With the recent outbreak of the COVID-19 pandemic, major industries and academic institutions throughout the world have moved into a work-from-home situation, which resulted in a huge demand for networking resources. In particular, several home users are demanding simultaneously high data rates to support online video streaming applications, like Webex and Zoom. Therefore, it is expected that in these situations the quality of experience of online users may be severely affected or deteriorated, especially as the number of simultaneous active online users increases. In this paper, we use the Neyman-Scott Cluster Process from Stochastic Geometry to model the spatial patterns of online home users and analyze the throughput that could be achieved by a various numbers of online home users who are accessing the internet concurrently.

In the recent year, people had to work from home due to the outbreak of the COVID-19 pandemic. When the majority of the family members are working online, the bitrate experienced by the average user may drop, especially if some members have to work in rooms that suffer from weak coverage. Benefiting from the emerging concept of Reflective Intelligent Surfaces (RIS), the network coverage in our houses can be greatly improved. This paper presents a study of an RIS-assisted system for an indoor scenario operating at 2.4GHz. We propose an RIS placement approach that is based on minimizing the pathloss of the channel, to enhance the rate of bad coverage rooms, while taking into consideration their user occupancies. The proposed approach, which we refer to as the Weighted RIS Placement, is modeled and simulated for a single RIS. The problem is then extended to a two-RIS scenario. Our results show that the Weighted RIS placement provides significant rate gains. Also, this is the first work that models the communication channels for the individual rooms, using corresponding Rician K-factor values that reflect the indoor layout.

Vehicular networks are gaining a huge momentum as a mean for an intelligent transportation system that can address numerous problems related to traffic monitoring, accidents, autonomous driving, etc. However, the deployment of vehicular networks is a big challenge for vehicles manufacturers and governments in terms of responsibility and cost. Compared to related research efforts that assume a fixed medium access probability (MAP) of nodes, this paper presents an analytical model using the stochastic geometry tool where we derive the MAP of DSRC nodes in a network composed of vehicles (DSRC nodes) that are located on a system of roads. We then model the roads using a Poisson line process (PLP) and the locations of nodes on each road as a homogeneous 1D Poisson point process (PPP). Also, we model the MAP based on the IEEE 802. 11p standard, where we consider the effect of interference and the carrier sense multiple access with collision avoidance (CSMA/CA). We validated the analytical model against Monte Carlo simulations to prove its accuracy and reliability. The importance of our work stems from the fact that the developed MAP model contributes to the understanding of future DSRC network deployments.

This paper develops a framework to study multi-hop relaying in a vehicular network consisting of vehicles and Road Side Units (RSUs), and the effect of this relaying on the network coverage and the communication delay. We use a stochastic geometry model that consists of a combination of Poisson Line Process (PLP) and 1D Poisson Point Process (PPP) to reliably characterize the vehicular network layout and the locations of the vehicles and the RSUs. Using this model, we analyze the effect of the different network parameters on the coverage provided by the RSUs to the vehicles. Then, we investigate how the uncovered vehicles can receive their intended packets by relaying them through multiple hops that form connected paths to the RSUs. We also analyze the delay introduced to packet delivery due to multi-hop relaying. Namely, we present results that illustrate the coverage gains achieved through multi-hop relaying and the delays induced. Such results could be used by network planners and operators to decide on the different configurations and operational parameters of the vehicular network to suit particular scenarios and objectives.

Carrier Aggregation (CA) has been evolving with all releases of LTE due to its large benefits. However, LTE is based on OFDM which suffers from its high Peak-to-Average-Power-Ratio (PAPR), therefore inducing non-linearities and causing deterioration in the power efficiency of the High Power Amplifier (HPA). Although the PAPR problem has been extensively tackled, there remains a need for techniques that can cope with current system designs. We therefore propose in this paper a new distortion-less PAPR reduction method that is characterized by its high performance and significantly lower complexity when compared to existing methods. We refer to this technique as the Peak Valley Alignment (PVA) method. It is inspired from the sequence alignment techniques used in bioinformatics. We show that the performance attained by optimization-based methods can be approximately achieved through the use of heuristics at a much lower complexity.

Connection and Service Request (CSR) scheduling affects the performance of a Mobile Relay Node (MRN) in relay-assisted LTE network in terms of crucial Quality-of-Service (QoS) metrics such as the blocking probability and the system's response time. In this paper, a novel Deadline-constrained Connection and service Request Scheduling (DCRS) scheme is proposed with the objective of improving an MRN's performance in terms of the above-mentioned metrics. A stochastic queueing model is formulated for the purpose of capturing the MRN's behavioral dynamics and evaluating its performance as it operates under DCRS. Simulations are conducted in order to verify the model's results' validity and accuracy. Moreover, the MRN performance achieved under DCRS is compared to that achieved under the typically adopted First-Come-First-Servce (FCFS) scheme. Results indicate that DCRS remarkably outperforms FCFS.

The increasing demand on data and services is pushing LTE network operators toward extending their operations to the unlicensed spectrum. The licensed assisted access (LAA) technology is a promising technology to exploit the unlicensed bands and increase the overall LTE network capacity. However, there is a need for characterizing the network performance of LAA operators as their number scale in the unlicensed bands. Hence, in this paper, we develop a framework based on stochastic geometry to model the coexistence of LAA operators. The area system throughput is utilized to analyze the performance imbalance that results from the coexistence of a large number of operators. We validate the accuracy of the proposed model against Monte Carlo simulations and we shed the light on the severe impact of such co-existence on the performance of some operators where their area system throughput may get drastically reduced.

While the topological interference management (TIM) problem was originally studied in a partially connected network, the novelity of this paper appears in exploring its performance in practical scenarios, where path losses exist. In this work, we also define the conditions under which TIM should be applied in order to save processing time when mobility is taken into account. Numerical results show the implication of these scenarios in constraining the degrees-of-freedom (DoF) achieved.

Abnormal driving refers mostly to drunk driving, fatigue driving, and aggressive driving behaviors. This work addresses drunk driving detection, which actually can be extended to apply to detection of the other abnormal driving behaviors. The approach learns about the related on-board vehicle sensors for detecting drunk driving behaviors based on learning using certain drunk driving cues. In a previous work, we developed a Hidden Markov Model (HMM) method and applied it to each time series of the selected sensors measurements. The prediction accuracy was highest for the longitudinal acceleration, with a maximum of 79%. Here, we extend our early work that was based on HMMs and employ Recurrent Neural Networks that specialize in time series, where our testing results indicate accuracy percentages that go into the upper nineties.

While cloud computing has provided major benefits by maximizing the use of resources within a cloud, the current solutions still face many challenges. In this paper, we propose performance enhancements for cloud computations, provided by integrating hardware acceleration into the computation services. We extend the Hadoop framework by adding provisions for hardware acceleration using Field Programmable Gate Arrays (FPGAs). Hardware acceleration using energy efficient FPGAs is used as a service within the clouds or to offload computations when needed. It can provide additional sources of revenues, reduced operating costs, and increased resource utilization. We developed a custom Hadoop system and tested four applications commonly used for machine learning and deep learning. The results show the benefits of hardware acceleration and the high performance gains in smaller execution times and energy consumption.

The proliferation of high data-rate applications and services in next-generation WLANs, as well as the significant increase in the number of Wi-Fi devices, is triggering the search for more bandwidth. For this, the Federal Communications Commission (FCC) is considering a proposal to permit devices, such as those that use the IEEE 802.11 (Wi-Fi) protocol, to operate in the 5.9 GHz band allocated to the intelligent transportation system (ITS). However, the nature of these bands poses a challenge since ITS dedicated short range communications (DSRC) networks use them to share safety-critical messages and may be subject to severe interference from other coexisting transmissions. We discuss the impact of coexistence of Wi-Fi networks on the performance of DSRC through an analytical framework based on stochastic geometry. We consider the recent IEEE 802.11ax Wi-Fi standard, and analyze uplink and downlink transmissions, with voice and background traffic being the highest and lowest priority traffic, respectively. We also validate the fixed contention window size of the derived stochastic geometry model using NS-3 simulations. The proposed framework can serve to increase awareness among regulatory bodies of the extent to which coexistence will adversely affect the performance of DSRC.

