Masters Thesis in Information and Communication Engineering supervised by Daya Sagar Baral are:
1. IMPLEMENTATION OF TURBO CODE IN CDMA 2000 (2008)
By: Damador Kandel
For the reliable communication, channel coding is employed. Turbo code as a powerful coding technique has been widely studied and used in communication system. Turbo code is implemented in forward link of CDMA 2000. In the transmitter side, the signal is spreaded and in the receiver side, the signal is de spreaded to recover the original signal. Turbo code is analyzed in detail and comparison is between turbo code and convolution code is done.
2. PAPR REDUCTION IN OFDM SYSTEM USING PULSE SHAPING TECHNIQUE (2008)
By: Prakash Bahadur Shahi
Orthogonal-frequency-division-multiplexing (OFDM) technique allow the transmission of high data rates over broadband radio channels subject to multipath fading without the need for powerful channel equalization. However, they are very sensitive to nonlinear effects due to the high peak-to-average power ratio (PAPR) owned by their transmitted signals. Efficient technique for reducing the PAPR of OFDM signals is purposed. The reduction in PAPR of the OFDM signal is obtained through a proper selection of a pulse shaping scheme that distributes the power of each modulated symbol over the OFDM block such that the average power of OFDM signal will not be far from individual symbol power. The obtained results show that this pulse shaping scheme is an attractive solution to the PAPR problem of OFDM signals. The good improvement in PAPR given by the present technique permits the reduction of the complexity and cost of the transmitter significantly. The pulse shaping schemes also take advantage of the frequency variations of the communication channel and can provide considerable performance gain in fading-multipath channels.
3. STUDY AND SIMULATION OF MIMO (2009)
By: Amit Khanal
Over recent years the MIMO (multiple input multiple output) has become a popular technique in wireless communication. MIMO is a system with multiple transmitting and multiple receiving antennas. ZF (Zero forcing) and MMSE (Minimum mean squared error) are the linear MIMO detectors while ML (Maximum likelihood) is an optimal MIMO detector. VBLAST (Vertical-Bell Labs Layered Space Time Architecture) is a special detector designed for the MIMO system. The performance of ZF VBLAST (zero forcing VBLAST) is compared with ZF, MMSE and ML detector. The VBLAST algorithm uses iterative method to detect transmitted symbols and one transmitted symbol is detected in each iteration. Each iteration further consists of ordering, interference nulling and interference cancellation step. The reduction of the computational complexity of the ZF VBLAST receiver by reducing the number of iteration is considered. The performance of various MIMO detectors is compared in terms of block error rate (BER). For simulation Rayleigh channel model has been considered with BPSK (binary phase shift keying) modulation at transmitting end.
4. PERFORMANCE EVALUATION OF 3GPP LONG TERM EVOLUTION (2010)
By: Kamal Lamichhane
Uplink and downlink modulation techniques in long term evolution (LTE) are SCFDMA and OFDMA. SCFDMA has different subcarrier mapping techniques and hence SCFDMA can be analyzed under these different subcarrier mapping techniques. From user's perspective, high bandwidth, large throughputs, service access delay and better quality of service related parameters like paging, successful call connection rate handoff rate, call drop rate etc. are the highly attractive features of 3GPP LTE. This technology is near to 4G and having maximum data rates up to 100 Mbps in downlink and 50Mbps in uplink. Technically LTE is based on Release 7 and Release 8 specifications as prescribed by 3GPP. The reason behind high data rate is based on use of digital modulation schemes like QPSK, 16QAM and 64QAM. The modulation techniques may vary with the distance of subscriber's from the transmitting station to the mobile station as well as the noise in channel and MIMO technology with different matrix combination in uplink and downlink. Peak to average power ratio (PAPR) is highly reduced in SCFDMA in comparison with OFDMA. SCFDMA is a single carrier modulation technique and OFDMA is a multi-carrier modulation technique. This may also be one of the causes of high PAPR in OFDMA i.e. amplifier in receiver has more nonlinear characteristics for multicarrier signal amplification. Low PAPR helps to minimize the inter-symbol interference and it is also good technical solution to save the power consumption of user's terminal while communication is in uplink mode. Multipath fading, white Channel performance is analyzed in terms of symbol error rate (SER) or bit error rate (BER) in different noise conditions in LTE channel.
