Why mobile phone frequency bands affect 5G network interoperability

In the early morning of October 14, Apple released the latest iPhone 12 series phones, although there are upgrades in the shape design, application materials, and chips, but the iPhone 12 Pro’s 5G function can not be used in China, which makes many domestic consumers confused, is the 5G in the United States is not the same as China’s 5G?

The global 5G network frequency band is mainly divided into Sub-6GHz and millimeter wave (mmWave) two major ranges, at present, China’s main use of Sub-6GHz. iPhone 12 Pro and iPhone 12 in the use of frequencies are 5G (mmWave) and 5G ( (sub-6GHz).

According to the definition of 3GPP version R15, 5G NR (NR is the “gap”, the airborne propagation of electromagnetic waves between base stations and mobile phones) consists of two frequency ranges, 5G spectrum is divided into two regions, FR1 and FR2, FR is the frequency range. FR1 is from 450MHz to 6000MHz, with a spectrum number from 1 to 255, and Sub-6GHz refers to this band. fr2 is from 24250MHz to 52,600MHz, with a spectrum number from 257 to 511, and usually refers to millimeter wave, although technically, millimeter wave speaks of the band above 30GHz. So what is the essential difference between the two operating bands?

We learned in middle school physics class that the speed of light equals wavelength times frequency, and in a general environment where the speed of light is constant, the relationship between frequency and wavelength is a reciprocal relationship of one to the other.

5G networks in the millimeter-wave spectrum have relatively greater bandwidth because they operate at very high frequencies, so that the infrastructure under the spectrum can provide gigabit-level speeds and very low-latency connections, so that files will be transferred very quickly. But because millimeter waves have a very short wavelength, it causes the signal to be extremely sensitive to physical obstacles, and penetrates poorly, so a wall may be in the way and your phone or other 5G device will have a weak signal or no signal. To address the weakness of millimeter waves, more base stations would need to be built to deploy 5G networks, which would be too expensive to build.

5G networks in sub-6GHz spectrum will be much slower in transmission speed compared to 5G networks in millimeter wave spectrum, which is like an enhanced version of 4G compared to 4G networks. However, the advantage of sub-6GHz is that the wavelength of this spectrum can penetrate walls and buildings better, greatly enhancing signal stability. In addition, the construction of base stations is much smaller than that of 5G networks in the millimeter wave spectrum, which has a huge advantage in construction costs. China’s 5G network deployment is currently working mainly in the sub-6GHz spectrum range.

So why can’t the iPhone 12 Pro’s 5G capabilities work in China? This is because the U.S. already occupies sub-6GHz spectrum 5G networks on the government and military, social applications can only be more selective millimeter wave spectrum 5G networks, while China’s 5G network uses sub-6GHz, so the iPhone 12 Pro can not be used in China for the time being.

Because the working bands of 5G deployment vary from country to country, it’s understandable that Apple’s 2020 iPhone 12 Pro handset will support different 5G networks depending on the region where it’s being sold.

At present, China’s application of millimeter wave is not very meaningful, but with the development of time, the domestic key cities are increasingly densely populated, the future of the millimeter wave application in hotspots, in some of the highest input-output ratio to some hotspots to add capacity is also a good choice.