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Current Research

• Allpass Filters in Vocoders
  A discussion of the use of all-pass filters in Vocoders.
  
  
• Stochastic Resonance of Binary Signals
  A discussion of how Stochastic Resonance (SR) can be used to clean and enhance a noisy binary signal.
  
  
• Multicast and Unicast Streaming Media
  A discussion of the differences between unicast and multicast transmission of multimedia.
  
  
• Dynamic Directional RTS/CTS
  A beamforming based addition to the RTS/CTS protocol which can improve overall network throughput.
  
  
• 802.11 Authentication and Association
  A description of the Authentication and Association Procedures in 802.11.
  
  
• Model-Based Speech Enhancement
  Maintaining harmonic information will improve the overall speech quality when compared to standard noise reduction techniques.
  
  
• Acoustic Echo Cancellation (AEC) for Commercially Available Off-the-Shelf (OTS) Hardware
  VOCAL has an ubiquitous acoustic echo cancellation solution for all operating systems and processors.
  
  
• Non-conventional Applications of Acoustic Echo Cancellation (AEC)
  VOCAL has an ubiquitous acoustic echo cancellation solution for all operating systems and processors.
  
  
• Windowing in Vocoders to Remove Artifacts
  A discussion of the use of Windowing functions to smooth discontinuities and remove audio artifacts.
  
  
• Stochastic Resonance of Analog and Digital Signals
  A discussion of Stochastic Resonance (SR) being applied to Analog and Digital Signals.
  
  
• VoIP Stack Featuring Voice Quality Enhancement (VQE)
  VOCAL's VoIP stack includes, speech coders, RTP, SIP and features such as voice quality enhancement modules can be added.
  
  
• Maintaining the Harmonic Structures for Speech Enhancement
  Maintaining harmonic information will improve the overall speech quality when compared to standard noise reduction techniques.
  
  
• Comfort Noise Generation in Vocoders
  A description of Comfort Noise Generation (CNG) in Speech Coding.
  
  
• Packet Loss Concealment (PLC) in Vocoders
  A description of Packet Loss Concealment in Vocoders.
  
  
• Psychoacoustic Noise Suppression
  Psychoacoustic noise suppression takes into account the physiological and acoustic properties of the human hearing organ into the design of the algorithm for improving the perceptual quality of the communication.
  
  
• SILK
  A description of the SILK codec.
  
  
• Measuring Speech Quality
  Subjective listening tests are preferred, but they are not always feasible and objective tests that attempt to predict how users will evaluate the speech quality is required.
  
  
• Echo Reduction in Coding
  Transform coding in audio and voice can introduce artifacts called pre/post echoes.
  
  
• The Cause of Echoes in Coding
  Transform coding in audio and voice can introduce artifacts called pre/post echoes.
  
  
• Arithmetic Coding in Vocoders
  A description of Arithmetic Coding as it applies to Voice Coding.
  
  
• Battlefield Voice Activated Transmission (VOX)
  Voice Activated Transmission is commonly used in radio communications in which push-to-talk is either inconvenient or not practical, thus hands-free communication is required.
  
  
• The Applications of Voice Activity Detection (VAD)
  Voice Activity Detectors (VAD) play a major role in the telecommunications and speech processing applications.
  
  
• Implementing Stochastic Resonance in Discrete Time
  An implementation of Stochastic resonance for a disrete time signal is presented based on cascading filters and a fourth order Runge-Kutta approximation.
  
  
• Stability of LPC Filters in Vocoders
  A description of algorithms used to ensure stability of Linear Predictive Coding (LPC) filters in Speech Coders.
  
  
• Standard Methods of Voice Activity Detection (VAD)
  Voice Activity Detectors (VAD) play a major role in the telecommunications and speech processing applications.
  
  
• Wideband Energy Detection in Scalable Speech Coding
  An algorithm is presented for determining if speech sampled at Wideband rates should be downsampled to narrowband rates.
  
  
• Session Initialization Protocol (SIP) and Deep Packet Inspection (DPI)
  For VoIP sessions, DPI of SIP will be important for monitoring scenarios such as session re-negotiations and call forwarding.
  
  
• Efficient Implementation of LPC Analysis Filters
  An efficient algorithm for performing a LPC analysis filter is presented.
  
