Frequency Error Estimation Using Irregular Pilot Intervals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional frequency error estimation methods in mobile telecommunication systems, such as UMTS LTE, are insufficient for accurately detecting large frequency errors due to their limited range, which affects reliable data transmission in OFDM systems with closely allocated subcarriers.
Innovation Solution
A method that estimates phase rotation indicators from differences between pilot symbols received at varying time intervals, calculating frequency error estimates from phase differences between these indicators, allowing for improved frequency error estimation by utilizing irregular time intervals and interpolating additional pilot symbols to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional frequency error estimation method using fixed time interval between pilot symbols is used, then the estimation process is simple, but the maximum detectable frequency error is limited to +-1 kHz which is insufficient for mobile environments
Solution Approach 1:
The patent divides the frequency error estimation into multiple segments by using different time intervals (first time interval and second time interval) between pilot symbol pairs. This segmentation allows the system to estimate frequency errors across a broader range by combining results from multiple interval measurements, thereby extending the detectable frequency error range beyond the conventional single-interval limitation.
Solution Approach 2:
The patent introduces a new dimension to the estimation process by utilizing multiple time intervals instead of a single fixed interval. This dimensional expansion from one-time-interval estimation to multi-time-interval estimation enables the system to capture frequency error characteristics across different time scales, significantly extending the maximum detectable frequency error to +-7 kHz.
2Measurement precision
If pilot symbols are transmitted at fixed regular intervals according to current standard, then the transmission structure is simple and standardized, but the frequency error estimation range is limited and cannot accurately detect large frequency errors
Solution Approach 1:
The patent applies dynamics by making the time interval between pilot symbols variable rather than fixed. The system dynamically selects different time intervals (first time interval for one pair of pilot symbols, second time interval for another pair) based on the estimation requirements. This dynamic interval selection enables the system to adapt to different frequency error magnitudes, improving both detection accuracy and versatility across mobile communication scenarios.
Solution Approach 2:
The patent changes the time interval parameter between pilot symbol transmissions from a fixed standardized value to multiple variable values. By transmitting pilot symbols at different time intervals and using these varied intervals for estimation, the system can accurately detect frequency errors across a wider range, thereby improving adaptability to different frequency error conditions while maintaining standardized transmission structures.
Data Source
Figure 1~3
Figure 4~6C
Figure 7~8
AI summary
A frequency error estimation algorithm is presented for use in radio receivers, for example. The present algorithm utilizes irregular time intervals between pilot symbols to improve the frequency range of the estimate. First, a first phase rotation indicator comprising information on phase rotation of a received signal within a first time interval is estimated. Then, a second phase rotation indicator comprising information on phase rotation of the received signal within a second time interval of a different length than the first time interval is estimated. A frequency error estimate is calculated from the phase difference between the first phase rotation indicator and the second phase rotation indicator, for example by dividing the phase difference by the difference in the lengths of the first and the second time interval.