Pinpointing your Connected mobile cell Tower: (Methods/Possibilities - Part 2) - Nourishing Tech Appetite

In this second part, you would regenerate ideas from different techniques, which are mostly used by network operators. You would find possibilities through discussion and also some experiments methods that I have performed.


The post is so simple and focused that it will be easier for audiences, who have little or no technical background. Let’s proceed.

 


 

 


Exploring the process and ideas

 
Locating the exact location with accuracy is a difficult task. There are various factors involved in the process which I discussed earlier. (You may read it in the first part to know the foundation.). The other reason is the map of cell towers, which are largely undisclosed in public by the network carrier due to privacy concern.


But there are some methods you can implement. Though the process is largely used by network operators to determine a phone’s location, you can get the general ideas, concepts and principle behind the techniques to further improve your knowledge.

 
My idea is simple. I just want to make you aware of different techniques first because it can help you in understanding my whole process. And also because when I get into the last session of the topic through experiment, you could better grasp my reverse technique.


Exploring the methods 

 
1. Cellular triangulation process


The triangulation process uses cellular signals from multiple cell towers to estimate a phone’s location. Mobile phone communicates with different cell and then the connection is established. The connected one then becomes the primary tower or, you can say it as the first point to start the tracking process. Mobile network operator then analyze the signal by calculating the times for signals to travel between phone and towers to determine the phone’s location. This is called a cellular triangular process.


The triangulation process is actually can be assumed as geometric method. Remember your 10th strand school’s mathematical class? You can easily determine the position of a point if you know other reference points. You just have to measure the angle or distance from the known point.


Let see the context with examples


Angular triangulation: assume you're friend is standing at point A and can see two points, B and C. Now you can measure the angles formed between the lines AB and AC. You can also figure out the distances between A and other two points. By using trigonometry you can easily calculate the distance and angle and the exact location of point A.


Distance triangulation: if you know the distances from one point to more than one reference points, location can be easily tracked by finding the intersection point of circles centered on those reference points. 

Here each circle's radius will be equal to the distance from the reference point to the point of interest and the intersection point of these circles will be the position that you want to find.


In this case of tracking location:  

  • The reference points will become locations of cell towers.
  • By analyzing and calculating the time it takes for signals to travel between the mobile phone and each tower, distance, angles and location of phone can be determined within a certain radius of accuracy. 

 

2. Finding the source of signals


Now let’s move further and try to explore that how you can find the source of signal by some right equipment and knowledge. 


How can it be?


To find it, the best way is to use two or more directional antenna with signal indicator. Want to know more about directional antenna?  You may read my post front to back ratio, which will help you in understanding more about it.

 
In short a directional antenna is well designed to focus on a particular direction with narrow beam width. It means, it can catch the signal from a particular direction according to its design. It works on front direction rather than back direction.


Here’s the idea:


Place one directional antenna focusing toward the estimated source of signal. Just focus the antenna to the north direction first. Slowly rotate it from north to east and east to south. 


While rotating find the highest signal strength by the help of an indicator you have. Place your antenna tightly where it gets the highest.


Now do the same process with the second antenna but far from the first one.



Understand it by example


Place the one antenna to position A and the second one at B point. Face both the antenna towards the source of signal which is point C. while rotating antenna you get the highest signal. Just place it there tightly. Now draw an imaginary base line between A and B and C. Now by trigonometry you can easily estimate the angle as well as distance of the signal source right?


Conducting Experiments to Track a connected Cell Tower


Now we have reached to the final session and after reading the above paragraphs you might have equipped with several ideas isn’t it?


So, it is the time to see some experiments which I performed to track the cell. Here I have used the indicator of phone and TA value. Now what is Ta?(timing advance). It is a parameter used in mobile communication. It is measured in units of time (typically, in microseconds or chip units).


The Timing Advance (TA) value is used in cellular technologies to help determine the distance between a mobile device and the base station (tower). Though it is not directly related to distance, a larger TA value generally indicates that the mobile device is far away from the tower, while a smaller TA value suggests that it is closer. I will discuss it in details in another post.


