Abstract: A multi-stage interference suppression receiver includes a short equalizer section configured to operate on a first portion of a received signal received over a channel to produce a first equalized signal and a first estimate of the channel, a channel estimator section configured to operate on the first equalized signal to produce a second equalized signal, the channel estimator section comprising a linear estimator and a non-linear estimator, a long equalizer section configured to operate on a second portion of the received signal to produce a first estimate of symbols in the received signal and a second estimate of the channel and an interference canceller section configured to operate on the first estimate of symbols in the received signal to generate a second estimate of symbols in the received signal based on, at least in part, the second estimate of the channel.

Abstract: A novel symbol estimation method produces intersymbol interference free symbols by detecting interfering symbols in an interfering channel. A channel estimate is refined for additional improvements. The method can lends itself as a serial or parallel algorithm implementation. The symbol estimation method includes using an initial estimate of received symbols and calculating a refined estimate of the received symbols using a channel estimate. The refined estimate is calculated by performing parameterization of intersymbol interference by symbols other than the symbol being refined and selecting a refined value for the symbol being refined by evaluating an optimization function. Symbol estimates are refined in multiple iterations, until a predetermined iteration termination criterion is met. Parameterization of ISI contribution of other symbols results in reduced computation by reducing total number of unknown variables in the refinement operation.

Abstract: A method for suppressing interference in a wireless communication comprises receiving a burst of symbols, filtering the burst of symbols using an interference suppression filter with a first plurality of weights, decoding the filtered burst of symbols to generate data corresponding to the burst of symbols, encoding the data to generate a re-encoded burst of symbols, calculating a second plurality of weights for the interference suppression filter based upon the re-encoded burst of symbols, filtering the re-encoded burst of symbols using the interference suppression filter with the second plurality of weights, and decoding the filtered re-encoded burst of symbols.

Abstract: Systems and methods for interference cancellation at a receiver in a wireless communication system are provided. In one aspect, a method for interference cancellation is provided. The method comprises providing total received chips received from a plurality of cells. The method also comprises successively estimating received chips for each of the plurality of cells in a plurality of iterations, wherein each of the plurality of iterations after a first iteration comprises canceling previously estimated received chips for one or more of the plurality of cells from the total received chips, and estimating received chips for one of the plurality of cells using the total received chips with the previously estimated received chips for the one or more of the plurality of cells cancelled out.

Abstract: Systems and methods for multi-user interference cancellation are provided. In one aspect of the disclosure, an apparatus is provided. The apparatus comprises a processing unit configured to process received chips into received symbols for a plurality of users and a detection unit configured to detect user symbols from the received symbols. The apparatus also comprises an interference cancellation unit configured to compute multi-user interference using the detected user symbols and to remove the computed multi-user interference from the received symbols. The apparatus further comprises a redetection unit configured to redetect user symbols from the received symbols with the computed multi-user interference removed.

Abstract: Systems and methods for symbol detection using sub-constellations are provided. In one aspect of the disclosure, an apparatus is provided. The apparatus comprises a processing unit configured to process received chips into received symbols for a plurality of users, a first detection unit configured to detect first components of user symbols for the plurality of users based on the received symbols and a computation unit configured to compute a portion of the received symbols due to the first components of the user symbols. The apparatus further comprises a second detection unit configured to detect second components of the user symbols based on the received symbols with the computed portion removed and a combining unit configured to detect the user symbols by combining the first components of the user symbols with the respective second components of the user symbols.

Abstract: Systems and methods for multi-user detection in a multiple access system are provided. In one aspect, an apparatus is provided. The apparatus comprises a processing unit configured to process received chips into received symbols for a plurality of users and a computation unit configured to compute a multi-user matrix using a Hadamard matrix, wherein the multi-user matrix relates user symbols for the plurality of users to the received symbols. The apparatus further comprises a detection unit configured to detect the user symbols for the plurality of users using the received symbols and the computed multi-user matrix.

Abstract: Systems and methods for inter-cell interference cancellation are provided. In one aspect of the disclosure, an apparatus is provided. The apparatus comprises a cell computation unit configured to compute receive chips for a first interfering cell and a subtraction unit configured to remove the computed receive chips for the first interfering cell from received chips at a receiver. The apparatus further comprises a processing unit configured to process the received chips with the computed receive chips for the first interfering cell removed into received symbols and a detection unit configured to detect user symbols for a target cell from the received symbols.

Abstract: Systems and methods for multi-user detection are provided. In one aspect of the disclosure, an apparatus is provided. The apparatus comprises a processing unit configured to process a plurality of received chips into a plurality of received symbols for a plurality of users. The apparatus further comprises a computation unit configured to compute a multi-user matrix relating a plurality of user symbols for the plurality of users to the plurality of received symbols and a detection unit configured to detect the plurality of user symbols for the plurality of users using the computed multi-user matrix and the plurality of received symbols.

Abstract: Systems and methods for data-aided channel estimation are provided. In one aspect of the disclosure, a channel estimation apparatus is provided. The apparatus comprises a first processing unit configured to process received chips into received symbols and a detection unit configured to detect user symbols from the received symbols. The apparatus further comprises a second processing unit configured to process the detected user symbols into estimated transmit chips and a channel computation unit configured to estimate a channel based on the estimated transmit chips and the received chips.

Abstract: A method for estimating timing in a wireless communication comprises the steps of receiving a plurality of symbol bursts corresponding to a plurality of time slots and selecting a subset of symbols from a first symbol burst of the plurality of symbol bursts. The subset comprises a first midamble symbol. The method further comprises the steps of calculating, for each symbol in the subset, a corresponding midamble estimation error, and determining the lowest calculated midamble estimation error to determine a timing for the first symbol burst. The method further comprises the steps of processing the first symbol burst utilizing the timing determined for the first symbol burst, and processing a second symbol burst of the plurality of symbol bursts utilizing the timing determined for the first symbol burst.

