AIS Message Error Protection for Low-Power Vessel Detection
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Solution Overview
Problem
E-Navigation systems face challenges in detecting AIS signals from small vessels due to low power transmission and signal collisions, especially in congested satellite detection environments, leading to difficulties in tracking vessels with low power and infrequent transmissions.
Innovation Solution
The implementation of error protection encoding schemes such as forward error correction, block coding, convolutional coding, and interleaving, combined with a message wrapper format, enhances the detectability of e-Navigation messages, allowing reliable recovery of message data even in noisy conditions and improving channel capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error protection encoding is applied to e-Navigation messages, then message detectability and reliability are improved, but message transmission time and processing complexity increase
Solution Approach 1:
Error protection encoding is applied in advance during message generation at the transmitter side. The binary payload is encoded with forward error correction codes (such as convolutional codes or block codes) and interleaving before transmission, so that the receiver can directly decode and recover messages even in noisy conditions without requiring retransmission, thus resolving the time loss issue.
Solution Approach 2:
The patent applies different error protection encoding schemes (convolutional coding, block coding, interleaving) with varying code rates and parameters to optimize the balance between reliability and transmission efficiency. By adjusting encoding parameters, the system achieves improved message detectability while minimizing the impact on transmission time.
2Reliability
If error protection encoding is applied to e-Navigation messages, then message detectability and reliability are improved, but device complexity increases
Solution Approach 1:
The error protection encoding process is divided into separate functional modules: forward error correction encoding, interleaving, and message wrapping. Each module handles a specific aspect of the encoding process independently, which simplifies the overall system design and implementation while maintaining high reliability. The receiver side similarly segments the decoding process into de-interleaving and error correction decoding steps.
Solution Approach 2:
The patent introduces a standardized message wrapper format that acts as an intermediary structure between the error protection encoding and the AIS message format. This wrapper encapsulates the encoded payload in a standardized form, simplifying the integration with existing AIS systems and reducing overall processing complexity.
3Speed
If conventional receivers are used without error protection decoding, then processing speed is faster, but message reliability deteriorates in noisy conditions
Solution Approach 1:
The error protection encoding scheme enables the message to be self-sufficient against noise and interference. The encoded messages contain built-in error correction capabilities that allow receivers to autonomously detect and correct errors without requiring external intervention or retransmission requests, thus maintaining both speed and reliability.
Data Source
AI summary
Methods and systems for enhancing the detectability of maritime e-Navigation messages are provided. Transmitters apply error protection encoding to the payload portion of messages to be transmitted, which are wrapped in a standard e-Navigation message format such as that used by the Automatic Identification System. Transmitted messages are received by a satellite or other surveillance platform employing a compatible radio frequency receiver to collect message signals over a large area or great distance. Candidate messages are identified and the error protection encoding decoded to recover messages.