Nowadays, the importance of real time condition monitoring and control for wind turbine (WT) is increasing because WTs are installed on remote site such as mountains and offshore. In this paper, we implement a monitoring and control system for a small-scale wind turbine. The monitoring and control system consists of data collection units, control unit and coordinator. The data collection units collect data from various sensors: temperature, humidity, atmospheric pressure, wind direction, wind speed and vibration. And the data collection units transmit sensing data to a coordinator. A ZigBee is used to communicate between a coordinator and data collection units. The coordinator is also communicate with PC and smart device through RS232 and Bluetooth, respectively. The GUI is implemented based on Android and LabVIEW to show the sensing data. The GUI based on LabVIEW can control the wind turbine direction using control unit.

Recently, we proposed the EPON-based communication network architectures for large-scale wind power farms (WPFs). The proposed architectures offer robust, reliable, high speed and cost effective solution compared with conventional switched-based architectures. In this paper, we first introduce the proposed WPF communication network. Then, we design a sensor data frame structure to carry the sensing data from different wind turbine (WT) parts such as rotor, transformer, nacelle, etc. The data frame includes the logical node ID (LNID), sensor node ID (SNID), sensor type (ST) and sensor data based on IEC61400-25 standard. Fixed bandwidth allocation (FBA) is considered to enable each WT of transmitting its data efficiently within the allocated time slot. We present an analytical model that describes the upstream traffic between the WTs and the control center. Using queueing theory approach, the WT performance is evaluated in view of the bandwidth utilization, queue delay and queue length. In case of WPF, the proposed architecture eliminates the turbines traffic from transit through other WTs which improves the network reliability.

With the continuous growth of traffic for years, both the monetary cost and the power consumption of the Internet increase sharply at the same time. Especially, backbone networks will become the main contributor of the overall Internet cost and power consumption. Except the feature of huge total amount, the traffic in future backbone networks will also show high heterogeneity in bandwidth requirement. Based on the variety of those traffic demands, the mixed-line-rate (MLR) schemes have been proposed in recent years. The MLR schemes are considered to b e able to support flexibility for network provisioning. To utilize resources in MLR backbone networks efficiently, logical topology design is an important issue. However, previous studies about logical topology design have focused on optimizing either monetary cost or power consumption of the whole network. In this paper, we design logical topology for optical MLR backbone networks by considering both energy efficiency and cost efficiency. The network cost is defined as an integrity consisting of the monetary cost and the power consumption of the whole network. Then, a Mixed Integer Linear Programming (MILP) formulation is presented to minimize the network cost. In order to evaluate the proposed formulation, it is applied on illustrative case studies. Finally, the numerical results are analyzed and discussed.

Although the conventional duty cycle MAC protocols such as RMAC for wireless sensor networks (WSNs) perform well in aspects of saving energy and reducing end-to-end delivery latency, they are designed independently and require an extra routing protocol in the network layer to provide path information for the MAC layer. We propose a novel cross-layer duty cycle MAC protocol with data forwarding towards pipeline feature (P-MAC) for WSNs. P-MAC divides all sensor nodes in the network into different grades around the sink. Each node identifies its grade according to its logic hop distance to the sink and simultaneously establishes a sleep/wakeup schedule based on its grade. Those nodes in the same grade keep the same schedule, while which is staggered with the schedule of the nodes in the adjacent grade. Then a variation of RTS/CTS handshake mechanism is used to forward data continuously in a pipeline fashion from the higher grade nodes to the lower grade nodes and finally to the sink. No extra routing overhead is needed, and the superiority of duty-cycling is kept. The performance of PMAC and RMAC are evaluated and compared in terms of packet delivery latency and energy efficiency by OPNET simulation.

Over the past several years, a significant amount of research has been conducted in the areas of optical packet switching (OPS) and optical burst switching (OBS). This research has been motivated by the need for techniques that are capable of supporting the demanding requirements of emerging dynamic high-bandwidth network applications in a flexible and efficient manner. Although optical packet and burst switching have yet to be widely deployed in commercial settings, recent research progress indicates that such deployments are not infeasible in the near future. The authors review the literature on OPS and OBS. Basic concepts are discussed and an overview of current and emerging research issues and challenges for optical packet and burst switched networks is presented. The authors attempt to cover issues that are essential for the practical deployment of such networks and highlight promising research directions that are likely to facilitate such deployments.

Optical burst switching (OBS) is a promising technique for supporting high-capacity, bursty data traffic over optical wavelength-division-multiplexed (WDM) networks. An optical link failure may result in a huge amount of data (and revenue) loss, and it has been an important survivability concern in optical networks. In this paper, we study the fault- management issues related with a link failure in an OBS network. We propose to use pre-planned global rerouting to balance network load and to reroute bursts after a link fails. We apply optimization techniques to pre-plan explicit backup routes for failure scenarios. Our objective is to achieve optimal load balancing both before and after a failure such that the network state can still remain stable with minimum burst-loss probability when a failure occurs. We apply the pre-planned normal and backup routing tables to an OBS network, and study the network performance after a failure occur using illustrative numerical examples. The results show that the average burst-loss probability can be significantly reduced by 60% - from an average of 0.10 to 0.04 (when the normalized link load is less than 0.5) using globally-rerouted backup routes, when compared with the scheme without global rerouting. We also observe that the burst-loss probability is reduced by 43% - from an average of 0.07 to 0.04 (when the link load is less than 0.5) if the rerouting is done using optimization techniques, when compared with shortest-path routing.for Fault Management

