M Tech Dissertations

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

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Now showing 1 - 9 of 9
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    Application of compressive sensing to tow-way relay channel estimation
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2012) Nair, Rahit R.; Chakka, Vijaykumar
    An Amplify and Forward Two-Way Relay Network is one where two nodes transmit data to each other via an intermediate relay. The relay amplifies the superimposed data from both the nodes before sending it to both the nodes. A method for the estimation of channel is proposed for Amplify and Forward Two-Way Relay Network (AF-TWRN). The proposed method utilizes the fact that the channel in the case of AF-TWRN shows sparse characteristic. The sparse multipath channel is estimated in the case of AF-TWRN using compressive sensing (CS) reconstruction algorithm, namely Iterative Hard Thresholding (IHT). MSE based performance of these methods in estimating the composite AF-TWRN channel was calculated and compared to that using Compressive Sampling Matching Pursuit (CoSaMP) and Orthogonal Matching Pursuit (OMP). IHT and CoSaMP are seen to perform slightly better than OMP with lesser computational complexity than OMP. It was also shown that all three CS based estimation methods perform better than the traditional Least Squares (LS) method in the estimation of Sparse AF-TWRN channel. A low complexity detection strategy was proposed
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    Design of a novel high linearity down conversion mixer for GSM band applications
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2012) Srinaga, Nikhil N.; Gupta, Sanjeev
    Double balanced Gilbert cell mixer (GCM) is the mostly used kind of mixer as it provides conversion gain and has port to port isolation. This mixer lacks in linearity and noise figure which are to be taken care in designing mixer. Linearity is important for mixer design, to get an undistorted signal at its output. Similarly noise figure of double balanced GCM is more due to more number of components and is to be decreased to add less noise to RF signal. To increase the linearity of mixer, necessary changes are to be done at transconductance stage. The linearity of the mixer proposed is increased, by making use of an additional capacitor in parallel to gate capacitance and derivative superposition method. Derivative superposition method needs more number of transistors at transconductance stage resulting in increase of parasitic capacitance, resulting in an increase of flicker noise from indirect mechanism. This flicker noise due to parasitic capacitance is reduced by placing a tuned inductor in parallel to it
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    Design of an analog phase shifter at X-band for radar and telecom applications
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2012) Pariyani, Sandeep; Gupta, Sanjeev
    When examining a monthly bank account statement it is not only the number below the bottom line that matters. Whether that number has a minus or plus in front of it is also crucial. For many technical issues, the sign matters as well. In circuits, we can change the sign of the RF signal by means of phase shifters. Moreover, by using phase shifters, intermediate states between the signs (including complex values) can be set in circuits With the increasing use of wireless systems in GHz range, there is high demand for integrated phase shifters in phased arrays and MIMO on chip systems. An analog phase shifter has been designed and analyzed to meet the needs of Radar and Telecom applications. An X-band (8- 12 GHz) analog phase shifter using vector modulator principle is designed and analyzed using microstrip planar trans- mission line. The output of phase shifter at 0, 10, 45, 90, 135 and 180 has phase error in the range of 5. The input return loss is in the range of 5-7 dB and the output return loss is in the range of 5-15 dB. Also the insertion loss of the designed phase shifter is in the range of 5-8 dB. The designed phase shifter is then compared with commercially available Hittite's analog phase shifter
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    Low noise amplifier design at 2 GHz
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Mavani, Kausha; Gupta, Sanjeev
    Low Noise Amplifier (LNA) is one of the most important building blocks of any wireless receiver. In this an attempt has been made to study two types of LNA designs. The first design is the conventional which consists of the transistor, its biasing network and the input and output matching networks. The second design is an inductorless design which can be further customized to work over a large frequency range. The operating frequency studied in this thesis is 2GHz. A comparison has been made between the two designs and the values of gain and noise figure are satisfactory in both the designs.