In this paper, we develop a joint clustering and topological interference management (TIM) framework for a device-to-device (D2D) network. This scheme divides the whole network into multiple groups, each served on a different frequency, and the interference within each group is managed by TIM, based only on the connectivity pattern and not on the instantaneous channel state information (CSI). To this end, we model TIM as a low-rank-matrix-completion problem (LRMC) problem and solve it using a novel and low-complex scheme based on semidefinite programming (SDP). As for the clustering part, we develop a clustering algorithm that is suited for the LRMC approach to solve TIM while building on the SDP relaxation of the maximum-$k$-cut algorithm, and extending it to account for each cluster’s capacity. This clustering problem turns out to be a capacitated maximum-$k$-cut problem, for which we derive a relatively tight upper bound, that helps in determining the performance guarantee of many clustering algorithms. Simulation results show that the joint clustering-TIM can help, in some cases, improve the system degrees-of-freedom (DoF), especially in large D2D networks. Our proposed scheme also reduces the computation time of the LRMC-based TIM approach.

Convolutional Neural Network (ConvNet or CNN) algorithms are characterized by a large number of model parameters and high computational complexity. These two requirements have made it challenging for implementations on resource-limited FPGAs. The challenges are magnified when considering designs for low-end FPGAs. While previous work has demonstrated successful ConvNet implementations with high-end FPGAs, this article presents a ConvNet accelerator design that enables the implementation of complex deep ConvNet architectures on resource-constrained FPGA platforms aimed at the IoT market. We call the design “FeatherNet” for its light resource utilization. The implementations are VHDL-based providing flexibility in design optimizations. As part of the design process, new methods are introduced to address several design challenges. The first method is a novel stride-aware graph-based method targeted at ConvNets that aims at achieving efficient signal processing with reduced resource utilization. The second method addresses the challenge of determining the minimal precision arithmetic needed while preserving high accuracy. For this challenge, we propose variable-width dynamic fixed-point representations combined with a layer-by-layer design-space pruning heuristic across the different layers of the deep ConvNet model. The third method aims at achieving a modular design that can support different types of ConvNet layers while ensuring low resource utilization. For this challenge, we propose the modules to be relatively small and composed of computational filters that can be interconnected to build an entire accelerator design. These model elements can be easily configured through HDL parameters (e.g., layer type, mask size, stride, etc.) to meet the needs of specific ConvNet implementations and thus they can be reused to implement a wide variety of ConvNet architectures. The fourth method addresses the challenge of design portability between two different FPGA vendor platforms, namely, Intel/Altera and Xilinx. For this challenge, we propose to instantiate the device-specific hardware blocks needed in each computational filter, rather than relying on the synthesis tools to infer these blocks, while keeping track of the similarities and differences between the two platforms. We believe that the solutions to these design challenges further advance knowledge as they can benefit designers and other researchers using similar devices or facing similar challenges. Our results demonstrated the success of addressing the design challenges and achieving low (30%) resource utilization for the low-end FPGA platforms: Zedboard and Cyclone V. The design overcame the limitation of designs targeted for high-end platforms and that cannot fit on low-end IoT platforms. Furthermore, our design showed superior performance results (measured in terms of [Frame/s/W] per Dollar) compared to high-end optimized designs.

The proliferation of multimedia applications and services increased the demand on data and the requirement by operators to improve the experience of their users. This has motivated the extension of cellular technologies, such as Long Term Evolution (LTE) toward using the unlicensed bands. However, the nature of these bands poses a challenge since there is uncontrolled interference from other coexisting transmissions. We discuss in this paper the issue of efficient coexistence of LTE operators in the unlicensed bands through an optimization framework that is based on performance metrics obtained using stochastic geometry. The proposed optimization framework allows for obtaining optimized network topologies that maximize the benefit of LTE operators looking to deploy their networks in the unlicensed bands.

In this paper, we provide closed form expressions for the probability density functions (PDF) of the interference power in a network whose transmitters are arranged according to the Poisson Point Process (PPP). These expressions apply for any integer path loss exponent η greater than 2. Using the stretched exponential or Kohlrausch function, we show that the PDF formulas can be obtained as long as the Laplace transform (LT) for the PDF follows a specific common (exponential) formulation. Moreover, we show that such closed form expressions can be useful in deriving performance metrics for the network for any fading type experienced by the signals. Finally, using Monte-Carlo simulations and numerical analysis, we validate the accuracy of the proposed analytical derivations.

Deep neural networks have gained tremendous attention in both the academic and industrial communities due to their performance in many artificial intelligence applications, particularly in computer vision. However, these algorithms are known to be computationally very demanding for both scoring and model learning applications. State-of-the-art recognition models use tens of millions of parameters and have significant memory and computational requirements. These requirements have restricted the users of deep neural network applications to high-end, expensive, and power hungry IoT platforms to penetrate the deep learning markets. This paper presents work at the leading edge intersection of several evolving technologies, including emerging IoT platforms, Deep Learning, and Field-programmable Gate Array (FPGA) computing. We demonstrate a new minimalist design methodology that minimizes the utilization of FPGA resources and can run deep learning algorithms with over 60 million parameters. This makes particularly suitable for resource-constrained, low-end FPGA platforms.

With the increasing demand on higher data rates to enhance the user experience, one possible solution would be to extend the cellular technology such as LTE toward the unlicensed bands. Initially, LTE was designed based on the frequency re-use factor of one and which has lead to higher capacity in several deployment scenarios. This happens when LTE exclusively uses the licensed spectrum where interference can be controlled. On the other hand, when LTE uses the unlicensed spectrum, other technologies such as WiFi will coexist and hence LTE will be subject to uncontrolled interference while it is expected to achieve a fair coexistence with such technologies. Given these constraints, we discuss in this paper the utilization of frequency re-use factor of one for LTE in the unlicensed band. In this case and subject to regulations of utilizing unlicensed bands, LTE will use the Listen before talk (LBT) mechanism with other radio access technologies. Thus, using tools from stochastic geometry, we model and analyze the effect of such scenario while comparing it to the case where LTE considers LBT mechanism with other LTE transmissions. Our analysis shows interesting performance gains that can be achieved by LTE in terms of rate coverage probability.

Global statistics show that about third of fatalities on the road involve pedestrians and cyclists, but surprisingly, this area is not receiving the attention it deserves from the research community. Communications between vehicles and smartphones held by pedestrians can greatly help in road accident prevention, and hence, introducing a system that exploits the advancements in wireless communication could certainly mitigate a significant part of the problem. Motivated by this, a system is proposed that relies on cellular communication and vehicle communication to detect probable vehicle to pedestrian crashes. Our simulations produced promising experimental results that illustrate the potentials of such a system in saving lives on the roads.

Machine Type Communication (MTC) is a key component of future 5G networks, and its realization is now possible due to the advances in technology and the market drivers. Several challenges however exist which hinder the realization of MTC, among which signaling overhead is considered the prominent challenge, particularly due to the massive number of devices in MTC networks. In this work, we consider an MTC system which utilizes massive MIMO and cell densification to support massive number of devices. In our scheme, devices within small cells can transmit their uplink data simultaneously on the same time-frequency resource with minimal interference due to the massive MIMO implementation, and random access is applied on a per-cell basis to limit the inter-cell interference. We derive a stochastic geometry model for our system and we use it in an optimization study. Our results can be used for optimal network planning and optimal resource allocation.

