RITE Site Project Descriptions: Summer 2002
1.
Investigation of Error Propagation in the V.34 Precoding System
Prof. S. Tretter
The ITU-T V.34 Recommendation for telephone line modems specifies a nonlinear precoding scheme in the transmitter, as well as an inverse precoder in the receiver in order to whiten and reduce the power of the noise component of the received signal at the input to the Viterbi trellis decoder in the receiver. The receiver trains a 4-tap FIR adaptive prediction error filter during the initial handshake to whiten the noise and then sends the tap values to the transmitter. The noise power reduction resulting from the prediction process is called the prediction gain and becomes significant for severe channels. The inverse precoder in the receiver assumes that the Viterbi decoder makes no symbol decision errors. Attempts at exact mathematical analysis of propagation effects when decision errors occur have been unsuccessful. The difficulties arise because of the nonlinear nature of the system. There are no published results on the effects of this phenomenon. Students will investigate the error propagation effects through simulation using a high level language like C or with MATLAB.
2.
Wireless Communication over Fading Channels with Side Information
Prof. P. Narayan
There are a variety of situations in which the transmitters and receivers in a communication system must operate without a complete knowledge of the probability law which governs the channel over which transmission occurs. This can happen, for instance, in mobile wireless communication where owing to the mobility of the users, the degradation of the transmitted signals due to multipath, shadowing and propagation losses, is time-varying. This time-varying behavior of the channel probability law is typically described in terms of the evolution of an underlying channel ``state" which describes the ``condition" of the channel. The channel state, e.g., the degree of fading, can often be measured or estimated, and varying extents of channel state information (CSI) provided to the transmitters and receivers. A key objective of our work is to study how CSI can be gainfully used in devising transmitter and receiver strategies so as to enable reliable and efficient communication. Two models are of particular interest in the context of wireless communication. The first model concerns the uplink of a mobile wireless channel with multiple (mobile) senders transmitting to a single (base-station) receiver. The objective is to determine transmitter/receiver structures, including channel-access strategies and encoding/decoding schemes, for reliable and efficient communication. The second model considers the downlink of a mobile wireless channel with a single (base-station) sender transmitting receiver-specific as well as common information in a broadcast mode to multiple (mobile) receivers. The base-station is equipped with multiple antennae. The tasks for MERIT students to perform are: (1) Understand the (theoretical) models mentioned above, and (2) Conduct numerical studies for assessment of system performance (e.g., throughput) for various statistical models of the channel fade.
3.
DSP Implementation of Communications Systems
Prof. J. Gansman
The goal of this project is to implement and design communication systems using DSP processors. The computing power of embedded processors has grown so dramatically that soon the entire transceiver can be programmed in such a device. The following are two project examples. V.22bis QAM Modem: The ITU-T V.22bis modem transmits at 2400 bits per second by using a 16-QAM constellation (4 bits per symbol) and 600 symbols per second. Students will make a full duplex modem by implementing the transmitter and receiver on a single C6701 DSP. After studying the modem standard, students will need to learn about pulse shape design, adaptive equalization, carrier synchronization, and symbol timing recovery. Software Radio: It is becoming increasingly important for real-world communications systems to have software configurable modulation schemes to permit flexibility. Students will explore this concept by researching various analog modulation schemes and implementing an analog software radio in full duplex mode. The transmitter will be software selectable between Large Carrier AM, DSB AM, and FM. The receiver will determine the modulation scheme from the received signal.
4.
Testbed-Based Simulation and Evaluation of Pseudochaotic Signaling over
Wireless Channels
Prof. B. Papadopoulos
We plan to encourage the involvement of undergraduates in research at the physical-layer of wireless communication systems. Undergraduate students can greatly contribute at the implementation stage of wireless communication systems, while at the same time obtaining a first-hand exposure to various aspects of these systems, such as the effects of RF impairments, thermal and quantization noise, channel and multi-user distortion, synchronization, coding, and BER performance characteristics. The project can thereby serve as a prelude for motivating communication theory and modeling, and provide a glimpse of some of the important research problems in the area. Such implementation-based physical-layer projects would draw upon some of the resources of the Indoor Wireless Lab, emanated from an NSF funded initiative in the form of a senior level design class, whereby the students over a period of two years built a working prototype of the IS-54 standard. The projects will involve exploiting the available hardware of the Indoor Wireless Lab, and in particular, programming the DSPs on the available testbeds to perform proof -of-concept simulation of novel signaling schemes. One such sample project involves the implementation and evaluation of a pseudochaotic signaling system on a wireless testbed. The undergraduate student's initial task amounts to implementing on a DSP an uncoded version of the pseudochaotic signaling scheme, whereby a digital symbol stream is modulated on a pseudochaotic waveform. Such a signal is generated by propagating an initial condition through the dynamics of a one-dimensional pseudochaotic mapping. Besides being involved at the implementation stage of the algorithm, the student would have to verify via lab testing the performance characteristics (developed by graduate students in our group) of intended and unintended receivers over indoor fading channels, as well as the tradeoffs between key length (side information at the intended receiver) and security. Naturally, such a project can provide an effective exposition not only to aspects of reliable communication over fading channels, but also to information-theoretic security and chaotic dynamical systems.
