Abstract: In an example, time and frequency domain speech enhancement is implemented on a platform having a programmable device, such a PC or a smartphone running an OS. Echo cancellation is done first in time domain to cancel a dominant portion of the echo. Residual echo is cancelled jointly with noise reduction during a subsequent frequency domain stage. The time domain block uses a dual band, shorter length Adaptive Filter for faster convergence. Non-linear residual echo is cancelled based on an echo estimate and an error signal from the adaptive filters. A controller locates regions that had residual echo suppressed and which do not have speech and injects comfort noise. The controller can be full-duplex and operate non-linearly. An AGC selectively amplifies the frequency bins, based on the Gain function used by the residual echo and noise canceller.

Abstract: A method, a system and a computer program product for fast detection of the onset of a near-end signal is provided. An Acoustic Echo Canceller (AEC) attenuates an acoustic echo present in a tele-communication network. The AEC includes an adaptive filter that estimates the acoustic echo and generates an error signal. The error signal is the difference between the acoustic echo and the estimate of acoustic echo plus a near-end signal, if present. The method comprises computing an onset indicator parameter from the error signal and the estimate of acoustic echo. Several other parameters are subsequently calculated by using the onset indicator parameter, the error signal and the estimate of acoustic echo.

Abstract: An apparatus comprises a network physical layer and an activity sensor for sensing a packet and activating the network physical layer from shutdown. The network physical layer decodes a PHY header portion and a media access control header portion of a packet header. A MAC has a fixed hardware media access plane implementing IEEE 802.11 series MAC functionality and couples to a microprocessor. A MAC address parser receives the MAC header portion of the packet, for processing the MAC header portion of the packet, and for activating the MAC from a shutdown in response to recognizing a MAC address within the MAC header portion of the packet, such that the MAC is not activated if the MAC parser does not recognize the MAC address, wherein the MAC is operable, after activation, to perform MAC functionality without the microprocessor and to provide data from the packet to the microprocessor.

Abstract: A battery-powered WLAN communication device has an activity sensor operable to identify an available packet. A PHY module is awakened to begin receiving the packet. The PHY module decodes a full MAC address from a MAC portion of a header of the packet. A MAC address parser receives the MAC address and determines whether the packet is to be received by comparing the full MAC address to a MAC address of the WLAN communication device. The MAC address parser is awakened to perform the comparing and shutdown after. Packets to be received include beacon packets. A hardware centric MAC separate from the MAC address parser has a beacon processor capable of being awakened from a shutdown state to process a beacon packet. The PHY module, the MAC address parser, and the beacon processor module are operable to be awakened and shutdown independently of each other and of a microprocessor.

Abstract: A method, a system and a computer program product for fast detection of the onset of a near-end signal is provided. An Acoustic Echo Canceller (AEC) attenuates an acoustic echo present in a tele-communication network. The AEC includes an adaptive filter that estimates the acoustic echo and generates an error signal. The error signal is the difference between the acoustic echo and the estimate of acoustic echo plus a near-end signal, if present. The method comprises computing an onset indicator parameter from the error signal and the estimate of acoustic echo. Several other parameters are subsequently calculated by using the onset indicator parameter, the error signal and the estimate of acoustic echo. The presence of the near-end signal is detected with very low detection delay by using the parameters mentioned above and one or more threshold values.

Abstract: Passive listening in wireless communication. An activity sensor device senses a packet. A medium access control (MAC) address parser receives the packet, processes a header of the packet, and activates a MAC device in response to recognizing a MAC address within the header, such that the MAC device is not activated if the MAC address parser does not recognize the MAC address.

Abstract: Hardware-based beacon processing. A hardware-centric medium access control (MAC) device includes a packet receiver and a beacon processor. The packet receiver receives a plurality of packets comprising at least one beacon packet. The beacon processor receives packets of the plurality of packets and filters out unwanted packets of the plurality of packets without requiring the use of other components of the hardware-centric MAC device and without requiring the use of a microprocessor.

