The design of computer and communication systems has been based, for decades, on the fundamental ... more The design of computer and communication systems has been based, for decades, on the fundamental assumption that the objective of all users is to improve their own performance. In recent years we have experienced a wave of DDoS attacks threatening the welfare of the internet. These are launched by malicious users whose pure incentive is to degrade the performance of other, innocent, users. The traditional systems turn out to be quite vulnerable to these attacks. The objective of this work is to take a first step to close this fundamental gap, aiming at laying a foundation that can be used in future computer/network designs taking into account the malicious users. Our approach is based on proposing a metric that evaluates the vulnerability of a system. We then evaluate the commonly used data structure in network mechanisms, the hash data structure, using our vulnerability metric. We show that a Closed Hash is much more vulnerable than an Open Hash to DDoS attacks, even though the two systems are considered to be equivalent via traditional performance evaluation. We also apply the metric to queueing mechanisms common to computer and communications systems. Lastly we apply it to the practical case of a hash table whose requests are controlled by a queue, showing that even after the attack has ended, the regular users still suffer from performance degradation or even a total denial of service.
Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we c... more Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we compare their fairness level? These questions are usually answered by handwaving as no fundamental research in this topic was yet conducted. Polling systems are widely used in many computer networks where several users compete for access to a common resource. Fairness is a fundamental aspect of polling systems; perhaps it serves as the motivation behind various polling schemes. Despite this fundamental role, fairness to customers in polling systems has not been extensively studied to date. This work is an attempt to model fairness in polling systems and study the relative fairness of various polling schemes. We focus, in the context of this work, on evaluating the system’s obedience to the FCFS policy as a measure of the fairness experienced by the individual customers. Using this metric we study the cyclic polling system under five different service disciplines: exhaustive, gated, binomial-gated, two-stage gated and globally-gated. For these systems we derive their “fairness” level both in a discrete system model and in a continuous model. We use the analysis as well as numerical examples to provide basic observations on fairness of polling systems.
The objective of this work is the modeling and analysis of multi-queue single-server systems cons... more The objective of this work is the modeling and analysis of multi-queue single-server systems consisting of many queues. The size of such systems imposes difficulties in either applying numerical procedures or in using simulations. We address the problem of whether a very large multi-queue single-server system (polling system), consisting of 100 or more queues, can be modeled by a significantly smaller system without considerably distorting its performance. In particular we study systems in which the service discipline is either exhaustive or gated and the service times in the different queues are identically distributed. We consider the delay incurred by an arbitrary customer in the system as the performance measure of interest.The main result of this paper is that in this framework a polling system consisting of several queues can approximate the behavior of a very large system fairly accurately. However, an approximation by a system consisting of a single queue (with vacation periods) will yield a fairly poor approximation. We propose an algorithm for transforming the original system (called System A) into the approximate system (called System B). We discuss the errors introduced by this transformation and provide bounds for the error in the estimates of the mean customer delay. Numerical results show that System B is good for predicting the tail probabilities of System A as well.
Proceedings of the 13th EAI International Conference on Performance Evaluation Methodologies and Tools, 2020
We consider the planning problem of a unique cellular model in which parked vehicles, termed Vehi... more We consider the planning problem of a unique cellular model in which parked vehicles, termed Vehicular Relay Nodes (VeRNs), assist the network by relaying data to and from users. VeRNs can lower cellular network load and provide a scalable solution to the explosive growth in data demand. The VeRN model presents a new paradigm that significantly differs from toady's cellular deployments that are based solely on fixed infrastructure. Consequently, known deployment planning methods are inapplicable. The complexity arises from utilizing vehicles which adds stochastic resource variables to the stochastic data demand variables, as well as from the deployment structure/topology and the cost trade-offs between fixed resources, stochastic resources, and user demand. We present a holistic solution for this unique deployment planning problem. Our solution is based on the combination of three methodologies, which enables us establishing the convexity, and thus greediness properties of the problem. This allows focusing the analysis on deriving marginal values, instead of full system analysis. We further propose an approach to approximate the marginal values supported by effective state space bounds. Numerical results show that the method is efficient, and addresses various distribution settings.
