More than just the next-generation wireless technology, 5G seeks to serve as an enabler for a broad range of applications and markets. The vision is the ubiquitous capability to provide every connected human, device, and system a much faster and more reliable wireless experience.
These are lofty goals, to be sure, ideas that tend to generate equally visionary and energetic debates. In fact, GMSA’s 288-page “5G Guide” (2019) begins with an observation that most any discussion regarding 5G typically revolves around the same core themes:
- The superiority of 5G technology compared to previous generations
- Definitive, yet somewhat elusive, new 5G use cases
- Spectrum availability, how it is allocated, to whom, and at what cost?
- Political ramifications, including international 5G races, debates over patents, security loopholes, trade wars, urban versus rural coverage, etc.
There is a fifth theme, the 5G Guide points out, that—while less glamorous—is perhaps even more critical:
“Fifth, there is the less headline-grabbing, yet practical task of upgrading the mobile infrastructure with the latest technology (i.e., 5G) based on a sustainable business case. This perspective is often missing from the news and commentary about 5G.”[i]
Network infrastructure—whether the macro layer, small cells, or edge connectivity—represents the glue that needs to hold everything together. So, while conversations around potential 5G use cases, national sovereignty issues, and the next evolution to 6G tend to make the news, without a robust, flexible, and affordable infrastructure, the whole thing falls apart.
Flavors of 5G
In response to the diverse strategies of 5G deployment, five alternative network architectures have been proposed to 3GPP by different mobile operators.[ii]
Within the 5G conceptual framework, these architectures fall into two main categories: standalone (SA) and non-standalone (NSA). Both network architecture approaches are defined in the 3GPP specification TR 21.915.
SA 5G infrastructure uses 5G new radio (NR) technology connected to a dedicated cloud-native core. As its name implies, a standalone infrastructure exists as an independent network layer, separate from the existing 4G architecture. It consists of a radio access network and a new radio interface on the user side, and a 5G core built around a service-based architecture and a heavy dose of virtualized network functions.
The downside of the standalone approach is that it does not enable operators to leverage and extend the value of their existing 3G/4G investment. The non-standalone approach, by contrast, combines a 5G RAN/NR interface with the operator’s existing 4G LTE infrastructure and core to provide a “5G-like” experience. While not widely seen as a long-term 5G solution, it enables operators to deliver on many of the promises of 5G now, as they work toward building an independent SA 5G infrastructure.
5G Transport is Front and Center
In attempting to solve the infrastructure puzzle, one of the more complex challenges 5G engineers face is the design of the transport network—fronthaul, midhaul and backhaul. Planners need to understand the differences among the protocols, capacities, latencies, reaches, and associated applications of the entire mobile network. Currently, the work on creating the 5G ecosphere focuses on three major use cases: enhanced mobile broadband (eMBB), ultra-reliable and low latency communications (uRLLC) and massive machine-type communications (mMTC). Each application adds yet another layer of complexity to transport network design, particularly if they coexist on the same network.
The challenge facing MNOs is there is no one-size-fits-all option; various RAN transport solutions are needed. For example, possible 5G transport solutions for small cell, macrocell, and network slicing applications utilize innovative optics, passive wavelength-division multiplexers (WDM), time-sensitive network components, Layer 3 routers, and service orchestrator operation.
So, network designers must be able to navigate the intricacies of 400G optics, time-sensitive networking (TSN) standards for C-band, use of millimeter-wave, network slicing, open service orchestration, and much more. It’s a lot to take in, but there are plenty of helpful resources to get you going.
To understand how the various approaches can be integrated and what you need to know to do it, start with the recent Fujitsu article, “A Tactical Transport Toolbox for Strategic 5G Deployment”, published in the November 2021 issue of Lightwave’s On Topic report on 5G strategies.
This article is an excellent primer on how advanced transport technologies are transforming RAN approaches and paving the way for today’s NSA and tomorrow’s SA 5G networks. It’s written from the perspective of a network partner who’s been a valuable member of the wireless ecosystem since nearly day 1.
[i] Optical Transport for 5G Mobile Network: Challenges and Solutions; IEEE Future Networks; October 2021
[ii] G. Liu, Y. Huang, Z. Chen, L. Liu, Q. Wang and N. Li, “5G Deployment: Standalone vs. Non-Standalone from the Operator Perspective,” in IEEE Communications Magazine, vol. 58, no. 11, pp. 83-89, November 2020, doi: 10.1109/MCOM.001.2000230.
