What are cells in mobile communications?

You may wonder why the word “cell” is used in the context of mobile communications. A mobile network consists of many inter-connected coverage zones created by the transmission of signals from cellular towers. Cellular towers, also known as radio base stations, are part of a mobile network owned by a mobile network operator – MNO. The radio base station is responsible for communicating with the mobile phone and is a part of a mobile operator’s radio network. In this post, we will dive into some of the basic questions around cells and cellphones.

What is a cell in mobile wireless?

A cell in mobile communications is a geographical area covered by radio signals from a nearby cellular base station. The radio signals are sent by the base station at certain frequencies, and transmission power to be received by our mobile phones. When a mobile phone is in an area covered by a base station, it can transmit radio signals to the base station at frequencies allocated by the base station. So basically, a cell is just a geographical range within which the communication between a base station and a mobile phone can occur through radio waves. The base stations transmit and receive the radio signals at certain frequencies within a well-defined range, and the mobile phones within this range do the same for two-way communication.

Why a mobile is called a cell phone?

A mobile phone is often referred to as a cell phone because it employs cellular technologies such as GSM, UMTS, cdmaOne, CDMA2000, LTE and NR to communicate with other phones. From a terminologies viewpoint, the term cell phone is mostly used in the US and countries that follow the US terminologies. However, in the UK and many parts of Europe, the term mobile phone is used for referring to cellular phones.

Which types of cells are used in mobile communication?

There are various types of cells used in mobile communication, including macrocells, microcells, femtocells and picocells. The cells are differentiated in this way based on the range they cover and the capacity they have. Macrocells have the longest range, whereas femtocells have the shortest range. Therefore, macrocells are more suitable for rural areas where coverage is required over a much larger area. Have a look at our dedicated post on small cells to learn about femtocells and picocells.

Cell TypeCell range
MacrocellsTens of kilometres
MicrocellsUp to 2 kilometres
PicocellsUp to 200 metres
FemtocellsUp to 10 metres

Types of cells in mobile networks

What is a cluster in mobile communication?

A cluster in mobile communications refers to a group of cells. The term cluster is used in cell planning where RF engineers have to ensure that the available frequency channels (e.g. ARFCN, UARFCN, EARFCN) are allocated to cells in a way that minimises any potential interference. If any two adjacent cells get allocated the same frequency channel that can lead to interference. If any two adjacent cells are allocated adjacent frequency channels e.g. ARFCN # 1 and ARFCN # 2, that can also lead to a type of interference called adjacent-channel interference.

cells for cell phones and mobile phones
Example of a cluster of cells

What is the difference between ARFCN, UARFCN and EARFCN?

ARFCN stands for Absolute Radio Frequency Channel Number, and it is a range of frequency channels available in the GSM networks. ARFCNs have numbers allocated to them, and each ARFCN represents a pair of frequencies, one for transmission and one for the reception when different frequency bands are used for uplink and downlink (Frequency Divison Duplex – FDD). UARFCN or UTRA ARFCN refers to the ARFCN in 3G UMTS networks, whereas EARFCN or Evolved-UTRA ARFCN refers to ARFCN in 4G LTE networks. Have a look at our dedicated post on GSM frequencies to understand how ARFCNs are allocated. To learn more about FDD and how it is used in 4G LTE networks, check out our post on Duplex schemes for LTE networks.

What is handoff in mobile communication?

A handoff, also known as a handover, is when a voice call or data session is transferred from one serving cell to another. A handoff happens when you start a call or a data session in a certain location, and then during the session, you move out of the area such that the cell that was serving you cannot reach you any longer. In that case, the serving cell will hand over the responsibilities of handling your session to another nearby cell better situated to serve you. For example, if you sit on a train from London Heathrow airport to central London and start watching a YouTube video (assuming you are using mobile data and not WiFi), your data session will keep getting handed over from one cell to another as you move from one location to another.

What is the difference between a macro cell and a micro cell?

Macrocells are the large or regular cells that provide the main mobile network coverage in your area. These cells usually have their antennas mounted at the top of tall masts on the ground, rooftops of high-rise buildings and other similar locations. Macrocells have a range of tens of kilometres, and they need to be mounted at a height from where they have a (mostly) clear view of the area they are serving. These cells require dedicated sites with adequate power supply, and usually, the operator pays rental fees for these sites. Macrocells form the main layer of cellular coverage within a geographical area. Microcells are a type of small cells that are low-powered cellular base stations. They are the biggest of the small cells with a range of up to 2 kilometres. Microcells can add capacity and coverage to the existing mobile network alongside macrocells, picocells and femtocells. Due to the area they can cover, microcells can be a good solution for areas like large train stations and address temporary capacity needs for any sporting events, concerts, etc.

Which cell is used to cover remote or sparsely populated areas?

Macrocells are used in those geographical areas where the main challenge is network coverage and not network capacity. When a mobile operator serves a town or village where the population density is low (fewer people per square kilometre), they need fewer cells per square kilometre. On the contrary, if a mobile operator serves a densely populated area, they need a higher number of cells per square kilometre. Macrocells are ideal for rural and sparsely populated areas such as remote villages and towns, which may have a large land area, but the population size is small. Macrocells have high transmission and reception power, giving them a large range to provide primary network coverage to vast geographical areas. Macrocells are more suitable to serve rural areas where the traffic load on the mobile network is not as high as that in heavily populated cities. Macrocells are installed, operated, controlled and managed by the mobile operator and use a licensed frequency spectrum. Multiple macrocells can originate from the same base station of a cell site.

Which cells are used for densely populated areas?

In densely populated areas such as central London, with thousands of people per square kilometre, there is a massive demand on a mobile network to ensure that everyone can access the network, get enough bandwidth/bit rates, and have no coverage gaps. In urban areas, many users try to access the network simultaneously for voice calls, web browsing, video streaming etc. which increases the demand on network capacity. Urban areas also have coverage challenges with too many obstacles such as large buildings, brick walls, elevators, underground train stations, interference from WiFi/WLAN signals, reflective surfaces to name a few. In these densely populated areas, a mobile operator can use smaller, more targeted cells, e.g. microcells and picocells, to fill the coverage and capacity gaps. Microcells are an extension of the primary cellular network, which consists of macrocells. Microcells are controlled and managed by the mobile operators themselves. The key considerations for deploying microcells include the connectivity to the mobile core network, the frequency spectrum and the power supply.

Conclusion

A cell in mobile communications refers to the coverage zone created by the cellular towers within a mobile network. The signals coming out of the cellular towers can travel long distances, but as they move forward through the air, they keep on losing strength and eventually stop moving. The range within which radio signals from a base station travel define the boundaries of a cell. In other words, a cell is a coverage area created by the emission of radio waves from the base station within a geographical location. The inter-connected existence of cells throughout a country allows an operator to keep us connected even when we are on the move.

Here are some helpful downloads

Thank you for reading this post, I hope it helped you in developing a better understanding of cellular networks. But 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 challenges given 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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