5. PERFORMANCE EVALUATION OF WiMAX/IEEE 802.16 PHYSICAL LAYER (2010)
By: Min Prasad Aryal
WiMAX is an eminent technology that provides broadband and IP connectivity on "last mile" scenario. Orthogonal frequency division multiple access uses adaptive modulation technique on the physical layer of WiMAX and it uses the concept of cyclic prefix that adds additional bits at the transmitter end. Then the receiver removes these additional bits in order to minimize inter symbol interference, to improve the bit error rate. The technological aspects of WiMAX standards are studied and the performance of WiMAX physical layer is analyzed in different perspectives in physical layer on the basis of bit error rate, signal to noise ratio etc. The performance is analyzed in different aspects such as with the variation of different modulation techniques, cyclic prefix, coding, channel models etc. The change in parameter is analyzed to improve the performance. It is compared with other broad band technologies such as 3G, WCDMA, HSPA, WiFi, LTE etc.
6. CAPACITY OF MIMO SYSTEMS FOR SPACIAL CHANNEL MODEL SCENARIOS (2010)
By: Dinesh Chandra Panthy
In the research process of wireless systems and in the race for the development of the new technologies, MIMO (Multiple Input, Multiple Output) is getting more attention as it uses two or more antennas at each end of a connection to send and receive data, enabling transmitter and receiver to accept signals more efficiently than with a single antenna and thus overcomes the problems and restrictions compared to the conventional system. MIMO system capacity is investigated using the Spatial Channel Model (SCM), proposed by standardization bodies (3GPP-3GPP2) for third generation systems and compared this to one of the physical geometrical model i.e., One Ring channel model and to a theoretical model i.e. independent and identically distributed (i.i.d.) model. Non line of sight (N-LOS) MIMO systems in SCM is evaluated with multipath propagation scenarios and compared with i.i.d and One-Ring channel model. The results show that capacity increase is almost linear with the number of antenna but rate of linearity is high in water filling power allocation scheme and is low in equal power allocation scheme.
The effect of mutual coupling due to closely spaced antenna elements (practical case) is also investigated. The results show that the mutual coupling lead to increase in capacity for the spacing less than approximately 0.4 times wavelength.
7. COMPARATIVE ANALYSIS OF FACE RECOGNITION METHODS (2010)
By: Manish Shrestha
Biometric systems have been researched intensively for security issues. Biometric systems can uniquely identify a particular identity. Among the biometric systems face recognition system is one of the most popular. In this approach the individuals are identified by the feature of face. Research has been in progress since 1980's with numerous applications henceforth. Currently, many face recognition applications are available commercially for criminal identification, security system, image processing etc. The goal of face recognition system is straight forward; Compare the captured images with images stored in database and recognize the faces already stored in database. A holistic Principal Component Analysis (PCA) based method, namely Eigenface method, Linear Discriminator Analysis (LDA) based method namely Fisherfaces and Independent Component Analysis (ICA) based method are studied and compared.
8. NETWORK ANALYSIS AND MANAGEMENT (2011)
By: Mukesh Kumar Keshari
Nowadays the popularity of World Wide Web is increasing rapidly. Websites are playing very crucial role to convey knowledge and information. Hence discovery of hidden information about the users is very crucial. This information can be helpful to optimize web server usage. If web logs are mined properly they can provide many useful information for the decision making process. Various monitoring software that are currently used by internet service providers for monitoring of their web server log information are analyzed. Various existing clustering algorithms are used to create the web uses pattern. Those pattern will be useful for any organization to identify the user interest and also helpful for the business intelligence process. Finally and existing algorithm is modified to create better clustering pattern. Its performance is also compared with the other existing algorithm.
