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The ZetX H-Plane - Let's put this to bed

Below is the TraX H-plane Overlay Sizing Algorithm for the H-Plane boundary as provided by the ZetX webpage ZetX | Scientific Standards.

"Identify 3 closest cell sites within 60° of the azimuth (30 ° each side)

Determine the density mean of the 3 towers (average distance in miles) Example: (1.2 mi + 3.3 mi + 4.5 mi) / 3 mi = 3.0 miles

Multiple the density mean by 0.97 to determine the outer boundary distance of the horizontal plane Example: 3 mi x 0.97 = 2.91 miles"

This is an image of two overlapping H-Planes provided by ZetX.

This same shape is used by ZetX in many legal cases to show the coverage of a cell site sector. The fact that some defendants may have been put in prison because the jury believed a phone was within the shaded red region is extremely concerning.

The legal system has been immensely deficient in providing a level playing field in terms of the knowledge of how cellular networks function. Law enforcement and prosecutors have and do still have significant advantages when it comes to using cell phone data in the courtroom.

The main reason I decided to become an expert witness in the area of cell phone technology is to move the judicial system to a level of fairness when it comes to understanding wireless technologies.

So let's address the H-Plane depiction for coverage because this should be stricken from all legal cases and if it was used to put someone in prison, then the case should be appealed.

I work closely with cellular engineers that design, optimize and troubleshoot cellular networks. I have traveled through the world meeting with the System Performance, Operations and RF Engineering departments of major wireless operators and network design companies. I have tested and continue to test wireless networks. I started my work with analog technologies AMPS, EAMPS, TACS, ETACS, back in the 1990's and have continued through the digital technologies of CDMA, GSM, UMTS, EVDO, LTE, LTE Advanced, 5G. Each of these technologies have different characteristics anbd utilize coverage in different ways, mostly adding improvements along the way. All of these technologies deal with coverage and interference and frequency capacity issues.

When designing or modifying a wireless network the first thing an RF Engineer does is utilize RF Planning software. The engineer loads variable values into the software. Some of these variables include the following:

  • Antenna height

  • Antenna model number

  • Antenna radiation pattern

  • Transmit power

  • Downtilt angle of antenna

  • Database of terrain (hills, valleys, water)

  • Database of clutter (grass, trees, bushes, signs, etc.)

  • Database of buildings (3D buildings with material types)

  • Traffic estimates

  • Drive test data

Once this data is entered into the software, the engineer chooses an algorithm model that best fits the situation. He then allows the software to run the model. The result is an estimate of the coverage of the cell sites in the network. it will typically look something like the image below.

The cell towers are shown in black with three triangles indicating the three sector antennas. The colors represent the coverage for each of the antennas. None of the colored areas look anything like the ZetX H-Plane depiction.

Let's think of it logically and put it through the common sense test. The world around us has many fixed and moving parts. The fixed parts are mountains, hills, valleys, etc. The moving parts are trees, grasses, signs, cars, structures, etc. Radio waves don't penetrate hills and don't bend down into a valley well. They get slowed down by trees and foliage. They bounce off buildings, cars, signs, etc.

Also, many different types of antennas are used on cell sites. Each of these antennas has a different radiation pattern. By this alone we know that one pattern does not fit all situations. When you add in all of the other variables it makes common sense that the coverage pattern for each tower antenna will be different and will look nothing at all like the H-Plane.

For further information you can download and read my testimony on this topic in a recent court case in Illinois from my Forensics web page at The direct link is here

Another reference is a recent case in Colorado that denied the use of the ZetX software and it's H-Plane depiction. You can download the decision here.

Colorado vs Jones
Download PDF • 368KB

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