For the long haul

Fronthaul refers to the fiber-based connection of the cloud radio access network (C-RAN), a new type of cellular network architecture of centralized baseband units (BBUs) and remote radio heads (RRHs) at the access layer of the network. Fronthaul complements backhaul connections between the central network and BBU, enabling the rapid transfer of data and denser network coverage.

Fronthaul is made up of standalone radio heads and centralized baseband controllers installed and located at remote cell sites. The RRHs -- also known as radio units -- and BBUs form functional blocks, and the equipment that enables them is located on the cell towers. The RRH hardware remains at the cell site. The BBU is relocated to a centralized location to serve multiple RRHs. The optical network links that interconnect multiple RRHs with the centralized BBU are called fronthaul.

Backhaul refers to the connections between a mobile network and a wired network that backhaul traffic from disparate cell sites to a mobile switching telephone office. These interconnected links form macrocell sites where data is quickly transferred from slower T1/E1 connections based on time-division multiplexing (TDM) to packet-based Ethernet-over-fiber links. These macrocell sites also house BBUs, which process control and user data, and connect to radio units (RUs).

Wireless backhaul is the use of wireless communication systems to transport data between the internet and subnetworks. It can help an organization or mobile network eliminate the need for physical cabling. On the other hand, mobile backhaul refers to the transport network that connects the core network and the radio access network (RAN) of the mobile network.

Fronthaul and backhaul both play a part in connecting the end user or node to a major network. A primary difference between fronthaul and backhaul is the part of the network the technology is used on. Backhaul links the mobile network to the wired network, while fronthaul describes the network architecture that connects the remote cell sites to the BBU.

When you bring together fronthaul and backhaul architecture (as well as midhaul), it is also known as crosshaul. Midhaul is the Carrier/Metro Ethernet Network between RAN base station sites. In a hierarchical telecommunications network, the backhaul portion of the network comprises the intermediate links between the core network, or backbone network and the small subnetworks at the “edge” of the entire hierarchical network.

There are several different types of fronthaul networks that enhance speed and provide low latency.

Enhanced common public radio interface (eCPRI). This fronthaul network helps standardize the split architecture inherent in 5G fronthaul components that separates RRHs from the BBU. It decreases the data rate demand and complexity between the radio equipment and radio equipment control.

Passive optical networks (PONs). PONs use optical splitters and point-to-multipoint topology. Passive fiber splitting in support of statistical multiplexing is a potential counterbalance for the density of RU connections inherent to massive multiple input multiple output (MIMO) technology.

Wavelength-division multiplexing (WDM). These networks use laser beams to combine multiple signals at varying infrared wavelengths for fiber-optic transmission. They enhance the efficiency of fronthaul fiber links. By transmitting over multiple wavelengths, traffic from several antennas can be sent through the network over a single dark fiber.

5G fronthaul facilitates enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (uRLLC) and massive machine-type communication (mMTC) for internet of things (IoT) networks. 5G provides gigabit (Gb) speeds and low latency, and it helps establish fronthaul transport capacity. Fronthaul enhances network performance, making it more flexible and efficient.

The evolution of fronthaul in mobile networks has mirrored the increasing reliance on optical fiber for broadband networks. Prior to the release of 4G, fiber was used primarily for transport networks. Higher performance standards, the development of MIMO technology and advanced radio coordination practices dovetailed with the arrival of remote radio solutions and the introduction of fronthaul to the optical fiber lexicon.

Among the challenges facing the development of mobile fronthaul networks are limited network options and a shortage of expertise in the field. These issues could restrict growth over the next few years. But 5G networks offer lucrative opportunities to scale, and enterprises are expected to overcome these challenges.

Glow’s role

Glow provides a solid 5G base that facilitates the implementation of fronthaul and backhaul technology. It provides a network of services to help in the adaptation of 5G for different use cases. It is expected to make leaps and bounds in the rollout of 5G services in the days to come.