The CSMA mode of operation was recently added to the LoRaWAN standard. We investigate, using a queueing model, how the introduction of CSMA in the communication between devices and the gate in LoRaWan may increase the probability of successful transmission. In the proposed model, customers (transmissions) are served by a multichannel station (gate), and the number of channels corresponds to the number of transmissions that can be performed in parallel. We introduce a queueing model with multiple attempts to find a free channel and investigate their impact on transmission throughput and reliability.

Vehicular Ad-Hoc Networks (VANETs) are essential for enhancing traffic management and road safety through vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication. Accurately predicting vehicle trajectories is critical yet challenging in dynamic traffic conditions. The paper proposes an optimized hybrid deep learning model combining Convolutional Neural Networks (CNNs) and Long Short-Term Memory (LSTM) networks to improve trajectory prediction. Simulation results on real-world datasets (GPS tracks of vehicles on highways and in urban areas) demonstrate higher prediction accuracy and efficiency, making the model highly effective for deployment in real-time smart city systems.

Resilient routing within low-power and lossy networks is essential to ensure the continuous and reliable operation of IoT devices. Standard RPL may struggle to adapt quickly and effectively to rapid changes in network conditions, such as link quality fluctuations, link failures, and varying traffic patterns, leading to suboptimal routing decisions, which can affect the QoS. In addition, IoT applications may express different QoS requirements that should be integrated within the routing decision. In this paper, we introduce a new extension of RPL, called Adaptive QoS-RPL, which can effectively adapt to changes in network conditions and node QoS requirements when building the DODAG. The experiments conducted using COOJA reported results that demonstrate the effectiveness of our solution compared to similar protocols.

This paper presents a formal specification of two techniques for resource allocation of processing nodes in a largescale Fog network, aiming to optimally handle service requests generated by a set of IoT devices. Fog computing extends Cloud computing services to the network edge by leveraging the computational resources of intermediate Fog nodes. Compared to Cloud resources, Fog resources are typically dynamic, heterogeneous, and constrained by latency and bandwidth. Improving the performance of Fog systems requires effective Fog resource management. To this end, we propose using the CSP process algebra to rigorously specify and validate the techniques we previously introduced, which are based on the stable and efficient Gale-Shapley matching algorithm for large-scale Fog computing networks.

Existing performance analyses and transmission policy designs under Time-Sensitive Networking (TSN) typically assume that all data flows are periodic and deterministic. However, in real-world scenarios, various sources of uncertainty - such as device failures, environmental variations, or upstream congestion - can lead to unexpected packet arrivals or losses, introducing non-deterministic behaviors into the network. This work develops a stochastic model based on Markov Decision Process (MDP) to capture the dynamics of TSN switch transmission under such conditions. To address the inefficiency caused by stale packets blocking fresher and more valuable ones, we propose a stale packet skipping policy to enhance the transmission efficiency. Specifically, a stale packet is discarded if a newer packet of the same flow is injected into the queue or if its deadline can no longer be met. This paper presents a detailed model description of the stochastic packet behaviors, the transmission system, and the stale packet skipping policy.

With the rapid expansion of smart cities, Intelligent Transportation Systems (ITS) are assuming an increasingly pivotal role. Among the multitude of tasks within ITS, traffic state forecasting stands out. As city boundaries grow, traffic forecasting encounters scalability and network transmission challenges. This research contributes to traffic state forecasting within large-scale, massive Internet of Things (IoT) scenarios. By investigating an urban expressway managing architecture that employs LoRaWAN communication, a novel deep learning-based model named Time Alignment based Temporal-Graph Attention Network (TATGaN) is proposed. Using the temporal-graph attention mechanism, TATGaN is able to extract temporal-spatial information and predict traffic state accurately. Moreover, the time alignment block makes TATGaN capable of handling irregular sequences given by the asynchronous arrival of packets. Simulation results based on OSM data of a specific region within Abu Dhabi show that TATGaN outperforms existing baseline methods in prediction performance with lower error and the higher reliability. Furthermore, the performance evaluation demonstrates the suitability of TATGaN for large-scale traffic network scenarios, attributing its efficiency to the transmission schedule and parameter mechanisms in LoRaWAN networks.

Improving urban mobility management has become increasingly challenging due to the rapid growth in both population and vehicular traffic, impacting the fluidity of mobility and leading to traffic congestion, delays, economic burdens, and adverse effects on public health. Moreover, there are significant concerns regarding air pollution, road accidents, and greenhouse gas emissions associated with this trend. Addressing these issues requires comprehensive strategies that prioritize sustainable transportation modes and urban planning to enhance efficiency and mitigate the negative impacts of mobility on the environment and public well-being. To address these challenges, cities must develop innovative strategies that integrate predictive models into their urban mobility planning. This paper presents a novel approach to predicting trajectories in Vehicular Ad hoc Networks (VANETs). Our proposed architecture leverages recurrent neural networks (RNNs) particularly long short-term memory (LSTM) to capture essential spatial features and temporal dependencies inherent in historical trajectories. Numerical results show that the proposed solution is efficient in terms of prediction.

In recent years, many research works have focused on RPL, especially in relation to the Internet of Things. This makes RPL an ideal data collection protocol for lossy environments where nodes have low energy levels and limited capabilities. In practice, RPL builds a tree-like topology, often represented by a destination-oriented directed acyclic graph that aims to transmit data to an LLN border router. Many multimetric extensions of RPL are based on a set of predefined metrics and an objective function; each node involved in the topology construction process goes through a parent selection by considering static weights for the set of metrics. The topology is periodically rebuilt to maintain the network while considering the same tools. To provide more flexibility, we present in this paper AOF-RPL, an extension of RPL which is designed to adjust the relevance of each metric based on the network's global condition and QoS requirements of the running applications. The problem is formulated using an MCDM method called ISOCOV. Simulations performed on COOJA show that our approach improves globally the performances compared to similar protocols while enhancing the network lifetime.

LoRaWAN (Long Range Wide Area Network) has garnered significant attention within the Internet of Things (IoT) due to its ability to establish a wireless network with massive devices over long distances while minimizing energy consumption. Our previous work shows its suitability for Intelligent Transportation Systems (ITS) scenarios. However, the utilization of the Aloha MAC protocol presents a challenge for LoRaWAN as it grapples with the presence of compromised nodes. These nodes may engage in greedy behaviors, disregarding network regulations to enhance their own performance or acquire additional network resources, and are often difficult to detect. This research contributes to machine learning-based greedy behavior detection methods. After proposing several end-to-end (E2E) methods with different ML algorithms, EDLoG (Encoder-based detection method of LoRaWAN Greedy behaviors) is proposed. It is a greedy behavior detection method combining a Multilayer Perceptron (MLP) encoder network and a statistical abnormal detection algorithm. The performance evaluations are conducted using simulation data under different scenarios given by MELoNS, a Modular and Extendable Simulator for the LoRaWAN Network developed in our previous work. The results show that the proposed method gives a detection recall 15%-20% higher than the baseline method by keeping a high detection precision. Moreover, the proposed methods show high timing efficiency with a running time much smaller than LoRaWAN’s time scale, making the method easily deployed to a real LoRaWAN network.

With the rapid growth of smart cities, Intelligent Transportation Systems (ITS) are playing an increasingly important role. However, with the rapid expansion of city boundaries, ITS faces scalability and energy consumption challenges. The wide range and the massive number of nodes have become significant issues for network technology in ITS. This study proposes an urban expressway managing architecture using LoRaWAN and edge computing. The traffic network is divided into different sections. A LoRa WAN network is established for monitoring and controlling each section by exploiting its low-power, long-range characteristics. Moreover, an edge computing-based traffic state encoder model has been proposed to handle the large amount of data generated by the massive number of nodes. The architecture's procedure allocates tasks to LoRaWAN devices by exploiting their different computing capabilities. Simulation results on real maps of both Abu Dhabi and Beijing demonstrate the high performance and scalability of the architecture. Numerical results also show that the encoder model can effectively reduce network packet size by extracting data features.

LoRaWAN is a network technology that provides a long-range wireless network at low energy consumption. In order to save energy, it takes the pure Aloha MAC protocol and the duty-cycle limitation at both uplink and downlink on the MAC layer. Moreover, LoRaWAN also adapts the orthogonal parameters to avoid the collision. However, the star-topology synchronization and the complicated collision mechanism make quantitative model analysis difficult in LoRaWAN. This study modeled the Class-A device in the LoRaWAN protocol using Probabilistic Timed Automata (PTA). It is a mathematical model that presents the nondeterministic and probabilistic choice with time passing. Using the time representation in PTA, the transmission schedule of LoRaWAN's MAC layer of is modeled. Moreover, the full collision model is built in the PTA. Several properties are verified with the probabilistic model checker PRISM, and the quantitative properties are calculated under different cases.

LoRaWAN (Long Range Wide Area Network) is rapidly gaining attention in the Internet of Things (IoT) due to its ability to provide a long-range wireless network at low energy consumption. However, with the Aloha MAC protocol, LoRaWAN faces the challenge of malicious behaviors from compromised nodes. Compromised nodes can take greedy behaviors by breaking network rules to improve their performance or obtain more network resources. This study proposes and investigates different greedy behaviors of infected nodes in LoRaWAN on the MAC layer. A straightforward double judgment detection method is proposed. The simulation results show that although the MAC layer of LoRaWAN is robust and resilient against greedy behavior by design, it can still be negatively affected by high-intensity greedy behavior. Moreover, the simulation results also show the high performance of the proposed detection method in different greedy behavior scenarios.

LoRaWAN (LOng RAnge radio Wide Area Network) is rapidly gaining attention with its capacity for a large devices number, long-range, and low power consumption. Many research works are carried out to evaluate or improve LoRaWAN’s performance in different application scenarios. However, because of a large number of connected devices and a complex environment, it is sometimes impractical to validate the studies with real test-bed or analytical methods. Therefore, the development of accurate network simulators is needed. More-over, extendability and flexibility are invaluable for a simulator to evaluate network performance in different scenarios and studies under a unified environment. To that end, this work presents MELoNS, a modular, extendable LoRaWAN simulator. By representing complete LoRaWAN transmission procedures at the different layers, MELoNS is suitable for the simulation of LoRaWAN in any scenario. MELoNS is lightweight and modular. The independence of network components gives MELoNS a high degree of freedom. Making MELoNS easy to implement and extend for different studies in the same environment. An example application of an intelligent traffic monitoring network is given to show the features of MeLONS.

