Tyco 0-1591700-x Manuale Utente

Wireless LAN systems need a little more planning than conventional wired LANs. This is because 
the access point relies on the propagation of radio signals, which are sometimes greatly affected 
by a range of factors including:- 

•  building materials,  

•  thickness and type of walls, 

•  proximity of metal,  

•  proximity of radar and other high power transmitters 

•  relative positions and characteristics of client devices. 

If you are uncertain about the characteristics of an intended location for a wireless LAN system, 
then it is advisable to obtain a professional site survey. This will provide a report on the current 
radio environment and may also make recommendations about the location of access points.  
It is possible to conduct your own informal site survey using the software tools provided on some 
client WLAN cards. This is achieved by fitting the appropriate client card into the PC, 
commissioning and installing the Access Point in the intended position and then moving the PC 
around the intended area. Whilst this is not a scientific method, it does provide a quick method of 
determining the likely coverage of an area by observing the relative signal strength.  
Note that radio environments may change due to new radars, transmitters, access points and 
scientific instrumentation being installed near the access point. This means that further site surveys 
may be needed in the future to assist in problem diagnosis. 

a)  Ensure that the number of barriers between the access point and client devices are kept to 

the absolute minimum. In an ideal environment, there should be “line-of-sight” between the 
access point and the client devices. 

b)  If the access point and clients are separated by walls, then ensure that the wall is relatively 

thin and constructed of a material that is of high radio transparency (not steel or re-inforced 
concrete etc).  

c)  If walls separate the client and the access point, then ensure that the wireless devices are 

perpendicular to the walls. This reduces the apparent depth of the wall compared with the 
signals needing to pass through a wall at an angle. 

d)  Reduce the distances between the access point and the client devices to maintain high 

signal strengths. This will keep the data transfer rates achieved over the wireless links to 
the highest possible levels. 

e)  Consider the availability of power for the access point. If power is not available, then the DC 

Power Injector Model 0-15910710-x can be used to inject power for the access point into 
the Ethernet cable at the equipment room. This option enables easy remote powering of 
distant access points. 

Wireless access points are potentially a security risk to a network if no precautions are taken. 
However as with any network, simple precautions can greatly increase the security of a network to 
create a highly secure environment. These precautions include:- 

1.  Change the default SSID setting and password (see pages 22 and 26).  
2.  Hide the SSID value (see page 24) 
3.  Implement an 802.1x authentication scheme if at all possible (see page 25). 
4.  If 802.1x cannot be implemented:- 

a.  Use the integrated WEP encryption at the highest possible key values and change 

the keys on a regular basis (page 24). 

b.  Use the MAC address based filters (page 21) 

5.  Place access points on inner walls of a building and use the lowest possible transmit power 

settings (see page 23).