Chapter 1695: ADSL

In later generations, many people will complain that when playing games, the Internet speed card is stuck, and the result is lost. However, if you go back 20 years, look at the Internet in this era, they should feel at ease.
Needless to say the game, just a picture, you need to wait patiently, you can go out for a meal, when you come back, it is estimated that the picture will come out.
At the same time, the picture is quite bad, because the highly compressed picture has a lot of distortion when it is restored.
If it is a high-guaranteed picture, a picture, how many megabytes are at every turn, and how long will it take to transmit with a cat of more than ten K? For a few minutes, this is just the theoretical speed. Everyone should know that it is good to have a broadband of 100 megabytes and a maximum speed of 10 megabits. A cat that is called 14.4K can have a speed of 1K. It takes tens of minutes to transfer a photo. As for the video? Can you accept the slap of the big window, and then move the picture on it once an hour? Can this be called a video?
There is no need to consider any job, and job is not a panacea. Although he is engaged in mobile communication switches, now, mobile communication switches are also in the 2G era.
If you use an image metaphor, in the 2G era, you can only look at Cangkongkong.TXT, which is a text file. In the 3G era, you can see Cangkongkong.jpej, which is also a picture. When it comes to 4G, you can see Cangkongkong. AVI is video.
The equipment in Ren Gong's hands is for the mobile communication system, and can also be used to transform the current telephone network, such as program-controlled switches. In short, the 2G era can only exchange text and other data.
Therefore, chat rooms in this era are very popular, because everyone can only post text.
(Hua Xiong also misses that era. It was the golden age to engage in online literature at that time. Now, Kuaishou Douyin has far surpassed online literature.)
Qin Guan wanted to make a video, it was definitely a great leap forward.
Qin Guan knew that he had made a big joke. The 14.4K cat has been developing, but the technology is quite slow. It was not until the 1990s that the 56K cat system was gradually developed. It was not very stable. Dropped.
now what?
It is very advanced in computer technology, and it has also begun to make strides in network technology. Domestic operators have begun to engage in this kind of personal network. The charges are quite high, definitely more expensive than mobile phones, and it is just getting rich. Can be owned by rich talents.
So, if I want to make a video call with my family, is it impossible?
Of course not. Now, if this is the case, it also means that a major breakthrough in network technology is coming soon. This is a broadband cat.
The phone line is still the same phone line, but the transmission speed has increased by hundreds of times, and it has directly stepped into the mega-level. It is used for video calls and online movies. There is absolutely no problem!
Now, laying optical fibers on a large scale is what the military can do. In terms of civilian use, it is still impossible to lay it out, and fiber to the home is even more impossible. After all, this requires a huge investment in infrastructure, and the domestic telecommunications industry still cannot afford it. There are not enough users. Enterprises, there are only large enterprises. Only one connection is possible. As for various small businesses, those bosses are definitely more willing to take a large mobile phone and deliberately display it when discussing business.
"It seems that the development of computer networks is still inseparable from our Hanxin Technology Company." With a smile on Qin Guan's face, he converted from the embarrassment just now, everyone knows that Qin Guan has a plan now. Up.
"Ms. Qin, are you going to introduce new black technology to us?" Many people gathered around, familiar faces, such as Qiu Xiaojun, now he is more mature, and he is already a mature man. Up.
"Everyone, what's the reason for the slow internet speed now?" Qin Guan finally started to act as the tech emperor in front of this group of technologists. This feeling was so beautiful.
"Because our data is high-frequency signals, but telephone lines can only transmit low-frequency signals, so the speed cannot be increased during the transmission." Someone immediately responded.
Yes, this is a weakness of the ordinary cat. When it transmits on the line, it uses audio signals. The rate of this signal cannot be high. Moreover, it is an analog signal, so there will be many problems, such as loss. Signal and so on. "So, if we want to greatly increase the transmission speed, we need to change everything." Qin Guan said: "I am here to only provide ideas, and the specific implementation is up to everyone."
"Mr. Qin, please tell me." While Ni Gong said, he began to take out his notebook and record seriously.
"Our telephone line is twisted pair. This telephone line can not only transmit low frequency, that is, the frequency band below 4KHZ, it can also transmit higher frequencies. We simply divide the transmission signal of the telephone line into Many frequency bands, for example, from 4kHz to 1.1MHz, such a huge and wide frequency band is divided into 256 sub-bands with a bandwidth of 4.3125kHz."
The above can also be used, the more you go up, the faster it will be.
"In this way, the previous telephone lines do not need to be discarded and can carry more signals. The frequency band below 4kHz is still used for traditional telephone services, and other frequency bands can be used to transmit digital signals." Qin Guan said: "Calling and surfing the Internet. , Do not affect each other, each does its own thing. However, we'd better distinguish the latter frequency bands."
Qin Guan is quite familiar with ADSL. In that parallel time and space, when he had a network in his home, he first used this telecommunication ADSL modem.
"For example, we use 138KHZ as the dividing line. The frequency band from 20KHz to 138KHz is used to transmit uplink signals, and the frequency band from 138KHz to 1.1MHZ is used to transmit downlink signals."
"This downside is occupied too much, right?" someone asked immediately.
"Yes, think about it, everyone, when individual users go online, do they download more or upload more?" Qin Guan asked rhetorically.
ADSL, the full name is Asymmetric Digital Subscriber Line. Downstream and upstream are different. After all, most users are mainly downloading, so that they can download more smoothly. Isn't that better?
According to technical data, even the original ADSL technology can reach a very high data transmission rate.
The uplink is 640kbps and the downlink is 8Mbps. In this way, there is no delay in watching movies or anything. At the same time, although the uplink seems to be very low, the speed is also increased by forty times compared with an ordinary 14.4KB ordinary cat. Make a video call, absolutely no problem!
"Our plan is to achieve a data transmission channel of 8M downlink and 640KB uplink." Qin Guan said, "Do you have confidence?"
After speaking, the scene was silent.