Conference Papers

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    Performance analysis of energy efficient asymmetric coding and modulation schemes for wireless sensor networks
    (2010) Kamath, G.M.; Shekar, Y.; Abhijith, K.G.; Sripati, U.; Kulkarni, M.
    Wireless Sensor Networks generally operate under severe energy constraints. In many cases, the networks are star connected with battery-powered nodes sensing data and sending it to a centrally-powered base station, whose energy constraints are more fore-bearing than that of the nodes. In this paper, an approach for energy efficient communication by using different channel codes on the base-station to node link (downlink) and node to base-station link (uplink) is proposed and analysed for such a network topology. This is in effect shifting complexity from the node to the base station while continuing to have the same BER performance. Also the use of more energy efficient modulation schemes are explored. ©2010 IEEE.
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    Soft decision decoding of Davydov-Tombak codes using a parity check tree
    (2010) Prashantha Kumar, H.; Sripati, U.; Rajesh Shetty, K.; Shankarananda, B.
    Davydov and Tombak have designed an excellent single error correction-double error detection (SEC-DED) code that appears to be more capable of detecting triple and quadruple errors than the conventional Hamming SEC-DED codes. These codes have been applied to memory subsystems and digital storage devices in order to achieve efficient and reliable data processing and storage. A new approach to soft decision decoding of Davydov-Tombak codes using a parity check tree associated with the Tanner graph is presented. For the AWGN channel, gains in excess of 1.6dB at reasonable bit error rates with respect to conventional hard decision decoding are demonstrated for the (40, 33), (37, 30), (35, 28) and (72, 64) Davydov-Tombak codes. ©2010 IEEE.
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    Synthesis of BCH codes for enhancing data integrity in flash memories
    (2010) Rajesh Shetty, K.; Sripati, U.; Prashantha Kumar, H.; Shankarananda, B.
    Flash memories have found extensive application for use in portable storage devices. They have been used for code storage as well as data storage. The storage density associated with these devices has increased tremendously in the past few years. This has necessitated very dense packing of data bits on the device. This gives rise to increased Raw Bit Error Rate (RBER) as a result of Inter Symbol Interference (ISI) between bits stored in adjacent cells. This necessitates the use of powerful error control codes to guarantee information integrity. With the increase in density of data storage, the raw bit error rate (RBER) associated with the storage device increases. Error Control Coding (ECC) can be used to reduce the RBER to acceptable values so that these devices can be employed to store information in applications where data corruption is unacceptable. In this paper, we describe the synthesis of BCH codes based on memory models proposed by the semiconductor industry. These codes have better error correcting capability than the codes used in current practice. ©2010 IEEE.
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    A cost-effective system for wireless power transmission
    (2010) Malani, P.; Arjun, Y.; Sripati, U.
    In recent years, the notion of transfer of power using wireless techniques has attracted many researchers. Transfer of power by wireless means has been recently demonstrated in the Massachusetts Institute of Technology (MIT). This system operates at 9.9 MHz. In this paper, we have discussed the design of a simple and cost-effective system which can enable transmission of power over short distances. We have employed the H - Bridge Inverter configuration to convert DC power to high frequency (100 kHz) which is then radiated with the help of a suitable loop antenna. It is observed that this system can also be used as a induction heating unit. In this form it can be used to replace conventional convection heating based electric stoves. ©2010 IEEE.
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    Space time coding for data transmission over power line channel
    (2010) Itagi, R.; Vittal, K.P.; Sripati, U.
    Power line channel for data transmission using digital modulation is considered to be used for sub station automation. Because of time-varying nonwhite noise being present on power line, power line channel can be modeled as multipath channel. Middleton Class-A noise model is used to simulate impulse noise on power line. The concept of space and time diversity given by Almouti, known as space time coding is used for data transmission over power line channel. Space time coding requires channel estimation, which is performed using pilot symbol data. Combination of BCH code concatenated with Convolution Turbo code employed as error correcting code ensures proper data recovery under severe channel disturbances. © 2010 IEEE.
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    Space time coding for power line communication
    (2011) Itagi, R.; Vittal, K.P.; Sripati, U.
    A study of Power Line as communication medium for broadband or narrowband application is performed in the perspective of space time coding. Simulation study to send modulated data on two phases of power line and receive signal between two phases and analyze is performed. Middleton class-A noise is used to model the noise on power line. BCH coding is used for error correction. Recovery of data, when at least one path of the channel is with medium attenuation, when simultaneously the other path of the channel goes worse is verified. The results are found to be in accordance with the principle of space time coding scheme and provide the possibility of utilizing power line as effective means of communication. © 2011 IEEE.
