3 Network architecture
3.2 Architectures

In wireless networks there are two modes for configuring a wireless architecture, ad hoc and infrastructure [1-2]. In Ad hoc mode, devices transmit directly peer-to-peer while on in infrastructure mode, devices communicate through an access point that serves as a bridge to other networks.

Ad hoc mode

By using ad hoc mode, all devices in the wireless network are directly communicating with each other in peer to peer communication mode (point-to-point). The network has no structure or fixed points. No access point is required for communication between devices.

Ad hoc mode is most suitable for small group of devices and all of these devices must be physically present in close proximity with each other. The performance of network suffers while the number of devices grows. Disconnections of random device may occur frequently and also, ad hoc mode can be a tough job for network administrator to manage the network. Ad hoc mode has another limitation is that, ad hoc mode networks cannot bridge to wired local area network and also cannot access internet if without the installation of special gateways.

However, ad hoc mode works fine in small environment and provides the easiest and least expensive way to set up a wireless network.

Infrastructure mode

The other architecture in wireless network is infrastructure mode. All devices are connected to wireless network with the help of an access point (AP). Wireless access points are usually routers or switches which convert airwave data into wired Ethernet data, acting as a bridge between the wired LAN and wireless users. Connecting multiple access points via a wired Ethernet backbone can further extend the wireless network coverage. As a mobile device moves out of the range of one access point, it moves into the range of another. As a result, wireless clients can freely roam from one access point domain to another and still maintain seamless network connection.

The infrastructure mode provides improved security, ease of management, and much more scalability and stability. However, the infrastructure mode incurs extra cost in deploying access points such as routers or switches.

Extended Service Set Identifier (ESSID)

The Extended Service Set Identification (ESSID) is one of two types of Service Set Identification (SSID). In an ad hoc wireless network with no access points, the Basic Service Set Identification (BSSID) is used. In an infrastructure wireless network that includes an access point, the ESSID is used, but may still be referred to as SSID.

A service set identification (SSID) is a 32-character (maximum) alphanumeric key identifying the name of the wireless local area network.

Some vendors refer to the SSID as the network name. For the wireless devices in a network to communicate with each other, all devices must be configured with the same SSID.