# Douglas A. Cairns, Durham US

## Douglas A. Cairns, Durham, NC US

Patent application number | Description | Published |
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20080211704 | Distributed Sigma-Delta Sensor Network - The sensor network described herein uses a distributed sigma-delta converter, where each of a plurality of sensor nodes includes a sigma-delta modulator communicatively coupled to a remotely located sigma-delta processor in a control hub. Each sensor node generates a serial bit stream representative of a sensor output signal. The control hub includes a plurality of signal processors, each of which receive and digitally process the serial bit stream wirelessly transmitted by a corresponding sensor node. A controller in the control hub analyzes the digital output from each signal processor to determine one or more characteristics of the sensor network. | 09-04-2008 |

20080267261 | Efficient Computation of a Waveform Correlation Matrix - A method and apparatus for reducing the complexity of waveform correlation computations used by a multicode receiver is described herein. One exemplary multicode receiver includes a despreading unit, channel estimator, and waveform correlation calculator. The despreading unit despreads a received multicode signal to generate despread symbols. The channel estimator estimates channel coefficients associated with the despread symbols. The waveform correlation calculator determines waveform correlations between the transmitted symbols in successive processing windows that span two or more symbol periods and that overlap in time. To reduce the computational complexity associated with computing waveform correlations, the calculator may reuse channel coefficients and/or net channel correlations for multiple symbol periods and/or processing windows. The calculator may also reduce complexity by reusing one or more waveform correlations from a previous processing window as waveform correlations for one or more subsequent processing windows and/or by exploiting the Hermitian symmetry of the waveform correlation matrix. | 10-30-2008 |

20080267262 | Efficient Computaton of Soft Scaling Factors for Linear Multi-User Detector - A symbol detector converts initial symbol estimates of received symbols to soft estimates for decoding. The symbol detector computes spreading waveform correlations between a spreading waveform for a symbol of interest and spreading waveforms for one or more interfering symbols. Interference rejection terms are computed by scaling the spreading waveform correlations by corresponding signal powers and compensating for noise. A soft scaling factor for the symbol of interest is computed from the interference rejection terms. The soft scaling factors are then applied to the initial symbol estimates to generate the soft estimates. | 10-30-2008 |

20080267265 | Robust Multicode Detector for HSDPA - Detecting a symbol of interest comprises despreading a received signal to obtain despread values corresponding to the symbol of interest and to one or more interfering symbols, combining the despread values to generate combined values for the symbol of interest and the interfering symbols, computing spreading waveform correlations between the spreading waveform for the symbol of interest and the spreading waveforms for the interfering symbols, computing interference rejection terms representing the interference present in the combined value for the symbol of interest attributable to the interfering symbols based on the spreading waveform correlations, and generating an estimate of the symbol of interest by combining the combined values with the interference rejection terms. The interference rejection terms are computed by scaling the spreading waveform correlations by corresponding signal powers and compensating the estimates for noise. This provides a robust interference model that avoids numerical problems associated with conventional joint detection. | 10-30-2008 |

20080291887 | MMSE Channel Estimation in a Communications Receiver - Methods and apparatus are disclosed for calculating a channel response for use in received signal processing. In an exemplary embodiment, a method comprises calculating a channel response correlation matrix based on measured channel responses derived from pilot symbols in a received signal and forming a traffic data correlation matrix based on measurements of traffic symbols in the received signal. The traffic data correlation matrix, the channel response correlation matrix, and the measured channel responses are used in an minimum mean-squared error (MMSE) estimation process to calculate the channel response estimates. In one or more embodiments, the calculated channel response estimates comprise estimates of net channel response corresponding to signal processing delays in a G-RAKE receiver. An exemplary receiver circuit comprises a baseband processor configured to calculate channel response estimates according to one or more of the disclosed methods. | 11-27-2008 |

