Chapter 1012 Communication Relay Platform
Although Chang Haonan wrote in the document that he relied on "ground stations" for communication relay, this was only adopted to make it easier for superiors and comrades in brother units to understand. It's just a general statement.
In fact, the node responsible for communication relay does not need to stick to the formality.
After all, under the premise that low-orbit relay communication constellations will be planned in the near future, spending a lot of money to build expensive fixed communication sites in border and coastal areas is a waste of time. Waste of resources.
To put it another way, even if this is not considered, the fixed relay station itself is a relatively fragile target in wartime, and it is easy to be taken care of by imaginary enemies.
Therefore, after the project was officially approved, Chang Haonan actually invested in research and development, mainly on two platforms.
The first is the stratospheric airship, which was developed under the leadership of Zhejiang University and has performed brilliantly during embankment operations.
This is already a fairly mature technology, and Zhejiang University has not stopped upgrading and improving the equipment in recent years.
In addition, its original design purpose was to serve as a communication relay platform, which can be said to fully meet Chang Haonan's needs.
There is no need to make major changes to the overall architecture, as long as the encoding-decoding function is added to the original function of simply receiving, storing and forwarding.
Since its floating height is more than 20,000 meters, which is much higher than the general flying height of early warning aircraft, it can be used as a simulated satellite unit during testing to test the antenna performance of the upper hemisphere of the aircraft.
Of course, because the distance is closer, the signal strength and signal-to-noise ratio are definitely still much stronger than real space-based communications.
Moreover, the relay station itself is relatively static and cannot completely restore the scene of space-based communications.
This is why Chang Haonan had to ask Zhang Weiyong to build the satellite.
The other platform is a vehicle-mounted ground communication relay station.
Compared with stratospheric airships, its functions are weaker and it is subject to stronger clutter interference, but it can achieve "communication while moving", that is, communicating while moving.
It is used to test the antenna performance of the lower hemisphere, while simulating the constant motion of the satellite platform and the weak signal characteristics.
The vehicle chassis does not require additional research and development. It can be modified directly with the SX2190 truck, which has a huge number of copies.
If necessary, you can also move it directly to other models.
As for the research and development of the entire vehicle-mounted relay station, Chang Haonan neither chose the 14th Institute of Electrical Engineering, which is responsible for the research and development of Air Police 2000, nor the Space Technology Research Institute, which is responsible for satellite research and development.
Instead, he went to the 54th Institute of Electrical Engineering in Shimen.
Or strictly speaking, it was the leader of the Electronic Technology Group who took the initiative to recommend them to Chang Haonan.
Because the 54th Institute is currently developing a series of satellite communication/scatter communication vehicles for military communication units and emergency rescue units.
Although it is not completely consistent with Chang Haonan's needs, the similarity is at least 90%.
And the technologies are similar.
Chang Haonan had no objection to this.
The technical difficulty of the hardware level of this communication relay vehicle is not high, and the core algorithm of the software is still developed by him, so it does not require that the partner must have strong capabilities.
As long as the execution ability is strong enough and you have the ability to learn.
Besides, the 54th Institute, as a network communications research institute, is not an ordinary person.
So, about a month after the QC300 project was completed, one day at the end of May, Wu Wei, the head of the general department of the 54th Institute of Electrical Engineering, led a core team of four people to personally I went to the capital and found Chang Haonan.
The latter did not beat around the bush and stated his requirements straightforwardly.
......
In Chang Haonan's office, Wu Wei looked at the densely marked technical information in his hand and showed a somewhat embarrassed expression:
"Mr. Chang, use Ground vehicles serve as communication relays for aircraft... It is technically not difficult to achieve, but..."
He said while carefully considering his words:
"But considering the size and power limitations of the vehicle platform, the range may not be particularly optimistic..."
Communication has always been about standing high and transmitting far, so most of the ideas are using Aircraft in the sky serve as relays on the ground.
This is the first time Wu Wei has heard of a reverse request in his life.
“It doesn’t matter, this is the effect I want.”
Chang Haonan’s answer was even more shocking:
"If the transmission range is too wide, it will be inconvenient to test the theoretical throughput performance of the multi-hop network."
Looking at Wu Wei, whose eyes almost popped out, he had no choice but to continue explaining:
"This kind of test, whether for confidentiality reasons or to reduce the impact on normal production and life, must be far away from the city, so the test area will most likely be placed in the northwest, with a maximum range of two to three hundred kilometers. I have to make sure that it goes through at least three jumps, so the working range of the vehicle system basically meets the requirements... The airship has to specifically reduce the power.”
