Symbol Hopping for Wireless Positioning Signal Interference
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Solution Overview
Problem
Existing wireless positioning methods face challenges in accurately determining the location of mobile devices due to signal interference from stronger sources, which can drown out weaker signals, leading to inaccurate or failed position determination.
Innovation Solution
The implementation of symbol hopping techniques in wireless communication systems, where base stations transmit positioning measurement signals on different symbols within a resource block, minimizing interference and allowing mobile devices to receive signals from multiple sources without collision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If base stations transmit positioning signals simultaneously on the same time-frequency resources, then the system is simple and efficient, but signal collision occurs where stronger signals drown out weaker signals
Solution Approach 1:
The patent divides the time-frequency resource into multiple orthogonal codes (e.g., sequence codes, spreading codes) and assigns different codes to different base stations. This segmentation allows multiple signals to be transmitted simultaneously without collision, as each signal can be distinguished by its unique code identifier. The mobile device measures signals from multiple base stations using these orthogonal codes to determine positioning information.
2Reliability
If base stations use different time-frequency resources for positioning signals, then signal interference is reduced, but the complexity of the system increases
Solution Approach 1:
The patent combines multiple dimensions (time, frequency, and code) to create orthogonal resources. Instead of simply assigning different time slots or frequency channels, the system uses orthogonal codes that can be multiplexed within the same time-frequency grid. This merging of dimensions allows multiple base stations to share resources efficiently while maintaining signal distinguishability, reducing overall system complexity compared to purely time-division or frequency-division approaches.
3Reliability
If orthogonal codes are assigned to base stations, then signal collision is eliminated, but the complexity of signal processing increases
Solution Approach 1:
The patent employs autocorrelation and cross-correlation properties of orthogonal codes to enable the mobile device to automatically distinguish between different base station signals. The signal processing leverages the mathematical properties of the codes themselves - specifically, that orthogonal codes have zero cross-correlation - to provide built-in separation functionality. This self-service approach reduces the need for complex external processing algorithms, as the code structure inherently provides the separation mechanism.
Data Source
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AI summary
Mobile devices often use orthogonal frequency division multiplexing (OFDM) to calculate position information of mobile devices within the network. However, physical distance between the mobile device and a signal source for positioning and other environmental factors can influence the signal strength of received signals. Received signals at the mobile device that are stronger may drown out the weaker signals, particularly when two signal sources occupy the same symbol. In traditional OFDM, a signal source transmits the same symbol for each positioning occasion, so a weaker signal may never be detected over a stronger signal, reducing the accuracy of the positioning calculations. Described herein are systems and methods for using a pattern to vary the designated symbol for each signal source in a wireless network so that a weaker signal from a signal source may be detected on at least some of the positioning occasions.