20090023437 | EFFICIENT METHOD FOR FORMING AND SHARING IMPAIRMENT COVARIANCE MATRIX - The technology comprises method(s) and apparatus for operating a telecommunications system. In its basic form the method comprises providing plural channelization codes for potential use by an uplink receiver; using unused channelization codes of the plural codes to generate an estimate of an impairment covariance matrix; and using the estimate of the impairment covariance matrix to form a processing parameter. For example, the processing parameter can be one or more weight values which, in turn, are can be used for generating a combined output signal. | 01-22-2009 |

20090052584 | Selective Signal Demodulation Method and Apparatus - Signal quality estimation and demodulation are tailored to the received signal quality. According to one embodiment, a received signal is processed by determining a first set of combining weights based on a first impairment covariance estimate derived assuming a low signal quality environment. A second set of combining weights is determined based on a second impairment covariance estimate derived assuming a high signal quality environment. A metric is determined corresponding to the difference between symbol estimates derived from the second set of combining weights and hard symbol decisions. The received signal is demodulated based on the second set of combining weights if the metric satisfies a threshold indicating high signal quality and otherwise based on the first set of combining weights. | 02-26-2009 |

20090116455 | Method and Apparatus for Code Power Parameter Estimation for Received Signal Processing - As taught herein channelization code power estimates are generated for a number of data channels in a received CDMA signal based on a joint determination process. Joint processing in this context yields improved estimation of data channel code powers and corresponding estimations of noise variance. These improvements arise from exploitation of joint processing of measured data value correlations across two or more data channel codes represented in the received signal. In one or more embodiments, joint determination of data channel code powers comprises forming a correlation matrix as a weighted average of correlations determined for a plurality of data channels. In one or more other embodiments, joint determination of data channel code powers comprises jointly fitting the correlation matrices for a plurality of data channels in a least squares error estimation process. | 05-07-2009 |

20090149147 | Speed-Based, Hybrid Parametric/Non-parametric Equalization - A mobile receiver having a multi-mode interference suppression function and a way to estimate its speed utilizes a parametric approach to interference suppression at high speeds, and a nonparametric approach at low speeds. In particular, if the mobile receiver is currently operating in a nonparametric mode and its speed exceeds a first predetermined threshold, the mobile receiver switches to a parametric mode. Conversely, if the mobile receiver is currently in parametric mode and its speed is less than a second predetermined threshold, the mobile receiver switches to nonparametric mode. In one embodiment, the speed may be estimated by a Doppler frequency in the received signal, and the thresholds are Doppler frequencies. In one embodiment, the first and second thresholds are different, creating a hysteresis in the mode switching. | 06-11-2009 |

20090202005 | Method and Apparatus for Improved Channel Estimation for Communications Signal Processing - Teachings presented herein present a “whitening” channel estimation method and apparatus that produce high-quality net channel estimates for processing a received signal, such as a received CDMA signal. Processing includes forming an initial least squares problem (for medium channel estimates) using known pilot values and corresponding pilot observations for the received signal, transforming the initial least squares problem using a whitening transformation term, and solving the transformed least squares problem to obtain whitened medium channel estimates. The whitening transformation term may be determined, for example, by carrying out a Cholesky factorization of a (traffic) data correlation matrix, which can be obtained from traffic data values for the received signal. Processing further includes converting the whitened medium channel estimates into whitened net channel estimates, which consider the effects of transmit/receive filtering. | 08-13-2009 |

20090213909 | Code Power Estimation for MIMO Signals - Methods and apparatus for estimating code-reuse interference associated with a received multi-stream multiple-input multiple-output (MIMO) signal are disclosed. An estimate for the data-to-pilot power ratio, Γ | 08-27-2009 |

