Diverse methods that have been proposed to model Rayleigh fading channels will be explored in this tutorial. Preliminary concepts related to wireless communications channel modeling are identified before introducing the models. The first model presented is the finite state Markov channel model which is based on the side information given by the received signal to noise ratio. The Markovian validity of the model is described along with the adequate conditions under which such validity holds. The relationships between the model and modulation schemes, error control protocols and channel coding are also described. Additionally hidden Markov models proposed to model Rayleigh fading channels are also studied along with their validity assumptions. 1.

Abstract—Data loss in wireless sensing applications is inevitable and while there have been many attempts at coping with this issue, recent developments in the area of Compressive Sensing (CS) provide a new and attractive perspective. Since many physical signals of interest are known to be sparse or compressible, employing CS, not only compresses the data and reduces effective transmission rate, but also improves the robustness of the system to channel erasures. This is possible because reconstruction algorithms for compressively sampled signals are not hampered by the stochastic nature of wireless link disturbances, which has traditionally plagued attempts at proactively handling the effects of these errors. In this paper, we propose that if CS is employed for source compression, then CS can further be exploited as an application layer erasure coding strategy for recovering missing data. We show that CS erasure encoding (CSEC) with random sampling is efficient for handling missing data in erasure channels, paralleling the performance of BCH codes, with the added benefit of graceful degradation of the reconstruction error even when the amount of missing data far exceeds the designed redundancy. Further, since CSEC is equivalent to nominal oversampling in the incoherent measurement basis, it is computationally cheaper than conventional erasure coding. We support our proposal through extensive performance studies. Keywords-erasure coding; compressive sensing. I.

In this work we find the capacity of a compound finite-state channel with time-invariant deterministic feedback. The model we consider involves the use of fixed length block codes. Our achievability result includes a proof of the existence of a universal decoder for the family of finite-state channels with feedback. As a consequence of our capacity result, we show that feedback does not increase the capacity of the compound Gilbert-Elliot channel. Additionally, we show that for a stationary and uniformly ergodic Markovian channel, if the compound channel capacity is zero without feedback then it is zero with feedback. Finally, we use our result on the finite-state channel to show that the feedback capacity of the memoryless compound channel is given by infθ maxQX I(X; Y |θ). Index Terms compound channel, feedback capacity, finite state channel, directed information, causal conditioning probability, Gilbert-Elliot channel, universal decoder, code-trees, types of code-trees, Sanov’s theorem, Pinsker’s inequality I.

Abstract—According to the discovery of available and suitable audiovisual services over IP, researches on the Quality of Service (QoS) for various multimedia application services are required. This paper presents evaluation of speech quality applying improved Packet Loss Concealment (PLC) algorithms with an end-to-end bidirectional transmission control scheme. We propose real-time transmission control scheme to perform better quality monitoring of VoIP service. In order to evaluate the newly proposed RTCP-XR scheme for VoIP services, we measure in real-time the quality degree of the received speech signal while applying our improved Packet Loss Concealment (PLC) algorithms in G.711 and G.729A codecs using an implemented Session Initiation Protocol (SIP)based SoftPhone and a 1-port gateway systems. Overall, for the evaluation with scientific exactitude of speech quality applied our PLC algorithms we examine with made phone-calls through the heterogeneous network systems. The experimental results confirm the applied PLC algorithms for improvement of speech quality over IP in real environments with the QoSfactor transmission control mechanism.

English: This paper presents a joint source and channel rate allocation algorithm for video transmission over erasure channels. The approach relies on unequal error protection (UEP) of the video stream, in order to minimize the received signal distortion. It takes into account both the frames and the channel characteristics. The loss behavior is approximated by a two states Markov model. The algorithm is incorporated in a H.263 version 2 compliant encoder. The encoder supports in addition a TCP-compatible congestion control mechanism and adapts the coding mode of each macro-block to the network loss behavior. Rate-distortion models are introduced in order to reduce the computational cost. A new payload format is also described for the transport of the streams over RTP. The overall approach, compared against equal error protection and against FEC-forward error correction- adapted to the channel only, leads to improved PSNR performances, with a more stable video quality.

This thesis addresses the problems of signal processing for image communication and restoration. Significant attention is devoted to developing novel stochastic models for images, investigating the information theoretic performance bounds for them, and designing e#cient learning and inference methods for the proposed models. Unlike the commonly accepted approach in which the design of communication systems is performed by first compressing the data into binary representation and then channel coding it to recover from transmission errors, this thesis advocates the joint source-channel coding solution to the problem. The joint approach potentially leads to significant performance gains in emerging multiuser communication scenarios like digital audio and video broadcast (DAB and DVB) and multicast over wireless and wireline networks, multimedia communication in heterogeneous environments, and situations with uncertainty and fluctuations in the data source or channel parameters as is typic...

Data loss in wireless sensor systems is inevitable, either due to exogenous (such as transmission medium impediments) or endogenous (such as faulty sensors) causes. While there have been many attempts at coping with this issue, recent developments

Abstract. It is important to develop intuitive and tractable generative models to simulate the topological and temporal dynamics of the blogosphere because these models provide insights about its structural evolution. In such generative models, independent instances of individual bloggers are initiated and these instances interact with each other to simulate the evolution of the blogosphere. Existing generative models of the blogosphere have certain limitations: (1) they do not simultaneously consider the topological and temporal properties, or (2) they utilize the global information about the blogosphere that is typically not available. In this paper, we propose a novel generative model for the blogosphere based on the random walk process that simultaneously considers both the topological and temporal properties and does not utilize the global information about the blogosphere. The results of our experiments show that the proposed random walk based model successfully captures the scale-free nature of both topological and temporal dynamics of the blogosphere.

With shrinking feature size and growing integration density in the Deep Sub-Micron technologies, the global buses are fast becoming the “weakest-links ” in VLSI design. They have large delays and are error-prone. Especially, in systemon-chip (SoC) designs, where parallel interconnects run over large distances, the effects of crosstalk are detrimental to the overall system performance due to the large delays and un-reliability involved. This paper presents an information theoretic approach to address delay and reliability in long interconnects. A framework to calculate the capacity of a physical wire is laid out herein. The results for 8-bit wide buses of varying lengths in 0.1µm technology are also presented. The wires are modeled based on their calculated parasitic (R,L,C) values and the coupling (C,L) parameters. Using this model, results are obtained for the data transfer capacity of long interconnects. It is seen that for wide buses, the signal delay distribution has a long tail, meaning that most signals arrive at the output much faster than the worst case delay. Using communication-theory, these “good ” signals arriving early can be used to predict/correct the “few ” signals arriving late. Further, results show that for every bus configuration, there exists an optimal frequency of transmission that will result in the maximum data transfer rate. Also, this optimal frequency is higher than the pessimistic worst case delay based clock design. 1.