Small Cell Installations: Microcell, Metrocell, Picocell, Femtocell for AT&T, Verizon, T-Mobile, Sprint Coverage

The table below compares the key characteristics of four types of residential or commercial small cell installations - Microcell, Metrocell, Picocell, Femtocell with two types of DAS (Distributed Antenna Systems).

Small Cell Type	Cell Radius	Power Level (Watts)	Number of Users
Outdoor DAS (oDAS)	1 mile	20	3,000 per sector
Indoor DAS (iDAS)	Up to 200 feet per antenna	2	2,500 – 3,000 per sector
Microcell	1 mile	10	1,800 per baseband unit
Metrocell	500 – 1,000 feet	5	200
Picocell	750 feet	1	32
Femtocell	50 - 60 feet	0.1	4 - 6
Wi-Fi	50 - 60 feet	0.1	Up to 200 per access point

Definition.

The last two decades has seen an increasing development in the wireless sector where “small cells” are deployed to provide capacity and coverage, both outdoors and indoors. Solutions using small cell are able to achieve increase capacity and high radio densities.

Compared to macro cells, small cells are essentially physically small and low-powered radios that provide operators with a means to densify cellular network in order to add capacity.

Types of Small Cells.

Various types of commercial small cells, including femtocells, picocells, metrocells and microcells, are used for smaller scale cell sites. The various types of small cells are different in a number of ways, including how many users they can support and the technology they use. There are however also numerous similarities. This is the main reason why they are all grouped together under the label small cells, whether commercial or residential. All the types mentioned operate at less power and support less users than traditional large-scale cell sites do.

It is useful to classify small cells not by the type of enclosure they are supplied in, but rather by their function in a wireless network. Small cells are primarily about increasing capacity by diverting traffic away from macro networks, ultimately densifying the network. If this definition is used, a distributed antenna system (DAS) should also be seen as a small cell, as a DAS operates at lower power and adds capacity by offloading traffic, while at the same time being able to support a concentrated group of users. A DAS can in fact be seen as the origin of small cells.

Each of these small cell types play different roles depending on its application. Over the past two decades, the wireless industry has definitely learned that as far as capacity and coverage solutions are concerned, a single solution that fits all scenarios does not exist.

Small Cell Architecture.

When small cells were first used, they were no more than an afterthought in mobile network architectures. Small cells are however becoming increasingly important in wireless service delivery. Small cell solutions are adding sophistication in the form of coordination and plug-and play-features, HetNet and C-RAN. The functional role of small cells of improving quality and adding more capacity in stressed wireless networks does however remain the same.

Plug-and-Play.

In order for the deployment of commercial grade small cells to be able to scale to thousands, or sometimes millions of access points economically, a provisioning methodology is needed that is simpler than what has traditionally been used for both macro base stations and distributed antenna systems (DAS). In the context of small cells, the term plug-and-play is used when small cells are added to a network, it automatically triggers a series of events that results in the configuration of the device for its environment and function. This work very much the same as when a peripheral device is automatically configured when it is connected to a computer for the first time. This type of automation is required by operators, and is crucial for the industry if it is to evolve in the future from a model that is led by operators to a self-service model for enterprises.

HetNets.

Heterogeneous networks, or HetNets, is growing in importance for small cell solutions and refers to combining multiple types of wireless access nodes including small cells, macro cells, wireless LANs and DAS across a common coverage area. These different types of systems, often from a wide range of different vendors, should coexist within one physical footprint for operators. A huge amount of work is going into ensuring simple, graceful coordination for things such as handover management and interference mitigation. Members of the Small Cell Forum continuously work on these aspects to contribute to, and adopt industry wide standard practices.

C-RAN.

C-RAN is a relatively recent concept in small cell architectures. Small cells are nowadays implemented in two basic models – the traditional standalone model where each access point contains a base station, radio and antenna, and C-RAN, where a centralized unit does baseband processing for numerous radios that are distributed through a large building. Each architecture has its own target use cases. C-RAN small cells are ideally suited for big buildings and public venues, while standalone small cells, e.g. femtocells and picocells, work well for small offices, parts of larger buildings e.g. flats, and homes where a single or a couple of units can cover the entire area. C-RAN architecture enables many advances for both deployment economics and for improved cellular performance by enabling multiple radios to form a single "borderless" cell.

Summary.

Small cells add capacity to cellular networks of the big four Carriers - Verizon Wireless, T-Mobile, AT&T Wireless, and Sprint. Being a Small Cell vendor, we have seen small cells evolving over time and now adds capacity in ever evolving ways with plug-and-play features, HetNet coordination and C-RAN architecture taking prominence.

Low-power small cells solutions are evolving to become a part of wireless networks that is increasingly important. Depending upon specific locations and requirements, our licensed Small Cell installers and technicians choose from numerous small cell technologies including picocells, femtocells, metrocells, microcells and distributed antenna systems (DAS). These are best defined by their functions, i.e. they provide network densification solutions that add capacity by offloading traffic from the macro network.