Abstract We consider a resource allocation problem in a geographically distributed cloud network,... more Abstract We consider a resource allocation problem in a geographically distributed cloud network, where the goal is to obtain the capacities of the servers across the network in order to minimize the overall cost. In this study, the system resources (servers) are subject to failures, due to occasional breakdowns or cyber attacks. As a result, the servers supply is of a stochastic nature. From an optimization point of view, we are facing a non-convex multi-dimensional problem. For the solution, we propose an efficient algorithm to obtain the optimal capacities of the servers in all the regions in the network, where computational experience is presented and discussed. We then numerically analyze the effect of the supply stochastic properties, namely expected volume, variability and correlation across regions, on system performance. The methodology and the results can be used to evaluate the effect of cyber attacks on resource allocation in geographically distributed systems and on the planning of these systems.
Cloud computing task management has a critical role in the efficient operation of the cloud resou... more Cloud computing task management has a critical role in the efficient operation of the cloud resources, i.e., the servers. The task management handles critical and complicated decisions, overcoming the inherent dynamic nature of cloud computing systems and the additional complexity due to the large magnitude of resources in such systems (tens of thousands of servers). Due to the fact that servers may fail, task management is required to conduct both task admissions and task preservation decisions. Moreover, both these decisions require considering future system trajectories and the interplay between preservation and admission. In this paper we study the combined problem of task admission and preservation in a dynamic environment of cloud computing systems through analysis of a queueing system based on a Markov decision process (MDP). We show that the optimal operational policy is of a double switching curve type. On face value, the extraction of the optimal policy is rather complicated, yet our analysis reveals that the optimal policy can be reduced to a single rule, since the rules can effectively be decoupled. Based on this result, we propose two heuristic approaches that approximate the optimal rule for the most relevant system settings in cloud computing systems. Our results provide a simple policy scheme for the combined admission and preservation problem that can be applied in a complex cloud computing environments, and eliminate the need for sophisticated real-time control mechanisms.
A new deployment scheme proposes to leverage the on-board connectivity capabilities of vehicles a... more A new deployment scheme proposes to leverage the on-board connectivity capabilities of vehicles and turn them (while they are parked) to vehicular relay nodes (VeRNs). The use of on-street parked vehicles as relays within the cellular network is compelling as it can reduce the investments of the operators in deploying infrastructure while increasing the coverage and capacity of the network. Thus, overcoming the exponential growth in users' data demand in a more cost-effective manner compared to traditional fixed infrastructure based deployments. Due to the dynamic nature of vehicles, there are challenges in the analysis and operations of this network. This is due to the fact that current analysis methods assume that the infrastructure is fixed. Thus, in this paper, we develop analytical tools to investigate the gain of utilizing VeRNs. We derive closed-form approximation expressions for two types of analysis, relevant for cellular deployments: a user focused analysis and a VeRN focused analysis. These results can be used for planning and operations of the system. Our extensive simulations show the accuracy and flexibility of our analysis scheme, as well as the high potential of VeRNs as a layer in cellular deployments. Furthermore, we demonstrate and investigate a unique scalability property of this deployment scheme. Index Terms-Heterogeneous networks, relay nodes, cellular deployments, vehicular relay nodes. I. INTRODUCTION V EHICULAR Relay Nodes (VeRNs) were recently proposed as an additional nomadic layer to cellular deployments [1], [2]. VeRNs are on-street parked vehicles with wireless relaying capabilities, which are activated on demand and only when needed. For example, vehicles located (parked) at city centers can be activated to enhance the cellular network during peak demand periods. Vehicles can act as VeRNs (relays) due to the fact that nowadays they are already equipped with wireless capabilities such as cellular (LTE) UE and WiFi Access-Point (AP) [3]. Thus, VeRNs can relay data to and from users via a 2-hop link which can be based on various options: cellular link to the basestation and WiFi link to the users, or cellular link to the BS and cellular device-to-device (D2D) [4], [5] to the users. Hence, VeRNs are a viable solution for nowadays 4G-LTE [6] and future 5G
Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we c... more Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we compare their fairness level? These questions are usually answered by handwaving as no fundamental research in this topic was yet conducted. Polling systems are widely used in many computer networks where several users compete for access to a common resource. Fairness is a fundamental aspect of polling systems; perhaps it serves as the motivation behind various polling schemes. Despite this fundamental role, fairness to customers in polling systems has not been extensively studied to date. This work is an attempt to model fairness in polling systems and study the relative fairness of various polling schemes. We focus, in the context of this work, on evaluating the system’s obedience to the FCFS policy as a measure of the fairness experienced by the individual customers. Using this metric we study the cyclic polling system under five different service disciplines: exhaustive, gated, binomial-gated, two-stage gated and globally-gated. For these systems we derive their “fairness” level both in a discrete system model and in a continuous model. We use the analysis as well as numerical examples to provide basic observations on fairness of polling systems.