Carrier Aggregation started to appear since release 10 of LTE, and offers higher data rates, but at the cost of increased Peak-to-Average-Power-Ratio (PAPR). This paper studies the distribution of PAPR through analyzing the Crest Factor (CF) which is the square root of the PAPR of the Carrier Aggregated OFDM (CA-OFDM) signals used in the downlink of LTE-A. Although the base station is not power constrained, the increased PAPR can adversely affect performance in terms of energy efficiency and coverage. We model the distribution of the CF by adopting the Level Crossing Rate analysis to approximate the peak distribution of the CA-OFDM signal which can be characterized as a bandlimited complex Gaussian process. The expression of the distribution is derived for an arbitrary number of component carriers for both contiguous and non-contiguous aggregation, where simulations show good agreement with the derived analytical expressions. The derived expression is applied to model the Selective Mapping technique used for PAPR reduction.

In a previous work, we presented a system which combines active solid state drives and reconfigurable FPGAs (which we called reconfigurable active SSD nodes, or simply RASSD nodes) into a storage-compute node that can be used by a cloud data-center to achieve accelerated computations while running data intensive applications. To hide the complexity of accessing RASSD nodes from applications, we proposed in another work a middleware framework which handles all low-level interactions with the hardware. The Middleware Server (MWS), which manages a group of RASSD nodes, has the role of bridging the connection between a client and the nodes. In this paper, we present extensions to the MWS to enable it to operate within a collaborative cloud environment, and we develop a model to evaluate the performance of the collaborative MWS. This model represents a study of the utilization of three hardware resources of the MWS: CPU, memory, and network interface. For each, we derive the parameters that affect its operations, and propose formulas for its utilization. The results describe the capacity of a MWS, and hence can be used to decide on the number of MWSs in a collaborative cloud datacenter.

The growing demand on data to enhance the user experience has motivated research toward increasing the efficiency of spectrum utilization by extending cellular technology, such as LTE, toward unlicensed bands. In order to study the fair coexistence of LTE and Wi-Fi, we consider the IEEE 802.11ax Wi-Fi standard, where we use stochastic geometry to model and analyze the coexistence of LTE with simultaneous uplink and downlink IEEE 802.11ax transmissions. Mainly, we consider LTE with continuous transmissions (no protocol change), LTE with discontinuous transmissions (LTE-U), and licensed-assisted access (LAA) coexistence mechanisms. In addition, we focus on single unlicensed frequency band transmissions, where the locations of Wi-Fi access points, Wi-Fi stations (users), and LTE eNodeBs (eNBs) are modeled as three independent homogeneous Poisson point processes. Then, we derive analytical expressions for a set of performance metrics, which are the medium access probability, signal-to-interference-plus-noise ratio coverage probability, density of successful transmissions, and Shannon throughput probability for both uplink and downlink of IEEE 802.11ax in addition to LTE. Our analysis quantifies both single-user and multi-user operation modes of the IEEE802.11ax and show that LTE-U or LAA can be a good neighbor for IEEE 802.11ax for different traffic types.

This work adopts the paradigm of cloud computing over the framework of Device-to-Device (D2D) communications in LTE-Advanced to enable mobile devices to offer network services to nearby devices, thus acting as mobile cloudlets, and to offload cellular traffic from the core network. Hence, any mobile device seeking a new service can search and discover for nearby services with the help of the LTE-A network. From an implementation point of view, our solution fits very well within the 3GPP standards as it utilizes its network elements designated for offering proximity based services. Our experimental results proved the efficiency of our system in helping mobile users discover needed services offered by nearby providers.

Carrier aggregation (CA) is a key enabling technique to increase the bandwidth of users in order to meet the increasing demand on peak data rates for emerging services and applications. However one of the main practical challenges that comes with CA is the severe increase in the peak-to-average-power ratio (PAPR) of the aggregated time domain NxSC-FDMA signal. This issue is critical for the user equipment (UE) in the uplink as it affects the efficiency of the power amplifier (PA) and hence the transmission coverage. In this paper, a novel two stage PAPR reduction scheme based on frequency spacing aware Discrete Fourier Transform (FSA-DFT) is proposed. Several CA scenarios were analyzed using the proposed technique. Experimental results show that the proposed technique provides a significant reduction in the PAPR of aggregated NxSC-FDMA signal.

Device-to-Device (D2D) communication has gained a lot of interest in the last years. Recently, it has been accepted as a promising concept as part of the third generation partnership project (3GPP) standard in the LTE-A release 12 and release 13 under the name of Proximity-Based Services (ProSe). However, the proposed solutions to integrate the D2D in the cellular network require added functionalities on the network resources, mainly in the discovery process. In this paper, we mitigate the requirement of additional resources in the LTE-A network by proposing a novel D2D discovery protocol. Specifically, we propose to offload the D2D discovery onto the Vehicular Ad-hoc Networks (VANETs) by using the inherent knowledge of the Road Side Unit (RSU) about the users in its coverage area. In addition, we propose a framework to model and analyze the duration of our discovery through mathematical derivations. Then, all the results are validated through extensive simulations on both Network Simulator 3 (NS3) and Matlab.

In this paper we propose a framework for providing anonymity to communicating cars in VANETs. The anonymity is accomplished based on a system of pseudonym generation, distribution, and replenishing. The road side units (RSUs) play a key role in the framework by receiving the originally generated pseudonyms from the trusted authority, and then distributing pseudonym sets to cars while shuffling the sets amongst themselves to maximize anonymity. The pseudonym distribution process among the RSUs and to the vehicles is highly adaptive to accommodate the needs of the vehicles. We develop a distributed optimization algorithm for the shuffling process and a novel mechanism for cars to change their pseudonyms. Experimental evaluations based on ns3 simulations demonstrate the effectiveness of the framework through showing relatively high values of the used metric, namely the anonymity set.

Abstract This paper presents a faulty node detection approach for wireless sensor networks that aggregate measurement data on their way toward the sink (base station). The approach is based on the idea of commanding sensor nodes on the aggregation paths to temporarily stop including their readings in the received aggregated readings from their upstream neighbors. The scheme is dependent on the ability of the sink to detect faulty nodes through changes in the received aggregated readings at the sink using a Markov Chain Controller (MCC). The algorithm that is run in the sink uses the MCC to assign a state to each sensor node based on transitions that are triggered by receiving aggregated path readings, and accordingly deduces the nodes that may be faulty. The experimental results show at least 98% detection rate at the cost of reasonable detection delays and generated wireless network traffic. Copyright © 2016 John Wiley & Sons, Ltd.

Security and privacy have become critical in computer networks, especially with the emergence of E-commerce. Other than securing the transfer of data, users are interested in protecting their profile privacy against exposure attacks. Multimedia communications are at the core of new information and communication technologies. We seek to achieve end users' profile privacy without violating the Quality of Service constraints on the throughput, end-to-end delay, and jitter, as these parameters represent the critical factors in multimedia applications. We propose an end-to-end anonymity design that takes into consideration the constraints of Voice-over-IP applications in a hybrid network environment, which involves ad hoc and infrastructure networks. Using clusterheads for communication anonymity to preserve user profile privacy, as well as encryption of the real-time protocol payload, we prove using analysis and simulations that our model can be easily integrated into currently deployed network infrastructures. Copyright © 2016 John Wiley & Sons, Ltd.

Accessing remote cloud services usually involves high network latencies. To deal with this issue, several models of local cloudlets have been proposed, but most of which are based on powerful desktop machines running continuously and constantly to provide services to nearby users. In this paper, we propose a more ubiquitous solution based on less powerful but considerably more accessible machines, namely mobile smartphones. We envision a network of cloudlets distributed within a geographic area, connected to a root server that keeps track of their online presence and resource availability. Our framework is especially suitable for environments where cloud clients are interested in network and software services, in information and data generated and updated by applications or cached from accesses to remote cloud centers. We use the CloudSim simulator to evaluate the performance of the proposed solution and compare it with a peer solutions found in the literature.

