US 6968001

US Patent 6968001: Communication Receiver with Virtual Parallel Equalizers

Title: Communication receiver with virtual parallel equalizers

Current Assignee: Qualcomm Inc.

Inventors:

• Srikant Jayaraman
• Ivan Jesus Fernandez Corbaton
• John E. Smee
• Michael A. Howard

Filing Date: August 21, 2002

Issue Date: November 22, 2005

Abstract:
The patent describes a method for optimizing an equalizer in a communication system receiver by utilizing "virtual parallel equalizers." This involves applying multiple configurations for training a single equalizer and then determining a performance measurement or estimate for each configuration. By comparing these performance measures, the optimum configuration is identified. The training and selection process is designed to operate at a rate significantly higher than the received sample rate, allowing for optimization to occur between the processing of data samples.

Plain-Language Overview of Independent Claims:

Independent Claim 1: Method of estimating a transmitted signal
This claim outlines a method for improving signal reception using an equalizer. It involves a repetitive process of:

1. Establishing a first setup: Defining a first set of operational values (parameters) for the equalizer.
2. Learning and updating: Training the equalizer based on these values to refine them.
3. Assessing performance: Measuring how well the equalizer performs with the updated first set of values.
4. Establishing a second setup: Defining a second, different set of operational values for the equalizer, which effectively changes its configuration.
5. Learning and updating again: Training the equalizer with these second values to refine them.
6. Assessing second performance: Measuring the equalizer's performance with the updated second set of values.
7. Comparing results: Directly comparing the performance results from the first and second setups.
8. Making a choice: Selecting the better performing set of values.
9. Applying the best setup: Configuring the equalizer to operate using the chosen best set of values.

Independent Claim 11: Apparatus for estimating a transmitted signal
This claim describes a device (apparatus) that performs the method of Claim 1. It lists the "means for" carrying out each step of the method:

• Means for determining a first set of values.
• Means for training the equalizer to generate updated first values.
• Means for estimating a first performance parameter.
• Means for setting a second set of values.
• Means for training the equalizer to generate updated second values.
• Means for estimating a second performance parameter.
• Means for comparing the first and second performance parameters.
• Means for selecting one of the sets of values.
• Means for configuring the equalizer using the selected values.

Independent Claim 12: Wireless apparatus
This claim describes a wireless device that includes an equalizer designed to estimate a transmitted signal. This equalizer is specifically configured to perform the core steps of the method described in Claim 1, essentially acting as the "means" without explicitly using the "means for" language:

• Determine a first set of parameter values.
• Train itself to generate updated first values.
• Estimate a first performance parameter.
• Set a second set of parameter values, changing its configuration.
• Train itself to generate updated second values.
• Estimate a second performance parameter.
• Compare the two performance parameters.
• Select the better set of values.
• Configure itself using the selected values.

Independent Claim 13: A method comprising
This claim presents another method, similar to Claim 1, but explicitly centers the training and performance measurement around a "received pilot signal":

1. Initial configuration: Set up the equalizer with a first set of parameters.
2. Train on pilot (first): Adjust the equalizer's settings using a known pilot signal with the first parameters.
3. Measure performance (first): Determine a performance level based on the pilot signal using the first configuration.
4. Second configuration: Set up the equalizer with a second, different set of parameters.
5. Train on pilot (second): Adjust the equalizer's settings using the same received pilot signal with the second parameters.
6. Measure performance (second): Determine a performance level based on the pilot signal using the second configuration.
7. Compare performance: Contrast the first and second performance measures.
8. Select best parameters: Choose either the first or second set of parameters based on which performed better.
9. Final configuration: Configure the equalizer with the chosen (best) set of parameters.

