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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 40947 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Hossein Khalaj, Babak
- Abstract:
- In this dissertation we will study the problem of transmitting the information of continuous source over fading channel, especially when the transmitter does not have complete information about the channel status. In this situation we will have a tradeoff between the Quality of received packets and the Reliability in transmissions. To increase the quality of packets, for example, we should increase the quantization, and therefore, the transmission rates at the transmitter. But this will also increase the Error Probability at the receiver. It means that if the receiver gets the transmitted packet, it will have a better estimation of information source, but it is likely that error happens and receiver does not get the transmitted packet. In this situation we will use end to end Distortion as a good meter to judge the functionality of the communication system. In recent years, many papers have been published concerning this problem. The main idea in most of them is to use Layered Transmission methods. In these methods transmitter sends each packet at multiple rates instead of single rate. Although these methods have better results than single rate methods, they do not use all the opportunities in practical situations. In most of the cases, there are so many time slots that the transmitter has no new packet to transmit to the receiver, but it can use these time slots to retransmit previous information and decrease the Error Probability. One of the famous methods which convert these vacant time slots to Time Diversity is HARQ. HARQ is an example of Rateless codes which do not have a specific transmission rate. In this dissertation we will use HARQ method in the foregoing problem. To make the situation more realistic we will propose a method based on Markov Chain to control the delay of the system. We will design and analyze three different types of HARQ: simple HARQ, HARQ with time division and HARQ-BS. The last two methods are mixtures of HARQ and Layered Transmission methods
- Keywords:
- Hybrid Automatic Repeat Request (HARQ) ; Distortion Index ; Fading Channel ; Rateless Codes ; Continuous Source ; Layered Transmission
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