In LTE-Advanced, carrier aggregation (CA) is a key enabling technique to increase the peak data rates of users and enhance the mobility management in heterogeneous networks (HetNets) using dual connectivity solutions. Several CA schemes have been proposed with a maximum of five LTE Release 8 component carriers (CCs) where the NxSC-FDMA has been chosen as the bandwidth extension scheme for the uplink. This enables the extension of the bandwidth allocated to a user up to 100 MHz while maintaining backward compatibility with LTE release 8 legacy users. However, CA leads to a severe increase in the peak-to-average-power ratio (PAPR) of the aggregated time domain NxSC-FDMA signal at the user equipment (UE). This is an important issue as it affects the power amplifier (PA) efficiency and hence the coverage of transmissions. In this paper, we propose a low- complexity post-IFFT technique to reduce the PAPR of carrier aggregated NxSC-FDMA signals in the uplink of LTE-Advanced. Several case studies of CA were analyzed by using the proposed technique. Simulation results show that the PAPR improvement is 2.5 dB for the case of 2 CCs at only about 4% of the complexity required by the partial selective mapping (PSLM) technique to achieve the same PAPR reduction.

The demand for high data rates in both the uplink and the downlink has motivated the use of carrier aggregation (CA) of several portions of the spectrum up to 100 MHz in LTE-Advanced, while maintaining backward compatibility with LTE release 8. One of the main practical challenges that comes with CA is the severe increase of peak-to-average-power-ratio (PAPR) of the corresponding generated time-domain OFDM signal, thus affecting the power amplifier (PA) efficiency, and hence the transmission coverage. This paper proposes a low-complexity joint interleaving technique to reduce the PAPR of carrier aggregated signals. Several CA scenarios were analyzed using our proposed technique. Simulation results demonstrate that our proposed technique can achieve the same PAPR reduction performance as that of the partial selective mapping (PSLM) technique with 66% reduction in terms of real multiplication and addition operations for the case of three aggregated component carriers (CCs).

In LTE-Advanced, carrier aggregation (CA) allows the extension of the bandwidth allocated to a certain user up to 100 MHz. In particular, the NxSC-FDMA has been selected as the uplink extension scheme. However, one of the main practical challenges that comes with CA is the severe increase in the peak-to-average-power ratio (PAPR) of the aggregated time domain NxSC-FDMA signal. The PAPR increase is an important issue as it affects the efficiency of the power amplifier (PA) at the user equipment (UE) and equivalently the transmission coverage of the LTE-Advanced system. In this paper we propose a PAPR reduction technique based on the well-known Karhunen-Loeve Transform (KLT) to reduce the PAPR of the NxSC-FDMA signals. Several CA scenarios were analyzed using the proposed technique and simulation results show that the performance of the PAPR has improved by 1.5 dB in case of carrier aggregation of two CCs.

In order to accommodate the exponentially-growing data traffic, LTE operators are considering the extension of the LTE operation into the unlicensed bands. In a recent technical report for the third Generation Partnership Project, Licensed-Assisted Access (LAA) to the unlicensed spectrum has been introduced. The report and other works in the literature reveal coexistence challenges that are raised when the LTE system coexists with other technologies such as WiFi, with fairness being the primary challenge. In this work, we propose a preliminary design for a semi-distributed LTE-Unlicensed scheme where the LTE Base Station uses WiFi-like carrier sense, back-off, and Quality of Service facility techniques. We also present a study on LAA-WiFi-coexistence through ns3 simulations. We conclude from our simulations that our preliminary design can achieve fairness in a limited set of scenarios, and we highlight the requirements and challenges that need to be considered in future work for designing a fair scheme for a wider set of scenarios.

In this paper, we introduce a scheme of caching requested data in LTE networks. After data (eg., web pages) is cached after its first request, the subsequent requests of the same data are served from the network's caching memory directly. The idea in this scheme is new in that the caching memory is at the level of the mobile devices themselves and not in the LTE core network, as in other proposed schemes. Our approach aims to minimize the required changes in the functions of the various elements of the LTE network core for supporting the caching operations. As we illustrate in the results section, the proposed system results in lower overall data access delays, which are attributed to retrieving some of the requested data from Internet servers when such data are not found in the network.

In 3GPP LTE-Advanced standard forum, Mobile Relay Node (MRN) occupies an important place. It is well known that cell-edge users suffer from bad Signal Level strength. To improve the signal quality and network coverage at the cell-edge it is proposed to use Mobile Relay Node. For the moment, MRN communicates to the UE devices in the vehicle. In this paper, we propose to implement MRN on the top of public transportation having known path and low speed to serve data hungry users outside the vehicles.

As a way of meeting a substantial increase in traffic demands, the concept of Heterogeneous Networks or HetNets was introduced. A HetNet is a multi-tier cellular network consisting of a macrocell tier overlaid with a microcell tier. Typically, the transmission power a Macrocell base station (BS) is higher than the transmission power of a Microcell BS. One of the goals of a HetNet is to offload traffic from the macrocell BS to the microcell BS. This purpose can be achieved by expanding the microcell region so that more users will associate with it. This causes significant cross-tier interference which can be remedied by utilizing coordinated multipoint (CoMP) within the microcell expanded region (ER). Our proposed methodology considers the effect of overlapping ERs and uses tools from stochastic geometry to analyze performance metrics in terms of outage probability.

Organizations are starting to realize the significant value of advertising on mobile devices, and a number of systems have been developed to exploit this opportunity. From a privacy perspective, practically all systems developed so far are based either on a trusted third-party model or on a generalized architecture. We propose a system for delivering context, location, time, and preference-aware advertisements to mobiles with a novel architecture to preserve privacy. The main adversary in our model is the server distributing the ads, which is trying to identify users and track them, and to a lesser extent, other peers in the wireless network. When a node is interested in an ad, it forms a group of nearby nodes seeking ads and willing to cooperate to achieve privacy. Peers combine their interests using a shuffling mechanism in an ad-hoc network and send them through a primary peer to the ad-server. In this way, preferences are masqueraded to request custom ads, which are then distributed by the primary peer. Another mechanism is proposed to implement the billing process without disclosing user identities.

Abstract This work proposes a replication scheme that is implemented on top of a previously proposed system for MANETs that cache submitted queries in special nodes, called query directories, and uses them to locate the data (responses) that are stored in the nodes that first request them, called caching nodes. The system, which was named distributed cache invalidation method (DCIM), includes client‐based mechanisms for keeping the cached data consistent with the data source. In this work, we extend DCIM to handle cache replicas inside the MANET. For this purpose, we utilize a push‐based approach within the MANET to propagate the server updates to replicas inside the network. The result is a hybrid approach that utilizes the benefits of pull approaches for client server communication and those of push approaches inside the network between the replicas. The approach is analyzed analytically, and the appropriate number of replicas is obtained, where it was concluded that full replication of the indices of data items at the query directory and two‐partial replication of the data items themselves makes most sense. Simulation results based on ns2 demonstrate the ability of the added replication scheme to lower delays and improve hit ration at the cost of mild increases in overhead traffic. Copyright © 2013 John Wiley & Sons, Ltd.

The spectrum database provided by FCC and Ofcom stores information about the availability of channels that can be used by vehicles to reliably transfer safety traffic information. However, due to the large number of queries to the database, the query delay could increase. In previous models, numerous modes of operation have been designed, but the communication between vehicles of different modes (particularly, Mode I and Mode II according to FCC terminology) is not discussed. Developed models for estimating the load on the database were based on the assumption that all vehicles travel at the same velocity, which is not a realistic condition for proper database load analysis. In this paper we address this issue by proposing an approach that divides the roads into segments and assigns a car or two to play the role of a Mode II covering the whole segment. The assigned vehicle(s) are responsible for providing the cars in their segments with the queried spectrum information. To test the validity of our design, we evaluate its performance using Matlab simulations based on the mathematical model we developed for estimating the number of Mode II cars. We illustrate how the database load varies in response to changes in various system parameters, such as number of segments, number of cars, and speed of vehicles.