  
• Speech Enhancement and Speech Intelligibility
  Speech enhancement may improve the perceptual speech quality, it does not guarantee an improvement in speech intelligibility.
  
  
• Adapting Particle Swarm Optimization (PSO) by Deciding on the State of Convergence
  An algorithm is presented for deciding on the state of convergence of PSO and, based on this, adapting its parameters apropriately.
  
  
• Compressed Sensing for Error Protection in JPWL
  Compressed sensing techniques are examined as an alternative for Reed-Solomon error correction within the JPWL framework.
  
  
• Exploiting Spacial Diversity in Single Antenna Systems using Cooperative Communications Cancellation
  Cooperative communications is the technique of using relay nodes to take advantage of spacial diversity on devices that are too small for multiple antennas.
  
  
• Lawful Interception of VoIP Traffic at an Internet Service Provider
  Lawful Intercept is the interception of data through a network as authorized by a law enforcement agency. This describes the basic structure as it would be implemented by an internet service provider.
  
  
• Cross-Correlations in Echo Cancellation
  The cross-correlation between various signal components can be revealing to the state of the echo canceller.
  
  
• Echo Cancellation in IP Networks
  The implementation of Voice over IP (VoIP) networks, presents a new set of challenges in optimizing the voice quality and providing the expected toll quality.
  
  
• Enhanced Security Based on Under-Determination in Compressed Sensing
  We present a feature of the technique of joint compression and encryption by compressed sensing. This feature makes messages encoded in this way more secure than messages secured by standard methods.
  
  
• Error Correction Using Compressed Sensing Techniques
  Compressed sensing is a technique where a sparse signal can be undersampled and reconstructed using convex minimization techniques. We show how compressed sensing techniques can be used as a forward error correction scheme.
  
  
• JPEG2000 Image Transmission using JPIP
  The scalable properties of JPEG2000 interactivity protocol (JPIP) are discussed. Some applications such as medical applications or image access on restricted devices is explored.
  
  
• Stochastic Resonance
  A description of the phenomenon of Stochastic Resonance and its application in Signal Processing
  
  
• Weak Signal Detection using Particle Swarm Optimization (PSO) and Stochastic Resonance (SR)
  A Particle Swarm based algorithm for tuning of Stochastic Resonance.
  
  
• Estimating Echo Return Loss and Echo Return Loss Enhancement
  To achieve an ubiquitous solution for an acoustic echo cancellation system, a control system for the adaptive filter for the echo canceller and the post-filter is required.
  
  
• Gradient Projection Reconstruction of Compressed Sensing Signals
  A gradient projection algorithm is introduced with the intention of decreasing the computational complexity of the compressed sensing reconstruction problem.
  
  
• Particle Swarm Optimization (PSO) in Signal Separation
  A PSO based algorithm for reducing noise in speech signals based upon optimizing the effects of a Singular Value Decomposition.
  
  
• Statistical Joint Control of Acoustic Echo Canceller and Post-Filter
  Based on the statistical properties of the adaptive filter of the echo canceller, the step-size and the post-filter can be controlled jointly.
  
  
• Wireless JPEG2000 Transmission and Unequal Error Protection using JPWL
  The JPWL standard is introduced. The header protection and unequal error protection capabilities of the standard are examined.
  
  
• Compressed Sensing in JPSEC
  Compressed sensing (CS) can be used as the encryption mechanism within the JPSEC protocol. The inherent properties of CS allow for some desirable properties within an image encryption scheme.
  
  
• Echo Control on Codec Parameters
  This direct modification of the codec parameters provides low complexity solution to voice quality enhancement in cellular networks.
  
  
• Euclidean Particle Swarm Optimization (EPSO)
  A PSO based algorithm that uses Euclidean distance as a measure of convergence to help prevent convergence to a local minima.
  
  
• Secrecy of Cryptography With Compressed Sensing
  The secrecy of images encoded using compressed sensing is examined. The standard deviation of the guessed sampling matrix is calculated and the impact this has on the security of the image is explored.
  
  
• Echo Cancellation in Cellular Networks
  There are several cellular network architectures which influence the implementation of an echo canceller.
  
  
• Overview of Encryption of Compressed Sensed Images
  Compressed sensing (CS) as an image encryption mechanism is explored.
  
  
• Adaptive Particle Swarm Optimization (APSO)
  A modification of PSO that is designed to deal with real time changing data by reevaluating particles to test for changes.
  
