Sub-6 and Millimeter Wave (mmWave) frequencies for 5G — All you need to know
Originally published on my personal blog.
5G is the next obvious upgrade to 4G and LTE that we use extensively today for our data needs when we’re on the go. LTE was a huge upgrade from the much slower 3G a few years back. But in 2019, we’re seeing over 1Gbps speeds with 5G. To make this a reality, wireless carriers are using a combination of different technologies and waves. In this post, I’ll try to explain two of those which we see and hear in most conversations revolving around 5G — Sub-6 and Millimeter waves.
To understand sub-6 and millimeter waves (mmWaves), we first need to understand how our smartphone radio signals function. As you all know, we have cell phone towers or antennas placed all around us which provide our phones with the coverage they need to keep us connected to the network. But what most people don’t know is that these towers are placed at strategic geographical locations (and just at random locations) to maximise the coverage of the signal they emit. Each tower covers a certain amount of ground with its signal. And where the coverage of one tower stops, the next tower picks up. When there is no overlapping of such coverage by towers, you get cell phone coverage dead zones, such as in the woods and remote rural areas.
The signals emitted by these towers operate at predefined frequencies, which are also called as cellular frequencies, and usually referred to as bands. So each wireless carrier gets allocated (or leases) a certain frequency band within which it can operate. So no two wireless carrier will have the same bands. Traditionally, for the older 3G and the existing 4G LTE technologies, carriers used frequency bands in the MHz range. But with 5G, carriers are using GHz bands. And even in the GHz range, there are multiple bands and technologies.
One thing to note here is that lower the frequency of these signals, higher is the geographical coverage, but lower is the downlink speeds. Which means a signal in the 1–3 MHz band can cover more geographical distance, which means you’ll get a signal or coverage even there the nearest tower is comparatively farther away from you. But your data speed will not be something you’ll be happy with. But when you jump to the GHz bands, the geographical coverage will not be as much as the MHz bands, but you’ll have higher downlink speeds. What this means is that wireless carriers will need more towers and in closer proximity to each other to cover the same amount of geographical area, but they’ll be able to offer better data download speeds.
The 5G technology that we’re all so excited about starts in the GHz bands. Some companies are using sub-1GHz bands and there are some companies which are using higher frequency bands. All the bands that operate at a frequency lower than 6GHz are called Sub-6 bands.
Sprint, one of the very first wireless carriers in the US to deploy 5G networks is using the 2.5GHz band. So it is able to cover more geographical area than it’s competitors, but is not able to match the download speeds of it’s competitors, who are using higher frequency bands. So the wireless carriers need to strike a balance between the downlink speed and coverage.
Next, some wireless carriers are using very high frequency bands, which are over 24GHz. As you can now imagine, these signals will be covering very less geographical area, but they’ll be able to provide some of the best downlink speeds imaginable. These are called the Millimeter Wave bands. Right now, wireless carriers are deploying these small emitters or towers on light posts, or over buildings, which are able to server a small area, but are able to provide high speeds. If you have watched any YouTube video demonstrating the awesome download speeds on a 5G network, you’d have seen the person standing right next to a pole. That’s because the person will be using the mmWave signal coming off of the antenna deployed on that pole.
The illustration below by Android Authority gives a visual idea about the geographical coverage of the mmWave, Sub-6 bands, and the LTE networks. Also, we can see the number of antennas or tower we’d need for each technology.
To summarise, a sub-6 band 5G technology will be able to cover a larger geographical area for 5G coverage, but will not able to provide higher speed downlink. But an mmWave 5G technology will be able to provide class leading downlink speeds, but at the cost of less geographical area coverage. Now you know the difference and will be able to understand the network strategy of your carrier when you decide to switch over to 5G.
There are a lot more things about 5G which you need to understand when you’re deciding about 5G. But with the information you got here, you have the basics to start your own research and understand this future of cellular connectivity more easily.
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