Showing papers by "Mohsen Guizani published in 2013"

Securing vehicle-to-grid communications in the smart grid

Abstract: Using vehicle-to-grid (V2G) services, battery vehicles (BVs) may help the smart grid alleviate peaks in power consumption. However, wireless communications infrastructure between BVs and the smart grid also introduce severe and unprecedented security vulnerabilities. In this article, we discuss V2G network architectures and present state-of-the-art security, including different security challenges during V2G power and communications interactions. Then we report on our context-aware authentication solution for V2G communications in the smart grid. Finally, we describe several open issues for secure V2G networks.

Resource Allocation with Incomplete Information for QoE-Driven Multimedia Communications

Abstract: Most existing Quality of Experience (QoE)-driven multimedia resource allocation methods assume that the QoE model of each user is known to the controller before the start of the multimedia playout. However, this assumption may be invalid in many practical scenarios. In this paper, we address the resource allocation problem with incomplete information where the realized mean opinion score (MOS) can only be observed over time, but the underlying QoE model and playout time are unknown. We consider two variants of this problem: 1) the form of the QoE model is known but the parameters are unknown; 2) both the form and the parameters of the QoE model are unknown. For both cases, we develop dynamic resource allocation schemes based on online test-optimization strategy. Simply speaking, one first spends appropriate time on testing the QoE model, then optimizes the sum of the MOS in the remaining playout time. The highlight of this paper lies in resolving the inherent tension between the test and optimization by jointly considering the uncertainties of QoE model and playout time. Furthermore, we derive tight bounds on the MOS loss incurred by the proposed schemes in comparison with the optimal scheme that knows the QoE model a priori and prove that the performance gap, as the playout time tends to infinity, asymptotically shrinks to zero.

Battery Status-aware Authentication Scheme for V2G Networks in Smart Grid

Abstract: Vehicle-to-grid (V2G) is emerging as an attractive paradigm in smart grid, and provides power and information services by periodically collecting power status of battery vehicles (BVs). During a BV's interaction with power grid, it may be in one of the following states: charging, fully-charged (FC), and discharging. In this paper, we identify that there are unique security challenges in a BV's different battery states. Accordingly, we propose a battery status-aware authentication scheme (BASA) to address the issue for V2G networks. In BASA, 1) an aggregated-identifier is proposed during the charging-to-FC state transition to ensure that BVs can be authenticated without disclosing their real identities; 2) selective disclosure based challenge-response authentication is presented during the FC-to-discharging phase to realize anonymous data transmission; 3) an aggregated-status is reported during the discharging-to-charging transition in order to hide a BV's power level from an aggregator. In addition, we perform comprehensive security analysis, which shows that BASA achieves both privacy preservation and security protection during battery state transitions. The analysis also indicates that battery status awareness is crucial for BVs' secure operations for V2G networks in smart grid.

Capacity and Delay Analysis for Data Gathering with Compressive Sensing in Wireless Sensor Networks

Abstract: Compressive sensing (CS) provides a new paradigm for efficient data gathering in wireless sensor networks (WSNs). In this paper, with the assumption that sensor data is sparse we apply the theory of CS to data gathering for a WSN where n nodes are randomly deployed. We investigate the fundamental limitation of data gathering with CS for both single-sink and multi-sink random networks under protocol interference model, in terms of capacity and delay. For the single-sink case, we present a simple scheme for data gathering with CS and derive the bounds of the data gathering capacity. We show that the proposed scheme can achieve the capacity Θ(\frac{nW}{M}) and the delay Θ(M\sqrtfrac{nlog n}), where W is the data rate on each link and M is the number of random projections required for reconstructing a snapshot. The results show that the proposed scheme can achieve a capacity gain of Θ (\frac{n}{M}) over the baseline transmission scheme and the delay can also be reduced by a factor of Θ(\fracsqrt{n\log n}{M}). For the multi-sink case, we consider the scenario where n_d sinks are present in the network and each sink collects one random projection from n_s randomly selected source nodes. We construct a simple architecture for multi-session data gathering with CS. We show that the per-session capacity of data gathering with CS is Θ(\frac{n\sqrt{n}W}{M n_d \sqrt{n_s \log n}}) and the per-session delay is Θ(M\sqrtfrac{{n}{log n}}). Finally, we validate our theoretical results for the scaling laws of the capacity in both single-sink and multi-sink networks through simulations.