9. PERFORMANCE ANALYSIS OF MIMO DETECTORS (2011)
By: Sagun Manandhar
In wireless communication, Multipath fading is constantly limiting and challenging the ability to achieve the full potential of wireless communications. Since the transmitted power is regulated and bandwidth is precious, there's need for techniques which requires no additional bandwidth and transmitted power. Diversity techniques are very powerful techniques that makes use of two or more copies of a signal and combine those signals to combat multipath fading. Among many diversity techniques known, space diversity technique is very popular due to simplicity and bandwidth efficiency. Space diversity can be implemented in both the transmitting end as well as the receiving end. The emergence of transmit diversity led to the evolution of Multiple Input Multiple Output (MIMO) systems. The decoding section is an indispensable part of MIMO systems. The Block Error Rate (BER) performance of various MIMO decoding schemes like Zero forcing (ZF), Minimum Mean Squared Error (MMSE), Maximum likelihood (ML), Linear Least Square Estimation (LLSE), and ZF-VBLAST are compared by performing various simulations. Rayleigh and Rician channel environments are used for analysis.
10. SYSTEMATIC APPROACH FOR ANALYSIS OF MIMO AND MIMI-OFDM SYSTEM (2012)
By: Kiran Chandra Dahal
The fundamentals of multiple-input single-output (MiSO) and multiple-input multiple-output (MIMO) radio communication systems with space- time codes are analyzed. A systematic method for a space-time orthogonal MIMO scheme that employs two transmitting and receiving antennas is purposed and the performance is evaluated. A MISO system and MIMO systems are analyzed using multicarrier modulation (MCM). MCM is incorporated with orthogonal frequency division multiplexing (OFDM) which implements binary phase shift keying (BPSK). The system is simulated based on the design, which tests in flat fading Rayleigh channel. The receiver design is incorporated with the maximal ratio combiner (MRC) receiving technique with perfect knowledge of channel state information (CSI). The theoretical performance of MIMO and MIMO OFDM based on bit error rate (BER) vs. signal to noise ratio (SNR) is derived for the channel and are compared with the help of simulation results.
11. DIRTY PAPER CODE DESIGN FOR MULTIUSER MIMO BROADCAST CHANNEL (2012)
By: Krishna Prasad Phelu
Dirty paper code (DPC) can be used to presubtract interference non-causally known to the transmitter and to achieve capacity as if no interference is present at all. In this thesis, DPC based on nested trellis code is designed using Trellis coded quantization/trellis coded modulation (TCQ/TCM) scheme. Rate 1/2 convolutional code is cascaded with rate 2/3 Trellis coded modulation (TCM) to form DPC. TCM code acts as channel code to protect transmitted signal against channel noise whereas cascading of both convolutional and TCM codes act as source code which implements vector quantization using Viterbi algorithm. Gain obtained from DPC can be increased using stronger source and channel codes which can be achieved by increasing number of states, because gain of both channel code and source code increases with states of encoder. DPC is the best candidate for precoding in multiuser multiple inputs multiple outputs (MU-MIMO) broadcast scenario. In MU-MIMO broadcast channel, signal transmitted to a user acts as interference for other users and this interference is non-causally available to base station because code for all users is encoded by same base station. So, in MU-MIMO broadcast channel interference to a user due to signal transmitted to another user can be nullified using DPC. DPC is implemented for MU- MIMO broadcast channel with base station containing multiple antennas and multiple receivers each equipped with single antenna.
