Iterative CX-BEM Channel Estimation for Time-Varying Wireless Signals
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Solution Overview
Problem
In wireless communication over time-varying channels, high Doppler spread and multipath propagation distort signals, making efficient and accurate channel estimation and symbol detection challenging due to the channel's frequency selectivity.
Innovation Solution
A method involving hybrid channel estimation and equalization, including initial channel estimation based on complex-exponential basis expansion model (CX-BEM) coefficients, followed by iterative rounds of channel estimation, interference removal, and equalization to improve signal detection accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional channel estimation and equalization techniques are used over time-varying channels, then the system can operate in mobile radio communication and satellite communication, but the signal distortion due to high Doppler spread and multipath propagation results in poor channel estimation accuracy and high bit error rates
Solution Approach 1:
The patent segments the channel estimation process into multiple stages: initial channel estimation using pilot symbols, followed by iterative refined estimation using detected data symbols. This multi-stage segmentation allows progressive improvement of estimation accuracy by separating the estimation tasks into manageable components that can be executed sequentially with increasing precision.
Solution Approach 2:
The patent implements feedback mechanisms where detected source symbols from equalization are fed back into the channel estimation process. The detected symbols are used to refine channel estimates in subsequent iterations, creating a closed-loop system where estimation and detection continuously improve each other through feedback, thereby overcoming signal distortion effects.
2Reliability
If iterative channel estimation and equalization are performed to improve signal detection accuracy, then bit error rates decrease, but computational complexity and processing time increase
Solution Approach 1:
The patent performs preliminary channel estimation using pilot symbols before actual data detection. This preliminary action provides an initial channel estimate that enables subsequent equalization operations, avoiding the need to perform complex iterative estimation from scratch and reducing overall computational burden while maintaining detection accuracy.
Solution Approach 2:
The patent employs partial action by performing a limited number of iterative refinement rounds rather than exhaustive optimization. The iterative process is stopped after a predetermined number of iterations or when convergence criteria are met, providing sufficient improvement in detection accuracy without incurring excessive computational costs associated with unlimited iterations.
3Adaptability or versatility
If complex-exponential basis expansion model (CX-BEM) is used for channel modeling, then time-varying channel characteristics are accurately captured, but the number of parameters to be estimated increases
Solution Approach 1:
The patent segments the parameter estimation task by separating pilot-aided estimation from data-aided estimation. Different parameter sets are estimated at different stages, allowing the system to handle the large number of CX-BEM parameters through divided estimation tasks rather than attempting to estimate all parameters simultaneously, thus managing complexity while maintaining modeling accuracy.
Data Source
AI summary
There is provided a method of receiving a transmitted signal over a time-varying channel. The method includes: obtaining a received symbol signal in frequency domain based on the transmitted signal; performing a first channel estimation based on the received symbol signal to obtain a plurality of first estimated BEM coefficients; performing a first equalization based on the received symbol signal and the plurality of first estimated BEM coefficients to obtain a plurality of first detected source symbols; and performing one or more rounds of a second channel estimation and a second equalization. Each round includes: performing the second channel estimation based on the received symbol signal and a plurality of detected source symbols to obtain a plurality of second estimated BEM coefficients; performing interference removal based on the received symbol signal, the plurality of detected source symbols and the plurality of second estimated BEM coefficients to obtain an interference reduced symbol signal infrequency domain; and performing the second equalization based on the interference reduced symbol signal and the plurality of second estimated BEM coefficients to obtain a plurality of second detected source symbols. There is also provided a corresponding receiver, and a system for wireless communication over a time-varying channel including the receiver.