DETEWE varix 14, Описание, Установка, Пусконаладка

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Description varix 200/varix 14 (DECT) 2 - 27
2 Planning a cordless communications network
2.9.3 Delay spread
The delay spread is the maximum deviation of the propagation time along the multiple prop-
agation paths from the mean propagation time via the direct path.
Estimating field coverage
Typical open-air attenuation at a frequency of 1.9 GHz (values rounded to the nearest inte-
ger)
Table 2.2
Since the DECT standard specifies an output power of +20 dBm for DECT FPs and a mini-
mum reception field strength at –83 dBm, a dynamic range of approximately 100 dB is
available. This is a purely theoretical value, however, as the average effect of weather, foli-
age on trees and shrubs etc. decreases this value to 85 dB.
For example: At a particular customer’s location, the field will have to penetrate a concrete
wall. Apart from this, the remaining field conditions can be assumed to be ideal.
Maximum dynamic range + 85 dB
Concrete wall - 20 dB cf. table 2.1
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Remaining dynamic range
+ 65 dB cf. table 2.2
Taking into consideration that the signal loss over a distance of 25 m is already 66 dBm, we
can deduce that the FPs must be installed with a spacing of less than 25 m.
Note: Estimating the dynamic range of the useful radio field does not free the installation
company of the obligation to carry out on-site field strength measurements.
Propagation path length Signal loss at 1.9 GHz 20 m 64 dB
1 m 38 dB 25 m 66 dB
2 m 44 dB 30 m 68 dB
3 m 48 dB 35 m 69 dB
4 m 50 dB 40 m 70 dB
5 m 52 dB 45 m 71 dB
6 m 54 dB 50 m 72 dB
7 m 55 dB 100 m 78 dB
8 m 56 dB 200 m 84 dB
9 m 57 dB 300 m 88 dB
10 m 58 dB 400 m 90 dB
15 m 62 dB 500 m 92 dB