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Performance Analysis of Telecommunications and Local Area Networks
... Une première recherche nous conduit à constater l'existence d'ouvrages offrant des recommandations pour l'évaluation de performances d'architectures réseaux [51,120,161]. De nombreux travaux de recherche les plus divers proposent différentes méthodologies pour la détermination des délais dans le contexte d'architectures Ethernet commuté (nous y reviendrons particulièrement aux chapitres 4 et 5). Face à cet éventail de solutions, se pose le problème du choix de l'une d'entre elles. ...
... 26 Trois ouvrages couvrant notre problématique furent cités au cours de la section 3.1.1. L'approche de Chan [51] relève de la modélisation mathématique par l'application de la théorie des files d'attente (nous y reviendrons plus loin). Les réseaux locaux et téléphoniques sont abordés par l'auteur, modélisant, sous la forme de processus stochastiques, les dynamiques d'arrivée et le taux de service des trames. ...
... La pratique de la modélisation analytique pour l'étude d'architectures réseaux est aujourd'hui courante en dépit de son ancienneté. Le nombre de méthodes existantes se réclamant de cette approche étant considérable, nous n'en présentons, à titre d'exemples, que deux : la théorie des files d'attente, déjà mentionnées par Chan [51] et Park [161] et très connue pour la modélisation analytique d'architectures réseaux ; ainsi que la théorie de l'ordonnancement, dont nous reparlons plus en détail au chapitre 5. ...
Ce travail de thèse s'intéresse à l'évaluation de performances des systèmes industriels de type smart grids, dont le rôle est d'assurer la transmission d'électricité depuis la/les source(s) de production jusqu'aux consommateurs. Considérés comme des systèmes distribués à forte criticité, il en résulte une obligation de respect de contraintes temps réel. Le standard IEC 61850, déployé pour l'automatisation et la protection des postes électriques composant ces smart grids, propose une quantification de ces contraintes sous forme de latences minimales à ne pas excéder. L'IEC 61850 ne préconisant aucune approche spécifique pour garantir ces contraintes temporelles, des solutions doivent alors être trouvées pour y répondre. Dans le cadre de cette thèse, nous proposons en premier lieu un nouvel outil d'aide à la décision fournissant des résultats obtenus par simulation, basés sur le logiciel OMNeT++. Ces modèles intègrent à la fois des outils pour Ethernet classique, la norme Time Sensitive Networking (TSN) et l'IEC 61850. Une seconde contribution est la modélisation analytique des délais de pire cas, basée sur l'agrégation de flux. Cette nouvelle approche permet de simplifier l'analyse du délai pire de cas par une succession d'analyses locales reposant sur des opérations peu coûteuses en temps de calcul, tout en minimisant le pessimisme des bornes de délais. Cette analyse prend en considération des architectures reposant sur Ethernet classique et TSN. Enfin, nous étudions l'apport possible, à notre problématique, de la Multi-Modélisation et de la co-simulation, reconnue comme solution pour l'étude de systèmes complexes (dont les smart grids). Nous contribuons ainsi à l'amélioration des capacités de l'intergiciel de co-simulation MECSYCO, en permettant à ce dernier la possibilité de co-simuler des systèmes smart grids intégrant trois expertises métiers : électrique, contrôle-commande et communication numérique.
... A commonly used approach to solve the linear equations (5) and (6) is via LU Decomposition [38], which has a complexity O(|P| 3 ) (|P| refers to the size of P). If the spare property of the matrix Λ is considered, then the complexity can be further reduced to O(|P|) using the approaches in [12,26]. For each s j (1 < j ≤ j * ), the size of P is (K + 1)((j − 1)K + 1). ...
... According to Equations (10), (12), and (13), we have ...
Cloud gaming has gained significant popularity recently due to many important benefits such as removal of device constraints, instant-on, and cross-platform. The properties of intensive resource demands and dynamic workloads make cloud gaming appropriate to be supported by an elastic cloud platform. Facing a large user population, a fundamental problem is how to provide satisfactory cloud gaming service at modest cost. We observe that the software storage cost could be substantial compared to the server running cost in cloud gaming using elastic cloud resources. Therefore, in this article, we address the server provisioning problem for cloud gaming to optimize both the server running cost and the software storage cost. We find that the distribution of game software among servers and the selection of server types both trigger tradeoffs between the software storage cost and the server running cost in cloud gaming. We formulate the problem with a stochastic model and employ queueing theory to conduct a solid theoretical analysis of the system behaviors under different request dispatching policies. We then propose several classes of algorithms to approximate the optimal solution. The proposed algorithms are evaluated by extensive experiments using real-world parameters. The results show that the proposed Ordered and Genetic algorithms are computationally efficient, nearly cost-optimal, and highly robust to dynamic changes.
