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Adaptive pre-emphasis adjustment based on self-contained bit errors in high speed network design.

IP.com Disclosure Number: IPCOM000031533D
Original Publication Date: 2004-Sep-28
Included in the Prior Art Database: 2004-Sep-28
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Abstract

Adaptive pre-emphasis adjustment based on self-contained bit errors in high speed network design.

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THIS COPY WAS MADE FROM AN INTERNAL IBM DOCUMENT AND NOT FROM THE PUBLISHED BOOK

TUC820030027 Jean Barkley/Tucson/IBM Kenny N Qiu, Gregg Lucas, Matthew D Bomhoff, Andrew E Seidel, Brian Cagno

Adaptive pre-emphasis adjustment based on self -contained bit errors in high speed network design.

1. Background: What is the problem solved by your invention? Describe known solutions to this problem (if any). What are the drawbacks of such know solutions, or why is an additional solution required? Cite any relevant technical documents or references.

One of the obstacles in high speed serial interface design such as Fibre Channel (FC) is dealing with signal degradation in signal transmission. Unexpected or unknown signal losses can ultimately cause operational failures. Such negative electrical signal effects can be caused by many factors, including long cable lengths, low quality cables, aging and environmental conditions such as temperature and mechanical stress. This reduction in signal amplitude is often referred to as "Eye Opening Closure". Figure 1 is an example of an eye diagram. The smaller the signal amplitude, the smaller the eye opening is, thereby, reducing the ability to transmit data without failures. This results in a higher bit error rate.

Figure 1. Eye Opening

In high speed network designs, pre-emphasis is a common technique used to increase the amplitude at the source of the signal to help improve signal quality at the destination. Pre-emphasis is usually predetermined for a specific environment at the design stage, which assumes the high speed transmission lines parameters will never change. This limits the flexibility to adapt the changes of parameters such as cable length and noise. The inability to adapt the changes of operation parameters such as changes of cable length can cause the increase of bit error rate. Bit error rate is the percentage of bits that have errors relative to the total number of bits received in a transmission and is an indication of how often a "packet" has to be retransmitted. This invention uses the self-contained bit error rate as a measurement to detect the changes in parameters to tune the electrical characteristics of the transmitter in order to achieve an optimal pre-emphasis value; therefore, the lowest possible bit error rate is achieved.

2. Summary of Invention: Briefly describe the core idea of your invention (saving the details for questions #3 below). Describe the advantages(s) of using your invention instead

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of the known solutions described above.

With the capability of dynamically adjusting pre-...