Small cells: What are microcells, femtocells and picocells?

Femtocells, picocells and microcells are types of small cells that complement the primary cellular coverage provided by the macrocells within a mobile network. The macrocells are the largest cells in mobile communications that cover tens of kilometres, whereas femtocells are the smallest cells.

Femtocells, picocells and microcells are small cells that allow a mobile operator to offer targeted cellular coverage in smaller areas to address network capacity and coverage issues. Femtocells cover a radius of up to 10 metres, picocells cover up to 200 metres, and microcells can cover up to 2 km.

Small cells have been a hot topic in the mobile communications industry for years. They mainly include femtocells, picocells and microcells that provide cellular coverage over smaller geographical locations. The terms femto, pico and micro indicate the size or range of the cell in question.

Mobile operators often use small cells to extend their network coverage. However, small cells are not just about the additional coverage (signal strength); they also allow mobile operators to offer additional capacity (bandwidth) to their customers.

What are small cells in mobile communications?

Small cells are low cost and low powered radio base stations that complement the primary cellular network of a mobile operator by providing targeted indoor and outdoor coverage to customers in smaller locations like homes, offices, shopping malls, train stations etc.

There are different types of small cells depending on the range, power consumption, form factor and use cases. The smallest type of small cell is a femtocell which is for indoor use, whereas the slightly larger type is called a picocell for indoor and outdoor use in urban and rural areas.

Among all small cells, femtocells have the shortest range, a radius of up to 10 metres. Picocells have a slightly longer range and cover a radius of up to 200 metres, whereas microcells can cover a radius of up to 2 kilometres. The regular cells in mobile networks are called macrocells that cover tens of kilometres.

Femtocells are the simplest and most user-friendly small cells that simply require a power supply and internet connectivity to start working. The internet acts as a backhaul connection that connects a femtocell to the rest of the mobile network for providing indoor coverage within a home or small office. The backhaul for femtocells can be a domestic internet connection, e.g. a fibre or DSL line through a broadband router.

Picocells are better suited for slightly larger areas, e.g. shopping malls, and require professional installation with a dedicated power supply and backhaul connectivity. The backhaul for picocells and microcells is a dedicated fibre or wireless link managed by the mobile operator just like a regular base station.

How do femtocells and picocells 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 macro cells, 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. It is the connection between the small cell base station (e.g. femtocell, picocell, microcell) and the mobile core network.

When a femtocell is connected to an internet backhaul, it communicates with an entity called a femtocell gateway which controls a large number of femtocells. The femtocell gateway connects femtocell to the relevant mobile core network entities for voice calls, SMS and mobile data.

All small cells are ultimately controlled by the mobile operator who provides them to their customers. Once connected to the backhaul, the small cell communicates with the rest of the mobile network owned and managed by the mobile operator.

A small cell only allows you to connect to the network of the mobile operator that deploys them. So, for example, if you get the “Sure Signal” product from Vodafone UK, which is a femtocell, it will only allow you to connect a phone with a Vodafone UK SIM card to the Vodafone UK’s mobile network.

Small cells work in the same way as regular base stations (cell towers) for a mobile phone. A mobile telephone sees small cells as traditional base stations, and all the cellular services, including voice calls, texts and mobile data, are available to the phone user in the same way.

When a customer is within range of a small cell, the phone automatically detects it to establish a connection. As small cells are low-powered base stations, the mobile phones that connect to them in idle or busy modes consume less power, which improves the phone’s battery life.

Small cells can support calls and sessions for simultaneous mobile phone users. While the range may vary depending on the small cell type and vendor, residential femtocells can generally accommodate 4 to 16 concurrent calls. In contrast, larger multi-band small cells can support up to 64 or more users.

With a femtocell, customers can also enable restricted access so that cellular connectivity is only available to permitted users. That can be achieved by creating a whitelist so that only people added to the whitelist can access cellular services, including voice calls, texts and data through the small cells.

Why are femtocells, picocells and microcells used?

Small cells are helpful for mobile network operators because they can provide cellular coverage in areas with coverage gaps. They can also provide additional capacity, which means additional bandwidth for customers.

