iCORE Student Seminars in Communications
In late 2001, the iCORE Wireless Communications Laboratory created a student seminar series. The purpose of these seminars is the dissemination of information, ideas, and research among the graduate students in communications at the University of Alberta.
For the iCORE Student Seminars, students generally present seminars based on their research results or their upcoming conference presentations. Some students present seminars based on publications that are relevant to their research. In all cases, the iCORE Student Seminars in Communications serve as a good conduit of information for students. Besides, it's a good excuse to get students out of the lab.
Back to Student Seminars
Seminars in Winter 2003
| Time: | 3:30 P.M., Tuesday, January 14th, 2003 |
| Place: | Room ETLC E2-001 |
| Speaker: | Lingzhi Cao M.Sc. Student University of Alberta |
| Topic: | Introduction of GSM Signaling Procedure |
| Abstract: |
Analysis of GSM signaling is one of the efficient methods to locate and solve GSM network problems. It is very important in wireless network optimization. Through the signaling data, information such as the causes of handover, channel release, and congestion can be known as well as the QoS of the network. In this presentation, some basic knowledge related to the signaling procedure will be introduced first. GSM signaling procedures such as radio link setup, authentication, location update, handover will be presented afterwards. The outline of the presentation is as follows: 1. GSM Architecture:
2. Base Station Subsystem (BSS) 3. Network and Switching System (NSS) 4. Optional Equipment (NSS) 5. Operation and Maintenance Subsystem 3. Radio Channel 4. BSS / NSS Protocols and Software Modules
2. Radio Interface (Um) : Layer 3 : "RIL 3" protocol 6. Level 3 GSM Procedures
2. Security Functions 3. Mobile Terminating Calls (MT) 4. Location Updates 5. Change of Cell during the Call ("Handover") |
| Time: | 3:30 P.M., Tuesday, February 4th, 2003 |
| Place: | Room ETLC E2-001 |
| Speaker: | Mohamed Oussama Damen Research Associate University of Alberta |
| Topic: | SISO Codes for MIMO Channels |
| Abstract: | Wireless channels are characterized by complex physical layer effects resulting from multitude of potentially mobile users communicating simultaneously in a multi-path fading environment. In such environments, reliable communication is made possible only through the use of diversity techniques in which the receiver is afforded multiple replicas of the transmitted signal under varying channel conditions. Antenna diversity techniques have recently received considerable attention due to the significant gains promised by information theoretic studies. While the use of multiple receive antennas is a well-explored problem, the design of space-time signals that exploit the available capacity in multi-transmit antenna systems still faces many challenges. A general framework for constructing multi-input multi-output (MIMO) space-time signals using single-input single-output (SISO) components is discussed in this talk. The combination of the threaded space-time architecture with algebraic number theoretic codes and constellations, or the threaded algebraic space-time (TAST) framework, is shown to be useful for constructing full rate, full diversity, and polynomial complexity space-time constellations for systems with arbitrary numbers of transmit and receive antennas, for scenarios where the channel state information (CSI) is known a-priori at the transmitter and receiver (TR-CSI), receiver only (R-CSI), and neither one of them (N-CSI). In addition, the TAST framework subsumes many of the existing space-time signaling schemes as special cases. Furthermore, the fundamental tradeoff between rate and diversity is examined under different constraints on the peak power, receiver complexity, and rate scaling with the signal-to-noise ratio. The talk will be concluded with a brief overview of possible avenues for future research. |
| Time: | 3:00 P.M., Wednesday, February 19th, 2003 |
| Place: | Room ETLC E2-002 |
| Speaker: | K. Sivanesan Ph.D. Student University of Alberta |
| Topic: | Cochannel Interference Mitigation Using Interference Whitening for Wireless Communication |
| Abstract: | The cochannel interference (CCI) and fading are the dominant impairments which limit the capacity of wireless communication systems. Cochannel interference mitigation of BPSK system in slow fading micro cellular environment is considered. The CCI of slow Rayleigh faded interferers is perfectly Gaussian distributed after coherent demodulation for synchronous and asynchronous interferers with rectangular pulse shaping and for synchronous interferers with bandlimited spectrum raised cosine pulse shaping at sampling instants. Thus, the receiver structure which maximizes the instantaneous signal to noise ratio, minimizes the average bit error rate. The whitening filter and signal to noise plus interference ratio maximizing filter is introduced in the conventional receiver structure. The performance is considerably better in variety of fading situations of desired user. |
