What are small cells in telecom?

Small cells have been a hot topic in the mobile communications industry for many years. Mobile operators often use small cells as a way to extend their network coverage. However, small cells are not just about the additional coverage; they can also allow mobile operators to offer additional capacity to their customers. So what exactly are small cells then? If you follow the mobile communications industry, then you may have come across terminologies like femtocells, picocells and microcells before. Small cells in mobile communications represent all the different types of cells, including femtocells, picocells, microcells and others. The terms femto, pico, micro, and others indicate the size or range of the cell in question.

What is a small cell?

Small cell is a terminology that refers to a range of small, low-powered cell sites that can provide targeted 2G, 3G, 4G and 5G cellular coverage to customers in smaller geographical areas like homes, offices and shopping malls etc. The most popular types of small cells are femtocells with a range of up to 10 metres and picocells with a range of up to 200 metres. The regular cells in mobile networks are called macrocells that can cover tens of kilometres.

How do small cells work?

Small cells work in the same way as the regular cells (macrocells) in terms of the overall mobile network connectivity, however, at a much smaller scale. Like macrocells, small cells are also part of the mobile radio network and require connectivity to the mobile core network through a backhaul connection. The backhaul connection for small cells provides a means for them to communicate with the rest of the mobile network through the mobile core network. The deployment methods for small cells vary depending on their type. Femtocells that arguably represent the simplest type of small cells require a power supply and connectivity to the internet to work. The internet acts as a backhaul connection for a femtocell to connect it to the rest of the mobile network for providing indoor cellular coverage within a home or small office. The other bigger cells, picocells, are better suited for slightly larger areas, e.g. shopping malls, and require professional installation with a dedicated power supply and backhaul connectivity.  

What is a small cell backhaul?

In small cells, the backhaul is the connection between the small cell base station (e.g. femtocell, picocell, microcell) and the mobile core network. For femtocells, the backhaul can be a simple fibre or DSL connection to the broadband router. However, for picocells and microcells, the backhaul is a dedicated connection that can ordinarily use a fibre cable or a wireless link.

What are the different types of small cells?

There are at least three types of small cells, including microcells, picocells and femtocells. Microcells are the biggest of the small cells as they can cover up to 2 kilometres and have been around for years as a key part of an overall mobile network fully controlled by the mobile operator. In most small cell discussions, you are likely to find femtocells and picocells frequently because they are more specific regarding the use cases they target and the strategic value they provide to a mobile operator. Picocells can cover up to 200 metres and can be used in shopping malls and large offices. Femtocells are the smallest of the small cells, and mobile operators can offer them directly to consumers as “signal boosters”.

Small CellRangeUse case examples
FemtocellUp to 10 metresSmall office or home
PicocellUp to 200 metresShopping malls or large offices
MicrocellUp to 2 kilometresStreets, train stations, densely populated buildings

—Small cell types and range—

What is a femtocell?

Femtocells are the smallest of the small cells and are often used by mobile operators as “signal boosters”. They are easy to install and operate and can be managed directly by the customers. Femtocells are owned by mobile operators but can be sent directly to the customers to address coverage issues within their homes or office. Femtocells form part of the main network of a mobile operator, and they have a range of up to 10 meters. Mobile operators market their femtocells with customer-friendly and easy to understand names such as coverage booster or signal booster.

The value that femtocells bring is that these can be installed and managed directly by a customer rather than the operator. Femtocells are usually available as a plug-and-play offering and require users to plug them into a power socket and connect to the home Internet (LAN/Wi-Fi router). Once connected to the Internet, the femtocells can communicate with the mobile operator’s core network via a gateway. Just like other small cells, femtocells provide coverage as well as additional capacity to mobile users.

What Is A Picocell?

