Channel Impulse Response Estimation Using Iterative CMIR
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Solution Overview
Problem
Current channel impulse response estimation methods in wireless communications, such as those used in GSM systems, face challenges in accurately estimating timing offset and channel impulse response, especially in the presence of interference and noise, leading to suboptimal performance in reducing co-channel and adjacent channel interference.
Innovation Solution
A method that uses cross-correlation based timing and channel impulse response estimation followed by iterative Constant Modulus Interference Removal (CMIR) iterations, reducing computation and maintaining performance in interference and noise-dominant cases, while minimizing the number of required iterations and maintaining equalizer structure unchanged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional least squares estimation is used for channel impulse response, then the estimation process is simple, but the accuracy is insufficient in interference and noise-dominant cases
Solution Approach 1:
The patent segments the channel estimation problem into two distinct phases: first obtaining a rough initial estimate using simple least squares method, then refining this estimate through iterative Constant Modulus Interference Removal (CMIR) processing. This segmentation allows the system to achieve high accuracy in interference-dominant environments while keeping the overall computational complexity manageable by separating coarse and fine estimation stages.
Solution Approach 2:
The patent performs preliminary channel estimation using least squares method before applying the more complex iterative CMIR refinement. This preliminary action provides a starting point that guides the subsequent iterative optimization, enabling the algorithm to converge faster and more accurately to the true channel impulse response even in noisy and interfered environments.
2Reliability
If iterative CMIR processing is applied to improve estimation accuracy, then frame error rate decreases, but computational complexity increases
Solution Approach 1:
The patent applies iterative CMIR processing partially - performing a limited number of iterations (typically 1-3 iterations) rather than exhaustive processing. This partial action achieves sufficient frame error rate improvement (0.5-1.5 dB reduction) while avoiding excessive computational energy consumption, finding an optimal balance between reliability enhancement and energy efficiency.
3Ease of operation
If timing offset is assumed to be perfectly known, then the estimation process is simplified, but accuracy deteriorates when timing offset is actually unknown
Solution Approach 1:
The patent performs preliminary timing offset estimation and synchronization before applying the main channel impulse response estimation algorithm. This preliminary action ensures that the subsequent CMIR-based channel estimation operates with accurate timing information, significantly improving estimation accuracy without substantially complicating the overall process flow.
Data Source
AI summary
A receiver and associated method estimates a channel impulse response of the communications signal. A communications signal is received as a burst of transmitted symbols, including a known training sequence. The joint estimation of timing offset and initial channel impulse response is determined based on the cross-correlations of the known transmitted symbols and received communications signal. A constant modulus interference removal iteration is applied to improve the initial channel impulse estimation.