| Time: | 3:30 P.M., Tuesday, March 11th, 2003 |
| Place: | Room ECERF W2-021 |
| Speaker: | M. Oussama Damen Research Associate University of Alberta |
| Topic: | iCORE MIMO Seminar -- Seminar on papers from Teletar (1995) and Foschini/Gans (1998) |
| Abstract: |
This seminar examines the following papers: E. Telatar, ``Capacity of multi-antenna Gaussian channels,'' Technical Report, Bell-Labs, June, 1995. Available on line at http://mars.bell-labs.com G. J. Foschini and M. Gans, ``On the limits of wireless communication in a fading environment when using multiple antennas,'' Wireless Personal Communications, March 1998. Available on line at http://mars.bell-labs.com |
| Time: | 3:30 P.M., Tuesday, March 11th, 2003 |
| Place: | Room ETLC E2-001 |
| Speaker: | Sheryl Howard Ph.D. Student University of Alberta |
| Topic: | Differentially Encoded Turbo Coded Modulation with APP Phase and Timing Estimation |
| Abstract: |
Phase and timing synchronization are crucial components of a digital communications system. However, the high noise environment which turbo codes are capable of operating in, along with the fast acquisition time required by wireless packet messaging due to short packet length, may preclude the PLL (phase-locked loop) technology typically used for synchronization. Higher order constellations, while increasing spectral efficiency, further complicate the matter with greater noise sensitivity. Differential modulation is a classic technique to avoid phase synchronization, but differential detection results in a nearly 3 dB loss in SNR for M-PSK, M>2. Extension of differential modulation to turbo codes shows a similar loss. Efforts to mitigate this loss have focused on multiple symbol detection, and quantizing phase states, resulting in a large state expansion of the decoding trellis. The APP decoder is the most complex portion of the iterative turbo decoding block. Rather than linearly expanding its state size, the APP soft information from the inner decoder may be used each iteration to form a channel estimate used within the decoding block. Such a channel phase estimator is presented in this talk and termed APP phase estimation. A serially concatenated system consisting of a [3,2,2] parity outer code with a differential 8-PSK inner code is presented, with an APP phase estimator incorporated into the iterative decoding block. No differential detection is used. Simulation results for this system with and without channel state information (CSI) are presented, with near-coherent results using the APP phase estimation for two different channel phase models. Coherent results show a turbo cliff 1.7 dB from 8-PSK capacity. Timing estimation using the APP soft symbol information available each iteration from the inner decoder will be considered as the next step in this research project. A standard DD (data-directed) timing estimation algorithm will be used inside the iterative decoding block, with symbol estimates derived each iteration from the APP soft information. Phase synchronization is assumed. Initial symbol estimates will be poor with significant timing offset, and use of the NDA (non-data-aided) form of this algorithm may prove necessary in the initial iterations. Should APP timing estimation proves feasible, joint timing/phase estimation will be considered as the final phase of this research project. |
| Time: | 5:00 P.M., Friday, March 14th, 2003 |
| Place: | Room ECERF W2-021 |
| Speaker: | Qiong Xie Research Associate University of Alberta |
| Topic: | iCORE MIMO Seminar -- Tarokh et al.(1998) seminar |
| Abstract: |
This seminar examines the following paper: V. Tarokh, N. Seshadri, and A. R. Calderbank, ``Space-time codes for high data rate wireless communication: Performance criterion and code construction,'' IEEE Trans. Inform. Theory, March 1998. |
| Time: | 3:30 P.M., Tuesday, March 18th, 2003 |
| Place: | Room ETLC E2-001 |
| Speaker: | David Young Ph.D. Student University of Alberta |
| Topic: | An Introduction to Parallel Programming in OpenMP |
| Abstract: |
Shared-memory multi-processor computers are now common, and in some cases significant reductions in run times for a program can be obtained when parallel computing is exploited in the program. In addition, some of Intel's newest processors use a technology called "hyperthreading" which make parallel programming relevant even to single-processor machines. However, designing and coding parallel programs that are both correct and efficient can be a complex problem. In computer simulation and related computation, the goal is typically a correct result rather than efficient program code, and programming effort may be viewed as a bigger cost than the run time of the code. OpenMP, a relatively new cross-platform standard, provides an efficient and portable means to introduce parallelism into program code. A key benefit of OpenMP is that it is relatively easy to introduce parallelism in small steps, useful for the parallel programming novice and for experimenting with parallelism in existing serial code. C/C++ and Fortran compilers which support OpenMP are available in the iCORE Wireless Communications Laboratory. This talk, tutorial in nature, is aimed at an audience with little or no parallel programming experience. It is based on the book _Parallel Programming in OpenMP_ (R. Chandra et al, Academic Press, 2001). Some background and motivation for parallel programming will be given. Techniques for parallelization of code will be presented with some simple code examples. Key issues in producing parallel code that is both correct (produces results identical to serial code) and efficient (produces results more quickly than serial code) will be discussed, highlighting where caution is needed. |
