combiner
correct
never
Fig. 3.5: Main lobe
3.5. Network layout
Certainly the network layout is mostly (sometimes completely) defined by the application. When the
terrain allows for direct radio communication among all sites in the network, the designer can do neither
too good nor too bad a job. Fortunately for RF network designers, the real world is seldom that simple.
The conditions every single radio hop has to meet were discussed in previous paragraphs. If we are
so lucky, that different layouts meeting that conditions are possible, we should exploit that for the be-
nefit of the network. The following rules should be followed when defining the layout of radio hops:
•
dominant radio sites (e.g. telco towers on hill tops) should be avoided whenever possible. Placing
a single repeater which serves most part of the network from the top of a hill is a straightforward
but worst alternative, which makes the whole network very vulnerable. First, a dominant site is ex-
posed to interference from a large area; second, such site is typically crowded with radio equipment
of all kinds, which keeps being added, moved (also failing to work properly), so local interference
may appear anytime; third, it makes the majority of communication paths dependent on a single
site, so one isolated failure may stop almost the entire network.
•
when total throughput is important, typically in report-by-exception networks, splitting the network
into several independent or only slightly overlapping areas of coverage can help. The placement
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Network planning
