Adaptive Search Window for Mobile Station Pilot Signal Detection
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Solution Overview
Problem
In spread spectrum communication systems, mobile stations face inefficiencies when using fixed search windows to monitor pilot signals, as rapid changes in distance due to high-speed movement can cause the pilot signal's PN offset to fall outside the search window, leading to potential loss of signal detection.
Innovation Solution
Adaptive search windows are defined based on the mobile station's direction and speed relative to the target transmitter, shifting the center point and adjusting the window's coverage to accommodate expected phase changes, ensuring the signal remains within the search range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed search window is used to monitor pilot signals, then the device complexity is reduced and ease of operation is improved, but the reliability of signal detection deteriorates when the mobile station moves at high speed
Solution Approach 1:
The patent applies the dynamics principle by making the search window dynamic rather than fixed. The search window is shifted and resized based on the mobile station's measured speed and direction of motion relative to the target base station. This allows the search window to adapt to changing propagation conditions, maintaining signal detection reliability during high-speed movement while avoiding the need for complex manual configuration or monitoring of multiple fixed windows.
Solution Approach 2:
The patent applies preliminary action by using the mobile station's measured speed and direction of motion to predict the future position of the pilot signal's PN offset. The search window is proactively shifted to where the signal is expected to be, rather than reacting after the signal has moved outside the current window. This predictive approach maintains detection reliability while keeping the system relatively simple.
2Reliability
If the search window width is increased to accommodate high-speed movement, then the reliability of signal detection is improved, but the time required to find the signal increases
Solution Approach 1:
The patent dynamically adjusts the search window width based on the mobile station's measured speed. At higher speeds, the window is widened to accommodate greater PN offset variations, ensuring the signal remains within the search range. At lower speeds, the window is narrowed to minimize the time required to search through possible offsets. This dynamic sizing resolves the contradiction by adapting the window width to actual motion conditions rather than using a fixed conservative size.
Solution Approach 2:
The patent changes the parameters of the search window (position and width) based on measured mobile station speed and direction. By adjusting these parameters dynamically, the system maintains high detection reliability during rapid movement while minimizing search time during slower movement or when the signal is already near the center of the window.
3Reliability
If the search window is shifted to track the pilot signal during motion, then the reliability of continuous signal monitoring is improved, but the device complexity increases due to additional measurements and calculations
Solution Approach 1:
The patent applies self-service by using the mobile station's existing motion measurements (speed and direction) that are already being performed for other purposes in the communication system. These measurements are reused to automatically adjust the search window, eliminating the need for separate complex tracking mechanisms. The system serves itself by leveraging available data to maintain signal detection reliability.
Solution Approach 2:
The patent implements feedback by continuously measuring the mobile station's speed and direction of motion relative to the target base station and using this information to adjust the search window position. This closed-loop approach ensures the search window remains aligned with the pilot signal despite changes in propagation delay, maintaining reliable continuous monitoring without requiring overly complex open-loop tracking systems.
Data Source
AI summary
A mobile station receives a target pilot signal transmitted by a target transmitter in a spread spectrum communication system and measures its phase. The mobile station then defines a search window to search for the target pilot signal at a later time. The mobile station defines the center point of the search window based on the previously-measured phase and the mobile station's direction of motion and speed relative to the target transmitter. If the mobile station is moving toward the target transmitter, the center point is less than the previously-measured phase by an adjustment amount. If the mobile station is moving away from the target transmitter, the center point is greater than the previously-measured phase by an adjustment amount. The adjustment amount may depend on the mobile station's speed. After the search window is defined, the mobile station uses the search window to search for the target pilot signal.