Chapter 1006 Maximum Rank Distance Code

In fact, Zhang Weiyong’s earliest professional background was communications technology.

However, after he began serving as chief satellite designer in the mid-to-late 90s, his main focus has been on the overall engineering aspect.

Of course, even if he still specialized in his original major, he might not have noticed the paper that proposed network coding in advance.

At the beginning of the 21st century, network communication technology was experiencing an explosive growth. New concepts and technologies were proposed every month, if not every day, and almost every proposer claimed that his or her research could change the world.

Even a well-resourced research team cannot pay enough attention to every result.

Not to mention that China's aerospace research has always been based on stability and is relatively conservative in the application of new technologies.

But if it’s technology that’s already been proven in other industries…that’s another matter.

Therefore, after hearing Chang Haonan's answer just now, Zhang Weiyong immediately sat up straight:

"Mr. Chang, do you also study information theory?"

Data transmission and data compression are both within the scope of information theory.

However, Chang Haonan had no research results in this area before.

But on second thought, it seems that Chang Haonan has expanded into a new research field, which is not surprising...

"Although network coding does belong to information theory, I came into contact with this field purely from a mathematical perspective..."

Chang Haonan explained with a smile:

"You know, I have some knowledge of topology and topological structures..."

"Cough cough cough-"

At this moment, Zhang Weiyong just picked up the glass and took a sip of wine, but was choked by Chang Haonan's words.

A person who solved the Poincare conjecture and created the manifold learning algorithm.

You said you have "some research" in topology?

That's really a lot of research.

After a while, Zhang Weiyong finally recovered a little and waved his hand to show that he was fine, and motioned Chang Haonan to continue the performance... uh... continue talking.

"In short...some time ago, someone asked me to review a paper on nonlinear coding algorithms. I found that there were several very basic theoretical problems in his paper, and it was definitely impossible to pass the manuscript. However, the ideas proposed were indeed very novel, so I took the opportunity to learn about the research background."

After drinking a small glass of red wine, Chang Haonan stopped talking and got a thermos from somewhere and drank water instead.

While talking, he also poured a glass for Zhang Weiyong.

"So you went deeper into it?"

“It’s not research yet.”

Chang Haonan shook his head:

"Things in the field of information theory are easy to understand on a theoretical level, but if you really want to study engineering applications, you need enough time and money. At most, I have a basic understanding of it..."

Now, Zhang Weiyong finally understood.

The other party went through so much trouble just to apply for the project with me and make use of the resources at the aerospace industry.

After all, not to mention that Chang Haonan is only a half-step academician now, even if he is really a big shot who has reached the great perfection realm of academician, it is impossible for him to ask the country to launch a batch of satellites or build an entire dedicated network for technical verification just by talking.

It must rely on some reputation.

Of course, Zhang Weiyong would not believe even a single punctuation mark of such nonsense as “I just learned about it and haven’t studied it in depth yet.”

"Can you elaborate on that?"

He asked calmly:

"I mean, about that specific generalized code."

"of course."

Chang Haonan turned the paper over:

"Let's first simplify a single-source dual-destination multicast directed acyclic network. All point-to-point links in the network have unit capacity. S is the source, T1 and T2 are the destinations, and the rest are intermediate nodes..."

As he spoke, he quickly drew two diagrams on the paper.

"According to the 'Maximum Flow Minimum Cut' theorem, in any directed graph, the maximum flow of information from the input node to the output node is equal to the capacity of the minimum cut set separating the input node from the output node. Therefore, the maximum theoretical transmission capacity of the multicast network in the figure below is 2 bits per unit time..."

"If we follow the traditional model in the left figure, since link cd is the bottleneck of the network transmission and can only transmit 1 bit of information, node c must use the traditional queuing storage method to realize information transmission, resulting in a throughput of only 1.5 bits per unit time for each destination node..."

"In the right figure, node C encodes the received message a and message b... For simplicity, we choose the simplest XOR logic. In short, the destination node can use the received message a or b, as well as the encoded result of a and b, and decode the other unreceived message bit at the same time. This reduces the transmission of one information flow and increases the throughput of each destination node to the theoretical upper limit of 2 bits/unit time..."

"Of course, due to the existence of the Shannon limit, no technology can compress data infinitely. But this is just the simplest case. You and I both know that the more complex the information transmission network is, the greater the gap between the actual throughput and the theoretical transmission capacity, and the more obvious the potential of this type of algorithm will be..."

"..."

"Wait a moment……"

Just as Chang Haonan was about to finish his speech and the piece of paper was almost filled up, Zhang Weiyong suddenly stretched out his hand:

"Mr. Chang, what you just said has a big premise, which is to assume that there are no errors in the transmission process... If any of the nodes on the right has a coding error or a transmission error, then the nodes behind will be infected, causing the error to spread like a computer virus to the entire communication node..."

"Not to mention that such errors are common in normal communications, military satellites also have to consider the electronic interference of the opponent..."

The latter's concerns are naturally justified.

The traditional information relay method sends data repeatedly, which may cause jams and delays, but it can still send the correct information.

However, if something goes wrong in the encoding and decoding process of the new trick that Chang Haonan is planning to use, then the relevant data may be wrong.

Moreover, since errors spread so quickly, it is difficult to figure out exactly which step caused the problem.

In the end, you still have to send data repeatedly, which will only make things worse.

However, facing this question, Chang Haonan acted as if it was a matter of course:

"That's why I said that it still requires in-depth research and technical verification..."

"If I can come up with the ready-made technology right now, why would I need to look for you? I can just go directly to Director Luan..."

"hiss……"

Zhang Weiyong scratched his head and felt that it made sense...

"In short, Mr. Zhang, you have just mentioned that the focus of this technology is, first, to develop a coding algorithm with stronger compression capabilities, and second, to find a way to find an error correction mechanism for the information transmission process. In this way, even if an error occurs during data transmission, it can be corrected at the next node to ensure that the error will not spread between different nodes."

As Chang Haonan spoke, he reached out and tapped the paper lightly for emphasis.

Speaking of this, we have entered an area that Zhang Weiyong is relatively familiar with:

"Like... maximum rank distance code?"

“The MRD code does work.”

Chang Haonan was somewhat surprised that the other party could directly point out the answer he wanted, but his expression did not change much:

"However, current research on MRD is still mainly focused on using it for data encryption, and the error correction function is only incidental... So if you want to achieve strong error correction capabilities, you must develop new MRD code technology."

"I can use Torch Group's resources to conduct some research and testing in the field of small-scale local area networks and aviation relay communications. However, these environments are still too mild compared to satellite communications. We definitely need a... or even a group of dedicated satellites to conduct intersatellite link tests before we can finally determine the feasibility of using it in the aerospace field..."