OFDM Positioning Pilot Channel for Mobile Device Location
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Solution Overview
Problem
Current positioning systems in wireless communication networks, such as GPS, are not robust in environments like tunnels or buildings due to weak satellite signals, necessitating a more reliable method to determine device positions within these networks.
Innovation Solution
A positioning system that uses Orthogonal Frequency Division Multiplexing (OFDM) to transmit Positioning Pilot Channel (PPC) symbols, allowing devices to determine their location by identifying multiple transmitters and calculating their channel estimates, enabling triangulation for accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If satellite positioning systems (GPS) are used to determine device positions, then positioning service is provided, but the system becomes unreliable in environments like tunnels or buildings due to weak satellite signals
Solution Approach 1:
The patent introduces terrestrial base stations as intermediary elements to provide positioning signals. Instead of relying directly on satellite signals that penetrate buildings and tunnels, the system uses local base stations that transmit positioning reference signals (PRS) through the positioning channel. These intermediary base stations act as mediators between the satellite system and the mobile device, providing reliable positioning signals in environments where direct satellite reception is blocked or weakened.
2Reliability
If conventional positioning systems are used, then positioning is provided, but the system lacks robustness in challenging environments
Solution Approach 1:
The patent makes the positioning system universal by enabling it to function across diverse environments (outdoor, indoor, urban canyons, tunnels) using the same underlying mechanism. The base station-based positioning reference signal system provides a unified approach that works regardless of the specific environment, making the system adaptable to various conditions without requiring environment-specific modifications. The positioning channel carries PRS that can be received and processed by mobile devices in any location within network coverage.
3Measurement precision
If base station signals are used for positioning, then positioning accuracy is improved in challenging environments, but the device complexity increases due to channel estimation requirements
Solution Approach 1:
The patent applies preliminary action by having base stations pre-transmit positioning reference signals (PRS) on dedicated positioning channels before actual positioning measurements are needed. These reference signals are prepared in advance and include known sequences that enable mobile devices to perform channel estimation. By having the reference signals pre-transmitted and structured in a known format, the device can efficiently estimate channel conditions without requiring complex real-time processing, thus reducing device complexity while maintaining positioning accuracy.
Data Source
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AI summary
Method and apparatus for position location in a wireless network. In an aspect, the method comprises: determining one or more identities of one or more transmitters based on a plurality of received OFDM symbols, wherein the plurality of received OFDM symbols are partitioned by subcarriers and time and wherein one or more active portions of the plurality of received OFDM symbols comprises the identification information for a transmitter; determining one or more channel estimates associated with the one or more transmitters; and determining the position of the device based at least in part on the one or more identities of the one or more transmitters and the one or more channel estimates.