Pilot-Aided MSE-OFDM Channel Estimation With Cascaded DFT Equalization
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Solution Overview
Problem
Existing pilot-aided channel estimation methods in multi-symbol encapsulated orthogonal frequency division multiplexing (MSE-OFDM) systems face challenges due to inter-symbol interference (ISI) and complex computational requirements, making conventional channel estimation and interpolation impossible, and existing solutions are either computationally complex or inefficient.
Innovation Solution
A novel transceiver design incorporating cascaded DFT processes at the transmitter and receiver, enabling simple equalization and optimal pilot-based channel estimation with low computational complexity, allowing channel estimation and interpolation across all subcarriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex time-domain equalizers are used for MSE-OFDM to handle inter-symbol interference, then channel estimation performance is improved, but computational complexity increases significantly
Solution Approach 1:
The patent extracts and removes the cyclic prefix from the received MSE-OFDM signal before processing. By taking out the CP portion that causes inter-symbol interference, the system can then apply simple frequency-domain equalization without requiring complex time-domain equalizers, thus maintaining channel estimation performance while significantly reducing computational complexity
Solution Approach 2:
The patent replaces the mechanical/algorithmic complexity of time-domain equalization with a simpler frequency-domain approach. By transforming the problem from time-domain to frequency-domain processing, the system achieves effective channel equalization using basic arithmetic operations instead of complex iterative algorithms
2Measurement precision
If maximum likelihood estimator is used for channel estimation in MSE-OFDM, then estimation accuracy is improved, but computational complexity becomes extremely high
Solution Approach 1:
The patent employs a least-squares estimator instead of the maximum likelihood estimator, using a computationally inexpensive approach that provides sufficient channel estimation accuracy for practical applications. This substitution of a simpler, lower-cost estimation method achieves acceptable performance without the extremely high computational burden of ML estimation
3Reliability
If conventional OFDM channel estimation with fixed pilots is used, then channel tracking is improved, but it becomes impossible in MSE-OFDM due to inter-symbol interference and frame structure
Solution Approach 1:
The patent inverts the conventional channel estimation approach by first removing the cyclic prefix to eliminate inter-symbol interference, then performing channel estimation on the cleaned signal. This reversed sequence of operations makes channel tracking feasible in MSE-OFDM systems where conventional approaches fail due to the frame structure and ISI
4Reliability
If cyclic prefix is added for each OFDM symbol to protect against delay spread, then robustness against multipath is improved, but CP overhead and redundancy increase
Solution Approach 1:
The patent merges multiple OFDM symbols into a single frame structure with one cyclic prefix protecting the entire frame rather than each individual symbol. This consolidation approach maintains robustness against delay spread and multipath effects while significantly reducing the cyclic prefix overhead compared to conventional per-symbol CP insertion
Data Source
AI summary
Disclosed is a method pilot-aided channel estimation in Orthogonal Frequency Division Multiplexing (OFDM) systems regardless of the frequency selectivity severity of the channel is proposed.