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Who the hell is Chapter 239

In the MIT Radio Society Activity Room, Professor Murray was staring blankly at the contents of the blackboard without speaking. Pen Fun Pavilion www.biquge.info (《》)

Harvey asked curiously, "Professor?" What's wrong? ”

However, Professor Murray did not seem to hear at all, and he leaned forward, looked at it carefully for a moment, and then immediately picked up the paper of the survey record in his hand, glanced at the notebook, and then at the contents of the blackboard.

At first, his brow furrowed deeply, and he kept comparing the contents of the blackboard with the manuscript paper, guessing why they were arranged in this way.

Harvey shouted once, but when his teacher didn't respond, he didn't say anything more.

He is very aware of Professor Murray's temperament, and when he encounters something of interest, he will become very focused, and automatically block out any distractions from the outside world.

What exactly are those numbers written on the blackboard? How could a professor be so fascinated?

Harvey also felt very strange.

Professor Murray, an authority on wireless communications, is among the most accomplished in the world, and Harvey, as his student, naturally knows this.

At that time, he went to start a business after finishing graduate school under him, and the field of entrepreneurship is also closely related to wireless communications, and he came back this time to represent the company, and wanted to hire professors to give them honorary technical guidance, and strive to establish a close cooperative relationship with MIT, as one of the reserve bases for R&D talents.

Intrigued, Harvey walked over and looked at the blackboard.

At first, he was a little confused when he saw the data, after all, he had not been involved in the project, but when he saw Professor Murray from time to time trying to match the data in his notebook with the data on the blackboard, he suddenly understood a little.

"These numbers on the blackboard are the satellite communication channel coding chips that the students measured?"

Thinking about it this way, Harvey also looked at it seriously.

The contents of the blackboard had completely captivated Professor Murray. 《》

He found that all the data on it was based on the observation data in his hand, and then selected some channel code chips and wrote them on the blackboard.

It is not a simple excerpt, but a selection, and at intervals, a continuous string of numbers is picked out.

These numbers are then formed into a matrix, which is then transformed into another matrix.

Next, the obtained matrix is calculated with another selected matrix, and then a matrix that is magnified many times is obtained.

Murray didn't know why he had picked the data, but he was shocked to see the results of the calculations on the blackboard!

Because, at this point, he can see some of the patterns contained in these numbers.

"This is a channel denoising algorithm!"

Having worked with radio communications and satellite communication coding for a long time, he was naturally able to understand what this process really meant, and it was because of this that he was very shocked!

You know, in satellite communication, the most critical thing is the denoising algorithm, because the satellite is usually thousands of kilometers away from the earth, and it is working with batteries, the transmission power is not very large, it is sending signals to the earth, and it will have to pass through the thick ionosphere and various artificial shields, and when it reaches the earth, the signal power will be attenuated to a very small one, and even directly drowned in the background noise.

The antenna on the earth can still receive weak signals, but whether they can distinguish these signals is a great problem.

For example, they use the 1.8-meter dish antenna of the monitoring station, which can actively amplify the received signal by 300 times, but this level of strength still cannot meet the requirements.

These signals must also be treated specially.

First of all, the signal coding technology on the satellite cannot use ordinary coding methods, but must use a technology called "spread spectrum communication".

For a long time, spread-spectrum communication technology has been mainly used for military secret communications and electronic countermeasure systems, so this technology is extremely secret and cannot be accessed by ordinary people. (《》)

Due to Professor Murray's special status, he is qualified to access this technology, but he does not know who the real inventor of this technology is.

What Professor Murray does know is that this technology was first seen in the mid-fifties, when the U.S. Navy gave Hoffman Radio a patent for the production of sonar buoys and the radios that accompany them for two-way communication between the aircraft and the sonar buoy equipment.

In that patent, however, the inventor's name was erased from the file, the information given was kept in extreme secrecy, and Hoffman Radio did not know who the patent was.

Spread spectrum communication technology is indeed a very unexpected but powerful technology.

It has many advantages, such as good anti-interference, strong concealment, and can improve the utilization of frequency bands.

Conventional communication coding technology is called "narrowband communication technology".

Transmission of any information requires a certain bandwidth, for example, the bandwidth of voice information is about 20Hz~20000Hz, and the bandwidth of ordinary TV image information is about 6MHz.