In today’s urbanized world, cities are grappling with new challenges arising from population growth and rapid urbanization. Among these challenges, mobility stands out as a significant concern, as many cities were not initially designed to accommodate the surge in population. Enhancing mobility within smart cities has become a crucial endeavor in order to mitigate traffic congestion and promote sustainability by reducing greenhouse gas emissions. Additionally, improving mobility in smart cities contributes to enhancing the overall quality of life for citizens. Addressing vehicle behavior is crucial in reducing traffic congestion and improving commuting efficiency. Despite having robust infrastructures, disruptive driving habits such as aggressive driving, improper lane usage, and non-compliance with traffic rules can hinder the flow of traffic. By promoting responsible and considerate driving practices, we can optimize traffic flow and create a more efficient and stress-free commuting experience for individuals. Understanding the dynamics of mobility on highways is crucial for identifying the causes of traffic congestion. By analyzing these patterns, valuable insights can be gained, leading to the development of effective solutions for improving traffic flow. This study aims to investigate these aspects and propose strategies to contribute to overall mobility enhancements. To achieve this goal, a novel stochastic model based on the product form that accurately represents overtaking behaviors on highways is presented in this study. The model offers valuable insights into the dynamics of overtaking and provides a comprehensive understanding of this critical aspect of highway traffic. The paper presents a detailed model description and numerical resolution to calculate rewards such as delays and congestion.

LoRaWAN attracted lots of attention with its capacity for large device numbers, long-range, and low-power consumption. In order to simplify the transmission procedure, a pure Aloha protocol is implemented into its MAC layer. However, as the number of connected devices to the base station increases, the devices’ transmission parameters allocation becomes a vital issue related to network performance. This research contributes to the decentralized dynamic spreading factor (SF) allocation strategies during transmission by proposing a score table-based evaluation and parameters surfing (STEPS) approach. STEPS is a reinforcement learning-based method that evaluates and changes the parameters based on probability and score tables. It provides a nondeterministic parameter selection method by updating the table while transmitting. Some variants of STEPS with different algorithms are proposed. Moreover, an estimation-based initialization is proposed to improve learning performance. Simulations and statistical tests are carried out with MULANE, a lightweight LoRaWAN Simulator developed in our previous work. The results show that the estimation has a high confidence level. Compared with the baseline methods, the proposed methods reduce energy consumption by 24%–27% in different numbers of nodes. For bi-directional transmission, the proposed methods increase the 18% network throughput in a small number of nodes and 33% in a large number of nodes. Moreover, the proposed methods provide a framework of decentralized parameter allocation, which gives the extendability of this work.

LoRaWAN is one of the network technologies that provide a long-range wireless network at low energy consumption. However, the pure Aloha MAC protocol and the duty-cycle limitation at both end devices and gateway make LoRaWAN very sensitive to malicious behaviors in the MAC layer. Moreover, this kind of sensitivity makes the false-positives problem challenging for malicious behavior detection with simple threshold methods. This study investigates two malicious behaviors - greedy and attack on the MAC layer. Furthermore, by combining the threshold method with a Local Outlier Factor (LOF) model in machine learning, LoRaLOFT is proposed. It is a centralized malicious node detection method. Analytical results show that the proposed method gives high detection accuracy while significantly reducing the false-positive rate in both behaviors.

As one of the technologies in the wide-area network category, LoRaWAN provides a wireless network with a large capacity of end devices (ED) in long-range. With a pure Aloha protocol implemented into its MAC layer, LoRaWAN can reduce its power consumption. Besides, some orthogonal transmission parameters give LoRaWAN capability to avoid collision and packet loss. Thus, allocating transmission parameters to increase the network performance becomes a challenging issue for LoRaWAN. Some dynamic Spreading Factor (SF) allocation strategies are studied in this paper. A distributed Markov Decision Process (MDP) model is constructed for the uplink transmission of the class-A device in LoRaWAN. The model is also solved and implemented to the algorithms for the initial strategy prediction. Analytical results show that the MDP model increases the performance of the studied algorithms on the transmission of the packet.

The last decade has witnessed an ever-growing user demand for a better QoS (Quality Of Service) and the fast growth of connected devices still put high pressure on the legacy network infrastructures. To improve network performances, better manage the resources and have a greater control over traffic transmission, intelligent routing procedures are increasingly demanded. Modern applications in the dynamic context of new emerging networks have their own routing requirements, in terms of set of metrics to consider, their importance and thresholds to respect. The objective of this work is to design an approach based on MCDM (Multi-Criteria Decision Making) to decide complex routing problems when assuming threshold constraints on metrics. We give the mathematical framework to capture such requirements and to decide the routing. A case study is presented to advocate the benefit of using our approach.

As an original property of human beings, human emotion recognition has gained a lot of interests of many researchers. The recent emotion recognition scheme using wireless signal is considered as one of emerging techniques toward intelligent smart cities. It is highly reasonable to form virtual emotion barrier that can detect human emotion when people move from one side to another side through at least one device in the barrier using wireless signal. Also, it is critical that the emotion recognition delay by virtual emotion barrier with possible two-way detection must be minimized to provide emotion-based services to citizen in timely manner. In this article, we introduce a virtual emotion detection model with two-way enabled delay bound, which pursues to provide timely emotion-based IoT services in advanced smart cities. Also, we formally define a problem whose objective is to generate two-way enabled virtual emotion barriers such that the virtual emotion detection maximum delay of those barriers should be minimized. Then, we propose a novel Two-Way-Enabled-Border-Slab scheme and evaluate its performance through extensive simulations with various settings and scenarios. Furthermore, relevant to the proposed system, we discuss possible research issues, challenges and future works.

LoRaWAN (LOng RAnge radio Wide Area Network) belongs to the LPWAN (Low Power Wide Area Network) category, it aims to provide a wide area, long range and low power consumption communication network solution. However, with the large number of connected devices to the base-station and a pure Aloha MAC protocol, the packet lost and collisions become an important issue in the network related to the transmission parameters of the devices. For this issue, STEPS is proposed in this study. The goal of the proposed method is to establish a score table based evaluation and parameters surfing approach. STEPS provides an approach of evaluating and changing the parameters based on probability and score table when transmission failure appears. It can also update the table while transmitting. STEPS is compatible with pure Aloha, and doesn't need any change on the MAC protocol and is easy to be implemented. In this study, the spreading factor is chosen as the parameter to establish the table, that will be evaluated and to be surfed. Simulation results show that STEPS provides a remarkable improvement on bi-directional transmission of the packet and a capability of decreasing the packet lost and collisions even with higher data rate than classical LoRaWAN scenario.

Nowadays, small objects endowed with a communication device are collaborating to execute specific tasks. Due to their large number and limited capabilities, they are being supported by Low Power and Lossy Networks (LLNs). LLNs are often used in data collection oriented applications in which nodes collect data and forward it to a border router using the RPL protocol. RPL is a standard routing protocol which has been especially designed for LLNS. To introduce more interoperability and flexibility in RPL, DUAL-MOP RPL has been designed, thus enabling nodes having different Modes Of Operations (MOPs) to function in the same network. However, to solve the long source header problem, in DUAL-MOP RPL, a large number of source routing operations are being executed which conducts to a high processing load. To tackle this issue, we introduce in this paper an extension of DUAL-MOP RPL called ODM-RPL that proposes a trade-off between the source routing header length and the storing nodes' processing load by first optimizing the source routing header and introducing a concept of preferred source routing header maximum length. The simulations results show the effectiveness of our solution in terms of performances.

As one of the LPWAN categories, LoRaWAN attracts great attention on IoT and M2M communication. It offers a comprehensive area communication network solution with a low data rate and low power consumption. Many research works on medium scheduling or resource allocation have been proposed to improve network performance. However, with many devices in the network, it is sometimes too difficult to deploy a test-bed to evaluate the network performance in the industry. However, different studies often use different simulators. Thus, it is also challenging to study the impact of different algorithms on the network by simulation. Thus, an extendable simulator becomes necessary for both industrial networks deploying and academic study. In this paper, we developed a lightweight, extendable simulator exclusive to LoRaWAN named MULANE. We also offered a GUI is to simplify the simulation process. Moreover, the simulator is agent-oriented, making the research works implementation easier by creating new agents,

In the last decade, we observed an exponential growth in the number of smart objects. These devices designed to enhance human well-being, are able to communicate and cooperate with each other to form the IoT (Internet of Things). However, the IoT is facing many challenging issues to be a widespread technology, such as: battery lifetime limitation, poor computing and storage resources capacities. To cope with that, the Cloud model has been integrated and rethought to bring more flexibility in the way the resources are managed in the IoT. Such a solution provides potentially unlimited computing and storage capabilities as well as many other services. In the literature, numerous architectures have been proposed to combine these two new technologies by introducing emerging computing paradigms such as FOG computing, EDGE computing, Mobile Cloud computing. In this paper, we survey the existing IoT-CLOUD architectures and we classify them by proposing a new taxonomy based on appropriate criteria.

Nowadays, Internet of things (IoT) is becoming the trademark technology for connecting real-world physical entities to provide specific services and enable the creation of a smart world. Due to the growing number of connected objects and the lack of standardization that meet IoT requirements, discovering and selecting the desirable service is becoming a challenging issue. In the literature, many works have been put forward to address service discovery in IoT. In this paper, we propose a complete classification of these works to provide a more elaborated taxonomy that includes several aspects and criteria. Then, we compare some of the most recent approaches according to several performance criteria, followed with a discussion to set up the future research directions.

Human emotion recognition has attracted much interest of researchers since it can be utilized for various applications and communication software services. For emotion recognition, there are several approaches including facial expression, human motion. In particular, the emotion derivation through wireless signal and its reflection has been developed recently. Also, a concept of virtual emotion barrier has been introduced, which the emotion can be detected by the built virtual emotion barrier. Because human emotion can be changed frequently, the emotion detection delay through virtual emotion barrier should be minimized for possible accurate emotion recognition. In this paper, we introduce delay bounded virtual emotion barriers in IoT-enabled smart cities, which deliberate on the minimum virtual emotion detection latency among the constructed virtual emotion barriers for next generation software services. Then, we formally define a problem whose goal is to create delay-bounded virtual emotion barriers in IoT-enabled area such that the virtual emotion detection maximum delay among virtual emotion barriers is minimized. To solve the problem, we devise a novel scheme which admits virtual emotion recognition with minimum delay. Furthermore, the performance of the proposed approach is evaluated through extensive experiments.

