423 research outputs found
Efficiency analysis of load balancing games with and without activation costs
In this paper, we study two models of resource allocation games: the classical load-balancing game and its new variant involving resource activation costs. The resources we consider are identical and the social costs of the games are utilitarian, which are the average of all individual players' costs.
Using the social costs we assess the quality of pure Nash equilibria in terms of the price of anarchy (PoA) and the price of stability (PoS). For each game problem, we identify suitable problem parameters and provide a parametric bound on the PoA and the PoS. In the case of the load-balancing game, the parametric bounds we provide are sharp and asymptotically tight
Resilience of Traffic Networks with Partially Controlled Routing
This paper investigates the use of Infrastructure-To-Vehicle (I2V)
communication to generate routing suggestions for drivers in transportation
systems, with the goal of optimizing a measure of overall network congestion.
We define link-wise levels of trust to tolerate the non-cooperative behavior of
part of the driver population, and we propose a real-time optimization
mechanism that adapts to the instantaneous network conditions and to sudden
changes in the levels of trust. Our framework allows us to quantify the
improvement in travel time in relation to the degree at which drivers follow
the routing suggestions. We then study the resilience of the system, measured
as the smallest change in routing choices that results in roads reaching their
maximum capacity. Interestingly, our findings suggest that fluctuations in the
extent to which drivers follow the provided routing suggestions can cause
failures of certain links. These results imply that the benefits of using
Infrastructure-To-Vehicle communication come at the cost of new fragilities,
that should be appropriately addressed in order to guarantee the reliable
operation of the infrastructure.Comment: Accepted for presentation at the IEEE 2019 American Control
Conferenc
Resilience of Locally Routed Network Flows: More Capacity is Not Always Better
In this paper, we are concerned with the resilience of locally routed network
flows with finite link capacities. In this setting, an external inflow is
injected to the so-called origin nodes. The total inflow arriving at each node
is routed locally such that none of the outgoing links are overloaded unless
the node receives an inflow greater than its total outgoing capacity. A link
irreversibly fails if it is overloaded or if there is no operational link in
its immediate downstream to carry its flow. For such systems, resilience is
defined as the minimum amount of reduction in the link capacities that would
result in the failure of all the outgoing links of an origin node. We show that
such networks do not necessarily become more resilient as additional capacity
is built in the network. Moreover, when the external inflow does not exceed the
network capacity, selective reductions of capacity at certain links can
actually help averting the cascading failures, without requiring any change in
the local routing policies. This is an attractive feature as it is often easier
in practice to reduce the available capacity of some critical links than to add
physical capacity or to alter routing policies, e.g., when such policies are
determined by social behavior, as in the case of road traffic networks. The
results can thus be used for real-time monitoring of distance-to-failure in
such networks and devising a feasible course of actions to avert systemic
failures.Comment: Accepted to the IEEE Conference on Decision and Control (CDC), 201
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