Securing Cognitive Radio Networks against Primary User Emulation Attacks

Abstract: Cognitive Radio (CR) is a promising technology for next-generation wireless networks in order to efficiently utilize the limited spectrum resources and satisfy the rapidly increasing demand for wireless applications and services. Security is a very important but not well addressed issue in CR networks. In this paper we focus on security problems arising from Primary User Emulation (PUE) attacks in CR networks. We present a comprehensive introduction to PUE attacks, from the attacking rationale and its impact on CR networks, to detection and defense approaches. In order to secure CR networks against PUE attacks, a two-level database-assisted detection approach is proposed to detect such attacks. Energy detection and location verification are combined for fast and reliable detection. An admission control based defense approach is proposed to mitigate the performance degradation of a CR network under a PUE attack. Illustrative results are presented to demonstrate the effectiveness of the proposed detection and defense approaches.

Exploring blind online scheduling for mobile cloud multimedia services

Abstract: Mobile cloud is a new emerging technology which can be used to enable users to enjoy abundant multimedia applications in a pervasive computing environment. Therefore, the scheduling of massive multimedia flows with heterogeneous QoS guarantees becomes an important issue for the mobile cloud. Generally, the predominant popular cloud-based scheduling algorithms assume that the request rate and service time, are available for the system operator. However, this assumption can hardly be maintained in many practical scenarios, especially for the largescale mobile cloud. In this article, we consider the scheduling problem for a practical mobile cloud in which the above parameters are unavailable and unknown. Taking into account the performance of the users and the impartial free time among the servers, the highlight of this article lies in proposing a blind online scheduling algorithm (BOSA). Specifically, we assign available multimedia servers based on the last timeslot information of the users' requests, and route all the multimedia flows according to the first-come- first-served rule. Moreover, we design detailed steps to apply the BOSA to a content recommendation system, and show that the proposed BOSA can achieve asymptotic optimality.

A survey on communication infrastructure for micro-grids

Abstract: A micro-grid is a small scale power supply network that is designed to provide electricity to a small community with its own renewable energy sources. Due to distributed generation variability, security and load sharing issues, an efficient communication infrastructure is necessary between its agents (load, generation and storage units). Numerous research efforts are being developed to come up with such communication techniques that can overcome the barriers to implement the concept of micro-grids. This paper covers the features, characteristics and challenges of micro-grids and their associated communication techniques.

Secure Data Discovery and Dissemination based on Hash Tree for Wireless Sensor Networks

Abstract: Wireless sensor networks (WSNs) are widely applicable in monitoring and control of environment parameters. It is sometimes necessary to disseminate data through wireless links after they are deployed in order to adjust configuration parameters of sensors or distribute management commands and queries to sensors. Several approaches have been proposed recently for data discovery and dissemination in WSNs. However, they all focus on how to ensure reliability and usually overlook security vulnerabilities. This paper identifies the security vulnerabilities in data discovery and dissemination when used in WSNs. Such vulnerabilities allow an adversary to update a network with undesirable values, erase critical variables, or launch denial-of-service (DoS) attacks. To address these vulnerabilities, this paper presents the design, implementation, and evaluation of a secure, lightweight, and DoS-resistant data discovery and dissemination protocol named SeDrip for WSNs. Our protocol takes into consideration the limited resources of sensor nodes, packet loss and out-of-sequence packet delivery. Also, it can provide instantaneous authentication without packet buffering delay, and tolerate node compromise. Besides the theoretical analysis that demonstrates the security and performance of SeDrip, this paper also reports the experimental evaluation of SeDrip in a network of resource-limited sensor nodes, which shows its efficiency in practice.

Incentive Scheduler Algorithm for Cooperation and Coverage Extension in Wireless Networks

Abstract: In this paper, we focus on wireless coverage extension and nodes' cooperation. We propose a new protocol based on an incentive approach and a scheduling algorithm to reward cooperative nodes. The cost of cooperation can be prohibitively expensive in terms of quality of service (QoS) and energy consumption, which does not motivate some nodes to cooperate. Therefore, we introduce a percentage of cooperation and QoS parameters in the scheduling algorithm called coverage extension based on incentive scheduling to incite potential mobile relaying nodes to cooperate and, in turn, extend the wireless areas. We use the cross-layer approach to optimize the QoS parameters. The proposed solution not only incites the nodes to cooperate but enhances the QoS by increasing the average throughput and decreasing the delay as well. The simulation results show that the proposed solution not only gives better results than the well-known scheduling algorithms, such as maximum signal-to-noise ratio (MaxSNR) and weighted fair opportunistic (WFO), but allows the cooperative mobile nodes to increase their own throughput by around 114% as well. The total amount of data transmitted out of the cell to extend the coverage can be increased by around 59% compared with the scheduling algorithm MaxSNR.

