2 - 18
Description varix 200/varix 14 (DECT)
2 Planning a cordless communications network
The areas in the figure which would seem not to be covered are in fact covered as a result of
reflections. A low level of multi-path propagation (refer to Figure 2.7) means that there are
fewer reflections, subsequently the bit-error rate decreases due to a reduction in the delay
spread. This has a direct effect on the quality of the hop.
2.5.5
Antenna diversity
The reflections and polarisation plane rotations described in the preceding chapters are off-
set using the so-called "diversity method". This method is based on selecting the antenna
which has the best reception at the receiving end (FP). Initial scientific research has shown
that spacing directional antennae horizontally (space diversity) achieves better results than
vertical spacing.
Note:
When using directional antennae, both must point in the same direction, as only one is
active at any given time, with the other being switched over to when required (diversity
method). In addition, both directional antennae should be mounted next to each other hori-
zontally in order to achieve maximum diversity advantages.
