Cracking the Rural Access Nut: Is 5G the Answer?
5G mobile networks are being marketed on the promise of enabling exciting new applications such as augmented reality, autonomous vehicles, and telesurgery. But more utilitarian applications of the technology, such as bringing reliable broadband connectivity to rural communities, will provide the greatest early benefits.
In a February 2021 survey conducted by Molex in partnership with third-party research firm, Dimensional Research among 5G carrier network professionals working in R&D, product, or engineering roles, 43% of executives surveyed said they thought that consumers would be the first to benefit from 5G, followed by industry and industrial IoT applications. This band was then followed by fixed wireless strategies – such as wireless broadband access for rural communities. These early adopters of 5G are expected to start seeing benefits years before more eye-catching applications such as autonomous vehicles and remote medicine.
5G promises to bring much higher data rates, support many more connections per unit area served, and will have much lower latencies than previous generations of mobile networking technology. The challenge for 5G equipment makers and network operators is that it is difficult to achieve all these benefits at once within a single RF band, so network equipment and mobile terminals need more complex radio interfaces and base station deployments than have been necessary for 4G networks to date.
Why is this? The answer, in part, is due to the physics of radio transmission: higher radio frequencies can carry more data than lower frequencies but since real-world propagation distances are inversely related to signal frequency, they don’t reach as far. The 5G spec addresses this conundrum by defining two overlapping bands of radio spectrum, FR1, and FR2. FR1 covers the sub-6GHz range, with a spectrum from 410MHz to 7125MHz. Signals on the FR1 band will achieve good coverage, as evidenced by the distribution of today’s 4G base stations, many of which operate at mid-band FR1 frequencies. However, FR1 signals will not support the higher data rates possible with millimeter-Wave (mmWave) frequencies. Another drawback of the FR1 bands is that they are already crowded with competing signals from WiFi, GPS, Bluetooth, and Zigbee signals, as well as electromagnetic interference from other sources.
5G’s FR2 band specifies the use of mmWave frequencies ranging from 24 to 52.6GHz. These offer more bandwidth and higher data rates than possible at FR1 frequencies, at the cost of much shorter propagation distances and greater use of small-cell base stations to provide line-of-sight connectivity for users in dense areas such as city centers.
For network equipment and handset developers, therefore, the challenge involved in implementing 5G is to decide which bands to support (not all bands are being implemented in all regions), and then to build the complex RF interfaces needed to do so. For many equipment makers, supporting mmWave spectrum will involve developing new skills, since microwave signals are more sensitive to issues such as PCB routing, impedance matching in connectors, antenna design and tuning, materials choices and more, versus lower frequency solutions. Many 5G implementations will also implement multiple-input, multiple-output (MIMO), beamforming, and beam-steering strategies to make the best use of the available spectrum. This will demand the design of efficient multiple-antenna mmWave arrays, which will often have to coexist with separate antenna arrays for FR1-band signals. Designers will also have to make trade-offs between the efficiency and bandwidth of the RF power amplifiers needed to drive these antennas and then implement all this with high signal integrity, low mutual interference, and effective heat management, in the very close confines of a handset or small-cell enclosure. It’s not easy.
What does all this tell us about the opportunities for 5G in rural settings? First, the challenge in rural settings is clear: it’s often difficult to bring the benefits of broadband connectivity to rural communities because the cost of distributing bandwidth from a central point to widely distributed remote users is just too high. Subscription revenues can never pay for all that trenching and cabling.
5G could address these issues by providing fixed wireless broadband access, using a strategy known as integrated access and backhaul. In this scheme, a central base station is connected to the rest of the cellular network over a buried fiber, microwave point-to-point link, or even just a dedicated 5G link. The bandwidth that this connection brings in is then redistributed over 5G to fixed wireless terminals at each subscriber’s home. Using mid-band FR1 frequencies enables good geographic reach, while beam-forming strategies and high-gain antennas in the home terminals help get the most out of the available spectrum. Switching to mmWave FR2 frequencies provides greater data rates over shorter distances and so may make more sense in rural clusters or built-up urban areas. Either way, experiments by Ericsson suggest that this integrated access and backhaul strategy can provide connectivity that is good enough to stream 4k video and in many cases has offered higher data rates than wired home broadband offerings.
So the opportunity exists to create entire ecosystems of home terminals, repeaters, small cells, and base stations that can bring 5G to widely distributed communities at a reasonable cost. For OEMs, the challenge of doing so is twofold: to understand the critical gating factors such as the potential markets for such equipment, the availability of spectrum, and the progress of enabling regulation; and to address the technical challenges of designing and building such sophisticated mmWave equipment at relatively low cost for long-term deployment in arbitrary conditions around the world.
Molex has been analyzing evolving global and regional cellular market needs and developing relevant solutions for decades. We understand issues such as high-frequency micro-connector development, mmWave antenna design, and the impact of physical configurations and materials choices on RF performance as well. Molex has also developed effective testing strategies for low-band, mid-band, and mmWave devices, complete with an anechoic chamber that enables verification that our 5G solutions meet the required specifications. Further, our teams have leveraged different types of advanced simulation software in the most effective ways for each design challenge, which can streamline development time and costs. And we have special production facilities that enable tight integration of complex electrical and mechanical structures in three dimensions, controlling performance while also saving space.
5G offers exciting new capabilities for mobile communications, but it may be that one of its most immediately useful applications will be in bringing broadband connectivity to communities that otherwise had no access. For families choosing to call rural locations home and factories in remote locations that require automation equipment and robotics to drive speed and accuracy in the manufacturing process – 5G is the future.