Carrier aggregation for LTE-advanced: uplink multiple access and transmission enhancement features

Abstract: Multiple access and transmission enhancement in support of carrier aggregation techniques has been actively studied in the 3GPP LTEAdvanced standardization process of the nextgeneration mobile broadband communication systems. By means of carrier aggregation, users can access a total bandwidth of up to 100 MHz in order to meet the IMT-Advanced requirements. This article first introduces and compares several uplink multiple access schemes in LTE-Advanced standard. Technical challenges arising from the use of carrier aggregation is then addressed, with focus on reference signals design for uplink transmission. Meanwhile, various candidate options are summarized and compared in terms of their system performance, computational complexity, and design flexibility. The article further proceeds to investigate the link performance with carrier aggregation, taking into account the presence of frequency offset and fast fading in the uplink channel. Numerical results are also presented, which indicate that advanced signal processing algorithms should be further studied and optimized to ensure reliable operation of the 3GPP LTE-Advanced in high mobility.

Impact of Channel Estimation Error on Bidirectional MABC-AF Relaying With Asymmetric Traffic Requirements

Abstract: Channel estimation error results in severe performance deterioration in wireless networks. In this paper, we study the impact of imperfect channel estimation (ICE) on the outage performance of bidirectional relaying where the two sources have asymmetric traffic requirements (ATRs). In particular, we focus on the amplify-and-forward (AF) relay-assisted multiple-access broadcast (MABC) protocol, i.e., MABC-AF, which has received much attention due to its high spectrum efficiency and low complexity. In the single-relay scenario, we derive exact and generalized closed-form expressions for system outage probability, which indicate that the system outage is determined by the unidirectional outage in the case of highly asymmetric traffic patterns. For more insights into our approach, the closed-form asymptotic expressions are also evaluated, manifesting the interesting error floor (EF) phenomenon due to ICE. Using these analytical results, we further develop a robust and practical optimum power-allocation (OPA) algorithm that minimizes the system outage probability under aggregate and individual node power constraints. In the multirelay scenario, by taking into account the traffic knowledge, a novel relay selection criterion is proposed for asymmetric MABC-AF, followed by its impact on the system outage probability in the presence of ICE. Numerical results validate the accuracy of our analytical results and highlight the effect of the proposed OPA algorithm under various traffic requirements and channel estimation errors. Furthermore, the results also show that the proposed relay selection criterion is superior to the classical max–min criterion with ATRs, and the performance improvement becomes remarkable as channel estimation error increases.

A Two-Step Secure Localization for Wireless Sensor Networks

Abstract: Accuratelylocatingunknownnodesisacriticalissueinthestudyofwirelesssensornetworks(WSNs). Many localization approaches have been proposed based on anchor nodes, which are assumed to know their locations by manual placement or additional equipments such as global positioning system. However, none of these approaches can work properly under the adversarial scenario. In this paper, we propose a novel scheme called two-step secure localization (TSSL) stand against many typical malicious attacks, e.g. wormhole attack and location spoofing attack. TSSL detects malicious nodes step by step. First, anchor nodes collaborate with each other to identify suspicious nodes by checkingtheircoordinates,identitiesandtimeofsendinginformation.Then,byusingamodifiedmesh generationscheme,maliciousnodesareisolatedandtheWSNisdividedintoareaswithdifferenttrust grades. Finally, a novel localization algorithm based on the arrival time difference of localization information is adopted to calculate locations of unknown nodes. Simulation results show that the TSSL detects malicious nodes effectively and the localization algorithm accomplishes localization with high localization accuracy.

Social interaction increases capacity of wireless networks

Abstract: A network model with both social and communication characteristics is considered. Different capacity regions are computed as a function of the social network size for each node. It has been shown that as the social connectivity among nodes improves, the likelihood of finding shorter path between source-destination pairs in the network increases which results in increase in the capacity compared to the original results by Gupta and Kumar [3].

