Abstract The voltage reference represents a very important stage in applications such RF system. Most bandgap voltage reference designer use bipolar junction transistors (BJT) to easily reduce the temperature dependence and supply voltage, other use an operational amplifiers (OP-AMP), which are generally very complex and may present undesirable parasite and high power consumption. This paper presents a approach for output variation... The voltage reference represents a very important stage in applications such RF system. Most bandgap voltage reference designer use bipolar junction transistors (BJT) to easily reduce the temperature dependence and supply voltage, other use an operational amplifiers (OP-AMP), which are generally very complex and may present undesirable parasite and high power consumption. This paper presents a approach for output variation compensation of bandgap voltage reference. The proposed technique is considered as an efficient calibration strategy for the BGR used to minimize the chip size and current consumption. Read More Read Less

Abstract Despite the increase of applications related to spatial or spatiotemporal databases, the assistance brought to the designer of these bases remains very poor. As in the classic data base domain (not spatial) the use of conceptual models, methods and tools of design is very current, in the real time geoprocessing application domain it is an exception. Yet, these databases are... Despite the increase of applications related to spatial or spatiotemporal databases, the assistance brought to the designer of these bases remains very poor. As in the classic data base domain (not spatial) the use of conceptual models, methods and tools of design is very current, in the real time geoprocessing application domain it is an exception. Yet, these databases are very often complex and would require a phase of detailed design. The subject of this article is to present the disadvantages of different existing methods and we propose profile UML dressing real time constraints in the field of real time geoprocessing applications. The GRT (Geographic Real Time) profile target the design of real-time geoprocessing applications. Read More Read Less

Abstract We propose a decentralized approach to processing transactions in a replicated database, under partial replication in Peer-To-Peer (P2P) environments. In order to solve problems of concurrent updates, we propose an architecture based on quorums, this architecture allows assigning a unique timestamp to each distributed transaction in order to built local precedence order graph is from at each peer , to... We propose a decentralized approach to processing transactions in a replicated database, under partial replication in Peer-To-Peer (P2P) environments. In order to solve problems of concurrent updates, we propose an architecture based on quorums, this architecture allows assigning a unique timestamp to each distributed transaction in order to built local precedence order graph is from at each peer , to select the servers replicas and to coordinate the distributed execution of the transaction. Read More Read Less

Abstract Throughput is the main concern in Wireless Mesh Networks (WMNs). The standard congestion control mechanism of TCP[7] is not able to handle the special properties of a shared wireless multi-hop channel well. Given that the unreliable wireless links and congestion are likely to be the source of throughput degradation in the network, reliable transport protocol conception dealing with wireless links... Throughput is the main concern in Wireless Mesh Networks (WMNs). The standard congestion control mechanism of TCP[7] is not able to handle the special properties of a shared wireless multi-hop channel well. Given that the unreliable wireless links and congestion are likely to be the source of throughput degradation in the network, reliable transport protocol conception dealing with wireless links properties can significantly improve the performance of such networks. This paper presents a novel transport protocol called MTCP, which covers these needs. Simulation results show that MTCP outperform TCP and its ad-hoc wireless variants in terms of reliability and congestion control. Read More Read Less

Abstract The quality of service (QoS) of several real time multimedia applications has become a crucial research topic. One of the challenges to achieve QoS requirements is to determine how to allocate system bandwidth to various applications with the respect of their QoS requirements. In this paper, we proposed a Call Admission Control scheme based on QoS requirements of different traffic... The quality of service (QoS) of several real time multimedia applications has become a crucial research topic. One of the challenges to achieve QoS requirements is to determine how to allocate system bandwidth to various applications with the respect of their QoS requirements. In this paper, we proposed a Call Admission Control scheme based on QoS requirements of different traffic types in mobile WiMAX. Our proposed admission control scheme is suitable for real time applications as it gives more priority to real time service classes. Numerical results show that the proposed CAC scheme could be the better choice for admission control in terms of call blocking probability of the connections and bandwidth utilization of the system. Read More Read Less

Abstract In this paper, we study the problem of QoS group communication in a heterogeneous network, which consists of multiple MANETs attached to the backbone Internet. We propose a heuristic multicast algorithm called DDCMA (Delay and Delay Variation Constraint Multicast Algorithm). DDCMA is designed for solving the DVBMT (Delay- and delay Variation- Bounded Multicast Tree) problem, which has been proved to... In this paper, we study the problem of QoS group communication in a heterogeneous network, which consists of multiple MANETs attached to the backbone Internet. We propose a heuristic multicast algorithm called DDCMA (Delay and Delay Variation Constraint Multicast Algorithm). DDCMA is designed for solving the DVBMT (Delay- and delay Variation- Bounded Multicast Tree) problem, which has been proved to be NP-complete. The literature studies consider only end-to-end delay bound and minimizing delay variation. In this paper, we improve and extend previous well known from literature heterogeneous network algorithms to provide scalable and stable multicast services on the Internet. The algorithm defines QoS parameters as constraints on both delay and delay variation. Furthermore, we introduce a new Delay–Variation Estimation Scheme for heterogeneous networks, which can help DDCMA achieve better performance in terms of the multicast delay variation than some well known algorithms. Theoretical analysis is given to show the correctness of DDCMA and its performance in terms of the multicast delay variation. Read More Read Less