5.
Coding and Modulation for Wireless
Networks
Prof. R. Liu
Coding and modulation designs that take advantage of the use of multiple antennas for transmit diversity are essential for robust wireless communications. Space-Time codes for different modulation and demodulation formats, as well as iterative signal processing for the receivers of wireless communications systems, are examined with fading multipath channels and interference from other users or jammers being present. The applications include cellular, PCS, fixed wireless and satellite networks. The demodulation and decoding process of the space-time coded signals is also coupled with iterative interference cancellation or suppression for additional advantage. When receiver feedback is available at the transmitter adaptive modulation and FEC coding as well as adaptive power allocation across subcarriers are also studied. We will also propose a systematic code construction method that jointly considers diversity advantage and coding advantage for an arbitrary number of transmit antennas and any memoryless constellation. In all scenarios, detailed simulations (in C and Matlab) of all blocks of the transmitter and the communications channel are developed and performance results and tradeoffs are generated. Undergraduate students will be involved in these simulations and work under the guidance of graduate students (GRAs).
6.
Opto-Impulse Radio for High Data Rate Wireless Communications
Prof. C. Lee
The objective of this research is to achieve high information data rate (multi-Mbs/s to Gbs/s) wireless communications with low probability of detection (LPD) and low probability of interception (LPI). The approach employed is the ultra-wideband impulse radio using optoelectronic technique. The innovation includes the use of picosecond semiconductor lasers and ultrafast photoconductive switches for impulse generation and reception. We refer this new technology as opto-impulse radio. We expect that opto-impulse radio will revolutionize wireless communications with quantum jump in system performance. The proposed research for the RITE students covers only hardware related issues. Students will be asked to set-up and demonstrate a simple opto-impulse radio system.
7.
Resource Allocation for Wireless
Communication Networks
Prof. A. Ephremides
and Prof. S. Ulukus
The number of wireless data customers as well as their demand for higher and higher data rates have made efficient allocation of resources of paramount importance. One important characteristic of wireless communication networks that distinguishes them from wired networks is that in wireless communication networks the transmissions of multiple users take place in the same fixed frequency bandwidth, that is, users' communications interact with each other through unintentional interference they create for each other. A main thrust of this project is in the allocation of physical layer resources to a network of mobile users (terminals) communicating with fixed information sources (base stations in cellular wireless networks) and investigations of energy-aware, energy-efficient, and energy-constrained wireless networking. The controllable resources in the physical layer are transmit powers, transmit waveforms, number of parallel transmissions, modulation constellation sizes, error correction coding mechanisms, and receiver filters of the users. The individual or joint optimum selection of these resources for individuals or networks of users has been an important research issue. The research typically involves mathematical modeling of the particular problem, solving it, and ultimately coming up with distributed algorithms to implement the solution. This area of research is very versatile in terms of finding research problems for undergraduate students with various backgrounds. Depending on the problem formulation (e.g., the set of resources considered, and system and implementation constraints), one can come up with problems with varying degrees of difficulty, and involving varying amounts of mathematical analysis and practical implementation aspects. We expect that selected undergraduates will work together with graduate research assistants under faculty supervision to contribute to these tasks.
8.
Simulation in Communication Networks
Prof. A. Makowski
Today's computer communication networks have become very large in size, provide service to a huge number of users, encompass a vast array of technologies and operate under a large number of protocol stacks with sometimes very dissimilar objectives. Over the past two decades, it has become increasingly clear that sophisticated software simulation tools are needed in order to develop good network designs, predict user performance and plan network evolution in the face of rapid traffic growth, catastrophic network failures, and the introduction of new technologies. Such software tools have been developed and are used widely in industry as they provide predictive modeling and often lead to a more comprehensive understanding of networking technologies. With this in mind, we propose to organize a number of simulation projects using two network simulators, namely OPNET which has become the de-facto standard throughout industry and government, and the discrete event simulator Ns targeted at networking research [http://www.isi.edu/nsnam/ns]. OPNET provides software solutions to optimize the performance and to maximize the availability of communications networks and applications; it integrates a suite of software tools, provides an extensive library of models across a large number of technologies, written in collaboration with vendors and manufacturers. On the other hand, Ns began as a variant of the REAL network simulator in 1989 and has evolved substantially over the past few years. It has always included substantial contributions from other researchers - it is not a polished and finished product, but the result of an on-going effort of research. Ns provides substantial support for simulation of TCP, routing, and multicast protocols over wired and wireless (local and satellite) networks. Possible topics include (but are not limited to) routing in wireless networks, generating self-similar traffic for OPNET and Ns simulations, traffic scheduling in wireless networks, self-organizing networks, modeling IP over ATM, the performance of TCP under RED gateways, source traffic modeling, QoS in cellular networks, simulation models for MPLS traffic engineering, performance of ATM switches, modeling satellite networks, etc. Such projects will provide the undegraduate students with the opportunity (1) to become familiar with simulation techniques and concepts, (2) to become proficient in the use of commercially available software packages, and (3) to develop of a better understanding of the concepts and implementations behind some key networking technologies.