A Vehicular Ad-hoc Network (VANET) is a type of Mobile Ad-hoc Network (MANET) that is used to provide communications between nearby vehicles on a hand, and between vehicles and fixed infrastructure on the roadside on the other hand. VANET is not only used for road safety and driving comfort but also for infotainment. An application area which is expected to greatly benefit from this advanced technology is Location Based Service (LBS): a service which helps users in finding nearby places. However, this application raises a privacy issue for these users since it can profile them and track their physical location. Therefore, to successfully deploy LBS, user's privacy is one of major challenges that must be addressed. In this paper, we propose a location privacy protection scheme to encourage drivers to use this service without any risk of being pursued. Our system was implemented using NS2 network simulator and found to achieve high values of anonymity.

In this article, we propose new extensions to Hadoop to enable clusters of reconfigurable active solid-state drives (RASSDs) to process streaming data from SSDs using FPGAs. We also develop an analytical model to estimate the performance of RASSD clusters running under Hadoop. Using the Hadoop RASSD platform and network simulators, we validate our design and demonstrate its impact on performance for different workloads taken from Stanford's Phoenix MapReduce project. Our results show that for a hardware acceleration factor of 20×, compute-intensive workloads processing 153MB of data can run up to 11× faster than a standard Hadoop cluster.

The strong potentials that exist in Vehicular Ad hoc Networks (VANETs) has given birth to the concept of Vehicular Clouds, in which cloud computing services are hosted by vehicles that have sufficient resources to act as mobile cloud servers. In this paper, we propose a protocol that enables vehicles to search for mobile cloud servers that are moving nearby and discover their services and resources. The design depends on roadside units (RSUs) that act as cloud directories with which mobile cloud servers register. We evaluate the performance of our protocol using ns2 and explain through comparing the results to another scheme the feasibility and efficiency of our protocol in terms of service discovery and service consuming delays and packet success ratio.

Caching systems have been proposed for MANETs to increase data availability and reduce data access delays. Every caching system is composed of three main components. The first component is requesting the data items from the server into the caching system. The second component is publishing the cached items in the network (or advertising them). While, the third component relates to nodes requesting cached items, or in other words pulling the items. These three aspects have inherent privacy problems that result in exposing the identities of the participants and in profiling their interests. In this work, we survey existing caching architectures for privacy vulnerabilities and propose a privacy preserving system that can operate on top of any existing caching system that provides anonymity and untraceability objectives. The system was implemented using ns-2 and proved to achieve high levels of anonymity with mitigated delays and overhead traffic.

A novel and rapidly growing area of research concerns data-intensive applications and the technical challenges that accompany it. One of those challenges is developing approaches and mechanisms that render high performance in processing and storing data. We joined this research effort by proposing a reconfigurable active solid state drives (RASSD) system that deals with such applications, through employing basic hardware, namely FPGA's connected to SSD's, to service the above applications as processing nodes, and take advantage of the close proximity between storage and processing. In this paper, we propose an intelligent middleware system for interfacing workstation-based and mobile applications to the distributed RASSD system. In order to provide high performance in terms of time and functionality, the middleware manages the data processing on the RASSD nodes through special pieces of code that we call drivelets, along with FPGA configuration files (bitstreams). Another important responsibility of the proposed middleware architecture lies in the unguided management of applications' flows, where it uses an intelligent script-parsing mechanism to turn one general request from the client into a sequence of operations needed to generate the required results. The middleware design allows for the integration of mobile applications into the overall architecture of the RASSD system, and allowing them to run data intensive applications that otherwise it is unfeasible for them to execute. We validate our design by comparing it to an existing middleware architecture, and present two use-cases with their results and discussion.

Cloud computing is increasingly becoming a desirable and foundational element in international enterprise computing. There are many companies which design, develop, and offer cloud technologies. However, cloud providers are still like lone islands. While current cloud computing models have provided significant benefits of maximizing the use of resources within a cloud, the current solutions still face many challenges including the lack of cross-leverage of available resources across clouds, the need to move data between clouds in some cases, and the lack of a global efficient cooperation between clouds. In [1], we addressed some of these challenges by providing an approach that enables various cloud providers to cooperate in order to execute, together, common requests. In this paper, we illustrate several enhancements to our work in [1] which focus on integrating hardware acceleration with the cloud services. We extend the Hadoop framework by adding provisions for hardware acceleration with Field Programmable Gate Arrays (FPGAs) within the cloud, for multi-cloud interaction, and for global cloud management. Hardware acceleration is used to offload computations when needed or as a service within the clouds. It can provide additional sources of revenues, reduced operating costs, and increased resource utilization. We derive a mathematical model for evaluating the performance of the most important entity in our system under various conditions.

Recent rules from FCC and OFCOM foresee the utilization of spectrum database as the main solution to provide accurate spectrum information about TV white spaces for secondary users in cognitive vehicular networks. Spectrum database provides maximum protection to licensed users, however, its implementation is not straight-forward in vehicular environments, due to the significant query overhead generated by mobile vehicles in congested urban scenarios. For this reason, in this paper we investigate possible solutions to integrate cooperative sensing and spectrum database querying, with the goal to minimize the primary users detection overhead while guaranteeing maximum protection for these primary users. We propose both theoretical and practical contributions in this field. First, we introduce a topological study to determine the optimal ratio between cooperation and spectrum database querying (referred to as ModeI, ModeII, cooperative Sensing-only devices according to FCC terminology) in order to minimize the network utilization for white space detection. We investigate various system parameters such as spectrum database query frequency, broadcast frequency (for cooperative sensing) and vehicles' velocity, and study their impact on system performance. Then, we propose a distributed (bio-inspired) protocol for network deployment that enables multi-interfaces vehicles to dynamically decide the detection mode to use, in order to minimize the database load, while providing high enough protection for licensed users.

This paper proposes distributed cache invalidation mechanism (DCIM), a client-based cache consistency scheme that is implemented on top of a previously proposed architecture for caching data items in mobile ad hoc networks (MANETs), namely COACS, where special nodes cache the queries and the addresses of the nodes that store the responses to these queries. We have also previously proposed a server-based consistency scheme, named SSUM, whereas in this paper, we introduce DCIM that is totally client-based. DCIM is a pull-based algorithm that implements adaptive time to live (TTL), piggybacking, and prefetching, and provides near strong consistency capabilities. Cached data items are assigned adaptive TTL values that correspond to their update rates at the data source, where items with expired TTL values are grouped in validation requests to the data source to refresh them, whereas unexpired ones but with high request rates are prefetched from the server. In this paper, DCIM is analyzed to assess the delay and bandwidth gains (or costs) when compared to polling every time and push-based schemes. DCIM was also implemented using ns2, and compared against client-based and server-based schemes to assess its performance experimentally. The consistency ratio, delay, and overhead traffic are reported versus several variables, where DCIM showed to be superior when compared to the other systems.

This paper proposes a data replication scheme implemented on top of a cooperative data caching architecture in MANETs that caches submitted queries in special nodes, called query directories (QDs), and uses them to locate data (responses) stored in the nodes that requested them, and called caching nodes (CNs). The QD entries are replicated according to a cost minimization model, and the actual data items are placed in nearby CNs. The proposed system is dynamic, as it adapts to topology changes and relocates replicas as necessary. The preliminary prototype of the proposed method is simulated using ns2 to assess its performance experimentally. Enhancements in performance in terms of lowered access delay and improved hit rates are reported, while maintaining a cap on overhead traffic.

