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1. M. Hayajneh, C.T. Abdallah, "Distributed Joint Rate and Power Control Game-Theoretic Algorithms for Wireless Data", IEEE Communications Letters, VOL. 8, NO. 8, pp.511-513, Aug. 2004.   [pdf]

   Abstract: In this letter, we consider two distributed game theoretic algorithms to jointly solve the problem of optimizing the transmission rates and transmit powers for future wireless data communication systems. We then establish the existence, uniqueness and Pareto optimality of Nash equilibria of both games.



2. M. Hayajneh,and C. T. Abdallah "Performance of Game Theoretic Power Control Algorithms for Wireless Data in Fading Channels", Submitted to IEEE GLOBECOM 2003, San Francisco, CA, December 2003.   [pdf]

   Abstract: An efficient use of the radio resources in wireless communications presents a fundamental challenge. While power is one of the most important radio resources, and its control has been studied extensively for voice communications, the increase demand of wireless data service makes it very important to establish power control algorithms for such service. In Code Division Multiple Access (CDMA) cellular systems we have a number of users who are simultaneously sharing the air interface. Each user wants to achieve a high Signal-to-Interference ratio (SIR) at the Base-Station (BS) with the lowest possible transmitted power level. These conflicting objectives of the users make the framework of game theory suitable to establish power control algorithms. In [1] a non-cooperative power control game (NPG) was proposed where each user unilaterally maximizes his quality of service (QoS), referred to as a ”utility”. The result of such NPG however, is a Nash equilibrium which is not efficient. To obtain a Pareto improvement, [1] introduced a pricing of the transmit power in which each user’s goal is to maximize a difference between the utility function of NPG and a linear pricing function with respect to the transmit power. However, in [1] the channel model is not realistic, as they only considered deterministic channel path gains from the BS to the user. Signals in a wireless communications experience different types of fading. In this paper we consider the problem studied in [1] with three cases of fading: Rayleigh flat fading, Rician flat fading and Nakagami flat fading. In all cases, the channel is assumed to be quasi static,i.e, the fading coefficient is constant during each packet’s duration.



3. J.A. Rohwer, C.T. Abdallah, and C. Christodoulou, "Least Squares Support Vector Machines for Direction of Arrival Estimation with Error Control Validation", IEEE Transactions GlOBECOM 2003, pp.2172-2176, San Francisco, CA, Dec. 2003.   [pdf]

   Abstract: This paper presents a multiclass, multilabel implementation of Least Squares Support Vector Machines (LS-SVM) for direction of arrival (DOA) estimation in a CDMA system. For any estimation or classification system the algorithm’s capabilities and performance must be evaluated. Specifically, for classification algorithms a high confidence level must exist along with a technique to automatically tag misclassifications. The learning algorithm presented in this paper includes error control and validation steps for generating statistics on the multiclass evaluation path and the signal subspace dimension. The error statistics provide a confidence level of the classification accuracy.



4. J.A. Rohwer, C.T. Abdallah, and C. Christodoulou, "Machine Learning Based CDMA Power Control", IEEE Transactions, pp.207-211, 2003.   [pdf]

   Abstract: This paper presents binary and multiclass machine learning techniques for CDMA power control. The power control commands are based in estimates of the signal and noise subspace eigenvalues and the signal subspace dimension. Results of two different sets of machine learning algorithms are presented. Binary machine learning algorithms generate fixed-step power control (FSPC) commands based on estimated eigenvalues and SIRs. A fixed-set of power control commands are generated with multiclass machine learning algorithms. The results show the limitations of a fixed-set power control system, but also show that a fixed-set system achieves comparable performance to high complexity closed-loop power control systems.



5. M. Hayajneh,and C. T. Abdallah "Performance of Game Theoretic Power Control Algorithms In Interference Limited Wireless Fading Channels", Submitted to Sixth Baiona Workshop on Signal Processing in Communications 2003, Baiona, SPAIN, September 2003.   [pdf]

   Abstract: We consider a game-theoretic power control algorithm in interference limited fading channels, where we propose a distributed (non-cooperative) algorithm to optimize the induced fading outage probability by maximizing the certainty equivalent margin (CEM). We prove that the problem of maximizing CEM is the same (up to an upper bound) as minimizing the induced outage fading probability, and provide a distributed game theoretic power control algorithm.