Recently, [8] has proposed that heterogeneity of infectiousness (and susceptibility) across indiv... more Recently, [8] has proposed that heterogeneity of infectiousness (and susceptibility) across individuals in infectious diseases, plays a major role in affecting the Herd Immunity Thresh-old (HIT). Such heterogeneity has been observed in COVID-19 and is recognized as overdis-persion (or “super-spreading”). The model of [8] suggests that super-spreaders contribute significantly to the effective reproduction factor, R, and that they are likely to get infected and immune early in the process. Consequently, under R0 ≈ 3 (attributed to COVID-19), the Herd Immunity Threshold (HIT) is as low as 5%, in contrast to 67% according to the traditional models [1, 2, 4, 10].This work follows up on [8] and proposes that heterogeneity of infectiousness (susceptibility) has two “faces” whose mix affects dramatically the HIT: (1) Personal-Trait-, and (2) Event-Based-Infectiousness (Susceptibility). The former is a personal trait of specific individuals (super-spreaders) and is nullified once those indiv...
Probability in the Engineering and Informational Sciences, Oct 1, 2008
... 9. Kingman, JFC (1962). The effect of queue discipline on waiting time variance, Proceedings ... more ... 9. Kingman, JFC (1962). The effect of queue discipline on waiting time variance, Proceedings of the Cambridge Philosophical Society, 58: 163-164. ... 17. Piccard, D. (2005). Outline of an extended book review, Stanford Encyclopedia of Philosophy. ...
Fairness is an inherent and fundamental factor of queue service disciplines in a large variety of... more Fairness is an inherent and fundamental factor of queue service disciplines in a large variety of queueing applications, ranging from airport and supermarket waiting lines to computer and communication queueing systems. Recent empirical studies show that fairness is highly important to queueing customers in practical scenarios. Despite this importance, queueing theory has devoted very little effort to this subject and an agreed upon measure for evaluating the fairness of queueing systems does not exist. In this work we propose RAQFM, a Resource Allocation Queueing Fairness Measure. The measure is built under the understanding that a widely accepted measure must adhere to the common sense intuition of researchers as well as practitioners and customers, and must also be based on widely accepted principles of social justice. We present the methodology of RAQFM and the principles on which it is based. We discuss its properties, emphasizing the way they appeal to one's intuition. We provide a methodology by which a wide variety of queueing systems can be analyzed to derive their fairness value.
... 23, Measuring fairness in queues - Avi-Itzhak, Levy - 2004. 22, Resource sharing for efficien... more ... 23, Measuring fairness in queues - Avi-Itzhak, Levy - 2004. 22, Resource sharing for efficiency in traffic systems - Smith, Whitt - 1981. ... 13, Quantifying fairness in queueing systems: principles, approaches and applicability - Avi-Itzhak, Levy, et al. ...
