OTDOA Positioning in LAA Unlicensed Spectrum
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Solution Overview
Problem
The challenge in accurately determining the position of user equipment (UE) in wireless communication systems using unlicensed spectrum, particularly with small cell access points, due to less precisely coordinated and synchronized Positioning Reference Signals (PRS) transmitted by small cells, which impede accurate location measurement.
Innovation Solution
A method involving UE measuring PRS from multiple secondary cells at different positioning occasions, reporting these measurements to a location server, which determines the UE's position based on the transmission times and measurement times of PRS from multiple eNBs, enhancing positioning accuracy by coordinating PRS configurations across secondary cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If Positioning Reference Signals (PRS) are transmitted by small cell access points using LAA, then the coverage and capacity of the network are improved, but the accuracy of position measurement deteriorates due to less precise signal coordination and synchronization
Solution Approach 1:
The network configures and provides positioning assistance data to the UE in advance, including information about PRS resources, timing, and frequency for multiple secondary cells. This preliminary configuration enables the UE to accurately measure PRS signals from multiple small cells despite their unsynchronized transmission, resolving the measurement accuracy issue while maintaining expanded coverage
Solution Approach 2:
A location server acts as an intermediary to coordinate PRS transmissions from multiple small cell eNBs. The location server provides synchronization information and positioning assistance data that mediates between the unsynchronized small cell transmissions and the UE's measurement requirements, enabling accurate positioning across the expanded LAA coverage area
2Measurement precision
If PRS transmissions from multiple secondary cells are used for positioning, then the positioning accuracy can be improved, but the complexity of coordinating and synchronizing signals across multiple eNBs increases
Solution Approach 1:
The location server serves as a central intermediary that manages PRS coordination across multiple eNBs. It generates and distributes positioning assistance data containing synchronization information, resource configurations, and timing details to both eNBs and UEs, thereby simplifying the coordination complexity while enabling accurate multi-cell positioning measurements
Solution Approach 2:
The system configures PRS parameters such as periodicity, subframe offset, and resource allocation for each secondary cell to ensure proper synchronization and measurement opportunities. By carefully adjusting these parameters, the system achieves accurate positioning measurements while managing the coordination complexity through standardized parameter sets
3Productivity
If small cell access points transmit PRS signals in unlicensed spectrum, then spectral efficiency is enhanced, but the reliability of location measurement deteriorates due to interference and less precise coordination
Solution Approach 1:
The network provides positioning assistance data to the UE in advance, including information about PRS resources, timing, frequency, and expected signal characteristics from multiple secondary cells. This preliminary information enables the UE to reliably measure and interpret PRS signals in the interference-prone unlicensed spectrum, maintaining measurement reliability while utilizing the high spectral efficiency of LAA
Solution Approach 2:
The UE reports measurement results and timing information back to the location server, which uses this feedback to refine positioning calculations and provide updated assistance data. This feedback mechanism enhances the reliability of location measurements by continuously optimizing the positioning process based on actual measurement conditions in the unlicensed spectrum
Data Source
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AI summary
Disclosed are techniques for determining a location of a user equipment (UE) communicating over a shared communication medium in unlicensed spectrum. In an aspect, the UE measures a positioning reference signal (PRS) from a first evolved NodeB (eNB) for a first secondary cell (Scell) and a second PRS from a second eNB for a second Scell. The UE reports the first and second PRS measurements and the first and second PRS measurement times to a location server. In an aspect, the first and second PRS are configured according to a common PRS configuration. The location server also receives transmission times of the PRS signals from the first and second eNBs. Using the measurement and transmission times, the location server can associate the first PRS measurement to the first eNB and the second PRS measurement to the second eNB, thereby assisting the location server to obtain a location for the UE..