Independent Claim 15: An apparatus comprising
This claim describes a device that contains a "configurable equalizer" and a "configuration selection unit" that together implement the method of Claim 13. The configuration selection unit is responsible for:

• Configuring the equalizer with a first set of parameters.
• Training the equalizer on a received pilot signal with the first parameters.
• Determining a first performance measure.
• Configuring the equalizer with a second set of parameters.
• Training the equalizer on the received pilot signal with the second parameters.
• Determining a second performance measure.
• Comparing the performance measures.
• Selecting the optimal set of parameters.
• Configuring the equalizer with the selected parameters.

CAFC 2026 Dockets:
As of April 26, 2026, a search of the CAFC 2026 dockets did not yield any specific cases or decisions directly mentioning US Patent 6968001. The patent's legal status is listed as "Expired - Lifetime", expiring on December 29, 2022, according to the provided patent text.

I do not have any information about litigation specifically involving US patent 6968001. My search did not return any relevant results from the specified patent litigation search sites.

Proceedings overview

There are no AIA trial proceedings on file for US patent 6968001.

Strategic summary

As there are no AIA trial proceedings on file for US patent 6968001, all claims (1-15) of the patent remain untested by these particular post-grant review mechanisms. This means there is no estoppel landscape established by IPR, PGR, or CBM proceedings that would bar future petitioners from raising prior-art grounds. The absence of PTAB activity could indicate that the patent has not been extensively asserted, or that prior challenges have taken other forms (e.g., district court litigation).

Recommended next steps

No PTAB activity exists for US patent 6968001. Therefore, if facing assertion of this patent, all claims of the patent are presumed valid for the purposes of PTAB challenges. An absence of PTAB activity is itself a signal; well-asserted patents often eventually attract IPRs.

Inventors

• Srikant Jayaraman (Qualcomm Inc.)
• Ivan Jesus Fernandez Corbaton (Qualcomm Inc.)
• John E. Smee (Qualcomm Inc.)
• Michael A. Howard (Qualcomm Inc.)

Original assignee

The original assignee, Qualcomm Inc., is an American multinational technology corporation headquartered in San Diego, California. The company develops and designs technologies for global communications and computing, including next-generation mobile networks, smart devices, and semiconductors. Qualcomm holds essential patents for global mobile communication standards, including 5G, 4G, CDMA2000, TD-SCDMA, and WCDMA. Qualcomm makes the chips and software that connect phones, cars, and other devices to wireless networks, with its best-known products being mobile processors and modem chips used in smartphones. They also earn revenue from licensing many of the core patents behind cellular technology. Qualcomm is currently operating.

Assignment timeline

There are no recorded assignments for US Patent 6968001 on the USPTO Patent Assignment Search database beyond the initial assignment to Qualcomm Incorporated at the time of grant, as indicated in the patent document itself.

Timeline diagram

timeline
    title Ownership of US 6968001
    2002 : Filed by Qualcomm Inc
    2005 : Issued to Qualcomm Inc

NPE / troll-pattern signals

1. Shell-entity transfer — not present
2. Known asserter in the chain — not present
3. Repeat correspondent across the chain — not present
4. Cascading transfers — not present
5. Pre-litigation transfer — not present
6. Bankruptcy fire-sale — not present
7. Privateering — not present
8. Defensive aggregator (anti-NPE) — not present

Verdict

Insufficient data
There are no recorded assignments for US Patent 6968001 beyond the original assignment to Qualcomm Inc. This lack of assignment records means there is no evidence to suggest any NPE activity.

To identify the most relevant prior art for US patent 6968001, I will examine the "Citations" and "Family Cites Families" sections of the provided patent text, as these typically list the prior art considered during prosecution. The information regarding publication/filing date and a brief description is provided within the patent text itself. I will then cross-reference these against the independent claims to determine potential anticipation under 35 U.S.C. § 102.