ABSTRACT Consideration is given to the problem of dynamically controlling a computer communicatio... more ABSTRACT Consideration is given to the problem of dynamically controlling a computer communication network consisting of N stations that compete for the use of a single channel. The channel is needed by the stations in order to transfer the packetized information they got from independent sources to a central storage device. The stations, which have some local storage capacity, are modeled as finite queues fed by independent Poisson streams and the channel as a single exponential server. The performance objective is to avoid situations in which any of the queues is fully (blocking). The authors also consider systems in which the queues are fed by the server and the objective is to avoid situations in which any of the queues is empty (starvation), and a hybrid system, consisting of both types of queue. Many computer and communication systems fall within the framework of these models. The goal is to get a good control policy for these systems. The authors first prove certain structural properties of the optimal solution for the case N =2. These properties lead them to conclude that it is unlikely that a closed-form expression for the optimal policy could be found, but at the same time guide the derivation of a heuristic decision rule
Mobile user tracking is a major issue in wireless networks. Previous studies and traditional appr... more Mobile user tracking is a major issue in wireless networks. Previous studies and traditional approaches dealt only with tracking algorithms which adapt themselves to the user activity.
A multiple access protocol that is particularly suitable for cellular Internet access and satelli... more A multiple access protocol that is particularly suitable for cellular Internet access and satellite-based networks with on-board processing is developed. The basic idea is that when a user wishes to send a message, it transmits with a probability paccess that depends on the load on the channel. Under conditions of low load, the probability paccess approaches 1, while at high load paccess is relatively low. This media access control protocol guarantees high channel utilization at high load, as well as low delay at low load periods. Using the statistical usage of the shared channel, the load is estimated with certain uncertainty. Our analysis shows that using the statistical usage of the shared channel, the optimal access probability can be well estimated for a broad class of load distribution patterns. In addition, we propose to use a central station to broadcast the value of paccess in networks with poor collision detection capability, or long feedback delay. The proposed method is ...
The design of computer and communication systems has been based, for decades, on the fundamental ... more The design of computer and communication systems has been based, for decades, on the fundamental assumption that the objective of all users is to improve their own performance. In recent years we have experienced a wave of DDoS attacks threatening the welfare of the internet. These are launched by malicious users whose pure incentive is to degrade the performance of other, innocent, users. The traditional systems turn out to be quite vulnerable to these attacks. The objective of this work is to take a first step to close this fundamental gap, aiming at laying a foundation that can be used in future computer/network designs taking into account the malicious users. Our approach is based on proposing a metric that evaluates the vulnerability of a system. We then evaluate the commonly used data structure in network mechanisms, the hash data structure, using our vulnerability metric. We show that a Closed Hash is much more vulnerable than an Open Hash to DDoS attacks, even though the two systems are considered to be equivalent via traditional performance evaluation. We also apply the metric to queueing mechanisms common to computer and communications systems. Lastly we apply it to the practical case of a hash table whose requests are controlled by a queue, showing that even after the attack has ended, the regular users still suffer from performance degradation or even a total denial of service.
Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we c... more Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we compare their fairness level? These questions are usually answered by handwaving as no fundamental research in this topic was yet conducted. Polling systems are widely used in many computer networks where several users compete for access to a common resource. Fairness is a fundamental aspect of polling systems; perhaps it serves as the motivation behind various polling schemes. Despite this fundamental role, fairness to customers in polling systems has not been extensively studied to date. This work is an attempt to model fairness in polling systems and study the relative fairness of various polling schemes. We focus, in the context of this work, on evaluating the system’s obedience to the FCFS policy as a measure of the fairness experienced by the individual customers. Using this metric we study the cyclic polling system under five different service disciplines: exhaustive, gated, binomial-gated, two-stage gated and globally-gated. For these systems we derive their “fairness” level both in a discrete system model and in a continuous model. We use the analysis as well as numerical examples to provide basic observations on fairness of polling systems.
