Orthogonal Pilot Signaling for Terrestrial Position Detection
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Solution Overview
Problem
Mobile stations face difficulties in accurately estimating position location due to signal interference from multiple base stations, particularly in scenarios where satellite signals are unavailable or weak, such as indoors or in tunnels, leading to the 'hearability problem' and reduced detection of downlink pilot signals.
Innovation Solution
The method involves transmitting signal waveforms from multiple sectors with nearly mutually orthogonal signal dimensions, such as time or frequency, to reduce interference and enhance pilot signal detection, using techniques like time division multiplexing and dedicated or random coloring to partition sectors and allocate signaling resources, allowing for incremental detection and improved position location estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal waveforms are transmitted from multiple sectors simultaneously, then position location estimation capability is improved, but signal interference increases
Solution Approach 1:
The patent divides the set of sectors into multiple subsets, where each subset transmits pilot signals using a distinct orthogonal cover code (OCC). This segmentation allows simultaneous transmission from multiple sectors while maintaining orthogonality within each subset, thereby reducing signal interference and improving position location estimation accuracy.
Solution Approach 2:
The patent introduces an additional dimension of orthogonality by applying different orthogonal cover codes (OCCs) across sector subsets. This dimensional approach allows multiple sectors to transmit simultaneously without interference, as the OCCs provide orthogonality in the code domain, enabling improved position estimation while avoiding the hearability problem.
2Area of stationary object
If pilot signals are transmitted from all sectors, then position location coverage is improved, but detection accuracy deteriorates due to interference
Solution Approach 1:
Sectors are divided into multiple subsets, each assigned a unique orthogonal cover code. This segmentation enables broader geographic coverage through multi-sector transmission while maintaining detection accuracy by ensuring orthogonality within each subset, preventing signal interference even as coverage area expands.
Solution Approach 2:
The patent changes the parameter of orthogonality by applying different orthogonal cover codes to different sector subsets. This parameter change allows the system to maintain signal detection accuracy across expanded coverage areas, as the OCCs ensure that signals from different subsets remain orthogonal and non-interfering.
3Device complexity
If sectors use the same signal waveform, then system complexity is reduced, but signal distinguishability worsens
Solution Approach 1:
The patent maintains simple base signal waveforms but introduces orthogonality in the code domain through orthogonal cover codes. This dimensional approach preserves signal transmission simplicity while dramatically improving signal distinguishability, as receivers can easily differentiate between sectors using the orthogonal OCCs without increasing overall system complexity.
Data Source
AI summary
Briefly, in accordance with one embodiment, a method of transmitting signals is provided. Signal waveforms are transmitted from at least two respective sectors. The at least two respective sectors are from at least two different sets of a superset of sectors. The transmitted signal waveforms include signal waveforms at least nearly mutually orthogonal at least along a particular signal dimension. An advantage of such an embodiment, for example, is reduced signal interference.