Axis IP-Surveillance system Design Manual page 22

Wireless networks
When running a cable between a LAN and a network camera is impractical, difficult or expensive, a
wireless solution using a wireless access point—also called a device bridge or wireless router—is a good
option. Wireless technology can be useful, for example, in historic buildings where the installation of
cables would damage the interior; within facilities where there is a need to move cameras to new loca-
tions on a regular basis, such as in a supermarket; or in outdoor installations. Wireless technology can
also be used to bridge sites without expensive ground cabling.
Network switch
Axis network
Server
camera
Wireless access
point
PC client
Wireless device
Axis network
Axis network
point
camera camera
Figure 2.3.b. A network with wired and wireless connections.
Security in wireless networks
Securing a wireless network should be addressed. Otherwise, everyone with a wireless device present
within the area covered by the network will be able to participate in the network and use shared ser-
vices. 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 from access-
ing 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 new standard, the WPA (WiFi Protected Access), significantly
increases security by taking care of some of the shortcomings in the WEP standard with, for instance,
the addition of an encrypted key.
When using wireless cameras for surveillance, there are a few rules of thumb:
> Enable the user/password login in the cameras
> Enable the encryption in the wireless router/cameras
> Since wireless routers do not have the same bandwidth capacity as a normal switch, no more than
four to five cameras should be connected to a wireless access point.
2.4.
Hardware (storage needs)
Similar to the way a PC can "save" documents and other files, video can be stored on a server or PC hard
disk. Specialized equipment is not needed since a storage solution treats video data like any other large
group of files that can be stored, accessed and eventually deleted. Video storage, however, puts new
strains on storage hardware because it may be required to operate on a continual basis, as opposed to
during normal business hours with other types of files. In addition, video by nature generates very large
amounts of data, creating high demands on the storage solution.
Calculating the storage needs
In order to appropriately calculate the storage requirements of a network surveillance system, there are
a number of elements to factor in, such as the number of cameras required in your installation, the num-
ber of hours a day each camera will be recording, how long the data will be stored, and whether the
system uses event triggers such as video motion detection or continuous recording. Additional param-
eters such as frame rate, compression, image quality and scene complexity (little motion or lots of mo-
tion) should also be considered.
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