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Method for Inband Uplink Signaling for the Purpose of Adaptive Channel Equalization in Multi GBit Wired Links

IP.com Disclosure Number: IPCOM000015452D
Original Publication Date: 2002-Jan-11
Included in the Prior Art Database: 2003-Jun-20
Document File: 1 page(s) / 30K

Publishing Venue

IBM

Abstract

For data rates above 1-2 GBit/s, the printed wires of a PCB back plane are introducing large amounts of unwanted ISI (intersymbol interference) in the data transmission system. This is especially true for NRZ (non return to zero) transmission. The proposal describes a method to feed information back from the receiver of a high speed link to the transmitter. This function is useful for the implementation of a channel equalization system where the adaption to the channel is done in the transmitter instead of the receiver. Basic goal of the adaptive equalization of the channel is to make sure that the data samplers in the receiver of the high speed links have a just good enough signal quality to make the correct decisions. This scheme allows longer transmission distances and may also considerably reduce the power consumption because there is surplus power generated and transmitted. The uplink information density is very small compared to the down link data rate because the channel in wired links is quasi static and its equalization algorithm may run very slow. Factors of one thousand to more than a million from data rate to equalization rate are easily possible. The proposal relies on a spread spectrum modulation of the uplink information. This spread sprectrum signal has a very low energy per donlink bit time due to a large spreading factor and may therefore simply be added to the incoming data signal at the receiver side of the link without a noticable degradation of the signal to noise ratio. At the transmitter side, the spread spectum signal may be detected with low effort due to the large coding gain that may be expected. A simple direct sequence spread spectrum system will suffice, resulting in low additional complexity at low power consumption. 1

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  Method for Inband Uplink Signaling for the Purpose of Adaptive Channel Equalization in Multi GBit Wired Links

    For data rates above 1-2 GBit/s, the printed wires of a PCB
back plane are introducing large amounts of unwanted ISI
(intersymbol interference) in the data transmission system. This
is especially true for NRZ (non return to zero) transmission. The
proposal describes a method to feed information back from the
receiver of a high speed link to the transmitter. This function
is useful for the implementation of a channel equalization system
where the adaption to the channel is done in the transmitter
instead of the receiver. Basic goal of the adaptive equalization
of the channel is to make sure that the data samplers in the
receiver of the high speed links have a just good enough signal
quality to make the correct decisions. This scheme allows longer
transmission distances and may also considerably reduce the power
consumption because there is surplus power generated and
transmitted.

The uplink information density is very small compared to the down
link data rate because the channel in wired links is quasi static
and its equalization algorithm may run very slow. Factors of one
thousand to more than a million from data rate to equalization
rate are easily possible. The proposal relies on a spread
spectrum modulation of the uplink information. This spread
sprectrum signal has a very low energy per donlink bit time due
to a large spreading factor and may therefore simply be added to
t...