Haythem Bany salameh | Yarmouk University (original) (raw)

Papers by Haythem Bany salameh

IEEE Access

Dynamic Spectrum Access (DSA) technology in wireless Cognitive Radio Networks (CRNs) provides opp... more Dynamic Spectrum Access (DSA) technology in wireless Cognitive Radio Networks (CRNs) provides opportunistic access for unlicensed users, also known as Secondary Users (SUs), which can offer huge bandwidth to enable future wireless communication. Mainly, this technology aims to improve the endto-end throughput by allowing SUs to exploit the licensed channels only when their licensed users, also known as Primary Users (PUs), are not using them. Most existing communication protocols designed for CRNs are based on the assumption that the channel availability time is considered based on a memoryless distribution for PUs arrivals. Unfortunately, this assumption is impractical because the PU channels' activity and availability are memory-time correlated. Worse yet, designing communication protocols for CRNs under this assumption can result in overestimating the Probability of Success (PoS) for SU packet transmissions, resulting in severe degradation in network performance in realistic scenarios. This paper derives a closed-form formula under memory-time correlation for channel availability that quantifies the PoS for SUs' packet transmission in CRNs. This will empower the network designers to get practical expectations about network efficiency rather than the overestimated PoS. Therefore, this work is also useful for emerging wireless networks with multi-hop routing, such as 5G, 6G, vehicular networks, etc., which incorporate DSA techniques. Our numerical and simulation results demonstrate that the PoS is overestimated in most of the literature due to adopting memoryless-based distribution in modeling channels' availability; such overestimation can impact communication protocol decisions, resulting in severe network performance degradation.

AEU - International Journal of Electronics and Communications, 2020

The pilot overhead provides fundamental limits on the performance of massive multiple-input multi... more The pilot overhead provides fundamental limits on the performance of massive multiple-input multipleoutput (MIMO) systems. This is because the performance of such systems is based on the failure of the presentation of accurate channel state information (CSI). Based on the theory of compressive sensing, this paper presents a novel channel estimation technique as the mean of minimizing the problems associated with pilot overhead. The proposed technique is based on the combination of the compressive sampling matching and sparsity adaptive matching pursuit techniques. The sources of the signals in MIMO systems are sparsely distributed in terms of spatial correlations. This distribution pattern enables then use of compressive sampling techniques to solve the channel estimation problem in MIMO systems. Simulation results demonstrate that the proposed channel estimation outperforms the conventional compressive sensing (CS)-based channel estimation algorithms in terms of the normalized mean square error (NMSE) performance at high signal-to-noise ratios (SNRs). Furthermore, it reduces the computational complexity of the channel estimation compared to conventional methods. In addition to the achieved performance gain in terms of NMSE, the presented method significantly reduces pilot overhead compared to conventional channel estimation techniques.

International Journal of Electrical and Computer Engineering (IJECE), 2020

Several wireless technologies have recently emerged to enable efficient and scalable internet-of-... more Several wireless technologies have recently emerged to enable efficient and scalable internet-of-things (IoT) networking. Cognitive radio (CR) technology, enabled by software-defined radios, is considered one of the main IoT-enabling technologies that can provide opportunistic wireless access to a large number of connected IoT devices. An important challenge in this domain is how to dynamically enable IoT transmissions while achieving efficient spectrum usage with a minimum total power consumption under interference and traffic demand uncertainty. Toward this end, we propose a dynamic bandwidth/channel/power allocation algorithm that aims at maximizing the overall network’s throughput while selecting the set of power resulting in the minimum total transmission power. This problem can be formulated as a two-stage binary linear stochastic programming. Because the interference over different channels is a continuous random variable and noting that the interference statistics are highly...

2016 IEEE Wireless Communications and Networking Conference, 2016

Direct-conversion radio transceivers can offer reprogrammable and low-cost hardware solutions for... more Direct-conversion radio transceivers can offer reprogrammable and low-cost hardware solutions for full-duplex (FD) cognitive radio (CR) devices. However, they are susceptible to radio frequency (RF) impairments, such as in-phase (I) and quadrature (Q) imbalance (IQI), which can significantly constrain the spectrum sensing capabilities. This paper is devoted to quantify and evaluate the effects of IQI in the context of spectrum sensing in FD CR systems, in which self-interference suppression (SIS) techniques are employed. Specifically, closed form expressions are derived for the false alarm and detection probabilities, under three different scenarios: imperfect SIS with joint transmitter (TX) and receiver (RX) IQI, imperfect SIS and ideal TX/RX RF front-end, and perfect SIS and ideal TX/RX RF front-end. The derived analytical results are validated through extensive simulations, which reveal that IQI has a detrimental impact on the spectrum sensing performance of the FD CR transceiver, which brings significant losses in the spectrum utilization.

Telecommunication Systems, 2017

Several new attacks have been identified in CRNs such as primary user emulation, dynamic spectrum... more Several new attacks have been identified in CRNs such as primary user emulation, dynamic spectrum access (DSA), and jamming attacks. Such types of attacks can severely impact network performance, specially in terms of the over all achieved network throughput. In response to that, intrusion detection system (IDS) based on anomaly and signature detection is recognized as an effective candidate solution to handle and mitigate these types of attacks. In this paper, we present an intrusion detection system for CRNs (CR-IDS) using the anomaly-based detection (ABD) approach. The proposed ABD algorithm provides the ability to effectively detect the different types of CRNs security attacks. CR-IDS contains different cooperative components to accomplish its desired functionalities which are monitoring, feature generation and selection, rule generation, rule based system, detection module, action module, impact analysis and learning module. Our simulation results show that CR-IDS can detect DSA attacks with high detection rate and very low false negative and false positive probabilities.

