Theses and Dissertations
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Item Open Access 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, SanjeevWhen 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 shifterItem Open Access Traffic profile measurement and traffic driven network reconfiguration(Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Monga, Jasneet Kaur; Srivastava, SanjayIn multi hop ad hoc network, nodes are constrained by the power or the energy sources that are available. Efficient algorithms for saving the energy are required to manage the network in such a manner that the resources available, get properly utilized and nodes in the network do not drain out. Switching and working over idle and busy periods of a node, one can achieve this dual goal and it comes under the category of sleep scheduling. In this approach, the basic emphasis is on the traffic profiles of the network nodes which is estimated based on the network traffic flows. The traffic estimated becomes the weight of the path between the different source destination pairs available in the network and this value averaged either at the local level or the global level is needed to be reduced, hence saving the overall energy of the network. The traffic weighted paths which consume energy above the average or the threshold value become the prime candidates for the consideration. The aim is to go for shorter and lighter paths in the network which require the sleeping nodes in the proximity of heavy and longer paths to be awaken to be a part of network topology and saving the extra energy wasted on longer paths. This makes the nodes in longer paths go through a sleep state so that they can be utilized when they are required, hence making topology changes by reconfiguring the paths.Item Open Access Analysis of address allocation protocols for mobile ad hoc networks(Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Sati, Mohit; Srivastava, Sanjay; Divakaran, SrikrishnanIn almost all networks, it is necessary to have a unique identifier for each node. This identifier is used to find out route locating a particular node. So an address is must for any node for unicast communication. Addresses can be preconfigured manually or can be assigned dynamically using a server (e.g. DHCP server). Manual configuration of ad hoc network is not possible for large scale networks. And setting up a server is not possible due to lack of infrastructure in Ad Hoc Networks. So it is necessary to have a mechanism by which we can allocate addresses to the nodes dynamically without any prior setup. Lack of infrastructure and mobility of nodes makes address allocation a challenging task in MANET. We present worst case message complexity analysis of a number of proposed address allocation protocols, which can be useful for estimating upper bounds for overhead and latency involved in address allocation as well as partitioning and merging. We also show that the worst case analysis is not a useful indicator of real world performance of the protocols. Buddy approach [5] is one of the many proposed approaches for address allocation. We model DPDA (A Distributed Protocol for Dynamic Address assignment in mobile ado networks)[6], a protocol based on buddy approach, to estimate the overhead involved in address allocation. We conduct simulations in NS-2 and compare with analytical results to validate our model. We perform simplified simulations using Python script which also validates the proposed model. We also do a simulation based comparison of MANETconf (MANET configuration) [8] and DPDA[6] in term of overhead and latency in address allocation, which shows that DPDA causes lower communication overhead and latency than Manetconf.Item Open Access Dual-band and shorted microstrip patch antenna design for communication system applications(Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Rai, Karishma K.; Gupta, SanjeevDual-band and miniaturized microstrip patch antennas are in much demand due to their small size, light weight and planar configuration. In this thesis, an attempt is made to design and analyze miniaturized microstrip patch antennas, patch arrays and dual-band microstrip patch antennas. These antennas can be used in any application, over a wide frequency range of 1 GHz to 10 GHz. An array of shorted microstrip patches has been designed to operate at the desired frequency. The dual-band operation is obtained by either creating a notch on one of the radiating patch of the microstrip patch antenna or loading the radiating patch by a slot. The patch used for this dual-band operation is shorted using a shorting wall. The results of both the designs are analyzed. The study carried on, helps to find the various antenna parameters and the optimized design of an antenna array and dual-band antenna.Item Open Access Scalable routing in mobile ad hoc networks(Dhirubhai Ambani Institute of Information and Communication Technology, 2009) Patel, Brijesh; Srivastava, SanjayIn Mobile Ad Hoc Networks (MANETs), performing routing is a challenging task in presence of the varying network parameters like node mobility, traffic and network size. It is very important to analyze the scalability characteristics of the routing protocols with respect to these parameters. ZRP is considered to be one of the most scalable routing protocols due to its multiscoping and hybridization features. We propose a general, parameterized model for analyzing control overhead of ZRP. A generic probabilistic model for data traffic is also proposed which can be replaced by different traffic models. Our analytical model is validated by comparisons with simulations performed on different scenarios. In our simulation results we have observed that the optimal zone radius lies where the proactive and reactive overhead components of ZRP are approximately equal as observed in [19]. We have also observed that optimal zone radius setting is different under different network conditions. Our simulations show that as the mobility increases the optimal zone radius value decreases, and as the traffic increases the value of optimal zone radius increases. Moreover, if a node operates away from the optimal zone radius setting then it has to bear and ditional routing overhead. Our simulations show that this deviation is quite high in case of low mobility (upto 35%) than in high mobility (upto 23%).Item Open Access Analysis of address allocation protocols for mobile ad hoc networks(Dhirubhai Ambani Institute of Information and Communication Technology, 2009) Sheth, Kavan J.; Srivastava, SanjayIn almost all networks, it is necessary to have a unique identifier for each node. This identifier is used to find out route locating a particular node. So an address is must for any node for unicast communication. Addresses can