  
• The Combined Reduction of Echo and Noise
  Tackling noise reduction and residual echo reduction in a joint effort.
  
  
• Secure JPEG2000 (JPSEC) Images
  Security in JPEG2000 is addressed by Part 8 of the ITU standard (T.807) known as JPSEC. We consider some of the possibilities of using the selective encoding of JPSEC with the scalability properties of JPEG2000.
  
  
• Dual Channel Noise Estimation for Speech Enhancement
  This dual-channel noise estimation technique is an extension of the single-channel noise estimation that uses the phase difference information.
  
  
• The Perception of Echo
  Round trip delay and bandwidth influence the perception of echoes.
  
  
• 802.11 Distributed Coordination Function (DCF)
  The basic functionality of the 802.11 distributed coordination function (DCF) is explained. Some concepts, including the hidden/exposed terminal problem and the network allocation vector, are explained in more detail.
  
  
• Gaussian Particle Swarm Optimization (GPSO)
  A PSO based algorithm using Gaussian random variables that is designed to not get caught in local minima.
  
  
• Noise Reduction using Singular Value Decomposition (SVD) and Particle Swarm Optimization (PSO)
  A PSO based algorithm for reducing noise in speech signals based upon optimizing the effects of a Singular Value Decomposition.
  
  
• Post Filtering for Residual Echo Control
  Post filtering of echo cancellation systems is important for environments with large levels of non-linear distortion.
  
  
• JPEG2000 Rate and Quality Scalability
  The scalable properties of JPEG2000 are explored including the resoltion scalability and quality scalability. It is explained how JPEG2000 uses EBCOT to accomplish this scalability.
  
  
• Network Utility Maximization (NUM) for Resource Allocation
  We introduce network utility maximization (NUM) or layering as optimized decomposition as an approach to optimizing layeres data communications networks.
  
  
• IEEE 802.11e
  An introduction to IEEE 802.11e Standard.
  
  
• IEEE 802.11n
  An introduction to IEEE 802.11n Standard.
  
  
• Variable Step-size and Regularization Parameters for NLMS
  In echo cancellation, proper control of step-size and regularization parameters of the NLMS can improve the overall performance of the system.
  
  
• Document Signature by Multiple Parties
  This page describes a method to allow multiple users to simultaneously sign a document using fax and Internet technologies. Either digital or physical signatures may be used to sign the document.
  
  
• Particle Swarm Optimization (PSO) in the Grassmannian Line Packing Problem for MIMO Beamforming
  Use of Particle Swarm Optimization to solve the Grassmannian line packing problem for the offline design of MIMO codebooks.
  
  
• Double-Talk Detection in Echo Cancellation
  The presence of the near-end talker during far-end speech is a source of disruption in the adaptation of the filter. Adaptation of the filter must be prevented via a double-talk detector.
  
  
• Frequency Offset Compensation in Echo Cancellation
  Frequency offset in echo cancellation refers to when the sampling frequency of the far-end and near-end signals are not the same.
  
  
• Wavelet Transform for Sparsity in JPEG2000
  The discrete wavelet transform (DWT) is used in the compression of images in the JPEG2000 protocol. Compared to the DCT used in the original JPEG compression, it allows for scalability and increased image quality in the compressed image.
  
  
• Networking
  Nearly every organization utilizes some form of networking to accomplish their goal. Because of the many topologies and scenarios available, it is important to properly choose the correct networking protocols to fit a given need.
  
  
• Distortion Minimizing Rate Control for Wireless Multimedia Sensor Networks
  Video transmission over wireless networks needs to be treated differently than standard data transmission. A distortion minimizing rate control (DMRC) rather than TCP can help to both maintain fairness among different streams along with keep the data rate consistant.
  
  
• Blind Signal Separation (BSS) using Particle Swarm Optimization (PSO)
  A method of designing adaptive unmixing filters for BSS by using PSO to determine optimal coefficients..
  
  
• Distortion Based Networking – Ad Hoc Wireless Routing
  When there are errors in multimedia data, these errors are able to be perceived by the end user in the form of distortion. This motivates us to choose a routing protocol based on the parameters which affect distortion such as delay and packet drops.
  
  
• Image Compression using Compressed Sensing (CS) and Particle Swarm Optimization (PSO)
  A method is described for using PSO and Compressed Sensing for image compression.
  
