Receiver Multiplexing Null Codes for Partial Composite Signal Decoding
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Solution Overview
Problem
Existing navigation satellite receivers require complex decoding of multiplexed binary offset carrier signals, which may not be authorized for all users or geographic areas, necessitating a receiver that can partially or fully decode these signals without complete access to the local replica.
Innovation Solution
A receiver with a front-end for down-converting composite signals, an analog-to-digital converter, signal generators, a multiplexer, and a correlator that can generate and process precursor signals to decode at least a portion or the entire composite signal, depending on operational modes authorized by the user's service plan and location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex receiver is used to fully decode the multiplexed binary offset carrier signal, then complete signal decoding capability is achieved, but device complexity and cost increase
Solution Approach 1:
The receiver is divided into multiple functional modules: a signal generator that creates precursor signals, a multiplexer that combines precursor signals with null codes, and a correlator that processes the composite signal. This segmentation allows the receiver to achieve full decoding capability through coordinated simple modules rather than a single complex unit.
Solution Approach 2:
The signal generator pre-generates precursor signals that correspond to expected signal components before correlation occurs. The multiplexer prepares the combined signal structure in advance by multiplexing precursor signals with null codes according to a predetermined sequence, enabling the correlator to efficiently process the composite signal without requiring complex real-time computation.
2Loss of information
If full decoding of the composite signal is implemented, then complete information is obtained, but user authorization and geographic restrictions cannot be enforced
Solution Approach 1:
The receiver implements selective signal processing by multiplexing precursor signals with null codes in a predetermined sequence. The correlator can be configured to process only certain portions of the composite signal corresponding to authorized components, while ignoring other portions represented by null codes. This allows the system to perform partial decoding that matches user authorization levels while maintaining the infrastructure for full decoding capability.
3Reliability
If the receiver processes the complete composite signal, then maximum signal-to-noise ratio is achieved, but processing complexity and computational load increase
Solution Approach 1:
The multiplexer extracts and separates signal components by multiplexing precursor signals with null codes in a predetermined sequence. The correlator then processes this structured composite signal, correlating received signals with the known precursor signal patterns. This extraction approach allows the receiver to focus computational resources on processing only the authorized signal components while maintaining optimal signal-to-noise ratio performance.
Data Source
AI summary
A multiplexer is capable of multiplexing at least two signals selected from the first signal, the second signal and the null code signal. In a first mode, the multiplexer multiplexes the first signal and the null code signal consistent with a predetermined time sequence for expression of the null code in first precursor signal In a second mode, the multiplexer multiplexes the first signal and the second signal to provide a second precursor signal. A correlator can correlate the digital received composite signal to the locally generated reference signal to decode at least a first portion of the received composite signal or the entire received composite signal, depending upon the mode (e.g., operation in the first or second mode).