WiMAX RF Systems Engineering (Artech House Mobile Communications Library) by Abate Zerihun

Author:Abate, Zerihun [Abate, Zerihun]
Language: eng
Format: azw3
Publisher: Artech House
Published: 2012-07-24T16:00:00+00:00

A database of anchor sites should be created and ranked according to RF suitability and the probability of securing a lease. In order to rank them from an RF perspective, several RF study iterations should be done. The first iteration should be one that includes all the anchor sites. Subsequent iterations will successively turn off sites in the coverage studies that appear to be redundant. Then a variation of these studies will be created, turning on the sites turned off in the previous studies and turning off those that were turned on.

Anchoring design on real sites has one great obvious benefit: time saved that would have been lost during redesign when invariably the theoretical design fails to align with the coverage objective. The final goal is building a working site location that meets the coverage objective. In other words, considerable time would be lost in adjusting theoretical sites to fit into the actual design and make it ready to be built. On the other hand, it is also true that some finite time will be required to find real sites to which the design can be anchored. However, the time lost for design and redesign to conform all theoretical sites to final design would be considerably higher. In any event, coordinating the computer design with an actual visit to the field or to site-acquisition personnel expedites the design and deployment process.

Ideally, you want the best location from an RF perspective that you can lease with minimal to no opposition from the neighborhood when the time comes to actually construct it. Well, how do you know if a site location is ideal from an RF vantage point? Mainly you want a clear view overlooking the coverage-objective locations. If, for example, a rooftop of a building is the prospective location, go up to the rooftop where the antennas are supposed to be located, and verify if your coverage objective is in clear view. For example, if it is a highway intersection you wish to cover from that location, then verify that the intersection is in clear view from the antenna location. Imagine the antenna propagating vertical and horizontal beamwidths, and make sure no nearby object or a building’s edge or parapet obstructs the propagation. If necessary, you should take back a sketch and measurement of the area, along with the antenna height, to your office and determine the proper clearance and angles.

If the prospective location is a tower being used by other service providers, you can rest assured it is a good location. However, you should determine where your antennas are going, whether higher or lower (or in the middle) than the other providers. Of course, frequency and distance (both vertical and horizontal) separation must be verified. (The guideline for vertical and horizontal separation of antennas is covered in Section 5.5.)

The height of the site location is critical. While a very tall site is nice to meet the coverage objective, it could be a source of a serious interference. If it so

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