Motorola TUT 45010 MC-802 wireless cpnt wallplate 557925-001-00 User Manual

 

 
 

The material used in walls and floors can vary from one property to another.  For example, 
different chemical formulations of concrete can cause loss variations up to 5dB.  The following 
chart is based on RF engineering studies and can be used as a general guide. 
 

Concrete block 

 

15 - 20 

+

6 

=

21 – 26 

Red Brick 

 

15 – 25 

 

6 

 

21 – 31 

Drywall 

 

3 – 6 

 

6 

 

9 - 15 

Many software site survey tools are readily available for a charge or free.  Using the RoomLoss 
method; it is only required to use a software tool that displays all visible BSS (AP MAC address) 
and their associated RSSI and channel.  NetStumbler is one such tool.  Cisco CB21 PCMCIA 
cards also provide this information using the included software suite. 
 
While many manufacturers may use the same wireless radio chipset, implementations can vary 
quite a bit.  RF sensitivity on the board, antenna design and antenna cable losses all vary from 
one laptop model to another. 
 
Since we are primarily interested in the signal delta (its loss factor), the actual RSSI reading is not 
quite as important.  Validate the laptop sensitivity before beginning the installation, using this 
procedure: 
 

1.  Set the Wireless WallPlate in site survey mode by loading the special software, or turn on 

the WallPlate and set the transmit power to 14dBm 

2.  Align the WallPlate in a vertical position with the flared tabs on the top and bottom 
3.  Place the laptop at 1meter away from the WallPlate AP on the same vertical height.  The 

RSSI of the WallPlate should be between -26dBm and -30dBm. 

It is desirable for an installation to provide adequate signal coverage with the loss of any single 
AP.  Passive redundancy, or rather redundancy by design, requires an installation in which every 
location receives adequate signal levels from two or more APs.  This must be balanced with the 
potential for co-channel interference. 

Because of the media access method described above, each AP or client will reduce the 
bandwidth available to any other AP or client on the same channel.  This co-channel interference 
is expected and predicted by carrier detection and media access.  While we cannot control where 
a client will be located, we can control the co-channel interference between any two WallPlates 
during the installation.  Selecting the installation density to control co-channel interference is the 
point of this document. 

RF signals are like rolling a football; they take a funny bounce.  Sometimes, a strong signal can 
be received in one location; while movement of only a few feet can result in much lower signal.  
Each WallPlate AP has two antennas with receive diversity.  Simply stated, the signal from any 
other transmitting device is received by both antennas, and the stronger signal is passed to the 
wireless driver. 

Motorola, Inc 

 

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