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 2009
| Time: | 2:00 P.M., Monday, March 16th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Prasanna Kalansuriya University of Alberta |
| Topic: | Performance Analysis of Decode-and-Forward Relay Network Under Adaptive M-QAM |
| Abstract: | The performance of a cooperative Decode-and-Forward (DF) relay network with adaptive M-ary Quadrature Amplitude Modulation (M-QAM) is analyzed. A five-mode adaptive M-QAM scheme is employed, and the system performance is investigated for both fixed switching levels and for optimized switching levels with a target bit error rate (BER) constraint. Expressions for average BER, spectral efficiency, and outage probability are derived to investigate the performance of the cooperative system under independently and identically distributed (i.i.d.) Nakagami-m fading wireless environments. Adaptive M-QAM with optimized switching levels maintains the target BER constraint while fixed switching levels achieves a conservative BER, which is lower than the target. |
| Time: | 2:00 P.M., Monday, March 16th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Hua Shao University of Alberta |
| Topic: | Statistical Analysis of Multiple Access Interference in Asynchronous UWB Impulse Radio |
| Abstract: | Optimal component and system design requires knowledge of the statistics underlying the system. To date, the determination of the probability distributions characterizing the multiple access interference in ultra-wide bandwidth wireless systems is an unsolved problem. The statistical characteristics of the multiple access interference in ultra-wide bandwidth wireless systems are studied. Expressions for the probability density functions of the distribution due to asynchronous multiple access interference and additive white Gaussian noise are derived for both additive white Gaussian noise and multipath fading ultrawide bandwidth environments. The accuracies of the derived expressions for the probability density functions are assessed and confirmed by simulation results. |
| Time: | 2:00 P.M., Monday, March 9th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Gongpu Wang University of Alberta |
| Topic: | Super-imposed Pilot-Aided Channel Estimation and Power Allocation for Relay Systems |
| Abstract: | Super-imposed pilots can be used as an alternative to traditional pilots that are used for channel estimation. Superimposed pilots improve bandwidth efficiency. We apply it to the Amplify and Forward (AF) relay systems. In this paper we give the channel estimation (CE) results, analyze the system performance, study the power allocation methods and extend our result to multi-hop relay systems. Our main contribution is that we suggest and prove the existence of minimum bit error rate (BER) as a function of pilot signal power, find the best power allocation ratio value that can reach the minimum BER, analyze parameters? influence on the ratio value, and extend our result to multi-hop systems. |
| Time: | 2:00 P.M., Monday, March 9th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Duy Trong Ngo (Danny) University of Alberta |
| Topic: | Resource Allocation for OFDM-based Cognitive Radio Multicast Networks |
| Abstract: | In cognitive radio networks with the coexistence of primary and secondary users, the problem of how to optimally allocate available resources (e.g., bandwidth and power) to multicast groups of secondary users that use orthogonal frequency division multiplexing (OFDM) is important. Taking the maximization of the weighted sum rate of such groups as the design objective, we propose a practically optimal subcarrier and power allocation scheme under constraints on the tolerable interference thresholds at individual primary user's frequency bands. Specifically, the optimization problem is solved via the dual method, where subcarriers are assigned in a per-tone basis and power is distributed in a water-filling fashion. As the number of subcarriers becomes large, the dual-domain solution becomes the global optimum of the primal problem with the duality gap vanishing to zero. The proposed design is valid for both unicast and multicast transmissions, and its computational complexity is only linear in the number of subcarriers. The effects of adjacent subcarrier nulling technique, which is to reduce mutual interference between primary and secondary frequency bands, on the proposed scheme are also examined. The superiority of the dual approach is confirmed by numerical results. |
| Time: | 2:00 P.M., Monday, March 2nd, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Amin Emad University of Alberta |
| Topic: | Effect of a Cochannel Interferer on an Automatic Frequency Control Loop in Fading Channels |
| Abstract: | The mean time to loss of lock and the average switching rate of an automatic frequency control loop operating in fading in the presence of a single interferer are derived. Closed-form expressions and integral form formulas are derived for the general case of modulated carriers as well as important special cases of similar modulations and unmodulated carriers. The general results include, as special cases, some previous more restricted results. Fading channels are assumed to be independent non-identically distributed (i.n.d.) with Rayleigh, Rician and Nakagami-m distributions while the special case of independent identically distributed (i.i.d.) channels is also considered. Corresponding numerical examples are provided and discussed to illustrate the results. |
