The Transmission Control Protocol - TCP has been widely researched in many different networking technologies such as wireless, optical, satellite, sensor, and wired since it is the most used protocol on the Internet. ...
详细信息
The Transmission Control Protocol - TCP has been widely researched in many different networking technologies such as wireless, optical, satellite, sensor, and wired since it is the most used protocol on the Internet. In Wireless mesh networks, this protocol still has challenges due to its origin and implementations for wired networks. This paper proposes an adaptation on the congestion control mechanism using information from the network layer to improve TCP performance through the vertical calibration across layer technique. The result is the Cross Layer Mesh - Transmission Control Protocol (CLM-TCP). To show the efficiency of the proposal, simulations in the NS-2 were carried out.
In Recent years, secure communications have become a important subject of research. The new service for wireless and wired networks is to provide confidentiality, authentication, authorization and data integrity. Secu...
详细信息
Conventional e-mail systems are prone to problems that affect their dependability. E-mail systems operate following a "push-based" approach: the sender side server pushes the e-mails it wants to send to the ...
Conventional e-mail systems are prone to problems that affect their dependability. E-mail systems operate following a "push-based" approach: the sender side server pushes the e-mails it wants to send to the corresponding receivers' servers. This approach may impose processing and storage overhead on the receiver side. This paper presents a peer-to-peer e-mail system in which messages are sent directly from senders to receivers using a "pull-based" approach. The sender stores locally all e-mails it intends to send, and notify their receivers using a global, distributed notification service. Receivers can then retrieve such notifications and decide if they want to receive the corresponding e-mails. If so, e-mails can be retrieved directly from their senders. This proposal is inspired from file sharing peer-to-peer systems, in which users locate and retrieve the contents they are looking for. A prototype was built to show the feasibility of the proposal, and experimental results show its viability.
E-mail services are essential in the Internet. However, the basic e-mail architecture presents problems that opens it to several threats. Alternatives have been proposed to solve some problems related with e-mail serv...
E-mail services are essential in the Internet. However, the basic e-mail architecture presents problems that opens it to several threats. Alternatives have been proposed to solve some problems related with e-mail services, offering reliability and scalability to those systems. This work presents a distributed trust model, allowing to create dynamic and decentralized trusted server lists, through the exclusion of servers used as spreaders of malicious messages. Many techniques were used to build it, like a social network model, message filters, message management, and a trust information storage and propagation model.
In sensor networks applied to monitoring applications, individual sensors may perform preassigned or on-demand tasks, or missions. Data updates (info-pages) may be sent to sensors from a command center, via a time-div...
详细信息
In sensor networks applied to monitoring applications, individual sensors may perform preassigned or on-demand tasks, or missions. Data updates (info-pages) may be sent to sensors from a command center, via a time-division broadcast channel. Sensors are normally put in sleep mode when not actively listening, in order to conserve energy in their batteries. Hence, a schedule is required that specifies when sensors should listen for updates and when they should sleep. The performance of such a schedule is evaluated based on data-related costs and sensor-related costs. Data-related costs reflect the obsoleteness of current sensor data, or the delay while sensors wait for updated instructions. Sensor-related costs reflect the energy that sensors consume while accessing the broadcast channel and while switching between the active and sleeping modes (rebooting). Our goal is a schedule with the minimum total cost. Previous related work has explored data-related costs, but listening cost has been addressed only under the assumption that the rebooting operation is free. This paper formulates a new cost model, which recognizes the cost of sensor rebooting. We derive an optimal schedule for the single-sensor setting. We proceed to consider schedules of multiple sensors, and formulate a mathematical program to find an optimal fractional schedule for this setting. Several heuristics for scheduling multiple sensors are introduced and analyzed, and various tradeoffs among the cost factors are demonstrated.
In order for solid state lighting technology to become a mainstream technology, one of the major challenges to overcome is increasing the efficiency of these devices while maintaining a proper color balance. A signifi...
详细信息
Distance learning is a learning style that can overcome the limitation of time and space. Because of the distance, teachers can not handle the student's learning situation, and they do not know whether the student...
详细信息
Distance learning is a learning style that can overcome the limitation of time and space. Because of the distance, teachers can not handle the student's learning situation, and they do not know whether the student is attentive, drowsy or absent. If teachers can know the student's affective state, they can overcome the difficult. The research applies the image recognition technologies to capture the face images of students when they are learning and analyzes their face features to evaluate the student's affective state by Fuzzy Integral. Finally, teachers can monitor the student's behavior by the detection results on the system interface.
Unmanned vehicle is future vehicle technology. Lateral control technology and longitudinal control technology are needed for unmanned vehicle. Automatic steering system is lateral control technology. A automatic steer...
详细信息
暂无评论