12. DECENTRALIZED TDMA SCHEDULING FOR WIRELESS SENSOR NETWORK (2012)
By: Laxman Palikhel
Energy conservation is a major issue in Wireless Sensor Network (WSN). In order to obtain energy conservation, Time Division Multiple Access (TDMA) has been discussed as one of the potential solution. Many researchers proposed TDMA as a Media Access Control (MAC) in order to conserve energy. The main advantage to using TDMA MAC is avoidance of collision of data packets during transmission and the added facility to use sleep modes. The use of sleep mode enables switching off the radio antennas thus reducing the energy conservation. Prior to usage of TDMA MAC, scheduling of the sensor nodes, i.e. providing time slot to the sensor nodes must be performed. Efficient scheduling of transmitting time slot in a TDMA is important for low power Wireless Sensor "Network. Two decentralized scheduling algorithms "Distributed Randomized TDMA (DRAND)" and "Deterministic Distributed TDMA (DDTDMA)" are compared. In these algorithms, flowing the messages among the sensor nodes the scheduling is performed by assigning transmitting time slot to each node. So, their efficiency is analyzed based on schedule length, message complexity and convergence time to obtain scheduling. It is shown that DDTDMA is efficient algorithm than ORAND in terms of schedule length, message complexity and convergence time.
13. PERFORMANCE ANALYSIS AND ENHANCEMENT OF ADAPTIVE MODULATIONS TECHNIQUE IN WiMAX SYSTEM IEEE 802.16 PHYSICAL LAYER (2012)
By: Rajib Bikram Adhikari
WiMAX is an eminent technology that provides broadband and IP connectivity on "last mile" scenario. It offers both line of sight and non-line of sight wireless communication. Orthogonal Frequency division multiple access is used by WiMAX. Orthogonal frequency division multiple accesses use adaptive modulation technique such as Quadrature Phase Shift Keying (QPSK), Quadrature amplitude Modulation (QAM). The signal is transmitted through the channel and it is received at the receiver end. Then the receiver removes these additional bits in order to minimize the inter symbol interference, to improve the bit error rate and to reduce the power spectrum. This analysis is useful for performance evaluation of different Modulation technique used in WIMAX. Cyclic prefix is used to reduce the data errors caused by multipath reception. Here we estimate the channel to know the condition for adaptation in data rate. Channel estimation is used because amplitude and phase shift causes error in wireless channel. Then using Adaptive equalizer bit error rate for all modulation techniques are improved. Here we used equalizer with and without decision feedback to change the bit error rate. Least mean square algorithm is used for implementation of equalizer. LMS algorithm is used with decision feedback and without decision feedback. Adaptive modulation technique is used in analyzing the channel condition by investigating the received data. The modulation technique is changed by analyzing the received bits and accordingly changing the modulation technique as the code bits sent through feedback charnel.
14. PERFORMANCE ANALYSIS OF MIMO OFDN UNDER VARIOUS CHANNELS (2012)
By: Suman Gautam
With the evolution of the wireless system the demand for high speed data services have been increasing day by day, which is impossible to be achieved by the conventional serial data transmission system without trade-off between high speed data services and Quality of Service (QoS) without increasing the band width of the system. In order to overcome this problem new parallel data transmission system was proposed, which is known as Orthogonal Frequency Division Multiplexing (OFDM) system. The performance of OFDM system can be further improved by using multiple antennas at transmitting and receiving side to provide spatial diversity. A Multiple Input Multiple Output (MIMO) system takes advantage of the spatial diversity that is obtained by spatially separated antennas in a dense multipath scattering environment. OFDM and MIMO OFDM system has been analyzed under different channel conditions. Performance of OFDM with different values of Guard Interval has been evaluated with the aid of modulation schemes namely Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK). As from the various results obtained it is found that performance of OFDM system has improved significantly using cyclic prefix as guard period. Further Performance of MIMO OFDM under Additive White Gaussian Noise (AWGN), Rayleigh and Rician with different modulation schemes shows better results and improvement in terms of Bite Error Rate (BER). Also the result of the analysis suggest for the better technique in order to improve the BER characteristic of the MIMO-OFDM system.
15. Comparative Study of Spectrum Sensing Techniques in Cognitive Radio (2013)
By: Rupesh Dahi Shrestha
16. Performance Analysis of Diameter Credit Control Application (DCCA) using Diameter Protocol in Telecommunication Networks (2014)
By: Suman K. C.