In order to make full use of frequency resources, the transmission bandwidth is usually compressed as much as possible. If the phone is a baseband transmission, people usually limit the bandwidth to about 3400Hz.

However, spread spectrum communication technology is the opposite, it belongs to broadband communication technology, and the ratio of the usual spread spectrum signal bandwidth to information bandwidth will be as high as hundreds or even thousands of times.

In this technique, length is exchanged for accuracy. By lengthening the length of the message and then using a specific encoding and decoding algorithm, it is possible to achieve accurate communication with very little power.

For example, there is originally only one signal, representing the code "1", but in order to prevent this signal from being completely canceled out by other interfering noise in space, it is usually necessary to expand this code to dozens or even hundreds of bits.

In this way, even if a certain number of coded fragments are missing, it is irrelevant to the whole, and after decoding, the received part of the coded fragment can still be restored to "1".

When the signal is on the satellite, it must be encoded and spread spectrum according to certain rules, which is equivalent to encrypting the data, inserting a lot of specific information on the original information, and making its code chip become N times the original number.

However, after reaching the ground, it is necessary to perform operations in the opposite direction and decode.

This process is like getting out of bed and dressing in the order of underwear first and then outer clothes, and when you go to bed, you have to take off your clothes in the order of outer clothes first and then underwear.

However, it is not just someone who asks it to take off its clothes, but to give him a decoding sequence, which is equivalent to a key, and uses this sequence to carry out algorithm operations to finally restore the original appearance.

However, this key is confidential and usually won't be told to you. The purpose of the project that Professor Murray is working on is to monitor the satellites of the Union of Su or Mei countries, and then calculate the key through a large amount of data calculation.

As long as you get this key in your hands, then it means that this satellite has been cracked.

However, the process is very complex and difficult. The project has been in the works for more than a year, and Professor Murray has built dozens of mathematical models for it, but he still hasn't touched the edge.

However, today, he saw the dawn of the key on the blackboard in the activity room!

The matrix of numbers on the blackboard shows that it seems that after a few matrix operations, the background noise has been greatly eliminated, that is, the signal has been restored to a certain extent.

If you continue, you will probably be able to restore the real code!

At this time, Professor Murray had already finished reading the contents of the blackboard, and the last number matrix was only half, and all the back had been erased.

"How did you wipe it off?" Professor Murray exclaimed, "Why wipe it off! Who rubbed it! ”

He was seeing the key point, but found that there was no more, this feeling, as if he and his wife were ooxx, about to reach the apex, suddenly by a basin of ice water poured from head to toe, about to spray thin passion to the freezing point in an instant.

The second half, which was the most crucial part, was erased, which made Professor Murray feel very sorry and angry at the same time.

Professor Murray's eyes widened, expecting to see what was still behind from the faint traces left on the blackboard, but his expectation was disappointed, and the other party wiped it thoroughly, leaving not even a slight trace.

Faced with this situation, he simply has a tendency to go crazy.

"Professor, these contents ......" Harvey saw that the professor came back to his senses and hurriedly spoke.

Before he could finish speaking, Professor Murray said directly: "Harvey, don't you Qualcomm want to develop a commercial product in the field of satellite wireless communication?" That's the key! ”

"What?" Harvey's spirit suddenly lifted when he heard this, and then he was a little surprised!

He knew that his teacher was not the kind of person who spoke his mouth, and he said yes, and that was for sure.

In fact, he came this time for another purpose, that is, he hoped that Professor Murray would be able to popularize the spread spectrum communication technology he had mastered.

However, Professor Murray has not nodded to this, because this technology is classified technology, he signed a non-disclosure agreement, although the government does not seem to be as strict about this piece as before, but there is no clear document that can declassify this technology.

"Who wrote these things on the blackboard?"

Professor Murray did not answer Harvey's words, but searched his mind for possible candidates.

First of all, a member of the MIT Radio Society, Bailey? Sophie? No, none of them have reached that level yet.

Other professors in the field of wireless engineering?

Professor Murray searched around in his mind, but he couldn't find anyone who could match the number.

At MIT, he doesn't know anyone better than him in this area.

Professor Murray revisited the previous content several times, but he still couldn't see how the rectangles on the blackboard came from.

The author who wrote this content omitted too many steps in between, as if the other party had just written the answer here.

Who the hell is it?