Cited Prior Art for US Patent 6968001:

Here are the patent citations listed in US6968001, along with their relevant details and potential anticipation:

Patent Citations (Directly cited by US6968001):

1. US5268930A

   • Full Citation: US5268930A (en)
   • Publication Date: 1993-12-07
   • Priority Date: 1991-12-19
   • Assignee: Novatel Communications Ltd.
   • Title: Decision feedback equalizer
   • Brief Description: This patent describes a decision feedback equalizer. Decision Feedback Equalizers (DFE) are a type of equalizer that uses previously detected symbols to help cancel intersymbol interference (ISI) from currently received symbols. This is relevant to the general field of equalization addressed by US6968001.
   • Potential Anticipation (35 U.S.C. § 102): US5268930A teaches a type of equalizer. While US6968001 focuses on virtual parallel equalizers and a method for selecting an optimal configuration, this reference could potentially anticipate the broad concept of using an equalizer, particularly if the claims of US6968001 are interpreted very broadly without the "virtual parallel" or "selection" features. However, it is unlikely to anticipate the specific method of training and selecting among multiple virtual configurations.

2. US5666378A

   • Full Citation: US5666378A (en)
   • Publication Date: 1997-09-09
   • Priority Date: 1994-03-18
   • Assignee: Glenayre Electronics, Inc.
   • Title: High performance modem using pilot symbols for equalization and frame synchronization
   • Brief Description: This patent describes a high-performance modem that uses pilot symbols for equalization and frame synchronization. The use of pilot signals for training and performance measurement is explicitly mentioned in US6968001 (e.g., in independent claims 13 and 15, and in the detailed description regarding MSE/C/I estimation from pilot signals).
   • Potential Anticipation (35 U.S.C. § 102): This reference explicitly teaches the use of pilot symbols for equalization. This could potentially anticipate aspects of US6968001, particularly claims 13 and 15, which specifically mention training on a "received pilot signal" and determining a performance measure based on it. The novelty of US6968001 in this context would likely reside in the "virtual parallel" aspect and the comparison and selection of multiple configurations, rather than simply using pilot symbols for training a single equalizer.

3. US5787118A

   • Full Citation: US5787118A (en)
   • Publication Date: 1998-07-28
   • Priority Date: 1993-09-10
   • Assignee: Mitsubishi Denki Kabushiki Kaisha
   • Title: Adaptive equalizer and adaptive diversity equalizer
   • Brief Description: This patent describes an adaptive equalizer and an adaptive diversity equalizer. Adaptive equalizers are a core component of US6968001, which deals with optimizing their configuration.
   • Potential Anticipation (35 U.S.C. § 102): Similar to US5268930A, this reference broadly teaches adaptive equalizers. It could anticipate the general concept of an adaptive equalizer but is unlikely to anticipate the specific method of creating "virtual parallel" configurations and selecting an optimal one based on performance parameters, as claimed in US6968001.

4. EP0782305A2

   • Full Citation: EP0782305A2 (en)
   • Publication Date: 1997-07-02
   • Priority Date: 1995-12-27
   • Assignee: Matsushita Electric Industrial Co., Ltd.
   • Title: Bidirectional DFE
   • Brief Description: This patent describes a bidirectional DFE (Decision Feedback Equalizer).
   • Potential Anticipation (35 U.S.C. § 102): This patent's relevance is similar to US5268930A, focusing on a specific type of equalizer. It may anticipate the general use of equalizers but not the "virtual parallel" optimization method of US6968001.

5. US6016379A

   • Full Citation: US6016379A (en)
   • Publication Date: 2000-01-18
   • Priority Date: 1997-08-05
   • Assignee: Alcatel
   • Title: Method and facility for equalizing an electric signal distorted due to interference in the optical domain
   • Brief Description: This patent describes a method and facility for equalizing an electric signal distorted due to interference in the optical domain.
   • Potential Anticipation (35 U.S.C. § 102): This patent describes equalization in a different domain (optical). While it addresses signal equalization, the context and specific mechanisms are likely different enough to not directly anticipate the claims of US6968001 in a wireless communication system with virtual parallel equalizers.