Abstract: A hardware-centric medium access control (MAC) device comprises a control plane module and a hardware media access planed module. The control plane module is configured for providing control functions of the hardware-centric MAC device. The hardware media access plane module communicatively coupled to the control plane module is configured for performing real-time data communication functions without requiring a microprocessor.

Abstract: A method and system for low-complexity implementation of a Viterbi Decoder with near optimal performance has been disclosed. The Viterbi decoding technique is diagrammatically represented as a trellis. The trellis includes various states at different time instants, and branches connecting these states. Each state has an associated state metric and a survivor path sequence, whereas each branch has a branch metric. The state metric for each current state is checked for crossing a predefined limit. If it crosses the predefined limit, the state metric is updated with a new metric that is obtained by subtracting a constant value from the state metric. Thereafter, the method finds a common path in the trellis at each state and updates the survivor path sequence of each state. The Most Significant Bits (MSBs) of the survivor path sequences of the states at a particular time instant are computed and the original data is decoded, based on the count of ‘0s’ and ‘1s’ in the MSBs.

Abstract: A hardware-centric medium access control (MAC) device comprises a control plane module and a hardware media access planed module. The control plane module is for providing control functions of the hardware-centric MAC device. The hardware media access plane module communicatively coupled to the control plane module is for performing real-time data communication functions without requiring a microprocessor.

Abstract: A method, system, and computer program product for frame and frequency synchronization in packet-based Orthogonal Frequency Division Multiplexing (OFDM) in wireless digital communication systems. An OFDM packet includes a preamble preceded by a Cyclic Prefix (CP). The method includes computing a timing metric for packet-based OFDM. The timing metric yields a sharp peak at a preamble boundary. The preamble boundary is detected, based on a threshold. The threshold is determined a priori, based on mean and variance of the timing metric at the preamble boundary and in its neighborhood. The mean and the variance are evaluated for an Additive White Gaussian Noise (AWGN) channel. The detection of the preamble boundary enables frame synchronization in packet-based OFDM. The method further involves the task of frequency-offset estimation, using the preamble. The frequency-offset estimation enables frequency synchronization in packet-based OFDM.

Abstract: Various embodiments of the present invention relate to a method and system for Vertical Bell Layered Space-Time (V-BLAST) detection with near Maximum Likelihood (ML) performance and low complexity. The V-BLAST system is a Multiple-Input Multiple-Output (MIMO) system. A receiver is provided that detects the data transmitted from the multiple transmitting antennas. The detection performance of such a method and system is better than that of linear receivers while keeping the complexity of the receiver marginally higher than that of the linear receivers. The detection performance of such a method and system is very close to that of the ML receiver while its complexity is much less than that of the ML receiver.

Abstract: The disclosed invention provides a method, a system and a computer program product for the maximum likelihood sequence estimation of transmitted MSK symbols. The disclosed invention provides a set of optimizations of the Viterbi algorithm for equalizing MSK symbols. The transmitted MSK symbols are alternately real and imaginary. Therefore, based on whether the transmitted MSK symbol is real or imaginary, the disclosed invention divides the set of Viterbi states into two sets of states. The disclosed invention obtains the surviving path only for the first set of states at stages corresponding to real transmitted symbols. A real hypothesis is used to obtain the surviving paths for the first set of states. The disclosed invention also obtains the surviving path only for the second set of states at stages corresponding to imaginary transmitted symbols. An imaginary hypothesis is used to obtain the surviving paths of the second set of states.

Abstract: The disclosed invention provides a system, a method and a computer program product for timing offset estimation for frequency selective fading channels in wireless communication systems. The disclosed invention first obtains a corrected received signal using the received signal and a pre-estimated timing offset. The pre-estimated timing offset is further tracked in two steps. In the first step a plurality of probable deviations in the pre-estimated timing offset are considered. Then a training sequence is used to determine an expected signal corresponding to each of the probable deviations. The corrected received signal is then shifted through the probable deviations. Thereafter error factor between the expected signals and corresponding shifted received signals is obtained. The probable deviation yielding optimum error factor is then identified as the first estimate of the deviation in timing offset.