... Throughput analysis of slotted non-persistent [12] For an approximate analysis of the slotted non-persistent CSMA, in addition to the assumptions for the non-persistent CSMA, we assume that the time axis is divided into slots of equal length τ p . A diagram for the slotted non-persistent CSMA is shown in figure 2-7. ...
... represents the absence of impulses and the channel is available for utilization. These two states can be represented by two random variables, which are geometrically distributed [11,12] . ...
... However, owing to the low cost nature of transceivers, there are reasons to believe that the BT technology could be also used for small or medium sized wireless local area networks (WLANs) where the higher bit rates are not needed [12]. The BT paradigm is based on the concept of piconets, where one device plays the role of Master and several terminals are Slaves; a Roll-call protocol can be used to manage the medium access aspects [13]; BT Specifications define a collection of protocol stacks based on, at the physical and radio link levels, an RF and a baseband layer. At baseband, six different packet types are defined, having different payload sizes and coding protection. ...
... The communication management adopted by BT is fully centralized: a communication This proposal is denoted as Roll-call polling [13] and was also studied in [15], under a different notation. This solution is fully compliant with BT Specifications and is the easiest and the most natural choice as far as the BT MAC protocol is concerned. ...
In this paper a MAC level Link Adaptation (LA) strategy to be implemented in a Bluetooth piconet is investigated: the performance level that can be achieved in terms of throughput is derived and the comparison with the case of no LA is performed.
Suitable definitions of the performance figures related to throughput are given and, starting from the knowledge of the physical level performance obtained via simulation, their analytical evaluation is performed in both the cases of LA and no LA.
All aspects related to the propagation characteristics of the environment, the modulation/demodulation and coding/decoding techniques, and the multiple access strategy are taken into account in an integrated way; moreover a reference scenario analytically characterized along with a realistic scenario have been considered for the performance level assessment.
The analytical results have been compared with simulation outcomes which confirm the validity of the approach adopted.
... The work will provide more reliable and efficient metering data collection to help the power-supply company realize real-time data collection and implement other value-added services based on the mutual communication between the DC and the meter units. These proposed schemes are based on the polling method, which is a centralized access method that uses a main station to control the multiple access to the shared medium [6] . It is more efficient to use a reservation medium-access control (MAC) protocol in a PLC network [7] , where there a centralized BS exists, a typically large number of subscribers, and where there is mutual communication between the central controller and each end station. ...
... If the BS cannot hear anything from the polled station after a stipulated time period, it will poll the next station anyway. Hence, the next network station in the same cycle can be polled [6]. ...
This paper proposes several schemes for solving the typical "silent node" problem in a powerline communications (PLC) access network based on the polling protocol. These schemes can help guarantee reliable and efficient automatic metering reading (AMR) service. The assumption of the PLC access network model in this paper is based on the actual structure of the PLC access networks of Singapore public residential buildings. Also, a two-state transition Markov model is utilized to model a meter unit with "silent node" problem in a PLC network. Some of the assumptions are also based on Konnex standard. By utilizing these models for our computer simulation, the performance of our proposed schemes can be evaluated in terms of reliability and efficiency.
... The work will provide more reliable and efficient metering data collection to help the power-supply company realize real-time data collection and implement other value-added services based on the mutual communication between the DC and the meter units. These proposed schemes are based on the polling method, which is a centralized access method that uses a main station to control the multiple access to the shared medium [6]. It is more efficient to use a reservation medium-access control (MAC) protocol in a PLC network [7], where there a centralized BS exists, a typically large number of subscribers, and where there is mutual communication between the central controller and each end station. ...
... If the BS cannot hear anything from the polled station after a stipulated time period, it will poll the next station anyway. Hence, the next network station in the same cycle can be polled [6]. ...
This paper presents two algorithms, namely clustered simple polling and neighbor relay polling, for solving the typical "silent node" problem in automatic meter reading (AMR) systems using power-line communications (PLC)-access networks. These schemes are tested through computer simulations to be both effective and efficient in overcoming the "silent node" problem in AMR systems. The construction of the PLC-access network model in this paper is based on the actual structure of the PLC-access networks of Singapore public residential buildings. Also, a two-state transition Markov model is used to simulate a meter unit with such a "silent node" problem in a PLC network. The processing time model is established on a meter topology of three-level clustering. By using these models for our computer simulations, the performance of our proposed schemes can be evaluated in terms of reliability and efficiency.