European Journal of Engineering Education, 2013

This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Robust massive MIMO channel estimation for 5G networks using compressive sensing technique

AEU - International Journal of Electronics and Communications

Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions fo... more Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions for full-duplex (FD) cognitive radio (CR) devices. However, they are susceptible to radio frequency (RF) impairments, such as in-phase (I) and quadrature (Q) imbalance (IQI), which can significantly constrain the spectrum sensing capabilities. This paper is devoted to quantify and evaluate the effects of IQI in the context of spectrum sensing in FD CR systems, in which self-interference suppression (SIS) techniques are employed. Specifically, closed form expressions are derived for the false alarm and detection probabilities, under three different scenarios: imperfect SIS with joint transmitter (TX) and receiver (RX) IQI, imperfect SIS and ideal TX/RX RF front-end, and perfect SIS and ideal TX/RX RF front-end. The derived analytical results are validated through extensive simulations, which reveal that IQI has a detrimental impact on the spectrum sensing performance of the FD CR transceiver, which brings significant losses in the spectrum utilization.

Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions fo... more Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions for full-duplex (FD) cognitive radio networks (CRNs). However, they are susceptible to radio frequency (RF) impairments, such as in-phase (I) and quadrature (Q) imbalance (IQI), which can significantly limit the spectrum sensing capabilities. This paper is devoted to quantify and evaluate the effects of IQI in single-and multi-channel energy detectors operating in FD mode, under both cooperative and non-cooperative spectrum sensing scenarios. In this context, closed-form expressions are derived for the false alarm and detection probabilities in the general case, where partial self-interference suppression (SIS) and joint transmitter (TX) and receiver (RX) IQI, are considered. Furthermore, simplified closed-form expressions for the special cases, where either the RF front-end is ideal or the SIS technique is perfect, are also presented. The presented analytical results have been verified through extensive simulations and indicate that the IQI and partial SIS can significantly affect spectrum sensing accuracy in FD-based CRNs. Specifically, if ideal RF front-end is assumed, spectrum sensing error can significantly increase, leading to a reduction in the CRN performance and negatively affect the performance of primary (PR) networks. Hence, when designing spectrum sharing algorithms for FD-based CRNs, the hardware impairments should be considered in order to improve the CRN performance, while minimizing the negative effects on PR users.

Wavelength-division demultiplexing using graded-index planar structures

IEEE/OSA Journal of Lightwave Technology, 2006

ABSTRACT In this paper, the authors propose a novel technique for wavelength-division demultiplex... more ABSTRACT In this paper, the authors propose a novel technique for wavelength-division demultiplexing using a graded-index planar structure. The device consists of three layers of the same bulk material: The two outer layers are homogeneous media with refractive indices n1 and n2, while the inner layer is an inhomogeneous medium where its refractive index is graded according to a certain profile. The proposed technique exploits the spatial shift that results from the material dispersion found in dispersive media such as silicon dioxide (silica). It is found that the graded-index structure produces a spatial shift that is much higher than that encountered in conventional prisms, provided a certain refractive index profile is chosen. Unlike graded-index fibers, it is found that the value of α of the refractive index profile (α-profile) for the proposed device must be < 1 to get large spatial dispersion. A mathematical expression for the spatial shift between adjacent wavelengths is found by determining the path profiles followed by the different wavelengths as they propagate through the graded-index layer. Theoretically, it is found that any spatial shift can be obtained by either reducing the value of α far below 1 for a fixed size of the structure or increasing the size of the structure for a fixed value of α.

Mathematical and Computer Modelling, 2011

Cognitive radio (CR) is a revolutionary technology in wireless communications that enhances spect... more Cognitive radio (CR) is a revolutionary technology in wireless communications that enhances spectrum utilization by allowing opportunistic and dynamic spectrum access. One of the key challenges in this domain is how CR users cooperate to dynamically access the available spectrum opportunities in order to maximize the overall perceived throughput. In this paper, we consider the coordinated spectrum access problem in a multi-user single-transceiver CR network (CRN), where each CR user is equipped with only one half-duplex transceiver. We first formulate the dynamic spectrum access as a rate/power control and channel assignment optimization problem. Our objective is to maximize the sum-rate achieved by all contending CR users over all available spectrum opportunities under interference and hardware constraints. We first show that this problem can be formulated as a mixed integer nonlinear programming (MINLP) problem that is NP-hard, in general. By exploiting the fact that actual communication systems have a finite number of available channels, each with a given maximum transmission power, we transfer this MINLP into a binary linear programming problem (BLP). Due to its integrality nature, this BLP is expected to be NP-hard. However, we show that its constraint matrix satisfies the total unimodularity property, and hence our problem can be optimally solved in polynomial time using linear programming (LP). To execute the optimal assignment in a distributed manner, we then present a distributed CSMA/CA-based random access mechanism for CRNs. We compare the performance of our proposed mechanism with reference CSMA/CA channel access mechanisms designed for CRNs. Simulation results show that our proposed mechanism significantly improves the overall network throughput and preserves fairness.

