There are many aspects of smartphone technology that could be described in detail but for now, we’d like to introduce you to how smartphones use cellular frequencies.
What are cellular frequencies?
Cellular frequencies are the sets of frequency ranges that have been assigned for cellular compatible mobile devices, among which the most popular ones are obviously mobile phones. Tablets and laptops can also work on those frequencies if they have the appropriate functions.
The radio frequencies used for cellular networks may differ in some countries.
For example, when the first commercial standard was launched in the United States (more than two decades ago), it operated in the 800 MHz frequency band. Mobile networks and carriers in the United States now use 2 GSM bands, 3 UMTS bands, 12 LTE bands, and 3 CDMA bands.
The four major frequency bands in the U.S. are as follows:
- 698-806 MHz 700 MHz Band
- 806-849/851-896 MHz 800 MHz Band
- 1850-1910/1930-1990 MHz Personal Communications Systems (PCS) Band
- 1710–1755/2110–2155 MHz Advanced Wireless Services (AWS) Band
Their differences depend on the carrier. Various operators use different bands, T-Mobile often uses PCS or AWS bands, while Verizon goes with an 800 MHz band. What does it mean when some are 800 while others are over 2,000? In general, the lower frequencies provide coverage over a larger area, because they propagate farther in the environment, including inside buildings.
Contrasingly, the higher ones allow service to more customers in a smaller area because the frequencies are weakened or even stopped by obstacles such as buildings. However, lower frequencies tend to have relatively poor capacity capabilities and higher ones have greater capacity allowing more information to be carried.
It is not easy to describe one universal system. Dual-band, tri-band or quad-band are already outdated, as this technology is now over ten years old. Ultimately, the frequency bands supported are a function of the mobile communication standards supported. Now, smartphones try to support as many frequencies as possible. Unfortunately, it is not possible to support all of them, because it becomes too expensive for manufacturers. That’s why a device’s compatibility is determined by the region in which it is sold as well as any potential carrier partners.
The actual frequency used by a particular model of mobile phone can change from place to place because it varies based on the settings of the carrier’s base stations. Switching to another frequency range is unnoticeable because it happens automatically when you are moving with your smartphone, for example, while travelling in the car.
Users don’t usually know which band they are on as it isn’t important to them. Problems may occur when you look at this from the other side, if each carrier uses their own cell sites, there is no sharing allowed. This means that if your friend has a mobile phone on a different system and both of you are in the same place, one of you might have a stronger signal than the other.
What does GSM and CDMA mean?
There is also another typology of frequency bands in which two technologies dominate: GSM (Global System for Mobiles) and CDMA (Code Division Multiple Access). These two standards are entirely incompatible. Not all carriers using those technologies are equal.
A phone which goes well with CDMA may not work best on carrier X but might be perfect on carrier Y. When you check your reception you’ll be able to tell.
What is 3G, 4G, 5G and 6G?
Technologies are changing rapidly. There was 1G (1979), 2G (1991), 2G transitional
(2.5G, 2.75G), 3G (2001), 3G transitional (3.5G, 3.75G, 3.9G), now there’s 4G (2009), IMT Advanced (2013), 5G (2019) and IMT-2020 (under development).
There are already potential plans in place for 6G. The newer ones are replacing the former but even though they are still improving, for example, 3G and 4G are operating in similar frequency ranges when we compare them to the potential capabilities of 5G. We mentioned the U.S. above but for the rest of the world, the most common bands are named as 800 Mhz, 900 Mhz, 1700 Mhz, 1900 Mhz and 2100 MHz. Nowadays, the majority of phones need to be able to facilitate roaming, so they support multiple bands which are used in various countries. They‘re also known as multi-band phones.
The graph below shows ‘the progress in mobile cellular frequency ranges – from the first generation (1G) in the 1980s to the sixth generation (6G) that is predicted for the 2030s.’
These are approximate figures, which is why you can find many different typologies of them. The bands in GSM networks are as follows: 850 MHz, 900 MHz, 1800Mhz and 1900 MHz. In the U.S., mobile devices have dual-band capability which supports 850 MHz and 1900 MHz and if someone has that kind of mobile phone, it cannot be used in Europe, whereas 900 MHz and 1800 Mhz are supported.
In early 2019, the Federal Communications Commission (FCC) voted to unanimously clear “terahertz wave” (95 gigahertz to 3 terahertz) frequencies. This was cleared “for engineers to start experimenting [with] uses for the next generation of wireless technology — possibly 6G.” It is not yet clear how humanity will benefit from the use of such high frequencies. Although the FCC make no mention of 6G specifically in their press release, it is the inevitable successor to 5G (up to 86 GHz). The challenges of frequencies such as 5G and 6G is that they require the transmission of data over millimeter waves. The shorter wavelengths get, the less reliable connections are and the less likely they’ll be to penetrate structures such as walls etc.
Frequency bands are the most important for the carriers as they have to know how to provide service to an increasing number of customers. Their development is about supporting the best connection and transmission of data. As an average phone user, you won’t have to delve into the subject (unless you want to) but it is worth noting that your bad reception is probably coming from somewhere!
Is 5G dangerous?
As this post is about frequencies, we should probably try to answer this question. 5G is the fifth generation of wireless technology, so it’s important that we familiarise ourselves with it. Whether you like it or not, it is already being used in various parts of the world and several people have voiced their concerns, particularly online. At this stage, we cannot say for certain how it will affect us as human beings but taking precautions when it comes to the use of emerging technology is always a good idea.
Scientists have been attempting to research 5G for several years now, in studies such as ‘Human Exposure to mmWave Phased Array Antennas in Mobile Terminal for 5G Mobile System’, ‘Simulation of the Effect of 5G Cell Phone Radiation on Human Brain’ and ‘Efficient Computation of SAR and Temperature Rise Distributions in a Human Head at Wide Range of Frequencies Due to 5G RF Field Exposure.’
More than 100,091 signatories from at least 187 countries as of June 7, 2019 appealed to UN, WHO, EU, Council of Europe and governments of all nations for a 5G moratorium, warning of the potential serious health effects of 5G. They asked for a full investigation of the potential health effects of 5G, independent from industry, asserting that:
‘5G will substantially increase exposure to radio frequency electromagnetic fields (RF-EMF) on top of the 2G, 3G, 4G, WiFi, etc. telecommunications already in place. RF-EMF has been proven to be harmful for humans and the environment.’
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