6. US6735244B1

   • Full Citation: US6735244B1 (en)
   • Publication Date: 2004-05-11
   • Priority Date: 1999-08-30
   • Assignee: Fujitsu Limited
   • Title: Data transmission system and receiver unit thereof
   • Brief Description: This patent describes a data transmission system and a receiver unit thereof.
   • Potential Anticipation (35 U.S.C. § 102): This patent's description is too general to assess specific anticipation without further details on its equalization methods. If it details a receiver unit with an equalizer that selects configurations based on performance, it could be highly relevant. Given the publication date (2004) is after the filing date of US6968001 (2002), its priority date (1999) would be key for 35 U.S.C. § 102 analysis.

7. US20020196844A1

   • Full Citation: US20020196844A1 (en)
   • Publication Date: 2002-12-26
   • Priority Date: 2001-05-04
   • Assignee: Caly Networks
   • Title: Adaptive equalizer system for short burst modems and link hopping radio networks
   • Brief Description: This patent describes an adaptive equalizer system for short burst modems and link hopping radio networks.
   • Potential Anticipation (35 U.S.C. § 102): The priority date (2001-05-04) is prior to US6968001's filing date (2002-08-21). This reference teaches an "adaptive equalizer system." If it includes mechanisms for adjusting equalizer parameters based on performance or selecting between different configurations in a way that aligns with the "virtual parallel" concept of US6968001, it could be a significant piece of prior art, particularly for independent claims 1, 11, 12, 13, and 15, which cover methods and apparatus for configuring, training, estimating performance, comparing, and selecting equalizer parameters.

Family Cites Families (Cited by other patents in the same family as US6968001):

1. JPH03244220A

   • Full Citation: JPH03244220A (en)
   • Publication Date: 1991-10-31
   • Priority Date: 1990-02-22
   • Assignee: Toshiba Corp
   • Title: Automatic equalizer
   • Brief Description: This patent describes an automatic equalizer.
   • Potential Anticipation (35 U.S.C. § 102): This is a broad disclosure of an automatic equalizer. It is highly unlikely to anticipate the specific "virtual parallel" and selection methods of US6968001, which represent an advancement in optimizing such equalizers.

2. JPH04252609A

   • Full Citation: JPH04252609A (en)
   • Publication Date: 1992-09-08
   • Priority Date: 1991-01-29
   • Assignee: Canon Inc
   • Title: automatic equalizer
   • Brief Description: This patent describes an automatic equalizer.
   • Potential Anticipation (35 U.S.C. § 102): Similar to JPH03244220A, this reference broadly teaches an automatic equalizer and is unlikely to anticipate the specific features of US6968001 related to virtual parallel equalizers and selection based on performance.

3. JPH10163934A

   • Full Citation: JPH10163934A (en)
   • Publication Date: 1998-06-19
   • Priority Date: 1996-12-03
   • Assignee: Matsushita Electric Ind Co Ltd
   • Title: Receiver
   • Brief Description: This patent describes a receiver.
   • Potential Anticipation (35 U.S.C. § 102): The description is very general ("Receiver"). Without more specific details on the equalization within this receiver, it's impossible to determine its potential for anticipation.

4. JP3168576B2

   • Full Citation: JP3168576B2 (en)
   • Publication Date: 2001-05-21
   • Priority Date: 1990-07-09
   • Assignee: ソニー株式会社
   • Title: Waveform equalization filter device
   • Brief Description: This patent describes a waveform equalization filter device.
   • Potential Anticipation (35 U.S.C. § 102): This patent's priority date (1990-07-09) makes it significantly older than US6968001. It describes a "waveform equalization filter device," which is a foundational component. It likely establishes the general concept of equalization but not the specific methods of virtual parallel equalizers and selection described in US6968001.

