SerDes Clock Modulation for Pin-Free Backchannel Communication
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Solution Overview
Problem
Serializer-deserializer (SerDes) systems lack the ability to communicate performance-related information between transmitter and receiver during operation, leading to inefficient link settings and power consumption, as existing methods require additional pins, wires, or complex modulation techniques unsuitable for optical links.
Innovation Solution
Modulating the frequency or phase of the clock signal to create a backchannel for communicating metadata without increasing pin count or affecting signal integrity, using digital modulators and phase or frequency-shift keying to encode data within the SerDes data link.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If dedicated physical backchannels are used for communication, then performance information can be communicated between TX and RX, but the number of pins and device complexity increases
Solution Approach 1:
The patent combines the data communication function and the performance information communication function into a single physical channel. The SerDes data link is used to carry both payload data and backchannel information, eliminating the need for separate physical backchannel connections. This is achieved by modulating the clock signal that drives the serializer, allowing performance information to be embedded within the existing data transmission infrastructure.
Solution Approach 2:
The existing SerDes data link is made multi-functional by enabling it to carry both primary data traffic and performance monitoring information. The clock signal used for data serialization is also used as the carrier for backchannel communication, allowing the same physical infrastructure to serve multiple purposes: data transmission, clock distribution, and performance information feedback.
2Loss of information
If common mode level modulation is used for backchannel communication, then metadata can be embedded in the data signal, but signal integrity is affected especially at very high data rates
Solution Approach 1:
The patent uses the clock signal as an intermediary carrier for backchannel information. Instead of directly modulating the data signal's common mode level, the system modulates the clock signal that drives the serializer. This indirect approach allows performance information to be transmitted without directly interfering with the data signal's integrity, as the clock modulation occurs at a different stage in the signal path.
3Loss of information
If AC coupling with frequency division multiplexing is used, then low-frequency spectrum can be used for backchannel communication, but additional pins and external capacitors are required
Solution Approach 1:
The patent extracts the backchannel communication function from the data signal path and embeds it in the clock signal path. By using the clock signal that already exists within the SerDes architecture, the invention eliminates the need for external AC coupling capacitors and additional pins required by frequency division multiplexing approaches. The clock signal serves as the carrier for backchannel information without requiring external components.
4Loss of information
If hand-shaking procedures are used at startup, then performance information can be communicated during link establishment, but real-time optimization during operation is not possible
Solution Approach 1:
The patent enables continuous backchannel communication throughout the entire operational lifetime of the SerDes link, not just during startup hand-shaking procedures. By embedding the communication capability in the ongoing data transmission process through clock signal modulation, the system can continuously exchange performance information and dynamically optimize link parameters in real-time, maintaining adaptability as long as the link is active.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables dynamic optimization of SerDes parameters and reduces power consumption by allowing real-time communication of performance information, compatible with both electrical and optical links, without adding traffic overhead or complexity.
Implementation Method 1
modulating the frequency or phase of the clock signal to create a backchannel for communicating metadata
Implementation Method 2
using digital modulators and phase or frequency-shift keying to encode data within the SerDes data link
Data Source
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AI summary
Methods, integrated circuits and computer-readable media for communicating back-channel data over a data link by modulating the phase or frequency of a clock signal of a data signal transmitted over the data link. Slow modulation of the clock signal allows it to be detected and extracted by a receiver without affecting the integrity or bit rate of the data signal. Some embodiments allow the functionality to be implemented without the use of extra hardware in the transmitter or receiver or either.