Sharif Digital Repository

Apart from its security, an SIP (Session Initiation Protocol) authentication protocol shall be efficient; because in order to replace traditional telephony, VoIP services have to offer enough security and QoS compared to PSTN services. Recently, Srinivasan et al. proposed an efficient SIP authentication scheme. The low delay overhead introduced by their scheme, causes the total call setup time to be well within the acceptable limit recommended by ITU-T. Based on their work, this paper proposes an SIP authentication scheme. In both schemes, the end users are authenticated with the proxy server in their domain using the registrar server. Comparing with the Srinivasan et al.'s scheme, our... 

DC microgrids (MGs) are becoming popular as effective means to integrate different energy resources. Conventionally, the droop control is adopted as a decentralized control method for power sharing in DC MGs. However, current sharing accuracy or voltage regulation deteriorates due to the effects of line impedances. In this paper, a new adaptive control strategy is proposed for DC MGs. In low load conditions, the output currents of the DGs are far from their maximum acceptable limits. Therefore, current sharing accuracy is not important. As load increases, the output currents of the DGs approach their maximum acceptable limits. Therefore, at high load conditions, accurate current sharing is... 

In this paper, first, two new criteria, which are titled social welfare percent (SWP) and congestion cost percent (CCP), are defined for static transmission expansion planning in restructured power systems. Then by a simple example it will be shown that none of the already presented market-based criteria could completely and truly evaluate the transmission network expansion from market view. Hence the SWP and CCP criteria altogether are proposed to completely and truly evaluate the transmission network expansion. Then a least-investment cost expansion plan is searched that its SWP and CCP are in predefined acceptable limits. The results of applying of the proposed method are illustrated over... 

In this paper, first, two new criteria, which are titled social welfare percent (SWP) and congestion cost percent (CCP), are defined for static transmission expansion planning in restructured power systems. Then by a simple example it will be shown that none of the already presented market-based criteria could completely and truly evaluate the transmission network expansion from market view. Hence the SWP and CCP criteria altogether are proposed to completely and truly evaluate the transmission network expansion. Then a least-investment cost expansion plan is searched that its SWP and CCP are in predefined acceptable limits. The results of applying of the proposed method are illustrated over... 

With the introduction of restructuring concepts to traditional power systems, a great deal of attention is given to the utilization of distributed generation. Since the integration of DG units has been known as an alternative for main grid as a resource for energy supply, the determination of optimal sizing and sitting is an important issue in the planning procedure of DG. This work presents a comprehensive multi-objective model for integration of distributed generations into a distribution network, regarding various technical, economical and environmental issues such as reduction of carbon dioxide emissions and investment & running costs while the bus voltages shall be kept within...