OFDM Receiver Bootstrap Processing for Frequency Offset Detection
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Solution Overview
Problem
There is a need for an efficient and cost-effective technique to detect payload data carried by OFDM symbols using the bootstrap signal in radio communications systems, as the robust encoding of the bootstrap signal makes individual signalling bits resource-intensive and difficult to detect accurately.
Innovation Solution
A receiver is designed with a radio frequency demodulation circuit, a detector circuit, and a bootstrap processor that includes an up-sampler, cross-correlator, and output processor to accurately detect and recover payload data from OFDM symbols. The bootstrap processor up-samples the bootstrap OFDM symbols, cross-correlates them with a signature sequence, and determines the frequency offset and channel transfer function to improve detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If robust encoding is used for the bootstrap signal to ensure detectability at low signal levels, then the reliability of signal detection is improved, but the resource consumption increases and detection accuracy deteriorates
Solution Approach 1:
The patent segments the frequency offset estimation process into two distinct stages: coarse frequency offset estimation using the robust bootstrap signal, and fine frequency offset estimation using the payload data. This segmentation allows each stage to use optimization strategies appropriate to its specific requirements, resolving the contradiction between robustness and precision.
Solution Approach 2:
The patent applies preliminary action by using the robustly encoded bootstrap signal to perform coarse frequency offset estimation and channel estimation before processing the payload data. This preliminary estimation removes the dominant error sources, allowing subsequent fine estimation to achieve higher precision without being overwhelmed by the limitations of robust encoding.
2Reliability
If robust encoding is used for the bootstrap signal, then the reliability of detection is improved, but the productivity of data transmission decreases due to resource-intensive signalling
Solution Approach 1:
The patent applies partial action by using the robust bootstrap signal only for the minimum necessary function of providing coarse frequency and channel estimates, rather than attempting to extract all information from it. This limited use of robust encoding reduces its resource consumption impact while maintaining detection reliability.
Solution Approach 2:
The patent creates a simplified copy of the frequency offset estimation problem by first solving it coarsely using the bootstrap signal, then solving it finely using the payload data. This two-copy approach allows the system to benefit from robust encoding only where absolutely necessary, improving overall transmission efficiency.
3Device complexity
If the bootstrap signal carries minimal information for system discovery, then the device complexity is reduced, but the measurement precision of frequency offset estimation deteriorates
Solution Approach 1:
The patent segments the estimation task into two parts: a simple coarse estimation using the minimal-information bootstrap signal, and a more complex fine estimation using the payload data. This segmentation allows the receiver to maintain low complexity for the critical initial detection while achieving high precision for the subsequent data processing.
Solution Approach 2:
The patent performs preliminary coarse estimation using the simple bootstrap signal structure, which removes the need for the receiver to process complex information from the bootstrap. This preliminary action simplifies the receiver design while the subsequent fine estimation recovers the precision that would be lost due to the bootstrap's minimal information content.
Data Source
AI summary
A receiver detects a received signal, transmitted by a transmitter to carry payload data as Orthogonal Frequency Division Multiplexed (OFDM) symbols in divided frames, each frame including a preamble including plural bootstrap OFDM symbols. A detector circuit detects, from the bootstrap OFDM symbols, a synchronization timing for converting a useful part of the bootstrap OFDM symbols into the frequency domain. A bootstrap processor detects an estimate of the channel transfer function from a first OFDM symbol, and a demodulator circuit recovers the signaling data from the bootstrap OFDM symbols using the estimate. The bootstrap processor includes an up-sampler configured to receive the bootstrap OFDM symbols, to form an up-sampled frequency domain version of the bootstrap OFDM symbol, and an output processor configured to identify a peak correlation result, to determine frequency offset of the received signal from a relative position of the peak correlation result in the frequency domain.