The IEEE 1609.4-Multi-Channel Operation protocol has been proposed to support the co-existence of safety and non-safety (infotainments) applications over the Dedicated Short Range Communication (DSRC) channels at the 5.9 GHz band. However, the multi- channel approach over a single-radio transceiver might result in several performance degradations that have not been thoroughly investigated yet. In this paper, we analyze the performance of safety- related applications over multi-channel vehicular networks. We demonstrate through a simulation study that the synchronous channel switching enforced by the IEEE 1609.4 protocol might easily compromise the performance of safety applications that rely on the periodic exchange of short lived broadcasts. Thus, we propose in this work the WAVE-enhanced Adaptive Broadcast (WAB) scheme. WAB provides a novel MAC contention control mechanism intended to reduce the impact of packet collisions caused by the synchronous channel switching, and to increase the packet delivery rate of broadcast messages in congested vehicular scenarios. The WAB scheme dynamically adapts to the channel conditions through a distributed load estimator metric, and implements priority mechanisms to ensure fairness among vehicles. Simulation results reveal that the proposed WAB scheme can significantly increase the packet delivery rate of broadcast messages when compared to the existing IEEE 802.11p/1609.4 scheme.

Recently, the IEEE 1609.4 WAVE protocol has been proposed to enable multi-channel communication in Vehicular Ad Hoc Networks (VANETs). While the usage of multi-channel technology can favor the co-existence of safety and non-safety vehicular applications, its implementation on single-radio transceivers poses some major concerns about the effective utilization of the channel resources. In this paper, we investigate the performance of safety-related applications on multi-channel VANETs. We demonstrate that the synchronous channel switching operations enforced by the IEEE 1609.4 protocol introduce additional delays to the delivery of safety messages, that might compromise the viability of such applications. To cope with this problem, we propose a WAVE-enhanced Safety message Delivery scheme (WSD) that minimizes the delivery delay of safety messages in multi-channel VANETs, while preserving compatibility with the IEEE 1609.4/802.11p standards. WSD attempts to transmit high priority safety message during SCH intervals while guaranteeing reception by all neighbors. We formulate the broadcast problem in multi-channel VANETs as a scheduling problem over the different DSRC channels. We extend the problem formulation to cooperative scenarios, in which multiple vehicles contribute to disseminate the safety message over the different channels. We evaluate our proposed WSD scheme through a simulation study. We show that our proposed solution can provide effective reduction of the delivery delay in multi-channel VANETs, when compared to the legacy IEEE 1609.4/802.11p protocols.

Vehicular ad hoc networks (VANETs) enable vehicles to communicate with each other but require efficient and robust routing protocols for their success. In this paper, we exploit the infrastructure of roadside units (RSUs) to efficiently and reliably route packets in VANETs. Our system operates by using vehicles to carry and forward messages from a source vehicle to a nearby RSU and, if needed, route these messages through the RSU network and, finally send them from an RSU to the destination vehicle. Our system is mostly critical for users who are far apart and want to communicate using their vehicles' onboard units. Many recent paradigms, like social networks, will greatly benefit from a system like ours to enable users on the road to exchange different types of data. We evaluate the performance of our system using the ns2 simulation platform and compare our scheme to existing solutions. The results prove the feasibility and efficiency of our scheme.

Mobile devices are getting more pervasive, and it is becoming increasingly necessary to integrate web services into applications that run on these devices. We introduce a novel approach for dynamically invoking web service methods from mobile devices with minimal user intervention that only involves entering a search phrase and values for the method parameters. The architecture overcomes technical challenges that involve consuming discovered services dynamically by introducing a man-in-the-middle (MIM) server that provides a web service whose responsibility is to discover needed services and build the client-side proxies at runtime. The architecture moves to the MIM server energy-consuming tasks that would otherwise run on the mobile device. Such tasks involve communication with servers over the Internet, XML-parsing of files, and on-the-fly compilation of source code. We perform extensive evaluations of the system performance to measure scalability as it relates to the capacity of the MIM server in handling mobile client requests, and device battery power savings resulting from delegating the service discovery tasks to the server.

In this paper, we propose to combine active solid state drives and reconfigurable FPGAs into a storage-compute node to use as a building block in a distributed, high performance computation platform for data intensive applications. We propose a complete framework for middleware functionality through an API abstraction layer that hides the complexity of accessing and processing data stored on these distributed nodes, thus allowing programmers to focus on the application, and not the underlying specialized architecture. The application in turn is re-architected to maximize its performance by delegating selected computations down to the storage-compute node. We present preliminary results measured on a real hardware prototype of a single-node. These results show that our proposed architecture provides more than a 2× improvement in performance over non-reconfigurable active-disk architectures that use electromechanical disks for storage and a 6× improvement in performance over a platform that performs the computation on the middle server.

The Wireless Access in Vehicular Environments (WAVE) protocol stack is one of the most important protocols used to allocate spectrum for vehicular communication. In a previous work, we proved that WAVE does not provide sufficient spectrum for reliable exchange of safety information. More specifically, safety message delay is not acceptable and exceeds application requirements. In this paper, we propose a system that provides Data delivery guarantees using Cognitive networks principles in congested Vehicular ad hoc networks. We will refer to our system as DCV. Our goal is to ensure that all safety packets get generated and transmitted during the same interval. The system monitors the contention delay experienced by cars on the control channel where all safety packets should be transmitted. If the sensed contention delay exceeds delay threshold γ, the Road Side Unit (RSU) needs to increase the spectrum allocated to the control channel using cognitive networks. The RSU employs a feedback control design where additional bandwidth is added to drive the contention delay below the delay threshold γ used as reference input for the controller. Analysis and simulations indicate the effectiveness of the system in providing data delivery guarantees in vehicular networks and thus increasing safety measures on the road.

Wireless Access in Vehicular Environments (WAVE) protocol stack is the most important protocol used to allocate spectrum for vehicular communication. The capabilities of WAVE to provide reliable exchange of safety information are questionable. In a previous work, we suggested a system that employs cognitive networks principles to increase the spectrum allocated to the control channel (CCH) by the IEEE 802.11p amendment, where all safety information is transmitted. However, the decision making process implemented in that work does not differentiate between contention levels and does not relate precisely the measured contention to the amount of needed spectrum, which leads to an inefficient utilization of the white spectrum. In order to assign the minimum necessary additional bandwidth to relieve the contention, we suggest in this paper a new system that quantifies contention into multiple levels of severity based on Fuzzy Logic and maps additional spectrum correspondingly. Simulations show the effectiveness of the system in allocating the minimum needed bandwidth to relieve contention, without affecting other QoS parameters such as delay and number of untransmitted packets.

Organizations are starting to realize the significant value of advertising on mobile devices, and a number of systems have been developed to exploit this opportunity. From a privacy perspective, however, all “privacy-concerned” systems developed so far are based on either a trusted third-party model or on some generalized architecture. We propose a system for delivering location and preference-aware advertisements to mobiles with a novel architecture to preserve privacy. The main adversary in our model is the server distributing the ads trying to identify users and track them, and to a lesser extent, other peer in the wireless network. When the need for tailored ads arises, the node will form a group of nearby nodes seeking ads and will cooperate to achieve privacy. Peers combine their interests using a “shuffling” mechanism in an ad-hoc network and send them through a “primary peer” to the ad server. The result is that preferences of multiple peers are accumulated and masqueraded to request custom ads which are then distributed by the primary peer. Another mechanism is also proposed to implement the billing process without disclosing user identities.