Exploiting 4G mobile user cooperation for energy conservation: challenges and opportunities

Abstract: Recent years have witnessed tremendous success and popularity of mobile applications and services, resulting in an explosive growth in the number of mobile devices, as well as in the range and types of things these devices can do. People nowadays become extremely dependent on their smartphones and handheld devices to access and receive online services. While computing and processing powers of these handheld devices are keeping up with this demand, battery lifetime remains the performance bottleneck, and researchers are now more challenged than ever before to come up with new techniques that can make efficient use of the devices? energy resources. In this article, we focus on exploiting user cooperation as a way of conserving energy in 4G mobile networks. We first begin by overviewing user cooperation and illustrating its potential for reducing energy consumption. Then, we describe the key challenges 4G mobile users face vis-a-vis of cooperation. Finally, we discuss some of the techniques proposed in literature to address these challenges by highlighting their methodologies, advantages, and disadvantages.

Protecting private cloud located within public cloud

Abstract: Many studies use cryptographic technologies to protect sensitive data in public cloud. However, these approaches may introduce large overheads. Recently, hybrid cloud started to gain a lot of attentions. A hybrid cloud consists of a private cloud and a public cloud. Hybrid cloud allows users to store sensitive data in their private cloud and hence enables efficient and secure data outsourcing. In this paper, we consider a new hybrid cloud model “Cloud-in-Cloud” (CIC). Our CIC model uses a new architecture to form a hybrid cloud: placing a small number of private computers (i.e., a small private cloud) within a public cloud. The private cloud can be used to store sensitive user data. Furthermore, it is within the public cloud, so the communications between private and public clouds have small overhead. And then we study how to protect a private cloud that locates within a semi-trusted environment. We present two methods that can detect attacks that try to obtain data and information in the private cloud. Our methods are able to efficiently detect physical attacks, such as the cold boot attack and the USB autorun attack. Experimental results show that our methods have small overhead.

Cloud-assisted mobile computing and pervasive services [Guest Editorial]

Abstract: In order to provide rich mobile pervasive services to end users, advancing mobile communication technologies and deployment of smart devices have become key issues in both industry and academia. However, the limited onboard computing, energy supply, and storage capabilities of mobile devices are hampering their ability to support the increasingly sophisticated applications demanded by users. Recently, mobile cloud computing (MCC) technologies for mobile devices have emerged to overcome these limitations. These technologies can minimize the requirements of computing power and storage to deploy pervasive applications in mobile devices. Developments of innovative and pervasive mobile services (mobile video streaming, rich media dissemination, surveillance, e-gaming, healthcare, etc.) can be greatly facilitated by cloud computing platforms employing advanced technologies.

A Measurement Study on the Topologies of BitTorrent Networks

Abstract: BitTorrent (BT) is a widely-used peer-to-peer (P2P) application. Most of BT's characteristics (except the topology) have been studied extensively by measurement approaches. In this paper, we deploy a measurement system to examine some performance-related topology properties of BT. Our goal is to provide a measurement view of the real-world BT topologies and to verify the previous estimations via simulations and real-world experiments. We observe that at the steady stage, a BT topology has short distances and low clustering coefficients, and its degree-frequency exhibits a Gaussian-like distribution. These indicate that a BT network is very close to a random network rather than a scale-free network or a small world. The proportion of peers with large download percentages is very high at the steady stage, showing that the swarm is robust from the resource perspective. We also find out that most high-degree peers have a very fast download speed. However, the low Spearman's rank correlation coefficient indicates that there is no strong correlation between the peer connection degree and the download speed. Different from previous results, we find that the diameter of a BT network at the initial stage is small even when 95% of peers use the peer exchange extension.

Copy limited flooding over opportunistic networks

Abstract: Mobile devices with local wireless interfaces can be organized into opportunistic networks which exploit communication opportunities arising from the movement of their users. With the proliferation and increasing capabilities of these devices, it is significant to investigate message dissemination over opportunistic networks to maximize the potential of those networks. In this paper, we analyze the performance of copy-limited flooding over opportunistic networks, where each node can only send no more than k copies of the same message. For this purpose, we propose a network model called Markov and Random graph Hierarchic Model (MRHM), where a node transfers among different Main-areas (places frequently visited by nodes) according to the Markov rule, and two different nodes in the same Main-area can establish a connection with a certain probability. We theoretically analyze the performance of k-copy limited flooding over MRHM in terms of delivery rate and delay. Our extensive experiments over MRHM and real traces reveal that when k equals 3, the performance of k-copy limited flooding is very close to that of Epidemic Routing.

