Wireless Ranging Using Constant Processing Delay Indication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current Fine Time Measurement (FTM) ranging solutions in wireless communication systems are not optimal in terms of spectrum efficiency, especially in systems with a large number of stations, as they require multiple frame pairs and assume varying duration between message reception and acknowledgement, making it difficult for other devices to determine distance accurately.
Innovation Solution
The proposed solution involves transmitting a first frame and receiving a second frame with an indication of constant or variable duration between reception and transmission, allowing devices to determine distance based on this indication, potentially using a single frame pair exchange and enabling passive stations to calculate distance even when the duration is constant, by incorporating the delay information in beacon or acknowledgement frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple frame pairs are used for ranging measurements, then measurement precision is improved, but spectrum efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by having the second apparatus (AP) pre-indicate its processing duration (t2-t3) in advance, either as a constant value or through calibration. This allows the first apparatus (STA) to calculate distance using a single frame pair exchange, eliminating the need for multiple measurements while maintaining accuracy. The duration indication is provided beforehand in beacon frames or through calibration procedures, enabling efficient one-shot distance determination.
2Device complexity
If the duration between message reception and acknowledgement is assumed to be constant, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies parameter changes by allowing the duration parameter (t2-t3) to be dynamically indicated by the AP rather than being fixed or assumed. The AP can signal different duration values based on its processing load and capabilities, and can indicate whether the duration is constant or variable. This flexible parameter approach maintains measurement precision while adapting to different operational conditions, resolving the contradiction between simplicity and accuracy.
3Reliability
If passive stations cannot determine distance, then reliability is improved by reducing calculation errors, but adaptability deteriorates
Solution Approach 1:
The patent introduces an intermediary mechanism where the AP acts as a mediator by providing duration indication information to passive stations. When the AP indicates that its processing duration is constant, passive stations can use this information along with their received frame timestamps to calculate distances to the AP. The AP's duration indication serves as the intermediary data that enables passive stations to perform accurate distance determination without directly participating in the ranging exchange, thus improving both reliability and adaptability.
Data Source
AI summary
This document discloses a solution for determining distances. In the solution, a first frame is transmitted (200) to a second apparatus; a second frame is received (202) from the second apparatus, as response to the first frame; an indication of the duration between the reception time of the first frame and transmission of the second frame is received (204); an indication whether the duration is constant or variable is received (206); and in case the duration is constant, the distance between the first apparatus and the second apparatus is determined (208) based at least partly on the indication of the duration.