17. Performance Analysis of Orthogonal-frequency-division-multiplexing (OFDM) based on Channel Estimation Technique (2014)
By: Indu Bhandari
In order to achieve the potential advantages of OFDM based systems, the channel coefficients should be estimated with minimum error. Orthogonal frequency division multiplexing (OFDM) is a method to transmit multi carrier in wireless environment, and can also be seen as a multi-carrier digital modulation or multi-carrier digital multiplexing technology. Channel estimation plays a vital role in OFDM system. The channel estimation technique that can be pilot based or blind based can be helpful to improve the performance of OFDM system. The channel estimation technique for OFDM systems based on pilot arrangements is investigated. Different algorithms for both estimating channel at pilot frequencies and interpolating the channel will be performed. The Performance comparison of all schemes by measuring bit error rate and mean square error using different modulation techniques like QPSK, and BPSK is discussed. Simulation results show the performance of different type channel estimation techniques and algorithms
18. Study On Fading Channel and Imperfect Channel Estimate On Wireless Communication (2014)
By: Manita Kharel
19. Performance Analysis of V-BLAST MIMO-OFDM Using Transmit and Receive Beamforming (2015)
By: Shankar Gangaju
Multiple input Multiple Output (MIMO) systems in conjunction with orthogonal frequency division multiplexing (OFDM) are extensively used in modern communication systems in order to improve throughput and robustness in multipath fading environments. However, for an optimal operation of these techniques, channel state information (CSI) must be available in both the transmitter and receiver sides. In this thesis to enhance the order of spatial diversity in presence of deteriorative fading correlations I proposed Least Mean Square (LMS) and Recursive Least Square (RLS) adaptive beamforming Algorithm. In receiver I used V-BLAST-ZF detection which is low complexity receiver for MIMO-OFDM. In order to confirm superiority of the proposed method in terms of computer simulations will be conducted in highly correlated fading situations with providing detailed mathematical derivations for clarifying Functionality of the proposed scheme.
20: Analysis of Dirty Paper Code (DPC) and Tomilnson-Harashima Precoding in Multiuser MIMO Broadcast Channel (2015)
By: Dev Narayan Poudel
With increasing data hungry applications, the demand for data rate is going on increasing. MIMO can provide linear capacity grow with increasing number of antennas both at transmitter and receiver side. But these days most of the devices are mobile for which multiple antennas at user side is not practically feasible. In this regard, Multiuser MIMO with single antenna receiver is feasible technology. In Multiuser MIMO (MU-MIMO) systems, precoding is essential to eliminate or minimize the multiuser interference (MUI). However, the design of a suitable precoding algorithm with good overall performance and low computational complexity at the same time is quite challenging, especially with the increase of system dimensions. In this thesis, we analyze the performance of two Precoding techniques Dirty Paper Coding and Tomilnson-Harashima Precoding to be used in next generation high speed data networks (3GPP LTE, LTE-advanced, and IEEE 802.16e Mobile WiMAX etc.). MU-MIMO has many advantages over point to point MIMO system. But due to lack of coordination between receivers in MU-MIMO the base station must precode the data to allow user to detect data independently. Base station has non-casual knowledge of the data to be transmitted to all users. To achieve capacity as if no interference is present at all, DPC is capacity achieving code for MU-MIMO broadcast scenario. Tomilnson Harashima Precoding (THP) is a prominent nonlinear processing technique employed at the transmit side and is a dual to the successive interference cancelation (SIC) detection at the receive side. Like SIC detection, the performance of THP strongly depends on the ordering of the precoded symbols.
