OFDM Signal Structure for Terrestrial Timing and Positioning
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Solution Overview
Problem
The existing LORAN-C system has become obsolete with the rise of Global Navigation Satellite Systems (GNSS), and there is a need for a modernized terrestrial positioning system that can provide backup timing and location services, especially in scenarios where GNSS fails, while optimizing spectrum use and enabling data communication.
Innovation Solution
A Low-Frequency (LF) broadcast system using Orthogonal Frequency Division Multiplexing (OFDM) signal structure to transmit timing reference signals and data, allowing for improved spectrum efficiency and modernized signal structure, enabling the transmission of timing and navigation information even when GNSS systems fail.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LORAN-C system is used for terrestrial positioning, then timing reference signals can be broadcast, but the system becomes obsolete and cannot provide modern data communication capabilities
Solution Approach 1:
The patent applies multi-functionality by designing a broadcast system that simultaneously provides timing reference signals for positioning and data communication capabilities. The OFDM signal structure carries both timing information and data payloads, allowing the system to serve multiple purposes (positioning, navigation, timing, and data transmission) rather than being limited to legacy LORAN-C timing-only functionality.
Solution Approach 2:
The patent changes the signal structure parameters from legacy LORAN-C pulse formats to modern OFDM waveforms with configurable subcarriers, symbols, and resource blocks. This parameter transformation enables the system to support modern data communication protocols while maintaining compatibility with timing reference signal requirements, thereby eliminating obsolescence.
2Productivity
If OFDM signal structure is used to broadcast timing reference signals and data, then spectrum efficiency is optimized, but system complexity increases
Solution Approach 1:
The patent segments the OFDM signal into distinct resource blocks, where each resource block contains specific timing reference signals and data portions. This segmentation allows the receiver to process timing and data separately, reducing overall system complexity while maintaining high spectrum efficiency through the structured resource allocation.
Solution Approach 2:
The patent employs periodic transmission of OFDM symbols with regular structures, where timing reference signals are transmitted at known intervals. This periodicity simplifies receiver synchronization and signal processing, reducing complexity while enabling efficient spectrum utilization through predictable signal patterns.
3Measurement precision
If timing reference signals are transmitted during OFDM resource blocks, then accurate timing and location services are provided, but transmission power requirements increase
Solution Approach 1:
The patent applies local quality by concentrating transmission power specifically on the subcarriers and symbols carrying timing reference signals, rather than uniformly distributing power across all signal elements. This localized power allocation ensures high timing accuracy where needed while reducing overall power requirements by using lower power for data portions.
Data Source
AI summary
Embodiments herein provide for a Low-Frequency (LF) broadcast system that improves on the LORAN-C system to help optimize the use of available spectrum while modernizing the signal structure of broadcast signals. In particular, embodiments can utilize an Orthogonal Frequency Division Multiplexing (OFDM) signal structure to broadcast timing and data signals in successive symbols of an OFDM resource block. Signals can include, for example, comb-1, comb-2, or comb-3 signal structures. Other signal aspects such as muting schemes, modulation, frequency offsets, and the like may vary, depending on desired functionality.