Fractional Frequency Offset Estimation via Power Threshold Control
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Solution Overview
Problem
In Broadband Wireless Access systems employing beam forming, the initial fractional frequency offset estimation process suffers from throughput deterioration due to the accumulation of invalid correlation values when beam forming is applied to symbols without data, as the presence or absence of DownLink symbol data cannot be determined before network synchronization is achieved.
Innovation Solution
A symbol power calculator and a comparator are introduced to calculate the average power of DownLink-MAP symbols, determining whether to apply beam forming to subsequent symbols based on power thresholds, thereby controlling correlation accumulation and distinguishing between data and non-data symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam forming is applied to symbols without data, then the system can serve multiple user terminals, but invalid correlation values are accumulated causing throughput deterioration in frequency offset estimation
Solution Approach 1:
The patent applies preliminary action by calculating the average power of DL-MAP symbols before processing subsequent symbols. This pre-computed power threshold is used to determine whether beam forming is applied to later symbols, allowing the system to proactively identify and exclude invalid correlation values before they degrade the frequency offset estimation throughput
Solution Approach 2:
The patent introduces power threshold comparison as an intermediary mechanism between beam forming application and correlation accumulation. By using the average power of DL-MAP symbols as a reference threshold, the system can indirectly determine the presence of data in symbols without direct network synchronization, thus preventing invalid correlation values from being accumulated
2Ease of operation
If correlation accumulation is performed on all symbols, then the estimation process is simple, but invalid correlation values from non-data symbols reduce estimation accuracy
Solution Approach 1:
The patent performs preliminary power calculation and threshold comparison before correlation accumulation. By computing the average power of DL-MAP symbols in advance and comparing it with subsequent symbols, the system pre-identifies which symbols contain valid data, allowing selective accumulation that maintains estimation accuracy while preserving operational simplicity
Solution Approach 2:
The patent extracts and removes invalid correlation values from the accumulation process. By using power threshold comparison to identify symbols without data, the system selectively excludes these symbols from correlation accumulation, thereby preventing degradation of frequency offset estimation accuracy while maintaining the overall simplicity of the accumulation mechanism
Data Source
AI summary
An apparatus and method for initial fractional frequency offset estimation are provided. In an apparatus for estimating an initial fractional frequency offset in a Broadband Wireless Access (BWA) communication system, the apparatus includes a sample power calculator for calculating a power of input sample data and for calculating an average power of a specific symbol, a power threshold comparator for comparing the sample data power in magnitude with the average power of the specific symbol and for outputting one of an accumulation ON and OFF signal, a first buffer for correlating a last data of the sample data with the sample data and for storing sample data corresponding to a preset number of correlation results, a second buffer for storing sample data corresponding to correlation results other than the sample data stored in the first buffer; and an accumulator for allowing accumulation of sample data stored in the second buffer if the power threshold comparator outputs the accumulation ON signal.