Under the background that the service area of the Beidou-3 system has expanded to the whole world, and the RDSS service performance and capacity have been greatly improved compared with the Beidou-2, we have studied the voice and image transmission technology based on the Beidou-3 RDSS link, which can make up for the coverage of traditional communication systems Weakness, as well as the relatively insufficient satellite communication capabilities of our country at the current stage. Compared with Beidou-2, the performance of Beidou-3 short message service has been greatly improved, and it can provide better services to users in China and surrounding areas. Currently, the single-transmission capacity of Beidou-3 level 5 card is 1750 bytes/sent .
On the basis of in-depth understanding of the transmission characteristics of RDSS links, we have broken through the high compression ratio voice and image coding and decoding technology , designed a low-latency voice and image data scheduling protocol , and realized point-to-point continuous voice and image transmission between users, and users Real-time voice and image feedback between the background and the background.
Our RDSS image transmission technology can achieve 40 times compression rate, the image quality evaluation index PSNR is not lower than 20dB, and innovatively realizes the progressive transmission method of image compression.
(Beidou-3 short message sending picture process demonstration)
1. Workflow
1. After the terminal takes a photo or selects a photo from the album, you can choose the cropping ratio and compression ratio;
2. After confirming the sending, the built-in compression library of the terminal divides the picture into N packets, and sends them to the computer terminal through the Beidou-3 short message satellite;
3. After the computer terminal receives the data packet, it decompresses it through the compression library, and displays the latest image effect in real time;
4. This technology adopts a progressive transmission method. After receiving 2-3 packets of data, you can see the outline clearly. The more packets you receive, the clearer it will be;
5. Even if 1-2 packets of data are lost in the later stage of receiving data, it will not have a great impact on the image quality;
2. Functional advantages
1. High compression ratio
Innovatively proposed and realized the progressive image display technology in the case of sub-packet transmission, optimized the use of precious channel bandwidth, realized error-resistant, high-compression ratio image transmission under narrow bandwidth, and can achieve a maximum compression ratio of 100 times.
2. High quality
Realize the progressive data sub-packet transmission protocol of image data. After the background receives the data, it will decompress and compensate, according to the image quality requirements in actual use of users.
3. High efficiency
The traditional way is to decompress and see the picture after receiving all the compressed packets. If you encounter packet loss, you will not be able to decompress. However, this technology can see the outline after receiving 2-3 packets of data. The more packets received, the more clear.
(background)
The traffic fee of Tiantong satellite phone is 16 yuan/MB , and the original image of a picture is 2MB. Using this compression library, it can be compressed to 20KB and then restored to 2MB
(inferred)
You can send 51 pictures with 1 megabyte of traffic, and the cost of sending 2MB pictures with this compression library is only 0.3 yuan per picture
3. Technical Features
1. Image progressive transmission technology
The highest supported transmission mode of Beidou-3 is 14Kbit data per second, and the bit error rate of the data link is 10^(-5). Under this condition, the compressed image data transmission requires a strong compression algorithm. The ability to resist bit errors ensures that bit errors do not spread. In order to ensure the real-time performance of data transmission, the compression algorithm should have good image quality under high compression ratio.
In order to support the BDS-3 data packet transmission protocol under the condition of low bit rate transmission, realize the reliable transmission of image compression data under high bit error rate, and at the same time realize the self-adaptive compression of images, and meet the requirements of image data under different transmission delay requirements Reliable transmission.
(PSNR peak signal-to-noise ratio)
We researched and proposed an image compression data packet retransmission strategy based on the RDSS transmission protocol, innovatively proposed and realized the image progressive display technology in the case of packet transmission, optimized the use of precious channel bandwidth, and realized anti-error code under narrow bandwidth , High compression ratio image transmission.
2. Optimization of high compression ratio image transmission strategy under narrow bandwidth
Aiming at the transmission conditions such as BDS-3's low bit rate, high bit error rate and data packet size limitation, the progressive data packet transmission protocol of image data is realized to meet the requirements of real-time performance and image quality in actual use.
According to the actual transmission requirements, this technology adopts an adaptive high compression ratio strategy, and the compressed image data is re-encapsulated in a progressive order. The encapsulation protocol includes frame header and frame count information, which can support the retransmission of application layer data packets and optimize utilization The precious channel bandwidth meets the user's real-time requirements for image data acquisition and high image quality requirements.
3. Anti-long delay voice and image transmission protocol
In order to solve the difficulties in RNSS voice and image transmission, this paper introduces network coding technology in RNSS transmission, and designs and proposes a voice and image transmission protocol based on coding redundancy.
This mechanism proposes that according to the packet loss rate of the link, the sending end reasonably adds redundant coded messages to the normal message sequence, and the receiving end decodes these coded messages to generate lost original messages, thereby avoiding the loss of packet loss and retransmission. resulting time loss.
4. Application scenarios
5. Demonstration video
Image compression and decompression library demo video v5.0-20220808