Sharif Digital Repository

One of the main parts of peer-to-peer multicast is the structure of overlay network. Most of the existing works utilize some common parameters for constructing overlay tree. These parameters are bandwidth and delay. The mismatch between current overlay structure and underlying network topology causes severe link stress and then leads to high end to end latency. According to these problems, we propose a new overlay construction algorithm called OLT in this thesis that finds the location of peers and tries to connect peers that are as close as possible. OLT exploits a number of heuristic techniques to reach an optimized tree even in case of peer heterogeneity and high churn rate. Our... 

The accessibility of broadband Internet to home users has pushed video broadcasting applications up in the list of the most favorite IP-based applications. A Peer-to-Peer overlay network is an attractive foundation for video streaming as it can shift the burden of content distribution from the network routers and servers to the clients. However, live Peer-to-Peer media streaming systems face many challenges such as bandwidth heterogeneity, node churn, and selfish nodes. Although many tree based and mesh based streaming protocols have been proposed, each has its own drawbacks such as unreliability and unfairness in the tree based and long startup delay and complex scheduling in mesh based... 

Multicasting has gained a lot of research attentions in facilitating group communications in wireless networks. Applying multicast mechanisms in Wireless Mesh Networks, brings a lot of benefits to these networks. In our research, we have introduced Cost-aware On-Demand Multicast Routing Protocol (C-ODMRP) as an extension of ODMRP that supports QoS provisioning for high quality applications in WMNs. In C-ODMRP, the nodes are prevented from applying the links that do not meet the QoS requirements. The multicast receivers are provided with resource-aware information to efficiently compute the cost of the routes when multiple routes from source to destination nodes are established. C-ODMRP takes... 

The accessibility of broadband Internet to home users has pushed video broadcasting applications up, in the list of most favorite applications in todays Internet. Such applications involve delivering the data which generated in a single sender to a set of users which are scattered around the world. While it was formerly believed that the IP-Multicasting is the mean to provide this kind of services, the trend has altered to the use of Application Layer Multicasting techniques due to their deployment simplicty. Since their advent, Peer to Peer applications has mitigated many problems previously unsolved in the field of communication. File sharing, distributed file systems, distributed data... 

Recently, the number of requests for multicast services through the wireless networks has increased. However, for successful deployment of these services, security and efficiency of content delivery must be provided at first. This thesis presents a new approach for secure multicast in wireless networks. This approach, CRAW (Combination of Re-keying and Authentication in Wireless networks) combines member authentication procedure with group key management protocol together to provide efficient re-keying. One-time password is proposed for member authentication and CKC (Code for Key Calculation) is suggested for group key management in wireless networks. In fact, the combination of... 

For applications such as videoconferencing, in which network resources are used for transmittingshared data, one may utilize multicasting so that resources are allocated in an efficient way. Due to the difficulties in implementing multicasting in the IP layer, designers tend to use the application layer of the OSI model to map an overlay network and implement the multicasting protocol in that layer, also known as Application Layer Multicasting (ALM). Besides the transfer of data, various concerns about the method such as application domain, group management, and routing mechanism are all handled by the ALM protocol. In this thesis, an ALMprotocol for multi-participant video conferencing in... 

Wireless mesh networks (WMN) appeared as popular communication networks supporting high speed and high throughput applications. They consist of mesh routers and mesh clients and they have unique characteristics like self organizing and self configuring of the mesh nodes that bring a great deal of efficiency, reliability and robustness to networks and decreases networks maintenance cost notably. Also WMNs provide an integration of different types of wireless networks by exploiting the gateway involvement. One of the important group communication technologies that offers high level of bandwidth conservation and efficiency is multicasting. It also decreases the cost of communication compared to... 

Today with growth of wireless communications and progress of small and cheap sensors which have capability of communication and calculation, wireless sensor networks are important and useful topic. But due to energy restrictions, efficient use of resources and increasing network lifetime, have been considered as key factors in network design. In this regard, using efficient multicast routing in energy consumption, for an efficient data transmission to specific number of nodes instead of all nodes code updates, information requests, task assignments and etc., is necessary.On the other hand these networks use unlicensed spectrum and suffer from collision due to congestion caused by other... 

According to the wide range of applications and numerous implementations, wireless networks are considered as a prominent means of providing data services, and have attracted the attention of many researches in recent years. Performance enhancement of these networks can be very beneficial to industry and wireless data service providers. Manipulation of relays, have been always considered as a proper means for improvement of network performance measures throughput and outage probability.In order to design relay networks efficiently, one should address two following problems: 1- determining transmission policy, and 2- relay location. In this research work, having in mind the optimality of... 

Overlay Peer-to-Peer networks opposed to their high scalability and more robustness against network errors, are more considerable rather than other content distribution approaches such as Client/Server and multicast video streaming. At this thesis we investigate the video streaming over these networks, which includes more than half of internet traffic nowadays.Localized video streaming is one of the techniques for improving quality of service (QoS) over peer-to-peer networks. With localization techniques, video chunks distribute among neighbors that have more proximity with each other and traffic is held localized over the network.We proposed a new metric for estimating network proximity of... 

Nowadays, video on demand causes a drastic increase in network traffic that it is expected that network traffic surpasses 45 exabytes per month until 2022; consequently, utilizing distributed memories known as caches across the network to alleviate the communication load during peak hours is inevitable. Coded caching is a promising approach to mitigate and smooth traffic during peak hours in the communication network in a way that it creates coded multicasting opportunities in addition to delivering content to users locally. However, it suffers from imposed delay resulting from coding that makes this approach infeasible for delay-sensitive contents, namely video streaming applications. So...