From Wikipedia, the free encyclopedia.
A wireless access point (WAP or AP) is a device that "connects" wireless communication devices together to create a wireless network. A wireless access point acts as the network's arbitrator, negotiating when each nearby client device can transmit. The WAP is also usually connected to a wired network, and can relay data between devices on each side. Many access points can be connected together to create a larger network that allows "roaming" where a person using the network can move from the communication range of one WAP to another and experience no data loss. One of the most common AP types is the 802.11 or "Wireless Ethernet" access point connecting an Ethernet network to so-called "Wi-Fi" devices, but other devices (such as those connecting mobile phones to wired phone networks) can also be considered WAPs. In Wi-Fi parlance, a network with at least one active wireless access point doing its duty is said to be a managed network or an infrastructure network. In contrast, a network where the client devices manage themselves is called an ad-hoc network.
Wireless access points with easy installation and low cost (at first glance) rapidly grew in popularity in the late 1990s and early 2000s. These devices offered a way to avoid tangled messes of Category 5 cable associated with typical Ethernet networks of the day. While wiring a business, home, or school often requires stringing many cables through walls and ceilings, wireless networking offers the ability to cut down on the number of cables strung or, in some cases, remove them entirely. Wireless networks also give users greater mobility freeing individuals from the need to be stuck at a computer tied to the wall. On the industrial and commercial side, wireless networking has had a big impact on operations: employees are often armed with PDTs having barcode scanners and wireless links, allowing them to update work progress and inventory in real-time.
One 802.11 access point can typically communicate with 30 client systems within a radius of anywhere from 50 to 300 feet. However, communication range varies a lot in the wireless world. General placement (indoor, outdoor, height above ground, nearby obstructions, etc.) is one very major variable. Other issues include the type of antenna, the current weather, operating radio frequency, and power output of the device. Some experiments have been carried out to allow computer networking over distances of several miles or more (though such placement is not unusual for cellular systems).
A typical corporate use of WAPs is to attach one to the wired network and then provide wireless client adapters for users who need them. Within the range of the access point, the wireless end-user has a full network connection with the benefit of mobility. In this instance, the access point is a gateway for clients to access the network. Another use is to bridge two wired networks where cable is not appropriate; for example, a manufacturer can connect a remote warehouse (within line of sight) by radio, with a wired network in each facility.
Another topography is called a lily pad network: a series of access points spread over a large area, each connected to a different network, providing hot spots where wireless clients can connect to the Internet without regard for the particular networks to which it's attached at the moment. The concept is somewhat accidental in large cities, where a combination of coffeehouses, libraries, and other public spaces offering wireless access allow clients to roam over a large area (i.e., hopping from lily pad to lily pad), staying more or less continually connected.
Additionally, the range of wireless access points can be extended through the use of repeaters and reflectors, which can bounce and/or amplify radio signals that ordinarily couldn't be received.
Usually, adjacent access points will use different frequencies to communicate with their clients. This avoids interference between the two nearby systems. However, wireless devices often take time to "listen" for other data traffic in the area on different frequencies, and are able to rapidly switch from one frequency to another when moving into an area that has better reception on a different AP. Unfortunately, this becomes problematic in crowded areas such as downtown areas with tall buildings. There can be enough overlap between the wireless networks of several businesses to cause interference because there just aren't any more frequencies available.
Wireless networking is far behind wired networking in terms of bandwidth and throughput. While (as of 2004) typical wireless devices for the consumer market can reach speeds of 11 (802.11b) or 54 megabits per second (802.11a, 802.11g), wired hardware of similar cost reaches 1000Mbps (Gigabit Ethernet). Networks that existed before the advent of wireless still remain, or have even been upgraded to higher bitrates, and there is desire to see wireless networks increase in speed to keep up.
Another issue with wireless access in genral is the need for security. Many early access points did not have very good abilities to discern if a particular user was authorized to access the network or not. This problem reflects issues that have long troubled many types of wired networks. It has been possible in the past for individuals to plug computers into random available Ethernet jacks and get access to the network. This was usually not much of a problem, though, since many businesses had reasonably good physical security. However, the fact that radio signals bleed outside buildings and across property lines means that the physical security aspect is not as much of a deterrent.
In response, several new security technologies have emerged. One of the simplest techniques involves only allowing access from certain MAC addresses, which works well in many cases. However, MAC addresses can be easily spoofed, leading to the development of more advanced measures. Many access points incorporate Wired Equivalent Privacy encryption, but that has been decried by many security analysts as not quite good enough (one common complaint is: "Wired Equivalent Privacy isn't"). A newer system for authentication is 802.1x, which promises to enhance security on both wired and wireless networks. Access points that incorporate technologies like these often also have routers built in, so they are somewhat more accurately described as wireless gateways.
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