20090213945 | Reduced Complexity Parametric Covariance Estimation for Precoded MIMO Transmissions - A model-based technique for estimating impairment covariance associated with a MIMO signal is disclosed. In an exemplary method, an impairment model is constructed for a received composite information signal comprising at least a first data stream transmitted from first and second antennas according to a first antenna weighting vector. The impairment model includes first and second model terms corresponding to the first and second antennas, respectively, but in several embodiments does not include a cross-antenna interference term. In another embodiment, an impairment model for a received MIMO signal is constructed by computing an impairment model term for each antenna and an additional term to account for preceding interference in a single-stream MIMO transmission scenario. The impairment terms are grouped so that only two associated scaling terms are unknown; values for the scaling terms are estimated by fitting the model to measured impairment covariance values. | 08-27-2009 |

20090245441 | ROBUST ITERATIVE LINEAR SYSTEM SOLVERS - In receiving equipment such as a mobile terminal ( | 10-01-2009 |

20090268787 | Method and Apparatus for Compensating for Processing Timing Misalignment in a Communication Receiver - According to the teachings presented herein, a wireless communication apparatus compensates for timing misalignment in its received signal processing. In at least one embodiment, the apparatus estimates a set of path delays for a received signal and sets processing delays on the estimated path delays. The apparatus jointly hypothesizes combinations of fractional timing offsets for two or more paths, and computes a decision metric for each joint hypothesis that indicates the accuracy of the joint hypothesis. As non-limiting examples, the decision metric may be a signal quality metric, or a distance metric (such as between a measured net channel response and an effective net channel response reconstructed as a function of the combination of fractional timing offsets included in the joint hypothesis). The apparatus evaluates the decision metrics to identify a best estimate of timing misalignment, and correspondingly compensates coherent processing of the received signal. | 10-29-2009 |

20090304132 | Method and Apparatus for Efficient Estimation of Interference in a Wireless Receiver - Methods and apparatus for determining an impairment covariance matrix for use in an interference-suppressing CDMA receiver are disclosed. In several of the disclosed embodiments, precise information regarding signal propagation delays is not needed. An exemplary method includes the selection of a plurality of processing delays for processing a received CDMA signal. Net channel coefficients for the processing delays are estimated and used to calculate an impairment covariance matrix. The impairment covariance matrix is calculated as a function of the estimated net channel coefficients and the processing delays, without estimating a propagation medium channel response for the received signal. | 12-10-2009 |

20090316674 | METHOD AND APPARATUS FOR DEMODULATION OF QAM SIGNAL USING SYMBOL-SPECIFIC AMPLITUDE REFERENCE ESTIMATION - According to the teachings presented herein, “spreading code” knowledge is used in forming amplitude references for QAM demodulation in a DS-CDMA receiver. Here, “spreading code” broadly refers to spreading/channelization codes, scrambling codes, or the product of such codes. Further, these teachings apply to any linear DS-CDMA demodulator, such as Rake, Generalized Rake (G-Rake), or chip equalizer, and to nonlinear demodulators that employ linear filtering, such as decision feedback equalizers (DFEs). Advantageously, the determination of symbol-specific amplitude references relies on shared correlation estimates and/or shared combining weights that are common to two or more symbols of interest, thereby significantly reducing processing requirements as compared to the use of symbol-specific impairment correlation estimates. | 12-24-2009 |

20100054309 | NONPARAMETRIC MIMO G-RAKE RECEIVER - With a nonparametric G-Rake receiver, combining weights may be determined using a nonparametric mechanism in multiple-input, multiple-output (MIMO) scenarios. In an example embodiment, a method for a receiving device having a nonparametric G-Rake receiver entails calculating an impairment covariance matrix and determining combining weights. More specifically, the impairment covariance matrix is calculated based on a pilot channel using a nonparametric mechanism in a MIMO scenario in which a code-reuse interference term exists. The combining weights are determined for the nonparametric G-Rake receiver responsive to the impairment covariance matrix and by accounting for the code-reuse interference term. | 03-04-2010 |

