Sharif Digital Repository

Data traffic in communication network has increased steadily in recent years. Service requirements have also changed to become more complex. Moreover decrease in relative prices of computation and storage against communication encourages using more caching in these networks . Meanwhile increased use of encryption in internet has forced service providers who were willing to enter content distribution market to cooperate with content providers. But the cooperation is discouraged by willingness of both parties to hide their internal information. There are solutions proposed for interaction and information exchange between ISPs and CPs which are based on game theory. However, these solutions... 

Caching has been widely considered an efficient way of reducing and balancing the growing traffic in communications networks in recent years. In this thesis, for the first time, the stochastic requests traffic model in communication networks is considered and a performance analysis is provided based on such a realistic assumption. In addition, we introduce new comprehensive performance metrics which simultaneously take into account, the cache hit probability, load on the bottleneck links, and requests arrival rates. The main contribution of this thesis is to present a system model based on queuing theory and provide an analysis of the stability, maximum stable throughput, load on the... 

Caching is the process of storing part of popular contents near the users, which not only results in better traffic balance, but also reduces the delay of content delivery. Due to limited cache capacities and time-varying nature of contents popularity, using a proper replacement policy for cached contents during the heavy traffic hours is necessary. Many of the existing methods have ignored the dynamics of requests. Also, most of the previous works have focused on parameters other than QoS characteristics as the performance metric.We propose a cache updating policy for wireless networks considering dynamic popularity for file requests. Our model is a wireless heterogeneous network consisting... 

In recent years, concentration on optimizing transmission in networks has led to use intermediate data transmission nodes to help routing, transmitting and storing data. In other words, new network architectures are changing from end-to-end (like Transmission Control Protocol) to hop-to-hop protocols. Named Data Network (NDN) is a promising content-centric scheme for the future Internet architecture that uses names instead of addresses and each node in intended path transmits Interest/Data packet pairs for data routing and delivery. Network Coding is also a content-centric approach that is effective for reducing redundancy, increasing network throughput and improving robustness. Not so many... 

The popularity of Internet-based video services has grown dramatically in recent years, with the figure now estimated to be around 75 percent of total bandwidth consumption and it will increase to 82 percent by 2021. The growth of video services, as well as the advent of 360-degree videos and more real-world experience in it than conventional videos, have led companies such as Google, Facebook, and others to embark on this field of research and implementation to make it an epidemic. One of the major issues that will challenge the implementation of this video service on the network is the high volume of these videos that do not make it possible for everyone to use them. It is necessary to... 

Cache networks play a key role in today’s Internet. Inspired by the successful deployment of caching in content delivery networks (CDNs), pervasive caching now is a fundamental concept in storage-assisted future Internet architectures, e.g., information-centric networks (ICN), and 5G. However, despite the clear and increasing economic advantages of caching for the network operators, it does not take place efficiently due to various problems. The emergence of in-network caching has created new challenges for modeling and performance evaluation of networks. In addition, content providers (CPs), who alone have the detailed demand data required for optimal content placement, have no natural... 

Wireless communication networks are undergoing a significant transformation from coverage-driven deployment of macrocells to user-centric and cluster-based capacity-driven deployments of low-power base stations (BSs), usually at the locations of high user density. On the other hand, the increasing irregularity and randomness in the locations of nodes has led to an increased interest in the use of random spatial models along with tools from stochastic geometry and point process theory for their accurate modeling and tractable analysis. To this end, this thesis investigates clustered networks for different wireless applications. In this regards, comprehensive and tractable analytic frameworks... 

In last decades, network traffic has shifted from voice to content, which can cause network congestion. A common technique to reduce the chance of congestion during peaktraffic periods, which leads to fewer congestion, is to duplicate contents in distributed memories across the network (servers, users, routers, ...). This technique is called caching. We study a cache-aided Gaussian broadcast channel (BC), where a transmitter is connected to two users through a Gaussian BC. The transmitter has access to a server with N equal size files. Each user has a local cache memory which is filled up in the placement phase. In the delivery phase, each user requests one of the files from the transmitter... 

Future mobile networks are expected to not only bring more wireless connectivity and higher data rates, but also to support several high-quality services including low-latency, ultra-reliable, and energy-efficient communications. To support these needs, intelligent reflecting surfaces (IRSs) have recently attracted a lot of attention due to their potential for reconfiguring the wireless channel and are considered as a promising solution for future mobile generations. On the other hand, the exponential growth of network traffic, and its non-uniform distribution result in network congestion during peak-traffic times and network underutilization during off-peak times. Caching or content... 

Today, with the proliferation of smart devices and the advent of various innovative applications, there has been an exponential surge in the number of users in telecommunication networks. Consequently, the data traffic rate is escalating considerably. This has created a major predicament for wireless networks due to the limited frequency spectrum. Therefore, the conventional centralized architecture makes it difficult for the network to address these numerous simultaneous requests. This issue can be solved by designing new architectures. In a way, network information is disseminated to the network's periphery and the contents of the primary data center are provided temporarily in closer...