NDP Ranging Error Recovery for Indoor Positioning
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Solution Overview
Problem
Current wireless communication systems, particularly in WLANs, face challenges in accurately determining the position of communication devices within buildings or areas with obstructed GPS signals, as GPS technology is unreliable indoors and traditional positioning methods lack precision in such environments.
Innovation Solution
The method involves transmitting null data packets (NDPs) as part of ranging measurement exchanges between communication devices, with error recovery mechanisms to ensure correct packet reception, allowing for accurate distance calculations and location estimation using triangulation techniques, even in environments where GPS is unreliable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error recovery mechanisms are implemented in NDP ranging, then reliability of location determination is improved, but device complexity increases
Solution Approach 1:
The patent implements preliminary error detection and recovery mechanisms before location determination is compromised. The receiving device performs clear channel assessment (CCA) before transmitting NDPs and uses acknowledgment protocols to ensure reliable reception, preventing errors from affecting location calculations rather than correcting them after occurrence.
Solution Approach 2:
The patent employs feedback mechanisms where receiving devices send acknowledgment signals to transmitting devices to confirm successful NDP reception. This feedback loop enables the system to identify and recover from transmission errors, ensuring reliable location determination while managing protocol complexity through structured error handling procedures.
2Measurement precision
If multiple ranging measurement exchanges are performed, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs ranging measurement exchanges in periodic cycles where multiple NDP transmissions are conducted in sequence. Each exchange follows a structured timeline with predetermined intervals between measurements, allowing the system to accumulate precise distance data through multiple samples while managing time consumption through efficient periodic scheduling rather than continuous measurement.
Data Source
AI summary
A first communication device transmits a first physical layer protocol data units (PPDU) that includes a first null data packet announcement (NDPA) frame as part of a first ranging measurement exchange. The first communication device transmits a first null data packet (NDP) as part of the first ranging measurement exchange, and records a transmit time of the first NDP. The first communication device determines whether a second NDP was received correctly from a second communication device as part of the first ranging measurement exchange. In response to determining that the second NDP was not received correctly, the first communication device commences a second ranging measurement exchange, including transmitting a second PPDU that includes a second NDPA frame as part of the second ranging measurement exchange.