6.3 Wireless Networking

Based on how the nodes are organized there are two types of wireless network architectures. In the first such type, called “infrastructure”, all the nodes communicate wirelessly to a central base station, or access point. The network may have several base stations, each covering a different geographical area, and they are typically interconnected through a wired network. In infrastructure-type networks the radio link where the transmitter is a node and the receiver is the access point is called the “uplink”. Conversely, the radio link where the transmitter is the access point and the receiver is a node is called the “downlink”. With infrastructure networks, the access point is usually connected to the Internet through a high capacity link, that may use fiber optics, and that does not necessarily involves a wireless connection. As such, in infrastructure networks, the wireless link may be only one hop on the transmitter side and a second single link wireless hop to access the destination end of the connection if it is also a wireless device.

The second type of wireless network architectures is the ad-hoc network. Here, there is no central base station and all nodes are hierarchically equal. In an ad-hoc network the nodes self-organize to establish the different routes and connections in the network with paths that typically involve multiple wireless hops. Nevertheless, while research into ad-hoc networks has been ongoing for several years, their deployment has been limited, resulting in most of the existing commercial networks being of the infrastructure type.