Chapter 3: System planning
157
Reflect ion likelihood guidance
As shown in the previous section, reflection can cause a decrease in throughput in an ABAB base site. This
section provides guidance on whether a reflection is likely to cause interference. The first condition for
whether a reflection can cause the data rate to reduce is that the reflecting object must be in view of the
AP and the SM to re-transmit the signal. If this is not the case, then the object cannot cause interference.
Given that the potential reflecting object is seen by the AP and the SM, there are a range of object sizes
and a range of zones where we can predict that interference will occur which may reduce the throughput
when both sector 1 and sector 3 are carrying traffic.
Sector Antenna and cnMedusa Antenna show regions enumerated A, B, C, and D. We also need to consider
objects of size 1, 2, 3 and 4 and define the areas where the objects may interfere.
l
object size 1: a flat building face with a clear reflecting property from sector to AP
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object size 2: random metalwork such as a wireless tower
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object size 3: a 0.5 X 0.5m flat metallic face or tree
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object size 4: a 0.2 X 0.2m random metal structure or 0.5 X 0.5m foliage.
The conditions for no interference are:
l
size 2 outside zone B
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size 3 outside zone C
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size 4 outside zone D
The size 1 object can interfere at large distances. It is necessary to look at the geometry by which
reflection could occur and cause interference. Typically, this will occur at a restricted range of azimuths
and ranges.
Figure 60 :
Sector Antenna
Summary of Contents for PMP 450 Series
Page 92: ...Chapter 2 System hardware 92 Figure 29 MicroPoP Omni antenna implementation pattern Vertical...
Page 134: ...Chapter 3 System planning 134 Figure 51 Mast or tower installation...
Page 135: ...Chapter 3 System planning 135 Figure 52 Wall installation...
Page 136: ...Chapter 3 System planning 136 Figure 53 Roof installation...
Page 137: ...Chapter 3 System planning 137 Figure 54 GPS receiver wall installation...
Page 158: ...Chapter 3 System planning 158 Figure 61 cnMedusa Antenna...
