Rice Wireless

Permanent URI for this collection

https://hdl.handle.net/1911/21945
Formerly the Center for Multimedia Communications, Rice Wireless is part of the university's Electrical and Computer Engineering Department. More information about the group can be found at http://wireless.rice.edu/.

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Browsing Rice Wireless by Author "Baraniuk, Richard G."

Now showing 1 - 12 of 12
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    DSP Education At Rice University
    (2003-09-01) Frantz, Patrick; Choi, Hyeokho; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    Rice University has a decades-long tradition of both digital signal processing (DSP) research and education, beginning in 1968. Since that time, Rice University has become a world leader and continued to be a pioneer in the DSP field. This paper will focus on the following three areas of activity at Rice. First, a brief history of DSP education and research at Rice will be presented, along with the current state of DSP research and education (Section 2). Second, a DSP Lab course will be presented, which utilizes Riceâ s Texas Instruments Elite DSP Laboratory and the C6x series of DSPs to educate students in the practical art of DSP (Section 3). This course is a 1-semester long series of labs, with a larger DSP project to be completed at the end of the course. Third, a brief overview of the Connexions project will be given, a tool originally developed to advance DSP education at Rice and other institutions (Sections 4 - 8). Connexions is a collaborative, community-driven approach to authoring, teaching, and learning that seeks to provide a cohesive body of high-quality educational content to anyone in the world, for free.
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    Edge Localized Image Sharpening via Reassignment with Application to Computed Tomography
    (2000-07-01) Dorney, Timothy D.; Bhashyam, Srikrishna; Doran, Andrew; Choi, Hyeokho; Flandrin, Patrick; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    Traditional filtering methods operate on the entire signal or image. In some applications, however, errors are concentrated in specific regions or features. A prime example is images generated using computed tomography. Practical implementations limit the amount of high frequency content in the reconstructed image, and consequently, edges are blurred. We introduce a new post-reconstruction edge enhancement algorithm, based on the reassignment principle and wavelets, that localizes its sharpening exclusively to edge features. Our method enhances edges without disturbing the low frequency textural details.
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    Imaging with Terahertz Pulses
    (2000-07-01) Dorney, Timothy D.; Johnson, Jon L.; Mittleman, Daniel M.; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    Recently, a real-time imaging system based on terahertz (THz) time-domain spectroscopy has been developed. This technique offers a range of unique imaging modalities due to the broad bandwidth, sub-picosecond duration, and phase-sensitive detection of the THz pulses. This paper provides a brief introduction of the state-of-the art in THz imaging. It also focuses on expanding the potential of this new and exciting field through two major efforts. The first concentrates on improving the experimental sensitivity of the system. We are exploring an interferometric arrangement to provide a background-free reflection imaging geometry. The second applies novel digital signal processing algorithms to extract useful information from the THz pulses. The possibility exists to combine spectroscopic characterization and/or identification with pixel-by-pixel imaging. We describe a new parameterization algorithm for both high and low refractive index materials.
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    Multifractal Cross-Traffic Estimation
    (2000-09-01) Ribeiro, Vinay Joseph; Coates, Mark J.; Riedi, Rudolf H.; Sarvotham, Shriram; Hendricks, Brent; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/)
    In this paper we develop a novel model-based technique, the Delphi algorithm, for inferring the instantaneous volume of competing cross-traffic across an end-to-end path. By using only end-to-end measurements, Delphi avoids the need for data collection within the Internet. Unique to the algorithm is an efficient exponentially spaced probing packet train and a parsimonious multifractal parametric model for the cross-traffic that captures its multiscale statistical properties (including long-range dependence) and queuing behavior. The algorithm is adaptive; it requires no a priori traffic statistics and effectively tracks changes in network conditions. NS (network simulator) experiments reveal that Delphi gives accurate ross-traffic estimates for higher link utilization levels while at lower utilizations it over-estimates the cross-traffic. Also, when Delphi's single bottleneck assumption does not hold it over-estimates the cross-traffic.
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    A Multifractal Wavelet Model with Application to Network Traffic
    (1999-04-01) Riedi, Rudolf H.; Crouse, Matthew; Ribeiro, Vinay Joseph; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/)
    In this paper, we develop a new multiscale modeling framework for characterizing positive-valued data with long-range-dependent correlations (1/f noise). Using the Haar wavelet transform and a special multiplicative structure on the wavelet and scaling coefficients to ensure positive results, the model provides a rapid O(N) cascade algorithm for synthesizing N-point data sets. We study both the second-order and multifractal properties of the model, the latter after a tutorial overview of multifractal analysis. We derive a scheme for matching the model to real data observations and, to demonstrate its effectiveness, apply the model to network traffic synthesis. The flexibility and accuracy of the model and fitting procedure result in a close fit to the real data statistics (variance-time plots and moment scaling) and queuing behavior. Although for illustrative purposes we focus on applications in network traffic modeling, the multifractal wavelet model could be useful in a number of other areas involving positive data, including image processing, finance, and geophysics.
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    Multiscale Nature of Network Traffic
    (2002-05-01) Abry, Patrice; Baraniuk, Richard G.; Flandrin, Patrick; Riedi, Rudolf H.; Veitch, Darryl; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    The complexity and richness of telecommunications traffic is such that one may despair to find any regularity or explanatory principles. Nonetheless, the discovery of scaling behavior in tele-traffic has provided hope that parsimonious models can be found. The statistics of scaling behavior present many challenges, especially in non-stationary environments. In this paper, we overview the state of the art in this area, focusing on the capabilities of the wavelet transform as a key tool for unravelling the mysteries of traffic statistics and dynamics.