... Queueing systems have been analysed on account of their wide range of applications in computer systems, telecommunication systems, wireless networks, etc. An excellent overview of the fundamental methods and results on queuing theory is given in the monographs of [5,8,11,[14][15][16]23]. Wireless Sensor Network has many successful applications like automated factories, remote telemedicine, military area protection and so on. ...
A single server queue with Poisson arrival and exponential service times subject to a policy of single working vacation with customer impatience is considered. The service times are different for an active phase and a working vacation phase. The customer is allowed to leave the system during the working vacation phase. Catastrophes, when they occur, wipe out the system which results in the system being inactive for a random period of time. Explicit expressions for the transient probabilities of the close-down period, maintenance state, active state, working vacation state and system size for active phase and working vacation phase have been obtained. The corresponding steady-state analysis and performance measures are also obtained. The effects of various parameters on the system performance measures are studied using numerical examples.
... Over the years, the study of queueing systems has grown tremendously, primarily due to the fact that queueing systems have enormous applications in wireless networks, telecommunication networks etc. A comprehensive over view of the fundamental techniques and standard results in queueing theory are given in the monographs of [1], [2], [3], [4], [5], [6], and [7].Wireless communications is one of the fastest growing segments of the communication industry. The rapid growth of wireless systems in areas such as Wireless sensor networks, automated factories, remote telemedicine etc. promise a bright future for wireless networks. ...
Mathematical analysis of Queueing systems shows a significant part in wireless communication network such as channel control, energy saving schemes etc. Here, we consider a M/M/1 Queue with the server operating in three modes -Active mode,
maintenance mode , sleep mode/close down period (with transitions from the maintenance mode to the sleep mode/close down period and active mode), subject to catastrophes. Catastrophes occur only when there are customers in the system and they wipe out the entire system resulting in the system being rendered inactive for a random period of time. Explicit expressions have been obtained for the transient probabilities and steady state probabilities of the close down period, maintenance state and system size along with the many performance measures. Influence of the different parameters on the steady state probabilities, system performance measures are studied using numerical examples.
Keywords: Catastrophe, close down state, maintenance state, transient probabilities, steady state probabilities
... The relays are equipped with infinite capacity buffers (queues), and they assist the user by transmitting the packets that failed to reach the destination. Packets have equal length (i.e., they consist of the same fixed number of bits [14]), and time is divided into slots corresponding to the transmission time of a packet. We consider an early arrival system (EAS), under which, at the beginning of a slot, packets arrive and they are routed to the relays according to the join the shortest relay queue (JSRQ) policy. ...
The aim of this work concerns the performance analysis of systems with interacting queues under the join the shortest queue policy. The case of two interacting queues results in a two-dimensional random walk with bounded transitions to non-neighboring states, which in turn results in complicated boundary behavior. Although this system violates the conditions of the compensation approach due to the transitions to non-neighboring states, we show how to extend the framework of the approach and how to apply it to the system at hand. Moreover, as an additional level of theoretic validation, we have compared the results obtained with the compensation approach with those obtained using the power series algorithm and we have shown that the compensation approach outperforms the power series algorithm in terms of numerical efficiency. In addition to the fundamental contribution, the results obtained are also of practical value, since our analysis constitutes a first attempt toward gaining insight into the performance of such interacting queues under the join the shortest queue policy. To fully comprehend the benefits of such a protocol, we compare its performance to the Bernoulli routing scheme as well as to that of the single relay system. Extensive numerical results show interesting insights into the system’s performance.
... The study of Queueing system has generated a lot of interest fundamentally due to the fact that Queueing systems have a wide range of application in wireless networks, Telecommunication networks etc. A comprehensive over view of the fundamental techniques and classical results in queueing theory are given in the monographs by Bertsekas and gallager (1987), Takagi (1991), Daigle (1992), Gelenbe and Pujolle (1998), Chan (2000), Hayes and Ganesh Babu (2004), and Giambene (2005)Wireless communications is one of the fastest growing segments of the communication industry. WiMAX evolved to satisfy the need of having a wireless internet access and other broadband services which work well in those areas where it is difficult to establish wired infrastructure and economically not feasible. ...
A single server queue with Poisson arrival and exponential service times subject to maintenance of the server, close down period and catastrophes is considered, wherein catastrophes occur only when there are customers in the system and they wipe out the entire system resulting in the system being rendered inactive for a random period of time. Explicit expressions for the transient probabilities of the close down period, maintenance state and system size have been obtained. The corresponding steady state analysis and performance measures are also obtained. The effects of various parameters on the system performance measures are studied using numerical examples.