  
• Handling of Nonlinearities in Echo Cancellation
  Adaptive filters can only cancel the linear portions of the echo path, thus the non-linear portions cannot be removed via the adaptive filter. In this paper it will be discussed how an adaptive algorithm will react to these non-linear distortions.
  
  
• Single Pixel Camera
  A single pixel camera concept is presented. This camera allows a physical realization of a compressed sensing (CS) system, where the sampling matrix is created using a digital micromirror device (DMD).
  
  
• Frequency Domain Adaptive Filtering in Echo Cancellation
  Frequency Domain Adaptive Filters (FDAF) in acoustic echo cancellation applications provide several advantages over its time domain counterpart.
  
  
• The Artifacts of Spectral Subtraction
  An example of the artifacts of the spectral subtraction is musical noise. Musical noise are little islands of spectrum power in a signal, that appear randomly in different frequency buckets from frame to frame.
  
  
• Background Subtraction using Compressed Sensing
  Compressed sensing is used to remove the background from an image. This allows for a low complexity background subtraction algorithm which can be implemented directly at the camera for use in surveillance or motion detection.
  
  
• Compressed Sensing of Images
  Compressed sensing can be used to simplify the sampling procedure for complex imaging systems. Such systems include MRI imaging and extremely high resolution optical imaging.
  
  
• Multipath Channel Estimation with Compressed Sensing
  We propose a method for using compressed sensing (CS) to find the multipath channel coefficients in a sparse channel. The channel is sensed using a pseudo-random process and the coefficients are determined using l1 minimization techniques.
  
  
• Recovery of Audio Signals with Compressed Sensing
  A method is presented by which analog audio signals can be directly sampled and compressed using compressed sensing (CS), resulting in decreased complexity and storage requirement for sparse wideband signals.
  
  
• De-reverberation of Speech Signals
  De-reverberation attempts to model the impulse response of the acoustic environment and filter it from the received microphone signal.
  
  
• Time Delay of Arrival (TDOA) using Particle Swarm Optimization (PSO)
  An application of swarm coding to localization using time-delay of arrival.
  
  
• Particle Swarm Optimization (PSO) in Speech Enhancement
  An application of swarm coding to two-channel noise reduction..
  
  
• Interference Cancellation in Compressed Sensed Signals
  A method is presented by which, for two compressed sensed signals, a signal of interest can be separated from an interferer based on some assumptions about the signals.
  
  
• The Challenges of Stereophonic\Multichannel Echo Cancellation's
  As in all acoustic hands-free communications systems, acoustic echo cancellation is a requirement. Multichannel echo cancellation provides an additional set of signal processing challenges as compared to monophonic echo cancellation.
  
  
• Wideband Acoustic Echo Cancellation
  Acoustic echo cancellation (AEC) is a critical component of wideband audio teleconferencing. The presence of the acoustic echoes in the microphone signal cause significant degradation in the quality of conversation, thus negating the benefits of having wideband audio.
  
  
• Comparison of Facsimile Transmission over T.38 and V.152
  Procedures for fax passthough and relay are described in V.152 and T.38, respectively. Both allow existing PSTN fax machines to transmit images over the IP network, but each one has its advantages.
  
  
• Particle Swarm Optimization (PSO) in the RWA Process for All-Optical WDM Networks
  Particle Swarm Optimization is used to determine the optimal Routing and Wavelength Assignment for an all optical Wavelength Division Multiplexing network.
  
  
• Subband Acoustic Echo Cancellation
  Subband adaptive filtering overcomes many of the limitations of traditional time-domain normalized least means squares implementations of echo cancellation.
  
  
• Motion Tracking using Particle Swarm Optimization
  A Particle Swarm Optimization based algorithm for motion tracking.
  
  
• Sound Propagation Models for Beamforming
  Beamforming can be applied to array of antennas, radar and sonar transducers, and to microphones. More specifically in the field of acoustic signal processing, the speech enhancements and noise reduction benefits of microphone arrays and acoustic beamforming have many applications.
  
  
• Counter with Cipher Block Chaining-Message Authentication Code (CCM) IP Core
  Hardware/Firmware implementation of the Counter with Cipher Block Chaining-Message Authentication Code (CCM) using Advanced Encryption Standard (AES) Encryption Block. Fully functional and synthesizable VHDL CCM IP core.
  
