Pilot Sequence Detection Using Frequency-Domain Sliding Correlator
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Solution Overview
Problem
Conventional algorithms for detecting the secondary synchronization channel (S-SCH) in UTRAN LTE systems face performance issues due to a large number of non-empty sub-carriers mapped to system information or data in OFDM symbols, leading to compromised detection accuracy and increased complexity.
Innovation Solution
A frequency division permanent common pilot detection method using a sliding correlator with a phase-shift in the frequency domain, combined with averaging and threshold mechanisms, to determine the pilot sequence in a time-division multiplexed pilot structure, which reduces false detection and improves accuracy by averaging peak magnitudes over sub-frames and selecting the pilot sequence index candidate with the lowest peak ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional time-domain algorithms are used for pilot sequence detection, then the detection process is simple to implement, but the detection accuracy is severely compromised due to a large number of non-empty sub-carriers mapped to system information or data
Solution Approach 1:
The patent transitions from time-domain processing to frequency-domain processing by applying FFT to the received OFDM symbol. This dimensional change allows the algorithm to operate on frequency-domain representations where pilot sub-carriers can be identified and processed more effectively, resolving the contradiction between implementation simplicity and detection accuracy.
Solution Approach 2:
The patent segments the frequency-domain signal by identifying specific pilot sub-carrier positions and extracting them separately from other sub-carriers carrying system information or data. This segmentation enables selective processing of pilot signals, improving detection accuracy while maintaining computational efficiency through focused operations on relevant signal components.
2Quantity of substance
If a scattered pilot structure with many sub-carriers allocated to system information is used, then the system information capacity is improved, but the pilot sequence detection performance is degraded
Solution Approach 1:
The patent extracts pilot sub-carriers from the composite OFDM signal by identifying their specific frequency positions and separating them from sub-carriers carrying system information. This extraction process allows independent processing of pilot signals, ensuring reliable detection performance even when many sub-carriers are allocated to system information.
Solution Approach 2:
The patent introduces frequency-domain processing as an intermediary step between receiving the OFDM symbol and detecting the pilot sequence. This intermediary approach enables the system to handle scattered pilot structures effectively by transforming the signal representation, allowing simultaneous support for high system information capacity and reliable pilot detection.
3Measurement precision
If sliding correlator with phase-shift in frequency domain is used, then the detection accuracy is significantly enhanced, but the computational complexity increases
Solution Approach 1:
The patent applies FFT transformation as a preliminary action to convert the time-domain OFDM symbol into frequency-domain representation before performing correlation operations. This preliminary transformation simplifies subsequent processing by enabling efficient frequency-domain correlation with reduced computational complexity compared to time-domain approaches.
Solution Approach 2:
The patent changes the domain parameter from time-domain to frequency-domain processing. This parameter change enables the use of efficient frequency-domain correlation algorithms that achieve high detection accuracy while reducing overall computational complexity through the mathematical properties of FFT-based processing.
Data Source
AI summary
A user equipment and corresponding method detect a frequency division permanent common pilot and include a controller configured to use a sliding correlator with a frequency division phase-shift, an averaging unit configured to average a peak magnitude output of the sliding correlator over a predetermined number of sub-frames for each of possible reference pilot sequence and each sample shift of the sliding correlator, and a maximum peak storing unit configured to store first and second maximum peaks depending on corresponding ratios and a threshold. The user equipment and method thereof also include a pilot sequence index candidate storing unit configured to store a pilot sequence index candidate for each shift of the sliding correlator. The user equipment and method thereof include a selector configured to select the pilot sequence index candidate with a lowest peak ratio to shift the sliding correlator.