Karim Seddik - Academia.edu (original) (raw)
Papers by Karim Seddik
IEEE Transactions on Vehicular Technology, 2021
2017 IEEE International Conference on Communications (ICC), 2017
Wireless communications standards increasingly use multiple antenna systems for increasing the sy... more Wireless communications standards increasingly use multiple antenna systems for increasing the system throughput. We consider the Multiple Input Multiple Output (MIMO) system of the Long Term Evolution (LTE) standard and provide detailed comparisons, in terms of hardware complexity, between two near-optimal decoders for such a system. In particular, we compare the K-Best and the selective spanning with fast enumeration (SSFE) decoders. For equal BER performance, we find that the K-best requires a smaller number of operations, particularly for the large decoder sizes needed to satisfy the conformance specifications in practical wireless communication standards.
IEEE Transactions on Wireless Communications, 2013
ABSTRACT In this paper, we examine a cognitive spectrum access scheme in which secondary users ex... more ABSTRACT In this paper, we examine a cognitive spectrum access scheme in which secondary users exploit the primary feedback information. We consider an overlay secondary network employing a random access scheme in which secondary users access the channel by certain access probabilities that are functions of the spectrum sensing metric. In setting our problem, we assume that secondary users can eavesdrop on the primary link's feedback. We study the cognitive radio network from a queuing theory point of view. Access probabilities are determined by solving a secondary throughput maximization problem subject to a constraint on the primary queues' stability. First, we formulate our problem which is found to be non-convex. Yet, we solve it efficiently by exploiting the structure of the secondary throughput equation. Our scheme yields improved results in, both, the secondary user throughput and the primary user packet delay as compared to the scheme where no feedback information is exploited. In addition, it comes very close to the optimal genie-aided scheme in which secondary users act upon the presumed perfect knowledge of the primary users' activity.
2016 14th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 2016
2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC), 2014
IEEE Transactions on Vehicular Technology, 2016
2016 13th IEEE Annual Consumer Communications & Networking Conference (CCNC), 2016
2015 IEEE Global Communications Conference (GLOBECOM), 2014
2015 IEEE Global Communications Conference (GLOBECOM), 2014
2015 IEEE Global Conference on Signal and Information Processing (GlobalSIP), 2015
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2015
In this paper, we study the fundamental trade-off between delay-constrained primary and secondary... more In this paper, we study the fundamental trade-off between delay-constrained primary and secondary users in cognitive radio networks. In particular, we characterize and optimize the trade-off between the secondary user (SU) effective capacity and the primary user (PU) average packet delay. Towards this objective, we employ Markov chain models to quantify the SU effective capacity and average packet delay in the PU queue. Afterwards, we formulate two constrained optimization problems to maximize the SU effective capacity subject to an average PU delay constraint. In the first problem, we use the spectrum sensing energy detection threshold as the optimization variable. In the second problem, we extend the problem and optimize also over the transmission powers of the SU. Interestingly, these complex non-linear problems are proven to be quasi-convex and, hence, can be solved efficiently using standard optimization tools. The numerical results reveal interesting insights about the optimal performance compared to the unconstrained PU delay baseline system.
2014 International Wireless Communications and Mobile Computing Conference (IWCMC), 2014
2014 Ieee Global Conference on Signal and Information Processing, Dec 1, 2014
Ieee Globecom 2007 Ieee Global Telecommunications Conference, 2007
ABSTRACT Spectrum sensing in wideband cognitive radio networks is challenged by several factors s... more ABSTRACT Spectrum sensing in wideband cognitive radio networks is challenged by several factors such as hidden primary users, overhead on network resources, and the requirement of high sampling rate. Compressive sensing has been proven effective to elevate some of these problems through efficient sampling and exploiting the underlying sparse structure of the measured frequency spectrum. In this paper, we propose an approach for collaborative compressive spectrum sensing. The proposed approach achieves improved sensing performance through utilizing Kronecker sparsifying bases to exploit the two dimensional sparse structure in the measured spectrum at different, spatially separated cognitive radios. Experimental analysis through simulation shows that the proposed scheme can substantially reduce the mean square error (MSE) of the recovered power spectrum density over conventional schemes while maintaining the use of a low-rate ADC. We also show that we can achieve dramatically lower MSE under low compression ratios using a dense measurement matrix but using Nyquist rate ADC.
