Chapter 1013 Five times...not enough!
Now that the technical principles and specific research and development routes have been clarified, the 54th Institute of Electrical Engineering has moved quite quickly.
?This is also due to the fact that the other party has been working in the field of terrestrial mobile communications for many years. As the two most important projects at present, the vehicle chassis communication equipment has actually entered the testing stage long ago.
It''s just one of the satellite communication vehicles. Since China''s own communication satellites are poor in number and performance, their performance has been limited.
After receiving Chang Haonan''s project request, the 54th Institute only took about three weeks to complete the hardware transformation of four prototype vehicles, making them equipped with complete reception-decoding-storage-encoding- forwarding function, becoming a true network coding data node.
?Just for the convenience of testing, the decoding and encoding modules are designed to be completely physically shut down to minimize the performance impact of additional hardware on the control group.
As for the procedures for encrypting and decrypting information…
That’s not even a problem.
?Chang Haonan has conducted tests on wired networks before, and the program at that time can be slightly modified.
In contrast, although Zhejiang University''s actions are not slow, they do not have any extra stratospheric airships on hand.
Whether it is to build new ones or to lower the ones already floating in the sky to collect weather data, it will take time.
The progress has lagged behind.
?However, Chang Haonan is not prepared to change his plan because of this.
Principle verification does not matter whether it is in heaven or on earth. .
Therefore, after the acceptance of the four modified relay communication vehicles, Chang Haonan sent them to the predetermined test area in western Mongolia Province.
As for why it is Meng Province…
Because Torch Group has a huge test field here.
Since Comrade Zhuang Bingchang has not yet successfully developed alfalfa and soybeans that meet the requirements, and Chang Haonan himself has not yet found a polymer material that can provide sufficient shear resistance for the sand, this land has not really started to play a role yet.
But after all, the right to use it belongs to Torch Group, and there are no large towns hundreds of kilometers around, so it is easy to get approval for radio transmission testing.
The only problem is that in 2002, there was no highway network that later spread across the country, especially in the relatively remote areas of the central and western regions.
So the four vehicles were first transported by rail from the capital to Qingcheng City, the capital of Mongolia Province, and then traveled hundreds of kilometers on their own. It took nearly a week to get there.
?Of course, during the whole process, dedicated personnel from the Torch Group and the 54th Institute of Electrical Engineering were responsible for escorting the vehicle, and Chang Haonan did not need to follow him personally—
The latter''s work schedule does not allow him to waste so much time on the road.
? As the general person in charge of the project, Chang Haonan only flew to TMTZQ Biqi Airport the day before the test.
Then on the morning of the next day, he transferred to a Z-12 helicopter belonging to the Air Force Search and Rescue Brigade of the Beijing Military Region and arrived at a general aviation airport near the test site.
When the helicopter landed, Wu Wei and others, who had already arrived here in advance, were naturally waiting near the apron.
General aviation airport mainly serves various types of helicopters, as well as small gadgets such as transport 5.
?The site conditions are naturally much worse than those of common civil aviation airports.
Even the runways and aprons are unpaved surfaces that have only been hardened.
Chang Haonan did not have much experience in helicopter rides before.
So, he jumped out of the cabin as soon as he confirmed that the helicopter had stopped.
Immediately afterwards, I was blinded by the dust that had not completely fallen back to the ground...
Fortunately, the people who were picking up the plane were far away, so they were walking over slowly and hurriedly, and did not notice Chang Haonan''s little embarrassment.
“Report to Mr. Chang.”
?Wu Wei came to Chang Haonan:
“According to the previously determined process arrangement, the four prototype vehicles have completed all inspections and are just waiting for you to officially issue the test order!”
Not far behind him, four SX2190 chassis communication vehicles were parked in groups of two under two sheds made of camouflage cloth.
Looking at the somewhat gray-faced people in front of him, Chang Haonan took a deep breath, took two steps forward with emotion, and shook hands with Wu Wei:
“Thank you for your hard work.”
Following the former’s eyes, Wu Wei lowered his head and looked at his earth-colored clothes:
ifier=Where is this going?￠a??a?￠
“We wish we were out on business trips for ten months a year. We’ve never seen anything like this... we’ve long been used to it.”
Speaking, he reached out and brushed off the dust on his clothes.
But the effect is obviously not very good.
So I had to change the topic:
"Mr. Chang, the logistics comrades at the airport here have left lunch for you. Look..."
?Chang Haonan didn''t eat much in the morning. It was already past noon, and he did feel a little hungry.
??But after looking at the four test vehicles in the distance with even the disk antennas deployed, I still felt that there was no time to waste:
“Pack up the whole lunch box for me, and find an empty space to take a sip during the test...”
…”
Four communication relay vehicles, according to the test plan from easy to difficult, will start from being 5 kilometers apart from each other, and gradually extend the distance in steps of 5 kilometers, until the distance is 30 kilometers apart.
?Subject to the influence of the height of the antenna and the curvature of the earth, the maximum distance for direct communication of this type of communication vehicle is 30 kilometers.