| Time: | 5:00 P.M., Friday, March 21th, 2003 |
| Place: | Room ECERF W2-021 |
| Speaker: | Lei Xiao M.Sc. Student University of Alberta |
| Topic: | iCORE MIMO Seminar -- Alamouti (1998) and Tarokh et al.(1999) seminar |
| Abstract: |
This seminar examines the following papers: S.M. Alamouti, ``A simple transmitter diversity scheme for wireless communications,'' IEEE Journal on Selected Areas in Communications, Oct. 1998. V. Tarokh, H. Jafarkhani, and A.R. Calderbank, ``Space-time block codes from orthogonal designs,'' IEEE Trans. Inform. Theory, July 1999. |
| Time: | 3:30 P.M., Tuesday, March 25th, 2003 |
| Place: | Room ETLC E2-001 |
| Speaker: | Wenyu Li M.Sc. Student University of Alberta |
| Topic: | iCORE MIMO Seminar -- Alamouti (1998) and Tarokh et al.(1999) seminar |
| Abstract: |
This presentation is based on Babak Hassibi & Bertrand M. Hochwald's paper "How Much Training is Needed in Multiple-Antenna Wireless Links?" Technical Memorandum, Bell Laboratories, Lucent Technologies, April 2000. http://mars.bell-labs.com Multiple-antenna wireless communication links promise very high data rates with low error probabilities, especially when the wireless channel response is known at the receiver. In practice, knowledge of the channel is often obtained by sending known training symbols to the receiver. In this presentation, it will be shown that how training affects the capacity of a fading channel---too little training and the channel is improperly learned, too much training and there is no time left for data transmission before the channel changes. An information-theoretic approach is used to compute the optimal amount of training as a function of the received signal-to-noise ratio, fading coherence time, and number of transmitter antennas. When the training and data powers are allowed to vary, it is shown that the optimal number of training symbols is equal to the number of transmit antennas---this number is also the smallest training interval length that guarantees meaningful estimates of the channel matrix. When the training and data powers are instead required to be equal, the optimal number of symbols may be larger than the number of antennas. As side results, the worst-case power-constrained additive noise in a matrix-valued additive noise channel is obtained, and training-based schemes are highly suboptimal at low SNR. |
| Time: | 5:00 P.M., Friday, March 28th, 2003 |
| Place: | Room ECERF W2-021 |
| Speaker: | Ge Li Ph.D. Student University of Alberta |
| Topic: | iCORE MIMO Seminar -- Hammons and Gamal (2000) seminar |
| Abstract: |
This presentation is based on the following paper: A.R. Hammons, Jr. and H. El Gamal, ``On the theory of space-time codes for PSK modulation,'' IEEE Trans. Inform. Theory, March 2000. |
| Time: | 3:30 P.M., Tuesday, April 1st, 2003 |
| Place: | Room ETLC E2-001 |
| Speaker: | Dr. Seung Joon Lee Post-doctoral Fellow University of Alberta |
| Topic: | A Design Example of a Burst-Mode TDMA Demodulator for Geostationary Earth Orbit Satellite Communications |
| Abstract: |
Digital Video Broadcasting-Return Channel via Satellite (DVB-RCS), recently published (year 2000) as an ETSI standard, forms the specification for the provision of the interaction channel for geostationary earth orbit (GEO) satellite interactive networks with fixed return channel satellite terminals (RCST). The standard, developed under the auspices of the DVB Forum, was created through the cooperation of satellite operators and satellite equipment manufactures, including system providers, hub manufacturers and terminal manufacturers. One of its important features concerned with physical layer as well as media access control layer is adopting multi-frequency TDMA for the sake of efficient use of radio resource. With this mechanism, a RCST may hop carrier frequencies timeslot by timeslot for transmission and so a burst-mode demodulator is required in a hub for return channel communication. In this design example, for achieving recovery of symbol timing and carrier frequency and phase for such burst transmission, a demodulator of feedforward type is considered to work better than feedback one suffering from hang-up phenomena. Additionally, different demodulator structures are prepared for different types of bursts (four types of bursts are suggested in DVB-RCS) since the characteristics of synchronization error depend on burst type. Many algorithms (of feedforward type) are surveyed for each synchronization function (such as symbol timing recovery, carrier recovery, etc.) and their performances are compared to select the best fit. The total system performance of the designed demodulator is addressed, concentrating on which makes a bottleneck preventing better total system performance. |
