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10.1 802.11 WLAN standards
The most common wireless standard for wireless local area networks (WLAN) is the 802.11
standard by IEEE. While there are also other standards as well as proprietary technologies, the
benefit of 802.11 wireless standards is that they all operate in a license-free spectrum, which
means there is no license fee associated with setting up and operating the network. The most
relevant extensions of the standards are 802.11b, 802.11g, 802.11a and 802.11n.
.
802.11b, which was approved in 1999, operates in the 2.4 GHz range and provides data rates up
to 11 Mbit/s. Until 2004, most WLAN products sold were based on 802.11b.
802.11g, which was approved in 2003, is the most common 802.11 variant on the market. It
operates in the 2.4 GHz range and provides data rates of up to 54 Mbit/s. WLAN products are
usually 802.11b/g compliant.
802.11a, which was approved in 1999, operates in the 5 GHz frequency range and provides data
rates of up to 54 Mbit/s. An issue with the 5 GHz frequency range is that it is not available for
use in parts of Europe where it is allocated for military radar systems. In such areas, 5 GHz WLAN
components should conform to 802.11a/h standard. Another disadvantage with 802.11a is that
its signal range is shorter than 802.11g’s because it operates on a higher frequency; conse-
quently, many more access points are required for transmission in the 5 GHz range than in the
2.4 GHz range.
802.11n, which is not yet completed and ratified, is the next generation standard that will
enable data rates of up to 600 Mbit/s. Products supporting 802.11n are based on a draft of the
standard.
When setting up a wireless network, the bandwidth capacity of the access point and the band-
width requirements of the network devices should be considered. In general, the useful data
throughput supported by a particular WLAN standard is about half the bit rate stipulated by a
standard due to signaling and protocol overhead. With network cameras that support 802.11g,
no more than four to five of such cameras should be connected to a wireless access point.
10.2 WLAN security
Due to the nature of wireless communications, anyone with a wireless device that is present
within the area covered by a wireless network can share the network and intercept data being
transferred over it unless the network is secured.
To prevent unauthorized access to the data transferred and to the network, some security technolo-
gies such as WEP and WPA/WPA2 have been developed to prevent unauthorized access and encrypt
data sent over the network.
CHAPTER 10 - WIRELESS TECHNOLOGIES
