What’s next after mmWave networks? – Madden
Mobile traffic demand continues to grow at 50% every year. Where will this ride end?
At Mobile Experts, we have been forecasting strong growth for millimeter wave (mmWave) networks, as the operators will run out of capacity below 6 GHz and they will need to double their capacity every two to three years in the future. There’s no economical way to deploy so much capacity below 6 GHz, so mmWave is a good bet for the next five years.
Here’s one chart to illustrate our view of the current situation in the U.S. with C-band spectrum fully engaged. As you can see, in dense urban zones, the mobile network will run out of sub-6 GHz capacity (yes, including C-band capacity) in 2023 because traffic growth is so strong.
Today, I’d like to examine the long term. What’s the end-game here? Do we really believe that we can operate a network effectively with half of our capacity on mmWave links?
In theory it seems like a fine idea. But we know that 80% of traffic is consumed indoors. So, if 50% of our capacity is handled by mmWave networks, and 80% of traffic is indoors, that means that at least 30% of mobile traffic requires mmWaves to penetrate the walls of the building.
Logically, we conclude that we need repeaters or other magical devices for penetration through walls. We’re forecasting that this will happen, but I’m unsure about some use cases. For example, in the dense urban pockets where buildings are 20 stories tall, a repeater strategy must involve the permission of commercial building owners, not just a simple consumer CPE unit.
Millimeter wave will bring truckloads of capacity, so it will solve our capacity challenge for the next four to six years. And it will continue to shoulder a heavy load in future broadband data demand for another 20 years. By adding about 1 GHz of new mmWave spectrum every three years, the mobile operators will be able to keep up with data demand and maintain their data traffic density at a level of about 0.1 Gbps/km2/MHz (GkM) through about 2027. After that, we will need a combination of new low-band spectrum and mmWave spectrum to keep up, or the traffic could become unmanageable.
I know, you’re probably thinking that mobile traffic growth won’t continue at 50% per year forever. I agree. My model ramps down the data growth gradually to 25% growth in 2030. It’s clear that strong mobile data growth can continue, based on the heavy data demand in fixed broadband networks. Households with fixed broadband routinely use hundreds of GB of data per month, while smartphones use 20-30 GB per month on the best networks. So, even without big industrial or other enterprise applications, we can see a path toward 10 years of growth.
The ideal case is to handle crowded indoor and outdoor spaces with mmWave, and to penetrate walls with low-band spectrum. With 80% of traffic indoors, we will need a combination of products in the long term: Indoor mmWave small cells, repeaters, and eventually Cognitive Radio.
By 2030, we will be introducing 6G, and, as always, we will tailor the new generation to meet the challenges that we face. I believe that 6G will include a strong technology push for Cognitive Radio, to liberate spectrum that is currently under-utilized between 20 MHz and 4 GHz.
My analysis reveals that in highly developed countries, at least 2 GHz of spectrum could be used on a part-time basis, effectively sharing spectrum between government users and commercial users with “smart” radio technology. (CBRS is a good example of Cognitive Radio technology where spectrum can be shared among critical users and commercial users).
So, if you’re working on technology for 6G, consider the need to penetrate brick walls without the permission of the building owner. Physics will guide you below 10 GHz, where all of the bands are spoken for. It’s time to get more creative and make shared spectrum a major global initiative.