Hybrid equalizer arrangement for use in data communications equipment

• US 5,604,769 A
• Filed: 10/13/1994
• Issued: 02/18/1997
• Est. Priority Date: 10/13/1994
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Wang, Jin-Der
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US08/322,878
• Time in Patent Office: 859 Days
• Field of Search: 375/229, 375/231, 375/233, 364/724.2
• US Class Current: 375/229
• CPC Class Codes: H04L 2025/03503 as a combination of feedback and prediction filters
• CPC Class Codes: H04L 2025/03808 Transmission of equaliser coefficients
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/497 by correlative coding, e.g. partial response coding or echo modulation coding transmitters and receivers for partial response systems transversal equalizers at the transmitter end H04L25/03343
• CPC Class Codes: H04L 25/4975 Correlative coding using Tomlinson precoding, Harashima precoding, Trellis precoding or GPRS

Abstract

A hybrid type of decision feedback equalizer (DFE) structure that approaches optimal DFE performance is described. The hybrid DFE includes both an intersymbol interference DFE (ISI-DFE) and a noise predictive DFE (NP-DFE). In particular, an adaptive feedforward filter section is followed by both an intersymbol interference (ISI) predictive filter and a noise predictive (NP) filter. The corresponding transmitter uses a precoder that utilizes optimal coefficient values, denoted as C(z), of the hybrid DFE structure. In particular, C(z) is equal to (1+I(z)) (1+N(z))-1, where, the notation I(z) and N(z), as known in the art, represent the resulting coefficient values after adaptation of the ISI-DFE and the NP-DFE, respectively.

Claims

1. Apparatus for use in data communications equipment, the apparatus comprising:

precoding means responsive to a data signal for providing a sequence of precoded data symbols; and

means for transmitting the sequence of precoded data symbols to a receiver;

wherein the means for precoding further includes a feedback filter means for filtering the sequence of precoded data symbols, where the response function of the feedback filter means is equal to (1+I(z)) (1+N(z))-1, where I(z) is equal to a set of intersymbol interference decision feedback equalizer coefficients transmitted from the receiver and N(z) is equal to a set of noise predictive decision feedback equalizer coefficients transmitted from the receiver.

2. Apparatus for use in data communications equipment, the apparatus comprising:

a filter means responsive to a sequence of precoded data symbols for providing a feedback signal; and

a mapper responsive to a signal representative of a difference between a data signal and the feedback signal for providing the sequence of precoded data symbols for transmission to a receiver;

wherein the filter means has a response function equal to (1+I(z)) (1+N(z))-1, where I(z) is equal to a set of intersymbol interference decision feedback equalizer coefficients transmitted from the receiver and N(z) is equal to a set of noise predictive decision feedback equalizer coefficients transmitted from the receiver.

3. A method for use in data communications equipment, the method comprising the steps of:

precoding a data signal to provide a sequence of precoded data symbols; and

transmitting the sequence of precoded data symbols to a receiver;

wherein the precoding further includes a step of filtering the sequence of precoded data symbols in accordance with a filter response function equal to (1+I(z)) (1+N(z))-1, where I(z) is equal to a set of intersymbol interference decision feedback equalizer coefficients transmitted from the receiver and N(z) is equal to a set of noise predictive decision feedback equalizer coefficients transmitted from the receiver.

4. A method for use in data communications equipment, the method comprising the steps of:

receiving a set of intersymbol interference decision feedback equalizer coefficients, I(z), from a receiver;

receiving a set of noise predictive decision feedback equalizer coefficients, N(z), transmitted from the receiver;

precoding a data signal to provide a precoded data signal for transmission to the receiver, where the precoded data signal is a function of (1+I(z)) (1+N(z))-1.

5. A method for use in data communications equipment, the method comprising the steps of:

receiving a set of intersymbol interference decision feedback equalizer coefficients, I(z), from a receiver;

receiving a set of noise predictive decision feedback equalizer coefficients, N(z), transmitted from the receiver;

filtering a sequence of precoded data symbols to provide a feedback signal; and

mapping a signal representative of a difference between a data signal and the feedback signal to provide the sequence of precoded data symbols; and

transmitting the sequence of precoded data symbols to the receiver;

wherein the filtering step filters the sequence of precoded data symbols in accordance with a filter response function equal to (1+I(z)) (1+N(z))-1.