Timing Recovery Circuit Modulo Error Reduction
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Solution Overview
Problem
In communication systems using Tomlinson-Harashima precoding (THP), timing recovery is impaired by significant symbol errors due to noise interference, leading to synchronization issues between transmitting and receiving terminals, especially when symbol values are shifted by ±2*(M-1), causing aliasing and errors.
Innovation Solution
A timing recovery circuit comprising a modulo processing circuit, a slicer, and a de-modulo processing circuit is employed, where the modulo processing circuit performs a modulo operation on input signals, and the de-modulo processing circuit performs an inverse operation to generate an error signal for timing recovery, effectively addressing the symbol value shifts and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If THP is utilized for timing recovery at the transmitting terminal, then symbol errors are reduced in advance, but significant symbol errors occur at the receiving terminal due to noise interference and signal value shifts
Solution Approach 1:
The patent introduces a de-modulo processing circuit as an intermediary component between the slicer and the timing recovery circuit. This de-modulo circuit performs a de-modulo operation on the sliced signal to generate a corrected signal, which then serves as the input for timing recovery. By adding this intermediary component, the system can compensate for the symbol value shifts and noise effects that occur in THP-based systems, thereby improving timing recovery accuracy without sacrificing symbol value precision.
Solution Approach 2:
The patent changes the parameter of the signal processing sequence by introducing a de-modulo operation before timing recovery. Instead of directly performing timing recovery on the sliced signal (which suffers from symbol value shifts), the system first applies a de-modulo operation to restore the signal values to their expected range. This parameter change in the processing sequence allows the timing recovery circuit to operate with more accurate signal values, resolving the contradiction between reliability and measurement precision.
2Reliability
If modulo processing circuit with modulo value 2M is applied at the transmitting terminal, then symbol values are restricted to reduce symbol errors, but another modulo processing circuit with modulo value 2M is required at the receiving terminal, increasing system complexity
Solution Approach 1:
The patent applies the inversion principle by using a de-modulo operation (the inverse of modulo) at the receiving terminal instead of another modulo operation. The de-modulo processing circuit performs a de-modulo operation with the same modulo value 2M, which is the inverse function of the modulo operation applied at the transmitting terminal. This inversion allows the system to maintain symbol value restrictions and reduce symbol errors while avoiding the need for additional complex modulo processing circuits, thereby resolving the contradiction between reliability and device complexity.
3Measurement precision
If signals with symbol value ±2·(M−1) are directly eliminated in the modulo processing circuit, then symbol errors are reduced, but aliasing of larger degrees occurs
Solution Approach 1:
The patent converts the harmful effect of symbol value shifts and potential aliasing into a beneficial process by introducing the de-modulo operation. The de-modulo processing circuit takes the sliced signal (which may contain shifted values) and performs a de-modulo operation to restore the original symbol values. This process transforms the potentially harmful signal value shifts into correctable deviations, allowing the system to maintain high measurement precision while preventing aliasing through proper signal value restoration before timing recovery.
Data Source
AI summary
In the implementation of timing recovery in conventional communication systems, significant errors are generated from modulo operations under certain extreme conditions by taking input signals of a slicer as datum points. In order to prevent such errors, the input signal of a modulo processing circuit is taken as the datum point in place of the input signal of a slicer. This technique could also be applied to communication systems adopting the minimum mean-square error algorithm, the zero-forcing algorithm, or other relevant algorithms.