5. US6373888B1

   • Full Citation: US6373888B1 (en)
   • Publication Date: 2002-04-16
   • Priority Date: 1998-10-09
   • Assignee: Telefonaktiebolaget Lm Ericsson (Publ)
   • Title: Estimated channel with variable number of taps
   • Brief Description: This patent describes an estimated channel with a variable number of taps. The concept of varying the number of equalizer taps to adjust performance is a central theme in US6968001, which discusses setting coefficients to zero to effectively change equalizer length.
   • Potential Anticipation (35 U.S.C. § 102): This is a highly relevant reference. Its priority date (1998-10-09) is prior to US6968001. The teaching of an "estimated channel with variable number of taps" directly addresses the problem of optimizing equalizer length, which is a core part of the "virtual parallel equalizers" concept in US6968001 (e.g., in the discussion of setting tap coefficients to zero to change effective length). Depending on the details of how the "variable number of taps" is managed and optimized in US6373888B1, it could potentially anticipate aspects of claims 1, 11, 12, 13, and 15, particularly concerning the determination of different equalizer configurations based on tap length and the selection of an optimal configuration.

6. US6522683B1

   • Full Citation: US6522683B1 (en)
   • Publication Date: 2003-02-18
   • Priority Date: 2000-08-10
   • Assignee: Qualcomm, Incorporated
   • Title: Method and apparatus for adaptive linear equalization for walsh covered modulation
   • Brief Description: This patent describes a method and apparatus for adaptive linear equalization for Walsh covered modulation.
   • Potential Anticipation (35 U.S.C. § 102): This patent, also by Qualcomm, has a priority date (2000-08-10) prior to US6968001. It describes an "adaptive linear equalization" method. While it mentions equalization, the specific focus on "Walsh covered modulation" might differentiate it. However, if it teaches adapting or optimizing equalizer parameters by comparing different configurations or performance metrics, it could be relevant to the general inventive concept of US6968001, specifically related to claims 1, 11, 12, 13, and 15 regarding adaptive equalization and optimization.

Most Relevant Prior Art Summary:

Based on the titles and brief descriptions, US6373888B1 ("Estimated channel with variable number of taps") and US20020196844A1 ("Adaptive equalizer system for short burst modems and link hopping radio networks") appear to be the most relevant prior art.

• US6373888B1 directly addresses the concept of a variable number of taps in an estimated channel, which is a key element of how US6968001 implements "virtual" equalizers by effectively changing their length. The details of its optimization method would be critical in assessing its anticipatory effect on US6968001's claims, particularly those relating to selecting an optimal configuration.

• US20020196844A1 (with its 2001 priority date) is highly relevant as it describes an "adaptive equalizer system." The specifics of how this system adapts and whether it involves comparing different configurations or performance metrics for selection would determine its direct impact on claims 1, 11, 12, 13, and 15, which cover methods and apparatus for configuring, training, estimating performance, comparing, and selecting equalizer parameters.

US5666378A ("High performance modem using pilot symbols for equalization and frame synchronization") is also highly relevant, particularly to claims 13 and 15, due to its explicit teaching of using pilot symbols for equalization, a feature central to the training and performance measurement aspects of those claims in US6968001.

Obviousness Analysis under 35 U.S.C. § 103

This analysis identifies combinations of prior art that would render the claims of US patent 6968001 obvious to a person having ordinary skill in the art (PHOSITA). The motivation to combine these references would stem from the desire to improve equalizer performance, adaptability, and efficiency in communication systems, especially in the context of time-varying channels and variable data rates.

A PHOSITA in the field of communication systems equalization would have a strong understanding of adaptive filters, various equalizer structures (e.g., FIR, DFE), performance metrics (e.g., MSE, C/I, SINR), and the challenges of optimizing equalizer performance in dynamic environments. They would also be aware of the trade-offs between equalizer length, adaptation speed, and steady-state performance.

Combination 1: US5666378A in view of US5268930A and general knowledge of adaptive equalizers.

This combination would render obvious the method and apparatus claims (Claims 1, 11, 12, 13, and 15) related to training an equalizer with different configurations and selecting based on performance, particularly for equalizers whose configurations involve filter coefficients.