... The relays are equipped with infinite capacity buffers (queues), and they assist the user by transmitting the packets that failed to reach the destination. Packets have equal length (i.e., they consist of the same fixed number of bits [14]), and time is divided into slots corresponding to the transmission time of a packet. We consider an Early Arrival System (EAS), under which at the beginning of a slot packets arrive and they are routed to the relays according to the join the shortest relay queue (JSRQ) policy. ...
The scope of this work is twofold: On the one hand, strongly motivated by emerging engineering issues in multiple access communication systems, we investigate the performance of a slotted-time relay-assisted cooperative random access wireless network with collisions and with join the shortest queue relay-routing protocol. For this model, we investigate the stability condition, and apply different methods to derive the joint equilibrium distribution of the queue lengths. On the other hand, using the cooperative communication system as a vehicle for illustration, we investigate and compare three different approaches for this type of multi-dimensional stochastic processes, namely the compensation approach, the power series algorithm (PSA), and the probability generating function (PGF) approach. We present an extensive numerical comparison of the compensation approach and PSA, and discuss which method performs better in terms of accuracy and computation time. We also provide details on how to compute the PGF in terms of a solution of a Riemann-Hilbert boundary value problem.
... We will base our definition of a random process on that given by Chan [2000]. ...
... We will base our definition of a random process on that given by Chan [2000]. ...
... Each slot has a marking bit in its header, which indicates the status of the slot whether it is empty or full as shown in Fig. 2. slotted ring networks provide high throughput [6][7]. The empty slot principle is the control strategy of the slotted ring. ...
Assorted analytical methods have been proposed for evaluating the performance of a
slotted ring network. This paper proposes MGM (Matrix Geometric Method) to analyze
the station buffer of a slotted ring for DT (Discrete-Time) queueing. The slotted ring is
analyzed for infinite station buffer as a late arrival DT system. Utilizing the
characteristics of 2-D Markov chain, various performance measures are validated
with their corresponding results such as, throughput and MPAD (Mean Packet Access
Delay) as well as the packet rejection probability for finite station buffer. The presented
results prove efficacy of the method.
... All other packets will be processed without any QoS guarantees as best effort traffic therefore setting operation parameters for this class has no sense [7,8]. ...
This paper presents a mathematical description of Weighted Round Robin service strategy, on which basis all the perspective QoS tools that serve to manage congestion in converged packet networks work. On the basis of the presented mathematical model, it is possible to suitably configure the operational parameters (maximum queue length, distribution of the available transfer capacity) of these tools according to required values of packet delays. The implementation of the analytical model is demonstrated on a real network segment using advanced network data traffic emulator.
... Phase-type distribution is based on the method of stages technique [7], [8], [9]. Using a random variable, we can represent the probability distribution of phases to describe the time till the Markov process ends to one absorbing state [10], [11]. Phase type distribution can be used to model a system in discretetime queueing domain, which yields, probability distribution which results the occurrence of one or more inter-related geometric distribution in sequence or phases is known as discrete phase-type distribution [12], [13], [14]. ...
Evaluation of flow time and service process of a queuing systems is a very special and powerful concept to analyze the flow time of any arriving data packet at any point of the system. In this paper, we construct and demonstrate the flow process and service process transition diagram to determine the flow time of a data packet in an early arrival finite discrete-time queueing system where arriving data packets are hypogeometrically distributed. We compute the probabilities of all starting states where a data packet can possibly enters and its flow process begins. We validated the obtained analytical results, for probability mass function of each starting state and total probability mass function, with simulation results.
... Given λ, μ and K, P {U navailable} is calculated by Equation 2) Enterprise service metric: The metric is represented by the M/M/n queuing model [13]. Enterprise services are modelled as CTMCs where the state of the Markov chain is defined by the number of requests being processed. ...
Supervisory Control and Data Acquisition (SCADA) systems control and monitor industrial and critical infrastructure functions, such as the electricity, gas, water, waste, railway and traffic. Recently, SCADA systems have been targeted by an increasing number of attacks from the Internet due to its grow- ing connectivity to Enterprise networks. Traditional techniques and models of identifying attacks, and quantifying its impact cannot be directly applied to SCADA systems because of their limited resources and real-time operating characteristics. The paper introduces a novel framework for evaluating survivability of SCADA systems from a service-oriented perspective. The framework uses an analytical model to evaluate the status of services performance and the survivability of the overall system using queuing theory and Bayesian networks. We further discuss how to learn from historical or simulated data automatically for building the conditional probability tables and the Bayesian networks.
... The corresponding accessing delays of asynchronous and synchronous data on the basis of the proposed MAC are analyzed and formulated as below 1) Delay in Accessing of Asynchronous Data: On behalf of [17], the delay faced by an arbitrary asynchronous request of priority 'n' in being served is the sum of three factors w c = delay due to current ongoing transmission. w b = delay due to equal and higher priority requests that arrive before 'n'. ...