In recent years, more and more functionally similar Web Services are offered to users. Quality of Service (QoS) parameters are used to characterize their performances and thus to facilitate their selection. Nowadays, clients are demanding more sophisticated services rather than those offered by single web services. Therefore, selecting a composition plan of web services among numerous choreographies by re-using existing services satisfying user's requirements has become a very challenging issue. QoS aware service composition aims to satisfy user's QoS needs during service composition. Traditional methods simply attempt to maximize user satisfaction by provisioning the composite service instance with the best QoS. These approaches do not consider in general that there are many consumers that are competing to acquire the same services. This could impact negatively the overall QoS and the decisions to take in the selection process. To respond to this particular problem, we propose a formal methodology based on Discrete Markov Chain to evaluate the performances of the QoS aware Web service composition system with multiple communities of consumers. The goal of this methodology is to help the designer to predict some useful performance parameters as the average time to reach a given QoS for a community of consumers in a competitive environment. The theoretical modelling of the problem is provided together with analytical results obtained by simulations using the Xborne tool.

The aim of the current research is to define a new MCDM method that has the ability to rank Web services when value constraints are expressed on QoS criteria. This method is called, ISOCOV (Ideal SOlution with COnstraint on Values). In presence of values constraints, the majority of existing MCDM methods proceeds either by discarding from the research space all the non satisfactory Web services, or by providing a partial integration of the requirements in the decision making process. On the contrary, ISOCOV takes into account all the aspects thus providing to the user a more accurate solution while dealing with the given constraints. The purpose is to be able to promote services that do not meet the constraints, when the cleaned research space stands empty or not representative enough. A case study using a real dataset is considered to highlight the functioning and the accuracy of our method comparatively to other similar MCDM approaches.

Web service composition is the process of combining Web services in order to offer value-added services that meet the increasing complex requirements of business processes. Besides simple Web services described with WSDL, OWL-S language allows to describe composite semantic Web services offering multiple operations using complex control structures. However, it becomes harder to manually check the consistency of orchestrations of such services in order to guarantee their correctness and avoid deadlock and erroneous statuses. In this paper, we first propose a formal method for translating OWL-S composite services into communicating automata using an iterative process which is driven by the control structure of that language. The same approach is also applied to the orchestrator whose description is given in WS-BPEL. Thereafter, we build up the synchronization product of the resulting automata and proceed to its consistency checking in order to unveil any forbidden statuses which depict flaws in that orchestration interaction protocol.

In this paper, a seamless virtual emotion system is introduced toward appropriate emotion-based services in advanced IoT-enabled smart cities. The proposed system is supported by virtual emotion barrier with replaceable detection and hole-free property, which recognizes human emotion using wireless signal. Also, we formally define a problem with ILP formulation whose goal is to maximize the lowest detection accuracy with weak hole in replaceable barrier in order to construct seamless replaceable hole-free virtual emotion barrier ultimately. Then, a novel scheme is proposed to solve the problem. Moreover, we perform the proposed approach through extensive simulations with various scenarios and its performance is evaluated with detailed discussion.

Service composition is a primary task in the development of service-oriented systems. The Web Service Process Execution Language (WS-BPEL) and the Web Service Choreography Descriptor Language (WS-CDL) are two major languages for Web services modeling and implementation. Although these two composition models are of a different nature, they are complementary. WS-CDL serves as a behavioral modeling language for collaboration between multiple participants (web services) within the same business process from a global point of view. However, WS-BPEL allows a service composition process to be described at different levels of abstraction. At a high level, the description follows a global point of view and deals only with the exchange of messages between participating abstract services (represented abstractly by roles). WS-CDL descriptions are thus considered as a specification of the abstract service composition from which more concrete WS-BPEL processes are extracted. In this article, we present a formal modeling and analysis approach based on sequential communication process (CSP) in order to verify the behavioral consistency between abstract choreographic descriptions and executable BPEL processes, thereby proving the correctness of the translation process.

Summary The aim of the current research is to develop a more accurate Web service selection approach that can deal with value constraints on QoS criteria in the user request. The purpose is to be able to promote services even when all the value constraints are not satisfied and hence rank them according to their closeness to meet the latter. For this effect, we use MCDM (Multi Criteria Decision making) methods together with suitable normalization techniques at different stages of the process. First of all, we consider an extension of the AHP method to compute and normalize the weights associated with the QoS criteria considered in the Web service selection. Second, we introduce a more consistent normalization technique, called OMRI, to normalize data according to value constraints. Third, we propose to extend different ranking MCDM methods to the OMRI normalization so that it becomes possible for them to cope with value constraints. The considered methods are SAW, TOPSIS, VIKOR, and WPM. To compare the accuracy of the extended ranking methods, we use the Borda compromise solution together with different similarity ratios. To validate the solution, several experiments have been conducted on a real dataset as well as on an artificial one.

With the explosive growth of mobile multimedia traffic, the problem of allocating computing and spectral resources for very low latency services become a challenge for next generation mobile networks. We exploit all the benefits of a completely virtualized environment, where mobile virtual network operators (MVNOs) and virtual service providers (VSPs) are connected in the Cloud through network as a service (NaaS) using distributed infrastructure as a service (IaaS). VSPs provide services according to Internet of things (IoT) devices requests including software as a service (SaaS) and emerging caching techniques Cache as a Service (CaaS) to satisfy the quality of service (QoS) requirements. Thus, we propose a many-to-many matching game between the sets of IoT devices and the set of virtual service providers (VSPs). To solve this game, we exploit the deferred acceptance algorithm that enables the players to self-organize into a stable matching and a reasonable number of algorithm iterations. To highlight the effectiveness of our approach for the on-demand services, we applied it on two typical services requiring ultra- reliability and low-latency communications (uRLLC): The intelligent transport and the video on-demand services. Simulation results has demonstrated that our proposed matching strategy coupled to CaaS caching capabilities on distributed F-RAN significantly outperforms the traditional strategies in terms of latency and network traffic load.

A barrier-coverage has attracted much interests of researchers because it can guarantee to detect any movement of mobile objects. Also, thanks to recent advancement of technology, it is possible to recognize human emotion by facial expression and human motion or activity. Then, the emotion recognition can be applied to various services and applications appropriately. Recently, it has been developed to sense emotion by wireless signal. One of issues for emotion recognition is to increase the recognition accuracy. In this paper, we introduce a new type of barrier, virtual emotion barrier, which is able to detect emotion by devices with wireless signal in Internet of Things (IoT) environment. Then, we formally define a problem whose objective is to construct virtual emotion barrier in the given area including IoT devices such that the detection accuracy of emotion by virtual emotion barrier is maximized. To solve the problem, we propose a greedy-emotion-accuracy approach. Moreover, we discuss future issues and possible research directions for virtual emotion barrier.

Wireless Sensor Networks (WSNs) are formed of a set of tiny autonomous entities interconnected by wireless communication links. These entities cooperate to collect and transmit measures taken from their environment. WSNs are characterized by a limitation of their battery, processing power and storage memory, which makes the consumption energy saving a real challenge. However, WSNs are deployed in open radio frequency and lack of physical security. Thus, these networks are vulnerable to several attacks: passive eavesdropping; active attacks; identity theft. In this paper, by using Stochastic Automata Networks (SAN), we propose to model our proposed method named Accordion method in order to detect and apprehend Denial of Service attacks (DoS).

MANETs (Mobile Ad hoc NETworks) are characterized by a dynamic topology and generally deployed in a hostile environment with limited resources. Therefore, the design of fault tolerant applications in this environment is paramount as nodes are often subject to failures. We exploit in this paper a solution based on geographic area node repartition to provide a virtual centralization of the network to monitor the failure detection procedure. Hence, we define our protocol called, ARFAD (Area Repartition Failure Detection) that allows a fast detection of a failure while reducing significantly the traffic overhead. We report simulation results performed on NS2 platform that compare the performances of ARFAD with a recent protocol.

A recent proliferation of UAVs accompanies several critical issues to be considered for efficient, secure use of UAVs. One of those issues should be a privacy of people. Also, when the UAVs fly to perform specific objectives, minimizing movements of UAVs is a big issue to provide a minimum mission completion time and a maximum network lifetime. One intuitive solution is that UAVs may pass through private area of citizens whereas people do not want any penetration into own area without a permission. Then, we may take into account a compromise between those situations by giving a differential permission for each UAV to access citizens' areas depending on specific benefits by use of UAVs or emergent situation for public safety. In this paper, we introduce a framework for privacy-preserving movements of UAVs with differential UAVs' permissions given by citizens. Then, we formally define a problem whose objective is to minimize total movements of UAVs with preserving privacy of people. To solve the problem, we create a new graph type called as UDiPP graph and propose a novel priority-based approach. Furthermore, we discuss future issues and directions for differential privacy-preserving movements by UAVs.

Congestion in Wireless Multimedia Sensor Networks (WMSN) may cause packet loss, buffer overflow and increases queueing delay, which has a significant negative impact on the network performance and reliability. This problem imposes more resource constraints that involve energy consumption and buffer size to meet additional requirements such as desired buffer size and limited amount of packet loss. One of the fundamental issues of congestion problem in such networks is the queue management. In fact, handling congestion without considering flexible buffer management and queueing methods, stay insignificant against dropping rate and packet loss. Consequently, a novel congestion control approach is needed to overcome these problems. In this paper, a new queue management mechanism called: Priority Queue Management based Explicit Congestion Control (PQMECC) is proposed and modeled using Stochastic Automata Networks, which are appropriate for modeling and analyzing complex systems with interacting components and complex synchronization. The congestion control technique used in PQMECC is based on priority, load repartition mechanism and explicit congestion notification which is generated only if the congestion reaches the threshold value.