The objective of this work is the modeling and analysis of multi-queue single-server systems cons... more The objective of this work is the modeling and analysis of multi-queue single-server systems consisting of many queues. The size of such systems imposes difficulties in either applying numerical procedures or in using simulations. We address the problem of whether a very large multi-queue single-server system (polling system), consisting of 100 or more queues, can be modeled by a significantly smaller system without considerably distorting its performance. In particular we study systems in which the service discipline is either exhaustive or gated and the service times in the different queues are identically distributed. We consider the delay incurred by an arbitrary customer in the system as the performance measure of interest.The main result of this paper is that in this framework a polling system consisting of several queues can approximate the behavior of a very large system fairly accurately. However, an approximation by a system consisting of a single queue (with vacation periods) will yield a fairly poor approximation. We propose an algorithm for transforming the original system (called System A) into the approximate system (called System B). We discuss the errors introduced by this transformation and provide bounds for the error in the estimates of the mean customer delay. Numerical results show that System B is good for predicting the tail probabilities of System A as well.
Proceedings of the 13th EAI International Conference on Performance Evaluation Methodologies and Tools, 2020
We consider the planning problem of a unique cellular model in which parked vehicles, termed Vehi... more We consider the planning problem of a unique cellular model in which parked vehicles, termed Vehicular Relay Nodes (VeRNs), assist the network by relaying data to and from users. VeRNs can lower cellular network load and provide a scalable solution to the explosive growth in data demand. The VeRN model presents a new paradigm that significantly differs from toady's cellular deployments that are based solely on fixed infrastructure. Consequently, known deployment planning methods are inapplicable. The complexity arises from utilizing vehicles which adds stochastic resource variables to the stochastic data demand variables, as well as from the deployment structure/topology and the cost trade-offs between fixed resources, stochastic resources, and user demand. We present a holistic solution for this unique deployment planning problem. Our solution is based on the combination of three methodologies, which enables us establishing the convexity, and thus greediness properties of the problem. This allows focusing the analysis on deriving marginal values, instead of full system analysis. We further propose an approach to approximate the marginal values supported by effective state space bounds. Numerical results show that the method is efficient, and addresses various distribution settings.
Abstract We consider a resource allocation problem in a geographically distributed cloud network,... more Abstract We consider a resource allocation problem in a geographically distributed cloud network, where the goal is to obtain the capacities of the servers across the network in order to minimize the overall cost. In this study, the system resources (servers) are subject to failures, due to occasional breakdowns or cyber attacks. As a result, the servers supply is of a stochastic nature. From an optimization point of view, we are facing a non-convex multi-dimensional problem. For the solution, we propose an efficient algorithm to obtain the optimal capacities of the servers in all the regions in the network, where computational experience is presented and discussed. We then numerically analyze the effect of the supply stochastic properties, namely expected volume, variability and correlation across regions, on system performance. The methodology and the results can be used to evaluate the effect of cyber attacks on resource allocation in geographically distributed systems and on the planning of these systems.
Cloud computing task management has a critical role in the efficient operation of the cloud resou... more Cloud computing task management has a critical role in the efficient operation of the cloud resources, i.e., the servers. The task management handles critical and complicated decisions, overcoming the inherent dynamic nature of cloud computing systems and the additional complexity due to the large magnitude of resources in such systems (tens of thousands of servers). Due to the fact that servers may fail, task management is required to conduct both task admissions and task preservation decisions. Moreover, both these decisions require considering future system trajectories and the interplay between preservation and admission. In this paper we study the combined problem of task admission and preservation in a dynamic environment of cloud computing systems through analysis of a queueing system based on a Markov decision process (MDP). We show that the optimal operational policy is of a double switching curve type. On face value, the extraction of the optimal policy is rather complicated, yet our analysis reveals that the optimal policy can be reduced to a single rule, since the rules can effectively be decoupled. Based on this result, we propose two heuristic approaches that approximate the optimal rule for the most relevant system settings in cloud computing systems. Our results provide a simple policy scheme for the combined admission and preservation problem that can be applied in a complex cloud computing environments, and eliminate the need for sophisticated real-time control mechanisms.