Abstract: A system, method and computer program product for detecting a frequency burst in a received signal at a wireless receiver is disclosed. The invention predicts the current sample of the received signal by filtering the past samples of the received signal through an adaptive filter. A prediction error is further obtained by subtracting the actual current sample and the predicted current sample. The prediction error is then used to adapt the adaptive filter. Since the frequency burst is a substantially predictable signal, the adaptive filter adapts to accurately predict the samples of the frequency burst. Therefore, the prediction error decreases when the frequency burst is received at the receiver. The end of the frequency burst is identified using the prediction error at each discrete time instant.

Abstract: The present invention provides a method and system for clock and carrier recovery in a direct sequence spread spectrum communication system. The process involves the receiver receiving a digital signal that has been transmitted by a remote transmitter. The method for joint clock and carrier recovery comprises the following steps. The received signal is down-converted and the signal is then converted to digital form. The signal is de-spread to obtain the phase of the signal constellation. The clock error at the receiver is then estimated from the phase error of the signal constellation by means of an optimal linear estimator. The discrete carrier frequency offset of the received signal is then estimated from the estimated clock error. The optimal linear estimator used here for estimating the clock error is also the maximum likelihood estimator.

Abstract: A method and apparatus for multi-path channel characterization in a Direct Sequence Spread Spectrum based wireless communication system is provided. The multipath channel is modeled as a tapped delay line FIR filter with L taps corresponding to L paths. A pre-defined training sequence is transmitted over the multipath channel. The received signal is sampled and cross correlations are computed between the samples obtained and the spreading sequence for various time lags to obtain the symbol boundary. Thereafter, a desired set of L cross correlations for L time lags around the symbol boundary is estimated. For this, all the L possible sets of L cross correlations for L time lags around the symbol boundary are considered. The energy in the cross correlations corresponding to each considered set is calculated. The set of L cross correlations having the maximum energy is selected for tap computation. The tap coefficients are estimated by solving a set of L simultaneous linear equations.

Abstract: A method, system and computer program product for obtaining the reliability values for the hard decisions obtained by a Viterbi equalizer in a wireless communication system. A difference parameter is obtained for each Viterbi state at a stage while advancing the Viterbi trellis by the stage. The difference parameter for a Viterbi state at a stage is obtained by subtracting the path metric of the non-surviving path from the path metric of the surviving path for the Viterbi state at the stage. The difference parameter corresponding to the Viterbi state on the ML path at a stage is used as the reliability value for the hard decision obtained at L stages behind the stage, where L is the memory of the Viterbi trellis. A method for obtaining the accurate reliability values for the hard decisions corresponding to the last L stages of a truncated Viterbi trellis is also provided.

Abstract: A computationally efficient method and system for decoding shortened cyclic codes is presented. The increase in computational efficiency is achieved by improvement of the syndrome calculation step. Two embodiments of the present invention are described; the first embodiment is optimized for a hardware implementation and the second embodiment is optimized for a Digital Signal Processor (DSP) implementation. The present invention is applicable to decoding of all the binary shortened cyclic codes, including Fire codes used for Coding Scheme-1 (CS-1) for GSM.

Abstract: The disclosed invention provides a method, a system and a computer program product for the maximum likelihood sequence estimation of transmitted MSK symbols. The disclosed invention provides a set of optimizations of the Viterbi algorithm for equalizing MSK symbols. The transmitted MSK symbols are alternately real and imaginary. Therefore, based on whether the transmitted MSK symbol is real or imaginary, the disclosed invention divides the set of Viterbi states into two sets of states. The disclosed invention obtains the surviving path only for the first set of states at stages corresponding to real transmitted symbols. A real hypothesis is used to obtain the surviving paths for the first set of states. The disclosed invention also obtains the surviving path only for the second set of states at stages corresponding to imaginary transmitted symbols. An imaginary hypothesis is used to obtain the surviving paths of the second set of states.