In this article, we propose to use game theory to model our WSN network. In this setting, the goal of the compromised node is to keep disrupting the network while remaining alive. The game studied is a two-player quantitative infinite game on a finite graph, where each transition can change some energy levels and some reward. The goal of the compromised node is hence to maximize its reward while maintaining a positive energy level. On the theoretical side, we show that solving these games is not algorithmically possible if the objective is too complex. We can however provide solutions in some restricted cases. The ultimate purpose is to demonstrate that, with the presented detection solution, a compromised node cannot “win the game”, and hence either gets detected, dies, or behaves as an normal (sane) node would.

The congestion control is one of the most important challenges in wireless sensor networks, which has a significant negative impact on the QoS of these networks. The aim of this paper is to propose a novel queuing and service management mechanism for congestion control, called QSMCC and then its modeling and performance analysis using the Continuous Time Markov Chains formalism. QSMCC is based on Priority and Round Robin policy for wireless sensor networks and uses explicit congestion notification which is generated when the occupancy rate of the queue reaches a threshold. To this end, a sensor node uses two logical queues to store the incoming and locally generated packets. The first queue consists of congestion notification packets (CN) and the second one consists of data packets (D). In addition, we develop the formulas of the main stationary performance measures, as a function of the network parameters and the occupancy rate of the queues. Through numerical examples, we discuss and compare the impact of applying Priority and Round Robin policies on a sensor network based on queue utilization, latency time and lost packets.

Nowadays, web service selection has become a very challenging issue. As the number of web services is increasing drastically, different QoS parameters are added in their description in addition to their functional parameters (Inputs and outputs) to distinguish them and ease their selection. Hence, web service selection consists to find out among services having the same functionalities the optimal elements that satisfy user QoS requirements. When the user request deals with value constrains on the QoS parameters, the mainstream approach operates by removing from the search space web services that do not satisfy the user constraints. However, such an approach is not always appropriate especially when the resulting search space is empty or very small. In this case, the discarded services may be of interest in the selection process. To tackle this issue, we propose to use a combination of two MCDM (Multi Criteria Decision Making) methods, that are AHP (Analytical Hierarchy Process) and RIM (Reference Ideal Method). AHP is used to encode an normalize weights constraints assigned to QoS criteria at the first stage. Then to deal with user value constraints, we consider RIM to rank discarded web services relatively to their proximity to the required value constraints. We compare our method with existing approaches by performing tests on a real dataset.

With the diversity of services and the need of different traffic classes in wireless networks, WIMAX technology (Worldwide Interoperability for Microwave Access), has been developed as a broadband wireless access technology based on IEEE standard 802.16. Indeed, this technology is able to mix real time and non real time services with the definition of service classes. To improve the admission rate of the different classes when implementing the admission control component, we propose in this paper a traffic scheduling based on WRR policy and a new mechanism to handle the rejected requests. Finally, we provide the Markov Chain based modelling of our solution and compute thereof primary performance evaluation results.

The wireless shared medium used by Wireless Sensor Networks applications causes a problem related to interference, specially with dense deployment that characterizes the WSNs. This requires the use of congestion control scheme to avoid interferences and buffer overflow that degrade the application reliability. REFIACC (Reliable, Efficient, fair and Interference aware Congestion control) schedule scheme is a cross layer congestion control protocol that avoids the aforementioned problems while maximizing throughput and fairness. In our previously studies, we have validated REFIACC using extensive simulations. In this study, REFIACC is modeled using Stochastic Automata Networks (SAN). In fact, SAN presents a good tool to avoid state-space explosion of Markov chains.

Summary The use of wireless sensor networks (WSNs) has increased rapidly over the last years. Due to their low resources, sensors come along with new issues regarding network security and energy consumption. Focusing on the network availability, previous studies proposed to protect clustered network against denial of service attacks with the use of traffic monitoring agents on some nodes. Those control nodes have to analyze the traffic inside a cluster and to send warnings to the cluster head whenever an abnormal behavior (e.g., high packets throughput or non‐retransmission of packets) is detected. But if the control nodes (cNodes) die out of exhaustion, they leave the network unprotected. To better fight against attacks, we try to enhance this solution by renewing periodically the election process. Furthermore, we propose three energy‐aware and secure methods to designate thecNodesin a hierarchically clustered WSN. The first one is a simple self‐election process where nodes randomly designate themselves. It leads to a better load balancing than a static method (i.e., with no renewal), but we argue that we can obtain better results by considering the remaining energy of the nodes atcNodesselection time. Hence, the second algorithm is purely based on the residual energy of the sensors. We discuss limitations of this deterministic process concerning security and cluster coverage and suggest workarounds. These improvements lead us to the third mechanism. It is based on residual energy too, but it includes a democratic election process in which nodes in the cluster vote to optimize thecNoderole attribution. Results obtained from simulation experiments with thens‐2tool are provided to analyze the energy repartition in the network and to compare the three selection algorithms. All experimental outcomes show improvements of the load balancing in the network, while maintaining good detection coverage, in regard to static selection. Furthermore, the analysis of the respective performances of the three mechanisms is used as a basis to establish recommendations regarding the use cases of those methods. Copyright © 2017 John Wiley & Sons, Ltd.

Recent trends in mobile cellular networks turn towards deployment of Small Cell Networks (SCNs), where the cell size gets smaller and thus the number of subscribers served in a cell will be relatively smaller and should be considered finite. However, almost works on cellular mobile networks consider an infinite population cell, resulting commonly in infinite queueing models, for which no analytical solution is available for performance measures and only numerical approximations can be obtained. In this paper, a Call Admission Control (CAC) in a finite population micro-cell operating in a SCN, with retrials of blocked new calls, impatience of subscribers and multiple guard channels dedicated to handoff calls, is proposed. For the numerical computation of the steady-state probabilities of the corresponding continuous time Markov chain (CTMC), an efficient algorithm giving automatically the infinitesimal generator is developed, and various performance measures are established in network parameters and stationary probabilities. The guard channels number and retrials effect on the network performance in terms of blocking probability (for new calls and retrials) and dropping probability (of handoffs) is also carried out via experimental results.

Wireless Sensor Network (WSN) has recently emerged as a new widely used technology. However, the deployment of such networks has reported high rates of failures. Due to resource constraints of sensor nodes, the design of efficient failure detection techniques has become a very challenging issue. Already proposed WSN fault detection protocols have reported either a high number of false suspicions, or slow detection times, even an important message overhead which impact negatively the resource consumption of the nodes. In this paper, we propose EAFD (efficient and accurate failure detector), a novel protocol for failure detection for clustered WSNs. This protocol exploits two levels of suspicions to decide the failure of a node, as well as computation messages to disseminate the heartbeat of nodes during the detection process. Thereby, EAFD achieves a better compromise in terms of accuracy and completeness, as well as message overhead. Primary simulation results, found that our protocol outperforms the protocol AFD.

Recent advances in wireless network technologies, like the ability to operate in a high-speed mobility environment, have opened up to a number of domains such as that of Intelligent Transport Systems (ITS) whose main component are so-called Vehicular Ad hoc Networks (VANETs). VANETs are associated with two kind of deployments: vehicular to Infrastructure (V2I), managing communications between vehicles and a fixed infrastructure, and Vehicular to Vehicular (V2V), for communications between vehicles. Since VANETs obey to the principles of mobile ad hoc networks, hence connections are established in a spontaneous and distributed manner, they suffer from lack of Quality of service guarantees as the access is not bounded. Modeling of VANETs is a complex task, as there are a number of factors that negatively affect the state-space dimension (i.e. the number of considered vehicles, the considered traffic, the mobility management). In this paper we introduce a formal model, in terms of a Markov chain, of the IEEE 802.11p MAC protocol, the basic access control mechanism employed in VANETs. Such model is the basis for computing relevant performance measures of the VANETs.

The fast growth of the number of deployed Web services is transforming the enterprises from data-oriented systems into service-oriented systems. In this context, the selection of the best web service that satisfies specific QoS values among a group of web services with similar functionalities is becoming a challenging issue. To this aim, we investigate in this paper a methodology for web service selection that combines three techniques. First of all, we use skyline to reduce the research space, then BWM (Best Worst Method) to assign weight to QoS criteria and finally we exploit Vikor to rank the obtained skyline web services. We report the experimental results that compare our approach with Topsis and Promethee methods.

To guarantee fault tolerant system, checkpointing protocols are usually run to save the last consistent state of the system. This information will be recovered whenever a node failure occurs, thereby making it possible to resume the execution of the system. In the context of MANETs, checkpoints need to be saved in a safe and a stable storage to avoid data loss. Due the the specific constraints of such networks, the implementation of a stable storage (SS) is a hard task to achieve. So far, the most used techniques are based on mirroring or replication. However, although the latter achieve a safe an a reliable implementation of the SS, the deployment and the maintenance of the SS remain very costly. We explore in this paper a solution based on a distributed implementation of the SS by using RAID5 storage scheme. Mobile agent paradigm and geographic areas repartition of nodes are exploited to provide a virtual centralisation of the system. We associate this solution with a recent checkpointing protocol to provide an efficient fault tolerance tool for MANETs. Simulation results performed on NS2 show that our solution outperforms clearly replication.

Failure detection in distributed systems under MANET environment is a hard task to achieve. Indeed, due to mobility and resource constraints, traditional protocols record a high number of false suspicions. We propose in this paper a new failure detection protocol for MANETs that achieves a better compromise in terms of accuracy and completeness, by introducing new mechanisms to correct false suspicions. Simulation results are reported to compare the performances of our protocol with other approaches.

The aim of this paper is to give a detailed modeling and performance analysis of Small Cell wireless Networks considering the limited number of mobiles served in each cell and different vacation schemes of the base stations channels, using the Generalized Stochastic Petri nets formalism. Hence, we show how this high level formalism allows a simple construction of detailed and compact models for such networks by considering single and multiple independent vacations of channels or all the base station in the case of synchronous vacations. In addition, we develop the formulas of the main stationary performance measures. Through numerical examples, we discuss the impact of channels number of the base station, vacation rate and vacation scheme on the network performances.