On the statistical distribution of electric field inside jet engines

Abstract: Using full wave analysis in `Ansys® HFSS', we obtain the electric field distribution inside a jet engine containing one set of 24 blades due to the excitation provided by a simple Hertzian dipole. Hertzian dipole illuminates the structure by radiating continuous wave field. The real and imaginary components of the electric field along the engine axis for various excitation positions are extracted and analyzed statistically. Our results show that the real and imaginary field components along the engine's main axis are dependent Gaussian distributions with different means and variances. These results provide a novel general statistical modeling for the field distribution inside the engine. This statistical approach to electromagnetic analysis avoids all the sophisticated engine details.

Improving Macrocell Downlink Throughput in Rayleigh Fading Channel Environment Through Femtocell User Cooperation

Abstract: This paper studies cooperative techniques that rely on femtocell user diversity to improve the downlink communication quality of macrocell users. We analytically derive and evaluate the achievable performance of these techniques in the downlink of Rayleigh fading channels. We provide an approximation of both the bit-error rate (BER) and the data throughput that macrocell users receive with femtocell user cooperation. Using simulations, we show that under reasonable SNR values, cooperative schemes enhance the performances of macrocells by improving the BER, outage probability, and data throughput of macrocell users significantly when compared with the traditional, non-cooperative schemes.

Adaptive service function for system reward maximization under elastic traffic model.

Abstract: We propose an adaptive service model that maximizes the amount of service that spectrum users (SUs) achieve from accessing DSA systems. The proposed model allows SUs to utilize available spectrum efficiently by enabling them to locate spectrum opportunities in a distributed manner, thereby maximizing the long-term rewards that SUs receive. In this model, SUs adapt their required level of service with time depending on the amount of service they received so far. This proposed model is suitable for and can be used by existing objective functions. It leads to the maximization of the amount of service that SUs receive through DSA. Our simulation results show that the proposed adaptive model is very scalable by performing well regardless of the number of users in the system, and allows users to achieve high service rewards by quickly locating spectrum opportunities in the system.

Opportunistic access for cooperative cognitive radio networks with requirement constraint

Abstract: In cognitive radio network, cooperation between primary users and secondary users can improve their data rate and achieve dynamic spectrum sharing. This paper proposes a novel spectrum sharing model to solve the opportunistic access problem in cooperative cognitive radio network (CCRN). In this model, primary users select sets of secondary users as their relays and allocate channel resource to secondary users according to their cooperative transmitting power. Secondary users have their own data rate requirement, and they have to determine their optimal relay power to satisfy their requirement. Primary users have to select the best relay group and maximize their throughput. We model this problem as a Stackelberg game and prove the existence and uniqueness of Nash Equilibrium. A low-complexity algorithm is proposed to realize the cooperative transmission mechanism. Simulation results show significant throughput enhancement in the primary network and more opportunities for secondary users to get access into the spectrum.

Impact of location heterogeneity on random walk mobility models

Abstract: This paper investigates random walk mobility models with location heterogeneity, where different locations may have different neighboring regions.With the assumption of totally n locations, we consider two cases, i.e., full-range locations where nodes situated have the capability to shuffle throughout the network and long-range locations where nodes are allowed for moving to positions nearby within a certain range. In the former situation, with the exact expressions derived, we find location heterogeneity has a critical impact on the first hitting time of random walk, varying from Θ(n) to Θ(n3) according to different extent of heterogeneity. The result covers, as two special cases, both the classic independent and identically distributed (i.i.d) mobility and traditional random walk as we vary the number of full-range locations. In the latter one, our asymptotic results on both the first crossing time and cover time suggest that they are inversely proportional to the range of neighboring region r (∝ r−2 and ∝ r−1, respectively). Furthermore, extensive simulation is conducted to verify our observations and enhance the understanding on the effect of network parameters.

Taking advantage of multi-user diversity in OFDM systems

Abstract: A multi-user diversity approach, called Opportunistic Interference Management (OIM), is considered in connection with Orthogonal Frequency Division Multiplexing (OFDM) systems. The OIM is applied to each consecutive group of OFDM sub-channels that are highly correlated. We use the OIM to transmit information in Qg consecutive sub-channels to d users in parallel. The expected parallel transmissions per group of sub-channels is then computed. The results show that the maximum expected parallel transmissions is achieved almost surely when enough mobile users exist.