Source: ZTE Documents
Author: ZTE Documents
Internet of Things Think Tank reprinted
Guide
Communication engineers guard the world's communication network all the time, and in every important examination, there are many staff members who silently guard the candidates.
College entrance examination, public examination, examination and research, teaching qualifications, various qualification examinations... The figure of all kinds of examinations is simply from the beginning of the year to the end of the year. I don't know if you have considered how to prevent candidates from cheating in so many important examinations?
In the news after the big exam, we often see a few hot-headed candidates who want to use various "crooked ways" to challenge the fairness of the exam.
For example, the spectacle watch "set", through which the candidate can see the text on the watch screen.
For example, an "eraser" that shows the answer.
Another example is the button-type camera, the cheat pen and so on. All kinds of high-tech cheating tools are emerging in an endless stream, and even high-end cheating tools imported from abroad have appeared in the examination room, using spy equipment.
We haven't seen these tools, but we're shocked. As a communication siege lion, Xiaobian only wants to tell you here: In fact, these crooked and evil ways cannot escape the eyes of the invigilator.
Some test takers think that by turning off their phones and placing them in "well-designed" places like shoe soles (you know), they can escape the scan of the metal detector wielded by the proctor at the entrance of the exam room and successfully bring their phones into the exam room.
As everyone knows, if the mobile phone has no signal, even a brick is not as good.
Why? This has to start with the working principle of mobile communication.
How mobile communication works
As a mobile communication device, the mobile phone needs to establish a connection with the nearby base station when communicating, and then access the core network to find the communication destination.
In the above process, all information is carried and transmitted through electromagnetic waves. The electromagnetic wave band used in mobile phones is related to the standard used in mobile phones and the operators where they are located. But overall, the electromagnetic bands used by the three operators are distributed in the 850-4900MHz range. If you want to block the mobile phone signal in the examination room, it is impossible to make the 2G/3G/4G/5G base station near the examination room not work, otherwise all the communication equipment in this area cannot communicate normally. That's the only way to block the mobile phone signal in the examination room.
When it comes to shielding mobile phone signals, the first thing that comes to mind is definitely metal shielding, that is, the mobile phone is placed in a closed metal box to block the propagation of electromagnetic waves through metal. But it is obviously impractical to make all the classrooms in the examination rooms closed in metal.
So what to do?
It is very simple, only a small mobile phone signal jammer is needed to block all mobile phone signals in the test room.
The principle of blocking mobile phone signals
The mobile phone signal jammer scans the low frequency band of the forward channel (from the base station to the channel of the mobile phone) at a certain speed during the operation process, and forms interference in the process of receiving the message signal of the mobile phone, so that the mobile phone cannot detect the normal data sent from the base station, so that it cannot establish a connection with the base station, showing no signal and no service.
For example, when the mobile phone communicates with the base station, the signal jammer is like a trickster, deliberately creating noise around you, and the noise signal is so loud that the mobile phone cannot hear what the base station says, and the base station cannot hear what the mobile phone says. In fact, this is not to block the mobile phone signal, but to make the signal emitted by the mobile phone obliterate in a large number of noise signals, so as to achieve the purpose of interference.
At present, the mobile phone signal jammer used in the examination room is full-band, which can interfere with all the frequency bands of the three operators 2G/3G/4G/5G, and the WIFI signal and Bluetooth signal can also be completely blocked.
Therefore, it is certainly not feasible for candidates to cheat through their mobile phones. But the frequency band of electromagnetic waves ranges from a few Hz to tens of hundreds of GHz, and each segment may be used as a signal for communication. So, will there be some special frequency bands that will be used in the examination room?
Other wireless communication tools
Surprisingly, it is true that some radio communication tools use dedicated frequency bands.
You must have heard of people who sell college entrance examination answers, they have such equipment in their hands. The operating frequency bands of these devices are selected outside the range of frequency bands covered by the mobile phone jammer. During the exam, illegal candidates use mini headphones to listen to the exam answers. The signal receiving module of this mini headset is hidden in the spectacle frame.
However, even spectacle frames are not "extralegal land". For this special radio communication tool, the examination room is specially equipped with a monitoring vehicle equipped with a radio monitor for real-time monitoring of radio wave signals of unknown origin.
Because electromagnetic waves have the characteristics of "near large and far small", by constantly moving the detection vehicle, the monitoring equipment can locate the location of the signal transmitter according to the distance and the strength of the signal, and capture the answer sender on the spot.
Nowadays, drones have also appeared in the examination rooms of various large-scale examinations, which can locate signals faster.
Various large-scale examinations are not only a stage for the knowledge competition of Guangdong University students, but also a contest between cheating in the communication circle and anti-cheating technology. Just as the so-called magic is one foot high and one foot high, although various cheating methods emerge in an endless stream, anti-cheating technology is superior. There is no such thing as a good or bad communication technology, but some people use them in the wrong place.
Just as communication engineers guard the world's communication network at all times, there are many staff members who silently guard the candidates in every important examination. With the fair environment built by these guardians, please focus on the exam papers in front of you and write down the unforgettable answers on your life journey with real talent!