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    Radiation analysis of microstrip active (amplifier) and passive (antenna) structures
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2010) Dhoot, Vivek; Gupta, Sanjeev
    Analysis of radiation from a microstrip amplifier and a newly proposed microstrip antenna is presented. Microstrip amplifier is analyzed replacing the MMIC structure by an equivalent S2P model and remaining portion being constructed with the original dimensions. A printed monopole antenna using multifractal technique is proposed. This antenna has multiband characteristics covering various wireless applications including WLAN 2.4 GHz and 5.8 GHz applications
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    Design of CDMA transmitter and three finger rake receiver
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2009) Pateriya, Bhavana; Dubey, Rahul
    As cellular wireless communication becomes a worldwide communication standard, it is important in studying how data communications happens in a cellular system. In this Thesis work CDMA transmitter and receiver have been designed including the communication channel which include effects of multipath fading and noise. Effectiveness of rake receiver have been verified for varying SNR and with varying the number of fingers. Also the functionality of each block is analyzed.
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    Design issues in direct conversion receiver
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2009) Gupta, Amit Kumar; Gupta, Sanjeev
    The wireless system is being rapidly proliferated in our life. The growing of capacity in wireless communication requires a new type of wireless communication method which does not affect current work on circuits and systems that can operate on gigahertz wide signals will undoubtedly be the wave of the future as pressures to supply multimedia services over wireless continue to build. To achieve the goal of single receiver which can act on various different standards the Direct Conversion Receiver (DCR) is the most suitable architecture. The DCR has been known for quite long years. There are number of design issues related to the implementation of DCR. This thesis presents the issues which are related to design of Direct Conversion along with the design issues related to LNA design.
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    Design of multi-standard RF front end receiver using novel low IF topology
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Pandit, Vivek Kumar; Gupta, Sanjeev
    This thesis presents the multi-standard receiver architecture and the corresponding RF front-end design supporting Bluetooth and IEEE 802.11a WLAN standards. To maximize the level of component share in the proposed multi-standard receiver, the corresponding standards is analyzed and applied to the proposed multi-standard receiver architecture. Low-IF architecture is chosen for both Bluetooth and IEEE 802.11a WLAN, respectively. The system specifications and the building block specifications is derived from the corresponding standards and verified by spreadsheet models taking into account of major design issues such as image-rejection, intercept points, noise figure and gain. The simulation results prove the validity of the system analysis and the proposed multi-standard receiver architecture.
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    Effect of channel asymmetry on reputation based cooperation mechanisms in mobile ad-hoc networks
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Vasavada, Tejas; Srivastava, Sanjay
    Enforced cooperation among MANET nodes is an active research issue. In applications, where the users have different goals and there is no central authority to control them, users may become selfish. These nodes may not forward packets sent by others and thus affect the basic functionality of the network. One proposed class of protocols to handle such scenarios is based on reputation functions. In reputation based schemes, nodes maintain reputation values of other nodes. Reputation value of a node is high for nodes that forward the received packets and low otherwise. Nodes with very low reputation values are identified as selfish nodes and isolated from network operations. In such schemes, every node has to observe whether its neighbour is forwarding packets or not. A node after sending a packet to its neighbour to forward further, increases reputation of neighbour if it overhears the same packet from the neighbour. If it does not overhear the packet, reputation of neighbour is reduced. This is the basic method to observe whether neighbour node is cooperative or not. Here basic assumption is that the channel between two neighbour nodes is always symmetric. This assumption does not hold true due to two reasons: (1) Nodes are moving. Neighbour node may have forwarded the packet but by the time it forwards, either observing node or neighbour or both might move out of each others range. (2) Even if both are in each others range, due to multipath fading, observing node may not overhear the packets forwarded by neighbour node. Thus sometimes even honest nodes may be considered selfish and isolated due to this asymmetry. This reduces throughput of honest nodes. In this thesis work we have examined the probability of channel asymmetry as a function of ratio r(of inter node distance and transmission range), for given values of relative average velocity of nodes V and Ricean parameter K. Ricean parameter K represents type of the environment i.e. obstructed or unobstructed. We have proposed an enhancement of existing reputation protocol OCEAN. In the enhanced protocol, observing node probabilistically updates reputation of neighbour when it does not overhear. This probabilistic update takes into account probability of channel asymmetry. We have tried to minimize false positives, i.e. honest nodes being detected as selfish. We have shown through simulations that false negatives, i.e. selfish nodes being detected as honest, do not increase much. We have also shown that how false positives and false negatives change as degree of dishonesty of selfish nodes change. At last, we have shown that throughput levels of honest nodes in original OCEAN protocol and modified OCEAN protocol are almost same.