Generally speaking, the blind area refers to the blind area of vision, and the blind area of vision refers to the place where people's vision cannot reach.Similarly, the communication blind zone refers to the place where electromagnetic waves cannot reach.
Generally speaking, the blind area refers to the blind area of vision, and the blind area of vision refers to the place where people's vision cannot reach.Similarly, the communication blind zone refers to the place where electromagnetic waves cannot reach.
Causes of blind spots and solutions
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There are many reasons for the formation of communication blind zones. Take the most common mobile phone communication as an example, the current mobile phone communication is basically microwave communication with a frequency between 300 MHz and 300 GHz. Because of the short propagation distance of microwave communication, a large number of signal relay facilities must be built to complete it. This relay facility is the base station.Each base station has a certain range of signal coverage due to its transmission power, antenna orientation, angle and other factors. If a mobile phone is located outside the coverage of the base station signal, it is in a signal blind zone.In addition, when users are in the basement or elevator, they often encounter the situation that the mobile phone has no signal. This blind zone can also be seen as a problem that the base station cannot cover. However, further analysis shows that the reflection, refraction and diffraction of electromagnetic waves used for communication are shielded in these places.The reason for mobile phone communication blind zone in bad weather is similar to this.Of course, the solution to these blind areas is relatively simple, that is, increase the power of the base station or improve the antenna performance. The more direct way is to add more base stations to reduce the blind areas.
In addition to the blind zone of microwave communication, there is also a blind zone in shortwave communication (communication mode with frequency between 3 MHz and 30 MHz).Short wave communication mainly depends on two kinds of electromagnetic waves: ground wave and sky wave. The so-called ground wave is the electromagnetic wave that propagates by relying on the surface medium. It mainly completes short wave short distance communication. The communication distance is generally 20 km~30 km, while sky wave refers to the electromagnetic wave that propagates through the ionosphere in the atmosphere. It is used for short wave long-distance communication. The minimum communication distance is generally 80 km~100 km,Then between 20 km and 80 km, there will be places where both kinds of electromagnetic waves cannot reach, which is called the blind area of short wave communication.The solution to this blind area is generally to increase the ground wave transmission power or select a high elevation antenna for sky wave.