be preconfigured manually or can be assigned dynamically using a server (e.g. DHCP server). Manual configuration of ad hoc network is not possible for large scale networks. And setting up a server is not possible due to lack of infrastructure in Ad Hoc Networks. So it is necessary to have a mechanism by which we can allocate addresses to the nodes dynamically without any prior setup. Lack of infrastructure and mobility of nodes makes address allocation a challenging task in MANET. We present worst case message complexity analysis of a number of proposed address allocation protocols, which can be useful for estimating upper bounds for overhead and latency involved in address allocation as well as partitioning and merging. We also show that the worst case analysis is not a useful indicator of real world performance of the protocols. Buddy approach [5] is one of the many proposed approaches for address allocation. We model DPDA (A Distributed Protocol for Dynamic Address assignment in mobile ado networks)[6], a protocol based on buddy approach, to estimate the overhead involved in address allocation. We conduct simulations in NS-2 and compare with analytical results to validate our model. We perform simplified simulations using Python script which also validates the proposed model. We also do a simulation based comparison of MANETconf (MANET configuration) [8] and DPDA[6] in term of overhead and latency in address allocation, which shows that DPDA causes lower communication overhead and latency than Manetconf.Item Open Access Low cost design of IFFT module for dolby AC-3 decoder(Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Gupta, Akshay Kumar; Dubey, RahulDolby AC-3 is a flexible audio data compression technology capable of encoding a range of audio channel formats into a low rate bit stream. AC-3 is the de facto audio standard for high-end digital consumer multimedia equipment. In this thesis work we have implemented 8 point FFT module using radix-2 algorithm. This work also shows the implementation of 128 point IFFT module using split radix algorithm.Item Open Access Nonuniform sampling and its reconstruction methodologies(Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Bhawsar, Vishal; Chakka, VijaykumarAlias-free DSP (DASP) is a methodology of processing signals digitally inside bandwidth that are wider than the famous nyquist limit of half of the sampling frequency. This topic has benefited from a strong research revival during the past few years. DASP is facilitated by suitable combination of non-uniform sampling and appropriate processing algorithms. In this thesis different stretegies to perform nonuniform sampling and its spectrum analysis are studied. We examine the problem of reconstructing a signal from non-uniform samples. A polynomial interpolation based reconstuction techniques are presented. Its performance are compared with the other previous papers on reconstruction technique on the basis of MSE criteria and Complexity of algorithm.Item Open Access Packet scheduling algorithm to improve delay bounds in HSDPA(Dhirubhai Ambani Institute of Information and Communication Technology, 2007) Pradhan, Pratik; Jotwani, Naresh D.With tremendous growth in mobile subscribers in recent past and trend of accessing packet data services in wireless networks, 3GPP has introduced an enhancement to Universal Mobile Telecommunications System (UMTS) standard known as High Speed Downlink Packet Access (HSDPA) to provide high data rate services, especially in the downlink. The main focus of HSDPA concept is to increase peak data rates, improve Quality of Service (QoS) and enhance the spectral efficiency for downlink packet data traffic. HSDPA introduces new transport channel named High Speed-Downlink Shared Channel (HS-DSCH) in downlink that is shared among the users accessing packet data services. Scheduling of these users is one of the most challenging and interesting problem because of constantly varying state of the wireless channel. The problem is even worse when users require certain level of QoS and the transmission rate supported by wireless channel is also varying. The Exponential Scheduling Algorithm, proposed in literature, is a good candidate to provide bounded delays when QoS requirements are speci¯ed in terms of maximum tolerable delays, but the investigations in this thesis show that it fails to provide delay bounds when it is still possible with some trade-o® with system throughput and sometimes not even that. The thesis proposes Delay Sense-Exponential Scheduling Algorithm, a variant of Exponential Scheduling Algorithm, to improve on the delay bounds provided by Exponential algorithm. The simulation results ensure that the new proposed algorithm improves on providing delay bounds to the Real Time (RT) services simultaneously providing comparable throughput to Non-Real Time (NRT) services. The proposed algorithm is studied under wide range of scenarios including NRT, RT and mixture of NRT and RT services.Item Open Access Buffer aware routing in interplanetary ad hoc network(Dhirubhai Ambani Institute of Information and Communication Technology, 2007) Mistry, Kamal; Srivastava, Sanjay; Lenin, R. B.Recent research has shown that existing TCP/IP protocol suit exhibits poor performance in space communication networks. To deal with communication challenges in deep space such as long propagation delay, high channel error rate, limited bandwidth etc. the architecture called Interplanetary Ad hoc Network (IPAN) is envisioned to establish a communication infrastructure in environment which allows to connect planets, natural and artificial satellites, and various mission elements such as space- crafts and rovers. The communication links in IPANs possess the properties of low bandwidth, high error rate, high latency and link unavailability for longer period of time. Nodes in such networks are resource constrained in terms of storage, energy and processing power. This work proposes a probabilistic routing protocol called \Buffer Aware Routing Protocol in Interplanetary Ad hoc Network (BARPIN)" based on the store and forward principle of Delay Tolerant Networking (DTN). Here IPAN is modeled as the network of two kinds of nodes, one having deterministic mobility patterns with greater resources and the others having random movement patterns with limited resources in terms of storage and energy. The delivery ratio performance measure of BARPIN is studied for different network conditions by changing field sizes, traffic rates, available resources on various nodes and for different source-destination pairs. Further we propose a model to estimate the minimum required buffer size of nodes for different data rates to reduce the packet loss due to buffer overflow, and justified the simulation results with analytical results.