We introduce the deployment of IEEE 802.15.4a in industrial field level communication, which is unexplored so far. Impulse radio-time hopping ultra wide band (IRTH UWB) physical layer is robust against dense multipath fading and interferences. However, we propose an adaption in medium access control (MAC) to meet the major constraints of reliability and timeliness. The self configuring MAC overcomes the difficulties and limitations of specified carrier sense multiple access/collision avoidance (CSMA/CA), slotted Aloha and guaranteed time slots (GTS) mechanisms. Addressable TH codes in fixed time slots of modified superframe structure are used to handle asynchronous alarm requests during ongoing synchronous transmissions. Traffic modeling is presented and we derive the expressions for accessing delays of both the synchronous and asynchronous data traffics. The realistic industrial non line of sight (NLOS) channel environment of IEEE 802.15.4a is employed and the respective power delay profile (PDP) and cumulative density function (CDF) of instantaneous signal to noise ratio (SNR) are found. Moreover, for large number of resolvable multipath components (MPCs), we also propose a reduced complexity adaptive SRake receiver, which efficiently recovers the weak IR-TH UWB signals in dense multipath propagation and strong noise. In addition, we evaluate the error performance of the proposed receiver architecture in comparison with conventional SRake and additive white Gaussian noise (AWGN) correlation receivers. Our simulation results show a significant performance improvement with very less number of SRake fingers.
A single server queue with Poisson arrival and exponential service times subject to a policy of single working vacation, close down period and catastrophe is considered. The service times are different for the active phase and the working vacation phase. A catastrophe is assumed to occur when there are customers in the system and wipes out the entire system resulting in the system being inactive for a random period of time. Explicit expressions for the steady state probabilities of the close down period, maintenance state and system size for active phase and working vacation phase have been obtained. The effects of various parameters on the system performance measures are studied using numerical examples.
Advanced persistent threats (APT) are major threats in the field of system and network security. They are extremely stealthy and use advanced evasion techniques like packing and behaviour obfuscation to hide their malicious behaviour and evade the detection methods. Existing behavior-based detection technique fails to detect the APTs due to its high persistence mechanism and sophisticated code nature. Hence, a novel hybrid analysis technique using Behavior based Sandboxing approach is proposed. The proposed technique consists of four phases namely, Static, Dynamic, Memory and System state analysis. Initially, static analysis is performed on the sample which involves packer detection and signature verification. If the sample is found stealthy and remains undetected, then it is executed inside a sandbox environment to analyze its behavior. Further, memory analysis is performed to extract memory artefacts of the current system state. Finally, system state analysis is performed by correlating clean system state and infected system state to determine whether the system is compromised.
Networking is referred as connecting computers electronically for the purpose of sharing information. Resources such as files, applications, printers and software are common information shared in a networking. The advantage of networking can be seen clearly in terms of security, efficiency, manageability and cost effectiveness as it allows collaboration between users in a wide range. Basically, network consists of hardware component such as computer, hubs, switches, routers and other devices which form the network infrastructure. These are the devices that play an important role in data transfer from one place to another using different technology such as radio waves and wires. There are many types of network available in the networking industries and the most common network are Local Area Network (LAN) and Wide Area Network (WAN).LAN network is made up of two or more computers connected together in a short distance usually at home, office buildings or school. WAN is a network that covers wider area than LAN and usually covers cities, countries and the whole world. Several major LAN can be connect together to form a WAN. As several devices are connected to network, it is important to ensure data collision does not happened when this devices attempt to use data channel simultaneously. A set of rules called Carrier Sense Multiple Access / Collision detection are used to detect and prevent collision in networks.
IntroductionLittle's LawModel of the M/M/1 System with Single-Server and Infinite QueueModel of the M/M/1/N-1 System with Single-Server and Limited Queue SizeModel of the M/M/m System with m Servers and Infinite Queue SizeModel of the M/M/m/N System with Limited Queue Size and Limited Number of ServersModel of the M/G/1 System with Single-Server and Infinite Queue SizeM/D/1 SystemQueuing Systems with One Server and Nonpre-Emptive PrioritiesThe M/G/R PS Model – Model of Buffers in the UMTS SystemReferences
Operasional dan pelayanan kepada nasabah suatu bank dengan system online sangat tergantung kepada kinerja dari jaringan komunikasi data, baik komunikasi data antara kantor pusat dengan kantor cabang maupun pelayanan langsung kepada nasabah melalui terminal atau channel transaksi.Biaya suatu bank untuk mengoperasikan jaringan komunikasi data merupakan salah satu biaya operasional bank yang terbesar. Usaha melakukan efisiensi biaya dan optimasi pemakaian data rate jaringan system banking online harus dilakukan guna menurunkan biaya operasional sekaligus peningkatan kinerja jaringan. Untuk itu digunakan kerangka kerja terukur berdasarkan e-TOM (Enhanced Telecom Operation Map).Untuk mendapatkan nilai-nilai Key Performance Indicators (KPI) dilakukan pengukuran terhadap besarnya data rate yang diperlukan oleh banking system, jumlah seluruh paket data yang ditransmisikan, besarnya data yang mampu ditransmisikan, dan banyaknya data yang tak dikehendaki pada segmen jaringan.Berdasarkan Key Performance Indicators (KPI) tersebut dilakukan perubahan setting data rate dan pengaturan alokasi port data komunikasi pada segmen jaringan hingga didapatkan nilai KPI terbaik.
