IoT Location Tracking Using Midamble Antenna Switching
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Solution Overview
Problem
Smaller IoT devices with poor antenna patterns and constant motion face challenges in location tracking due to multipath and changing channels, as existing wireless protocol standards like IEEE 802.11ax do not effectively mitigate location tracking accuracy errors.
Innovation Solution
Implementing midambles in data payloads to enable switching of radio paths during reception, allowing for accurate location estimation by capturing RF and baseband information across multiple antennas, thereby improving location accuracy, latency, and battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional location tracking methods (AoA, ToF) are used for IoT devices, then location estimation is supported, but location tracking accuracy deteriorates due to multipath and constantly changing channels from device motion
Solution Approach 1:
The system performs preliminary channel estimation using midambles inserted within the data payload before the actual data reception is complete. This preliminary estimation allows the receiver to compensate for channel variations and multipath effects that occur during the entire transmission, improving location tracking accuracy despite device motion.
Solution Approach 2:
Midambles serve as intermediary reference signals inserted within the data payload. These midambles provide a stable reference for channel estimation that mediates between the transmitted signal and the received signal, allowing the system to accurately estimate location parameters even when the channel is constantly changing due to device motion.
2Reliability
If antenna switching is performed during data payload reception, then receive diversity and location estimation robustness are improved, but device complexity increases
Solution Approach 1:
The data payload is segmented into multiple portions with midambles inserted between them. This segmentation allows the receiver to switch between different antenna elements at each midamble boundary, capturing diverse signal paths and improving location estimation robustness without requiring complex continuous switching mechanisms.
Solution Approach 2:
Antenna switching is performed periodically at fixed intervals corresponding to the midamble positions within the data payload. This periodic switching pattern simplifies the implementation compared to continuous switching, as the antenna selector can operate in a rhythmic, predictable manner synchronized with the midamble insertion pattern.
3Measurement precision
If more antennas are used for location estimation, then measurement precision improves, but use of energy increases
Solution Approach 1:
The system uses more antennas than strictly necessary for basic location estimation, but only activates a subset of antennas at any given time through periodic switching. This partial action approach allows the device to have the capability of using multiple antennas for improved precision while consuming less energy by not continuously operating all antennas at full power.
Data Source
AI summary
In one embodiment, a technique for Internet of Things (IoT) device location tracking using midambles is provided. A first wireless device in connection with an antenna array may receive one or more first data symbols of a data payload from a second wireless device using a first antenna state that assigns a radio path, used for location estimation, to a first antenna of the antenna array. Subsequent to identifying a first midamble of the data payload, the first wireless device may change the first antenna state to a second antenna state that assigns the radio path to a second antenna of the antenna array. The first wireless device may receive one or more second data symbols of the data payload using the second antenna state. The first wireless device may determine a location of the second wireless device based on location information determined using the radio path.