Cross-layer Optimization of a CSMA Protocol with Adaptive Modulation for Improved Energy Efficiency in Wireless Sensor Networks

We investigate the energy efficiency in a wireless sensor networks that implements a non-persiste... more We investigate the energy efficiency in a wireless sensor networks that implements a non-persistent CSMA MAC protocol with adaptive MQAM modulation at the physical layer. The system throughput is estimated based on the number of received ACK packets. The backoff probability at the MAC layer and the modulation order at the physical layer are jointly adapted according to the traffic dynamics, leading to improved system energy efficiency while satisfying a given constraint on the packet retransmission delay. Through numerical examples and simulations, we verify the significant energy-efficiency improvements achieved by this joint optimization compared to the backoff- probability-only and the modulation-order-only adaptations.

In this paper, we consider the coordinated spectrum access problem in a multiuser single-transcei... more In this paper, we consider the coordinated spectrum access problem in a multiuser single-transceiver cognitive radio network (CRN). Our objective is to maximize the sum-rate achieved by all contending cognitive radio users with respect to both spectrum assignment and transmission rate. The problem is posed as a rate-maximization problem subject to hardware and interference constraints. Specifically, we show that this problem can be formulated as an integer linear programming problem (ILP) with unimodular constraint matrix, which can be optimally solved in polynomial time using linear programming. Unlike previous research, our formulation is not restricted to the information-theoretic capacity, and can be applied to any arbitrarily given rate-SINR function. We also develop a distributed CSMA/CA-based MAC protocol for CRNs to realize the optimal assignment in a distributed manner. Simulation results indicate that compared to a reference CSMA/CA CRN MAC protocol, the proposed protocol significantly improves network throughput and preserves fairness.

Several spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed... more Several spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed assuming no adjacent-channel interference (i.e., no interference from neighboring CR transmissions operating over adjacent channels). However, in practice, such an assumption may not hold, and guard bands are realistically needed to prevent interference from neighboring CR transmissions operating on adjacent channels. Introducing guard bands is a restrictive constraint on the effective use of the spectrum. In this work, we investigate the problem of assigning channels/powers to CR transmissions, while accounting for such a constraint. To improve spectrum efficiency and avoid unnecessary blocking of CR transmissions, we propose a novel guard-band-aware channel assignment scheme. The proposed scheme reduces the number of required guard channels for a given transmission by exploiting the benefits of utilizing adjacent channels while considering the already reserved guard channels. We analytically formulate the channel access as a joint power control and channel assignment optimization problem, with the objective of minimizing the required spectrum resource for a given CR transmission. Because the optimization problem is found to be a binary linear program (BLP), which is known to be NP-hard in general, we present a near-optimal algorithm to solve this problem based on a sequential fixing procedure, where the binary variables are determined iteratively by solving a sequence of linear programs. Simulation results are provided, which verify the accuracy of the proposed algorithm and demonstrate the significant gain achieved by being guard-band-aware.

Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization thr... more Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization through opportunistic on-demand access. Many spectrum access/sharing algorithms for CR networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption may not hold due to hardware cost. In this paper, we address the problem of assigning channels to CR transmissions, assuming one transceiver per CR. The primary goal of our design is to maximize the number of simultaneous CR transmissions with respect to both spectrum assignment and transmission power. Energy conservation is also treated, but as a secondary objective. The problem is posed as a utility maximization problem subject to target rate demand and interference constraints. For multi-transceiver CRNs, this optimization problem is known to be NP-hard. However, under the practical setting of a single transceiver per CR user, we show that this problem can be optimally solved in polynomial time. Specifically, we present a centralized algorithm for the channel assignment problem based on bipartite matching. We then integrate this algorithm into distributed MAC protocols. First, we consider a single-hop CRN, for which we introduce a CSMA-like MAC protocol that uses an access window (AW) for exchanging control information prior to data transmissions. This approach allows us to realize a centralized algorithm in a distributed manner.

Quality and availability-aware spectrum sharing for improved packet delivery in spectrum-agile networks

In this paper, we propose a novel CRN MAC, called MAX-PS-MAC. MAX-PS-MAC uses a probabilistic cha... more In this paper, we propose a novel CRN MAC, called MAX-PS-MAC. MAX-PS-MAC uses a probabilistic channel assignment mechanism that attempts at maximizing the packet success probability of each transmission by exploiting statistical information regarding availability durations and link quality conditions of idle channels. While most of previously proposed CRN MAC protocols account for PR channel dynamics by requiring communicating CR users to consistently perform dynamic channel switching according to PR activities, MAX-PS-MAC avoids the significant overhead and delay of channel switching by providing communicating CR users with the idle channel that provides the highest probability of success. Simulation results indicate that compared to typical CRN MAC protocols, MAX-PS-MAC significantly reduces the forced-termination rate of CR transmissions, which consequently improves network throughput by up to 110%.

