MIMO Location Estimation via Per-Chain SNR Filtering
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Solution Overview
Problem
In MIMO wireless networks, existing location estimation methods face challenges due to the variability of RSSI/SNR measurements across multiple chains, leading to inaccuracies in location determination, especially in environments with multipath and NLOS conditions.
Innovation Solution
The system determines path loss per RF subcarrier by obtaining feedback information, deriving received signal strength values, and calculating effective radiated power to accurately estimate location, while discarding unsuitable data and selecting suitable signal strength values to improve estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple chains are used for spatial multiplexing and advanced MIMO techniques, then communication reliability and performance are improved, but RSSI/SNR measurement accuracy deteriorates due to variability across chains
Solution Approach 1:
The patent segments the RSSI/SNR measurement process by analyzing each RF chain individually rather than using a single aggregated value. It divides the measurement into per-chain components, allowing identification of which chains provide reliable measurements and which are affected by multipath or NLOS conditions. This segmentation enables the system to select appropriate chains for location estimation while excluding problematic ones.
Solution Approach 2:
The patent applies local quality by evaluating the measurement characteristics of each RF chain separately. Instead of treating all chains uniformly, it assesses the local quality of each chain's signal path (direct, multipath, or NLOS) and uses this information to weight or select chains appropriately for location estimation, thereby improving overall measurement accuracy.
2Productivity
If all received chains are used to receive frames with maximal ratio combining, then communication performance is improved, but location estimation accuracy deteriorates due to highly variable RSSI/SNR measurements
Solution Approach 1:
The patent extracts and removes problematic measurement data from the location estimation process. It identifies chains or measurements affected by multipath or NLOS conditions and excludes them from the location calculation, while still using all chains for communication purposes. This extraction ensures that only reliable measurements contribute to location estimation.
Solution Approach 2:
The patent employs feedback mechanisms where the receiver provides channel state information back to the transmitter, enabling the system to identify and report which chains have reliable signal paths. This feedback loop allows the system to dynamically adjust which chains are used for location estimation based on real-time channel conditions.
3Loss of information
If per-chain RSSI/SNR measurements are reported to applications, then measurement detail is improved, but system complexity increases due to multiple chains and processing requirements
Solution Approach 1:
The patent merges the complex per-chain measurement data into a simplified location estimation process. Instead of processing all individual chain measurements separately, it combines the information to identify reliable chains and uses this synthesized information for location calculation, reducing the processing burden while maintaining accuracy.
Data Source
AI summary
Disclosed herein, one embodiment of the disclosure is directed to a system, apparatus, and method for location estimation in the presence of multipath/non-line-of-sight (NLOS) conditions. Various methods have been contemplated to detect the level of multipath/NLOS propagation between two devices. A SNR variation method determines how the SNR of each chain/stream is varying over a time window in order to detect the chain/stream with least local scattering or multipath. A measure of coherence SNR is defined to measure the level of multipath/NLOS per-chain/stream. Moreover, since per-subcarrier SNR information is available at the one or both nodes, the coherence methods can be used on a per-subcarrier basis to detect multipath/NLOS for the entire channel, for the specific spatial stream or for the specific frequencies occupied by the subcarriers. Furthermore, a coherence bandwidth estimation method uses the SNR variation over subcarriers to detect the coherence bandwidth of the spatial stream. The amount of multipath/NLOS is inversely proportional to the coherence bandwidth.