• US5666378A (High performance modem using pilot symbols for equalization and frame synchronization): This patent discloses using pilot symbols for equalization and synchronization in a modem. This directly addresses the "training the equalizer on a received pilot signal" aspect found in claims 13 and 15, and the general concept of using a "known sequence of samples" for training in claim 2. It teaches that pilot signals can be used to perform channel state information (CSI) measurements, which are then used to precondition data for transmission.
• US5268930A (Decision feedback equalizer): This patent describes a decision feedback equalizer (DFE). A DFE is a type of nonlinear equalizer that reduces intersymbol interference (ISI) and consists of a tapped delay line with a forward and feedback filter. DFEs are known to adapt based on actual decisions and do not amplify noise, making them effective for high-speed links. A PHOSITA would understand that varying the lengths of the feedforward and feedback filters in a DFE constitutes different equalizer configurations. The concept of setting filter coefficients to zero to effectively change equalizer length is a well-known technique in adaptive filtering.
• Motivation for Combination: A PHOSITA would be motivated to combine these references to enhance the performance and adaptability of equalizers in communication systems. US5666378A provides the mechanism of using pilot signals for training and performance estimation. US5268930A (and the general knowledge of DFEs) offers a specific type of equalizer with adjustable filter lengths, which can be seen as different "configurations." The problem of optimizing equalizer performance for varying channel conditions (as described in US6968001) is a known challenge. Adaptive equalizers are commonly used to automatically adjust to time-varying channel properties. Therefore, it would be obvious to a PHOSITA to train a DFE, as described in US5268930A, using pilot symbols as disclosed in US5666378A, and to evaluate the performance of different DFE configurations (e.g., varying tap lengths) to select the optimal one. The choice of different filter coefficients directly relates to "determining a first/second set of values for the set of parameters" and "setting a second set of values...effectively changes the configuration of the equalizer" as stated in claims 1, 11, 12, 13, and 15. The estimation of a "performance parameter" (e.g., C/I or MSE) is also a standard practice for evaluating equalizer performance.

Combination 2: US20020196844A1 in view of general knowledge of adaptive equalizers and performance metrics.

This combination would target the method and apparatus claims, focusing on adaptive equalization and the general concept of trying different equalizer parameters and selecting the best one.

• US20020196844A1 (Adaptive equalizer system for short burst modems and link hopping radio networks): This reference explicitly discusses adaptive equalizer systems, which are designed to adapt to time-varying properties of the communication channel. It would be understood by a PHOSITA that adaptive equalizers inherently involve adjusting filter coefficients or other parameters to optimize performance. Adaptive equalization involves calculating parameters of the equalizing filter based on the received signal, often using training signals or statistical models.
• General Knowledge of Adaptive Equalizers and Performance Metrics: It is common knowledge in the field that adaptive equalizers constantly change their filter characteristics over time to track time-varying channels. Algorithms like Least Mean Square (LMS) and Recursive Least Squares (RLS) are widely used to determine tap coefficients and update them. Performance metrics such as Carrier-to-Interference (C/I) ratio, Signal-to-Noise Ratio (SNR), Mean Square Error (MSE), or Signal to Interference and Noise Ratio (SINR) are standard for evaluating equalizer effectiveness.
• Motivation for Combination: Given that adaptive equalizers (as in US20020196844A1) are designed to handle varying channel conditions, a PHOSITA would be motivated to systematically explore different operating "configurations" or "parameters" of such an equalizer to optimize its performance. This optimization would naturally involve defining different sets of parameters, training the equalizer with these sets, estimating a performance parameter for each, comparing these parameters, and selecting the best configuration for subsequent data processing. This directly addresses the core method of US6968001 claims. The patent itself notes that "optimizing the equalizer by selecting the number of taps is difficult, as this requires a balancing of competing goals" and that an "optimum number of taps balances such considerations and compromises between good steady-state performance and good transient performance." This highlights the known problem that US6968001 attempts to solve, and the proposed solution would be an obvious application of known adaptive equalization techniques.

Combination 3: US5787118A in view of US6735244B1 and knowledge of common equalizer parameters.