In this era of big data, of quantified self and of smart cities, wireless sensor networks are meant to be used every day, for all sort of applications. Made of tiny sensors, they collect data and communicate through wireless technologies. Because they may take part in sensitive or military applications, security is an essential matter in such networks. Confidentiality and authenticity can be ensured by the use of dedicated mechanisms. Focusing on availability, we propose here a new practical approach to protect the network against denial of service attacks thanks to the use of traffic monitoring agents called cNodes. The approach uses a fair election process of cNodes in accordance with classical criteria related to residual energies and the presence of compromised nodes which may have greedy or jamming behaviors. Results obtained from simulations show that this method is effective both in terms of detection and of energy conservation.

Wireless Multimedia Sensors Networks are characterized by a high consumption of network resources such as energy and bandwidth. This consumption is caused by the large amount of data flowing across the network. One of the mechanisms used to reduce the consumption of resources is data fusion to eliminate redundant transmission while synthesizing the relevant information. However, as data fusion can operate only on specific nodes, called fusion agents, an important amount of data still remains sent from sensor nodes to the fusion agents. In this paper, we deal with the fusion of Multi-focus images. In such applications the totality of the images are sent from the cameras to the fusion agents before to be fused, which results in a huge consumption of the network resources. To tackle this issue, we propose a transmitting strategy that determines the useful information to send. This is achieved by computing different similarity coefficients at different levels. The values of the similarity thresholds are adaptable making it possible to cope with the context of the network and the running application. Primary simulation results show the effectiveness of the proposed mechanism in terms of network resources consumption and delay transmission.

Sensor networks are tiny independent devices which are characterized by limiting battery, processing power and storage memory, that makes saving consumption energy as real challenge power. Morever, there are many techniques used used to conserve energy in Wireless Sensor Networks (WSNs) the clustering technique is one of them. In terms of security, WSNs are more vulnerable to attacks than wired networks. However, radio frequencies used in WSNs are open, making the eavesdropping fairly easy. By considering energy consumption and in order to prevent from Denial of Service (DoS) attacks, present study introducing a preventing DoS attacks approach, which is based on using clustering techniques.

In this paper we present a formal modeling and analysis approach of the IEEE 802.11 CSMA/CA protocol in wireless local area networks (LANs) whose some greedy stations have selfish behaviors. Such stations do not strictly comply with rules of CSMA/CA protocol in order to increase their chances to access the channel at the expense of normal stations. We capture the behavior of wireless stations correctly implementing the DCF functioning mode of CSMA, along with compromised stations and the wireless medium using communicating timed automata which are the modeling language of the UPPAAL model checker. We proceed as well to the checking of some safety and liveness properties by means of this tool. We also propose stochastic models and we give some numerical results.

Nowadays, QoS parameters are more and more integrated in composite web service architectures. The performance evaluation of the latter is becoming a challenging issue, as it demands to satisfy complex synchronization as well as different requirements. We investigate in this paper the use of Time Petri Nets (TPN) for modeling and analyzing the behavior of such architectures in the aim to compute the mean response time of requests and the throughput. We consider here the case of the Fork-Join architectures with a fixed number of invoked elementary services. We show how to model this architecture while assuming queue's constraints as well as Timeouts. We simulate the obtained TPN models under different loads to compute the considered QoS parameters.

In this paper, we deal with failure detection in distributed systems under mobile environment constraints. For this effect, we propose a new protocol, called AFDAN (Accurate Fault Detection Protocol for Ad hoc Network), that is in charge of monitoring the distributed application against any node failure. The simulation results of our protocol show good performances in terms of accuracy and message overhead comparing to other protocols dedicated for MANETs.

IEEE 802.16 well known as WIMAX is defined as the standard of Broadband WMAN networks. This technology is able to mix real time and non real time services with the definition of service classes. To efficientlty schedule traffics of different classes, we proposed in a previous work a token bucket based scheme and evaluated its performances by means of probabilistic models. In this paper, we explore the use of TPN (Time Petri nets) for deterministic performance evaluation in order to compute quantitative and qualitative properties. We show how to model two different strategies of traffic scheduling by using TPN model extended to logical inhibitor arcs. The first strategy is based on strict priorities between traffics, the second is based on token bucket mechanism. Then in order to improve the efficiency of the latter scheme, we propose to extend it to a QoS-management mechanism. Then we simulate the obtained models by using the tool TINA in order to evaluate their performances when varying the load of the system. Preliminary results show that token bucket extension provides better figures in terms of service delay, than other schemes, in case of high service loads while maintaining fairness and priorities between traffics.

Researchers have payed more and more attention on security issues in wireless networks this last decade as those networks are exposed to Denial of Service (DoS) attacks. Last improvements of the wireless technologies has developed the possibility to cars to communicate with Vehicular Ad Hoc networks more known as VANET. In these networks the impact of DoS is more important as it can affect the life of passengers. The features of DoS attacks are not well known in VANETs, thus we propose in this study a new Analytical model that represents the behavior of jamming attack in VANETS. This DoS attack consists of a node that disturb/disrupt the communications between nodes, then the overall quality of service is decreased. Representing this attack by analytical model using Markov chains is impossible as we face a problem of a state space explosion, thus we have used a more appropriate concept that is not usually used in the security in wireless networks with Stochastic Automata Networks. This model was used to calculate the rewards of this attack and can be used to decide whether a network is under or not a DoS attack.

With the advent of new technologies in the area of wireless systems and communications, there is an increasing need to develop distributed applications that take into account mobility constraints while being fault tolerant. Indeed, this environment is very sensitive to failures. Among the existing techniques, we focus on the rollback recovery that is best suited for this kind of situations. The rollback recovery requires to save regularly (in the background of the distributed application), local states of nodes; this task is called checkpointing. Thus, the system will resume (after repairing or replacing the failing node) from one of these states (checkpoints). To launch the rollback recovery, it is necessary to define a protocol that has the ability to detect all the failures while reducing the rate of false suspicions. Therefore, the definition, the verification and the performance evaluation of failure detection protocols is a crucial stage to achieve. In this paper, we show how to model the behavior of already defined fault tolerant protocols: FDAN (failure detection protocol), 2P ACA (checkpointing protocol) by using stochastic Automata Networks (SAN). This makes it possible to verify their coherence and evaluate their performances by using dedicated tools.

The use of sensor networks has increased rapidly over the last years. Due to their low resources, sensors come along with new issues regarding network security and energy consumption. Focusing on the network availability, previous studies proposed to protect the network against denial of service attacks with the use of traffic monitoring agents on some nodes. But if the control nodes go down or get compromised, they leave the network unprotected. To better fight against attacks, we try to enhance this solution by introducing an energy-aware and secure method to select these monitoring nodes (called cNodes) in a clustered wireless sensor network. Our election process is done in accordance to their remaining reserves: nodes with the higher residual energy are selected. We discuss limitations of this deterministic process concerning security and cluster coverage, and suggest as a workaround to designate new control nodes (called vNodes). Those vNodes are responsible for monitoring the cNodes by periodically enquiring about their remaining energy and ensuring that they do not lie during the election process (in attempt to keep their cNode role). Finally, we present some experimental results obtained with the ns-3 simulator in order to analyze the impact of our proposal on the energy repartition in the network.

One challenge of composite Web service architectures is the guarantee of the Quality of Service (QoS). Performance evaluation of these architectures is essential but complex due to synchronizations inside the orchestration of services. We propose in this paper, to use stochastic automata networks which a power formalism to modelize and to evaluate complex system with synchronizations.

In this paper we present a formal modeling and verification method of an enhanced version of the CSMA/CA protocol related to the IEEE 802.11 MAC layer, which has been proposed as the standard protocol for wireless local area networks (LANs). We deal mainly with the DCF procedure of this protocol throughout a sequence of transformation steps. We first use UML state machines to capture the behavior of wireless stations implementing the DCF and we thereafter translate them into the input language of the UPPAAL model checker, that is a network of communicating timed automata. Last, we proceed with the checking of some safety and liveness properties by means of this tool, such as deadlock-freedom.

On a major security issue in WSN is the availability as these networks suffer from Denial of service Attacks. One of the most aggressive DoS attacks in WSN are greedy behaviors. This attack consists in increasing the bandwidth by a compromised node at the expenses of other nodes by not respecting the access network procedure. In this paper, we tackle the greedy behavior detection in the context of WSN using non slotted 802.15.4. Detecting of such attacks is not evident as it requires assessment tools that decide of a potential attack among normal network behaviors. Formal methods can be very useful to model and simulate the Network and therefore to provide a feedback of its behavior. We propose in this study to use Time Petri nets to detect greedy attaks. For this effect, we characterize the behavior of a greedy node, then we propose a modeling based on Time Petri nets for both a sane and a greedy node. Then we simulate the model under TINA platform by considering different scenarios and confront the obtained values of some parameters (as collision rate, the number of failings, and the energy consumption). Numerical results are used to detect misbehavior directly by nodes only by overhearing the transmissions.

Clustering algorithms play an important role in design and deployment of in wireless sensor networks (WSNs). We apply here a general clustering algorithm namely FFUCA (Fast and Flexible Unsupervised Clustering Algorithm) on WSNs. This application shows that FFUCA provides rapidly a strong organizational structure of nodes. We compare its built structures with those of the common algorithm LEACH to validate our approach. We aim to provide an optimal structure regarding energy consumption but with a low computational complexity.

The ever-increasing number of customers and the need for higher data rates and multimedia services require the deployment of Small Cell Networks. In this paper, we propose a new computational approach to study performance and reliability of Small Cell Networks, taking into account the retrial phenomenon, the finite number of customers (mobiles) served in a cell and the random breakdowns of the base station channels, using the Generalized Stochastic Petri Nets (GSPNs) model as a support. However, one of the major drawbacks of this high-level formalism in performance evaluation of large networks is the state space explosion problem which increases when considering repeated calls and multiple unreliable channels. Hence, the novelty of this investigation is the presentation of an approach which allows a direct computing of the infinitesimal generator describing the customers behavior and channels allocation in as small cell, without generating nor storing the reachability set. In addition, we develop the formulas of the main stationary reliability and performance indices as a function of the network parameters, the stationary probabilities and independently of the reachability set markings.