| Time: | 5:00 P.M., Friday, April 4th, 2003 |
| Place: | Room ECERF W2-021 |
| Speaker: | Bo Hu Ph.D. Student University of Alberta |
| Topic: | iCORE MIMO Seminar -- Hochwald and Sweldens (2000) seminar |
| Abstract: |
This presentation is based on the following paper: B.M. Hochwald and W. Sweldens, ``Differential unitary space-time modulation,'' IEEE Trans. Commun., Dec 2000. |
| Time: | 5:00 P.M., Friday, April 11th, 2003 |
| Place: | Room ECERF W2-021 |
| Speaker: | David Mazzarese Ph.D. Student University of Alberta |
| Topic: | iCORE MIMO Seminar -- Viswanath et al. (2002) seminar |
| Abstract: |
This presentation is based on the following paper: P. Viswanath, D.N.C. Tse, and R. Laroia, ``Opportunistic beamforming using dumb antennas,'' IEEE Trans. Inform. Theory, June 2002. |
| Time: | 3:40 P.M., Friday, April 15th, 2003 |
| Place: | Room ETLC E1-008 |
| Speaker: | David Mazzarese Ph.D. Student University of Alberta |
| Topic: | High Throughput Downlink Cellular Packet Data Access with Multiple Antennas and Multiuser Diversity |
| Abstract: | We present a discussion of MIMO (multiple-input multiple-output) systems designed to exploit multiuser diversity, with the principal goal of increasing throughput of delay tolerant data services to nomadic and mobile users in cellular systems. We consider the downlink of a cellular packet data access scheme with a base station transmit antenna array and users equipped with a single receive antenna. We show that it can be preferable to transmit to several users simultaneously using the transmit antenna array even with sub-optimal signaling. This is in contrast to single antenna systems exploiting multiuser diversity and using link adaptation, in which the average throughput per sector is maximized, when in any packet time slot transmission occurs only to one user experiencing the best channel conditions at the time. We propose several scheduling algorithms and compare their performance to the throughput achievable with precoding and perfect channel state information at the transmitter. We show that the capacity scaling typical to MIMO systems can be achieved even with single-antenna mobile receivers, but only a fraction of that capacity can be used with limited channel knowledge at the transmitter, when multiuser diversity is exploited. |
| Time: | 3:00 P.M., Tuesday, April 15th, 2003 |
| Place: | Room ETLC E1-008 |
| Speaker: | Ge Li Ph.D. Student University of Alberta |
| Topic: | Low-Density Parity-Check Codes for Space-Time Wireless Transmission |
| Abstract: |
It has been shown theoretically that using multiple antennas at both ends of a wireless link can significantly increase channel capacity, as well as improve quality of transmission. Space-time coding integrates channel coding, modulation and transmit diversity to exploit this high capacity, without requiring instantaneous channel knowledge at the transmitter. This talk will discuss the design of a high data rate space-time coding scheme using low-density parity-check (LDPC) codes. LDPC codes have shown a great potential in achieving Shannon's channel capacity limits for single antenna systems. These codes, when properly optimized using numerical density evolution techniques, can achieve reliable transmission at signal-to-noises ratios extremely close to the Shannon limit on the additive Gaussian noise (AWGN) channel, Rayleigh fading channel, etc. In the first part of this talk, I will present our design of LDPC codes for use with a multiantenna system on flat Rayleigh fading channels. For systems with a relatively small number of transmit antennas, we focus on space-time coding employing binary and 2^p-ary LDPC codes, where p equals the number of encoded bits transmitted by the transmit antenna array during each signaling interval. For systems with a large transmit array, we study a layered space-time architecture using binary LDPC codes as component codes of each layer. The quality of the codes involved is then assessed in terms of frame error rate via simulation under various fading conditions. For multiantenna systems with diversity order larger than two, we show that LDPC codes of quasi-regular or irregular construction are able to achieve higher coding gain and/or diversity gain than convolutional codes and turbo codes of similar, if not lower decoding complexity. To show our design of q-ary LDPC codes for multiantenna systems, the second part of this talk will present the approximate Gaussian density evolution technique we have developed for the q-ary-input symmetric-output channels. Under the Gaussian assumption, we prove that the density evolution of q-ary sum-product decoding is fully characterized by (q-1) quantities. I will describe our code optimization technique for nonbinary LDPC codes using the approximate density evolution, and show that codes thus designed specifically for single-antenna AWGN channels are able to achieve good performance with multiantenna systems as well. |