Always look on the bright side of Light, I meant Spectrum
What do we need Spectrum for?
Well, today apparently almost everything. Order food, buy a ticket to a show or do our daily 2 Kms worth of browsing on social networks. It doesn’t matter if we are using WiFi, 4G or 5G. If it is wireless communication, there is a radio signal carrying our uber eats request. These radio signals are electromagnetic waves, such as gamma rays, X-rays, infra-red, and microwaves. As explained by Neil deGrasse Tyson, it’s all light!
So, my smartphone uses X-rays? Isn’t it dangerous?
Yes, X-rays are dangerous and no, our smartphones don’t use them. As shown in Figure 1, we only use a very small subset of electromagnetic wavelengths in our wireless communications, i.e., frequencies typically below 6 GHz. The reason we don’t usually go above 6GHz is related to the increase of path loss with frequency, meaning radio signals sent in higher frequencies will have higher attenuation from the absorption by the water molecules (H2O) present in the air. In short, the higher the frequency the shorter its coverage range. Additionally, while lower frequencies are able to penetrate walls relatively well, higher frequencies are reflected, thus reducing indoor coverage.
Many of the wireless technologies used in Internet of Things (IoT) related use cases, such as SigFox, ZigBee, Lora, NB-IoT and LTE-M, use sensors that send very little amounts of data on periodic intervals. These sensors can be installed in remote locations or in deep indoor environments, requiring a very robust coverage level (think of smart metres). It is no surprise that most wireless technologies, especially the ones related to machine-to-machine communication, operate at lower frequencies.
Why don’t we just use lower frequencies then?
It is not an easy task to harmonise all the different applications and industries which rely on wireless communication to operate. Frequency band allocation is the responsibility of National Regulatory Authorities (NRAs), which oversee and manage the spectrum usage and leasing. Ubiwhere developed the web-based platform used in the 5G auctions conducted by the Portuguese regulator ANACOM, where the Mobile Network Operators (MNOs) bid for 5G frequency bands, paying a total amount of over 566,802 million euros to the Portuguese Government, for the spectrum licences. NRAs play a critical role and this is easily observable in a recent case where the frequencies used in the airline industry can be considered as “neighbours” to some bands that were recently allocated to the telecommunication industry, for the 5G rollout. Such interference could put human lives at risk and in fact, the Federal Aviation Administration (FAA) released several statements concerning possible interference between 5G transmitters operating in the mid-band (3.5GHz) and the aeroplane’s radio altimeters which operate in a similar frequency. How is it possible for 5G to use frequency bands that are close to other critical systems, you may ask. In short, the spectrum allocations in the lower frequencies look like this:
According to GSMA’s Global Economy Report, mobile data will more than triple in most regions over the next six years, driven by increasing smartphone adoption and video usage.
How can wireless networks keep up with this demand if the spectrum is such a scarce resource? Coverage vs Capacity
Being able to use lower frequency bands helps us cover a wider area, however, depending on population density, this can turn into a challenge. Covering a wide area in a dense urban environment might ultimately result in a poor quality of service since the limited resources will be split by many concurrent users. Imagine having to split a regular size pizza between 100 people. This will result in many unhappy customers. The opposite is also not ideal, since having huge capacity but only in a short area where almost nobody lives is a waste of resources, or in other words, a bad investment. We have to be smart when using the available frequency bands and this is something that MNOs are very good at. The typical frequency distribution and usage are highlighted in figure 3, with frequencies bands below 1 GHz targeting deep indoor and rural areas, mid bands offering a balanced tradeoff between coverage and capacity, high-bands, also referred to as “mmWaves”, focusing on hotspots with a high concentration of people and devices.
The bands above 6GHz have a very limited range, but at the same time have the largest bandwidth available, i.e., increased capacity. Going back to the previous pizza analogy, mmWave pizza is significantly larger when compared with the low and mid-bands pizza sizes. However, the pathloss is so severe that if we do as little as a turn during a video call and our body blocks the Line of Sight (LoS) between our device and the antenna, the connection can be severely compromised. The attenuation caused by our body (which is made by 70% of water) is also known as body loss and is accounted for, in the link budget.
Technologies such as beamforming can help to overcome the challenges of using mmWave but the way radio equipment is deployed close to the end-user needs to be carefully planned. Integrating what is oftentimes not visually appealing hardware while still preserving the city architecture is not an easy task. With this in mind, Ubiwhere has products such as the SmartLamppost and the Urban Platform, which allow for Infrastructure owners like Municipalities to onboard different installations — EV charging, radio equipment, CCTV cameras and local processing units, just to name a few — while also providing a neutral hosting platform that allows the management of leasing agreements with multiple incumbents. Ubiwhere strongly believes in the concept of infrastructure sharing and neutral hosting to be essential in building more efficient, interoperable and inclusive cities, where regardless of the provider or the technology, the focus is on serving who lives, works and visits the city, as best as possible.
References
https://www.gsma.com/mobileeconomy/wp-content/uploads/2022/02/280222-The-Mobile-Economy-2022.pdf
