20.5 Wireless Network Topologies

There are two main wireless network topologies: the wireless infrastructure topology (the cellular topology is a special case of it) and the Ad-Hoc topology.

The Cellular Topology

	Cellular topology is a multi-BS infrastructure network topology which uses the frequency reuse concept.
	Need to support as many users as possible, given the limited radio spectrum available.
	Frequency reuse can be described as the spatial reuse of the available spectrum to support multiple users separated by distance.
	The cellular concept is based on Dividing the area to be covered into a number of adjacent smaller areas and allocating a BS to each smaller area.
	The same radio spectrum is used several times in the smaller areas.
	Each smaller area is called a cell. Cells are grouped in clusters.
	The frequency spectrum is divided into bands and distributed among the cluster’s cells. This is done in each of the clusters making the network.
	The Global System for Mobile (GSM) is a worldwide standard for cellular network operations.
	GSM is a multipurpose framework supporting both voice and data services.

20.5 Wireless Network Topologies

The Ad-Hoc Topology

	The Ad-hoc topology is established by mobile nodes and Does not need a pre-existing infrastructure.
	Ad Hoc network topology applies to reconfigure networks that can operate without the need for a fixed infrastructure.
	It is suitable for quick deployment of a wireless network.
	The Bluetooth standard is based on the Ad-hoc topology.
	Ad Hoc networks has two variations: Single-hop and multi-hop.

		In single-hop ad hoc networks, every user terminal can communicate directly with any of the other user terminals.
		In multi-hop ad hoc networks users may be distributed in a wider area, making the user terminal able to reach only a portion of the other users in the network (due to the terminal’s transmitter power). Terminals are aware of their neighbours and cooperate in communicating messages between terminals far apart in the network.

20.5 Wireless Network Topologies

The Advantages of Ad-hoc topology include:

		Ease, speed of deployment
		Decreased dependence on infrastructure
		Can use in many scenarios where deployment of a wired network is impractical or impossible