Short Quasi-Cyclic LDPC Coding for Low-Power Meter Reading
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Solution Overview
Problem
State-of-the-art LDPC codes consume high energy per useful bit transmitted and require complex decoding due to their length, making them unsuitable for low-power, long-lasting battery-operated devices like water or electricity meters, especially in noisy communication channels.
Innovation Solution
An LDPC encoder configured with a bipartite Tanner graph having 128 variable nodes and 64 constraint nodes, where each constraint node is connected to 7 variable nodes, and cycles are of length 6 or more, derived from a protograph structure, ensuring short codes with high decoding performance and error correction capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If state-of-the-art LDPC codes are used for data transmission, then error correction capabilities are improved, but energy consumption per useful bit transmitted increases significantly
Solution Approach 1:
The patent changes the structural parameters of the LDPC code by using a protograph-based construction with specific constraints: 128 variable nodes, 64 constraint nodes, each constraint node connected to exactly 7 variable nodes, and ensuring all cycles have length >= 6. These parameter changes optimize the code for low-energy operation while maintaining error correction performance
Solution Approach 2:
The code is segmented into a protograph structure with 8 variable protograph nodes (each representing a group of 16 variable graph nodes) and 4 constrained protograph nodes (each representing a group of 16 constraint nodes). This segmentation allows for systematic construction of the code with controlled properties that reduce energy consumption
2Reliability
If long LDPC codes are used to achieve good error correction, then error detection and correction rate is improved, but decoding complexity increases due to numerous decoding iterations
Solution Approach 1:
The patent uses a short code length of 128 bits instead of traditional long codes, which reduces the number of decoding iterations required. The specific parameter configuration (128 variable nodes, 64 constraint nodes, degree-7 constraint nodes, girth-6 Tanner graph) is optimized to achieve good error correction performance with reduced decoding complexity
Solution Approach 2:
The use of a protograph-based construction allows for flexible and systematic generation of the code structure, enabling optimization of the Tanner graph properties (cycle lengths, node degrees) to balance error correction performance and decoding complexity dynamically
3Duration of action of stationary object
If transmission power is reduced to preserve battery lifetime, then battery lifetime is extended, but the received signal becomes very noisy
Solution Approach 1:
The patent converts the harmful effect of noisy channels (resulting from low transmission power) into a benefit by designing an LDPC code specifically optimized for noisy environments. The code's structure (girth-6 Tanner graph, degree-7 constraint nodes) provides robust error correction that actively combats the noise, allowing reliable communication even when the signal is very noisy
Solution Approach 2:
The patent applies error correction coding before transmission to cushion against the expected noise in the channel. By pre-encoding the data with redundancy bits according to the optimized LDPC code, the system prepares for potential errors in advance, allowing recovery of the original data even when received through a noisy channel
Data Source
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AI summary
The present invention describes an LDPC (Low Density Parity Check) code admitting a check matrix represented by a bipartite Tanner graph comprising 128 variable nodes of the graph and 64 constrained nodes of the graph, said code being characterized in that: each of the constraint nodes of the graph is connected to 7 variable nodes of the graph; each of the cycles of the graph has a length greater than or equal to 6; the minimum distance of said code is equal to or greater than a predefined minimum distance threshold.