Opportunistic Routing in Cognitive Radio Networks: Exploiting Spectrum Availability and Rich Channel Diversity

Designing an appropriate routing metric in cognitive radio networks (CRNs) is a challenging probl... more Designing an appropriate routing metric in cognitive radio networks (CRNs) is a challenging problem. In a multi-hop CRN, both spectrum handoff (quantified by channel availability time) and required transmission time can significantly impact network connectivity and routing. Specifically, spectrum handoff can cause a significant degradation in CRN performance when the availability time of an assigned channel is smaller than the required transmission time over that channel. In this case, the percentage of CR transmissions that will be terminated due to primary user (PU) activities, can significantly increase, leading to a reduction in network throughput. To reduce the percentage of terminated CR transmissions, we introduce a novel routing metric that jointly considers spectrum availability time and required CR transmission time. Based on this metric, we propose a probabilistic routing algorithm for multi-hop CRNs that attempts at computing the path with the maximum probability of success from a given source to its destination (including the channel assignment along that path). Simulation results show that our proposed algorithm leads to a significant performance improvement over two reference algorithms presented in this paper.

Many spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed as... more Many spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption may not hold due to hardware cost. In this paper, we address the problem of assigning channels to CR transmissions, assuming one transceiver per CR. The primary goal of our design is to maximize the number of feasible concurrent CR transmissions with respect to both spectrum assignment and transmission power. Energy conservation is also treated, but as a secondary objective. The problem is posed as a utility maximization problem subject to target rate demand and interference constraints. For multi-transceiver CRNs, this optimization problem is known to be NP-hard. However, under the practical setting of a single transceiver per CR user, we show that this problem can be optimally solved in polynomial time. Specifically, we present a centralized algorithm for the channel assignment problem based on bipartite matching. We then integrate this algorithm into distributed MAC protocols. First, we consider a single-hop CRN, for which we introduce a CSMA-like MAC protocol that uses an access window (AW) for exchanging control information prior to data transmissions. This approach allows us to realize a centralized algorithm in a distributed manner. We then develop a distributed MAC protocol (WFC-MAC) for a multi-hop CRN. WFC-MAC improves the CRN throughput through a novel distributed channel assignment that relies only on information provided by the two communicating users. We compare the performance of our schemes with CSMA/CA variants. The results show that our schemes significantly decrease the blocking rate of CR transmissions, and hence improves the network throughput.

Adaptive power-controlled MAC protocols for improved throughput in hardware-constrained cognitive radio networks

Ad Hoc Networks, 2011

Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization thr... more Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization through opportunistic on-demand access. Many MAC protocols for cognitive radio networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption comes at the cost of extra hardware. In this paper, we address the problem of assigning channels to CR transmissions in single-hop and multi-hop CRNs, assuming one transceiver per CR. The primary goal of our design is to maximize the number of feasible concurrent CR transmissions, and conserve energy as a secondary objective, with respect to both spectrum assignment and transmission power subject to interference constraint and user rate demands. The problem is formulated under both binary-level and multi-level spectrum opportunity frameworks. Our formulation applies to any power-rate relationship. For single-hop CRNs, a centralized polynomial-time algorithm based on bipartite matching that computes the optimal channel assignment is developed. We then integrate this algorithm into distributed MAC protocols that preserve fairness. For multi-hop ad hoc CRNs, we propose a novel distributed MAC protocol (WFC-MAC) that attempts to maximize the CRN throughput, assuming single transceiver radios but with “dual-receive” capability. WFC-MAC uses a cooperative assignment that relies only on information provided by the two communicating users. The main novelty in WFC-MAC lies in requiring no active coordination with licensed users and exploiting the dual-receive capability of radios, thus alleviating various channel access problems that are common to multi-channel designs. We conduct theoretical analysis of our MAC protocols, and study their performance via simulations. The results indicate that compared with CSMA/CA variants, our protocols significantly decrease the blocking rate of CR transmissions, and hence improve network throughput.

IEEE/ACM Transactions on Networking, 2010

The cognitive radio (CR) paradigm calls for open spectrum access according to a predetermined eti... more The cognitive radio (CR) paradigm calls for open spectrum access according to a predetermined etiquette. Under this paradigm, CR nodes access the spectrum opportunistically by continuously monitoring the operating channels. A key challenge in this domain is how the nodes in a CR network (CRN) cooperate to access the medium in order to maximize the CRN throughput. Typical multi-channel MAC protocols assume that frequency channels are adjacent and that there are no constraints on the transmission power. However, a CRN may operate over a wide range of frequencies, and a power mask is often enforced on the transmission of a CR user to avoid corrupting the transmissions of spectrum-licensed primary-radio (PR) users. To avoid unnecessary blocking of CR transmissions, we propose a novel distance-dependent MAC protocol for CRNs. Our protocol, called DDMAC, attempts to maximize the CRN throughput. It uses a novel probabilistic channel assignment mechanism that exploits the dependence between the signal's attenuation model and the transmission distance while considering the traffic profile. DDMAC allows a pair of CR users to communicate on a channel that may not be optimal from one user's perspective, but that allows more concurrent transmissions to take place, especially under moderate and high traffic loads. Simulation results indicate that compared to typical multi-channel CSMA-based protocols, DDMAC reduces the blocking rate of CR requests by up to 30%, which consequently improves the network throughput.

