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Worst of two arbitrary channels,
90 rmin=100m
Pr{I < x} (percent) 70 Least-interfered channel:
single FWA slot (same as Fig. 1)
worst of two FWA slots
50
30 Assumptions:
10 FWA traffic density = 300 E/km2
5-km radius of interference, free space propagation
1 Downlink interference only
-70 FWA "microbase" stations with 10 dBi gain
120 FWA channels
15 dB building attenuation
Cochannel interference only
-65 -60 -55 -50 -45
x (dBm)
Figure 5.2: Effective cochannel interference to a UPCS system that has the same frame
structure as the FWA system, but is not synchronized with it.
For a UPCS system with a frame structure different than that of the FWA system, the problem is
aggravated. For example, a PACS-UB system has a 2.5 msec frame, so two uplink and two
downlink transmissions occur during the 5-msec FWA downlink. Therefore, a given PACS-UB
slot pair can receive interference from up to eight FWA downlink slots, and the effective
interference on the PACS-UB channel will be the worst of these (i.e., highest interference).
Figure 5.3 illustrates the concept, and Figure 4 shows the corresponding effect on the interference
distribution.
Figure 5.3: Illustrative example of slot coincidence for DECT and PACS-UB
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