Browsing by Author "Kulkarni, Muralidhar"

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Advances in Communication, Signal Processing, VLSI, and Embedded Systems: Select Proceedings of VSPICE 2019
(2020) Kallya, Shubhakar; Kulkarni, Muralidhar; Shivaprakasha, K.S.
Analog & Digital Communication Systems
(2015) Kulkarni, Muralidhar; Husain, Farooq
Digital and Analog Communication Systems
(2012) Couch, Leon W.; Kulkarni, Muralidhar
Digital Communications
(2005) Kulkarni, Muralidhar
Energy Efficient Error Control Techniques for OFDM Systems with their Applicability to Power Line and Wireless Communication Channels
(National Institute of Technology Karnataka, Surathkal, 2014) H. M, Savitha; Kulkarni, Muralidhar
The basic idea of multi carrier modulation is to divide the transmitted bit stream into many different sub streams and send them over many different sub channels which are orthogonal under ideal propagation conditions. Orthogonal frequency division multiplexing is a discrete multi tone system. An efficient implementation of OFDM system can be carried out using inverse fast Fourier transform for modulation and fast Fourier transform for demodulation. OFDM is a popular modulation technique in almost all the recent applications in the RF domain. OFDM has emerged as a successful modulation format in major communication standards, like digital subscriber loop, wireless LAN, DVB and DAB. Worldwide Interoperability for Microwave Access and Long-Term Evolution are the two popular 4G mobile network standards, which use OFDM modulation format. One of the major disadvantages of OFDM is its sensitivity to frequency and phase noise. One of the objectives in this research work is the development of a coded OFDM system that tackles the performance degradation due to carrier frequency offset in a much efficient manner as compared to the available methods. The second objective is to develop an additive white class-A noise model for coded OFDM system so that it can be used with better bit error rate performance in power line communication systems. Besides this, a performance evaluation and determination of the performance gain in soft iterative decoders as compared to hard iterative decoders is considered. This evaluation is done in support of the efficiency of Turbo and low density parity check codes. To check the suitability of the coded systems in free space optical communication, BER performance evaluation of coded communication system has been carried out. The overall objective of this research work is to develop coded OFDM systems that perform much efficiently in terms of the BER performance. It also aims to provide the possible SNR saving in the proposed methods as compared to the available methods.
Information Theory and Coding
(2018) Kulkarni, Muralidhar; Shivaprakasha, K.S.
Metamaterial Inspired Reconfigurable antenna for Cognitive Radio applications
(National Institute of Technology Karnataka, Surathkal, 2022) Jacob, Naveen; Kulkarni, Muralidhar; K., Krishnamoorthy
The rapid development of electronics and wireless communication led to great demand for wireless devices that can operate at different standards, concurrently. These devices require low profile, compact, high gain antennas which can handle multiple functions simultaneously. Reconfigurable antennas integrated with electromagnetic metamaterial structures is a promising solution for the above requirement. A miniaturized multiband reconfigurable Artificial Magnetic Conductor (AMC) unit cell, a zero phase reflection metasurface and a phase gradient metasurface are designed to integrate with the antenna for improving the gain and achieving beam steerability. Antennas designed for Cognitive Radio (CR) services requires switching between Ultra-Wide Band (UWB) response and multiple Narrow Band (NB) responses for the purpose of “spectrum sensing” and “communicating” respectively. Focusing on this requirement a frequency reconfigurable circular monopole antenna is designed which can switch and fine tune between UWB response and several number of NB responses. Modern wireless devices that operates on different communication standards requires, change in data rate, depending upon the requirement of application. This demands the antenna to be capable of tuning its bandwidth. Focusing on this requirement a bandwidth reconfigurable antenna is designed by integrating the metamaterial structure, complementary split ring (CSRR) with the antenna. Circular polarization with switchable polarization sense of LHCP and RHCP, is also implemented in the designed antenna. Radiation pattern reconfigurability, with a good beam steering angle is also achieved for the designed antenna by integrating phase gradient metasurface. Designed antenna is fabricated and tested in an anechoic chamber. Its measured parameters are compared with existing designs in the literature to showcase the improved performance exhibited by the designed antenna.