  
• Particle Swarm Optimization in Acoustic Echo Cancellation
  Particle Swarm Optimization is used to determine the optimal IIR filter for Acoustic Echo Cancellation.
  
  
• Secure Faxing with JPSEC
  Faxing documents using Secure JPEG 2000, also referred to as JPSEC, is a method to secure image contents with stronger encryption and data integrity than what is provided by T.30.
  
  
• Monaural Speech Separation
  Speech segregation is the separation of a desired speech signal from a mix of environmental signals.
  
  
• Undetermined Blind Signal Separation
  Degenerate Unmixing Estimation Technique for Undetermined Blind Signal Separation.
  
  
• Adaptive Parity Error Detection for Compressive Imaging
  Traditional image compression is very sensitive to bit errors from a lossy channel. By using compressed sensing to compress and image, the error resiliency of an encoded image is greatly increased.
  
  
• Noise Resiliency with Compressed Sensing
  Noise Resiliency with Compressed Sensing.
  
  
• Terahertz Imaging for Security using Compressed Sensing
  Terahertz Imaging for Security using Compressed Sensing.
  
  
• Adaptive Antenna Arrays using Particle Swarm Optimization
  Adaptive Antenna Arrays using Particle Swarm Optimization.
  
  
• The Affect of Convergence Speed in the Two-Path Method
  The Affect of Convergence Speed in the Two-Path Method.
  
  
• Particle Swarm Optimization on FPGA
  Particle Swarm Optimization on FPGA.
  
  
• T.38 Image Extraction from Captured Network Data
  T.38 is one form of communication that could be used to facilitate criminal activities. Lawful interception technologies give agencies the ability to process collected criminal communications.
  
  
• Advanced Encryption Standard (AES) IP Core
  Hardware/Firmware implementation of the Advanced Encryption Standard (AES). Fully functional and synthesizable VHDL AES IP core.
  
  
• Noise Reduction (Noise Control) in Sound Capture
  An acoustic echo canceller may need to address different acoustic and noise control environment issues. Constraints include the volume of the enclosure, the required bandwidth, and the tolerable delay.
  
  
• Particle Swarm Optimization in the Design of Adaptive FIR Filters
  Particle Swarm Optimization in the Design of Adaptive FIR Filters.
  
  
• Noise Reduction of Non-stationary Noise Sources
  Noise Reduction of Non-stationary Noise Sources.
  
  
• Particle Swarm Optimization in the Design of Adaptive IIR Filters
  Particle Swarm Optimization in the Design of Adaptive IIR Filters.
  
  
• Robust Adaptive Algorithms for Echo Cancellation
  An acoustic echo canceller may need to address different acoustic and noise control environment issues. Constraints include the volume of the enclosure, the required bandwidth, and the tolerable delay.
  
  
• The Combination of Adaptive Filters
  An acoustic echo canceller may need to address different acoustic and noise control environment issues. Constraints include the volume of the enclosure, the required bandwidth, and the tolerable delay.
  
  
• Comparison of T.38 Transmission Over UDPTL or RTP
  T.38 provides two UDP-based means for transporting its data: UDPTL and RTP. While the two are used in a very similar manner, each one has its advantages over the other.
  
  
• Two-Path Method for Acoustic Echo Cancellation
  Acoustic echo cancellation (AEC) is a critical component of audio teleconferencing. In conferencing systems, the acoustic coupling between the loudspeaker and microphone is disruptive to the flow of conversation and inhibits the ability of achieving full-duplex communication. Implementation of a two-path echo canceller is a simple, but effective way to mitigate these challenges.
  
  
• Particle Swarm Optimization
  Particle Swarm Optimization.
  
  
• T.38 Transmission Over SRTP
  The T.38 standard lacks a standardized method to secure the image sent. Using SRTP to transfer T.38 data can provide one way to increase the security of T.38.
  
  
• Current Proposed Modifications to T.38
  In order to improve on evolutive compatibility and avoid confusion, T.38 must continually be updated and fixed. This document summarizes the proposed changes to T.38.
  
  
• T.38 Prioritization in a Universal Gateway
  T.38 is the most commonly implemented solution for real-time facsimile over the Internet. When implemented in a universal gateway, T.38 must compete with other types of IP traffic for resources.