The Wireless Access in Vehicular Environments (WAVE) protocol stack is one of the most important protocols proposed to standardize and allocate spectrum for vehicle-to-vehicle and vehicle-to-infrastructure communication. In a previous work, we proved that WAVE faces a spectrum scarcity problem which hinders reliable exchange of safety information. To overcome this problem, we proposed a system that applies cognitive networks principles to WAVE as to increase the spectrum allocated to the control channel (CCH) by the IEEE 802.11p amendment, where all safety information is transmitted. However, the decision making process in our previous work did not utilize the extra spectrum efficiently as it was not allocated according to the contention level experienced by the vehicle. In this paper, we suggest a system that employs a fuzzy logic system (FLS) to dynamically assign additional spectrum from the ISM band to the CCH. This system, which we call FCVANET, assigns the minimum necessary additional bandwidth to relieve the contention. The FLS takes as input 2 parameters, the message delay and the un-transmitted packets and utilizes a feedback loop. Our simulations show that the proposed system allocates bandwidth more efficiently in accordance with the contention level faced by the vehicles. The system succeeds to relieve contention by reducing delay and the number of un-transmitted packets.

Vehicular ad hoc networks (VANETs) enable vehicles to communicate with each other, but require efficient and robust routing protocols for their success. In this paper, we exploit the infrastructure of roadside units (RSUs) to efficiently and reliably route packets in VANETs. Our system operates by using vehicles to carry and forward messages from a source vehicle to a nearby RSU, and then if needed, route these messages through the RSU network, and finally send them from an RSU to the destination vehicle. Our system is mostly critical for far apart users who want to communicate using their on-board units (OBUs). We carry out an extensive mathematical analysis to study the performance of our system under different network conditions. We verify our analysis by comparing its results with the results of the simulations we performed using the ns2 software. The results prove the feasibility and efficiency of our scheme in terms of query delay, packet delivery ratio, and network traffic.

Vehicular ad hoc networks (VANETs) enable vehicles that are not necessarily within the same radio transmission range to communicate with each other and with roadside units (RSUs). The success of data acquisition and delivery systems in VANETs depends on their ability to defend against the different types of security and privacy attacks. The security of safety messages (like emergency and traffic information) has been the concern of VANET security researchers, and very few works dealt with the security of data messages exchanged between users and the infrastructure. This paper introduces a system that takes advantage of the RSUs that are connected to the internet and provide various types of information to VANET users. We provide a suite of novel security and privacy mechanisms in our proposed system, and evaluate its performance using the ns2 software. We demonstrate through comparing its results to those of another system its feasibility and efficiency.

This paper proposes a cache consistency scheme based on a previously proposed architecture for caching database data in MANETs. The original scheme for data caching stores the queries that are submitted by requesting nodes in special nodes, called query directories (QDs), and uses these queries to locate the data (responses) that are stored in the nodes that requested them, called caching nodes (CNs). The consistency scheme is server-based in which control mechanisms are implemented to adapt the process of caching a data item and updating it by the server to its popularity and its data update rate at the server. The system implements methods to handle disconnections of QD and CN nodes from the network and to control how the cache of each node is updated or discarded when it returns to the network. Estimates for the average response time of node requests and the average node bandwidth utilization are derived in order to determine the gains (or costs) of employing our scheme in the MANET. Moreover, ns2 simulations were performed to measure several parameters, like the average data request response time, cache update delay, hit ratio, and bandwidth utilization. The results demonstrate the advantage of the proposed scheme over existing systems.

Nodes in mobile ad-hoc networks (MANETs) acquire data from servers through access points. In order to minimize this interaction, data caching at mobile nodes is employed. This work builds on a recently introduced cooperative caching scheme that uses the query as an index to its response. When a new request is issued, nodes cooperate to find its answer and send it to the requesting node. This work semantically compares each request with all cached queries and implements a process that may trim the request into fragments and combine the answers of these fragments to calculate the total answer of the request. Our simulations show the advantages of the system when compared to other cache methods that are proposed for MANETs.

State of the art research currently aims at utilizing the new wireless capabilities in vehicles to handle road safety threats, relay traffic information, and provide vehicles with a broader sense of their surroundings. Additionally, multimedia and entertainment applications play a vital role in pushing new technologies. They require delivering large pieces of data to the widest possible public using specialized means of delivery. In the meanwhile, the BitTorrent protocol has become widely utilized for large file sharing. However, this protocol requires modifications to allow its use in the highly volatile vehicular ad-hoc networks (VANETs). This paper describes the work done to design algorithms for locating file pieces and gathering information about them. This represents the most challenging step toward applying a BitTorrent-like scheme for VANETs.

This paper introduces a message forwarding algorithm for search applications within mobile ad hoc networks that is based on the concept of selecting the nearest node from a set of designated nodes. The algorithm, which is called Minimum Distance Packet Forwarding (MDPF), uses routing information to select the node with the minimum distance. The goal of the proposed algorithm is to minimize the average number of hops taken to reach the node that holds the desired data. Numerical analysis and experimental evaluations using the network simulation software ns2 were performed to derive the lower and upper bounds of the confidence interval for the mean hop count between the source node of the data request, on one hand, and the node that holds the desired data and the last node in the set of search nodes, on the other hand. In the experimental evaluation, the performance of MDPF was compared to that of Random Packet Forwarding (RPF) and Minimal Spanning Tree Forwarding (MSTF). The results agreed with the numerical analysis results and demonstrated that MDPF offers significant hop count savings and smaller delays when compared to RPF and MSTF.

Due to the widespread of different types of hand-held computing devices whose bandwidth, memory size, and processing capacity are becoming comparable to those of desktop computers, mobile ad-hoc network (MANET) applications can now make use of proven distributed computing paradigms, in particular, web services. Indeed, in MANET environments, mobile computing devices can invoke web services methods to gain access to needed data, like stock quotes, currency exchange rates, etc. However, in addition to the communication costs, device mobility can cause temporary loss of connectivity to the server, thus rendering needed services inaccessible during those periods. For such reasons, caching of web service responses within the MANET can become beneficial for increasing data availability and reducing delays. This paper describes a distributed system designed for MANET environments to cache proxies of consumed web services and responses of their invoked methods. Furthermore, it analyzes the analytical and experimental performance of the system, and demonstrates the savings that could be realized after implementing it.

The rapid increase and proliferation of mobile wireless technologies has led to the rise of new problems that fall under the umbrella of challenged networks, namely, intermittent network connectivity. This diversity in wireless devices, along with their convergence, has granted users access to multiple heterogeneous networks available in parallel. Nowadays, a user generally expects to be connected in all places at all times. To better meet this expectation, we propose a system that takes advantage of intermittent connection opportunities while exploiting other networks available in parallel. We build our system over the parallel networks architecture, ParaNets, which suggests using heterogeneous networks simultaneously as data and control channels. Our system adopts the Data Bundling System for Intermittent Connections (DBS-IC), previously proposed as a stand-alone architecture for intermittent connectivity, and integrates it with the ParaNets architecture. We evaluate our system by fully implementing a ParaNets-enabled version of DBS-IC and thoroughly testing it over emulated network conditions. Characteristics of these networks are adopted based on real-life data on 802.11, 3G cell, and satellite networks. Our results show how minimal exploitation of parallel networks largely optimizes both cost and delivery rate.

This paper proposes a dynamic energy efficient clustering algorithm for mobile ad hoc networks (MANETs). The proposed algorithm elects first the nodes that have a higher energy and less mobility as cluster-heads, then periodically monitors the cluster-heads' energy and locally alters the network topology or the clusters to increase the network lifetime by reducing the energy consumption of the suffering cluster-heads. The algorithm employs two dynamically-computed energy thresholds: a yellow threshold that is used to achieve some sort of local load balancing by distributing the load equally among the adjacent cluster-heads, and a red threshold that is used to trigger local re-clustering in the network. Simulation results show that the proposed algorithm outperformed the weight clustering approach found in the literature.