9.
Wireless Transmission Control Protocol
Prof. R. La
With the deployment of 2G/3G wireless systems, such as GPRS, EDGE, and CDMA2000, it is becoming more crucial to be able to understand and accurately model the impact of various delays on Transmission Control Protocol (TCP) performance. For instance, in order to better utilize the wireless resources, wireless systems dynamically set up and tear down connections, e.g. Temporary Block Flow in GPRS. This requires that the mobile first requests a connection set up whenever it has data to transmit on the uplink. This may introduce a significant, variable delay in TCP round trip measurement and acknowledgement (ACK) compression over the air interface. Further, additional delay may be introduced between Servicing GPRS Support Node (SGSN) and Packet Control Unit (PCU) in GRPS system or SGSN and Radio Network Controller (RNC) in UMTS system due to vendor specific implementation of flow control mechanism. It has been observed that widely varying round trip delays can have a significant impact on the end-to-end performance of TCP. Hence, analyzing the performance of TCP over various wireless technologies is important for efficient network resource management. This problem has several different aspects, each of which can be isolated and studied separately. For example, the impact of connection set up delay can be studied independently of other aspects, while the impact of buffer sizes at SGSN and PCU or RNC and the flow mechanism between them can be studied separately. These problems should be suitable for undergraduate projects.
10.
Defending Against Distributed Denial of Service Attacks in the Internet
Prof. M. Shayman
There have been a number of widely publicized denial of service attacks against Internet web servers. These attacks deny access to legitimate users, are costly to electronic commerce, and pose a national security risk. Current mechanisms are inadequate to defend against this threat. The problem is difficult for several reasons: (1) many sources may be involved in sending attack traffic; (2) the machines sending attack packets may be remotely controlled by the perpetrators of the attack; (3) the machines sending attack packets may be obscured by address spoofing--falsifying the source address field in the packets; (4) the attack traffic emanating from any one machine may be very light if the attack sources are widely distributed; (5) sophisticated attackers can create attack traffic that is statistically similar to legitimate traffic. In this project, we will develop mechanisms to detect denial of service attacks that can be implemented in individual routers as well as algorithms to filter and discard suspected traffic when an attack is detected. We will also develop mechanisms to facilitate coordinated actions by groups of routers. The students will contribute to the project by preparing and performing network simulations. It is also expected that they will interact with the industrial partners in this project, Boeing and NAI Labs.
11.
Multimedia Security for Networks and Wireless Communications
Prof. M. Wu and Prof.
R. Liu
Internet and wireless networks offer ubiquitous channels to deliver and to exchange multimedia information. However, the digital advantages offered by the information technology era cannot be fully deployed without guarantees on the security and protection of multimedia data. Both encryption and data embedding are promising mechanisms for such protection. The projects suitable for undergraduate students include not only the design and implementation of elements in multimedia encryption and data embedding systems, but also testing and security evaluation (sometimes through attacks). One project would be to explore and evaluate candidate elementary encryption operations on multimedia data that are computationally effective and are easily compatible with lossy compression and lossy communications. Another project would be to design and implement a software testbed of multimedia data hiding, which will enable the easy reuse of common modules and will allow the investigation for each specific data hiding design problem to focus on critical modules. Information security often involves design and analysis. College students are one group of the stereotype hackers portrayed by the media to attack security systems. Such hacking has brought about many interesting ethical discussions that are important for engineering undergraduates to be aware of. What's more, the technical community has gradually recognized that the design and the analysis (often in the form of attacks) are equally important in the research and commercialization of information security. In view of the equal importance of the design and the analysis for information security systems, the security projects for undergraduates would also involve elements of attacks and analysis. It not only helps to improve our security designs, but also provides a valuable opportunity for the students to give their thinking on ethical issues, including the technical as well as the social impact of their works.
12.
