09.01.2015 Views

Intelligent Transportation Systems - City of Oakland

Intelligent Transportation Systems - City of Oakland

Intelligent Transportation Systems - City of Oakland

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

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

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!