This paper introduces a cooperation-based database caching system for Mobile Ad Hoc Networks (MANETs). The heart of the system is the nodes that cache submitted queries. The queries are used as indices to data cached in nodes that previously requested them. We discuss how the system is formed and how requested data is found if cached, or retrieved from the external database and then cached. Analysis is performed and expressions are derived for the different parameters, including upper and lower bounds for the number of query caching nodes as well as the average load they experience, generated network traffic, node bandwidth consumption, and other performance-related measures. Simulations with the ns-2 software were used to study the performance of the system in terms of average delay and hit ratio, and to compare it with the performance of two other caching schemes for MANETs, namely CachePath and CacheData. The results demonstrate the effectiveness of the proposed system in terms of achieved hit ratio and low delay.

Service discovery is indispensable to ad hoc networking where establishing a stand-alone and self-configurable communication environment is the main objective. This paper concentrates on designing a distributed service discovery model for service sharing among diverse mobile devices in mobile ad hoc networks. This model is built on top of the network layer of the TCP/IP stack and benefits from the up-to-date routing information enabled by proactive routing protocols that attempt to keep the information in the routing tables of the mobile nodes current. The designed system is based on storing service descriptions in selected nodes that are searched in accordance to a proposed Minimum Distance Packet Forwarding (MDPF) algorithm. In addition to identifying and analyzing the design parameters of the system, this paper studies the delay and traffic performance using analytical derivations and experimental evaluation based on the ns-2 network simulation software. The system is intended to be used in a collaborative mobile ad hoc network environment whereby a mobile node can consume services, share them, or facilitate such sharing by helping other nodes find them.

Testing web services impose many challenges to existing testing methods, techniques, and tools; especially those available to traditional applications. Composed web services increase these challenges by requiring additional validation and verification efforts. Structural-based testing approaches have been thoroughly researched for traditional applications; however, they have not yet been examined, as a methodology, for testing composed web services. In this work, we introduce a formal model for an abstract-based workflow framework that can be used to capture a composed web service under test. We then define a set of applicable structural-based testing criteria to the framework. Finally we outline a promising line of testing criteria that can be applied to this framework.

In today's MANET, nodes can be equipped with one or more wireless communications interfaces that support different wireless technologies such as WIFI IEEE 802.11 and Bluetooth. Each technology implements distinct hardware and logical specifications. Current AODV routing protocol becomes inefficient when used in a network formed of heterogeneous devices. Indeed AODV in its nature search the paths between homogeneous devices and ignore the ones between heterogeneous devices. In this paper, we propose a heterogeneous AODV protocol that interoperates between WIFI and Bluetooth technologies in a single MANET. The extended algorithm takes into consideration several factors when building the routes such as network stability, traffic, conversion rate; in addition to the shortest path.

IEEE 802.16 standard defines the specifications for emerging WiMAX networks. It did not however define the scheduling algorithms that determine the uplink and downlink bandwidth allocation. This paper proposes a preemptive deficit fair priority queue (PDFPQ) scheduling architecture for QoS management for the IEEE 802.16 standard. The proposed scheduling architecture is an extension of the DFPQ scheduling technique found in the literature. It enhances the QoS requirements of real time polling service (rtPS) flow class, and improves its delay and throughput. Compared to DFPQ, preliminary results show that a significant rtPS delay reduction and throughput increase can be realized with our new scheduling technique.

This paper describes an efficient Web page change detection system based on three optimizations that were implemented on top of the Hungarian algorithm, which we employ to compare trees that correspond to HTML Web pages. The optimizations attempt to stop the comparator algorithm that employs this O(n3) algorithm before it completes all its iterations based on criteria having to do with properties of HTML and heuristics. Analysis and experimental results prove the effectiveness of these optimizations and their ability to render O(n2) performance, where n denotes the number of nodes in the tree. A complete system was implemented and used to carry out the performance experiments. This system includes functionalities and interfaces for processing user requests, fetching Web pages from the Internet, allowing users to select zones in Web pages to monitor, and highlighting changes on the Web pages being monitored

This paper proposes a new model for caching Web service response data in a mobile ad hoc network (MANET). The aim is to enable any node joining the ad hoc network to either contribute services to other nodes or to consume services offered by other nodes. This model attempts to coordinate the service discovery and service use processes while maintaining minimal communication among nodes. The system comprises proxy caches (PCs), for acting as the interface to remote Web services and the internally cached service responses, request directories (RDs)for caching the cache keys that act as indexes to the responses, and finally, the caching nodes (CNs) that cache the responses. The CNs are the mobile nodes that requested the cached responses while the RDs are the ones that store the cache keys generated from the submitted requests and hold pointers to the CNs that store the responses. The PCs, RDs, and CNs are added (assigned) based on need according to capability criteria. Experimental results show the superiority of the system over non-caching and illustrate its performance in terms of delay and load versus hit ratio, which is a function of the system's caching capacity

Handheld devices in mobile ad hoc networks (MANETs) use different communication technologies (e.g., Bluetooth and IEEE 802.11) and are equipped with different software/hardware processing capabilities. This multi-level heterogeneity poses a serious challenge on the performance of MANETs and adds a number of characteristics, complexities, and constraints to their design. This paper proposes a communication abstract model that supports interoperability and coexistence between heterogeneous mobile devices. The model is represented through a three-layered paradigm: a communication service layer that deals with available communication capabilities; a communication capability layer that is responsible for controlling and managing the lower communication service layer and translating the high level functions of the available capabilities; and a communication interface layer that provides the applications with a unified public interface that supports various functionalities. Simulation results show that the proposed model, when used in a heterogeneous MANET environment, increases its performance in term of reliability and power saving, and yields a significant reduction in path length and delay

Learning associated with mechanical computer-aided design (CAD) poses challenges for both trainers and trainees. This article presents findings that relate to the acquisition of skills in utilizing a modern mechanical CAD tool, Pro/ENGINEER version 2000i2, to design models of low complexity. Empirical learning curves were generated and broken into declarative and procedural components, which were analyzed in an attempt to measure how and how fast trainees developed cognitive and motor skills. Results showed that there is an inverse relationship between the amount of improvement in performance time and the number of build features used in building a solid model. If production time is an overriding criterion, then efforts should be focused on teaching CAD trainees how to build mechanical solid models using small number of complex, more time-efficient features.

This paper proposes a model for caching database data in mobile ad-hoc networks through caching the queries and their responses. The approach makes a distinction between the queries and their responses and caches them on separate mobile nodes. This method is driven by the fact that queries do not become invalid unless when the design of the database entities changes while data changes depending on the application that feeds information into the database. The architecture we use is hierarchical and employs three types of designated nodes: a query directory (QD), service manager (SM), and caching node (CN). The one or more QDs are responsible for caching the queries and are assigned and supervised by the SM that also oversees the mobility activities and the availability of nodes in the network and makes "managerial" decisions accordingly, including appointing backup nodes. With this model, any node that joins the ad hoc network will either contribute services to other nodes (willingness to become an SM, a QD, or a CN) or consume services offered by other nodes. This model attempts to coordinate the query executing and query caching mechanisms in a seamless manner while maintaining minimal communication among nodes. We present preliminary results of a model that was simulated using the NS-2 software and show the viability of the proposed approach.

the IEEE 802.11e standard has been introduced recently for providing quality of service (QoS) capabilities in the emerging wireless local area networks. This standard introduces a contention window based enhanced distributed channel access (EDCA) technique that provides a prioritized traffic to guarantee the minimum bandwidth needed for time critical applications. However, the EDCA technique resets statically the contention window of the mobile station after each successful transmission. This static behavior does not adapt to the network state hence reduces the network usage and results in bad performance and poor link utilization whenever the demand for link utilization increases. This paper proposes a new adaptive differentiation technique for IEEE 802.11e wireless local area networks that takes into account the network state before resetting the contention window. The performance of the proposed technique is evaluated compared to the original differentiation techniques of the IEEE 802.11a and IEEE 802.11e standards. Preliminary results show that the proposed adaptive technique enhances the channel utilization and increases throughput.