Computer Recognition of Faces
Prof. R. Chellappa
Computer recognition of faces has applications in access control, ATM machines and in human/computer interfaces. In the project, the student(s) will develop global principal component analysis/linear discriminant analysis or feature-based approaches for verifying the presence/absence of a human and then determine the human's gender, identity and emotions. Using images acquired by a camera mounted on a PC, the algorithms will be able to produce an electronic log of the human's arrival/departure record. Emphasis will be placed on real-time implementations of existing algorithms in Professor Chellappa's group.
13.
Automatic Speaker-Independent Speech Recognition
Prof. C. Espy-Wilson
There is an increasing demand for automatic speaker-independent speech recognition solutions for desktops and wireless handheld devices. The latter application places serious constraint on the available memory. The development of accurate, efficient, robust and speaker-independent digital signal processing algorithms for speech recognition is the subject of intensive on-going research in the Department. Many of the research activities involved, such as the evaluation of algorithms across different databases and the development of fast algorithms, are suitable projects for undergraduate students. Typical subprojects include the conversion of MATLAB code into C, the evaluation and comparison of different algorithms in the various components of the recognition system, and the application of these algorithms on environmental sounds to see how well they are characterized and distinguished from speech.
14.
GPS-Based Location Determination
Prof. P. S. Krishnaprasad
GPS (global positioning laboratory) represents a remarkable integration of several major advances in the field of electrical engineering-from satellite communication, coding, estimation of signals in noise, to real-time signal processing via fast, low power circuitry on portable devices--providing us the capability to determine with increasing precision and accuracy, the location and speed of a GPS-equipped platform practically anywhere on earth. It is expected that initially, work in the proposed project would emphasize a view of the integration of subject matter inherent to GPS, demonstrating how systems concepts, such as filtering algorithms (e.g., Kalman filters and various nonlinear filters), mathematical descriptions of orbital mechanics of satellites, and differential or interferometric techniques, and phase tracking techniques contribute to the advances in precision and accuracy achievable via GPS. The project will also provide opportunities for studying applications of GPS to motion control, and in this context also investigate integration of a variety of other sensor technologies (e.g., inertial and optical/acoustic proximity sensors) with GPS for this purpose. It is expected that initially, work in the proposed project would emphasize a view of the integration of subject matter inherent to GPS, demonstrating how systems concepts, such as filtering algorithms (e.g., Kalman filters and various nonlinear filters), mathematical descriptions of orbital mechanics of satellites, differential or interferometric techniques, and phase tracking techniques contribute to the advances in precision and accuracy achievable via GPS. The project will also provide opportunities for studying applications of GPS to motion control, and in this context also investigate integration of a variety of other sensor technologies with GPS for this purpose. Students selected under the RITE site program will be able to pursue software development in this arena (with interesting challenges in integer optimization for phase ambiguity resolution, cycle slip detection and mode switching in satellite tracking). A primary goal of the project will be for students to learn the principles and carry out implementations of motion determination algorithms based on filtering and estimation theory and gain a better appreciation of issues in signal processing influenced by noise characteristics associated to the GPS system.
15.
Neuromorphic Signal Processing
Prof. S. Shamma,
Prof. R. Etienne-Cummings, Prof.
J. Simon, Prof. P. Abshire
Neuromorphic engineering is a novel direction in Bioengineering that is based on the design and fabrication of artificial neural systems, such as vision chips, head-eye systems, auditory processors, and autonomous robots, whose physical architecture and design principles are based on those of biological nervous systems. The last decade has witnessed major advances in the theory of neurally inspired signal processing and its hardware implementation in analog and digital VLSI. Most significant has been the appreciation that biological sensory and motor systems offer novel ideas on how to construct machines that exhibit robust, sensitive, and adaptive behaviors, and even potentially complex cognitive abilities. The research that underlies this young field is truly diverse. It ranges from the purely theoretical studies of computational complexity and learning algorithms, to the highly applied image and speech understanding systems. Research activities in the department cover much of this wide spectrum of interests. They include the formulation of auditory algorithms for speech and music recognition and understanding, the design of echolocation systems mimicking the bat ultrasound, the exploration, modeling and analysis of the brain's sensory processing systems, and the detailed modeling of sound localization abilities of the barn owl. Many components of this research activity, such as real-time implementation of algorithms on DSP chips and development of analog VLSI circuits, testing them, and integrating them within bigger systems, are suitable projects for undergraduate students. In addition, this collection of projects lends itself to robotic implementations, especially with autonomous vehicles, projects that are especially suitable for a group effort where the integration of multiple modalities and technologies is necessary. The summer students will use custom chips that have been developed in the labs and integrate them into a demonstration systems. Various algorithms for image processing will be implemented using these systems. We expect the students to be exposed to a wide range of engineering concepts, ranging from analog and digital signal processing to hardware realization of image processing algorithms. The results may be published at conferences and/or in technical journals. The technical and communicational skills of the students will be enhanced by exposing them to high-level research, requiring written technical papers/reports and oral presentations.