| Time: | 2:00 P.M., Monday, March 2nd, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Amin Emad University of Alberta |
| Topic: | Mean Time to Loss of Lock and Average Switching Rate of an Automatic Frequency Control Loop with an Interferer and Noise in a Fading Channel |
| Abstract: | The performance of an automatic frequency control (AFC) loop in a noisy fading channel when an interference signal is present at the input of the AFC is studied. Independent non-identically distributed (i.n.d.) channels with Rayleigh and Rician fading are considered. The received signals are assumed to be narrowband and linearly modulated while the analysis is applicable to the unmodulated scenario as well. Closed-form expressions and integral form formulas are derived for the mean time to loss of lock (MTLL) and the average switching rate (ASR) of an AFC. Numerical examples are provided to illustrate the effects of noise and slow fading on the performance of an AFC in the presence of an interferer. It is shown that in some scenarios, an AFC has a better performance if the desired signal is corrupted by more noise. |
| Time: | 2:00 P.M., Monday, February 23rd, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Damith Senaratne University of Alberta |
| Topic: | Unified Performance Analysis of Two Hop Amplify and Forward Relaying |
| Abstract: | We present unified performance analysis results for two hop Amplify and Forward (AF) relaying over Nakagamim fading nonidentical source-to-relay (S-R) and relay-to-destination (R-D) links. The results cover channel-noise-assisted, channel-assisted and blind relay configurations. Closed form expressions are derived for cumulative distribution function (CDF), probability density function (PDF), and moment generating function (MGF). Exact results are derived for symbol error rate (SER) of specific configurations. All results are verified through Monte Carlo simulation. |
| Time: | 2:00 P.M., Monday, February 23rd, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Xin Wang University of Alberta |
| Topic: | Switching Rates of Dual Selection Diversity in kappa-mu and alpha-mu Fading Channels |
| Abstract: | Switching rate is an important parameter in selection diversity receiver design because the switching transients increase the system outage. An exact closed-form solution for the switching rate of dual selection diversity in kappa-mu and alpha-mu distributed fadings is derived. Independent and identically distributed (i.i.d.) kappa-mu and alpha-mu fading channels are considered. The switching rate for dual i.i.d. kappa-mu distributed fading includes the switching rate for dual i.i.d. Rayleigh, Rician and Nakagami-m fading channels as special cases. Similarly, the switching rate for dual alpha-mu fading channels also includes special cases such as Rayleigh, Nakagami-m and Weibull fading channels. |
| Time: | 2:00 P.M., Monday, February 9th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Dr. Young Gil Kim University of Alberta |
| Topic: | A Greedy Cophasing Scheme for MIMO Beamforming Systems Using Quantized Feedback |
| Abstract: | In this talk, we propose the Hadamard matrix as a codebook for multiple-input multiple-output (MIMO) beamforming system, and show that the quantized equal gain transmission (QEGT) scheme using the Hadamard matrix has the same symbol error probability performance as a receiver selection diversity combining scheme in independent generalized Rayleigh fading channels. Also, we propose a greedy cophasing scheme for MIMO beamforming systems using quantized feedback. The greedy cophasing scheme provides 3.2 dB power gain over an orthogonal space-time block code when the number of transmit antennas is four, the number of receive antennas is one, and the number of feedback bits is three. |
| Time: | 2:00 P.M., Monday, February 9th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Damith Senaratne University of Alberta |
| Topic: | A General Numerical Method for Computing the Probability of Outage |
| Abstract: | The outage probability is a fundamental performance metric, which has been widely investigated in the literature. In this paper, we develop a general method to compute the outage given the moment generating function (MGF). When computing the outage using the MGF, integration along the standard Bromwich contour suffers from a loss of accuracy due to oscillatory nature of the integrand. One can address this difficulty by using the Cauchy’s theorem to replace the Bromwich contour by an appropriate equivalent contour. For highly-accurate numerical results, the steepest descent contour is the most suitable replacement. Unfortunately, this optimal contour can not be in general expressed in closed-form. The class of Talbot contours characterized by three parameters provides an alternative. However, it is not clear how these parameters need to be tuned for best results. We propose the use of linear regression to set the parameter values so as to minimize the mismatch between corresponding Talbot contour and the steepest-descent contour. The resulting integral has a smooth and rapidly decaying integrand, making it possible for the outage probability to be evaluated with high accuracy by using a simple numerical integration method. This approach is general in a sense that it works for any system where the MGF is known. Thus, it can handle a wide range of fading distributions and a variety of communication systems. |
