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The complex valued matched filter correlators consume maximum power in the DS/SS CDMA receivers. These correlators accumulate 1024 samples lying in the range-7 to +7. This accumulation needs 3 data bits, 1 sign bit and 10 extra bits for overflow. Hence, the correlator can be implemented as a cascade of 4-bit full adder and a 10-bit incrementer. As a ripple carry adder (RCA) consumes the least power among all the existing adder architectures, we have implemented the 4-bit adder as a RCA. Previous incrementers were implemented as ripple counters. In this paper we propose a novel incrementer which is faster than a ripple counter based incrementer. Hence, it can be operated at a reduced voltage resulting in considerable power reduction. The incrementer is implemented using multiplexers, AND gates and TSPC registers. The ripplecounter

Dynamic load distribution algorithm performance in heterogeneous distributed system for I/O- intensive task

The international standard IEEE 802.11 Wireless LAN protocol is a popular standard for wireless local area networks. Its medium access control layer (MAC) is a carrier sense multiple access with collision avoidance (CSMA/CA) design, although collisions cannot always be prevented, randomized exponential backoff rule is used in the retransmission scheme to minimize the likelihood of repeated collisions. To work around this problem, we identify state transition of the protocol that can be used to simplify the models and make verification feasible. This paper explains the state transition model of two way handshake mechanism of IEEE 802.11 standard for MAC DCF. Using these observations, a time variant generalized state transition model for channel, sender and destination station has been described. The proposed model has been validated using network simulator ns-2.

Abstract-Optical burst switching (OBS) is developed as an alternative switching technology, which combines advantages of both Optical circuit switching (OCS) and Optical packet switching (OPS) and avoids the disadvantages. In OBS control packet called control burst is separated from data packet called data burst. A control burst is sent in advance, which configures the switches in the path for the data burst. Due to lack of adequate contention resolution technique data burst loss is high in OBS. Schemes such as fiber delay line (FDL), wavelength conversion, deflection routing are the solution to prevent network congestion. But they have their own limitations. So a contention resolution technique is needed in OBS. In this paper we propose a scheme to minimize contention and to control traffic flow in the network. The proposed scheme logically divides a given network to clusters and selects a node as cluster head from each cluster. Cluster head keeps track of the resources available in the network and exchange the status of the resources among themselves to maintain up-to-date information. A node within a cluster that wishes to send a burst make request to its cluster head for a available wavelength on the path to destination. If a unused wavelength is available on the path to its destination, then it send a reply message with the available wavelength else send a reply no wavelength is available. Node after receiving a reply from the cluster head send a control burst followed by data burst on the wavelength that it has received from cluster head. If the reply says no wavelength is available then it waits for some specified time and sends another request. Since the cluster heads maintain the status of the resources at any time, t, it will minimize the contention of bursts. We made a comparison between the different techniques using simulation. Our simulation result shows propose method gives lower burst loss. I.

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Performance of distributed systems can be improved from scheduling of tasks aspect. A good scheduling algorithm can enhance the performance of the distributed system significantly. In this paper we have compared the performance of batch mode and immediate mode schedulers in heterogeneous distributed computing environment. An immediate mode scheduler only considers a single task for scheduling on a FCFS (first come, first served) basis while a batch mode scheduler considers a number of tasks at once for scheduling. In particular we have used two immediate mode scheduler: (i) the earliest first (EF) algorithm and (ii) the lightest loaded (LL), and two batch mode heuristic scheduler (i) the max-min (MX) scheduler and (ii) min-min (MM) scheduler. The main aim of max-min (MX) scheduler is to have the largest tasks scheduled as early as possible, with smaller tasks at the end filling in the gaps. The min-min (MM) scheduler is similar to the MX scheduler, except tasks are sorted in ascending order according to size. We have simulated the scheduler behavior with our simulator developed using Matlab, where each task is with the expected execution time and expected completion time on a particular machine. This findings are used to design an adaptive dynamic scheduler that selects the best strategy depending on load at a particular time frame. The results are also useful in deciding the effective group size of a processor pool (cluster) for the HDCS, which can be remodeled as a tree of resource clusters that are geographically distributed. We have also outline the proposed scheduler framework that uses (i) a global scheduler, responsible for determining where to send task submitted to it, a local scheduler, responsible for determining the order in which tasks are executed at that particular processor pool. 1.

Abstract—A mobile ad hoc network (MANET) is an infrastructure less distributed network without any central control in which each node jointly participate for routing. Topology of the network is not fixed and varies dynamically with time. Routing in such an infrastructure less network is still a challenging task. In this paper we propose a novel load balanced routing for mobile ad hoc network. In this approach load is defined as the number bytes of packets transmitted by the node and the number of nodes from which it is currently receiving the data packets. Route is constructed in on demand fashion. In our approach there is a provision for handling the data collision occurred by interference by selecting the disjoint paths. For each node contributing in routing a flag bit is set with the time limit TTL once the time limit exceeds this value flag bit is reset. By this flag bit we are able to monitor the data collisions occurred due to interference of the data packets. Each node keeps track of the number of data packets transmitted by him as well as the data packets transmitted by its one hop neighboring nodes along with their flag bit status for the current time interval, by limited broadcasts of hello messages. For relaying the route request the flag bits of neighboring nodes must be at reset status. By this approach we are able to enhance the performance of DSR routing algorithm for larger extent. Keywords-control information, interference, load balanced routing, route coupling. I.

Abstract — The Web Services have gained considerable attention over the last few years. Video-on-Demand (VoD) systems have resulted in speedy growth of the web traffic. Therefore the concept of load balancer aimed to distribute the tasks to different Web Servers to reduce response times was introduced. This paper attempts to analyze the performance of FCFS, Randomized, Genetic algorithms and Heuristics algorithms for selecting server to meet the VoD requirement. Performances of these algorithms have been simulated with parameters like makespan and average resource utilization for different server models. This paper presents an efficient heuristic called Ga-max-min for distributing the load among servers. Heuristics like min-min and max-min are also applied to heterogeneous server farms and the result is compared with the proposed heuristic for VOD Servers. Ga-max-min was found to provide lower makespan and higher resource utilization than the genetic algorithm.

Abstract—Minimizing the energy consumption in cloud computing environment is one of the key research issues. Power consumed by computing resources and storage in cloud can be optimized through energy aware resource allocation. As the resource utilization by the tasks are directly relates to energy consumption, the task consolidation are being used to optimize the energy consumption. An energy efficient heuristic algorithm has been proposed and compared with three energy-aware task consolidation heuristics by varying number of tasks. The proposed task consolidation algorithm minimizes total energy consumed by the cloud computing system. Keywords—Cloud Computing, task consolidation, energy aware, virtual machine, energy-efficient resource allocation, resource utilization. I.