A new deployment scheme proposes to leverage the on-board connectivity capabilities of vehicles a... more A new deployment scheme proposes to leverage the on-board connectivity capabilities of vehicles and turn them (while they are parked) to vehicular relay nodes (VeRNs). The use of on-street parked vehicles as relays within the cellular network is compelling as it can reduce the investments of the operators in deploying infrastructure while increasing the coverage and capacity of the network. Thus, overcoming the exponential growth in users' data demand in a more cost-effective manner compared to traditional fixed infrastructure based deployments. Due to the dynamic nature of vehicles, there are challenges in the analysis and operations of this network. This is due to the fact that current analysis methods assume that the infrastructure is fixed. Thus, in this paper, we develop analytical tools to investigate the gain of utilizing VeRNs. We derive closed-form approximation expressions for two types of analysis, relevant for cellular deployments: a user focused analysis and a VeRN focused analysis. These results can be used for planning and operations of the system. Our extensive simulations show the accuracy and flexibility of our analysis scheme, as well as the high potential of VeRNs as a layer in cellular deployments. Furthermore, we demonstrate and investigate a unique scalability property of this deployment scheme. Index Terms-Heterogeneous networks, relay nodes, cellular deployments, vehicular relay nodes. I. INTRODUCTION V EHICULAR Relay Nodes (VeRNs) were recently proposed as an additional nomadic layer to cellular deployments [1], [2]. VeRNs are on-street parked vehicles with wireless relaying capabilities, which are activated on demand and only when needed. For example, vehicles located (parked) at city centers can be activated to enhance the cellular network during peak demand periods. Vehicles can act as VeRNs (relays) due to the fact that nowadays they are already equipped with wireless capabilities such as cellular (LTE) UE and WiFi Access-Point (AP) [3]. Thus, VeRNs can relay data to and from users via a 2-hop link which can be based on various options: cellular link to the basestation and WiFi link to the users, or cellular link to the BS and cellular device-to-device (D2D) [4], [5] to the users. Hence, VeRNs are a viable solution for nowadays 4G-LTE [6] and future 5G
Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we c... more Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we compare their fairness level? These questions are usually answered by handwaving as no fundamental research in this topic was yet conducted. Polling systems are widely used in many computer networks where several users compete for access to a common resource. Fairness is a fundamental aspect of polling systems; perhaps it serves as the motivation behind various polling schemes. Despite this fundamental role, fairness to customers in polling systems has not been extensively studied to date. This work is an attempt to model fairness in polling systems and study the relative fairness of various polling schemes. We focus, in the context of this work, on evaluating the system’s obedience to the FCFS policy as a measure of the fairness experienced by the individual customers. Using this metric we study the cyclic polling system under five different service disciplines: exhaustive, gated, binomial-gated, two-stage gated and globally-gated. For these systems we derive their “fairness” level both in a discrete system model and in a continuous model. We use the analysis as well as numerical examples to provide basic observations on fairness of polling systems.
Recently, [8] has proposed that heterogeneity of infectiousness (and susceptibility) across indiv... more Recently, [8] has proposed that heterogeneity of infectiousness (and susceptibility) across individuals in infectious diseases, plays a major role in affecting the Herd Immunity Thresh-old (HIT). Such heterogeneity has been observed in COVID-19 and is recognized as overdis-persion (or “super-spreading”). The model of [8] suggests that super-spreaders contribute significantly to the effective reproduction factor, R, and that they are likely to get infected and immune early in the process. Consequently, under R0 ≈ 3 (attributed to COVID-19), the Herd Immunity Threshold (HIT) is as low as 5%, in contrast to 67% according to the traditional models [1, 2, 4, 10].This work follows up on [8] and proposes that heterogeneity of infectiousness (susceptibility) has two “faces” whose mix affects dramatically the HIT: (1) Personal-Trait-, and (2) Event-Based-Infectiousness (Susceptibility). The former is a personal trait of specific individuals (super-spreaders) and is nullified once those indiv...