Used in areas such as pollution measurement or data gathering over battlefields, wireless sensor networks have attracted more and more attention over the last years. The deployment of such a network is accompanied by several security issues, including data confidentiality. Robust encryption algorithms addressed to network communication exist, but they do not always match the low resources restrictions — low processor, memory, limited energy — set upon the sensors. To overcome this, other, simpler solutions have been proposed, such as the Securing Data based on Multi-Path routing method, or an application of the Shamir's Secret Sharing Scheme, which both use distinct paths in the network to send pieces of data obtained by splitting the original message. This paper addresses the two methods named above, and proposes a solution based on traffic classification, using alternatively the Securing Data based on Multi-Path routing method, the Shamir's Secret Sharing Scheme, and strong encryption algorithms.

The modern distributed systems introduce new constraints. Therefore, there are subject to different types of faults. A running application should proceed normally and especially end to achieve its goals despite the presence of faults. Hence, the fault tolerance is very important in this context. Among the fault tolerance techniques, we consider in this study, the checkpointing based recovery by proposing a new hybrid checkpointing protocol for MANETs.

Vehicular ad hoc network (VANET) is currently researched and achieved by several organizers to develop the intelligent transportation system (ITS). Research on Vehicular Ad hoc Network (VANET) has been conducting for long time. Nowadays, several organizers has obtained remarkable achievements contributing to the development of the Intelligent transportation system, ITS. The communication protocol in VANET named 802.11p protocol, has been improved to adapt to the high-speed environment. However, the communication among vehicles can be interfered even by Denial of Service (DoS) attacks such as jamming attacks. The vehicles communicate with each other in the high-speed environment. The time of data exchange between them must be extremely short. Solutions for detection of jamming attacks must occur quickly to detect more precisely. In order to detect jamming attacks more precisely, solutions therefore must occur very fast. In this paper, we propose one solution to detect jamming attacks. The following solution is based on the combination of the packet delivery ratio and its diminution.

WIth the facility of deployment, Wireless Sensor Networks becomes very popular but have special characteristics such as limited battery, limited processing power, and limited storage that makes the energy consumption saving a real challenge. Add to this and due to their distributed deployment, these networks are exposed to denial of service attacks such as jamming and greedy attacks. In all cases these attacks tackle the energy consumption in order to degrade the overall Quality of Service (QoS). In this paper, we propose an energy-preserving solution to detect compromised nodes in WSNs. The proposed method is based on hierarchical clustering technique which elect Controlled nodes (Cnode) that analyze the traffic inside a cluster and to send warnings to the cluster-head (CH) whenever an abnormal behavior is detected. The proposed method is dynamic as the Cnodes are periodically elected among ordinary nodes on each atomic cluster. Such a solution results in a better energy balance while maintaining good detection coverage as it is based on the distance between nodes, the output throughput and delay between packets transmission.

SUMMARY Classical call admission control schemes focus on QoS enhancements because radio bandwidth will be allocated for mobile communications. Both of radio bandwidth and lifetime duration of mobile node are very important and precious for resources allocation in wireless networks. In this paper, we present a novel admission control for infrastructure‐less clustered wireless networks. The proposed admission control is based on QoS constraints and the lifetime duration of mobile nodes, including speed and power consumption parameters. Some new schemes are introduced, QoS parameters are negotiated during the admission procedure, and a forced handover technique is developed instead of reject flows, using a centralized view of topology. The performance of the proposed scheme was analyzed and evaluated with respect to throughput and call blocking probability, using different classes of traffic. Furthermore, simulation results confirmed the effectiveness of the admission control schemes. Copyright © 2011 John Wiley & Sons, Ltd.

ABSTRACT Detecting denial‐of‐service (DoS) attacks and reducing the energy consumption are two important and frequent requirements in wireless sensor networks (WSNs). In this paper, we propose an energy‐preserving solution to detect compromised nodes in hierarchically clustered WSNs. DoS detection is based on using dedicated inspector nodes (cNodes) whose role is to analyze the traffic inside a cluster and to send warnings to the cluster head whenever an abnormal behavior (i.e., high packets throughput) is detected. With previously introduced DoS detection schema, cNodes are statically displaced in strategic positions within the network topology. This guarantees good detection coverage but leads to quickly draining cNodes battery. In this paper, we propose a dynamic cNodes displacement schema according to which cNodes are periodically elected among ordinary nodes of each atomic cluster. Such a solution results in a better energy balance while maintaining good detection coverage. We analyze the tradeoffs between static and dynamic solutions by means of two complementary approaches: through simulation with the NS‐2 simulation platform and by means of statistical model checking with the Hybrid Automata Stochastic Logic. Copyright © 2013 John Wiley & Sons, Ltd.

A Wireless sensor Networks is a collection of simple devices with limited computation and resources. It is used to collect informations that are send back to the user. The sensed informations are real-time data streams for applications such as environmental monitoring, structural engineering, health care, VANET, and aircraft etc. The features of Wireless sensor networks (WSN) is that nodes are randomly deployed in the area where information collection is needed. Thus the security problem is an important issue as they are exposed to attacks and specifically to Denial of Service that can affect the sensor nodes battery lifetime. In this study, we propose and evaluate the performance of a secure routing protocol that take into account the existence of multipath between sender and destination to transmit data in several paths. The proposed protocol have been evaluated using stochastic automata networks formalism.

In this paper, we propose a novel dynamic approach for detecting Denial of Service (DoS) attacks in cluster-based sensor networks. Our method is based on the election of controller nodes called cNodes which observe and report DoS attack activities. Each cluster contains cNodes and normal sensor nodes. The role of a cNode is to analyze traffic and to send back a warning to the cluster head if any abnormal traffic is detected. The election of these cNodes is dynamic, and done periodically and based on a Multiplicative Linear-Congruential Generator (MLCG). The proposed dynamic solution can improve the network lifetime by minimizing the energy consumption for each sensor node and can improve security by preventing attacks.

Clustering algorithms have been widely used in many domains so as to partition a set of elements into several subsets, each subset (or “cluster”) grouping elements which share some similarities. These algorithms are particularly useful in wireless sensor networks (WSNs), where they allow data aggregation and energy cuts. By forming clusters and electing cluster heads responsible for forwarding their packets, the small devices that compose WSNs have not to reach directly the base station (BS) of the network. They spare energy and they can lead further in time their measuring task, so as to detect forest fires or water pollution for example. In this paper, we will apply a new and general clustering algorithm, based on classificability and ultrametric properties, to a WSN. Our goal is to get clusters with a low computational complexity, but with an optimal structure regarding energy consumption.

In this paper we have implemented the Hash technique to provide security in HWMP (Hybrid Wireless Mesh Protocol). Then after, we compared the Hash based HWMP against IBC (Identity Based Cryptography) based HWMP. This study has been carried out to show the great benefits of the IBC technique in securing HWMP. Results have shown that, IBC-HWMP outperforms the hash-based HWMP in terms of overhead and delay. According to the obtained results the use of IBC with HWMP provides a greate level of security with light overhead.

Recently, the directional antenna has received intensive research due to its variety of potential benefits for wireless communication systems, especially in the context of ad hoc networks. Nodes equipped with this type of antennas can communicate simultaneously without interference, and potentially establish links between them with less routing hops. This interference reduction provide a higher channel reuse leading to better resource exploitation and potentially better performance. In this study we want to take the advantage of directional antennas by proposing a sectorial coverage in a deployment of a WMN backbone based on mesh mode. Mainly, we propose a new architecture based on this type of antennas and OLSR protocol is used as routing protocol. We show by simulations under NS3 that the proposed architecture improve the overall QoS. We propose also an implementation of this type of antennas and we show with numerical results that the use of directional coverage outperform the omnidirectional coverage.

This paper tackle the problem of coverage in IEEE 802.11 in mesh mode. Instead of omnidirectional coverage, we propose to use directional coverage that can increase the distance between the nodes. The use of directional antenna have two main advantages. The first is to increase the performance of QoS of considered services. The second is that using directional antenna allows to improve the spatial reuse of the wireless channel, which allows nodes to communicate simultaneously without interference, and potentially establish links between nodes far away from each other, and the number of routing hops can be fewer than that of omnidirectional antennas. We also propose an new amendment to reduce the routing overhead related to the use of multiple interfaces. We have evaluated the performance of the proposed architecture and we show with numerical results that the use of directional coverage outperform the omnidirectional coverage.

In this paper we present an energy efficient priority based MAC protocol for Wireless Sensor Networks (WSNs). We abbreviate it as PRIMA. The PRIMA protocol consists of two phases; a clustering phase and a channel access phase. Clustering the senor network makes the MAC protocol to handle well network scalability issues. The channel access is composed of a hybrid mode of TDMA and CSMA. CSMA mode is used to communicate control messages, while data messages are assigned TDMA slots. Doing so, minimizes packet collisions and consequently minimizing energy consumption. Our PRIMA protocol forces the nodes that have no data to send to go early into a sleep state to save energy, this minimizes the idle listening periods which is considered as a main source of the energy consumption in sensor networks. The PRIMA protocol provides Quality of Service (QoS) by employing a queueing model to classify the traffic depending on its importance into four different queues. Higher priority queues have absolute preferential treatment over low priority queues. Through simulations and analytical analysis, we evaluate the performance of our proposed MAC protocol and compare it against the Q-MAC protocol. Results have shown that our protocol outperforms Q-MAC in terms of energy consumption, packet delivery ratio and average packet delay.

Reliable, fast and energy-efficient data dissemination is one of the essential features for several applications in wireless sensor networks (WSNs). In the dawn of WSNs, data delivery techniques considered only static data sinks. However, static sink approaches place a considerable burden on sensor nodes surrounding the sinks in terms of traffic and energy consumption. Eventually, data dissemination techniques for WSNs with mobile sinks have been proposed to alleviate the traffic issues of static sink approaches and improve network lifetime. In this paper, we propose a new data dissemination strategy that combines a simple but efficient sleep schedule technique with a trail generation mechanism. Simulation results show that the proposed E-TRAIL protocol significantly improves network lifetime while maintaining similar data delivery success performance when compared to the selected approaches.

In order to check formulas with rewards on multidimensional Continuous Time Markov Chains (CTMC) for composite Web service model, we propose an algorithm based on stochastic comparison. The considered model has heterogeneous servers and the number of elementary Web services can be very large. Thus, the computation of the rewards on the exact model is almost impossible because of the well known problem of the state space explosion. We propose to apply our proposed model checking algorithm on our proposed bounding models in order to perform the verification on the bounds values instead of the exact one. These bounding models provide upper and lower bounds on response times of composite Web service model.