Measuring signal travel time (Propagation time)


This experiment was performed in semi urban areas. And the tower was in line of sight. 


 


 

The tower has three sector antennas. The first experiment is done with first sector and the second one is done with another sector.


Now let’s see this snap shots of inicators





In the first snap shot(sector 1) the TA value is 2 and the distance is approximately 200 meters. In the second one(sector 2), the TA value is 1 and the distance is nearly 100 meters.

 
Note: Look the changed pci when I move to another sector or antenna.

Now let’s find how much time it takes for the signal to travel from my phone to the tower which is 200 meter.

 


 


Now radio waves travel at the speed of light which is 299,792,458 meters per second but speed reduces when travel in air so, the speed of light in air is 299702547.236 meter/s. Therefore we will use the second one.

 


For calculation we have followings

 
Speed to light in air = 299702547.236 meter/s 


Distance =200 meter


We have to find that how much time it takes for signal to cover 200 meter.


Converting 1 second in microsecond = 1000000 microsecond 


If Signal travels 299702547.236 meter in 1000000 microsecond
 

Then it will travel 1 meter in microsecond =1000000/299702547.236= 0.0033366416442652 microsecond


Therefore, 200 meter will be traveled in microsecond = 0.0033366416442652 * 200 = 0.6673283288530428 microsecond

Second experiment


If 200 meter is travelled in 0.6673283288530428 microsecond


Then traveling 100 meters at the same speed will take half of that time that is 0.667 microseconds / 2 Time (in microseconds) = 0.3335 microseconds


These calculation shows one way propagation time of both experiments.

 
It means if we calculate the time for a round trip then we would get 0.667 * 2 = 1.334656657706086 microseconds for the first experiment where we have TA value 2


In the same way we would get = 0.3335 * 2 = 0.667 microsecond in second experiment where the TA value was 1


Experiment 3: Utilizing Directional Antennas


The above experiments will be difficult in areas where numerous cell towers exist very closer to each other. But it can also be solved and, estimation of tracking can be narrowing down by using directional antenna which I talked earlier to find the signal.

 
Note: All these and above experiments are only possible and can give the most relevant result when it will be performed in line of sight (scenarios where you can see the towers directly and no obstacles)


How would you do?


Assume yourself in a place where you are surrounded by four cell towers and have no ideas which one you are linked to. Perhaps it can also be possible one of them may not belong to you network carrier.


Narrowing down with directional antenna


The thumb rule is to use a good directional antenna (lpda or yagi) with a signal indicator. You can also use a booster with antenna to make it more precise estimation.


Experiment


First you have to find the TA value, but the problem is that it is remained idle and only activated when we initiate call or data. But there is an idea to active it to get a current ta value. For this just dial *#*#4636#*#*  (android phone version 7 and above). Go in phone info. Find Cell info refresh rate. In default setting it is disabled.  Click and change to immediate. 


Check it in “all cell measurement info”. Did not get? Change Cell info refresh rate to disable and the again to immediate. Do the process of changing till you get Ta value. Take screen shot or jot down on paper.


Finding the connected tower that matches with you screen shot details to verify.


Experiment


Imagine four towers as A, B, C and D. Point the antenna towards A and try to align it properly until you get the highest signal strength. Note it down (cell Id, PCI, and TA value) Do the same for others tower.


For instance:

 
Tower A: PCI- 123, TA-2
Tower B: PCI- 456, TA-5
Tower C: PCI- 789, TA-6
Tower D: PCI- 129, TA-1


Repeat the experiment and do comparison.


Note: stronger signal and closer to tower mean lowest Ta value while higher value gives hints of far distance.


Close Encounter:


If you are not sure then approach at least one tower that has lowest ta value to confirm your guess. And this way you can narrow down your estimation of connected tower.

 
Note: The experiment which I have discussed can help you to identify your guess works in line of sight. It is also important to note that sometimes it will be not foolproof because of the factors like network handover, interference of signal because of obstacles. Again the accuracy also depends on methods and the quality of directional antenna and equipments.


If you are a tech-savvy then assume it like a science experiment and try it once to learn this valuable and enjoyable experience.


Let me know how did you try and your ideas in comment below.









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