IEEE Access

Dynamic Spectrum Access (DSA) technology in wireless Cognitive Radio Networks (CRNs) provides opp... more Dynamic Spectrum Access (DSA) technology in wireless Cognitive Radio Networks (CRNs) provides opportunistic access for unlicensed users, also known as Secondary Users (SUs), which can offer huge bandwidth to enable future wireless communication. Mainly, this technology aims to improve the endto-end throughput by allowing SUs to exploit the licensed channels only when their licensed users, also known as Primary Users (PUs), are not using them. Most existing communication protocols designed for CRNs are based on the assumption that the channel availability time is considered based on a memoryless distribution for PUs arrivals. Unfortunately, this assumption is impractical because the PU channels' activity and availability are memory-time correlated. Worse yet, designing communication protocols for CRNs under this assumption can result in overestimating the Probability of Success (PoS) for SU packet transmissions, resulting in severe degradation in network performance in realistic scenarios. This paper derives a closed-form formula under memory-time correlation for channel availability that quantifies the PoS for SUs' packet transmission in CRNs. This will empower the network designers to get practical expectations about network efficiency rather than the overestimated PoS. Therefore, this work is also useful for emerging wireless networks with multi-hop routing, such as 5G, 6G, vehicular networks, etc., which incorporate DSA techniques. Our numerical and simulation results demonstrate that the PoS is overestimated in most of the literature due to adopting memoryless-based distribution in modeling channels' availability; such overestimation can impact communication protocol decisions, resulting in severe network performance degradation.

AEU - International Journal of Electronics and Communications, 2020

The pilot overhead provides fundamental limits on the performance of massive multiple-input multi... more The pilot overhead provides fundamental limits on the performance of massive multiple-input multipleoutput (MIMO) systems. This is because the performance of such systems is based on the failure of the presentation of accurate channel state information (CSI). Based on the theory of compressive sensing, this paper presents a novel channel estimation technique as the mean of minimizing the problems associated with pilot overhead. The proposed technique is based on the combination of the compressive sampling matching and sparsity adaptive matching pursuit techniques. The sources of the signals in MIMO systems are sparsely distributed in terms of spatial correlations. This distribution pattern enables then use of compressive sampling techniques to solve the channel estimation problem in MIMO systems. Simulation results demonstrate that the proposed channel estimation outperforms the conventional compressive sensing (CS)-based channel estimation algorithms in terms of the normalized mean square error (NMSE) performance at high signal-to-noise ratios (SNRs). Furthermore, it reduces the computational complexity of the channel estimation compared to conventional methods. In addition to the achieved performance gain in terms of NMSE, the presented method significantly reduces pilot overhead compared to conventional channel estimation techniques.

International Journal of Electrical and Computer Engineering (IJECE), 2020

Several wireless technologies have recently emerged to enable efficient and scalable internet-of-... more Several wireless technologies have recently emerged to enable efficient and scalable internet-of-things (IoT) networking. Cognitive radio (CR) technology, enabled by software-defined radios, is considered one of the main IoT-enabling technologies that can provide opportunistic wireless access to a large number of connected IoT devices. An important challenge in this domain is how to dynamically enable IoT transmissions while achieving efficient spectrum usage with a minimum total power consumption under interference and traffic demand uncertainty. Toward this end, we propose a dynamic bandwidth/channel/power allocation algorithm that aims at maximizing the overall network’s throughput while selecting the set of power resulting in the minimum total transmission power. This problem can be formulated as a two-stage binary linear stochastic programming. Because the interference over different channels is a continuous random variable and noting that the interference statistics are highly...

2016 IEEE Wireless Communications and Networking Conference, 2016

Direct-conversion radio transceivers can offer reprogrammable and low-cost hardware solutions for... more Direct-conversion radio transceivers can offer reprogrammable and low-cost hardware solutions for full-duplex (FD) cognitive radio (CR) devices. However, they are susceptible to radio frequency (RF) impairments, such as in-phase (I) and quadrature (Q) imbalance (IQI), which can significantly constrain the spectrum sensing capabilities. This paper is devoted to quantify and evaluate the effects of IQI in the context of spectrum sensing in FD CR systems, in which self-interference suppression (SIS) techniques are employed. Specifically, closed form expressions are derived for the false alarm and detection probabilities, under three different scenarios: imperfect SIS with joint transmitter (TX) and receiver (RX) IQI, imperfect SIS and ideal TX/RX RF front-end, and perfect SIS and ideal TX/RX RF front-end. The derived analytical results are validated through extensive simulations, which reveal that IQI has a detrimental impact on the spectrum sensing performance of the FD CR transceiver, which brings significant losses in the spectrum utilization.

Telecommunication Systems, 2017

Several new attacks have been identified in CRNs such as primary user emulation, dynamic spectrum... more Several new attacks have been identified in CRNs such as primary user emulation, dynamic spectrum access (DSA), and jamming attacks. Such types of attacks can severely impact network performance, specially in terms of the over all achieved network throughput. In response to that, intrusion detection system (IDS) based on anomaly and signature detection is recognized as an effective candidate solution to handle and mitigate these types of attacks. In this paper, we present an intrusion detection system for CRNs (CR-IDS) using the anomaly-based detection (ABD) approach. The proposed ABD algorithm provides the ability to effectively detect the different types of CRNs security attacks. CR-IDS contains different cooperative components to accomplish its desired functionalities which are monitoring, feature generation and selection, rule generation, rule based system, detection module, action module, impact analysis and learning module. Our simulation results show that CR-IDS can detect DSA attacks with high detection rate and very low false negative and false positive probabilities.