6. N. Herscovici, C. Christodoulu, L.S. Bakim, C.T. Abdallah, and E. Schamiloglu, "Communicating with Microwave-Propelled Sails", IEEE Antennas and Propagation Magazine, Vol. 45, No. 4, pp.111-122, Aug. 2003.   [pdf]

   Abstract: We describe a communication channel for a microwave-propelled sail, a novel concept for a deep-space scientific probe. We suggest techniques to recover the great loss introduced by the large distances, and we have conducted various simulations to understand the effects on the performance of the system. Possible disruption in the channel by high-energy solar flares, which increase the error in the estimation of the received signal, is accounted for. We developed the simulation for a full communication system on an additive white Gaussian noise (AWGN) channel, including the random-time solar-flare disturbance. We show that turbo codes can be exploited that perform very well at low SNRs and have high coding gain.



7. M. Hayajneh, C.T. Abdallah, "Statistical Learning Theory to Evaluate The Performance of Game Theoretic Power Control Algorithms for Wireless Data in Arbitrary Channels", IEEE Transactions, pp.723-728, 2003   [pdf]

   Abstract: In this paper we use statistical learning theory to evaluate the performance of game theoretic power control algorithms for wireless data in arbitrary channels, i.e., no presumed channel model is required. To show the validity of statistical learning theory in this context, we studied a flat fading channel, and more specifically, we simulated the case of Rayleigh flat fading channel. With the help of a relatively small number of training samples, the results suggest the learnability of the utility function classes defined by changing the users power (adjusted parameter) for each user’s utility function.



8. I. Guvenc, C. T. Abdallah, R. Jordan and O. Dedeoglu, "Enhancements to RSS Based Indoor Tracking Systems Using Kalman Filters", Accepted, GSPx & International Signal Processing Conference, Dallas, TX, March 31-April 3, 2003.   [pdf]

   Abstract: This paper describes the site survey issues when deploying a wireless local area network (WLAN), the implementation of a location system over the deployed network, and the application of a Kalman filtering algorithm to enhance the tracking performance. We have made a site survey in the Electrical and Computer Engineering (EECE) department of University of New Mexico (UNM) to optimally position the access points. Ekahau Positioning Engine [1] was used to find the coverage areas of all available access points throughout the building. After having the network up and running, the signal strength values at certain locations are recorded and an indoor propagation analysis is made. A nearest neighbors algorithm and its variants are used to construct a location system and possible ways of improvements are discussed. Improvements in the estimation error using a Kalman filter algorithm are then presented.



9. M. Hayajneh,and C. T. Abdallah "Performance of Game Theoretic Power Control Algorithms for Wireless Data in Fast Flat Fading Channels", 2003 IEEE Wireless Communications and Networking Conference, Vol. 2, pp.723 -725, New Orleans, Louisiana, March 2003.   [pdf]

   Abstract: In this paper we use statistical learning theory to evaluate the performance of game theoretic power control algorithms for wireless data in arbitrary channels, i.e., no presumed channel model is required. To show the validity of statistical learning theory power control game (NPG) and a noncooperative in this context, we studied a flat fading channel, and more specifi- cally, we simulated the case of Rayleigh flat fading channel. With the help of a relatively small number of training samples, the results suggest the learnability of the utility function classes defined by changing the users power (adjusted parameter) for each user’s utility function.



10. J.A. Rohwer, C.T. Abdallah, and C. Christodoulou, "Least Squares Support Vector Machines for Direction of Arrival Estimation", IEEE Transactions, pp.57-60, 2003.   [pdf]

    Abstract: Machine learning research has largely been devoted to binary and multiclass problems relating to data mining, text categorization, and pattern/facial recognition. Recently, popular machine learning algorithms, including support vector machines (SVM), have successfully been applied to wireless communication problems, notably spread spectrum receiver design [1], channel equalization [2].This paper presents a multiclass implementation of SVMs for direction of arrival (DOA) estimation.

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