How does cellular communication work?
Many people think about how cellular networks work, what happens when we press the call button? When calling each other, the often called subscriber is not only within the same city, but even on another continent. How does cellular communications work?
PRINCIPLE OF ACTION OF CELLULAR COMMUNICATIONS
In most of the territory of our country, mobile communications equipment is located, it is called base stations. They are clearly visible in open areas – in the fields between settlements. In the city, they are often placed on the roofs of buildings. The base station is able to pick up the signal from the smartphone at a distance of up to thirty-five kilometers, the contact between the towers is carried out by means of a special service or voice signal.
The active development of mobile communications has created a problem of limiting the frequency, namely, the working channels located close to each other began to overlap, creating interference. For many years, an idea has been proposed on which a certain service area by a mobile operator should be divided into cells. Each cell is served by a special transmitter, assuming a fixed frequency range and range. Such a system eliminates interference when using the same frequency, but in a different cell. To divide a certain area into equal sections, the most optimal is a figure with six angles resembling a bee honeycomb, since an antenna with a pie chart installed in the center of the cell will provide free stable access to all points of the cell. All cells have their own frequency band and serving base station. Adjacent cells do not use the same frequencies, thereby eliminating crosstalk and interference, and vice versa, cells located far from each other can use identical frequencies.
HOW BASE STATIONS WORK
When the smartphone is in standby mode, its receiving mechanism scans the channels of the system. If the user is about to make a call, he dials a number and the device automatically finds a station that is closer to him and sends a request to allocate a voice channel. Those base stations that receive a response signal redirect their data to the switching center, where the conversation is switched to the nearest station to the called party with a higher signal level. The switching center also determines which mobile operator is being used by the called subscriber.
In the event that a call is made between subscribers within the same network, then the location of the called subscriber is immediately identified in the switching center, and it does not matter where the person is: at home, in transport or on a business trip to another country. The physical location of the subscriber in no way interferes with the connection and making the call. If the switching center receives information that the called subscriber is using an operator of another communication, then the request will be sent to the switching center of another network. In general, it turns out that the system is quite simple, and how cellular communication works is understandable. The interesting question remains, what does the device of the base station look like: here everything is simple – these are just a few metal pedestals located on the roofs of buildings and for their uninterrupted operation high-quality ventilation is enough.
COMMUNICATION STABILITY PROBLEMS
It is clear that at the time of dialing, the device occupies an unoccupied channel with the highest possible signal level. But, if during the conversation the subscriber begins to move away from the base station or the conditions for the expansion of radio waves deteriorate – all this will adversely affect the connection and its quality. It is logical that its improvement occurs after subscribers switch to other, more stable, communication channels.
Each base station has an antenna, consisting of several elements, the so-called sectors, responsible for “their” area. The vertical component of the antenna is responsible for communication with mobile devices, the round – with the controller. Considering that one station most often consists of 6 sectors, and each of them is able to receive at least 70 calls, after some simple calculations it turns out that serving more than 400 subscribers at the same time is not a problem for it. Such performance is often enough. But, there are also emergency situations when all the subscribers of all mobile operators start calling, for example, on big holidays (New Year’s Eve), and the base stations just can not cope – interruptions and interference begin. Nevertheless, for an average load of six sectors is more than enough.
It should be noted that depending on the area of the settlement and population density, mobile operators establish base stations with different frequency ranges:
• 900 MHz. The installation of such a station is more appropriate in small towns, urban-type settlements, etc. In this mode, the base station covers an area with a radius of about 35 km, or even 70 km if it currently serves a small amount.