Abstract Optical Burst Switching (OBS) has become a mature technology to support the current and next generation Internet over optical network backbones. In OBS networks contention is the main source of burst loss that can reduce the performance of the higher layers. Burst retransmission is a reactive loss recovery mechanism, which attempts to resolve contention by retransmitting the contended burst at... Optical Burst Switching (OBS) has become a mature technology to support the current and next generation Internet over optical network backbones. In OBS networks contention is the main source of burst loss that can reduce the performance of the higher layers. Burst retransmission is a reactive loss recovery mechanism, which attempts to resolve contention by retransmitting the contended burst at the OBS layer. Burst cloning is a proactive loss recovery mechanism, which attempts to prevent burst loss by sending two copies of the same burst; if the first copy is lost, the second copy may still be able to reach the destination. Burst retransmission is better suited when the load is low, however burst cloning is better suited when the load is high. In order to combines the advantages of burst retransmission at low load with the benefits of burst cloning at high load, we propose a hybrid scheme for star OBS networks that aims to control the extra load due to the both loss recovery mechanisms. Simulation results show that our hybrid scheme can achieve better overall network performance than both burst retransmission scheme and burst cloning scheme. Read More Read Less

Abstract Wireless Sensor Networks (WSNs) have been regarded as distinguished Ad Hoc networks that can be used for specific applications. Since a WSN consists of potentially hundreds of low cost, small size and battery powered sensor nodes, it has more potentials than other Ad Hoc networks to be deployed in many emerging applications. The WSNs raised many new challenges such as:... Wireless Sensor Networks (WSNs) have been regarded as distinguished Ad Hoc networks that can be used for specific applications. Since a WSN consists of potentially hundreds of low cost, small size and battery powered sensor nodes, it has more potentials than other Ad Hoc networks to be deployed in many emerging applications. The WSNs raised many new challenges such as: the design of embedded sensors and wireless networking technologies, in other words the routing protocols. Scalability of routing protocols used in WSNs is a critical issue due to the extremely high node numbers and relatively high node density. A good routing protocol has to be scalable and adaptive to the changes in the network topology. Thus protocols must perform well as the network grows larger or as the workload increases. Many Ad Hoc routing protocols such as Ad Hoc On demand Distance Vector (AODV), Dynamic Source Routing (DSR), and Destination Sequenced Distance Vector (DSDV), have been proved to perform well on the Mobile Ad Hoc networks (MANETs). In this paper, a performance study is carried out, using some simulation network models, to investigate how well AODV, DSR, and DSDV routing protocols work on WSNs, in static environments, using NS-2 simulator. The performance study focuses on the impact of the network size, network density (up to 500 nodes), number of sources (data connections), and the type of generated traffic model. The performance metrics to be used in this work are average end-to-end delay, packet delivery fraction (PDF), routing overheads (ROH), and average energy consumption per received packet. Read More Read Less

Abstract A optimized speed controller for permanent magnet synchronous motor (PMSM) is investigated in this paper, in which genetic algorithm (GA), direct torque control (DTC) concept, and neural networks space vector modulation (NNSVM) are integrated to achieve high performance for speed and torque responses. A GA is integrated to optimize the proportional integral (PI) controller. While NNSVM is contributed to reduce... A optimized speed controller for permanent magnet synchronous motor (PMSM) is investigated in this paper, in which genetic algorithm (GA), direct torque control (DTC) concept, and neural networks space vector modulation (NNSVM) are integrated to achieve high performance for speed and torque responses. A GA is integrated to optimize the proportional integral (PI) controller. While NNSVM is contributed to reduce more the ripples of mechanical speed and torque of PMSM, like that combination elements of artificial intelligence, proposed control reacts as, ensemble of intelligent human is gathered to solve a mathematical or physical problem in a little time than one of them. Simulation results show that the proposed controller provides high-performance dynamic characteristics and is robust with regard to plant parameter variations. Furthermore, comparing with the other controller, the harmonic ripples is much reduced by the proposed controller. Read More Read Less

Abstract In this paper, an algorithm for implementing Interleave Division Multiple Access (IDMA) is introduced and also a permutation polynomial interleaver (PPI) is suggested as a user specific interleaver in IDMA .The proposed technique can solve the memory cost problem for chip level interleavers and reduce the amount of information exchange between mobile stations and base stations to specify the interleaver... In this paper, an algorithm for implementing Interleave Division Multiple Access (IDMA) is introduced and also a permutation polynomial interleaver (PPI) is suggested as a user specific interleaver in IDMA .The proposed technique can solve the memory cost problem for chip level interleavers and reduce the amount of information exchange between mobile stations and base stations to specify the interleaver used as there identifications. We compare the proposed PPI with recent interleaver designs such as Random, Tree and Prime Interleaver. Performance analysis of IDMA with Binary phase shift keying (BPSK) modulation employing the proposed PPI in Additive White Gaussian Noise (AWGN) channel is carried out. In addition to that, we compare between interleavers from point of view complexity & bandwidth against number of user. Read More Read Less