With 5G, How Much Fiber is Enough?

Deploying a 5G network is complex. It is not simply upgrading the RAN and the core; there are layers of complexity, each intertwined with the next. To overcome the myriad challenges a successful 5G deployment encompasses, it is essential to understand the cause-and-effect implications of every decision. Each choice can impact the cost and the strength of a service provider’s business case.

5G has three core use cases:

enhanced mobile broadband (eMBB)
ultra-reliable low latency communication (URLLC)
massive machine type communications (mMTC).

Initially not all use cases will be implemented. For example, URLLC applications require certain network enhancements that early 5G deployments may not be able to deliver. But from the service provider perspective, planning for those requirements is essential for a future-proof 5G network. Building the best network infrastructure to support 5G use cases is the top priority for all major service providers. To achieve that goal, upgrading the underlying fiber network that connects the radios to the core is the critical first step to success.

While deploying fiber is costly, the benefits undeniably outweigh the deployment challenges. Fiber offers higher bandwidths (required for eMBB) with less attenuation, resists electromagnetic interference, offers lower latency (URLLC), and with improving multiplexing technologies, can accommodate capacity growth on the same fiber infrastructure.

Still, service providers grapple with fundamental questions: How much fiber is enough? How can fiber infrastructure investments today be leveraged for success as 5G matures? And they face the reality that without high-capacity backhaul, mid-haul and fronthaul, their customers’ 5G experiences will not be any better than 4G. Moreover, unaddressed latency issues introduce the same risk to the 5G business case. Applications including virtual reality and connected cars demand a delay-proof fronthaul.

The balancing act

An example of a converged fiber network that can accommodate 5G requirements as well as other access network architectures.

Identifying the right fiber topology for deploying a 5G network is the key to making the business case pay off. A variety of fiber fronthaul network topologies and technologies can be planned and implemented based on correct understanding of the requirements and goals of the network and getting fronthaul right. What does that mean?

1. It must be cost-efficient. Deploying fiber is expensive. If dark (unlit) fiber is available, it should be used initially and, as capacity demand increases, deployment of a next level of multiplexing (WDM) system and future planning can increase network capacity.

2. It must be flexible. Fronthaul must allow different applications with different latency and jitter budgets to work on the same fiber infrastructure.

3. It must be transparent. Fronthaul should allow multiple services with varying quality of service (QoS) to be implemented.

4. It must be agile. Agility will enable quick delivery of new services and dynamic allocation and release of network resources required by different services. The ability to dynamically optimize network connectivity also will be a key component of 5G fronthaul.

5. It must have perfect timing and synchronization. High latency and jitter cannot be present, especially for mobility and URLLC applications.

6. It must be easy to manage and maintain. Network failures in fiber fronthaul must be quickly resolved and high reliability for time-sensitive applications must be achieved.

And, for service providers with multiple service offerings, a scalable access fiber architecture that can easily support residential, business, enterprise, and 5G midhaul/fronthaul on the same platform is essential.

Testing the 5G network

5G’s massively larger bandwidth demands a much denser fiber fronthaul, midhaul, and backhaul network. This means not only more fiber cables and end points, but also a higher order of multiplexing that in turn increases the complexity and scale of fiber testing. Previously we had a fiber cable pair connected to a radio. Now, this has evolved to upwards of 12 or more fiber pairs per radio. As a result, a visual fault location tool will not suffice to validate fiber signal integrity. Technicians may see light at the other end but will have no way to validate a specific wavelength path is correct.

Further, in a WDM system, testing for correct power levels will require different sets of instruments. Many fibers will drive more MPO connector deployments, which will require an MPO light source and an MPO tester. Ultimately, fiber field installations will be more complex with significantly more MPO and xWDM deployments.

This increase in the number of fibers and the types of connections will drive the need for service providers and their contractors to have easy-to-use fiber test instruments with integrated test process automation to scale 5G deployments.

Keys to a winning strategy

The optical infrastructure serving fronthaul, mid-haul, and backhaul must be flexible, agile, and futureproof to meet 5G high-bandwidth demands and significantly higher cell-site density. The topology of the chosen fiber infrastructure must maximize return on investment from short-term deployment to long-term network growth models. Managing and maintaining fiber infrastructure will be a constant operational expense that must be considered at the time of deployment. Having the right test solutions for maintaining fiber networks will be key in delivering high quality of service at low opex.

Kashif Hussain is the director of solutions marketing with VIAVI Solutions and has more than 20 years of experience in mobile networking and wireless technology. His expertise in RF, DAS, HetNets, and LTE comes from developing, managing, supporting, marketing, and consulting on major mobile communications projects. His industry experience also includes various senior roles at MobileNet, Tektronix Communications, Ericsson, and Nortel. Kashif has also authored patents for wireless products.