European Journal of Engineering Education, 2013

This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Robust massive MIMO channel estimation for 5G networks using compressive sensing technique

AEU - International Journal of Electronics and Communications

Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions fo... more Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions for full-duplex (FD) cognitive radio (CR) devices. However, they are susceptible to radio frequency (RF) impairments, such as in-phase (I) and quadrature (Q) imbalance (IQI), which can significantly constrain the spectrum sensing capabilities. This paper is devoted to quantify and evaluate the effects of IQI in the context of spectrum sensing in FD CR systems, in which self-interference suppression (SIS) techniques are employed. Specifically, closed form expressions are derived for the false alarm and detection probabilities, under three different scenarios: imperfect SIS with joint transmitter (TX) and receiver (RX) IQI, imperfect SIS and ideal TX/RX RF front-end, and perfect SIS and ideal TX/RX RF front-end. The derived analytical results are validated through extensive simulations, which reveal that IQI has a detrimental impact on the spectrum sensing performance of the FD CR transceiver, which brings significant losses in the spectrum utilization.

Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions fo... more Direct-conversion radio transceivers can offer re-programmable and low-cost hardware solutions for full-duplex (FD) cognitive radio networks (CRNs). However, they are susceptible to radio frequency (RF) impairments, such as in-phase (I) and quadrature (Q) imbalance (IQI), which can significantly limit the spectrum sensing capabilities. This paper is devoted to quantify and evaluate the effects of IQI in single-and multi-channel energy detectors operating in FD mode, under both cooperative and non-cooperative spectrum sensing scenarios. In this context, closed-form expressions are derived for the false alarm and detection probabilities in the general case, where partial self-interference suppression (SIS) and joint transmitter (TX) and receiver (RX) IQI, are considered. Furthermore, simplified closed-form expressions for the special cases, where either the RF front-end is ideal or the SIS technique is perfect, are also presented. The presented analytical results have been verified through extensive simulations and indicate that the IQI and partial SIS can significantly affect spectrum sensing accuracy in FD-based CRNs. Specifically, if ideal RF front-end is assumed, spectrum sensing error can significantly increase, leading to a reduction in the CRN performance and negatively affect the performance of primary (PR) networks. Hence, when designing spectrum sharing algorithms for FD-based CRNs, the hardware impairments should be considered in order to improve the CRN performance, while minimizing the negative effects on PR users.

Wavelength-division demultiplexing using graded-index planar structures

IEEE/OSA Journal of Lightwave Technology, 2006

ABSTRACT In this paper, the authors propose a novel technique for wavelength-division demultiplex... more ABSTRACT In this paper, the authors propose a novel technique for wavelength-division demultiplexing using a graded-index planar structure. The device consists of three layers of the same bulk material: The two outer layers are homogeneous media with refractive indices n1 and n2, while the inner layer is an inhomogeneous medium where its refractive index is graded according to a certain profile. The proposed technique exploits the spatial shift that results from the material dispersion found in dispersive media such as silicon dioxide (silica). It is found that the graded-index structure produces a spatial shift that is much higher than that encountered in conventional prisms, provided a certain refractive index profile is chosen. Unlike graded-index fibers, it is found that the value of α of the refractive index profile (α-profile) for the proposed device must be < 1 to get large spatial dispersion. A mathematical expression for the spatial shift between adjacent wavelengths is found by determining the path profiles followed by the different wavelengths as they propagate through the graded-index layer. Theoretically, it is found that any spatial shift can be obtained by either reducing the value of α far below 1 for a fixed size of the structure or increasing the size of the structure for a fixed value of α.

Mathematical and Computer Modelling, 2011

Cognitive radio (CR) is a revolutionary technology in wireless communications that enhances spect... more Cognitive radio (CR) is a revolutionary technology in wireless communications that enhances spectrum utilization by allowing opportunistic and dynamic spectrum access. One of the key challenges in this domain is how CR users cooperate to dynamically access the available spectrum opportunities in order to maximize the overall perceived throughput. In this paper, we consider the coordinated spectrum access problem in a multi-user single-transceiver CR network (CRN), where each CR user is equipped with only one half-duplex transceiver. We first formulate the dynamic spectrum access as a rate/power control and channel assignment optimization problem. Our objective is to maximize the sum-rate achieved by all contending CR users over all available spectrum opportunities under interference and hardware constraints. We first show that this problem can be formulated as a mixed integer nonlinear programming (MINLP) problem that is NP-hard, in general. By exploiting the fact that actual communication systems have a finite number of available channels, each with a given maximum transmission power, we transfer this MINLP into a binary linear programming problem (BLP). Due to its integrality nature, this BLP is expected to be NP-hard. However, we show that its constraint matrix satisfies the total unimodularity property, and hence our problem can be optimally solved in polynomial time using linear programming (LP). To execute the optimal assignment in a distributed manner, we then present a distributed CSMA/CA-based random access mechanism for CRNs. We compare the performance of our proposed mechanism with reference CSMA/CA channel access mechanisms designed for CRNs. Simulation results show that our proposed mechanism significantly improves the overall network throughput and preserves fairness.