The cooperation of micro-electronics, wireless communications, integrated circuits and sensor networks have led to rise of Wireless Body Area Networks (WBANs). The aim of WBANs is to keep a human body under control by means of a set of small-size, lightweight, and low-power sensor nodes placed in, on, or around the human body. The WBANs are also used in a number of new applications namely health monitoring, entertainment, sports, and military applications. The sensor nodes in WBANs have limited energy resources as a result of communicating with each other wirelessly. Therefore, the medium access control protocols for WBANs must be energy efficient protocols. Also, WBAN’s importance of having the different data traffics has increased determination of operation sequence at the coordinator nodes. In this study, data traffic sensitive WBAN is proposed. End to end delay and throughput results are examined for performance evaluation.
This paper aims to improve the spectrum efficiency of the licensed time division multiple access (TDMA) channel by exploiting the unused periods of primary users (PUs) in cognitive radio networks. A wireless network that consists of two classes of users, PUs and CR users, accessing a time slotted based common communication channel is considered. PUs employ TDMA and have always high priority over the CR users to access the channel. CR users utilize slotted Carrier Sense Multiple Access and can access the channel when it is not occupied by the PUs. New expressions for the throughput of both CR network and overall network have been derived in order to evaluate the channel utilization. Besides, an example network have been developed, modeled and simulated by using the OPNET Modeler simulation software with the purpose of verifying the analytical throughput results. The simulation results obtained under various network load conditions are consistent with the analytical results. This study has also proposed that the overall channel utilization can be improved by well exploiting the spectrum holes without interfering with the PU transmissions.
With increasing probability of failure and reliability concerns for interconnection networks, fault-tolerance is quickly becoming an integral part of such systems. It is therefore critical to provide an efficient fault-tolerant mechanism to keep the system running, even in the presence of faults. In this paper a distributed fault-tolerant routing methodology for mesh networks is proposed which supports a dynamic fault model. Unlike most previous methods that support a dynamic fault model, the presented method is able to tolerate any number of faults with any shapes of fault regions without disabling healthy nodes. The performance of the method is extensively evaluated, and the results show that our proposed method is valid for mesh topology, which has graceful performance degradation and allows the network to remain fully operational facing with the failures.
Low data rate, IEEE 802.15.4a wireless personal area networks (WPANs) are introduced in industrial field level communication. The standard supports a carrier less baseband impulse radio-time hopping ultra wide band (IR-TH UWB) physical layer (PHY), which due to its small duty cycle and very short pulse widths is robust against dense multipath propagation and interferences. The medium access control (MAC) allows the use of slotted Aloha, carrier sense multiple access/collision avoidance (CSMA/CA) and guaranteed slots (GTS) mechanisms. However, for its efficient deployment in Field Bus systems, an adaption is required to improve reliability and real time performance. We propose a self configuring MAC to handle asynchronous alarm requests during ongoing synchronous transmissions. Addressable TH codes in fixed time slots of modified superframe structure are employed. On behalf of these amendments, expressions for accessing delays of synchronous and asynchronous data are derived with traffic modeling. In addition, the error performance of the selected PHY is evaluated over realistic IEEE 802.15.4a industrial non line of sight (NLOS) channel in comparison over additive white Gaussian noise (AWGN). Selective Rake (SRake) receiver is used to recover the signal in dense multipath propagated environment. Impulse response and the power delay profile (PDP) of the channel are generated and presented.
