Frequency Offset Estimation for LTE Uplink Frequency Hopping
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Solution Overview
Problem
Existing frequency offset estimation methods in LTE systems, particularly for uplink reception, are inadequate when frequency hopping is employed and consume excessive computation and power resources, limiting their effectiveness and efficiency.
Innovation Solution
A method that estimates frequency offset by determining phase change candidates between a data symbol and a reference symbol, rotating constellation symbols, and selecting the phase change candidate that best matches constellation points, thereby reducing computational and power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the prior art frequency offset estimation approach using phase change between two reference symbols is applied, then frequency offset can be estimated, but it cannot be applied when frequency hopping is employed in the uplink
Solution Approach 1:
The patent segments the frequency offset estimation process into multiple candidate phase changes, each corresponding to different frequency hopping patterns. By dividing the estimation into discrete candidates rather than a single continuous measurement, the method can accommodate different frequency hopping scenarios while maintaining estimation accuracy.
Solution Approach 2:
The patent introduces dynamic selection of phase change candidates based on the actual frequency hopping pattern detected in the received signal. The estimation method adapts to changing frequency allocations by selecting the appropriate phase change candidate that matches the observed hopping behavior, making it versatile for different uplink configurations.
2Measurement precision
If multiple frequency offset candidates are tested by decoding the received OFDM signal multiple times, then accurate frequency offset can be determined, but large amounts of computation and power resources are consumed
Solution Approach 1:
The patent applies partial action by testing only a limited set of pre-determined frequency offset candidates rather than exhaustively searching all possible frequency offsets. This selective approach maintains sufficient estimation accuracy while significantly reducing the number of decoding attempts required, thereby lowering power consumption.
Solution Approach 2:
The patent performs preliminary identification of frequency hopping patterns and pre-determines a small set of likely frequency offset candidates before attempting signal decoding. This preliminary action narrows down the search space, allowing accurate frequency offset determination with minimal decoding attempts and reduced energy expenditure.
3Measurement precision
If multiple frequency offset candidates are tested by decoding the received OFDM signal multiple times, then accurate frequency offset can be determined, but high costs are incurred for the eNB and UE
Solution Approach 1:
The patent implements partial action by limiting the frequency offset candidate testing to a small, pre-determined set based on frequency hopping pattern analysis. This approach achieves sufficient estimation precision while avoiding the computational burden of testing all possible frequency offsets, thereby reducing device complexity and processing requirements.
Solution Approach 2:
The patent extracts and utilizes the frequency hopping pattern information from the received signal to identify and eliminate unlikely frequency offset candidates. By taking out the relevant hopping pattern features and using them to filter the candidate set, the method reduces computation resources while maintaining estimation accuracy.
Data Source
AI summary
The present disclosure provides a method implemented in a wireless communication device for estimating a frequency offset between a carrier frequency of a received signal and a frequency of a local oscillator as well as the wireless communication device. The method comprises determining a plurality of phase change candidates for a phase change between a data symbol and a first reference symbol in the signal. The method further comprises generating a collection of constellation symbols from the data symbol and rotating the collection of constellation symbols by the plurality of phase change candidates. Then, one of the phase change candidates corresponding to one of the rotated collections of constellation symbols is selected in such a manner that said one of the rotated collections of constellation symbols matches a set of constellation points best. Next, the frequency offset is determined based on the selected phase change candidate.