Ranging Apparatus Using Orthogonal Coded Modulation for Indoor Positioning
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Solution Overview
Problem
Indoor location-based services face challenges with satellite-based positioning systems due to poor signal reception and resolution, and simultaneous ranging to multiple objects in indoor environments is hindered by signal interference, making it difficult to accurately determine the position of objects using conventional channel estimation methods.
Innovation Solution
The implementation of a ranging procedure using interference cancellation through pre-defined orthogonal design coded modulation patterns in preamble messages, allowing for simultaneous communication and accurate channel estimation and position determination of multiple objects by removing interference between signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple objects transmit preamble messages simultaneously for ranging, then productivity of simultaneous tracking is improved, but signal interference increases making channel estimation difficult
Solution Approach 1:
The system segments the simultaneous transmission into orthogonal components by assigning different orthogonal codes to different objects. Each object's preamble message is modulated with a unique orthogonal code, allowing the receiver to separate and estimate channels for multiple objects simultaneously without interference, thus resolving the contradiction between simultaneous tracking and signal interference.
Solution Approach 2:
The system changes the modulation parameter by using orthogonal coded modulation patterns instead of conventional modulation. This parameter change enables the preambles from multiple objects to be orthogonally separated at the receiver, allowing simultaneous ranging while eliminating mutual interference between objects' signals.
2Measurement precision
If conventional channel estimation is used with simultaneous transmissions, then device complexity is maintained, but measurement precision deteriorates due to interference
Solution Approach 1:
The system applies preliminary action by pre-modulating each object's preamble message with a unique orthogonal code before transmission. This preliminary coding enables the receiver to easily separate and estimate channels for multiple objects using simple correlation operations, achieving high measurement precision without increasing device complexity.
Data Source
AI summary
A ranging procedure is performed using interference cancellation using preamble messages from a plurality of objects, each of which includes a pre-defined orthogonal design coded modulation patterns. A channel for an object may be estimated using the pre-defined orthogonal design coded modulation patterns in the preamble messages received from objects to remove interference of the preamble message received from other objects. A range to an object may be determined based on a determined delay in the preamble message from that object. The range may be used to assist in determining the position of the object. The pre-defined preamble message may be transmitted by receiving a schedule for an access point in a network for a ranging procedure and periodically transmitting a pre-defined preamble message for the ranging procedure, the pre-defined preamble message includes an orthogonal design coded modulation pattern.