The ad hoc and infrastructure modes are used by wireless local area networks to connect devices to the networks. Although both modes allow computers and devices to connect to each other on a wireless network, infrastructure mode requires the use of an access point for this communication to take place. Ad hoc mode, on the other hand, uses a direct computer-to-computer connection and is best suited for small home networks. Ad hoc mode involves connecting a computer directly to another computer, so it is often called peer-to-peer networking.
Ad hoc and infrastructure modes differ greatly in how the network is set up. In an ad hoc network, each device's network adapter directly communicates with other devices through the use of software. This software can be included with the device's operating system or purchased from a third party. This provides an inexpensive and quicker way to connect than using infrastructure mode. Another benefit of an ad hoc network is that the connection speeds can be significantly faster than when using a wireless accent point with infrastructure mode.
Infrastructure networks consist of the networked devices and the wireless access point or wireless router. Each device must connect to the access point before having access to other computers on the network. While both ad hoc and infrastructure networks can provide a secure connection, infrastructure mode supports various encryption methods. Additional security features allow the use of passwords and allow computers to connect by checking a device's media access control (MAC) address.
Another difference between ad hoc and infrastructure networks is in the area of expandability. The access point used with infrastructure mode can support multiple clients on both wireless and wired networks. The direct connection method used with ad hoc mode is prone to interference and is not useful for a large corporate network. In addition, ad hoc mode does not support wireless clients, so all computers will need wireless adapters. Wireless access points used in infrastructure mode can also support additional features, including Internet sharing, roaming and the ability to expand a network using multiple access points.
Although infrastructure mode is usually more useful than ad hoc mode, wireless access points lead to increased costs and more time for initially setting up the network. Another downside is that the network speed will be lower than an ad hoc network's because data must travel to the access point before reaching another computer. Large networks usually do, however, benefit from using infrastructure mode anyway.