Mobile operators employ small cells to primarily fix network coverage issues in geographical areas where the signals from the main network can’t reach. They sell femtocells to their customers as “signal boosters”, allowing customers to address any coverage holes in their homes. As a plug-n-play product, femtocells do not require any expensive RF planning, which reduces the operational costs for the mobile operator.

Small cells are valuable assets for mobile operators as they can offload some traffic from their main network (macrocells). The traffic offloading is especially useful during busy hours as it reduces the load on the main network, improving the overall Quality of Service (QoS) for 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. The network traffic generated by these users can be offloaded to small cells.

For example, if you are in a large shopping mall with lots of people using the same mobile network as you, the available network capacity may get shared with other users. By installing a picocell in that shopping mall, a mobile operator can provide extra capacity to ensure enough bandwidth for everyone.

Do 5G networks use a small cell architecture?

5G uses a cellular technology New Radio (NR), which is highly flexible and can operate at high, medium and low frequencies to connect different types of cellular devices to the same mobile network.

Higher radio frequencies generally have a shorter range, whereas lower frequencies provide more extensive coverage. The typical radius of a 5G NR cell is small, and it ranges from a few hundred metres to a few kilometres. The largest cell radius for 5G is 300 kilometres (186.4 miles).

The solutions for indoor 5G coverage benefit from small cells that use higher frequencies for higher throughput and lower latencies. 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.

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 also supports sub 1 GHz frequencies (e.g. 600 MHz and 700 MHz), which have a more extended range and are therefore wide-area frequencies.

What are the different types of small cells?

Femtocells, picocells and microcells are the types of small cells that allow 2G, 3G, 4G and 5G networks to provide secure communication in high-quality through licensed and unlicensed frequencies controlled by the mobile operator. The range of small cells is from 10 metres to 2 kilometres.

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

Generally, in the context of small cells, femtocells and picocells are the small cells mostly referred to due to the use cases they enable and the strategic value they offer to mobile operators. However, microcells are also part of the small cell family.

Microcells are the largest of the small cells, and they cover an area within a 2-kilometre radius. Microcells have been around for years as a critical part of mobile radio network deployment and are fully controlled by the mobile operator, just like the macrocells.

Type of small cellRange in metres / KmUse cases
FemtocellUp to 10 metresSmall office or home
PicocellUp to 200 metresShopping malls or large offices
MicrocellUp to 2 kilometresStreets, train stations, densely populated buildings

—Table showing femtocells, picocells, and microcells range and use cases—

Femtocells and picocells have a shorter range compared to microcells. Picocells cover up to 200 metres and can be used in shopping malls and large offices. Femtocells are the smallest of small cells with a range of up to 10 metres and are suitable for homes and small offices.

What is a femtocell?

Femtocells are the smallest 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 customer to address coverage issues within their homes or small offices.

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 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. Like other small cells, femtocells provide coverage and 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 a perfect solution in situations where targeted coverage is needed in a relatively small area with many mobile users, e.g. shopping malls, train stations, office sites, etc.

Many people make and receive phone calls, send messages, and use apps and other internet services on their mobile phones in such areas. In other words, picocells are 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 are controlled and managed by mobile operators and require a dedicated location or site where they can be mounted professionally. In addition, Picocells must be connected to the main power supply and fixed or wireless backhaul connection. Like any other cell site, picocells also have associated operational costs such as site rent, electricity, etc.

What Is A microcell?

Microcells are the largest small cells covering a much larger geographical area than femtocells and picocells. They have the most extensive range, which is about 2 kilometres. Microcells can add capacity and coverage to the mobile network alongside the macrocells.

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.

Are there any drawbacks to using small cells?

While small cells mainly provide benefits, there are few areas where they can be challenged.

Capacity and coverage are the two critical reasons for deploying small cells. In terms of extended coverage, the value small cells bring to the table is not different from what a low-cost repeater can offer. However, the additional capacity part makes small cells superior to repeaters.

However, with signal boosters (femtocells), where a customer is expected to use their own fixed 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. 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.

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