In this paper, we propose methods to derive from original model, bounding models family for computation of lifetime in Wireless sensor networks. These models allow to find trade-off between accuracy of the bounds and the computation complexity.

Symmetric key algorithms are a typically efficient and fast cryptosystem, so it has significant applications in many realms. For a wireless ad hoc network with constraint computational resources, the cryptosystem based on symmetric key algorithms is extremely suitable for such an agile and dynamic environment, along with other security strategies. In this paper, we introduce the concept of selective encryption into the design of data protection mechanisms. First, we present the principle of selective encryption and propose a probabilistically selective encryption algorithm based on symmetric key. By utilizing probabilistic methodology and stochastic algorithm, a sender includes proper uncertainty in the process of message encryption, so that only entrusted receiver can decrypt the ciphertext and other unauthorized nodes have no knowledge of the transmitted messages on the whole. In addition, we also employ other security mechanisms to enhance the security of our proposed scheme. Eventually, we carry out an extensive set of simulation experiments based on ns2 simulator, and our simulation indicates that the technique of selective algorithms can indeed improve the efficiency of message encryption.

(This work is an extension of our conference paper at Valuetools 2006 [18].) Stochastic Well-formed Petri Nets (SWNs) are a powerful tool for modeling complex systems with concurrency, synchronization, and cooperation. Call Admission Control (CAC) is an important mechanism for mobile networks. While several studies have been done on GSM/GPRS and on UMTS system with mixed voice and data, to the best of our knowledge, limited CAC models for mobile networks that have been proposed in the literature are represented with a unidimensional Markov chain, where the communication system was mainly based upon voice calls in order to reduce the state space of the Markov chain. Another drawback of those studies is the lack of a clear synchronization between mobile nodes and the servers. In this paper, we propose an efficient CAC scheme for mobile networks that takes into account voice connections as well as synchronous and asynchronous data connections. Furthermore, we use SWNs to model the system interaction, which consists of several mobile nodes, gateways, cells, and servers. We describe our scheme and present its analytical performance results using the WNSIM symbolic simulator of GreatSPN tool.

WIMAX networks are aim to provide services with high throughput (up to 70 Mbps) and with a large coverage (up to 50 Km) To ensure QoS architecture has been designed and in the IEEE 802.16.e amendment they introduce the service differentiation by 4 service classes (UGS, rtPS, nrtPS and BE). Add to this an Admission control (AC) has been specified to avoid any degradation of the active connection. This mechanism is not defined in the literature and is let to the operators. Major implemented AC use the strict priority. The drawback of the strict priority is that it penalizes service classes with the lowest priority especially the BE. In this paper we propose to improve the AC of BE in WIMAX networks. To achieve this goal we propose to use the leaky bucket for both rtPS an nrtPS in order to reduce lightly the number of accepted connections and to improve considerably the number of BE accepted connection. We evaluate the performance of the proposed scheme by a markovian model.

Wireless mesh network (WMNs) are an emerging technology, presented mainly as a way to build a multi-hop network based on an infrastructure. IEEE has developed a draft 802.11s describing the enhancement of the IEEE 802.11 for mesh networks. This new standard aims to create a new wireless configuration that manages the topology, the quality of radio link and the routing. For routing, two path selection protocols HWMP (Hybrid Wireless Mesh Protocol) and RA-OLSR (Radio-Aware Optimized Link State Routing) are considered. The both routing protocols are inadequate for multimedia applications, such as video conferencing, which is often requiring guaranteed Quality of Service (QoS). QoS routing requires not only finding a best route from a source to a destination according to some criteria (like AirTime metric, hop numbers, etc.) , which is the case of HWMP, but a route that satisfies the end-to-end QoS requirement, often given in terms of bandwidth or delay. This paper tackles this last point by improving the HWMP protocol that handles QoS for real time applications. The goal of the proposed enhancement is to increase the bandwidth utilization and to avoid any network congestions. The method is based on the evaluation of QoS parameters as end-to-end delay or remaining bandwidth and to determine if they can fit with the real time application. Simulation results show that the proposed solution outperform classical HWMP.

Response time is an important factor for every software system and it becomes more salient when it is associated with introducing novel technologies, such as Web services. Most performance evaluation of Web services are focused toward composite Web services and their response time. One important limitation of existing work is in the fact that only constant or service exponential time distribution are considered. However, experimental results have shown that the Web services response times is typically heavy-tailed, in particulary, if there are heterogeneous. So, heavy-tailed response times should be considered in the dimensioning Web services. In this study, we propose analytical formulas for mean response times for structured BPEL constructors such as sequence, flow and switch constructors, etc. The difference with previous studies in the literature, is that we consider heterogenous servers, the number of invoked elementary Web services can be variable and the elementary Web services response times are heavy-tailed.

In this paper, we propose bounding models which provide upper and lower bounds on response time in composite Web service model. The considered models have heterogeneous servers and the number of elementary Web services can be very large. These models allows to find trade-off between the accuracy of the bounds and the computation complexity.

The most widely used standard for wireless networks is the IEEE 802.11. In 802.11, dense deployment of Access Points (APs) is needed to meet customers' demands. The installation of multiple access points is expensive and not convenient because of Ethernet wiring from access points to backhaul network access modem, hub, etc. Wireless mesh network (WMN) is an emerging technology; presented mainly as the solution to the problem related to the necessity to create a wireless distribution system (APs need to interconnect wirelessly). It is expected to replace the wireline infrastructure network due to the scalability and rapid cost effective deployment and maintenance. One of the WMN applications is that they can be used as a backbone. The characteristics of self-organization and auto-configuration in the wireless mesh backbone offer many benefits such as low upfront investment, increased reliability and scalability. In this Paper, we are interested, to the using of directional antennas in wireless mesh backbone. By using this kind of antenna in wireless mesh backbone we can improve the performance and QoS. The directional antenna allow to improve the spatial reuse of the wireless channel, which allows nodes to communicate simultaneously without interference, and potentially establish links between nodes far away from each other, and the number of routing hops can be fewer than that of omnidirectional antennas. We also propose a new amendment to reduce the routing overhead related to the use of multiple interfaces.

In wireless and mobile networks, the importance of network management becomes prominent, due to the prevalence of personal computing devices. These devices are able to offer their users with great convenience and flexible mobility. However, when the size of such a network is scalable, the difficulty of secure network management increases accordingly. In this paper, we primarily study the issues of secure network management. First of all, the necessity of managing a network in a securely way is discussed, along with the features of wireless devices and mobile networks. Then, we propose a secure framework for network management and group communication. In the proposed framework, a set of secure management mechanisms are involved to ensure the functions of group management and to protect the reliability of data exchange. The analysis of security mechanisms provides the provable secure properties of our framework, which is resilient to malicious behavior and able to guarantee the security of a network. Therefore, our proposed framework demonstrates a reliable paradigm for secure management and communication in wireless ad hoc networks.

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Abstract We propose new techniques to simplify the computation of the end‐to‐end delay for an evaluation of a Web services model. The simplification processes are associated with stochastic comparisons of random variables. Thus, the simplified models are stochastic bounds for the original ones. In this study, we consider that the Web service model can be represented by an acyclic directed graph. Thus, we propose upper and lower bounds on the response times by considering in one case special random variables for service times and in the other case we substitute the precedence graph by another one. We prove that the response times computed on the bounding models are really upper and lower bounds on the considered models. We also propose to generalize the model by considering the contention time when several executions of composite Web services are invocated. We propose in this case upper and lower bounds on response times by proposing bounding models. The response times are easier to compute on these new models. We give the corresponding proofs based on stochastic comparisons. We present several numerical results in order to show the accuracy of our bounds. Copyright © 2010 John Wiley & Sons, Ltd.

This special issue is devoted to performance evaluation of communications in distributed systems and Web-based service architectures. Performance evaluation is still a topic that attains a lot of attention in both distributed and mobile systems as well as Web-based service architectures. Owing to the recent advances in internet-based applications as well as distributed and mobile communication systems, we are witnessing a variety of new technologies. However, these systems are becoming very large and complex at the same time. Several challenges remain to be resolved before these systems become a commodity. Guaranteeing Quality of Service (QoS) and provisioning of web-based systems as well as distributed and mobile systems and evaluating their communication performance are among the challenging problems in the design of these systems. Quantitative analysis can be very difficult and may be intractable because of the state space explosion. New methods and tools have recently emerged for these kinds of complex systems, such as Stochastic Automata Networks, Stochastic bounds, PEPA, to mention just a few.

Due to their nature, vehicular ad hoc network (VANET) is vulnerable to denial of service (DoS) attacks, such as jamming attack. The objective of a jammer is to interfere with legitimate wireless communications, and to degrade the overall QoS of the network. In this paper, we propose a model to detect a particular class of jamming attack, in which the jammer transmits only when valid radio activity is signaled from its radio hardware. This detection model is based upon the measurement of error distribution.

In this paper we evaluate the handoff performance of an UMTS network with underlying tunnel-WLANs at the cell periphery while developing an adaptive QoS oriented CAC function, proposed to limit the occurrence of hard IEEE 802.11 WLAN-UMTS handovers to mobiles using real time applications. The proposed protocol is hybrid and based on the service class differentiation, the location in the heterogeneous infrastructure and a vertical handoff decision function as well. The results show that our policy achieves significant performance and gains. It maximizes the utilization of the resources available at the WLAN cells, and meets as much as possible the QoS requirement of higher priority users.

The emergence and success of IP networks make the development of new services like voice, multimedia or web services possible. One of the major problem of these type of application is that IP networks is not designed to provide Quality of Service (QoS) in an end to end architecture. Thus the performance evaluation of these applications is important to guarantee a high level of QoS. We focus in this study to evaluate the performance evaluation of Web services which is the most difficult to achieve because of the complexity of their architectures. The classical mathematical formalisms such as queueing networks can not be used in this kind of problems due the synchronization events and the state space explosion. In this paper we propose to use an adequate and efficient modelling tool: the Stochastic Automata Network (SAN) to evaluate the performance of Web services architecture over IP networks. Numerical results using PEPS are given for considered performance measures.

