Joint Maximum Likelihood Time-of-Arrival Estimation in Multipath Channels for Device Positioning in LTE Networks

Relevance. Despite the development of 5G technologies, the use of 4G remains relevant. Moreover, the LTE radio interface parameters underlie NR, making the results obtained for LTE applicable to NR. Positioning in LTE networks is based on ToA signal arrival time measurements. Non-line-of-sight conditions in a multipath channel cause significant ToA estimation errors, requiring the development of compensation methods to improve positioning accuracy.

The aim of this work is to improve the accuracy of ToA measurements in non-line-of-sight conditions by researching and developing methods for joint maximum-likelihood (JML) ToA estimation in a multipath channel.

Results. The 2D-JML method is shown to be more effective than 1D-JML, especially in scenarios with closely spaced multipath components typical of small-bandwidth signals. This improvement is achieved through a scientifically justified selection of the number of signal samples at the multipath channel output. It was found that in the EPA, EVA, and ETU models at C/N₀ = 85 dB∙Hz, after interference elimination, the ranging accuracy of 2D-JML measurements with a hybrid sampling model ranges from 26 to 60 m for a 1.4 MHz bandwidth and less than 4 m for 20 MHz.

Novelty. For the first time, a comprehensive scientific justification of the bandwidth and number of samples for the joint maximum-likelihood ToA estimation method in a multipath channel is presented in typical LTE device positioning scenarios to achieve meter-level accuracy of ranging measurements.

The theoretical significance. The theoretical foundations for signal arrival time estimation in multipath LTE channels are refined. The proposed JML ToA estimation method expands on the classical maximum likelihood method by taking into account the channel structure and allowing for closer approximation to the CRLB. The results can be used in the further development of OFDM-based positioning theory.

The practical significance. The JML method can be implemented in existing LTE/LTE-A devices to improve positioning accuracy without changing the network infrastructure. The results obtained are also applicable to the development of positioning algorithms for future 5G networks.

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