Intelligent Transportation Systems - City of Oakland
Intelligent Transportation Systems - City of Oakland
Intelligent Transportation Systems - City of Oakland
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Figure 6.1 – Communications Topologies<br />
Field<br />
Device<br />
POINT-to-POINT<br />
NODE<br />
Field<br />
Device<br />
DAISY-CHAIN<br />
NODE<br />
Field<br />
Device<br />
Field<br />
Device<br />
Field<br />
Device<br />
RING<br />
NODE<br />
Field<br />
Device<br />
Field<br />
Device<br />
Field<br />
Device<br />
6.4.2.1 Star Topology (Point-to-Point)<br />
The star topology is comprised <strong>of</strong> a main hub point with many point-to-point<br />
communication links extending from it. The point-to-point communication links provide<br />
quick response times due to a dedicated channel between each point; however this<br />
presents a reliability problem such that if the medium/connection is cut, the channel has<br />
no other path to maintain the connection. Most microwave communication technologies<br />
(and leased services) use point-to-point topology. In the case <strong>of</strong> fiber optics, point-topoint<br />
topology requires more fibers than daisy-chain or ring topologies because one or<br />
more fibers are dedicated to each field device. In the case <strong>of</strong> microwave, separate pairs<br />
<strong>of</strong> microwave antennas are required for each path.<br />
If the field devices were connected in a star topology, the hub would serve as the central<br />
collection point, through which all communication would be routed. The advantage <strong>of</strong> a<br />
star topology is the simplicity <strong>of</strong> design and configuration.<br />
The disadvantages <strong>of</strong> the star topology include:<br />
<strong>City</strong> <strong>of</strong> <strong>Oakland</strong> ITS Strategic Plan<br />
69 September, 2003