Wireless Receiver Equalization Using Hybrid Time-Frequency Coefficients
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Solution Overview
Problem
Conventional channel equalizers in wireless communication receivers, particularly for HSDPA systems, face limitations in performance and computational complexity, especially when dealing with specific channel conditions and the need for additional cost in implementing decision-feedback equalizers, and rely on assumptions about noise and interference statistics.
Innovation Solution
A hybrid time-domain/frequency-domain equalizer design where coefficients are calculated in the frequency domain and transformed to the time domain for use in a time-domain filter, with spectral regularization to constrain the time span of the equalizer tap-weights vector, reducing computational complexity and performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional frequency-domain equalization is used, then equalization performance is improved, but computational complexity increases and overlap techniques are required
Solution Approach 1:
The patent segments the equalization process into two distinct domains: frequency-domain coefficient calculation and time-domain signal filtering. By separating these functions, the patent avoids the computational burden of full frequency-domain processing while retaining the benefits of frequency-domain coefficient optimization. This segmentation eliminates the need for overlap techniques and reduces overall computational complexity.
Solution Approach 2:
The patent introduces an intermediary transformation step where frequency-domain equalizer coefficients are converted to time-domain coefficients before applying the equalization filter. This intermediary transformation allows the system to leverage the computational efficiency of frequency-domain coefficient calculation while performing the actual filtering in the computationally simpler time domain, thereby reducing overall computational complexity without sacrificing equalization performance.
2Measurement precision
If the number of equalizer coefficients is increased, then equalization accuracy is improved, but computational complexity and processing time increase
Solution Approach 1:
The patent transitions the filtering operation from the frequency domain to the time domain, changing the dimensional perspective of the equalization process. This dimensional change allows the system to use a smaller number of time-domain coefficients to achieve the same equalization accuracy that would require many more frequency-domain coefficients, thereby improving processing speed while maintaining equalization accuracy.
3Reliability
If decision-feedback equalization is used, then equalization performance is improved, but implementation cost and complexity increase significantly
Solution Approach 1:
The patent employs a linear equalizer structure that is computationally cheaper and simpler to implement than decision-feedback equalization. While linear equalizers may theoretically require more coefficients to achieve the same performance, the patent compensates by using frequency-domain coefficient calculation to optimize these coefficients efficiently, thereby achieving good equalization performance at lower implementation cost and complexity.
Data Source
AI summary
A method, receiver and program for equalizing digital samples of a radio signal received over a wireless communications channel. The method comprises: receiving digital samples of the radio signal; calculating equalizer coefficients in the frequency domain; transforming the equalizer coefficients from the frequency domain to the time domain; and equalizing the digital samples in the time domain using the transformed time domain equalizer coefficients.