Sari Branch, Islamic Azad UniversityJournal of Advances in Computer Research2345-606X4120130101Modeling Cooperation between Nodes in Wireless Networks by APD Game1122512ENAbbas ArghavaniComputer and Information Technology Department, Qazvin Islamic Azad University, Qazvin, IranAbdorasoul GhasemiFaculty of Electrical and Computer Engineering Department, K. N. Toosi University of Technology, Tehran, IranJournal Article20130514<em>Cooperation is the foundation of many protocols in wireless networks. Without cooperation, the performance of a network significantly decreases. Hence, all nodes in traditional networks are required to cooperate with each other.</em> <em>In this paper, instead of traditional networks, a network of rational and autonomous nodes is considered, which means that each node itself can decide whether to cooperate with its neighbor or not and performs something that benefits it. </em> <em>We have used Alternative Prisoner’s Dilemma game which is one of the classic games in the field of game theory, to model node's behavior in a nontraditional network. Then, by providing an approach based on Learning Automata, we've tried to encourage the nodes to cooperate with each other.</em>Sari Branch, Islamic Azad UniversityJournal of Advances in Computer Research2345-606X4120130101Pre-scheduling and Scheduling of Task Graph on Homogeneous Multiprocessor Systems13292524ENMarjan AbdeyazdanDepartment of Computer Engineering, Science and Research branch, Islamic Azad University,Tehran, IranSaeed ParsaDepartment of Computer Engineering, Iran University of Science and Technology, Tehran, IranAmir Masoud RahmaniDepartment of Computer Engineering, Science and Research branch, Islamic Azad University,Tehran, IranJournal Article20130516<em>Task graph scheduling is a multi-objective optimization and NP-hard problem. In this paper a new algorithm on homogeneous multiprocessors systems is proposed. Basically, scheduling algorithms are targeted to balance the two parameters of time and energy consumption. These two parameters are up to a certain limit in contrast with each other and improvement of one causes reduction in the other one. The problem is to achieve the trade-off between these two parameters. Pre-scheduling algorithms are mainly aimed at modifying the structure of task graph to gain optimal scheduling.</em> <em>In the proposed algorithm the suitable number of processors for scheduling the task graph is computed. The idea of Nash equilibrium is mainly applied to compute the appropriate number of processors in such a way that the idle time of the processors is reduced while their processing power is increased. Also, considering the communication costs and interdependencies, the tasks are merged as their earliest start time is reduced. In this way, the length of the critical path is reduced while the degree of parallelism is increased and ultimately the completion time is reduced.Our experimental result on a number of known benchmark graphs demonstrates the effect of our proposed algorithm.</em>Sari Branch, Islamic Azad UniversityJournal of Advances in Computer Research2345-606X4120130101VRED: An improvement over RED algorithm by using queue length growth velocity31382510ENShahram JamaliComputer Engineering Department, University of MohagheghArdabili, Ardabil, IranBita AlipasandiDepartment of Computer Engineering, Zanjan Branch, Islamic Azad University, Zanjan, IranNeda AlipasandiSama technical and vocational training college, Islamic Azad University,Ardabil Branch,
Ardabil, IranJournal Article20130514<em>Active Queue Management (AQM) plays an important role in the Internet congestion control. It tries to enhance congestion control, and to achieve tradeoff between bottleneck utilization and delay. Random Early Detection (RED) is the most popular active queue management algorithm that has been implemented in the in Internet routers and is trying to supply low delay and low packet loss. RED algorithm uses only the average queue length as a congestion meter to trigger packet dropping or packet marking as a congestion feedback. Since the average queue length considers only long–term behavior of any queue, this approach fails to see instantaneous changes of the queue length and hence its reaction is not fast enough. This paperincludes another meter i.e. queue length growth velocity to measure congestion level in the router. This leads to fast reaction to the congestion and hence improves the network performance. Simulation results show that the proposed algorithm outperforms RED algorithm in terms of number of dropped packets and bottleneck utilization.</em>