Cyclic Range Search Architecture for LPD Signal Acquisition
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Solution Overview
Problem
Low Probability of Detection (LPD) receivers face significant computational complexity in signal acquisition due to the need for long chip sequences at extremely low signal-to-noise ratios, making it challenging to operate efficiently.
Innovation Solution
The architecture for signal acquisition with a cyclic range search, which constrains transmitter start times to known intervals and uses multiple redundant known sequences, allowing for a cyclic range search that reduces computational complexity and enables ad hoc channel access, controlled latency, distance estimation, and distance-directed transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long known sequence is used for signal acquisition at low SNR, then the probability of detection is improved, but the computational complexity increases
Solution Approach 1:
The patent divides the long known sequence into multiple shorter segments that are transmitted at different time intervals. The receiver processes these segments separately and combines the results, achieving the same detection probability as a single long sequence but with reduced computational complexity at any given moment.
Solution Approach 2:
The transmitter sends multiple redundant known sequences in advance at different time intervals before the actual data transmission. This allows the receiver to perform acquisition and synchronization ahead of time, reducing the computational burden during critical data processing phases.
2Measurement precision
If a long known sequence is used for signal acquisition, then synchronization accuracy is improved, but the time required for acquisition increases
Solution Approach 1:
The acquisition process is divided into multiple parallel searches over segmented time intervals. Instead of searching through one long sequence sequentially, the receiver performs multiple shorter searches simultaneously or in rapid succession, reducing total acquisition time while maintaining synchronization accuracy through combination of results.
Solution Approach 2:
The transmitter periodically transmits known sequences at regular intervals. The receiver utilizes this periodic structure to perform acquisition at multiple discrete time points, enabling faster synchronization by identifying the signal presence across periodic occurrences rather than requiring a single long continuous search.
3Productivity
If multiple redundant known sequences are transmitted, then the cyclic range search efficiency is improved, but the transmission overhead increases
Solution Approach 1:
The multiple known sequences serve dual purposes: they enable efficient cyclic range search for signal acquisition and simultaneously provide redundancy for error correction and verification. This multi-functionality justifies the transmission overhead by extracting multiple benefits from the same transmitted data.
Solution Approach 2:
The system transmits redundant known sequences that can be discarded after serving their acquisition purpose, while the essential information is recovered and retained. This allows the receiver to use the redundant sequences for range search without permanently storing or processing all transmitted data, managing the overhead efficiently.
Data Source
AI summary
An architecture for a spread-spectrum transmitter-receiver system in an advanced tactical data link that allows the receiver to readily acquire and synchronize to a desired LPD signal. Signal acquisition is performed with a cyclic range search that uses multiple redundant known sequences mapped to a known message sequence in a highly repeated manner. By employing the invariance of the speed of light, and synchronicity between transmitter and receiver, the architecture can significantly reduce the computational complexity of the receiver. Additionally, the architecture enables ad hoc channel access, controlled latency, distance estimation, and distance-directed transmissions.