| Time: | 2:00 P.M., Monday, February 2nd, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Iraj Hosseini University of Alberta |
| Topic: | Low-Complexity Multisampling Multiuser Detector for Time-Hopping UWB Systems |
| Abstract: | Multiple access interference (MAI) in time hopping (TH) ultra-wideband (UWB) systems is known to be non-Gaussian. Much previous research in TH-UWB receiver design has attempted to propose better single-user UWB detectors by introducing more accurate models for the distribution of the MAI. Recently, it was shown that some of the single-user receivers track closely the optimum achievable single-user performance. Although, these receivers are simple, all suffer from error rate floors, and hence limited user capacity. Multiuser detection (MUD) is considered for offering high performance at the cost of complexity that grows exponentially with the number of users. Thought to be too complex for low-cost UWB receivers, MUD applied in TH-UWB systems benefits from the low duty cycle implying that the number of effective interfering users is small compared to the number of active users. A novel low-complexity multisampling multiuser detector inspired by the inferiority of single-user receivers and the small number of effective interfering users in TH-UWB systems is proposed. Simulation results show that this detector achieves the performance of the conventional matched filter receiver operating in a single-user system. |
| Time: | 2:00 P.M., Monday, February 2nd, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Shuo Liu University of Alberta |
| Topic: | Large SNR Analysis of Diversity Schemes over Rayleigh Channels with Arbitrary Correlation |
| Abstract: | Asymptotic error rate expressions are derived for multi-branch equal gain combining and selection combining operating on arbitrarily correlated Rayleigh fading channels. These closed-form solutions are used to provide rapid and accurate estimation of the error rates in large signal-to-noise ratio regions. More importantly, it is shown that the asymptotic error rates over correlated branches can be obtained by scaling the asymptotic error rates over independent branches with the determinant of the normalized channel correlation matrix. |
| Time: | 2:00 P.M., Monday, January 26th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Iraj Hosseini University of Alberta |
| Topic: | A TH-UWB Receiver With Near-MUD Performance for Multiple Access Interference Environments |
| Abstract: | The multiple access interference (MAI) in a time-hopping (TH) ultra-wideband (UWB) system is known to be non-Gaussian even when the system has a moderately large number of active users. Therefore, the conventional matched filter (CMF) receiver, the optimal structure for Gaussian noise which maximizes the signal-to-noise ratio (SNR) and minimizes the probability of detection error in the absence of non-Gaussian interference, is not necessarily optimal. We express and prove a stronger claim that even the outputs of the matched filters in the conventional UWB receiver can not provide a sufficient decision statistic for detecting the information bits transmitted by the desired user. Further, a novel TH-UWB receiver is introduced which uses a similar methodology to the optimal multiuser detection (MUD) algorithm for detecting the information bits. However, the complexity of this new receiver is much less than that of the optimal MUD algorithm. It employs only one matched filter instead of a bank of matched filters resulting in a simple and low-cost TH-UWB receiver. Simulation results show that the new receiver outperforms previous single-user TH-UWB receivers and achieves essentially the performance of the CMF receiver operating in a single-user system. |
| Time: | 2:00 P.M., Monday, January 26th, 2009 |
| Place: | Room ETLC E2-002 |
| Speaker: | Ali Sharifkhani University of Alberta |
| Topic: | Packet Transmission Scheduling Algorithm for Wireless Sensor Networks with Energy Limited Mobile Sink |
| Abstract: | A transmission scheduling algorithm is proposed for wireless sensor networks with energy limited mobile sinks. The algorithm is primarily based on the well known tradeoff between the expected number of data packets that are successfully received by the sink and the transmission power consumed in the system. The likelihood of having new packets generated at the sensor node during the transmission as well as the possibility of erroneous reception of acknowledge packets at the sensor node are accounted for in the algorithm. The behavior of the system is studied in terms of power consumption and packet reception for different packet generation rates as well as different costs of transmission power at the sink. |