Cellular Networks

By david chow

To efficiently reuse wireless spectrum, wireless network are divided into cells. In general a cell is a hexagon in shape. Based on the radius of the cells, there are three types of cellular networks, including (1) macrocells, (2) microcells, and (3) picocells.

Macrocellar wireless network

A macrocell can cover a large area with a radius ranging from 1 to 10 km. a distinction can be further made to for large macrocells and small macrocells. A large macrocell can cover a range with a radius of 5 to 10 km, which is mainly used for rural areas with little traffic. In contrast, a small macrocell generally covers a range with a radius between 1 and 5 km. This types of cells are used if traffic density is high. Macrocellar wireless networks transmit a very high radio power to cover a large cellar area. They have low spectrum efficiency due to its large cell coverage. The typical rms delay for a macrocell is at the range of 10us.

Microcellar wireless network

Microcellar networks are deployed in area with high density of traffic such as suburb. Each microcell generally covers a radius ranging from 200m to 1km. Microcellar networks can be deployed as a chain or in two dimensions. The chain-like deployment is often made along a highway with high traffic densities, while the two-dimension deployment is often made in the city streets. In this deployment, buildings help block signal from neighbouring cells, thereby decreasing co-channel interference. Comparatively, microcellar networks have better spectrum efficiency than that of macrocellar networks. Typical rms delay for microcell is around 2us due to its smaller coverage area.

Picocellar wireless network

Picocellar wireless network is a type of wireless network with the smallest radio coverage. Its radius ranges from 10 to 200m. Such a type of network is often deployed in a room. Thus, it is often called indoor wireless network. Picocellar wireless networks have the best spectrum efficiency among the three types of cellar networks. Also, due to its smallest coverage, it transmits the lowest radio power and has the smallest rms delay ranging from 50 to 300ns.

Summary

Three types of cellar wireless networks are introduced. They cover different cellar areas and are applicable to different wireless communication scenarios. In general, a macrocellar network covers the largest area, but requires the highest transmission power and shows the lowest spectrum efficiency. In contrast, a picocell network transmits the weakest radio signal to cover the smallest area like a conference room. It achieves the best spectrum efficiency.

This article was contributed by Wireless Technology: http://www.ylesstech.com

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