21. Adaptive Clustering Based Hybrid VANET Accommodating Adaptive Data Rate for Performance Enhancement (2015)
By: Krishna Kumar Jha
The Vehicular Ad-hoc Network (VANET) is the backbone of today’s Intelligent Transportation System(ITS). The classes of applications for communication between vehicles range from time critical safety applications to delay tolerant Internet connectivity applications. The communication performance depends on how efficiently and timely the data delivery takes place in the network. The fast topology change and frequent disruptions due to highly mobile nodes of VANETs are the main challenges of VANETs. This thesis implements adaptive clustering of vehicles to improve the data delivery performance of the system. The design of cluster has significant impact on performance, which requires the analysis of physical layer channel condition and MAC operation at data link layer. This thesis analyzes the different propagation model along with the adaptive data rate on physical layer channel condition on real time traffic scenario. The 3G network is also deployed to send the sensitive packet without delay and to improve the system performance. The system performance is evaluated on the basis of throughput and packet delivery ratio. The throughput and packet delivery ratio are found to be better for Nakagami model than Rayleigh model. The clustering based VANET has been found to perform better than normal VANET in case of large number of nodes.The algorithm development and simulation are carried out in NS3 with real time traffic mobility scenario generated by Simulation of Urban Mobility (SUMO).
22. QoS Improvement in MANET Using Crosslayer Back Pressure Routing with Adaptive Redundancy (2016)
By: Ashutosh Ghimire
A MANET is an autonomous collection of mobile users that communicate over relatively bandwidth constrained wireless links. MANET are both self-forming and self-healing, enabling peer-level communications between mobile nodes without reliance on centralized resources or fixed infrastructure. Although, many routing protocols have been developed for MANET, widespread use of MANET have not been seen outside of experimental labs and simulation environment. Energy efficiency and delay performance of existing routing protocols are not good enough as they do not consider energy as a parameter and thus need to be optimized. In this research two existing concepts; adding Adaptive Redundancy and Crosslayer routing to improve delay and energy efficiency respectively are merged to form a new routing model. Furthermore, the proposed model of Crosslayer Back Pressure Routing with Adaptive Redundancy has been tested and compared with existing routing protocols using NS-3 and found to have the best delay and energy performance.
23. An Approach to Software Defined Network Firewall Based on Genetic Algorithm (2016)
By: Giresh Singh Kunwar
Software Defined Networking (SDN) is an emerging technology and a focused area of research in the field of computer networking. The fast changing and ever-growing demands of users evoke the dynamic networking environment which is not possible through today’s inflexible and vendor specific infrastructure of networking. The software defined approach of data networking eliminates the drawbacks of legacy network as it makes the network flexible, manageable, controllable and transparent. However, at the same time, it brings a lot of security challenges as well. This thesis demonstrates an approach to deal with various network intrusions by building a soft Firewall in Software Defined Network environment. In this research, Genetic Algorithm (GA) is implemented to build the rules for Firewall from a predefined set of network audit data. NSL-KDD training dataset is used in the training phase of Genetic Algorithm to generate best fitted rules to classify network attacks for the Firewall and these rules are then validated using NSL-KDD test dataset. It is found that the rules classified by Genetic Algorithm have 75 to 80 percent probability of detecting intrusions in the network. These rules are finally programmed in Software Defined Network controller in simple if-else format to make it work as a network Firewall.
24. Genetic Algorithm Based Approach to Image Denoising Problem (2017)
By: Sanjay Bhandari
Digital images can be degraded by noise during the process of acquisition, transmission, storage or compression. To ensure image quality, it is necessary to remove the noise in the image before the image is suitable for different processing operations. Image denoising is a process which is deployed to remove the noise through the manipulation of image data to recover quality image from the noisy image. The image denoising process should be such that the original image can be recovered without losing important features such as edges, corners and textures. One of the powerful and perspective approaches in this area is image denoising using discrete wavelet transform. This work combines genetic algorithm with wavelet based denoising methods. During the evolutionary process, wavelet based denoising methods are applied as local search operators and filtering techniques are applied as mutation operators. A set of digital images, commonly used by the scientific community as benchmarks, is contaminated by different level of additive Gaussian noise and the proposed algorithm is used to reduce the noise level in the image. The results obtained by the proposed method shows significant gain can be obtained by application of genetic algorithm to the image denoising methods. Also, the proposed method is compared against denoising methods in the literature. Its performance outperforms some methods and is competitive with several state-of-art methods for images with high levels of noise.