Table of Contents
Advertisement
System characteristics
4. 2
High-frequency propagation conditions
For a better understanding of the explanations on physical conditions given in the
following sections, we first need to take a look at the basic principles of high-fre-
quency propagation.
The method under discussion here is DECT standard. It operates in the frequency
range of 1880...1900 MHz and provides 120 communication channels. All cordless
telephony systems are subject in principle to the following explanations. The expe-
rience gained in planning any system will therefore be very useful when it comes to
planning DECT systems.
4. 2. 1
Interference factors
The knowledge of potential reasons for interference can raise the project engi-
neer's awareness to such an extent that many critical points can be avoided already
at the design stage of the DECT system by using the appropriate measures. In radio
technology there are many interference factors that affect mainly the range and
quality of the transmission.
In principle we need to differentiate between two types of interference factors:
• Interference by obstacles that attenuate and / or reflect radio propagation, caus-
ing dead spots
• Interference due to other radio signals, leading to transmission errors
The receive power of DECT signals can fluctuate a great deal, locally, within only a
few centimetres (see
eliminated simply by altering the position.
70
60
50
40
30
Fig. 7
Obstacle-induced attenuation and reflection of DECT signals
24
Fig.
7). This means that signal interference can be reduced or
slow fading (environment-related)
/2 = 8 cm
(due to stationary waves)
route covered
rapid fading
Planning Aastra 400 DECT systems as of R1.0
syd-0457/1.0 – R1.0 – 10.2012
Advertisement
Table of Contents
