Frequency-Domain Turbo Equalization for Multipath VSB Reception
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Solution Overview
Problem
Digital communication systems face challenges in accurately receiving digital television (DTV) signals due to signal distortion and noise from the propagation medium, which can lead to bit error rates exceeding the system's error tolerance, especially when the communication channel characteristics are unknown or change over time.
Innovation Solution
A digital communications receiver processes received signals by applying cyclic prefix restoration, converting them to the frequency domain, and using a frequency domain turbo equalizer to estimate channel characteristics, reducing the number of symbol values needed to determine the full set of received symbols, thereby mitigating multipath effects and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive equalization is used to compensate for channel distortion, then signal quality is improved, but device complexity increases significantly
Solution Approach 1:
The patent extracts and processes only the necessary portion of the received signal by utilizing the cyclic prefix structure. Instead of processing the entire signal through complex adaptive equalization, the method extracts the useful signal portion from the cyclic prefix and processes it separately, thereby reducing the computational complexity and device requirements while maintaining signal quality.
Solution Approach 2:
The patent transforms the time-domain signal processing problem into the frequency domain using FFT operations. By converting the received signal and channel impulse response to frequency domain representations, the equalization process becomes computationally simpler and can be implemented with reduced device complexity while achieving the same signal quality improvement.
2Measurement precision
If the entire received signal is processed to recover all symbols, then measurement precision is improved, but loss of time increases due to processing duration
Solution Approach 1:
The patent extracts and processes only the necessary portion of the received signal by utilizing the cyclic prefix structure. Instead of processing the entire signal to recover all symbols, the method extracts the useful signal portion from the cyclic prefix and processes it separately, thereby reducing processing time while maintaining sufficient symbol recovery accuracy for system operation.
3Reliability
If conventional equalization is used, then signal distortion is compensated, but inter-symbol interference persists due to multipath delays
Solution Approach 1:
The patent applies preliminary processing to the cyclic prefix portion of the signal before main signal processing. By pre-processing the cyclic prefix to extract channel impulse response information and compensate for multipath effects in advance, the method reduces inter-symbol interference in the main signal processing stage, thereby improving overall system performance.
Data Source
AI summary
In a digital communications receiver configured to receive, via a communications channel, a received first signal representing a sequence of symbols, each symbol being encoded to be representative of data bits, a method of processing the received signal includes adjusting a magnitude, filtering, and applying cyclic prefix restoration, to the received signal to produce a second signal, converting the second signal from time domain to frequency domain to produce a frequency domain signal, and determining a first quantity of values representing a first portion of the symbols by evaluating a relationship of channel values representing characteristics of the communications channel and a second quantity of values representing a portion of the frequency domain signal, the first quantity being smaller than the second quantity.