8-VSB Receiver Equalizer-Decoding for ISI-Robust Trellis Recovery
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Solution Overview
Problem
Digital broadcasting systems face limitations in reliability due to Inter-Symbol Interference (ISI) in channels, particularly in ATSC 8-VSB schemes, where existing channel equalization techniques like MLSE and DFE are complex or have performance limitations, necessitating the development of low-cost, high-performance receivers.
Innovation Solution
A digital television receiver with a multi-stage equalizer/decoder structure that performs adaptive channel equalization, Trellis-Coded Modulation (TCM) decoding, and Reed-Solomon (RS) decoding, using a decision feedback equalizer and providing priori information from RS decoding for soft-decision operations to enhance reliability in multipath and time-variable channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If joint MLSE (Super Trellis) is used to decode TCM data through ISI channel, then decoding performance is optimal, but hardware complexity exponentially increases with time variable channel characteristics
Solution Approach 1:
The receiver is divided into two separate functional units: a Decision Feedback Equalizer (DFE) for ISI compensation and a TCM decoder for data decoding. This segmentation allows each unit to perform its specialized function independently, avoiding the exponential complexity of joint MLSE while maintaining effective interference cancellation and decoding performance.
2Object-affected harmful factors
If Decision Feedback Equalizer is used prior to TCM decoder, then ISI compensation is achieved, but reliability is limited due to use of uncoded symbols for feedback operation
Solution Approach 1:
The TCM decoder generates decoded data that is fed back to the DFE as reliable reference signals for ISI compensation. This feedback mechanism uses high-reliability decoded symbols rather than uncoded symbols, significantly improving the accuracy of interference cancellation while maintaining the causal structure needed for real-time processing.
3Device complexity
If TCM decoder and Decision Feedback Equalizer are connected in cascade, then hardware burden is reduced, but performance is limited compared to optimal MLSE
Solution Approach 1:
The invention creates a feedback loop where the TCM decoder's output is fed back to the DFE, transforming the simple cascade connection into an iterative refinement system. This allows the DFE to use reliable decoded symbols for ISI compensation, which in turn improves decoding accuracy, achieving performance close to optimal MLSE with reduced hardware complexity.
Data Source
AI summary
Provided is a receiver for processing VSB signal. The receiver includes a first equalizer/decoder unit and a second equalizer/decoder unit. The first equalizer/decoder unit performs a first equalizing operation, first TCM decoding and first RS decoding on a received symbol to output a first dibit. The second equalizer/decoder unit performs a second equalizing operation, second TCM decoding and second RS decoding on the received symbol to output a transport stream. The first dibit is provided as a priori information for a soft-decision operation of the second TCM decoding.