This combination focuses on the broader concept of varying equalizer parameters beyond just tap coefficients, such as phase offset or sector identifiers.

• US5787118A (Adaptive diversity equalizer): This patent describes an adaptive diversity equalizer, implying the handling of multiple received signals, possibly from different paths or antennas, to improve overall signal quality. Diversity techniques are used to compensate for fading channel impairments and often involve multiple receiving antennas. While the specific parameters it varies are not explicitly detailed in the abstract, the term "diversity" suggests the possibility of managing multiple input streams or channels.
• US6735244B1 (Data transmission system and receiver unit thereof): This patent broadly covers a data transmission system and receiver unit. While the abstract does not specify equalizer parameters, it represents general knowledge in receiver design.
• Motivation for Combination: A PHOSITA would understand that in complex communication environments, especially those involving diversity or multiple possible signal sources (e.g., soft handoff in cellular systems), an equalizer's optimal performance might depend on parameters beyond just filter tap coefficients. For instance, in a soft handoff situation, a receiver might be able to receive data samples from multiple transmitters, and a "sector identifier" could be a relevant parameter to optimize reception. US6968001 explicitly mentions that equalizer parameters can include "a DC offset value or a phase offset value for the input samples, or a sector identifier." US5787118A, dealing with diversity, would motivate a PHOSITA to consider how different signal paths or sources could be treated differently by an equalizer. It would be obvious to extend the concept of trying different equalizer configurations (as in Combination 1 and 2) to include other known communication system parameters such as phase offset (for accurate symbol detection) or sector identifiers (for multi-cell reception) to find the best reception quality in a system context described by US6735244B1.

Obviousness Considerations under 35 U.S.C. § 103

The legal standard for obviousness under 35 U.S.C. § 103 requires determining whether "the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains."

The claims of US patent 6968001 broadly cover a method and apparatus for optimizing an equalizer by iteratively testing different parameter sets, measuring performance, comparing, selecting the best, and configuring the equalizer. The problem of optimizing equalizer performance for time-varying channels is a known challenge in communication systems. Adaptive equalizers, by their nature, seek to automatically adjust to channel conditions.

The prior art demonstrates that:

• Adaptive equalizers were well-known and used to combat ISI in time-varying channels.
• Decision Feedback Equalizers (DFEs) were known as a type of adaptive equalizer with adjustable forward and feedback filter lengths.
• The use of pilot signals for training equalizers and estimating performance (e.g., C/I, MSE) was a standard practice.
• The concept of varying equalizer "parameters" or "configurations" to optimize performance was also implicitly or explicitly understood in the context of adaptive equalizers, where coefficients are continuously adjusted. The explicit mention in US6968001 of dynamically adjusting the effective length of an equalizer by setting tap coefficients to zero is a known technique.
• The use of performance metrics (like C/I, MSE, SINR) for comparing different equalizer settings was standard.

Therefore, a PHOSITA, seeking to improve the "universal" performance of a receiver over a variety of channel conditions and rates of channel variation (the stated goal of US6968001), would have been motivated to combine these known elements. The idea of "virtual parallel equalizers" in US6968001, where a single piece of hardware is reconfigured rapidly to emulate multiple equalizers, leverages the idle time of a fast equalizer. This is an efficient use of existing resources, a common engineering goal. Given that training and filtering take "only a fraction of the allowable time T", the idea of performing multiple trainings sequentially within a half-slot time would be an obvious implementation choice to maximize resource utilization and adapt to varying conditions.

The specific "equalizer parameters" beyond tap coefficients, such as DC offset, phase offset, or sector identifiers, are also well-known aspects of receiver design and signal processing. Applying the iterative optimization method to these parameters would be a straightforward extension of known adaptive equalization principles.

For these reasons, the claims of US patent 6968001, particularly those related to determining multiple equalizer configurations, training, estimating performance, comparing, selecting, and then configuring the equalizer based on that selection, would have been obvious to a PHOSITA at the time of the invention.