Sharif Digital Repository

Network coding, as a novel technique, suggests that the intermediate nodes of a network can combine independent flows to optimize the usage of a shared communication channel. Also, distributed source coding, exploits the joint statistics of correlated information sources to reduce the volume of transmitted information. Surprisingly, it has been shown that linear network codes are able to compress correlated sources. In this project, we have focused on this problem, i.e. joint distributed source and network coding. We have two important contributions with different directions. First we give a practical design for joint coding. Second, we use an evolutionary approach to find the best placement... 

The two central topics of information theory are the compression and the transmission of data. Shannon, in his seminal work, formalized both these problems and determined their fundamental limits. Since then the main goal of coding theory has been to find practical schemes that approach these limits.Polar codes, recently invented by Arıkan, are the first practical codes that are known to achieve the capacity for a large class of channels. Their code construction is based on a phenomenon called “channel polarization”.
Since the performance of polar code degrades when the block length is small, several kinds of Reed – Solomon concatenation is considered in order to improve the... 

The coding and compression of information sources with special probability distribution is the center of concentration of researchers in this field in the last decades. In this dissertation, after a concise introduction to source coding, we focus on the universal source coding and data compression from an algorithmic and information theoretic point of view. First we introduce the fundamental concepts of source coding and data compression. Then, we analysis some algorithms on integer coding and verify their universality and asymptotically optimality. Usually statistics of information sources is not available in communication systems and storage devices, so that applying universal source... 

In most stochastic models with uncountable cardinality of sample space with non-trivial probability measures, the inherent information is infinite. The continuous-valued random variables and continuous-domain random processes are among such objects. Therefore, a fidelity criterion must be defined between the stochastic subject and its estimated version. Although there are some criteria for of stochastic continuous signals, based on quantizing the signal in both time and amplitude domains, we are going to define a criterion which is for stochastic processes in bounded time domain. Next, the criterion will be expressed in general sources perspective and the optimum rate of coding will be... 

The main problem in network information theory is how to send some sources in a network with multiple transmitters and receivers, in the presence of the noise and the interference.This problem is not solved in its general form and it needs source coding and channel coding. With the increase of users in a network, the secrecy becomes a challenging issue. The information-theoretic security is independent of the computational complexity.In this thesis, we investigate the transmission of correlated sources over information theoretic networks and study secrecy constraints in these networks. First, we study the secrecy of a one-receiver, two-eavesdropper broadcast channel with three degraded... 

Security has been considered from the information theoretic point of view in different channels such as broadcast, multiple access and relay channels. Due to application of these channels in modern networks such as wireless, sensor and Ad-hoc networks, information theoretic security arguments especially wiretapping, has major significance in these networks. With regard to necessity of confidentiality protection in modern telecommunication services, security from the information theoretic point of view should be considered as well as capacity and achievable rate region considerations in these networks. In this thesis, first, a survey of basic works in the subjects of secrecy capacity and... 

In the signal transmission cycle in a telecommunication network, there are two coding blocks, which can be realized in two ways. In the traditional way, source coding is first used to remove redundancies and compress information. Then, channel coding is used to transmit on the telecommunication channel and deal with noise and other destructive factors of the channel. In other words, source coding and channel coding are done separately. In contrast, signal transmission can be done by joint source¬channel coding. According to Shannon separation theorem and with the fulfillment of the conditions mentioned in the theorem, the method of separation of source and channel coding in a point to point... 

As one of the most important software artifacts, release reports include most essential changes of software systems in each release. These reports are useful for documenting team activities, improving communication between team members and facilitating decision makings. They are often generated manually by a team member, which can be a tedious and time-consuming task. For each release, one should go through hundreds of issue reports, changed files, source code, and other related documents to determine what has changed and why. Then they need to identify the most important and relevant changes. Therefore, automated generation of release reports can be highly desirable. Despite the... 

Polar codes were introduced by Arikan in 2009. These codes are the first family of codes that with low encoding complexity and successive cancellation decoder, can achieve the channel capacity. Polar codes, at first were implemented for channel coding, but in 2010 performance of these codes in binary and q-ary alphabet source was studied. It is shown that these codes can perform efficiently in channel coding and source coding. On the other hand, one of the most important continuous sources are Gaussian sources. Due to the importance of Gaussian sources and good performance of polar codes, we try to evaluate the performance of these codes in Gaussian sources. Note that, these codes have... 

In this thesis, we propose a new method for deriving the achievability results in quantum information theoretic problems. The calssical quan- tum decoupling lemma is an essential component in our method. Assume that each classical source is randomly binned at a finite rate. We find sufficient conditions on these rates such that the bin indices are nearly mutually independent of each other and of a quantum source Qn. Us- ing this theorem in conjunction with the calssical quantum Slepian Wolf (CQSW) result, this method suggest a new comprehensive framework for the achievability of network quantum information theoretic prob- lems. We’ve used the new method to redrive the Holevo bound, private...