We address the problem of connection preemption in a multi-class network environment. Our objective is: (i) to minimize the number of preempted connections, and (ii) to minimize the total preempted bandwidth, in that order. We show that this problem is NP-complete by reducing it to a well-known NP complete problem - the subset sum problem. Therefore, a known polynomial time algorithm, such as Minn.Conn [1], to solve this problem is suboptimal. We present an optimal algorithm with exponential complexity that can be used when the network load is light. We also present a fully polynomial time approximation algorithm that performs within a bounded factor from the optimal, and can be used in large networks having thousands of connections. We compare the performance of exact and approximate algorithms in a practical scenario by conducting simulations on a network representing twenty largest metros in the U.S. The simulations show that, on average, the approximate algorithm preempts bandwidth which is only a small fraction more as compared to that preempted by the exact algorithm, but is an order of magnitude more efficient in terms of execution time.

In label-switched networks such as MPLS, protection routing involves computing and setting up the backup paths at the same time when the primary paths are routed. It has previously been shown that two or more backup paths may share bandwidth along common links if such backup paths will never be activated simultaneously. Such sharing between the backup paths leads to reduced bandwidth reservations and, hence improved performance in terms of number of path requests that can be accommodated on the network (Aslam et al., 2005). We present a novel idea that backup paths may also share bandwidth with certain primary paths, thereby further reducing the overall bandwidth reservations on the network. This results in even more path requests being accommodated on the network. Sharing with primary paths is possible with any protection routing framework. To demonstrate this sharing, we use the NPP protection routing framework as an example (Aslam et al., 2005). We provide the enhancements to the NPP framework needed to exploit sharing with the primary paths. For the enhanced NPP framework, simulation results on various networks confirm that sharing with primary paths indeed results in better network utilization. This increased performance is achieved with bounded local state information and without requiring any additional routing or signaling overhead.

Optical burst switching (OBS) is a promising technique for supporting high-capacity bursty data traffic over optical wavelength-division-multiplexed (WDM) networks. A label-switched path can be established to forward a burst control packet (BCP) if each OBS node is augmented with an IP/MPLS controller. Such a network is called a labeled OBS (LOBS) network, and it can exploit the explicit routing and constraint-based routing properties supported in the MPLS framework to perform traffic and resource engineering. However, the burst-loss probability (denoted as BLP) can be large if the traffic is not properly engineered in a LOBS network, especially after a failure occurs. In this paper, we propose to use pre-planned global rerouting to balance network load and to restore bursts after a link fails. We apply optimization techniques to pre-plan explicit backup routes for failure scenarios. Our objective is to achieve optimal load balancing both before and after a failure such that the network state can still remain stable with minimum BLP when failure occurs. We apply the pre-planned global rerouting method in a LOBS network and study the performance of different rerouting schemes on some typical network topologies. Our illustrative numerical examples show that the BLP can be significantly reduced by 25%-99% (when the average link load is less than 0.5) using globally rerouted backup routes, when compared with the scheme without global rerouting. We also observe that the BLP is reduced by 20%-65% (when the average link load is less than 0.5) if the rerouting is done using optimization techniques, when compared with shortest-path routing.

This paper proposes a new call admission control scheme considering the call dropping probability of ongoing calls in LEO satellite networks. Quality of service (QoS) provisioning of low handover failure probability is used in the proposed call admission control (CAC) scheme to guarantee predefined acceptable call dropping probability for each call. To ensure the call dropping probability the handover failure probability has been formulated using the classification of the local traffic conditions and the derivation of generation probability for the equivalent case of handover failure event. The performance of the proposed scheme has been evaluated in terms of call dropping probability and handover failure probability. The performance evaluation results have clearly shown that the proposed CAC scheme guarantees the continuity of call connections with predefined QoS levels.

WDM ring networks built on dynamic WDM add-drop multiplexer allow a pair of source-destination (SD) nodes to exchange data packet directly without intermediate nodes on its routing path. This requires an efficient protocol that coordinates the process of data transmission through a control channel. We propose a reservation/Ack/transmission protocol (RATP) which is based on collision free reservation to efficiently use the wavelengths for data packet transmission. In order to maximize the utilization of wavelengths, a reserved wavelength is reused for other SD nodes. Access fairness is also provided among the network nodes by reusable fairness control (RFC). The proposed protocol is evaluated in terms of network throughput, delay and wavelength reuse efficiency.

In this paper, we propose an estimated-prorated slot allocation algorithm for VBR services in wireless ATM networks. The algorithm is based on a new control scheme, hybrid dynamic parameter (DP) control. The proposed hybrid DP control transmits a dynamic parameter through piggybacking or control slot according to the variation of buffer length. It provides the strengths of in-band control and out-of-band control, efficiency of resource usage and sufficiency of information. And it also improves the capability of the dynamic parameter through 2 bits. As the hybrid DP control scheme can offer nearly precise MAC level estimations of the requirements for each VBR VC, the proposed allocation algorithm makes it possible to obtain an ideal allocation efficiency. For the VBR traffic under consideration, the simulation results show that the proposed algorithm has better performance than conventional schemes in terms of allocation efficiency, delay and cell loss. Thus, we can confirm that the allocation algorithm based on hybrid DP control can maximize the channel utilization under variable traffic patterns.