Any further away, you have to use scattering communication means.
On the contrary, it is not conducive to the conduct of today''s test.
?As Chang Haonan officially ordered the test to begin, cars No. 2, 3, and 4 left the parking lot in sequence and drove west along a dirt road.
Vehicle No. 1 does not need to move as a signal transmission source. At this time, several technicians have begun to erect antennas and raise the mast.
The initial communication test with an interval of 5 kilometers did not require this thing.
But the latter is essential.
A few minutes later, Chang Haonan also entered the compartment of Car No. 1 with Wu Wei.
In fact, a conference room was specially set aside at the airport tower as the test command center.
?However, in order to see the results as soon as possible, Chang Haonan chose to get on the bus in person.
…
??Although the road conditions on unpaved roads are very poor, one hundred kilometers is not a very long distance for a vehicle after all.
About half an hour later, the farthest car No. 4 also reported that it had arrived at the predetermined location 15 kilometers away. So.
The first round of testing has officially begun.
First of all, it is naturally the control group.
In other words, according to the traditional relay model, the relay station only receives and forwards data but does not process the data.
“All cars are in place!”
From the radio, the voice of the on-site test commander Fu Mingyi came:
“Car No. 1, start sending data!”
For a time, in the originally noisy carriage, only the hum of the air conditioner and communication equipment was working, and the breathing sounds of a total of four people, including Chang Haonan.
The data content used for the test was set by Chang Haonan in advance, so the operator did not need to input anything on site.
Just select the content on the operation interface and then send it.
?However, after all, the program took less than a month to compile quickly, so there was no need to consider issues such as UI interaction.
Let alone others, even Chang Haonan himself was a little nervous looking at the slightly crude interface.
Fortunately, the basic functions are quite complete.
?It didn’t take long for the data transmission to come to an end.
?There is no doubt that even without looking at the specific results, you can tell just by feeling that the results are not optimistic -
Network throughput is not the "average network speed" as commonly understood. The test method is not to transmit a certain amount of data files and then divide it by the final time. Instead, it sends a certain number of frames at a certain rate and calculates the transmission speed of the device under test. frame.
If the two are equal, then increase the sending rate and retest until the number of frames received is less than the number of frames sent, and the corresponding rate is the network throughput.
Hence, it can basically be considered that the shorter the test time, the worse the results.
?In addition, it is not difficult to see that although the result obtained by this test method is a bandwidth unit of one byte/second, it is by no means only related to the transmission bandwidth.
The more important thing is actually stability.
“1.4 kilobytes/second…”
? almost as soon as the numbers appeared on the screen, Wu Wei subconsciously figured it out.
Even at the beginning of the 21st century, the results were shockingly slow.
As he estimated before, using communication vehicles for multi-hop transmission on the ground with poor transmission conditions will not end well.
In fact, the measured throughput on the No. 2 bus is as high as more than 170 kilobytes/second.
At the No. 3 car, there are still about 30 kilobytes/second left...
Car No. 4 only has 1.4 kilobytes/second left.
It is enough to see the devastating impact of adding relay nodes on transmission speed.
?Of course, such exaggerated results are indeed a special case caused by large local natural disturbances.
But the trend is always correct.
“Turn on the encoding and decoding functions of each car number and test again!”
?Chang Haonan recorded the experimental data and then gave an order to the radio.
For him, the worse the results of the control group, the closer they are to success.
?However, the premise of everything is.
The experimental group can really measure better data.
…
As the cooling fan of the cabinet started whirring again, the second test officially began.
Theoretically, after the encoding and decoding functions are enabled, the network throughput will approach the Shannon limit.
Although there will still be many impacts in actual operation, no matter what, the results should be better than before.
The testing process did not live up to expectations.
The duration is several times longer than the first time.
Even though the outcome is only positively correlated with the length of time rather than directly proportional, this is at least a good sign.
It was not until more than ten minutes later that a number representing the throughput of car No. 4 popped up on the screen as before.
“6.8 kilobytes/second!”
This result made Wu Wei''s eyes light up.
You should know that these numbers themselves do not represent the true level of his communication vehicle.
But the magnitude of the improvement is real.
Nearly 5 times!
?He has no doubt that if his own products use this technology, their performance will not be completely outdated even after 5 or even 10 years...
“Mr. Chang, this…”
He looked at Chang Haonan excitedly, ready to express congratulations.
But when he said the words, he realized that the other person''s face... didn''t seem very good-looking.
“That’s not right…”
?Chang Haonan frowned slightly, stared at the results on the screen and murmured.
??The slightly weird reaction directly confused Wu Wei:
“That’s not right…what’s wrong?”
…”
He was greeted by a moment of silence.
After a while, Chang Haonan said softly in a tone that was unclear whether he was talking to himself or answering a question:
“I tested it on a wired network before, and the result was never 15 times lower...Why is the effect this time reduced by two-thirds?”
Hearing these words, Wu Wei almost choked on his own saliva—
?Good guy, does this mean that the five-fold improvement is not big enough?
(End of this chapter)