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    Optimal Signaling Strategies for Symmetric and Asymmetric Bit-Rate Communication Services in the Presence of Crosstalk
    (1999-01-15) Gaikwad, Rohit; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    We have invented a new modem technology for transmitting data on conventional telephone lines (twisted pairs) at high speeds. This discovery is timely, as new standards are being developed for this Digital Subscriber Line (DSL) technology at this very moment. The potential market for the new modem technology is massive, as the telephone service providers wish to offer Internet access to the masses using the current phone lines into the home. Key to the deployment of any new service is the distribution of power over frequency, for new services must be designed to be robust to interference that might be caused by other services that are carried by neighboring telephone lines. As well, new services cannot interfere with existing services. We have made two discoveries. The first is an optimization technique that provides the best possible distribution of power (over frequency) for any new DSL service given the interference from other known services that are carried by neighboring telephone lines in the same cable. The second is a power istribution scheme that minimizes the interference caused by the new DSL service into neighboring lines. This new modem technology can be applied to many channels besides the telephone channel (for example, coaxial cables, power lines, wireless channels, and telemetry cables used in geophysical well-logging tools).
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    Optimal Transmit Spectra for Communication in the Presence of Crosstalk
    (1999-06-01) Gaikwad, Rohit; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    This paper presents a general framework for designing optimal transmit spectra for symmetric bit-rate communication services dominated by crosstalk, in particular Digital Subscriber Line (DSL) services such as the proposed HDSL2. Using the channel, noise, and interference transfer functions, we set up and solve an optimization problem to maximize the joint capacity of neighboring lines. Joint signaling techniques and optimal power distribution yield significant gains in bit rates (or performance margins) over current schemes. Furthermore, by design, the spectra are spectrally compatible with existing neighboring services. The framework is quite general --- it does not depend on the exact choice of modulation scheme, for example. It is also extremely simple and of low computational complexity.
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    PathChirp: Efficient Available Bandwidth Estimation for Network Paths
    (2003-04-01) Ribeiro, Vinay Joseph; Riedi, Rudolf H.; Baraniuk, Richard G.; Navratil, Jiri; Cottrell, Les; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    This paper presents PathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of "self-induced congestion," PathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing rate within each chirp, PathChirp obtains a rich set of information from which to dynamically estimate the available bandwidth. Since it uses only packet interarrival times for estimation, PathChirp does not require synchronous nor highly stable clocks at the sender and receiver. We test PathChirp with simulations and Internet experiments and find that it provides good estimates of the available bandwidth while using up to an order-of-magnitude fewer bytes than current state-of-the-art techniques.
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    Quantization of Sparse Representations
    (2007-01-16) Boufounos, Petros T.; Baraniuk, Richard G.
    Compressive sensing (CS) is a new signal acquisition technique for sparse and compressible signals. Rather than uniformly sampling the signal, CS computes inner products with randomized basis functions; the signal is then recovered by a convex optimization. Random CS measurements are universal in the sense that the same acquisition system is sufficient for signals sparse in any representation. This paper examines the effect of quanitization of CS measurements. A careful study of stictly sparse, power-limited signals concludes that CS with scalar quantization does not use its allocated rate efficiently. The inefficiency, which is quantified, can be interpreted as the price that must be paid for the universality of the encoding system. The results in this paper complement and extend recent results on the quantization of compressive sensing measurements of compressible signals.
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    Recent Advances in Terahertz Imaging
    (1999-06-01) Koch, Martin; Rudd, J. Van; Neelamani, Ramesh; Gupta, Maya; Baraniuk, Richard G.; Mittleman, Daniel M.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    We review recent progress in the field of terahertz "T-ray" imaging. This relatively new imaging technique, based on terahertz time-domain spectroscopy, has the potential to be the first portable far-infared imagin spectrometer. We give several examples whcih illustrate the possible applications of this technology, using both the amplitude and phase information contained in the THz waveforms. We desribe the latest results in tomographic imaging, in which waveforms reflected from an object can be used to form a three-dimensional representation. Advanced signal processing tools are exploted for the purpose of extracting tomographic results, including spectroscopic information about each reflecting layer of a sample. We also describe the applicatoin of optical near-field techniques to the THz imaging system. Substantial improvements in teh spatial resolution are demonstrated.
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    Spectral Optimization for Communication in the Presence of Crosstalk
    (1999-03-01) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)
    This paper presents a general framework for designing optimal transmit spectra for communication services dominated by crosstalk --- for example Digital Subscriber Lines (DSLs) and wireless LANs. Using the channel, noise, and interference transfer functions, we set up and solve an optimization problem to maximize the joint channel capacity. We employ joint signaling techniques and optimal power distribution to yield significant gains in bit rates (or performance margins). Furthermore, by design, the spectra are spectrally compatible with existing neighboring services. The framework is quite general; it does not depend on the exact choice of the modulation scheme, for example. It is also extremely simple and of low computational complexity.