Randomizing PRS Frequency Offsets and Muting Patterns in LTE
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Solution Overview
Problem
Conventional wireless communication systems face challenges in accurately determining the location of user equipment (UE) due to interference from secondary correlation peaks in positioning reference signal (PRS) decoding, which affects the time-of-flight measurements used in location estimation processes like trilateration and triangulation.
Innovation Solution
Randomization of PRS frequency offsets and muting patterns in LTE networks is implemented by using a random number generator to dynamically select frequency tone offsets and muting sequences, allowing UE to measure PRS from more neighboring base stations and improve the accuracy of observed time difference of arrival (OTDOA) estimations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PRS decoding is used, then the system can determine time-of-flight intervals, but secondary correlation peaks cause interference and reduce measurement precision
Solution Approach 1:
The patent applies dynamics by making the PRS configuration dynamic through randomization. Specifically, the frequency offset and muting pattern are randomized across different PRS occasions, transforming the static PRS structure into a dynamic one. This randomization causes secondary correlation peaks to vary in position and magnitude over time, preventing them from consistently interfering with the main correlation peak and thereby improving time-of-flight measurement precision.
Solution Approach 2:
The patent changes key parameters of the PRS signal, specifically the frequency offset and muting pattern parameters. By randomizing these parameters across different PRS occasions, the system alters the temporal and spectral characteristics of the signal. This parameter randomization transforms the deterministic interference pattern into a stochastic one, reducing the impact of secondary correlation peaks on measurement accuracy.
2Reliability
If PRS is transmitted from multiple base stations, then location estimation can be performed, but interference increases and hearability decreases
Solution Approach 1:
The patent makes the PRS transmission dynamic by implementing randomization of frequency offsets and muting patterns across multiple base stations. Each base station randomizes its PRS configuration independently, creating a dynamic interference environment where secondary correlation peaks from different stations do not align consistently. This dynamic approach improves hearability by preventing persistent interference patterns that would otherwise accumulate from multiple transmitters.
Solution Approach 2:
The patent changes the transmission parameters (frequency offset and muting pattern) for PRS signals from multiple base stations. By randomizing these parameters, the system ensures that PRS signals from different base stations have different temporal-spectral signatures. This parameter diversification reduces constructive interference and allows the UE to more reliably detect and measure PRS from multiple sources, improving location positioning reliability.
3Measurement precision
If static PRS configuration is used, then implementation is simple, but accuracy of OTDOA estimation is limited
Solution Approach 1:
The patent introduces dynamics into the PRS configuration through randomization, where frequency offsets and muting patterns vary across different PRS occasions. This dynamic configuration improves OTDOA estimation precision by reducing the impact of secondary correlation peaks. The complexity increase is managed through algorithmic generation of random sequences, which maintains implementation feasibility while achieving superior measurement accuracy.
Solution Approach 2:
The patent changes the PRS configuration parameters from static to randomized values. The frequency offset and muting pattern parameters are randomly selected for each PRS occasion, creating parameter diversity that improves OTDOA estimation. The complexity introduced is offset by the use of standardized random number generation algorithms and the fact that the randomization follows defined patterns that can be replicated by both transmitting and receiving devices.
Data Source
AI summary
Certain aspects of the present disclosure generally relate to randomization of positioning reference signal (PRS) frequency offsets and muting patterns in long term evolution (LTE) for enhanced observed time difference of arrival (eOTDOA). According to certain aspects, a method is provided for wireless communications which may be performed, for example, by a base station (BS). The method generally includes randomly selecting at least one parameter used to determine a set of time-frequency resources for transmitting positioning reference signals (PRS) and transmitting PRS on the determined set of time-frequency resources. The user equipment (UE) may randomly select the at least one parameter used to determine the set of time-frequency resources to measure for the PRS from the BS and measure PRS on the determined set of time-frequency resources.