20100172396 | METHOD AND APPARATUS FOR SETTING RECEIVED SIGNAL PROCESSING DELAYS AS A FUNCTION OF CHANNEL DISPERSIVENESS - A method and apparatus provide for setting processing delay assignments in a CDMA receiver using a flat-channel placement or using a dispersive channel placement, in dependence on characterizing the channel as flat or dispersive. For example, a receiver maintains a logical flag reliably indicating the current channel state as flat or dispersive, and assigns or otherwise sets processing delays—e.g., for received signal demodulation—using a flat-channel placement algorithm or a dispersive-channel placement algorithm. The “flat-channel” placement algorithm generally provides better performance in flat-channel environments, and the “dispersive-channel” placement algorithm generally provides better performance in dispersive channel environments. Such processing may be regarded as “activating” a simplified processing delay placement grid that offers better performance if the channel truly is flat, with the underlying advantage of providing a reliable mechanism for detecting flat channel conditions. | 07-08-2010 |

20100238980 | Signal Reception with Adjustable Processing Delay Placement - The placement of processing delays may be adjusted to facilitate signal reception. In an example embodiment, a composite signal having multiple signal images corresponding to multiple reception delays is received. A root-mean-square (RMS) delay spread is ascertained for the multiple reception delays that correspond to the multiple signal images of the composite signal. A set of temporal points is produced responsive to the RMS delay spread. Multiple processing delays are placed based on the set of temporal points. In different example implementations, the set of temporal points (e.g., of a grid) may be produced by adjusting a spacing between temporal points, by adjusting a total number of temporal points in the set, or by changing a center location of the set. The spacing and number of points may be adjusted responsive to the RMS delay spread. The center location may be adjusted responsive to at least one calculated delay. | 09-23-2010 |

20100303132 | Method and Apparatus for Allocating Processing Delays in Multi-Carrier Systems - A multi-carrier linear equalization receiver, e.g., a RAKE receiver or chip equalization receiver, is described herein. The multi-carrier receiver distributes processing delays among a plurality of received carriers based on a dispersion determined for each carrier. The receiver initially allocates a minimum number of processing delays sufficient for light dispersion to each carrier. For the dispersive carriers, the receiver allocates one or more additional processing delays. In one embodiment, the additional processing delays are allocated to the dispersive carriers based on SIR. | 12-02-2010 |

20110007793 | JOINT TIME/FREQUENCY PROCESSING FOR WIRELESS RECEIVERS - Channel estimation and/or equalization processing is performed in a wireless receiver in two stages. The first stage involves pre-filtering in the frequency domain to compact a grid-based representation of the net channel. The second stage involves implementing reduced-complexity time domain channel estimation and/or equalization. According to one embodiment, a received signal transmitted over a net channel is processed by pre-filtering the received signal in the frequency domain. The frequency domain pre-filtering compacts an N-tap effective grid-based representation of the net channel into a K-tap compacted grid-based representation of the net channel where K | 01-13-2011 |

20110009150 | METHOD OF CLOSED LOOP POWER CONTROL ADJUSTED BY SELF-INTERFERENCE - A method and apparatus for controlling the transmit power of a mobile device in a mobile communication network takes the level of self-interference into account to perform inner-loop power control. For normal inner-loop power control, a signal quality estimate is compared to a signal quality target and power control commands are generated based on the comparison. When self-interference is the dominant impairment in the received signal, a “fast break” is introduced to change inner-loop power control command generation. The amount of self-interference is determined based on the delay spread of the channel. | 01-13-2011 |

20110014874 | CONVOLUTIONAL IMPAIRMENT COVARIANCE ESTIMATION METHOD AND APPARATUS - Path delay information generated by a path searcher module of a wireless receiver is used to generate net channel coefficients for use in suppressing interference from a received signal. According to one embodiment, interference is suppressed from a signal transmitted over a communication channel including transmit and receive pulse shaping filters and a radio channel by generating net channel coefficients for the communication channel at processing delays such as G-Rake finger delays or chip equalizer tap delays. Medium channel coefficients are generated for the radio channel at estimated path delays as a function of the net channel coefficients. The net channel coefficients are regenerated at arbitrary delays as a function of the medium channel coefficients and an impairment covariance estimate is generated based at least in part on the regenerated net channel coefficients. | 01-20-2011 |

