Pulse or digital communications – Receivers – Interference or noise reduction
Reexamination Certificate
1999-10-13
2003-04-22
Corrielus, Jean (Department: 2631)
Pulse or digital communications
Receivers
Interference or noise reduction
C375S233000
Reexamination Certificate
active
06553085
ABSTRACT:
I. INTRODUCTION
A. Related Art
This invention is related to maximizing the transmission of data over communication networks. More specifically, this invention is related to suppression of cross-talk and interference over communications channels.
B. Background
Interference (echo and crosstalk) is one of the major performance-limiting impairments on UTP cables. In this application, various receiver structures suitable to the transmission of Gigabit Ethernet over 4 pairs of UTP cables are described. Furthermore, the performance of the invention is disclosed through use of a receiver structure that uses a cascade of FSLE and DFE for interference suppression. Some of these results are based on the assumption that the interference can be cyclostationary, i.e., interference statistics are periodic with a period equal to a symbol interval. This is true as long as all transmitter symbol timing clocks are synchronized in frequency. These assumptions are meant to explain the results provided and should not be interpreted as a limitation on the scope of the claims.
Suppression of cyclostationary interference by linear equalizers has been considered previously. Prior studies have identified that linear processing of cyclostationary interfering signals can exploit spectral correlation properties peculiar to these signals. In Section II, we describe the channel characteristics and model the communication channels. In Section III, we present embodiments of the invention including the different receiver structures suitable to the transmission of Gigabit Ethernet over 4 pairs of cat-5 UTP cables. In Section IV, we present the analytical model for the cascaded FSLE/DFE receiver structure using interference suppression approach and its performance analysis. Numerical results on the SNR and numbers of taps required for the FSLE and DFE are discussed in Section V.
SUMMARY OF THE INVENTION
The present invention provides a method for equalizing interference over a synchronized packet or frame based baseband transmission system wherein the crosstalk on the system is cyclostationary or periodic with a period equal to a symbol interval. With reference to
FIG. 11
, the method comprises the steps of synchronizing
1102
the transmitters and receivers using the uncorrelated transmit signals; generating the cyclostationary NEXT and FEXT interference
1104
along with ISI using the uncorrelated symbols at the synchronized transmitters at one or more remote stations and the central station; using cascaded Fractionally Spaced Linear Equalizer (FSLE) and Decision Feed back Equalizer (DFE) for both interference suppression and equalization
1106
to minimize excess bandwidth at central receivers at the central station; increasing
1108
the receiver's FSLE filter taps (NT) to maximize Signal to noise ratio; increasing
1110
the receiver's DFE filter taps to reduce post-inter-symbol interference; and combining
1112
FSLE/DFE and proper phase sampling adjustments, enabling use of the spectral correlation properties peculiar to the modified signals.
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Corrielus Jean
Fenwick & West LLP
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