Abstract: A method for timing and frequency synchronization in a wireless system is provided. The method comprises the steps of receiving a burst of symbols, selecting a subset of the burst of symbols, iteratively adjusting the subset of the burst of symbols by a plurality of timing offsets and calculating, for each timing offset, a first performance metric corresponding to the adjusted subset. The method further comprises the steps of determining one of the plurality of timing offsets to be a preferred timing offset based upon the first performance metric thereof, iteratively rotating the subset of the burst of symbols by a plurality of frequency offsets and calculating, for each frequency offset, a second performance metric corresponding to the rotated subset, and determining one of the plurality of frequency offsets to be a preferred frequency offset based upon the second performance metric thereof.

Abstract: A method for suppressing interference in a wireless communication is provided. The method comprises receiving a burst of symbols, generating a plurality of timing hypotheses for the burst of symbols, and calculating, for each timing hypothesis, a plurality of weights for an interference suppression filter based upon a subset of the burst of symbols. The method further comprises, for each timing hypothesis, filtering the subset of the burst of symbols using the interference suppression filter with the corresponding plurality of weights, and selecting one of the plurality of timing hypotheses corresponding to a selection criteria. The method further comprises equalizing and decoding the filtered burst of symbols based upon the selected one of the plurality of timing hypotheses.

Abstract: Techniques for performing adaptive channel estimation are described. A receiver derives channel estimates for a wireless channel based on received pilot symbols and at least one estimation parameter. The receiver updates the at least one estimation parameter based on the received pilot symbols. The at least one estimation parameter may be for an innovations representation model of the wireless channel and may be updated based on a cost function with costs defined by prediction errors. In one design, the receiver derives predicted pilot symbols based on the received pilot symbols and the at least one estimation parameter, determines prediction errors based on the received pilot symbols and the predicted pilot symbols, and further derives error gradients based on the prediction errors. The receiver then updates the at least one estimation parameter based on the error gradients and the prediction errors, e.g., if a stability test is satisfied.

Abstract: Techniques for recovering a desired transmission in the presence of interfering transmissions are described. For iterative detection and cancellation, multiple groups of code channels are formed for a plurality of code channels for at least one sector. Processing is performed for the multiple groups of code channels in multiple iterations. For each iteration, data detection and signal cancellation are performed for the multiple groups of code channels in multiple stages, e.g., in a sequential order starting with the strongest group to the weakest group. Each stage of each iteration may perform data detection, signal reconstruction, and signal cancellation. Each stage of each iteration may also perform equalization, data detection, signal reconstruction, and signal cancellation.

Abstract: Techniques for recovering a desired transmission in the presence of interfering transmissions are described. For successive equalization and cancellation (SEC), equalization is performed on a received signal to obtain an equalized signal for a first set of code channels. The first set may include all code channels for one sector, a subset of all code channels for one sector, multiple code channels for multiple sectors, etc. Data detection is then performed on the equalized signal to obtain a detected signal for the first set of code channels. A signal for the first set of code channels is reconstructed based on the detected signal. The reconstructed signal for the first set of code channels is then canceled from the received signal. Equalization, data detection, reconstruction, and cancellation are performed for at least one additional set of code channels in similar manner.

Abstract: This disclosure is directed to techniques for estimating signal-to-noise ratio (SNR) of signals received by a wireless communication device. The techniques take advantage of spatial receive diversity in a wireless communication device to achieve accurate estimates of SNR. In general, a spatial projection wiener filter function can be applied to incoming symbol estimates to support efficient computation of SNR. The estimated SNR can be used to produce power control commands for use in forward power control.

Abstract: Techniques for deriving a channel estimate using a scattered pilot and a continual pilot are described. The scattered pilot is sent on different sets of carriers in different symbol periods. The continual pilot is sent in each symbol period on irregularly spaced carriers. The scattered pilot is used to identify the indices of channel taps of interest, e.g., L strongest channel taps. The continual pilot is used to determine the complex gains of these L channel taps. A receiver derives a channel impulse response estimate based on received pilot symbols for the scattered pilot, identifies the L strongest channel taps, and determines the indices of these L strongest channel taps. The receiver forms a Fourier sub-matrix based on the L tap indices and determines the gains of the L channel taps based on received pilot symbols for the continual pilot and the Fourier sub-matrix.

Abstract: A decision feedback equalizer includes a chip estimate buffer that forms chip estimates into a vector. A CCK decoder decodes the vector of chip estimates, and a CCK encoder, connected with the CCK decoder, re-encodes the vector of chip estimates into a valid CCK code word. At the same time, a chip slicer provides direct sliced chips from the chip estimates. An update module then forms a hybrid vector from the valid CCK code-word and the direct sliced chips for input to the feedback filter of the decision feedback equalizer. The hybrid feedback filter input vector reflects the CCK coding gain of its re-encoded portion thereby reducing the estimated chip error rate to improve the performance of the decision feedback equalizer.

Abstract: A decision feedback equalizer includes a chip estimate buffer that forms chip estimates into a vector. A CCK decoder decodes the vector of chip estimates, and a CCK encoder, connected with the CCK decoder, re-encodes the vector of chip estimates into a valid CCK code word. At the same time, a chip slicer provides direct sliced chips from the chip estimates. An update module then forms a hybrid vector from the valid CCK code-word and the direct sliced chips for input to the feedback filter of the decision feedback equalizer. The hybrid feedback filter input vector reflects the CCK coding gain of its re-encoded portion thereby reducing the estimated chip error rate to improve the performance of the decision feedback equalizer.