What is a frequency spectrum in mobile communications?

We see mobile operators engaged in discussions around the frequency spectrum every few years. 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 roll out 4G LTE services in the UK.

A frequency spectrum in mobile communications is the range of radio frequencies allocated to each mobile network operator (MNO) in their country of operation for transmitting and receiving their RF signals. An MNO can add more cells with more spectrum to improve network capacity and coverage.

What does a frequency spectrum mean to a mobile operator?

A frequency spectrum defines the frequency bands in a particular range (e.g. 3.4 to 3.8 GHz) allocated to each mobile operator in a country to offer cellular services to their customers. The frequency bands require the mobile network operator (MNO) to get a license from local regulatory authorities.

The frequency spectrum is one of the most precious resources for any mobile network operator and is the lifeblood of a mobile network. The provision of cellular services in high-quality requires the frequencies to be allocated and managed correctly. 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. Mobile operators use the available frequencies to connect our mobile phones to the mobile network. To use these frequencies for transmission and reception of mobile signals, mobile operators acquire licenses from local regulatory bodies, for example, Ofcom in the UK.

An example of a frequency spectrum could be 3.4 GHz to 3.8 GHz, which can be used for 5G cellular services. A mobile operator in a country can get a portion of this frequency spectrum to launch their services. The frequency spectrum is for the radio access network, so only mobile network operators (MNO) buy it, not MVNOs. I have written a dedicated post on the difference between MNOs and MVNOs, which I encourage you to check out if you are unclear.

Difference between spectrum, band, carrier and bandwidth

A frequency spectrum is a range of frequencies, e.g. 2500 to 2900 MHz. A frequency band is essentially the same, e.g. a 2500 MHz band. A carrier is a sub-band or a channel, and its size or width is called the bandwidth, e.g. a channel from 2500 to 2505 MHz will have a bandwidth of 5 MHz.

The terms frequency, spectrum, band, carrier and bandwidth can be a bit confusing, especially when used interchangeably. Frequency is expressed in Hertz and is the number of cycles per second. Mobile networks use radio communication which is carried out on a range of frequencies. These frequencies can range from 850 MegaHertz (MHz) to tens of GigaHertz (GHz). 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 the mobile network 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. Operator B, in this example, may decide to buy a bandwidth of 80 MHz to get 3520 MHz to 3600 MHz.

In real life, mobile operators 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.

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 whereas in 3G UMTS networks the standard channel bandwidth is 5 MHz.

How mobile operators use the frequency spectrum

The frequency spectrum is used by the radio access network that includes cell towers within the cell sites of a mobile operator. The radio network is responsible for all the radio communication that enables the transmission and reception of mobile signals between the cell phone and the cell tower.

If we take a real-life example, most mobile network operators (MNO) in the UK use the 3400 – 3800 MHz (3.4 GHz – 3.8 GHz) frequency band for providing 5G (fifth-generation) cellular services. So, the mobile operators in the UK, e.g. Vodafone, EE, O2 and Three, can purchase portions of the 3.4-3.8 GHz spectrum from the UK regulatory authority, Ofcom.

If a mobile operator in the UK decides to use a total bandwidth of, for example, 100 MHz, they may get allocated a 100 MHz portion of the 3400 MHz – 3800 MHz. The operator can then employ the 100 MHz bandwidth to create channels of various sizes, e.g. 20 MHz and then use and reuse those channels throughout the country to provide 5G cellular coverage.

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

Who owns the frequency spectrum?

The frequency spectrum in a country is owned and managed by the government. The regulatory authorities within the country are responsible for issuing licenses to communication service providers such as mobile network operators who use their allocated frequency bands for radio signal communication.

Mobile network operators (MNO) may get the licenses awarded by paying the license fee to the local regulatory authorities. Mobile operators then use the frequency bands for the transmission and reception of radio signals for their cellular services. Mobile operators use sub-frequency bands (channels) within their allocated frequency bands and assign these to their radio base stations (cell towers). These base stations are nodes like Node B in 3G, eNodeB in 4G and gNodeB in 5G.

What are spectrum licenses?

The majority of the frequency bands for mobile communications are regulated and require mobile operators to purchase licenses from the government authorities before they can use them. The licenses are not limited to mobile communications and apply to all telecom services, including TV and radio.

In the UK, the regulatory authority that manages the frequency spectrum licenses is called Ofcom. All licensed frequencies require service providers, like mobile network operators, TV companies, radio stations etc., to purchase licenses from Ofcom for the transmission of their signals. For example, if a mobile operator wants to launch 5G services in the UK, they need to get a license for 5G 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 as well as unlicensed frequency bands.

What frequencies are used by mobile networks?

A mobile network can use a range of frequencies for different cellular technologies. Mobile operators run multiple cellular technologies such as GSM, IS-95, CDMA2000, UMTS, LTE and NR for 2G, 3G, 4G and 5G services. All cellular technologies use a predefined range of radio frequencies. There is no single frequency band that applies to all mobile networks, but a range of frequency bands can be used for different mobile technologies (e.g. GSM, UMTS, LTE) and various geographical regions.

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. 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. I have written dedicated posts on frequency bands for GSM networks and 3G UMTS networks. If you are from a country that uses CDMA technologies, you may check out this dedicated post on IS-95 (cdmaOne) frequencies.

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 extra support, especially when preparing for a new job, studying a new topic, or 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 you 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 the product overview and product roadmap.

Scroll to Top