2014 Ieee Global Conference on Signal and Information Processing, Dec 1, 2014
IEEE Transactions on Vehicular Technology, 2021
2017 IEEE International Conference on Communications (ICC), 2017
Wireless communications standards increasingly use multiple antenna systems for increasing the sy... more Wireless communications standards increasingly use multiple antenna systems for increasing the system throughput. We consider the Multiple Input Multiple Output (MIMO) system of the Long Term Evolution (LTE) standard and provide detailed comparisons, in terms of hardware complexity, between two near-optimal decoders for such a system. In particular, we compare the K-Best and the selective spanning with fast enumeration (SSFE) decoders. For equal BER performance, we find that the K-best requires a smaller number of operations, particularly for the large decoder sizes needed to satisfy the conformance specifications in practical wireless communication standards.
IEEE Transactions on Wireless Communications, 2013
ABSTRACT In this paper, we examine a cognitive spectrum access scheme in which secondary users ex... more ABSTRACT In this paper, we examine a cognitive spectrum access scheme in which secondary users exploit the primary feedback information. We consider an overlay secondary network employing a random access scheme in which secondary users access the channel by certain access probabilities that are functions of the spectrum sensing metric. In setting our problem, we assume that secondary users can eavesdrop on the primary link's feedback. We study the cognitive radio network from a queuing theory point of view. Access probabilities are determined by solving a secondary throughput maximization problem subject to a constraint on the primary queues' stability. First, we formulate our problem which is found to be non-convex. Yet, we solve it efficiently by exploiting the structure of the secondary throughput equation. Our scheme yields improved results in, both, the secondary user throughput and the primary user packet delay as compared to the scheme where no feedback information is exploited. In addition, it comes very close to the optimal genie-aided scheme in which secondary users act upon the presumed perfect knowledge of the primary users' activity.
2016 14th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 2016
2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC), 2014
IEEE Transactions on Vehicular Technology, 2016
2016 13th IEEE Annual Consumer Communications & Networking Conference (CCNC), 2016
2015 IEEE Global Communications Conference (GLOBECOM), 2014
2015 IEEE Global Communications Conference (GLOBECOM), 2014
2015 IEEE Global Conference on Signal and Information Processing (GlobalSIP), 2015
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2015
In this paper, we study the fundamental trade-off between delay-constrained primary and secondary... more In this paper, we study the fundamental trade-off between delay-constrained primary and secondary users in cognitive radio networks. In particular, we characterize and optimize the trade-off between the secondary user (SU) effective capacity and the primary user (PU) average packet delay. Towards this objective, we employ Markov chain models to quantify the SU effective capacity and average packet delay in the PU queue. Afterwards, we formulate two constrained optimization problems to maximize the SU effective capacity subject to an average PU delay constraint. In the first problem, we use the spectrum sensing energy detection threshold as the optimization variable. In the second problem, we extend the problem and optimize also over the transmission powers of the SU. Interestingly, these complex non-linear problems are proven to be quasi-convex and, hence, can be solved efficiently using standard optimization tools. The numerical results reveal interesting insights about the optimal performance compared to the unconstrained PU delay baseline system.
2014 International Wireless Communications and Mobile Computing Conference (IWCMC), 2014
2014 Ieee Global Conference on Signal and Information Processing, Dec 1, 2014
Ieee Globecom 2007 Ieee Global Telecommunications Conference, 2007
ABSTRACT Spectrum sensing in wideband cognitive radio networks is challenged by several factors s... more ABSTRACT Spectrum sensing in wideband cognitive radio networks is challenged by several factors such as hidden primary users, overhead on network resources, and the requirement of high sampling rate. Compressive sensing has been proven effective to elevate some of these problems through efficient sampling and exploiting the underlying sparse structure of the measured frequency spectrum. In this paper, we propose an approach for collaborative compressive spectrum sensing. The proposed approach achieves improved sensing performance through utilizing Kronecker sparsifying bases to exploit the two dimensional sparse structure in the measured spectrum at different, spatially separated cognitive radios. Experimental analysis through simulation shows that the proposed scheme can substantially reduce the mean square error (MSE) of the recovered power spectrum density over conventional schemes while maintaining the use of a low-rate ADC. We also show that we can achieve dramatically lower MSE under low compression ratios using a dense measurement matrix but using Nyquist rate ADC.
2014 Ieee Global Conference on Signal and Information Processing, Dec 1, 2014