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 Wireless networks

 

Wireless networks

Even if wired networks are present in most buildings today, sometimes a non-wired solution holds substantial value to the user, financially as well as functionally. 

For example, it could be useful in a building where the installation of cables would not be possible without damaging the interior, or within a facility such as retail outlet where there is a need to move the camera to new locations on a regular basis without having to pull new cables every time.

Another common use of wireless technology is to bridge two buildings or sites together without the need for expensive and complex ground works.

There are two major categories for wireless communications:

  • Wireless LAN (also known as WLAN)
    A LAN is by definition a Local Area Network, i.e. over short distances and normally indoors. Nowadays, the wireless LAN standards are well defined and devices from different vendors work well together.

  • Wireless bridges
    When it is necessary to connect buildings or sites with high speed links, a point-to-point data link capable of long distances and high speeds is required. Two commonly used technologies are microwave and laser.

Wireless LAN standards

802.11a
Standard using the 5 GHz band providing up to ~24 Mbps actual throughput at up to 30m/100feet in outdoor environments. Limited range of products supporting it. Theoretical bandwidth is 54 Mbps.

802.11b
Standard, providing up to ~5 Mbps actual throughput at up to 100 m/300 feet in outdoor environments. It uses the 2.4 GHz band. Theoretical bandwidth is 11 Mbps.

802.11g
The most commonly used standard providing improved performance compared with 802.11b. Up to ~24 Mbps actual throughput at up to 100 m/300 feet in outdoor environments. It uses the 2.4 GHz band. Theoretical bandwidth is 54 Mbps.

802.11n
Next generation of the 802.11 Wireless LAN standard. The actual throughput will be in excess of 100Mbps.

Broadband wireless access
802.16 - WiMAX
IEEE 802.16, also known as WiMAX, is a specification for fixed broadband wireless metropolitan access networks (MANs) that use a point-to-multipoint architecture. The standard defines the use of bandwidth between the licensed 10GHz and 66GHz and sub 11GHz frequency ranges. 802.16 supports very high bit rates in both uploading to and downloading from a base station up to a distance of 50km/30 miles to handle such services as VoIP.

Typical network including both wireless and wired connections

The center point here is the network switch. To the left, a server and a PC client, are connected using wired Ethernet. Next to the switch, there is a wireless access point. This device manages all the wireless devices within range.

Two wireless devices are represented on this diagram:

  • The AXIS 207W Network Camera. This camera has built-in support for wireless communications.
  • A wireless device point. This device provides wireless communication and connects directly to an Axis network camera that has no built-in support for wireless communications.

It is also possible to connect the server and the PC wirelessly. But as the wireless network bandwidth is limited compared with the wired one, the goal should always be to use wired networks whenever possible.

About security in wireless networks

Due to the nature of wireless communications, everyone with a wireless device present within the area covered by the network will be able to participate in the network and use shared services; hence the need for security. The most commonly used standard today is WEP (Wireless Equivalent Privacy), which adds RSA RC4-based encryption to the communication, and prevents people without the correct key to access the network. But as the key itself is not encrypted, it is possible to 'pick the lock', so this should be seen only as a basic level of security. A WEP key is normally of either 40 (64) bits or 128 bits in length. Lately, new standards being deployed significantly increase security, such as the WPA (WiFi Protected Access) standard, which takes care of some shortcomings in the WEP standard, including the addition of an encrypted key.

Wireless bridges

Some solutions may also use other standards than the dominating 802.11 standard, providing increased performance and much longer distances in combination with very high security. This also includes the use of other means of Radio Frequency, such as microwave links. 

Another common technology is optical systems such as laser links. A microwave link can provide up to 1000 Mbps for distances up to 80 km/130 miles. For locations outside the range of all these systems, there is also the option of satellite communication. Due to the way this system operates, transmitting up to a satellite and back down to earth, the latency can be very long (up to several seconds). This makes it less suitable for functions like manual dome control and video conferencing where low latency is preferred. If larger bandwidth is required, the use of satellite systems also becomes very costly.

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