Sleep Mode Analysis via Workload Decomposition

The goal of this paper is to establish a general approach for analyzing queueing models with repeated inhomogeneous vacations. The server goes on for a vacation if the inactivity prolongs more than the vacation trigger duration. Once the system enters in vacation mode, it may continue for several consecutive vacations. At the end of a vacation, the server goes on another vacation, possibly with a different probability distribution; if during the previous vacation there have been no arrivals. However the system enters in vacation mode only if the inactivity is persisted beyond defined trigger duration. In order to get an insight on the influence of parameters on the performance, we choose to study a simple M/G/1 queue (Poisson arrivals and general independent service times) which has the advantage of being tractable analytically. The theoretical model is applied to the problem of power saving for mobile devices in which the sleep durations of a device correspond to the vacations of the server. Various system performance metrics such as the frame response time and the economy of energy are derived. A constrained optimization problem is formulated to maximize the economy of energy achieved in power save mode, with constraints as QoS conditions to be met. An illustration of the proposed methods is shown with a WiMAX system scenario to obtain design parameters for better performance. Our analysis allows us not only to optimize the system parameters for a given traffic intensity but also to propose parameters that provide the best performance under worst case conditions

Unilateral Altruism in Network Routing Games with Atomic Players

We study a routing game in which one of the players unilaterally acts altruistically by taking into consideration the latency cost of other players as well as his own. By not playing selfishly, a player can not only improve the other players' equilibrium utility but also improve his own equilibrium utility. To quantify the effect, we define a metric called the Value of Unilateral Altruism (VoU) to be the ratio of the equilibrium utility of the altruistic user to the equilibrium utility he would have received in Nash equilibrium if he were selfish. We show by example that the VoU, in a game with nonlinear latency functions and atomic players, can be arbitrarily large. Since the Nash equilibrium social welfare of this example is arbitrarily far from social optimum, this example also has a Price of Anarchy (PoA) that is unbounded. The example is driven by there being a small number of players since the same example with non-atomic players yields a Nash equilibrium that is fully efficient

Combined Optimal Control of Activation and Transmission in Delay-Tolerant Networks

International audiencePerformance of a delay tolerant network has strong dependence on the nodes participating in data transportation. Such networks often face several resource constraints especially related to energy. Energy is consumed not only in data transmission but also in listening and in several signaling activities. On one hand these activities enhance the system's performance while on the other hand, they consume significant amount of energy even when they do not involve actual node transmission. Accordingly, in order to use energy efficiently, one may have to limit not only the amount of transmissions but also the amount of nodes that are active at each time. Therefore we study two coupled problems: i) the activation problem which determines when a mobile will turn on in order to receive packets, and ii) the problem of regulating the beaconing. We derive optimal energy management strategies by formulating the problem as an optimal control one, which we then explicitly solve. We also validate our findings through extensive simulations which are based on contact traces

Analysis of an M/G/1 Queue with Repeated Inhomogeneous Vacations with Application to IEEE 802.16e Power Saving Mechanism

International audienceThe goal of this paper is to establish a general approach for analyzing queueing models with repeated in homogeneous vacations. At the end of a vacation, the server goes on another vacation, possibly with a different probability distribution, if during the previous vacation there have been no arrivals. In case there have been one or more arrivals during a vacation then a busy period starts after a warm-up time. In order to get an insight on the influence of parameters on the performance, we choose to study a simple M/G/1 queue (Poisson arrivals and general independent service times) which has the advantage of being tractable analytically. The theoretical model is applied to the problem of power saving for mobile devices in which the sleep durations of a device correspond to the vacations of the server. Various system performance metrics such as the frame response time and the economy of energy are derived. A constrained optimization problem is formulated to maximize the economy of energy achieved in power save mode, with constraints as QoS conditions to be met. An illustration of the proposed methods is shown with a WiMAX system scenario to obtain design parameters for better performance. Our analysis allows us not only to optimize the system parameters for a given traffic intensity but also to propose parameters that provide the best performance under worst case conditions

Sleep Mode Analysis via Workload Decomposition

The goal of this paper is to establish a general approach for analyzing queueing models with repeated inhomogeneous vacations. Theserver goes on for a vacation if the inactivity prolongs more than a vacation trigger duration. Once the system enters in vacation mode,it may continue for several consecutive vacation. At the end of a vacation, the server goes on another vacation, possibly with a {\emdifferent} probability distribution, if during the previous vacation there have been no arrivals. However the system enters in vacationmode only if the inactivity is persisted beyond a defined trigger duration. In order to get an insight on the influence of parameterson the performance, we choose to study a simple $M/G/1$ queue (Poisson arrivals and general independent service times) which hasthe advantage of being tractable analytically. The theoretical model is applied to the problem of power saving for mobile devices inwhich the sleep durations of a device correspond to the vacations of the server. Various system performance metrics such as the frameresponse time and the economy of energy are derived. A constrained optimization problem is formulated to maximize the economy of energy achieved in power save mode, with constraints as QoS conditions to be met. An illustration of the proposed methods is shown with a WiMAX system scenario to obtain design parameters for better performance. Our analysis allows us not only to optimize the system parameters for a given traffic intensity but also to propose parameters that provide the best performance under worst caseconditions

Optimal Activation and Transmission Control in Delay Tolerant Networks

Much research has been devoted to maximizing the life time of mobile ad-hoc networks. Life time has often been defined as the time elapsed until the first node is out of battery power. In the context of static networks, this could lead to disconnectivity. In contrast, Delay Tolerant Networks (DTNs) leverage the mobility of relay nodes to compensate for lack of permanent connectivity and thus enable communication even after some nodes have depleted their stored energy. One can thus consider the life times of nodes as some additional parameters that can be controlled to optimize the performances of a DTN. In this paper, we consider two ways in which the energy state of a mobile can be controlled. Since both listening and transmission require energy, and since each of these has a different type of effect on the network performance, we study both the activation problem, which determines when a mobile will turn on in order to receive packets, and the transmission control problem, which can be done using transmission scheduling. The optimal solutions are shown to be of the threshold type. The paper introduces new methods to derive the threshold structure of optimal policies as previously used methods are not useful in this context due to the multidimensional nature of the problem. The findings are validated through extensive simulations