Microwave and Radar Engineering
(2009) Kulkarni, Muralidhar
Microwave and Radar Engineering
(2015) Kulkarni, Muralidhar
Modified QUIC Protocol with Congestion Control for Improved Network Performance
(National Institute of Technology Karnataka, Surathkal, 2019) Kharat Prashant, Krishnarao; Kulkarni, Muralidhar
In a computer communication network, transport layer is responsible for reliable data delivery with guaranteed Quality of Service (QoS). Congestion control mechanism is one of the prime features of transport layer and predominantly responsible for maintaining the performance of network. The main contributions of this thesis are to modify the existing handshaking mechanism of Quick UDP Internet Connections (QUIC) protocol, called modified QUIC (ModQUIC) to reduce control overhead and Congestion Window (cwnd) size update delay. The suggested modification fine tunes the window update mechanism with Acknowledgment (ACK), that results in smooth variation in cwnd growth. Further, it regulates the network traffic which in turn helps to control congestion. In the first phase, we have suggested modification of the existing QUIC protocol called the ModQUIC protocol and its performance has been evaluated with Chromium server-client model testbed. The results and analysis are presented in comparison to QUIC and TCP in terms of performance measures like throughput and delay. Here, the performance has been tested for limited and sufficient link bandwidth in presence of loss, whereas the validation of results have been carried out with the help of linear regression model. In the result analysis, it was evident that ModQUIC achieves a throughput improvement of 35.66% and 51.93% over QUIC and TCP respectively, whereas delay is also reduced to 3% and 5% in comparison to QUIC and TCP. In the second phase, ModQUIC performance is verified in emulated environment using the Mininet for transport layer and browser network. The experimental results of ModQUIC are compared with QUIC, TCP and TCP/HTTP2 based on throughput, delay and fairness. It has been observed that ModQUIC outperforms throughput with an increased speed by minimizing transmission delay and improvised fairness. In addition, specifically for lossy link and low bandwidth, ModQUIC performance is better compared to QUIC and TCP. One of the QUIC features is inbuilt congestion control mechanism, which is responsible for maintaining streaming data. If there is no congestion, regular window size update is carried out as a step by step approach. In next phase of research work, ModQUIC protocol is investigated with CUBIC and Botitleneck Bandwidth Round-trip-propagation (BBR) congestion control mechanisms and suggested use of a decreased value for the factor β = βTCP=n for n flows, which are competing to acquire bottleneck resources, where βTCP is the decrease factor used in TCP. The Chromium server-client testbed experiment results show that the ModQUIC with BBR giver better performance in terms of throughput, delay and datarate. The result analysis actually gives an improvement of 6.8%, 19.06% and 27.9% for the ModQUIC/BBR as compared to ModQUIC/CUBIC, QUIC/BBR and QUIC/CUBIC respectively in terms of throughput. Furthermore, the delay is reduced by 8.02%, 6.56% and 14.38% over ModQUIC/CUBIC, QUIC/BBR and QUIC/CUBIC respectively. The QUIC protocol versions are updating faster and new versions of the same are available for users. In the final contribution of the research work, the performance of QUIC protocol has been tested with respect to congestion control using India’s rapidly growing Internet Service Provider (ISP); Reliance Jio 4G (JioFi) network. This experimental study investigated ModQUIC performance for congestion control mechanisms CUBIC and BBR in JioFi. The experiment is conducted using a testbed, developed with JioFi and Raspberry Pi-3 wireless router along with network emulator; Netem. Furthermore, the QUIC performance is verified with respect to Throughput and Retransmission Ratio (RTR) in which it is observed that overall ModQUIC/BBR performance is better than ModQUIC/CUBIC in the current Internet. We observed that Reliance Jio is an economical solution for the highly populated country like India, but not a contemporary solution to fulfill India’s newly launched digitization project.
Principles Of Communication
(2006) Husain, Farooq; Kulkarni, Muralidhar
Text Book on Digital Signal Processing
(2010) Kaler, R.S.; Kulkarni, Muralidhar; Gupta, Umesh