challenges to meetingperformance requirements, its evolved architecture provides several technical benefits that make the journey worth taking, including:
Radio units can be highly distributed while more complex and expensive baseband processing can be centralized;
Less latency-sensitive functions can be located further back in the network and even virtualized in the cloud on commercial-off-the-shelf hardware;
Support for flexible, standardized Ethernet versus proprietary connections;
Ability to use fiber to support high data rates; and
Data and applications can be placed much closer to the end-user, powering edge compute services.
In short, 5G C-RAN enables operators to deliver excellent user performance while reducing costs with simpler cell sites, centralized and shared baseband processing, and cost-effective non-proprietary equipment.
Meeting the 5G user experience performance requirements
Enhanced 5G user experiences demand ultra-fast speeds, ultra-low latency, massive capacity and higher reliability. Meeting these requirements poses significant demands on the radio network and requires an evolved fronthaul architecture, which must economically support the speeds and latencies required by.
In a network of multiple devices, it is often required that all elements operate on a common time base or clock. Multiple enhanced radio techniques that are essential to assuring 5G’s user experience benefits all rely on a tightly synchronized 5G fronthaul network. In the second half of this blog series, we will discuss this important and challenging detail.
Guest contributor: Tim Frost, Strategic Technology Manager, Calnex Solutions