iosr-JECE   Volume-3 ~ Issue-2

Abstract: Orthogonal frequency division multiplexing (OFDM) is a form of multicarrier modulation technique with high spectral efficiency and immunity to interference. Despite of many advantages the main disadvantage of OFDM is that the time domain of OFDM signal which is a sum of subcarrier sinusoids leads to high Peak-to- Average power ratio (PAPR). A simple technique used to reduce the PAPR of OFDM signals is to clip the signal to a maximum allowed value, at the cost of bit error rate (BER) degradation and out-of-band radiation. The other method is Selective mapping method (SLM) technique which is a probabilistic technique for PAPR reduction with aim of reducing the occurrence of peaks in a signal. In this project partial transmit (PTS) scheme along with the threshold technique has been simulated using Matlab and the simulation results shows that the technique performs better. To compare the results SLM and clipping methods are also simulated.
Index Terms: Bit Error Rate (BER) Degradation, Inverse Discrete Fourier Transform (IDFT), Inverse Fast Fourier Transform (IFFT), Orthogonal Frequency Division Multiplexing (OFDM)), Partial Transmit Scheme
(PTS), Peak-to-Average power ratio (PAPR) and Selective Mapping Method (SLM).

Abstract: In this paper, teletraffic data were collected from Airtel Nigeria Ltd. for a period of 18 months. Frequencies of occurrence of congestion in the network were derived from the teletraffic data using the Nigerian Communications Commission (NCC) benchmark. The dominant causes of congestion in the network were identified from the data and their value of occurrence was seen to be random in nature. A Poisson probability distribution model was therefore implemented for the prediction of congestion in the network. The identified four dominant causes of congestion and their percentage relative weights based on frequency of occurrence were: (i) X1: Faulty System (50.63%); (ii) X2: Faulty Trunk(s) (29.11%); (iii) X3: Power Failure (16.46%) and (iv) X4: Cable Cut (03.80%). MATLAB (M-file Data Acquisition Toolbox) programming environment was used to write a software program in C++ language that simulated the four dominant causes of congestion. Pearson Product Moment Correlation Coefficient formula was used to test the relationship between the measured and simulated congestion. The value r = 0.7487 was the correlation coefficient obtained between the measured and simulated results. This shows that the model is reasonably reliable.
Key words: Airtel, Congestion, Mobile network, Poisson, Probability.

Abstract: An Ad-hoc network is a dynamically changing network of mobile nodes that communicate without the support of a fixed network. Due to lack of centralized control, secured communication in mobile Ad-hoc network is important matter due to dynamic nature of the network topology. MANETs is affected by new security problems in addition to the problems of regular networks. In this paper, we introduce an efficient security AODV algorithm to enhance the data security in the network. To generate the private key ECDSA algorithm is used. Simulation result shows that our protocol gives better performance than the previous one.
Key words: AODV, ECDSA algorithm, MANET

Abstract: In this paper, we present the principles of a low-cost Internet-based data processing system. The main h e a r t of the system is an embedded hardware (ARM 9) running with a Linux OS. The embedded device communicates through General Packet Radio Service (GPRS) module, which makes it accessible from anywhere in the world. The GPRS module provides a bidirectional real-time data transfer between the server and client. The proposed system will provide no need for server software and maintenance
Key words: ARM, GPRS, GSM, FTP Server ,Data-acquisition, embedded system, interaction, Internet, Linux, real time.

Abstract: In this paper, we present a robust and adaptive forward error correction technique for high end Audio-Video Streaming solutions. This solution targets all kinds of network loss conditions and can be used in any embedded platforms. This technique uses optimum solution for packet loss recovery that involves switching between adaptive FEC based packet loss recovery and retransmission management. Whenever network loss increases the permissible limit of adaptive FEC loss recovery, then it switches to re-transmission of media. Adaptive FEC based packet loss recovery works on best of adaptive matrix size selection, loss recovery method selection (on-the-fly or store and compute) and FEC codec selection (Parity 1D, 2D, Raptor, Read Solomon and Hamming etc.) This technique also incorporates support for embedded systems which do not have much computation power. For such embedded systems, the adaptive FEC recovery technique switches to fixed matrix of having store and save approach for single and burst packet loss recovery. This technique provides inter-operability w.r.t FEC codec selection which also takes care of embedded system capability
Key words: Adaptive FEC, Adaptive matrix size, FEC coding (Parity 1D, 2D, