Backplane Ethernet Pre-Coding for High-Speed ISI Mitigation
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Solution Overview
Problem
High-speed communication systems, such as Backplane Ethernet, face significant signal impairment due to intersymbol interference (ISI) and noise at conventional 10 Gbps speeds, making it challenging to achieve speeds beyond this limit without compromising reliability.
Innovation Solution
A system that employs a transmitter architecture using higher-order modulation schemes like PAM-4, combined with forward error correction (FEC) and a pre-coder architecture to mitigate ISI and noise, along with a receiver design that includes a feedforward equalizer and inverse pre-coder to recover data accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher transmission speeds are used to increase productivity, then data transmission speed is improved, but signal reliability deteriorates due to ISI and noise
Solution Approach 1:
The pre-coder modifies the transmitted signal in advance to counteract the expected ISI effects before the signal propagates through the channel. By pre-distorting the signal with knowledge of the channel characteristics, the system prepares the signal to arrive at the receiver with reduced ISI, enabling higher speeds while maintaining reliability
Solution Approach 2:
The system uses feedback equalization where the receiver estimates the channel response and feeds back correction information to the transmitter. The pre-coder adapts its pre-distortion based on feedback about actual channel conditions, allowing the system to optimize performance at high speeds while compensating for ISI and noise
2Ease of manufacture
If conventional transceiver designs are used to maintain ease of manufacture, then device complexity is reduced, but the ability to transmit at speeds beyond 10 Gbps is lost
Solution Approach 1:
The transceiver is divided into distinct functional blocks: a pre-coder stage that processes data before modulation, a conventional modulator, and a separate equalization stage at the receiver. This segmentation allows the use of proven conventional designs for most components while adding only the necessary pre-coding functionality to achieve higher speeds
Solution Approach 2:
The system changes the signal parameters by applying pre-coding transformation to the data stream before conventional modulation. This parameter transformation enables the signal to withstand higher transmission rates by pre-compensating for distortion, allowing conventional transceiver architectures to operate at speeds beyond 10 Gbps
Data Source
AI summary
In conventional Backplane Ethernet systems, data is transmitted over two pairs of copper traces in one direction using a PAM-2 scheme and a baud rate of 10.3125 GHz, giving an effective bit rate of 10.3125 Gbps. The rate at which data can be transmitted in Backplane Ethernet systems, while still being reliably received, is typically limited by ISI caused by the dispersive nature of the copper traces, frequency dependent transmission losses caused primarily by skin effect and dielectric loss of the copper traces, and cross-talk from adjacent communication lines. The present invention is directed to systems for overcoming these and other signal impairments to achieve speeds up to, and beyond, twice the conventional 10 Gbps limit associated with Backplane Ethernet systems.