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    Performance analysis of fountain codes with Robust Soliton distribution for erasure channels
    (2011) Prakash, G.; Nayak, M.; Kulkarni, M.; Sripati, U.
    Fountain Codes are essentially Forward Error Correction (FEC) codes, which were developed for applications involving multicasting or for delivering large amounts of content to multiple recipients simultaneously. FEC increases the reliability of a system in a noisy environment. Luby Transform codes (LT codes) which come from a new coding family of the Fountain codes are the first realization of rateless codes which can generate potentially limitless code words from data. In this paper, a performance analysis of Fountain codes for erasure channels, which use the Robust Soliton distribution for encoding the data packets and belief propagation to decode the received packets has been carried out Results show that the overhead during decoding is around 11.2%. © 2011 IEEE.
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    A low SNR approach to substation communication using powerline for EMI reduction
    (2012) Itagi, R.L.; Vittal, K.P.; Sripati, U.
    Use of space time code concatenated with BCH (Bose Choudhari Hocquenghem) code is analyzed for performance in powerline channel with impulse noise. Performance of BCH-Space time code is worked in this paper for application of narrowband power line communication. BCH code (63, 36) with t=5 is designed and implemented in TMS320C6713 Digital Signal Processor, which is interfaced with Matlab version 7.4, where power line channel and impulse noise are simulated. These results are compared with Turbo coded OFDM scheme for powerline channel. From the results, reduction in carrier power requirement is found for BCH Space time code. Space time code has now become popular in wireless communication, as application in multipath channel. Since power line can provide different uncorrelated paths to realize multipaths effect, it is possible to apply space time code for powerline channel. In this paper, powerline is modelled as a multipath channel and impulse noise as Middleton class-A noise, on Matlab 7.4 platform. The BCH code of n=63, k=36, t=5, is designed and tested in a Digital Signal Processor (DSP) TMS320C6713. Interfacing is done using JTAG from processor to Matlab where power line, impulse noise and space time code are simulated. The performance of the system as communication system for narrowband PLC is tested for different channel and noise conditions. The results are used to find SNR requirement at a Pe (Probability of error) of the order of 10 -5 and for carrier signal strength to be within EMI (Electro Magnetic Interference) and EMC(Electro Magnetic compatibility) limits. Use of a BCH code with more better error correcting capacity, will further reduce the SNR requirement, hence will reduce carrier power. © 2012 IEEE.
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    Performance analysis of Free Space Optical links encoded using Luby Transform codes
    (2012) Prakash, G.; Kulkarni, M.; Sripati, U.; Kalyanpur, M.N.
    Free Space Optical (FSO) communication is an emerging transmission technique to transmit high data rates without using cables. This technology is expected to revolutionize the present communication system architectures both in the terrestrial and the in -space architecture. Atmospheric effects can significantly degrade the performance of FSO systems. This reduces the SNR and leads to impaired performance. FSO channels can be modeled using Gamma-Gamma, Weibull, Log-Normal, K distribution functions. Error control codes can help to mitigate atmospheric turbulence induced signal fading in free space optical communication links. Luby Transform codes belong to a class of error control codes called Fountain codes and are meant for erasure channels. In this paper, we propose encoding FSO links with Luby Transform (LT) codes for error channels. Decoding is done using belief propagation with Log Likelihood Ratio and results are obtained for different modulation schemes under different channel distributions. © 2012 IEEE.
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    Using RBF neural networks and kullback-leibler distance to classify channel models in Free Space Optics
    (2012) Prakash, G.; Kulkarni, M.; Sripati, U.
    Free Space Optical (FSO) communication systems offer a license free and cost effective access performance. FSO systems provide virtually unlimited bandwidth. Since the laser beams used in these systems are spatially confined, the links are very secure. However FSO links perform well only in clear weather conditions. Clouds, fog, aerosols, and turbulence drastically affect the performance of FSO systems and lead to fluctuations in both the intensity and phase of the received signal. FSO links can suffer from data packet corruption and erasure. Various statistical models have been proposed to describe the atmospheric turbulence channels. The choice of the appropriate model for varying level of turbulence is dependent on the atmospheric parameters. In this paper we classify the channels using Radial Basis Function Neural Networks to decide the best fit. We also use Kullback-Leibler distance as a measure between the reference distribution and the distribution of observed data. © 2012 IEEE.