What is a Wireless Bridge?
A wireless bridge is a hardware component used to connect two or more network segments (LANs or parts of a LAN) which are physically and logically (by protocol) separated. It does not necessarily always need to be a hardware device, as some operating systems (such as Windows, Linux, Mac OS X and FreeBSD) provide software to bridge different protocols. This is seen commonly in protocols over wireless to cable. So in a sense the computer acts as a bridge by using bridging OS software.
Many wireless routers and wireless access points offer either a "bridge" mode or a "repeater" mode, both of which perform a similar common function, the difference being the bridge mode connects two different protocol types and the repeater mode relays the same protocol type. Wireless routers, access points, and bridges are available that are compliant with the IEEE802.11a, b, g and n standards. The frequency bands for these wireless standards can be used license-free in most countries.
Wireless bridge devices work in pairs (point-to-point), one on each side of the "bridge". However, there can be many simultaneous "bridges" using one central device (point to multipoint).
Bridging can be via WDS (Wireless Distribution System) which creates a transparent Level 2 wireless bridge between two or more points. Alternately the bridge can be set up as an access point – client relationship which requires the wireless devices used for the bridge to be set to the same service set identifier (SSID) and radio channel.
An example of a point-to-point bridge application would be connecting two commercial buildings. An example of a combination point to point bridge and point to multipoint application would be connecting multiple farm buildings.
Bridging has historically referred to propagation of data across a device without traversing a network stack, such as TCP/IP. Wireless bridging is a colloquial term. A more accurate description of connecting two local area networks would be a Wireless LAN to LAN bridge. The distinction is important. While a device may not support bridging to a remote wireless access point to connect two LANs, it may be desirable (and supported) that a wireless access point support true bridging; where packets traverse from a wireless to wired network without passing through an internal protocol stack, firewall or other network abstraction. Two bridged networks could be treated as parts of a single subnet under Internet Protocol (IP). A wireless client would be able to make a DHCP request to a wired DHCP server if the wired and wireless networks were bridged. In the ISO OSI model, a device in which packets traverse the network layer is considered a router, a device in which packets traverse the data link layer only is considered a bridge.
Unless a user has a wireless card with a PXE-ROM chip built into it, it is not easy to directly netboot over a wireless connection. BIOS-based PXE algorithms usually only search for a wired NIC to be used in a PXE netboot.
It is possible to connect a "wireless bridge" (i.e. a wireless router or access point set to the "bridge" mode) to the wired NIC of a PC. The PC then netboots through the wired Ethernet NIC as usual, but the data is then transmitted from the NIC to the wireless AP/router connected to it and then wirelessly "across the bridge" to a central wireless access point/router.
This requires two wireless devices (one wireless access point and one client device), making it a more expensive solution. It is sometimes, however, easier or less expensive than running extra Ethernet cables between the two points.