Study on QoS support in 802.11e-based multi-hop vehicular wireless ad hoc networks

Multimedia communications over vehicular ad hoc networks (VANET) will play an important role in the future intelligent transport system (ITS). QoS support for VANET therefore becomes an essential problem. In this paper, we first study the QoS performance in multi-hop VANET by using the standard IEEE 802.11e EDCA MAC and our proposed triple-constraint QoS routing protocol, Delay-Reliability-Hop (DeReHQ). In particular, we evaluate the DeReHQ protocol together with EDCA in highway and urban areas. Simulation results show that end-to-end delay performance can sometimes be achieved when both 802.11e EDCA and DeReHQ extended AODV are used. However, further studies on cross-layer optimization for QoS support in multi-hop environment are required

An effective ant-colony based routing algorithm for mobile ad-hoc network

An effective Ant-Colony based routing algorithm for mobile ad-hoc network is proposed in this paper. In this routing scheme, each path is marked by path grade, which is calculated from the combination of multiple constrained QoS parameters such as the time delay, packet loss rate and bandwidth, etc. packet routing is decided by the path grade and the queue buffer length of the node. The advantage of this scheme is that it can effectively improve the packet delivery ratio and reduce the end-to-end delay. The simulation results show that our proposed algorithm can improve the packet delivery ratio by 9%-22% and the end-to-end delay can be reduced by 14%-16% as compared with the conventional QAODV and ARA routing schemes

A method for direct calculation of quadratic turning points

For a given one-parameter nonlinear system, the simplest bifurcation is the quadratic turning bifurcation where the Jacobian matrix becomes singular due to rank deficiency 1. To overcome the difficulty in solving the quadratic turning point caused by the singularity of the Jacobian matrix, the conventional Newton method can be applied to the so-called Moore-Spence determination system to solve for the quadratic turning point. However, the Moore-Spence system has much higher dimensions and causes much more complexity in factorisation of the extended Jacobian matrix. In the paper, by introducing an auxiliary variable and an auxiliary linear equation into Newton iterations in solving the Moore-Spence determination system, a matrix reduction technique can be worked out to solve the Moore-Spence extended equations much more efficiently. The high dimensions of the matrix can thus be reduced and the complexity involved in matrix factorisation can be reduced noticeably. The technique is proposed for general nonlinear systems. Formulation is derived for applying this technique to solving quadratic turning points, or say nose points, on load-flow solution curves of power systems. Computer tests on the IEEE 30-busbar system and a 2416-busbar East China power system are reported to show the effectiveness of the suggested technique.published_or_final_versio

Optimization of MPPT step size in stand-alone solar pumping systems

In a stand-alone solar pumping system with a pump driven by an induction motor, the step size in maximum power point tracking (MPPT) methods greatly affects the dynamics and stability of the system. In this paper, we analyze some phenomena appearing in the contrastive experiments which have been carried out for about one year, and give a solution to determine the step size based on system parameters and controller capabilities. The contrastive experiments show that the system performance can be obviously improved by the optimized step size together with an adequate smoothing capacitor. © 2006 IEEE.published_or_final_versio

Multi-infeed HVDC/AC power system modeling and analysis with dynamic phasor application

In this paper, dynamic phasor method has been applied to HVDC transmission system and FACTS device modeling. A hybrid-model simulation algorithm is suggested for transient stability analysis with HVDC transmission system and FACTS devices in dynamic phasor models and other ac system elements in electromechanical models. Computer test results show clearly that the proposed hybrid-model simulation algorithm can be applied for transient stability analysis effectively and accurately. A multi-infeed HVDC/AC (MIDC/AC) system is studied using the suggested hybrid-model transient stability program. The dynamic behaviors of MIDC/AC system under different circumstances are discussed. The characteristics of HVDC system recovery and recovery strategy for MIDC system are considered in the stability analysis. Furthermore, the impacts of advanced FACTS controllers such as STATCOM on system dynamic are studied for enhance system operation security. © 2000 IEEE.published_or_final_versio

Incorporating UPFC model into the power system toolbox of theMATLAB for transient stability study

In this paper, power frequency model for unified power flow controller (UPFC) is presented with its DC link capacitor dynamics included. A novel interface of UPFC to AC network for transient stability study is then suggested and realised using Power System Toolbox (PST) of MATLAB. The control strategies for UPFC shunt and series elements are also discussed. Computer results on a 4-generator interconnected test power system show that the convergence and accuracy of the suggested interface are challenging and the suggested interface makes it very easy to incorporate the UPFC model into the conventional transient stability programme. The results also show that the UPFC control strategy had strong impacts on the performance of UPFC.published_or_final_versio