GB/T 39349-2020 in English
VALIDSpace data and information transfer systems- TC （telecommand） synchronization and channel coding
- Issued on:2020-11-19
- Implemented on:2021-06-01
- File Format:PDF
- Delivery:Via email within 5 business days
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| Standard No: | GB/T 39349-2020 |
| Document status: | VALID |
| Title in English: | Space data and information transfer systems- TC （telecommand） synchronization and channel coding |
| Title in Chinese: | 空间数据与信息传输系统 遥控同步与信道编码 |
| Language: | English |
| File Format: | Electronic (PDF) |
| Delivery: | Via email within 5 business days |
| Issued on: | 2020-11-19 |
| Implemented on: | 2021-06-01 |
| ICS Classification: | 49.140-Space systems and operations |
| Professional Classification: | GB-National Standard |
| Related Topics: | remote
Data Control and Information Management remote control Tongxin data channel coding channel coding GBT39349 GB/T 39349-2020 channel coding standard Information transfer gb/t 39349-2020 Agricultural spatial information standards and gb/t 39349 |
《GB/T 39349-2020空间数据与信息传输系统 遥控同步与信道编码》由TC425（全国宇航技术及其应用标准化技术委员会）归口，TC425SC3（全国宇航技术及其应用标准化技术委员会空间数据与信息传输分会）执行，主管部门为国家标准化管理委员会。
Introduction
Analysis of the core content of the standard
This standard specifies the key technologies for synchronization and channel coding of remote control links in space data systems, including four core modules: BCH coding, LDPC coding, communication link transfer unit (CLTU) and pseudo-randomization, which are suitable for reliable data transmission between spacecraft and ground stations.
Comparison of Coding Technologies
| Technical Indicators | BCH(63,56) | LDPC(128,64) | LDPC(512,256) |
|---|---|---|---|
| Coding Efficiency | 88.9% | 50% | 50% |
| Error Correction Capability | 1bit Error Correction/2bit Error Detection | Soft Decision Decoding | Soft Decision Decoding |
| Synchronization Sequence | 16bit EB90 | 64bit 034776C7272895B0 | 64bit 034776C7272895B0 |
| Applicable scenarios | Conventional SNR link | Low SNR deep space link | Extremely low SNR link |
CLTU transmission unit structure
The communication link transmission unit adopts a three-segment structure:
- Start sequence: BCH encoding adopts 16bit EB90, LDPC encoding adopts 64bit specific synchronization code
- Encoded data area: BCH contains 56-bit information + 7-bit check for every 63 bits, and LDPC supports two code lengths of 128/512
- End sequence: BCH uses 64-bit C5C5C5C5C5C5C579, and LDPC (128,64) uses a 128-bit specific sequence
The receiving end achieves frame synchronization through a state machine mechanism, which includes three working modes: search state, decoding state and inactive state.
Key technology implementation
1. Pseudo-randomization processing
The polynomial x8+x6+x4+x3+x2+x+1 is used, and the initial seed is FF399E5A68, which can effectively ensure the balance of data "0" and "1".
2. Physical layer operating procedures
- PLOP1: Single CLTU transmission mode, including capture sequence → CLTU → end sequence
- PLOP2: Multiple CLTU continuous transmission, inserting idle sequences between frames to maintain synchronization
3. Management parameter configuration
Key parameters include:
- Maximum CLTU length (default 1024 bytes)
- Number of retransmissions (3 times recommended for long delay links)
- Carrier modulation mode (CMM1-CMM4)
Implementation recommendations
Deep space exploration mission: Prioritize LDPC (512,256) coding, combined with PLOP2 operating procedures to improve transmission reliability under extremely low signal-to-noise ratio.
Near Earth Satellite Mission: BCH coding can be used to simplify the system complexity, and pay attention to setting reasonable filling data rules.
System Verification Points: It is necessary to focus on testing the fault tolerance of the starting sequence detection, the decoding success rate under different signal-to-noise ratios, and the pseudo-randomization synchronization maintenance performance.
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