Broadband Powerline Communications (PLC) is currently used in two application domains: Access networks and In-Home communications. Access networks are used by the service providers to provide network services to their customers, and In-Home applications are used by the users privately inside their households. In the situation where an Access network is connected to a household with an In-Home network, the PLC communication signal can propagate between both networks. Because both systems utilize the same frequency band, their transmissions may interfere with each other. As a natural characteristic of the PLC system, the user is not moving but their statuses and resource requirements are changing during the run-time. Some coexistence protocols are proposed, however, they are not designed for optimizing the available transmission capacity. Moreover, a distributed approach is required when it is not possible to organize a centralized controller for both Access and In-Home domains. Therefore, we propose a channel self-organizing protocol which allows both domains to cooperate in order to share and optimize the transmission capacity dynamically. Employing this algorithm, each system detects the interferences from its neighbors and organizes its resources to achieve the overall maximum channel utilization. On the other hand, the protocol maintains the balance of channels per user in different cells. The proposed channel allocation protocol is analyzed and evaluated by means of two example network models.
Based on the available power line structure, a PLC network is configured as a multiple cells network, including several adjacent access and in-home cells. In a PLC cell, the users are not moving but their statuses and traffic demands are changing during the run-time. These cells may interference with each other; therefore, each cell has a fixed amount of transmission capacity for its transmissions. The transmission capacity is defined as a set of channels. Since the active users and traffic demands in each cell are variable, the users in different cells may get different amount of resource for their transmission. This situation leads to the problem of unfairness between users. Furthermore, when the cells are not interfering, they can use the same channels for their parallel transmissions. The overall multi-cell structure may also change dynamically due to the activation and deactivation of some cells, which requires a method for re-arranging the allocated channels between the working cells. Therefore, a method which allows the dynamic sharing of the transmission capacity between the cells is required. In this paper, we propose a negotiation strategy to allow the cells to cooperate and dynamically share the channels in a distributed fashion. The negotiation strategy is based on two procedures, seizing the channels if they are free and releasing channels if a cell has more channels per user than its neighbors. The proposal is analyzed and several aspects are discussed in this paper.
Single frequency network technique is applied to powerline communications networks to ensure an efficient data transmission in large networks. We consider an application of this technique for ground traffic control in airports which has high quality of service requirements, particularly regarding transmission delays of time-critical messages. Performance of the well-known slotted ALOHA protocol is not sufficient. Therefore, we propose a novel protocol called slotted ALOHA with local acknowledgments (SALA), ensuring significantly higher performance than the basic protocol solution, which results with a higher network utilization and reduced transmission delays
To enhance the reliability of narrowband PLC (Power Line Communication) in low-voltage network, inspired by the structure and invulnerability of spider web, a new PLC network model is proposed in this paper. The characteristics of the model and the transformational process of low-voltage distribution network from physical topology to artificially spider web logical topology are thoroughly discussed. New networking algorithm and route- reconstruction algorithm are put forward. A two-state Markov model is used to simulate a terminal node and the time-delay characteristic of the new algorithm is analyzed by modeling. Based on Opnet14.5, simulation and comparison are conducted, which prove that the new network model has advantages in improving the communication reliability of PLC network. new network model and automatic routing are conducted to improve narrowband PLC reliability, dynamic routing algorithm based on artificial spiderweb is put forward and the results and analysis of the simulation are presented.
In this paper, a new network model - Erlang multiplexing model (Erlang M model) is given, which is used to describe the relationship between traffic, wireless channel amounts, access capacity and multiplexing ratio. Based on this Erlang M model, the wireless channel resources planning for data service can be more detailed and accurate, which is different from the traditional planning way that is leading by manual experience. This method has been used in the planning of Beijing's mobile network and well proved.
The opportunities and applications for a large group of coordinating autonomous underwater vehicles (AUV) is exciting and provides greater exploration opportunities than fixed sensor nodes or using a single AUV. The work presented in this paper is the development of a Medium Access Control Protocol for a cluster of small autonomous vehicles working in a centralized network topology. Acoustic communication links are typically used for underwater operations, however are substantially limited by the physics of acoustic propagation which require essentially new scheduling protocols to those being used and developed for packet radio networks. This paper provides a discussion and overview of the essential issues for developing a new MAC protocol for a cluster of closely operating underwater vehicles and presents some performance results for a proposed Adaptive Token Polling Protocol.
Slotted ALOHA is one of the earliest proposed contention-based medium access solutions for wireless networks and it remains a common approach in literature. In this paper, we present the throughput and delay performance analysis for a slotted ALOHA system with periodic server vacations. By this, we mean that the service is governed by a fixed cycle composed of alternating active and inactive periods, representative of an energy-efficient medium access solution that implements sleep cycles. To our knowledge, ours is the first work to fully develop this analysis.
