Wireless LAN

Definition: WLANs provide wireless network communication over short distances using radio or infrared signals instead of traditional network cabling.
A WLAN typically extends an existing wired local area network. WLANs are built by attaching a device called the access point (AP) to the edge of the wired network. Clients communicate with the AP using a wireless network adapter similar in function to a traditional Ethernet adapter.

Network security remains an important issue for WLANs. Random wireless clients must usually be prohibited from joining the WLAN. Technologies like WEP raise the level of security on wireless networks to rival that of traditional wired networks.

wireless LAN
Examples: For WLANs that connect to the Internet, Wireless Application Protocol (WAP) technology allows Web content to be more easily downloaded to a WLAN and rendered on wireless clients like cell phones and PDAs.


WLAN standards

WLAN standards below the metropolitan level are fairly well defined; most people have heard about 802.11b and g Wi-Fi standards. Some upcoming standards like 3G are attempting to increase range and seamless availability. Others like 802.1x, EAP, and 802.11i are attempting to increase security. Currently, the industry emphasis is on extending range or strengthening security rather than trying to increase speed, but that may change in the future.

802.11a, b, and g: The big three standards
The 802.11a, b, and g standards are by far the most common ones for home wireless access points up through large business wireless systems. The differences in the protocols are these:

802.11a
- Shortest range of the big three standards (generally around 60 to 100 feet)
- Broadcasts in the 5GHz frequency
- Supports up to 54Mbps (megabits per second) speed
- Less able to penetrate physical barriers like walls
- Better speed than 802.11b, supports more simultaneous connections, and because it operates in a more regulated frequency, gets less signal interference from other devices, so is considered to be more consistent in terms of maintaining a connection. In certain circumstances, such as areas with major radio interference (e.g., airports, business call centers), 802.11a will outperform and actually outrange 802.11b.

802.11b
- Better range than 802.11a: up to 300 feet in ideal circumstances, and better than 802.
11a even in real-world circumstances (Tests by independent reviewers tend to achieve
anywhere from 70 to 150 feet.)
- Broadcasts in the 2.4GHz frequency
- Supports up to 11Mbps speed
- Hardware tends to be lower in cost nowadays.
- Better able than 802.11a to penetrate physical barriers, and lower in cost, but cannot support as many simultaneous connections. Also, it operates on the same frequency as many cordless phones and other appliances; therefore, it is more susceptible to interference and other things that degrade its performance, so it's not considered a good technology for certain applications requiring absolutely reliable connections, such as live video streaming.

802.11g
- Very close to 802.11b in certain aspects; is actually backwards compatible with 802.11b
products (but will run only at 802.11b speeds when operating with them)
- Faster speed than 802.11b; supports up to 54Mbps. Some proprietary solutions (Netgear,
Linksys) manage to get 108Mbps out of the 802.11g standard by broadcasting on more than
one of the eight channels that 802.11b uses.

- Also uses the 2.4GHz frequency
- Slightly shorter range than 802.11b, but still better than 802.11a. Most independent reviews
report around 65 to 120 feet in real-world situations.
- Suffers from the same problems, such as interference and absolute reliability, as 802.11b