Probability in the Engineering and Informational Sciences, Oct 1, 2008
... 9. Kingman, JFC (1962). The effect of queue discipline on waiting time variance, Proceedings ... more ... 9. Kingman, JFC (1962). The effect of queue discipline on waiting time variance, Proceedings of the Cambridge Philosophical Society, 58: 163-164. ... 17. Piccard, D. (2005). Outline of an extended book review, Stanford Encyclopedia of Philosophy. ...
Fairness is an inherent and fundamental factor of queue service disciplines in a large variety of... more Fairness is an inherent and fundamental factor of queue service disciplines in a large variety of queueing applications, ranging from airport and supermarket waiting lines to computer and communication queueing systems. Recent empirical studies show that fairness is highly important to queueing customers in practical scenarios. Despite this importance, queueing theory has devoted very little effort to this subject and an agreed upon measure for evaluating the fairness of queueing systems does not exist. In this work we propose RAQFM, a Resource Allocation Queueing Fairness Measure. The measure is built under the understanding that a widely accepted measure must adhere to the common sense intuition of researchers as well as practitioners and customers, and must also be based on widely accepted principles of social justice. We present the methodology of RAQFM and the principles on which it is based. We discuss its properties, emphasizing the way they appeal to one's intuition. We provide a methodology by which a wide variety of queueing systems can be analyzed to derive their fairness value.
... 23, Measuring fairness in queues - Avi-Itzhak, Levy - 2004. 22, Resource sharing for efficien... more ... 23, Measuring fairness in queues - Avi-Itzhak, Levy - 2004. 22, Resource sharing for efficiency in traffic systems - Smith, Whitt - 1981. ... 13, Quantifying fairness in queueing systems: principles, approaches and applicability - Avi-Itzhak, Levy, et al. ...
ABSTRACT Consideration is given to the problem of dynamically controlling a computer communicatio... more ABSTRACT Consideration is given to the problem of dynamically controlling a computer communication network consisting of N stations that compete for the use of a single channel. The channel is needed by the stations in order to transfer the packetized information they got from independent sources to a central storage device. The stations, which have some local storage capacity, are modeled as finite queues fed by independent Poisson streams and the channel as a single exponential server. The performance objective is to avoid situations in which any of the queues is fully (blocking). The authors also consider systems in which the queues are fed by the server and the objective is to avoid situations in which any of the queues is empty (starvation), and a hybrid system, consisting of both types of queue. Many computer and communication systems fall within the framework of these models. The goal is to get a good control policy for these systems. The authors first prove certain structural properties of the optimal solution for the case N =2. These properties lead them to conclude that it is unlikely that a closed-form expression for the optimal policy could be found, but at the same time guide the derivation of a heuristic decision rule
Mobile user tracking is a major issue in wireless networks. Previous studies and traditional appr... more Mobile user tracking is a major issue in wireless networks. Previous studies and traditional approaches dealt only with tracking algorithms which adapt themselves to the user activity.
A multiple access protocol that is particularly suitable for cellular Internet access and satelli... more A multiple access protocol that is particularly suitable for cellular Internet access and satellite-based networks with on-board processing is developed. The basic idea is that when a user wishes to send a message, it transmits with a probability paccess that depends on the load on the channel. Under conditions of low load, the probability paccess approaches 1, while at high load paccess is relatively low. This media access control protocol guarantees high channel utilization at high load, as well as low delay at low load periods. Using the statistical usage of the shared channel, the load is estimated with certain uncertainty. Our analysis shows that using the statistical usage of the shared channel, the optimal access probability can be well estimated for a broad class of load distribution patterns. In addition, we propose to use a central station to broadcast the value of paccess in networks with poor collision detection capability, or long feedback delay. The proposed method is ...
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Papers by Hanoch Levy