Picocells are small cells with a coverage range of up to 200 metres. They are little powerhouses for mobile operators as they can act as strong mini-base stations to provide additional capacity and coverage to customers. Picocells can be used within buildings such as shopping malls and office sites to fill any coverage and/or capacity gaps. They are controlled and managed by mobile operators and require a proper location or site to be mounted, connected to the power supply, and provided with backhaul connectivity. Like any other regular cell site, picocells also have associated operational costs such as site rent, electricity, etc. They are a perfect solution in situations where targeted coverage is needed in a rather small area with a high number of mobile users, e.g. shopping malls, train stations, office sites, etc. In such areas, many people make and receive phone calls, send messages, use apps and other internet services on their mobile phones. In other words, picocells are just smaller base stations used by operators as an additional layer of cells to provide targeted coverage in areas where the macro network cannot fully reach. They need to be mounted properly and require a dedicated power supply and connectivity to the mobile core network. 

What Is A microcell?

Microcells are small cells that cover a much larger geographical area compared to femtocells and picocells. 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 other cells. Based on the range of microcells (up to 2 km), they can be a good solution for areas like large train stations. They can also address temporary capacity needs for large public gatherings like sporting events, concerts, etc. The macrocells still provide the primary network coverage in any mobile network, but microcells can be an extension of the main network to fill coverage and capacity gaps. Microcells are controlled and managed by the mobile operators themselves.

Why do we have small cells?

Small cells are useful for mobile phone users because they can provide cellular coverage in areas where there are coverage gaps. They can also provide additional capacity, which for customers means extra bandwidth. For example, if you are in a large shopping mall with lots of people using the same mobile network as you, the network capacity that the mobile operator can offer you may get shared with other users. With a picocell, a mobile operator can provide additional capacity to have enough bandwidth for everyone. Customers can use femtocells as signal boosters if they have areas within their homes with poor cellular coverage.

What are the advantages of small cells for mobile operators?

Small cells are also important to mobile operators as they allow them to offload some of the traffic from their main network (macrocells), especially during busy hours, so that better quality of service (QoS) can be provided to the customers. Places with large public gatherings such as offices, shopping malls, and stadia usually require more capacity because many users at these sites try to access the internet from their mobile phones simultaneously. Network traffic generated by these users can be offloaded to small cells. In addition, mobile operators use femtocells as a low-cost solution to fix coverage issues in smaller areas.

Is a small cell the same as 5G?

Small cells and 5G are not the same things. 5G is a cellular technology, whereas small cells are types of cells (coverage zones) that can be used within 5G, 4G, 3G and 2G mobile networks. 5G or the fifth generation of mobile networks can operate at high, medium and low frequencies to connect devices in small and wide areas. When higher frequency bands are used in the 5G networks, e.g. 28 GHz band, they can provide highly targeted coverage in a smaller area because higher frequencies cannot travel too far. However, 5G can also support sub 1 GHz frequencies (e.g. 600 MHz and 700 MHz), which are wide-area frequencies and not limited to smaller areas. Therefore, the higher frequency bands within 5G will work in a small cell set-up, but that does not mean that 5G is limited to small cells or that small cells are limited to 5G.

How far can a small cell cover?

Small cells can cover from 10 metres to up to 2 kilometres. The smallest small cells, femtocells, can cover up to 10 metres, whereas picocells can cover up to 200 metres. Microcells are also a type of small cells, and they can cover a radius of up to 2 kilometres.

Type of small cellArea covered
FemtocellUp to 10 metres
PicocellUp to 200 metres
MicrocellUp to 2 kilometres

–Coverage area for small cells—

Are there any drawbacks of using small cells?

While small cells mostly provide benefits, there are few areas where they can be challenged. There are two key reasons for deploying small cells; coverage and capacity. In terms of extended coverage, the value small cells bring to the table is not different from what a low-cost repeater can offer. It is the additional capacity part that makes small cells more superior to repeaters. That is certainly true for picocells and microcells where a dedicated backhaul is provided. However, with signal boosters (femtocells), where a customer is expected to use their internet as a backhaul, the maximum bandwidth they get on the cell phone is limited to their internet speed. It means that the value femtocells offer in such a scenario is mainly voice calls and SMS because, for any data usage, the customer is better off using their internet directly.

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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