With coming dual connectivity capabilities, allowing a single 5G device to use capacity resources from two radio sites, we can point to one new way 5G can build on 4G: 4G often will provide coverage, while 5G provides capacity, for any single user or device.
The point is that 5G NR, whether in sub-6 GHz or mmWave bands, can leverage much of the existing 4G infrastructure. 4G for coverage, 5G for capacity is one way to view the matter.
Dual connectivity is key, in that regard. Where carrier aggregation allows a device to use more than one capacity asset (different spectrum) at a single radio site, dual connectivity allows use of assets from two radio sites simultaneously.
In other words, a device can use capacity from two cells, not just one. That is another way of saying both 4G and 5G capacity can be used, at the same time, by a device connected to two different cell sites.
Just siting 5G NR radios at 4G towers is one simple example. And while that approach works better when 4G is paired with 5G in mid-band spectrum, even use of millimeter wave spectrum provides significant coverage and cost results, says Qualcomm.
Even when co-siting millimeter wave 5G, Qualcomm says it “saw significant mmWave outdoor coverage for both downlink and uplink just by co-siting with existing LTE infrastructure, and as expected with mmWave, the median burst rate is well over 1 Gbps with many cities delivering beyond 2 Gbps.”
“Even at the cell edge, with suboptimal signal quality, mmWave can deliver throughputs of over 300 Mbps, which is remarkable compared to just a few Mbps that today’s networks are capable of at the cell edge,” Qualcomm has noted. “In fact, many operators have been deploying small cells to leverage capacity and performance benefits from technologies like LAA (licensed assisted access), and this dense heterogeneous deployment allows delivering near-ubiquitous outdoor coverage.”
That means a more-graceful way to use both 4G for coverage and 5G for capacity.
Some observers are critical of 5G deployment hype, capital investment dangers, use case uncertainty and therefore business model risk. That is reasonable enough.
But we often forget that 5G uses many new techniques for reusing existing 4G assets, including signaling networks, radio sites, backhaul, changes in network architecture, radios and spectrum aggregation that allow a more-graceful approach to 5G deployment. And that means the feared capex dangers are far less than some have predicted.
In fact, in the early days, the primary value of 5G is to augment 4G smartphone capacity demands, within existing capex budgets, for the most part, often reusing existing physical assets. In fact, one now-obvious key is that advanced 4G networks will essentially become the coverage complement to capacity-focused 5G.