What are small cells in telecom?

Small cells have been a hot topic in the mobile communications industry for a number of years. Mobile operators often use small cells as a way to extend their network coverage. 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?

Small cells are small base stations or mini-cell sites controlled by mobile operators to provide targetted coverage in places where the standard network coverage is poor. Small cells cover smaller areas ranging from 10m to 1Km or more. They also provide additional capacity to offload network traffic from the larger cells. The larger cells are called macrocells and their range is in tens of kilometres.

If you follow the mobile communications industry then you may have come across terminologies like femtocells, picocells and microcells before. Small Cells is an umbrella terminology as pointed out by GSMA Small Cell Deployment Booklet. 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.

Femtocells

Femtocells are owned by mobile operators but can be used by customers in their homes or small offices to address coverage issues. They are easy to install and operate and can be managed directly by the customers. Femtocells form part of the main network of a mobile operator, and they need to be purchased from the mobile operator. They have a range of up to 10 meters and 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 a user 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 core network of the mobile operator via a gateway. Just like other small cells, femtocells provide coverage as well as additional capacity to mobile users.

Picocells

Picocells can be used within buildings such as shopping malls and office sites to address coverage gaps and provide additional capacity to the mobile users. They have a range of up to 200 metres, and they can provide coverage over a larger area as compared to femtocells. 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. 

Picocells act as little powerhouses for operators as they are mini-base stations which can provide additional coverage and capacity in areas that have a higher concentration of mobile users. They are controlled and managed by mobile operators and require a proper location or site where they can be mounted, connected to the power supply, and provided with backhaul connectivity to connect them to the operator’s core network. Just like any other cell sites, 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, lots of people make and receive phone calls, send messages, use apps and other internet services on their mobile phones.

Microcells

Microcells are also a type of small cells but they have a much larger range as 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 be used for addressing temporary capacity needs for large public gatherings like sporting events, concerts, etc.

The primary network coverage is still provided by the macrocells 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.

How do small cells work?

Small cells are essentially low-powered radio base stations that form part of a mobile operator’s radio network. Just like the main radio network, small cells can create 2G, 3G and 4G connectivity using GSM, UMTS and LTE technologies. The implementation methods for small cells vary depending on their type. The backhaul part of the small cell provides the means for connecting it to the rest of the mobile network. The implementation of a femtocell can be as simple as connecting it to a power supply and a broadband connection in an indoor environment. Picocells and microcells, on the other hand, need to be mounted outdoors and require proper power cabling and backhaul connectivity. The key considerations for microcells and picocells include the connectivity to the mobile core network, the frequency spectrum and the power supply.

Small cells are also of strategic importance to the mobile operators as they allow them to offload some of the network traffic from their primary (macro) network to these mini-sites in busy hours. Places with large public gatherings such as offices, shopping malls, and stadia usually require more capacity because lots of 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.

Have a look at our book Mobile Networks Made Easy on Amazon for information on this and other similar topics.

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