Supervisory Control and Data Acquisition (SCADA) systems control and monitor industrial and critical infrastructure functions, such as electricity, gas, water, waste, railway and traffic. Recently, SCADA systems have been targeted by an increasing number of attacks from the Internet due to its grow- ing connectivity to Enterprise networks. Traditional techniques and models of identifying attacks, and quantifying its impact cannot be directly applied to SCADA systems because of their limited resources and real-time operating characteristics. This paper introduces a novel framework for evaluating survivability of SCADA systems from a service-oriented perspective. The proposed framework uses an analytical model to evaluate the status of services and the survivability of the overall system using queuing theory and Bayesian networks. Preliminary results are shown and some improvements on the model are identified.
Various analytical methods are proposed and used to evaluate the performance of a given slotted ring network. In this paper a station buffer of a slotted ring is analyzed using discrete time queueing technique with an assumption that the time is divided into small segments known as slots. We analyzed and propose the matrix geometric method (MGM) as the solution technique for the model under discussion. Our model has finite station buffer and its behaviour is evaluated through MGM technique by utilizing the characteristics of two-dimensional Markov chain. Various performance measures are validated with their corresponding results such as, throughput, delay and probability of packet rejection.
Even if Bluetooth has not been specifically designated for WLANs (Wireless Local Area Networks) and the interconnection of computers, the possibility of establishing low-cost wireless connections makes this technology attractive for this kind of context also. In this paper we assess, by means of a simulative approach that takes the complete physical and MAC level aspects into account, the performance of a Bluetooth-based WLAN adopting a roll-call polling protocol under realistic channel conditions, that is, in the presence of the typical impairments of indoor wireless communications (fading, etc); moreover, we propose an analytical formulation to derive the maximum throughput offered by a Bluetooth link and we suggest a call admission control technique based on the previous analytical considerations.
We investigate MAC protocols for large powerline communications (PLC) networks using single frequency network (SFN) technique. The performances of the MAC protocols are evaluated by both analytical and simulation modeling. The analytical and simulation results are similar, and in some cases are almost the same. We also see the difference performance behavior of slotted ALOHA in the PLC-SFN networks compared with traditional communication systems.
In this paper, a novel approach is developed to evaluate the overall performance of a local area network as well as to monitor some possible intrusion detections. The data is obtained via system utility 'ping' and huge data is analyzed via statistical methods. Finally, an overall performance index is defined and simulation experiments in three months proved the effectiveness of the proposed performance index. A software package is developed based on these ideas.
In this paper a link adaptation (LA) strategy to be implemented in a Bluetooth piconet is investigated: the performance level that can be achieved is derived and the comparison with the case of no LA is performed. Suitable definitions of the performance figures are given and starting from the knowledge of the physical level performance obtained via simulation, their analytical evaluation is performed in both the cases of LA and no LA. All aspects related to the propagation characteristics of the environment, the modulation/demodulation and coding/decoding techniques, and the multiple access strategy are taken into account in an integrated way.
A large number of non-converging 2.5G and 3G wireless standards have emerged, over the past, such as, GSM/GPRS, EDGE, IS-95, IxRTT, IxEV -DO, IS-54, IS-136, and IMT2000/UMTS etc. In parallel, unlicensed broadband wireless networks such as IEEE 802.11 and HIPELAN/2 are also spawning across the world. The failure to agree, worldwide, on a unique radio access mode, for economic and political reasons, is forcing the telecommunications community to explore reconfigurable user terminals. Such a reconfigurable radio system will allow the user to roam across geographic areas offering radio access connections using differing standards. To date research into reconfigurable MSs or handsets, also known as SDRs, has predominantly focused on converting physical layer processing into a modularized programmable environment. Although necessary, this only represents a fraction of the overall support and technology required to realize the potential of the concept. Reconfigurability of the higher layers of the protocol stacks is equally important. This paper proposes a software configurable wireless MAC layer design based on the state machine approach. The design exploits the existence of common characteristics in different wireless protocols such as slotted Aloha, p-persistent CSMA, GPRS RLC/MAC protocol and 802.11 MAC protocol. The generic MAC layer design can be re-configured by the software to adapt to a specific wireless MAC layer and be a basis for SDR (software defined radio) mobile station. A methodology for configuring the MAC layer design is also introduced.
In this paper we present an analytical model for the estimation of the blocking probability as a function of the offered traffic per user in a cellular environment, where capacity is determined by hard blocking and the average number of users per cell is small. By the term "hard" capacity we mean the maximum number of users that can be served by a base station. Using a statistical model, the paper shows that the number of mobiles audible to a base that have that base as the strongest one has a Poisson distribution whose mean is given in terms of the mean densities of mobiles and base stations and the parameters of the attenuation law. The model proposed here does not represent a tool for detailed network planning, but it is a helpful (and from the computational viewpoint simple) means for network dimensioning.
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