Wireless Station ToF Positioning via Reverse-Direction Grant
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Solution Overview
Problem
Accurate and real-time indoor navigation and positioning are challenging due to the absence of satellite and cellular signal reception in indoor environments, necessitating improved methods for location determination in wireless networks.
Innovation Solution
The implementation of time-of-flight (ToF) positioning using a reverse-direction grant (RDG) mechanism, eliminating the need for a final acknowledgement frame, and incorporating aggregated media-access-control protocol data units (A-MPDU) to enhance measurement accuracy and reduce channel access attempts in IEEE 802.11 wireless networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional outdoor navigation systems are used in indoor environments, then satellite and cellular signal reception is required, but indoor environments block these signals making positioning inaccurate or impossible
Solution Approach 1:
The patent introduces wireless stations and time-of-flight measurement mechanisms as intermediaries between the positioning system and the indoor environment. Instead of relying on external satellite/cellular signals that are blocked by buildings, the system uses local wireless stations within the indoor environment to perform ToF measurements, creating a mediator layer that enables positioning without direct external signal reception
Solution Approach 2:
The patent replaces the traditional satellite-based electromagnetic signal system with a wireless network-based time-of-flight measurement system. This substitution involves using Wi-Fi or similar wireless communications to transmit timing information between stations, replacing the mechanical/physical dependency on satellite signal propagation through the atmosphere and building structures
2Reliability
If multiple channel access attempts are made to ensure message delivery, then message delivery reliability improves, but channel access delays and collisions increase
Solution Approach 1:
The patent applies preliminary action by having the initiating station send a reverse-direction grant (RDG) indication in advance, which pre-authorizes the responding station to transmit its message. This preliminary grant reduces the need for multiple channel access attempts and retransmissions, as the responding station already has permission to transmit when its message is ready, thereby reducing channel access delays while maintaining delivery reliability
Solution Approach 2:
The patent implements feedback mechanisms where stations acknowledge receipt of messages and timing information. The initiating station receives timing measurements from the responding station, and both stations can request retransmission if messages are not properly received. This feedback loop ensures reliable message delivery while allowing the system to adapt to channel conditions and minimize unnecessary retransmissions
Data Source
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AI summary
Embodiments of a communication station (STA) and method for time-of-flight (ToF) positioning in a wireless network are generally described herein. In some embodiments, an initiating station may transmit a message M1 carrying a high-throughput control (HTC) field that includes a reverse direction grant (RDG) bit. The RDG indication grants permission to a responding station to send information back to the initiating station. The message M1 may be a timing measurement action frame. An ACK frame may be received from the responding station to acknowledge receipt of the message M1. The ACK frame may optionally carry an HTC field that includes a more PPDU indication to indicate whether a PPDU (e.g., contained in message M2) is to follow the ACK frame. The message M2 may be received from the responding station and may include timing measurement information from a current and/or one or more previous ToF message exchanges.