The amount of information in this paragraph is enough for Wu Wei to digest. It took a few minutes to fully understand Chang Haonan's ultimate goal:
"So...the network coding technology you just mentioned is for multi-hop communication?"
"That's right."
Chang Haonan nodded, then raised his finger and pointed at the information in Wu Wei's hand:
"If you turn back two pages, there will be relevant technologies. Explain." The latter quickly lowered his head and turned to the position he mentioned.
"Of course, there is nothing much to say about network coding technology itself. You are an expert in this field. You must have studied it...at least understood it."
At this time, Chang Haonan continued:
“The real core of our test is to use the maximum rank distance code to provide sufficient error correction capabilities for the network coding transmission process, ensuring that even if the opponent... or Despite the strong interference caused by the natural environment, the information can still be transmitted accurately."
"MRD code..."
Wu Wei put the information in his hand on the table and thought about it. :
“When the scatter communication vehicle project was first established two years ago, I also studied this technology. It can detect and correct errors in the matrix data structure. The error correction efficiency is higher than the traditional low-density parity check code ( LDPC) can be improved by five orders of magnitude..."
Compared with Zhang Weiyong, who specializes in satellite systems, he obviously has a deeper understanding of this aspect.
“As long as you have done research.”
Chang Haonan put down the pen he was holding:
“Not only in terms of error correction ability, but also in terms of technology alone In other words, MRD code is an encryption technology that is almost impossible to crack, which can greatly improve the stability and security of communication.”
The reason why he emphasized that technically speaking, it is because of any encryption method. Nothing can stop physical theft.
In a system, the most reliable and weakest link is always the people.
“But Mr. Chang, our research at that time was all completed on the supercomputing end...”
Wu Wei’s frowned brows still did not relax:
"The encoding and decoding process of MRD codes relies on check matrices and generator matrices. It is very complex and its efficiency depends heavily on computing power. Even for supercomputers, the cycle to complete an encoding-decoding cycle sometimes has to be calculated in hours. , if it is to be applied to real-time communication, the computing power requirements for relay equipment will be too high..."
Chang Haonan was not surprised by this result.
In fact, the reason why the maximum rank distance code, an artifact with incredible effects, was proposed as early as 1985 but has never been put into use is mainly because the encoding and decoding process is too complicated.
The technological breakthrough he achieved was precisely in this part.
"I think... what you were testing was the Gaby Dulin code?"
"Yes."
Wu Wei nodded:
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"After all, it is the most classic maximum rank distance code."
"However, we have also tested several variants of Gaby Dulin codes. In general, the efficiency is improved compared to the original version, but it is not It's very obvious..."
"But the maximum rank distance code I want to test is not entirely based on the concept proposed by Gaby Dulin..."
Chang Haonan put down the code he just put down again. Picked up the pen:
"The technical details of this part... are too long and cannot be explained in one or two hours. I will give you a special technical document later..."
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"But to put it simply, it is to introduce a new concept called the self-duality of the maximum rank distance code... uh... similar to the orthogonal concept of the matrix, that is, when an MRD code C and its dual code C⊥ are equal At that time, we believed that it has self-duality. Under the premise of meeting certain conditions, an MRD code must be equivalent to a self-dual MRD code..."
"Combining this concept, we can design a For Gaby Dulin codes... Of course, it can also be a fast decoding algorithm for other MRD codes, that is, for the adjoint S and i=t, t-1, t-2... calculate the matrix Mi and the determinant det(Mi ), until the first occurrence of i=m such that det(Mi)≠0, m here is the rank of the error vector e..."
"..."
"Further, we Legal user A can be allowed to select the matrices S, You can get a lot of improvement..."
Although it was "in simple terms", Chang Haonan still talked for almost half an hour.
This is based on the premise that Wu Wei has sufficient encryption algorithm foundation.
“That is to say, we use traditional encryption methods to transmit the asymmetrically encrypted message itself, and then use asymmetric encryption to transmit the key required for decryption. This can reduce the amount of data that requires error correction by the relay station. To ensure transmission efficiency?"
Wu Wei tentatively confirmed.
Chang Haonan nodded happily and leaned his upper body back on the chair.
Now, the latter at least understands the technical route part.
As for the specific algorithm level...
This is not urgent.
Even he himself, with the help of the system, spent almost a month on this.
“I have tested this MRD code combined with network coding technology on a small-scale wired network.”
Chang Haonan said lightly:
"The result is that in a four-route multi-hop network, the actual transmission capacity can be increased by about 15-20 times, but the processing delay is a little higher and has to be calculated in seconds."
"But for satellite communications or For Tiandi Communications, because the bandwidth is too low, the transmission delay will replace the processing delay and the actual delay... will be reduced! ”
(End of this chapter)
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