20110075706 | CHANNEL GEOMETRY DETECTOR - Adaptive reconfiguration of a wireless receiver is enabled based on channel geometry. According to an embodiment, the wireless receiver includes a geometry factor processing module and signal processing modules, e.g. such as but not limited to an SIR estimation module, a power estimation module, a despreading module, a low-pass filter, a combing weight generation module, a coefficient estimation module, a synchronization control channel interference canceller module, etc. The geometry factor processing module determines a geometry factor for the channel over which signals are transmitted to the wireless receiver, the geometry factor being a measure of the ratio of total transmitted power received by the wireless receiver to total interference plus noise power at the wireless receiver. One or more of the receiver signal processing modules are reconfigurable based on the geometry factor. | 03-31-2011 |

20110129000 | METHOD AND APPARATUS FOR EFFICIENT AMLD MATRIX COMPUTATIONS - The computation of code-specific channel matrices for an Assisted Maximum Likelihood Detection (AMLD) receiver comprises separately computing high rate matrices that change each symbol period, and a low rate matrix that is substantially constant over a plurality of symbol periods. The high and low rate matrices are combined to generate a code-specific channel matrix for each receiver stage. The high rate matrices include scrambling and spreading code information, and the low rate matrices include information on the net channel response and combining weights. The low rate matrices are efficiently computed by a linear convolution in the frequency domain of the net channel response and combining weights (with zero padding to avoid circular convolution), then transforming the convolution to the time domain and extracting matrix elements. Where the combining weights are constant across stages, a common code-specific channel matrix may be computed and used in multiple AMLD receiver stages. | 06-02-2011 |

20110142101 | DATA TO PILOT RATIO ESTIMATION - A CDMA receiver computes an accurate estimate of the data to pilot power ratio. First, a biased estimate of the data to pilot power ratio is obtained from the data channel. A multiplicative correction factor is then computed from the pilot channel, and applied to the biased data to pilot power ratio estimate. | 06-16-2011 |

20110206167 | Data-Aided SIR Estimation - A signal-to-interference estimate is generated using unknown data symbols in place of or in addition to pilot symbols. Data received over a data channel (traffic channel or control channel) are collected. The data symbols are then used to compute an observation metric based on deviations of the data symbols from a predetermined set of possible data symbols, wherein one of the data symbols and symbol constellation is normalized. A data channel signal-to-interference ratio is then computed based on the observation metric. | 08-25-2011 |

20120219155 | METHODS AND DEVICES FOR ALLOCATING SCRAMBLING CODES - Methods and devices are provided whereby scrambling codes can be set in an improved way. In accordance with one embodiment a method is provided in a User Equipment for generating a second scrambling code or a second scrambling code group. The UE is configured for multi carrier operation receiving downlink transmission from a Universal Mobile Telecommunications System Terrestrial Radio Access Network on a set of at least two downlink carriers including an anchor carrier and at least a first secondary carrier. The method comprises determining a first scrambling code or a first scrambling code group associated with a first cell on the anchor carrier; and deriving a second scrambling code or a second scrambling code group associated with a second cell on said first secondary carrier using a predefined rule defining the relation between the second scrambling code or second scrambling code group and the first scrambling code or scrambling code group. Hereby interference suppression/cancellation processing is enabled in a receiver of a UE on secondary cells in multi-carrier scenarios that do not transmit the SCH, while minimizing the need for overhead in terms of signaling of the scrambling codes for neighbouring cells in a UTRAN system. Methods and devices for E-UTRAN are also described. | 08-30-2012 |