Cross-layer Optimization of a CSMA Protocol with Adaptive Modulation for Improved Energy Efficiency in Wireless Sensor Networks

We investigate the energy efficiency in a wireless sensor networks that implements a non-persiste... more We investigate the energy efficiency in a wireless sensor networks that implements a non-persistent CSMA MAC protocol with adaptive MQAM modulation at the physical layer. The system throughput is estimated based on the number of received ACK packets. The backoff probability at the MAC layer and the modulation order at the physical layer are jointly adapted according to the traffic dynamics, leading to improved system energy efficiency while satisfying a given constraint on the packet retransmission delay. Through numerical examples and simulations, we verify the significant energy-efficiency improvements achieved by this joint optimization compared to the backoff- probability-only and the modulation-order-only adaptations.

In this paper, we consider the coordinated spectrum access problem in a multiuser single-transcei... more In this paper, we consider the coordinated spectrum access problem in a multiuser single-transceiver cognitive radio network (CRN). Our objective is to maximize the sum-rate achieved by all contending cognitive radio users with respect to both spectrum assignment and transmission rate. The problem is posed as a rate-maximization problem subject to hardware and interference constraints. Specifically, we show that this problem can be formulated as an integer linear programming problem (ILP) with unimodular constraint matrix, which can be optimally solved in polynomial time using linear programming. Unlike previous research, our formulation is not restricted to the information-theoretic capacity, and can be applied to any arbitrarily given rate-SINR function. We also develop a distributed CSMA/CA-based MAC protocol for CRNs to realize the optimal assignment in a distributed manner. Simulation results indicate that compared to a reference CSMA/CA CRN MAC protocol, the proposed protocol significantly improves network throughput and preserves fairness.

Several spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed... more Several spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed assuming no adjacent-channel interference (i.e., no interference from neighboring CR transmissions operating over adjacent channels). However, in practice, such an assumption may not hold, and guard bands are realistically needed to prevent interference from neighboring CR transmissions operating on adjacent channels. Introducing guard bands is a restrictive constraint on the effective use of the spectrum. In this work, we investigate the problem of assigning channels/powers to CR transmissions, while accounting for such a constraint. To improve spectrum efficiency and avoid unnecessary blocking of CR transmissions, we propose a novel guard-band-aware channel assignment scheme. The proposed scheme reduces the number of required guard channels for a given transmission by exploiting the benefits of utilizing adjacent channels while considering the already reserved guard channels. We analytically formulate the channel access as a joint power control and channel assignment optimization problem, with the objective of minimizing the required spectrum resource for a given CR transmission. Because the optimization problem is found to be a binary linear program (BLP), which is known to be NP-hard in general, we present a near-optimal algorithm to solve this problem based on a sequential fixing procedure, where the binary variables are determined iteratively by solving a sequence of linear programs. Simulation results are provided, which verify the accuracy of the proposed algorithm and demonstrate the significant gain achieved by being guard-band-aware.

Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization thr... more Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization through opportunistic on-demand access. Many spectrum access/sharing algorithms for CR networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption may not hold due to hardware cost. In this paper, we address the problem of assigning channels to CR transmissions, assuming one transceiver per CR. The primary goal of our design is to maximize the number of simultaneous CR transmissions with respect to both spectrum assignment and transmission power. Energy conservation is also treated, but as a secondary objective. The problem is posed as a utility maximization problem subject to target rate demand and interference constraints. For multi-transceiver CRNs, this optimization problem is known to be NP-hard. However, under the practical setting of a single transceiver per CR user, we show that this problem can be optimally solved in polynomial time. Specifically, we present a centralized algorithm for the channel assignment problem based on bipartite matching. We then integrate this algorithm into distributed MAC protocols. First, we consider a single-hop CRN, for which we introduce a CSMA-like MAC protocol that uses an access window (AW) for exchanging control information prior to data transmissions. This approach allows us to realize a centralized algorithm in a distributed manner.

Quality and availability-aware spectrum sharing for improved packet delivery in spectrum-agile networks

In this paper, we propose a novel CRN MAC, called MAX-PS-MAC. MAX-PS-MAC uses a probabilistic cha... more In this paper, we propose a novel CRN MAC, called MAX-PS-MAC. MAX-PS-MAC uses a probabilistic channel assignment mechanism that attempts at maximizing the packet success probability of each transmission by exploiting statistical information regarding availability durations and link quality conditions of idle channels. While most of previously proposed CRN MAC protocols account for PR channel dynamics by requiring communicating CR users to consistently perform dynamic channel switching according to PR activities, MAX-PS-MAC avoids the significant overhead and delay of channel switching by providing communicating CR users with the idle channel that provides the highest probability of success. Simulation results indicate that compared to typical CRN MAC protocols, MAX-PS-MAC significantly reduces the forced-termination rate of CR transmissions, which consequently improves network throughput by up to 110%.

