When you open your own mobile phone WiFi, you may find that Her he wrote 5GHz. Is there a 5G era without money? Classmates who are unknown, may be just like this: "What? 2.4G and 5G? I am using 4G now! 5G is not commercially available?"
In fact, we often say 4G, 5G G, is the first letter of English word generation, referring to the first generation of mobile communication technology, and 5GHz WiFi is neither usually said, and it is nothing to do with Generation. It is the signal frequency of the WiFi. As another example, friends who play the radio are familiar with "FM86.4MHz" and so on, 86.4MHz means the frequency of radio used by this radio you listened.
So is the communication frequency? Why is the fiber can provide so fast network speed, the wireless signal is not?
The X-rays of microwaves, mobile signals, lights, and even hospitals in our lives are electromagnetic waves. The only difference is that the frequency is different. The communication in the space is in the figure, the electromagnetic field is based on periodicity. Change, temporary waveform of one cycle is called a unit, and the speed of the electromagnetic field is the speed of light, the frequency is the number of units passing within a second. The amount of physical quantity is wavelength, that is, the length of the electromagnetic wave, obviously the speed = frequency × wavelength, because the light speed is certain, the longer the wavelength, the less the unit can pass in one second.
The higher the frequency (the more units passing by the unit), the higher the energy carrying, the more wear penetration, such as X-rays, the frequency is approximately at 30PHz (3 after 16 zero) to 30EHz (3) 19 zero) - reiterated that 1Hz has passed a unit in a second; low electromagnetic waves, it has a good ability to circumvent the obstacle to continue to spread, such as the previous broadcast signal, crossing the big mountain river To your radio, 86.4MHz (MHHz) is the radio frequency used by the radio you listened.
What does the FM mean? In fact, like a note cannot write a song, the electromagnetic wave of a single frequency cannot be transmitted, just like the GIF above, you see that it flows tone, there is no fluctuation. To pass the information, you must have a frequency alternating change. If the musical notes are alternating, you will know which song is, this is the modulation technology.
Simply, if a boys want to express love for a girl when they are class, his mood is the information he wants to send. It can't speak in class. It can't take the heart, and the girl can see it. It's just a face of a boys. At this time, the boy can't face no expression (equivalent to a single frequency), he must modulate his mood on the face, crowding, eyebrows (equivalent to frequency changes), send it to the female classmate.
Let's take a look at how the mobile phone is doing this: This boy has sent a "I love you" on WeChat. Because the computer can only use binary expressions, each Chinese word is allocated a one-piece binary. Encoding, such as encoding with GB2312, "I love you" is translated into an electrical signal of "1100111010010 101100001011110 1100010011100011". what does this mean? That is to say, "1" will generate a string current, "1" corresponds to a current, "0" corresponds to no current, such as "01011010" The waveform of the string signal is the following:
The same waveform like this string password is modulated on the electromagnetic wave emitted by your phone (that is, the 5GHz electromagnetic waves displayed on the phone, 9 zero behind 5), for example, this (can have different modulation methods, as long as both parties The agreement is consistent, according to the same method, modem, such as FM FM):
After the base station conversion to the frequency of higher frequency, generally in 200thz (ie, 14 zero), the fiber is transmitted to the base station near the other side, and then the base station sends 5GHz electromagnetic wave to the other party's mobile phone, and then restore this phone The sequence of string 0101 is translated into "I love you", so that these three words are displayed on the other mobile phone.
Therefore, if you want to transfer information, there must be a frequency change, and the electromagnetic wave varies within a frequency range, which is the frequency band. At present, there are mainly two frequency bands used in WiFi, namely 2.4GHz and 5GHz. Take 2.4GHz as an example, the frequency range is 2.4-2.4835GHz, a total of 83.5MHz frequency resources (because the electromagnetic wave in life is too much, do not affect each other, try to use different frequencies, so frequency is very valuable resources Some frequency bands are not allowed to use it), this 83.5MHz is called bandwidth, that is, the width of the frequency band.
I want everyone to have questions in my heart: Usually Internet access, the carrier tells the bandwidth to me not this? What are you saying about 10m, 100M bandwidth, refers to the fastest download speed duck. Don't worry, in fact, this is a matter. Because the Nyquist Limit tells us that the limit speed of the information that can transmit information is equal to twice the system bandwidth. This means that the bandwidth of the 2.4GHz bandwidth is 83.5MHz, then the speed limit it transmits data is 167Mbps. Note that this is theoretical limit speed. The actual equipment is hard to achieve so high, so if you use the 2.4GHz band WiFi, the highest bandwidth is 100m, if the operator tells you more than 167m, then absolute Just flicking you!
Now know why frequency is a valuable resource? A certain bandwidth frequency band can only support that high rate, so the frequency of the communication system is now more, so it is more likely to obtain large bandwidth, such as the frequency band of 5GHz is actually 4.910GHz ~ 5.875GHz frequency range, total 900 More M's bandwidth, the advantage is obvious! As for the previously mentioned fiber, the frequency is so high, and it is conceivable that the bandwidth to be transmitted is much higher than the WiFi. The maximum rate of single fiber currently is 57.6Tbps, enough to support the people throughout the country. The root fiber is called, knowing that the diameter of a fiber is only less than 10 microns!
Summary, 5G in WiFi refers to signal frequencies of the frequency band at 5GHz (of course only the 802.11ac protocol is true 5GHz WiFi), and the 3G, i.e., the third generation of mobile communication technology, is used 1880MHz-1900MHz And 2010MHz-2025MHz frequency band, 4G is 1880-1900MHz, 2320-2635MHz, 2575-2635MHz frequency band; and today's 5G uses 450MHz-6GHz band and 24.25-52.6GHz band, this frequency band is far more than previous The frequency band of wireless communications is, and it will provide a wide range of bandwidth. Of course, everything is good, if I said, the higher the frequency of electromagnetic waves, the more I don't have the ability of the radio dozens of megahertz, so the arrival of the 5G era, means needed More base stations are transferred to the signal, because the 5G signal of your phone can no longer be transmitted far.
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