What is a frequency spectrum in mobile communications?

Every few years, we see mobile operators engaged in discussions around the frequency spectrum. But, do you sometimes wonder what they are talking about and, more importantly, why they are talking about it? Regulatory authorities such as Ofcom in the UK are also involved in these discussions. If you follow UK technology news, you may recall 2013 when Ofcom was auctioning for the 4G mobile spectrum, which key players in the UK, including EE, Vodafone, Telefónica UK, Hutchison 3G and Niche Spectrum Ventures, ended up winning. That win allowed these players to be able to roll out 4G LTE services in the UK.

What is a frequency spectrum?

A spectrum or frequency spectrum in mobile communications is the frequency band allocated to mobile operators, which they can use to launch mobile cellular services. Mobile operators use the frequency spectrum to connect us to the mobile network. The connection between the mobile phone and the cellular towers takes place using the frequencies allocated to the mobile operator as part of the overall frequency spectrum they get. So a frequency spectrum is just a range of frequencies. An example of a frequency spectrum could be 3.4GHz to 3.8 GHz, which can be used for 5G cellular services. A mobile operator in a country can get some portion of this frequency spectrum to launch their services.

What is a spectrum in a cellular network?

The frequency spectrum is one of the most precious resources of any cellular network operator. It is the only way for the operators to roll out mobile services in any location. The frequency spectrum defines the frequency bands allocated to each mobile operator in a country to provide mobile services to their customers. These frequency bands are licensed and require mobile operators to get the license from a regulatory body. The frequency spectrum is the lifeblood of a mobile network. The provision of mobile services in high-quality requires the frequencies to be allocated and controlled properly. Improper use of the frequency channels can lead to severe degradation of services due to interference. For mobile operators, the frequency spectrum needs to be planned well and used efficiently to ensure good Quality of Service (QoS) for their customers.

Who owns the spectrum?

The frequency spectrum in any country is owned and managed by the government. The regulators within specific countries are responsible for issuing licenses to communication service providers such as mobile operators to use the frequency bands within their allocated frequency spectrum. Mobile operators can then use the frequency bands for the transmission and reception of their mobile services. Mobile operators use sub-frequency bands (channels) within their allocated frequency bands and assign these to their radio network resources. So basically, when your mobile phone communicates with your nearest Base Station, it uses one of these frequency channels.

What are spectrum licenses?

The frequencies that require the government’s permission for their use in a country require a mobile operator to get a license from the regulatory authority. In the UK, this regulatory authority is called Ofcom. The licensing is not limited to mobile communications only but applies to all telecom services, including TV, radio and other such services. For example, if a mobile operator wants to launch 5G services in the UK, they need to get a license for 5G compatible frequencies from Ofcom. However, not all frequency bands require a license, e.g. Wi-Fi, walkie-talkies, and baby monitors typically use frequency bands that are license-free or unlicensed. 5G networks can use licensed and unlicensed frequency bands, as explained in this post.

What is mobile network frequency?

A mobile network can use a range of different frequencies for different services. Mobile operators run multiple cellular technologies such as 2G, 3G, 4G and 5G to connect their customers to the network. All of these technologies use a predefined range of frequencies. For example, in Europe, 2G GSM networks can use a frequency band from 890 MHz to 960 MHz, but other GSM-compatible frequency bands are also possible. Likewise, 3G UMTS networks can use 1920 MHz to 2170 MHz in Europe, but other frequencies bands, including 850 MHz, 900 MHz, and 1700 MHz, are also possible. The key point here is that there is no single frequency band for mobile networks, and a range of frequency bands can be used for different mobile technologies (e.g. GSM, UMTS, LTE) and different geographical regions.

What is the difference between frequency, spectrum, band, and carrier?

Let’s get the terminologies right. The terms frequency, spectrum, band, and carrier can be confusing, especially when used interchangeably. Frequency is expressed in Hertz and is the number of cycles per second. Mobile networks use frequencies from 850 MegaHertz (MHz) to tens of GigaHertz (GHz). Mobile networks use radio communication which is carried out on a range of frequencies. A spectrum or frequency spectrum is a range of frequencies that are available for any given service. For example, a regulatory authority in a country can have 3400 MHz to 3600 MHz of total frequency spectrum available, which they can sell to different mobile operators. Let’s say the regulatory authority makes two portions of this spectrum to sell to mobile operators A and B. Operator A, in this example, buys a bandwidth of 100 MHz, so they get the 3400-3500 MHz, frequency band. On the other hand, operator B decides to buy a bandwidth of 80 MHz and get 3520 MHz to 3600 MHz. In real life, what operators actually do is that they divide the total purchased bandwidth into multiple frequency channels of smaller bandwidths, e.g. 10 MHz or 20 MHz etc. These frequency channels are also known as carriers and are used for establishing a connection between a mobile phone and the mobile network.

Is spectrum a bandwidth?

Theoretically speaking, any range of frequencies can have a bandwidth because a range always has a start and finish. But in the context of mobile communications, a frequency spectrum and bandwidth are two different things. A frequency spectrum, as explained above, is an overall range of frequencies within which multiple frequency bands can be created. On the other hand, the bandwidth in mobile communications refers to the total width of a frequency channel allocated to a mobile phone user for cellular services. Usually, in 4G networks, it is common to see channel bandwidths of 20 MHz.

What is the use of frequency spectrum?

The frequency spectrum is used for all radio communication between the cell phone and the mobile network. For example, most 5G cellular service providers use the 3400 – 3800 MHz (3.4 GHz – 3.8 GHz) frequency band in the UK. Different mobile operators in the UK can purchase portions of this spectrum from the regulatory authority Ofcom. In the same example, let’s say a certain UK mobile operator decides to buy 100 MHz (3400 MHz to 3500 MHz). That way, the operator can use this 100 MHz bandwidth to create channels of various sizes, e.g. 20 MHz and then use them and reuse them throughout the country to have nationwide coverage.

Visual representation of communication between a mobile network and a mobile phone

Conclusion

A frequency spectrum in mobile communications is the range of frequencies allocated to mobile operators for the transmission and reception of their mobile signals within their country of operation. The frequency spectrum available to a mobile operator can determine how good or bad their network coverage quality can potentially be. With more spectrum, a mobile operator can add more cells in any given area to add more capacity. However, just because a mobile operator has more spectrum than other operators does not automatically mean that they have a better service because the use of spectrum requires investment in radio networks also.

Here are some helpful downloads

Thank you for reading this post, I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need some extra support especially when preparing for a new job, or studying a new topic, or maybe just buying a new phone. Whatever you are trying to do, here are some downloads that can help you:

Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy which explains the network nodes e.g. BTS, MSC, GGSN etc.

Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience which is why I’ve carefully put together a few slides to get you started in no time. So if work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on product overview and product roadmap.

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