A Real-Time Testbed for Distributed Algorithms:Evaluation of Average Consensus inSimulated Vehicular Ad Hoc Networks
Examensarbete för masterexamen
Computer systems and networks (MPCSN), MSc
Intelligent transportation systems consist of applications which use communication capabilities of vehicles to solve tasks that require cooperation with other vehicles. One of the possible applications is cooperative positioning, in which vehicles increase the accuracy of their positions by sharing positioning information with each other. Previous research has suggested using average consensus to share this information. Average consensus is a type of distributed algorithm that, in a system where each node performs a measurement of some value, can make all nodes reach agreement on the average of the set of measurements. This thesis evaluates the performance of average consensus algorithms in vehicular ad hoc networks. Full-scale experiments on vehicular systems are costly, but it is also not necessarily desired to fully simulate a vehicular system. This thesis presents a testbed where we opt to fully simulate the vehicular communication network. The vehicles that are part of the network can be simulated using either virtual nodes or a scaled down physical robot system. An 802.11p wireless network, which has been suggested for vehicular ad hoc networks, is simulated using the ns-3 network simulator. Additionally, some properties that cause the wireless network to be unreliable are simulated. Furthermore, in this thesis, three average consensus algorithms are implemented with some modifications to account for the properties of vehicular ad hoc networks. These algorithms are evaluated in the created testbed, in order to study their performance in such a network. We observe that consensus converges asymptotically in a simulation of randomly moving nodes, and that the consensus states of the nodes oscillate around the true average when new nodes are allowed to enter the system during consensus. The consensus converges to a state that does not necessarily coincide exactly with the true average, which is to be expected since some packets are lost due the simulated wireless network not being fully reliable. We also demonstrate that performing average consensus on the position of an object can improve the precision of driving in a physical system of moving robots.
Data- och informationsvetenskap , Computer and Information Science