M Tech Dissertations

Permanent URI for this collectionhttp://drsr.daiict.ac.in/handle/123456789/3

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Subject: search.filters.subject.Optical communications

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    Investigation on spatial arrangement of transceiver arrays in free space optical communication system
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2013) Panchratna, Digvijay; Ghosh, Anjan
    Free space optical communication (FSO) is a line of sight communication that uses lasers (as transmitter) and photo detectors (as receiver) to provide communication between two points. FSO have come about in need for greater bandwidth and improved reliable communication system. As optical frequency ranges is in terahertz i.e. from 1012 to 1016 Hz, so FSO system offers huge bandwidth and hence increased data transmitting capabilities. For an atmospheric channel the characteristics of channel are not in our control, so the performance of a FSO system is degraded by atmospheric effects. Fog, smoke, rain, snow, dust particles etc. are responsible for attenuation of the transmitted laser beam. But the main factor that is responsible for fading of the signal is the scintillation effect. Scintillation causes fluctuations in both intensity and the phase of the received signal, impairing the link performance. SIMO (Single input multiple output) and MIMO (Multiple input multiple output) systems are commonly deployed in order to combat the fading due to scintillation. But for a SIMO free space optical communication link the number of detectors to be used to deliver the maximum SNR and their position is still unknown. The curiosity of our work lies in designing the receiver array i.e. the number of detectors to be used to deliver the maximum SNR and their arrangements. In our approach, we used the concept of power with misalignment and spatial arrangement methods to come up with the problem statement. In this thesis, we have proposed two methods: 1. Deterministic method and 2. the Monte Carlo method, to find out the number of detectors and their arrangements for maximum SNR. Considering the weak turbulence regime we have modelled the channel to be log-normally distributed. In our work we have analyzed the link for both the cases i.e. with and without scintillation in order to correlate the effect on results. Novelty of our work lies in methods of arrangement i.e. the manual arrangement method and Monte Carlo method which provide us a better way to analyze the problem.
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    FIR filter for high speed 60 GHz wireless communications.
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2013) Dholariya, Tarun; Sen, Subhajit
    In this thesis report the design and implementation of the FIR filter at 5 GS/s presented. IEEE 802.15.3c standard declared unlicensed band from 57 to 66 GHz. This 60 GHz wireless communication transmitter uses interpolator filter part of this works at 5 GS/s. In this report 6 order 5 GS/s FIR filter implementation is described. In 180nm technology speed requirement cannot be achieved. Using the 45 nm technology this FIR filter is implemented and tested. The FIR filter structure is designed in bit pipelined structure. The key part are CPL adder and TSPC Flip-Flop. These adder and FF enabled very high frequency operation at 7.35 GHz. This led to implementation of 5 GS/s FIR filter using power of 2 coefficients.
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    Optical wireless sensor network design for a conducting chamber
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Borkar, Abhishek; Ranjan, Prabhat
    Now a day’s majority of the wireless sensor networks (WSNs) are based on Radio Frequency (RF) communication technology. But RF when used in an environment like that of metallic, conducting chamber exhibits large amount of interference due to multipath effects which degrades the performance of the sensor network. Infrared (IR) communication technology can be used in sensor networks which is capable of overcoming the drawbacks exhibited by RF. Suitable IR link can provide high efficiency and mobility. A wireless sensor network has to be deployed inside a metallic chamber

    known as Tokamak, used to produce controlled nuclear fusion. The sensor network

    should be capable of capturing images and monitoring environmental parameters viz.

    temperature and light intensity inside the chamber and transmitting the data outside.

    One such design of sensor network based on IR communication technology has been

    presented in this thesis. A design of sensor node with a camera, temperature sensor, light intensity sensor and IR transceiver interfaces is presented. Also a design of an optical gateway to transmit the data outside the metallic chamber is presented.

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    Routing and wavelength assignment in DWDM networks
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2005) Gupta, Dharmendra; Roy, Anil K.
    All-Optical Networks employing Dense Wavelength Division Multiplexing (DWDM) are believed to be the next generation networks that can meet the ever-increasing demand for bandwidth of the end users. The problem of Routing and Wavelength Assignment (RWA) has been receiving a lot of attention recently due to its application to optical networks. Optimal Routing and Wavelength Assignment can significantly increase the efficiency of wavelength-routed all-optical networks. This thesis presents some new heuristics for wavelength assignment and converter placement in mesh topologies. Our heuristics try to assign the wavelengths in an efficient manner those results in very low blocking probability. We propose novel static and dynamic assignment schemes that outperform past assignment schemes reported in the literature, even when converters are used. The proposed on-line scheme called Round-Robin assignment outperforms previously proposed strategies such as first-fit and random assignment schemes. The performance improvement obtained with the proposed static assignments is very significant when compared with the dynamic schemes. We designed and developed a simulator in Matlab6.5 that supports the 2D mesh topology with DWDM as well as random topology generation. We ran extensive simulations and compared our heuristics with those reported in the literature. We have examined converter placement in mesh topologies and proposed that placing converters at the center yields better results than uniform placement when dimension order routing is employed. We introduced a new concept called wavelength assignment with second trial that results in extremely low blocking probabilities when compared to schemes based on a single trial. Our proposed schemes are simple to implement and do not add to the cost. Thus we conclude that wavelength assignment plays more significant role in affecting the blocking probability than wavelength converters. The algorithm yields significant improvements in terms of the request blocking probability over traditional techniques. Also we have observed from simulated results that by using even limited conversion of degree two is sufficient to achieve performance of full conversion. We have achieved this performance by using our better heuristic technique of establishing light paths.