Bit-to-Symbol Encoding Mitigates Baseline Wander in PAM Signals
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Solution Overview
Problem
Baseline wander (BLW) in pulse amplitude modulated (PAM) signals transmitted through high pass filters leads to deteriorated bit error rate (BER) performance due to DC shifts, and existing solutions either increase receiver costs or are ineffective as feed forward approaches.
Innovation Solution
A bit-to-symbol encoding technique that involves generating side scrambling values using polynomials, scrambling data, and mapping it to a set of symbols with sufficient positive and negative voltage transitions to mitigate BLW, reducing the need for baseline wander compensation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a baseline wander compensating unit is used at the receiver to compensate for DC level changes, then BER performance is improved, but receiver cost and complexity increase
Solution Approach 1:
The patent applies preliminary action by implementing baseline wander compensation at the transmitter side before signal transmission. The transmitter generates compensation signals based on estimated DC level changes and adds them to the original signal in advance, so that the received signal already has compensated DC levels, eliminating the need for complex receiver-side compensation circuits.
Solution Approach 2:
The patent uses an intermediary approach by introducing a compensation signal as a mediator between the original signal and the transmitted signal. This compensation signal, generated based on polynomial fitting of DC level changes, acts as an intermediate element that pre-adjusts the DC level before transmission, thereby simplifying the receiver structure.
2Device complexity
If feed forward baseline wander compensation is used at the transmitter, then receiver complexity is reduced, but compensation effectiveness decreases
Solution Approach 1:
The patent implements feedback by using received signal samples at the transmitter to estimate DC level changes. The transmitter continuously monitors the transmitted signal characteristics, fits polynomial models to track DC drift, and uses this feedback information to generate real-time compensation signals, thereby maintaining high compensation effectiveness in a feed-forward architecture.
Solution Approach 2:
The patent replaces the mechanical/receiver-side compensation system with a signal-processing-based transmitter-side compensation system. Instead of using complex receiver circuits to physically adjust DC levels, the invention uses polynomial fitting algorithms and digital signal processing to generate compensation signals, substituting hardware complexity with computational methods.
3Reliability
If conventional bit-to-symbol mapping is used to provide voltage transitions, then some BLW mitigation is achieved, but BER performance can be further improved
Solution Approach 1:
The patent applies parameter changes by modifying the bit-to-symbol mapping process to incorporate DC level compensation information. The mapping technique adjusts symbol selection based on estimated DC drift parameters, dynamically changing the mapping parameters to ensure sufficient voltage transitions that counteract baseline wander, thereby improving BER performance without significant complexity increase.
Data Source
AI summary
A device and method for encoding bits to symbols for a communication system are described. In one embodiment, a method for encoding bits to symbols for a communication system includes receiving a set of N-bit data to be transmitted, where N is an integer, generating side scrambling values using a polynomial, scrambling the set of N-bit data using the side scrambling values to produce scrambled data, mapping the scrambled data to a particular set of M symbols from a plurality of sets of M symbols, where M is an integer and M is smaller than N, and outputting the particular set of M symbols for transmission over a transmission medium. Other embodiments are also described.