Admission control plays an important role in providing the desired Quality of Service (QoS) in wireless networks. It depends on precise estimates of bandwidth available in the network and the bandwidth required by new flows. Estimating these parameters in wireless networks is challenging due to the shared and open nature of the wireless channel. Resources sharing in wireless links imposes a number of problems in a QoS enabled networks. One of the problems is the estimation of the performance of implied radio links. In this article, we present a novel admission control for infrastrure-less clustered wireless networks. The proposed admission control is based on QoS constraints and the lifetime duration of mobile nodes, including speed, power consumption and capacity parameters. Some new schemes are introduced, QoS parameters are negotiated during the admission procedure, and a forced handover technique is developed instead of reject flows using a centralized view of topology. We also propose algorithms that implement these approaches. The simulation results confirm the effectiveness of the admission control schemes.

We propose new techniques to simplify the computation of the end to end delay for an evaluation of a Web services. These techniques allow us to simplify the model description to reduce the number of states of the underlying Markov chain. The simplification processes are associated with stochastic comparisons of random variables. Thus the simplified models are stochastic bounds for the original ones.

Web services are very present in computing today. Several studies are being conducted in the context of Web services: specifications, security, performance measures and so on. In this paper, we propose an analytical model based on multiple-class queueing network to evaluate the performance of Web service architecture. Numerical results are given for considered performance measures.

We have the privilege and the honour to welcome you all to the 5thIEEE IEEE International Workshop on Performance and Management of Wireless and Wired “on”Mobile Networks in Zurich, jointly with the LCN conference. Over the years, P2MNet has consolidated to become a major event in the performance evaluation of heterogeneous wireless and wired networks. Thus, let us first offer our special thanks the whole LCN Organizing and Steering Committee, for their hard work to make P2MNet such a successful event and for giving us the opportunity to organize the 5thedition of the workshop.

The increasing popularity of mobile wireless networks and various numbers of wireless networks becomes an important challenge. The future generation of wireless networks is expected to integrate a potentially large number of heterogeneous wireless technologies in what could considered a huge step toward universal seamless access. The topology management became here one of the main challenges. Efficient topology control enhances quality of service and provide less congested cell. In this paper we propose a model to control the topology of a infrastructure-less heterogeneous wireless networks (Ad Hoc and WiMAX relay networks), this approach is based on periodic measurements and forced vertical handover techniques with a control layout. Moreover, this proposed model uses a dedicated architecture with different planes (access, communication and control). We have proposed an analytical model and simulation has been used in order to provide performances rewards.

Modelling becomes more and more important in computer science. Recent systems which are in general composed of several resources of different nature involved in sharing tasks sent by users need high level models to be studied. In theses complex systems with several interactions, load balancing between the servers which process the requests is necessary if performance is required. Many works have been done on load balancing, however none of theses studies uses the stochastic well formed Petri nets (SWN) which offer a high level modelling. In this work, we are interested in the adaptation of an algorithm of load balancing with SWN in a distributed database. Our study takes into account the synchronization, the identity of the resources and their cooperation. So as to point out the impact of the load balancing on performance, we propose two models: a model with load balancing, another one without load balancing. Performance measures are carried out using symbolic simulation.

It is well known that TCP protocol behaves quiet loosely in mobile wireless environments. In fact, when a mobile host moves from one IP domain to another it has to get a new IP address in the new domain. This process of getting a new IP address should be automatic and fast enough in order to keep active any running TCP session without loosing the quality of service provided to the user. Mobile IP has been developed to manage the user mobility in mobile wireless networks. However, this protocol is not well suited to support a TCP handoffs during the node's handover process which will help in keeping active any running TCP sessions. In this paper, we have designed a new management architecture which will ensure the continuity of any TCP connection when a mobile host executes a handover. In order to validate our architecture, we have evaluated its performance by adopting an analytical model.

In this paper we propose an efficient multi-service scheduling scheme called real-time adaptive scheduler (RTAS) for WiMAX service classes. It is based on deficit round robin with an adaptive quantum according to the QoS requirement of each considered service. Our scheduler assures fairness between the different class of services on either uplink or downlink TDD frame. Simulation results show the achieved fairness and the adaptation with real-time characteristics of data traffic.

IEEE 802.16 standard provides a broadband wireless access solution. WiMAX (Worldwide interpretability for microwave access) is the business definition of the 802.16-2004 amendment. In WiMAX, quality of service (QoS) is provided through both classification and scheduling of the four different types of traffic classes defined by the standard. Each class has it own bandwidth requirements as well as its level of QoS, which has to be maintained. In this paper, we provide a performance analysis of three types of connections defined in the standard (UGS, rtPS, nrtPS). Different levels of priority and blocking probability are assigned to each class of service. This performance analysis has been done using an analytical model for evaluating admission control (AC) for the previous mentioned classes in WiMAX network.

WiMAX (worldwide interpretability for microwave access) is one of the leader standards of broadband wireless access (BWA). This standard becomes a competitor of 4G or LTE (long term evolution) with the introduction of different class of service flow (UGS, rtPS, nrtPS, BE). Each service class has its own QoS requirements. Even if the standard specify the transmission policy of each service class, it recommends the implementation of an admission control (AC) without any specification. As the standard does not define any specifications for the AC, then this task is left for the operator. In this paper, we propose an implementation of an AC algorithm mechanism for IEEE 802.16. The performance evaluation of these networks by analytical models is not easy due to the state space explosion, thus we use the stochastic automata networks (SAN) formalism to model our proposed AC mechanism. With SAN we calculate the rewards of the proposed AC and we show that the proposed solution is efficient.

We use a mathematical method based on stochastic comparison of multidimensional Markov chains in order to compute packet loss rates in IP routers for MPLS networks. The key idea of this methodology is that given a complex system represented by a Markov chain which is too large to be solved, we propose to build smaller Markov chains providing performance measures bounds.

Service oriented computing (SOC) strives for applications having services as the fundamental element of design, and with Web services acting as the enabling technology. In an earlier work, we have empowered Web services with the concepts from aspect oriented programming (AOP) to enhance their flexibility and adaptability. Software flexibility and its execution time to provide expected services are the fundamental requirements for our industrial context. Therefore, this paper presents a formal model for simulating and studying response time of aspectized Web services. By classifying these aspectized Web services according to their non-functional requirements, we intend to study the execution behavior for various classes of these services.

End to end QoS of communication systems is essential for users but their performance evaluation is a complex issue. The abstraction of such systems are usually given by multidimensional Markov processes whose analysis is very difficult and even intractable, if there is no specific solution form. In this study, we propose an algorithm in order to automatically derive aggregated Markov processes providing upper and lower bounds on performance measures. We applied the algorithm to the analysis of an open tandem queueing network with rejection in order to derive performance measure bounds. Parametric aggregation schemes have been proposed in order to compute bounds on loss probabilities and end to end mean delays. Therefore a tradeoff between the accuracy of the bound and the size of considered Markov chains is possible.

TCP is a protocol which performs well with networks that are physically linked and hosts are stationary. To establish a TCP connection, one must associate an IP address with a port number for both sender and receiver. However, in wireless environments mobile hosts are subject to change their attachment point during communication, this process is called handoff. Thus, in mobile environments the TCP operation is more complicated, because the mobile moves from one cell to another and it changes of network’s domain, then it acquires a new temporary IP address. Hence, the TCP packet loss is increased. Mobile IP was developed to manage the user mobility in wireless networks. However, this protocol is not adapted to support TCP session throughout the handover process. In this study, we have modeled the proposed architecture which ensures the continuity of TCP connection when a mobile executes a handover. We have evaluated the performance of the architecture by an analytical model.

International audience

Summary form only given. Due to random access in wireless networks using CSMA/CA like in Wifi networks, the integration of services with a lot of quality of service needs is impossible. In this paper, we propose to study and to evaluate a new MAC protocol that takes into account different types of traffic (e.g.. voice and data) and for each traffic, different priority levels are considered. To improve the QoS of WIFI MAC protocols, we add a selective reject and push-out mechanisms. To model our protocol, using Markov chain is impossible because it provides Markov chain with a large state-space. This is due to the resource management and user mobility. Thus, we propose to build an aggregated Markov chain with a less state-space that allows to compute easily performance measures. We have used stochastic comparisons of Markov chains to prove that the considered access protocol (with selective reject and push-out mechanisms) gives less loss rates of high priority connections (data and voices) than the traditional one (without selective reject and push-out mechanisms). We give numerical results to confirm mathematical proofs.

We present in this paper a mathematical method based on stochastic comparisons of Markov chains in order to compute in a mobile network performance measures that are important Q parameters for users: the dropping handover of voice and the blocking probability of a new voice call. The key idea of this methodology is that given a complex system represented by a multi-dimensional Markov chain which is too large to be solved, we propose to reduce the state space, and so to define a new Markov chain which is a simplified version of the original one. This reduced Markov chain is defined as an aggregated one, which represents a stochastic bound for performance measures written as increasing reward function on the stationary distribution. The main steps of the construction of the aggregated Markov chain applied into mobile networks are presented in this paper. As the number of mobile users with different kinds of applications increases, the associated model is more complex and it can be represented by multi-dimensional continuous time Markov chain with a very large size. Thus, we define an aggregated Markov chain represented by a multi-dimensional birth and death process which is very easy to solve. We have proved that there is a weak ordering between the original Markov chain and the aggregated one using increasing set formalism. We have computed upper bounds of dropping handover and blocking probability for different values of input parameters. Numerical results prove that upper bounds give good results and so the stochastic methodology is an interesting mathematical tool for the performance evaluation of complex systems. Keywords: Mobile Networks, Quality of Service, Stochastic ordering, stochastic comparisons, Continuous Time Markov Chains.

New services are introduced in the broadband network such video or multimedia. These services have some quality of service constraint such as transit delay, and cell loss probability. To improve the quality of service, it is important to optimize the bandwidth utilization. In this study we focus on this problem, and our major contribution is to provide quality of service by the development of a new rerouting algorithm. All existing routing algorithms optimize at the time of call establishment. The originality of our contribution is to optimize routing before and after call establishment. To show the benefit of our algorithm we do a performance evaluation using a new technique called SAN (stochastic automata networks), which is adapted to our problem.