Opportunistic Routing in Cognitive Radio Networks: Exploiting Spectrum Availability and Rich Channel Diversity

Designing an appropriate routing metric in cognitive radio networks (CRNs) is a challenging probl... more Designing an appropriate routing metric in cognitive radio networks (CRNs) is a challenging problem. In a multi-hop CRN, both spectrum handoff (quantified by channel availability time) and required transmission time can significantly impact network connectivity and routing. Specifically, spectrum handoff can cause a significant degradation in CRN performance when the availability time of an assigned channel is smaller than the required transmission time over that channel. In this case, the percentage of CR transmissions that will be terminated due to primary user (PU) activities, can significantly increase, leading to a reduction in network throughput. To reduce the percentage of terminated CR transmissions, we introduce a novel routing metric that jointly considers spectrum availability time and required CR transmission time. Based on this metric, we propose a probabilistic routing algorithm for multi-hop CRNs that attempts at computing the path with the maximum probability of success from a given source to its destination (including the channel assignment along that path). Simulation results show that our proposed algorithm leads to a significant performance improvement over two reference algorithms presented in this paper.

Many spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed as... more Many spectrum access/sharing algorithms for cognitive radio networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption may not hold due to hardware cost. In this paper, we address the problem of assigning channels to CR transmissions, assuming one transceiver per CR. The primary goal of our design is to maximize the number of feasible concurrent CR transmissions with respect to both spectrum assignment and transmission power. Energy conservation is also treated, but as a secondary objective. The problem is posed as a utility maximization problem subject to target rate demand and interference constraints. For multi-transceiver CRNs, this optimization problem is known to be NP-hard. However, under the practical setting of a single transceiver per CR user, we show that this problem can be optimally solved in polynomial time. Specifically, we present a centralized algorithm for the channel assignment problem based on bipartite matching. We then integrate this algorithm into distributed MAC protocols. First, we consider a single-hop CRN, for which we introduce a CSMA-like MAC protocol that uses an access window (AW) for exchanging control information prior to data transmissions. This approach allows us to realize a centralized algorithm in a distributed manner. We then develop a distributed MAC protocol (WFC-MAC) for a multi-hop CRN. WFC-MAC improves the CRN throughput through a novel distributed channel assignment that relies only on information provided by the two communicating users. We compare the performance of our schemes with CSMA/CA variants. The results show that our schemes significantly decrease the blocking rate of CR transmissions, and hence improves the network throughput.

Adaptive power-controlled MAC protocols for improved throughput in hardware-constrained cognitive radio networks

Ad Hoc Networks, 2011

Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization thr... more Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization through opportunistic on-demand access. Many MAC protocols for cognitive radio networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption comes at the cost of extra hardware. In this paper, we address the problem of assigning channels to CR transmissions in single-hop and multi-hop CRNs, assuming one transceiver per CR. The primary goal of our design is to maximize the number of feasible concurrent CR transmissions, and conserve energy as a secondary objective, with respect to both spectrum assignment and transmission power subject to interference constraint and user rate demands. The problem is formulated under both binary-level and multi-level spectrum opportunity frameworks. Our formulation applies to any power-rate relationship. For single-hop CRNs, a centralized polynomial-time algorithm based on bipartite matching that computes the optimal channel assignment is developed. We then integrate this algorithm into distributed MAC protocols that preserve fairness. For multi-hop ad hoc CRNs, we propose a novel distributed MAC protocol (WFC-MAC) that attempts to maximize the CRN throughput, assuming single transceiver radios but with “dual-receive” capability. WFC-MAC uses a cooperative assignment that relies only on information provided by the two communicating users. The main novelty in WFC-MAC lies in requiring no active coordination with licensed users and exploiting the dual-receive capability of radios, thus alleviating various channel access problems that are common to multi-channel designs. We conduct theoretical analysis of our MAC protocols, and study their performance via simulations. The results indicate that compared with CSMA/CA variants, our protocols significantly decrease the blocking rate of CR transmissions, and hence improve network throughput.

IEEE/ACM Transactions on Networking, 2010

The cognitive radio (CR) paradigm calls for open spectrum access according to a predetermined eti... more The cognitive radio (CR) paradigm calls for open spectrum access according to a predetermined etiquette. Under this paradigm, CR nodes access the spectrum opportunistically by continuously monitoring the operating channels. A key challenge in this domain is how the nodes in a CR network (CRN) cooperate to access the medium in order to maximize the CRN throughput. Typical multi-channel MAC protocols assume that frequency channels are adjacent and that there are no constraints on the transmission power. However, a CRN may operate over a wide range of frequencies, and a power mask is often enforced on the transmission of a CR user to avoid corrupting the transmissions of spectrum-licensed primary-radio (PR) users. To avoid unnecessary blocking of CR transmissions, we propose a novel distance-dependent MAC protocol for CRNs. Our protocol, called DDMAC, attempts to maximize the CRN throughput. It uses a novel probabilistic channel assignment mechanism that exploits the dependence between the signal's attenuation model and the transmission distance while considering the traffic profile. DDMAC allows a pair of CR users to communicate on a channel that may not be optimal from one user's perspective, but that allows more concurrent transmissions to take place, especially under moderate and high traffic loads. Simulation results indicate that compared to typical multi-channel CSMA-based protocols, DDMAC reduces the blocking rate of CR requests by up to 30%, which consequently improves the network throughput.