Telemetry Time-Series Compression Using Predictive Bit Masks
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Solution Overview
Problem
Current methods for compressing telemetry time series data in space missions are inefficient due to high processing power requirements and limited bandwidth, particularly for housekeeping data, which often expands under existing compression methods and lacks stability for real-time applications.
Innovation Solution
A lossless compression method that predicts bit states in telemetry data packets based on historical data, using statistical analysis to create mask packets and perform bit operations such as XOR and AND, allowing for near real-time compression with reduced processing power and improved compression ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If complicated compression software (e.g. winzip, 7zip) is loaded into the spacecraft's memory, then compression ratio is improved, but device complexity and processing power requirements increase
Solution Approach 1:
The patent replaces complex, long-lived compression software with simple, disposable bit operations (XOR, AND, OR) that can be executed quickly and discarded. These elementary operations require minimal processing power and memory while achieving effective compression through statistical exploitation of bit patterns in telemetry data.
Solution Approach 2:
The patent substitutes traditional mechanical/software-based compression algorithms with a mathematical/statistical approach using bitwise operations. Instead of loading complex compression code, the system uses probabilistic models and bit manipulation to achieve compression, replacing the 'mechanical' software system with a more efficient mathematical system.
2Power
If RICE compression is used for housekeeping data, then processing power is reduced, but compression ratio deteriorates and data may expand
Solution Approach 1:
The patent changes the approach from using fixed compression algorithms to dynamically adjusting compression parameters based on statistical analysis of the actual data. By analyzing historical telemetry data to determine bit state probabilities and using adaptive bit operations, the system optimizes compression for each specific data set, achieving both low processing power and high compression ratio.
Solution Approach 2:
The patent introduces dynamic adaptation into the compression process by continuously analyzing data patterns and adjusting the compression strategy accordingly. The system monitors bit state probabilities and modifies its approach in real-time, making the compression process dynamic rather than static, which allows it to handle varying data characteristics effectively.
3Measurement precision
If high frequency sampling is performed, then measurement precision is improved, but bandwidth requirements increase
Solution Approach 1:
The patent extracts and transmits only the most significant and unpredictable bits from the telemetry data, leaving out the predictable bits that can be reconstructed at the ground station. This selective extraction maintains measurement precision for critical parameters while dramatically reducing the quantity of data that needs to be transmitted over the bandwidth-constrained channel.
Solution Approach 2:
The patent applies different treatment to different parts of the data structure, identifying and preserving only the locally significant bits that contain actual information, while compressing or eliminating redundant predictable bits. This local quality approach ensures that monitoring accuracy is maintained for critical measurements while reducing overall bandwidth consumption.
4Loss of information
If run length substitution algorithm is used with multiple passes, then compression is achieved, but processing time increases making it unsuitable for real-time applications
Solution Approach 1:
The patent skips the multiple-pass approach entirely by performing compression in a single pass using straightforward bit operations. The method processes each bit once, applying pre-determined XOR and AND operations based on statistical probabilities, thereby rushing through the compression process without the need for repeated analysis and substitution passes.
Solution Approach 2:
The patent performs preliminary statistical analysis of the data patterns before the actual compression operation. By pre-calculating bit state probabilities and determining the optimal bit operations in advance, the system prepares everything needed for rapid single-pass compression, eliminating the need for multiple processing passes during the actual compression phase.
Data Source
AI summary
A mask packet is provided with bits in a ONE state for all predictable bit positions and with a ZERO state for all unpredictable ones. All predictable bit positions of the new data packet are brought into a ZERO state if an actual bit state matches the predicted bit state and into a ONE state if the actual bit state does not. A processed packet is generated by applying an AND operation between the new data packet and the mask packet to change all unpredictable bits to a ZERO state. A series of counters is provided by calculating the number of bits in the processed packet between the first bit and the first bit with a state ONE; and between the following bits with a state ONE and between the last bit with a state ONE and the last bit in the processed packet. The counters are stored or transmitted.