Chapter 1006 Maximum Rank Distance Code
In fact, Zhang Weiyong’s earliest professional background was in communication technology.
However, after he began to serve as satellite chief engineer in the mid-to-late 1990s, his main focus was on the overall engineering aspect.
Of course, even if he is still specialized in the original major, he may not have noticed in advance the paper that proposed network coding -
At the beginning of the 21st century, we are catching up with network communications. In the era of technological explosion, new concepts and new technologies are proposed not to mention every day, but at least every month, and almost every proposer claims that their research can change the world.
Even a research team with abundant resources cannot pay enough attention to every result.
Not to mention that China’s aerospace research has always been focused on stability and is relatively conservative in the application of new technologies.
But if it is a technology that has been proven in other industries... that is another matter.
Therefore, after hearing Chang Haonan’s answer just now, Zhang Weiyong immediately sat up straight:
“Mr. Chang still has research on information theory?”
Data transmission and data compression are both categories of information theory.
Chang Haonan has not had any research results in this area before.
But after thinking about it, it seems that Chang Haonan has expanded into a new research field, which is not very surprising...
"Although network coding does belong to information theory, I have come into contact with it. I came to this field purely from a mathematical perspective..."
Chang Haonan explained with a smile:
"You know, I have done some research on topology and topological structures..."
"Cough cough cough——"
At this moment, Zhang Weiyong just picked up the cup again and took a sip of wine. I was directly choked by Chang Haonan's words.
A person who solved the Poincaré conjecture and created a manifold learning algorithm.
Say that you have "some research" on topology?
That's really well researched.
After a while, Zhang Weiyong finally calmed down and waved his hand to express that he was fine, and signaled Chang Haonan to continue performing... uh... keep talking.
"In short...some time ago, someone came to me to review a paper on nonlinear coding algorithms. I found that there were several very basic theoretical issues in his paper, and it would definitely not be approved. , but the idea proposed is indeed very novel, so I stopped by to learn about the research background.”
Chang Haonan did not continue after drinking a small glass of red wine, but got a thermos from nowhere. Drink water instead.
While talking, I also poured a glass for Zhang Weiyong.
"So you're going to study it in depth?"
"Research is not something we can talk about yet."
Chang Haonan shook his head:
"Things in the field of information theory, theoretical level Fortunately, if you really want to study engineering applications, you will need enough time and funds. At most, I can understand it..."
At this time, Zhang Weiyong finally understood.
The other party went around in such a big circle because he originally wanted to apply for the project with him, and then take advantage of the resources at the Aerospace Port.
After all, not to mention that Chang Haonan is only a half-step academician now, even if he is really a big brother in the Dzogchen realm of academicians, he cannot let the country build a group of satellites just by talking, or Build an entire dedicated network to perform technical verification.
You must rely on some names.
Of course, Zhang Weiyong would not believe such nonsense as "I just learned about it and haven't studied it in depth yet".
“Can you tell me more?” He asked calmly:
"I mean, about that specific generalized encoding."
"Of course."
Chang Haonan turned the piece of paper to the back:
< br>"We first simplify a multicast directed acyclic network with single source and dual sinks. All point-to-point links in the network have unit capacity. S is the source, T1 and T2 are sinks, and the rest are intermediate Node..."
As he spoke, he drew two schematic 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 that separates the input node from the output node, then The maximum theoretical transmission capacity of the multicast network in the figure below is 2 bits/unit time..."
"If you follow the traditional model in the figure on the left, since the link CD is the bottleneck of the network transmission, only 1 bit information, resulting in node C having to use the traditional queuing storage method to realize information transmission, resulting in the throughput of each sink node being only 1.5 bits/unit time..."
"In the picture on the right, node C Encode the received message a and message b... For simplicity, we choose the simplest XOR logic. In short, the sink node can use the received message a or b, as well as the encoded results of a and b, to simultaneously interpret Another unreceived message bit, thus reducing the transmission of an information flow and increasing the throughput of each sink node to the theoretical upper limit of 2 bits/unit time..."
"Of course, due to Due to the existence of Shannon limit, it is impossible for any technology to 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 actual throughput and theoretical transmission capacity. , the potential of this type of algorithm becomes more obvious..."
"..."
"Wait a minute..."
Just when Chang Haonan was about to reach the end of his story and the paper was finally almost full, Zhang Weiyong suddenly stretched out his hand:
"Mr. Chang, what you just said is based on the assumption that the transmission process is error-free... If any of the nodes on the right has a coding error or a transmission error, then the subsequent nodes will Be infected, causing errors like computer viruses, eventually spreading to the entire communication node..."
"Not to mention that such errors are very common in normal communications, military satellites also need to consider the opponent's electronic interference... …”
The latter's concerns are certainly justified.
The traditional information relay method repeatedly sends data. Although it will cause lags and delays, the correct information can still be sent.
But for this new trick that Chang Haonan is planning to do, if something goes wrong in the intermediate encoding and decoding process, the relevant data may be wrong.
Furthermore, because errors propagate so quickly, it is difficult to figure out which step caused the problem.
In the end, you still have to send the data repeatedly, which will only become more stuck.
However, when faced with this problem, Chang Haonan took it for granted:
“That’s why I said that in-depth research and technical verification are still needed...”
"If I can come up with ready-made technology now, then there is no need to go to you. I can just go to Director Luan directly..."
"Hiss..."
Zhang Weiyong I scratched my head and thought it made sense...
"In short, Mr. Zhang, you just mentioned that the focus of this technology now is to develop encoding algorithms with stronger compression capabilities. The second is to find ways to find an error correction mechanism for the information transmission process, so that even if the data is being transmitted If an error occurs, it can be corrected at the next node to ensure that the error will not spread between different nodes."
Chang Haonan said, reaching out and tapping the paper lightly. Show emphasis.
When it comes to this, we enter a field that Zhang Weiyong is relatively familiar with:
"For example...maximum rank distance code?"
"MRD code is indeed possible."< br>
Chang Haonan was a little surprised that the other party could directly point out the answer he wanted, but there was no change in his expression:
“However, the current research on MRD is mainly focused on using it for data encryption and error correction. The function is just incidental... So if you want to achieve strong error correction capabilities, you must develop new MRD code technology."
"I can use the resources of the Torch Group in small-scale local area networks and aviation. Some research and testing have been conducted in the field of relay communications, but these environments are still too mild compared to satellite communications. It will definitely require a... or even a group of specialized satellites to conduct inter-satellite link testing before final determination can be made. The feasibility of being used in the aerospace field..."
(End of this chapter)