The story of mmWave is more than a century old, when Sir Jagdish Chandra Bose, one of the founding fathers of modern telecommunications, first reached up to 60 GHz in his lab in Kolkata. Up until the last few years, no one outside of academia or telecom R&D really talked about it. Since the advent of 5G, mmWave has seen more and more people talking about it.
The power struggle for the access for the bands is heating up, especially in India. Satcom wants it, telcos want it, the government wants it. So, what's with it? Why is mmWave being talked of like a game-changer?
A Brief History of mmWave
Technically, the mmWaves come under Extremely High Frequency designation by the IEEE. In the Indian context, however, the mmWaves comprise of the 26.5 to 29.5 GHz band. This band falls right on the edge of EHF, but lies in the SHF, or the Super High Frequency. Incidentally, the mid-band spectrum also lies in this range, and that is called, rather imaginatively, the centimeter waves.
Since this band has such a high frequency, the waves face quite a lot atmospheric attenuation. That is, gas molecules present in the atmosphere absorb the wave to an extent.
This is important, because it has deep implications for how 5G can be implemented over mmWave.
However, these shorter wavelengths have their own benefits as well. Small antennas can achieve the same amount of high gain and directivity as the lower bands. This translates, along with the high free space loss, in a more efficient use of frequencies for point-to-multipoint applications.
These highly directive antennas can go in a larger number than a normal antenna in a given area. Therefore, mmWaves can have a greater user density due to higher frequency reuse. This is precisely what makes the band precious to telcos - with India's urban tele-density at 141.03%, this could prove to be a game changer. Also, the high usable channel capacity in this band can also allow it to serve some applications that would otherwise use fiber-optics.
mmWave and 5G - An Ambivalent Relationship
This band has seen use in high bandwidth communication links, intersatellite links and so on. Even the WiFi 802.11 standard uses it in the 60 GHz spectrum band. What's even more interesting that some erstwhile Soviet Bloc nations also experimented with mmWave for any medicinal applications.
However, the band still remains relatively undeveloped in terms of civilian communications. This is where the aforementioned capacity to support high user density comes in for the band. Since it is so useful, it satisfies the primary requirement of a 5G network. Any 5G network needs to be energy-efficient in order to deliver good value for money to the customers and be a viable commercial venture for the service provider.
Over the past 5 years of 5G development, mmWave has really come out as a great candidate for carrying 5G. This is because 5G on low frequency just does not cut it. A prime example of this is when T-Mobile first launched a commercial 5G network, back in 2019, over the 600 MHz spectrum band. It was only able to deliver a 20% boost on the existing 4G network speeds, a far cry from the claimed 10-100 times the speeds.
“In some places, 600 MHz 5G will be a lot faster than LTE. In others, customers won’t see as much difference. On average, customers with a 600 MHz 5G phone should see a 20 percent download speed boost on top of what T-Mobile’s LTE network delivers, and with the New T-Mobile they can expect that to get exponentially faster over time, just like we saw when 4G was first introduced.”
This quote came from TMUS after Houston Chronicle called their network "underwhelming". If anything, this goes to show how important a high-frequency spectrum is for 5G. Here's the catch though - the range, it's not good.
The Headaches of High Frequency
The telcos can make use of the great usability of the spectrum, and the high capacity and bandwidth, that allows telcos to support dense urban settings, but that is it. There is no practical range to speak of, especially with mmWave.
T-Mobile CTO Neville Ray, said in a blog post back in 2019, that mmWave spectrum used for 5G "will never materially scale beyond small pockets of 5G hotspots in dense urban environments". This potentially means that no 5G for rural settings.
The GIF by T-Mobile shows how mmWave struggles to penetrate even glass doors. And there are a lot of them in cities to be fair. This low penetration, coupled with its limited range, implies that without telcos having to install a ridiculous amount of antennas. That means, 5G over mmWave is going to be useless outside of a very limited footprint.
To use the 5G to the best of effects, one has to stay within a limited footprint of around 1 square kilometer, where the reception is good enough. However, most of the people do not stay within such a small footprint.
It does not mean that it can't be used in rural settings. The sheer amount of infrastructure that it would require makes it prohibitively expensive. Let's take an example. Suppose a suburb is 10 kilometers away from the city center. Let's also suppose that we want to take the mmWave to this suburb from the city. Given the average range of 1-1.5 kilometers, we will need 5-10 antennas to just bring it to the suburb. That is a considerable amount of investment, no matter how you look at it.
The best use for mmWaves is to use it to deploy 5G in small pockets of high-density urban areas, it seems. And even then, it can't even penetrate materials, making it a really questionable investment to make.
However, GSMA called the use of spectrum above 24GHz "vital" for high-speed 5G. And it is - lower bands translate to lower speeds. This is largely because of the sheer amount of unused spectrum in higher bands. Also, one can count the bands with considerable unused blocks of spectrum below 1GHz on one hand.
The Best Recipe for 5G Deployment in India
Of course, there are three key spectrum bands for 5G usage. First, there are the sub 1 GHz bands, or low band, which has the 600 and 700 MHz bands. Second, there is the sub 6-GHz bands, or the mid-band, primarily the 3-3.5 GHz bands. Third, there is the mmWave, or high-band, spectrum.
For the rural deployment, the telcos need to have the low-band spectrum to build the network. The low band spectrum allows for great range, at the cost of speed. Speed remains a luxury for the underserved and unserved rural areas of the country, however. For intercity connectivity, mid-band spectrum will be helpful. And for close spaces in a city, mmWave can provide high-speed connectivity.
Basically, as the distance and user density decrease and increase, respectively, the frequency of the spectrum band increases. India is a large country, and there are multiple areas that are severely underserved. Therefore, for 5G to bring connectivity to the masses, telcos need to think about what should be the best mix for 5G deployment.
Telcos such as Bharti Airtel and Reliance Jio have repeatedly stated that they have deployed massive MIMO that is required for 5G. That is a step in the right direction. MIMO, or Multiple Input, Multiple Output, is essentially the technology that makes connectivity possible. With each generation, the amount of MIMOs increases. That is why deploying massive MIMO is such an important exercise - it shows the readiness of a network to deploy.
Is mmWave Important for 5G in India?
To be frank - it is not that important. Not at least for the initial rollout.
India's urban population is steadily growing and it has some of the most jam-packed cities in the world. Therefore, Indian telcos will need mmWave to support the cities. Apart from that, there is not much mmWave can do for telcos.
However, satcom can use the unused spectrum for internet from space, and telecom backhaul. This also allows for a massive B2B application for satcom as well in the country. The Indian government does not allow for satcom operators to provide backhaul to telcos.
The satcom operators are rather stubbornly asking for no selling of the mmWave spectrum in India, which has led to an impasse. The initiative lies with the government to whether sell it, or allocate it.
mmWave spectrum sure delivers fast 5G - the fastest 5G possible. But, India's needs lie elsewhere. India needs to look at filling the cracks in connectivity rather than papering over them.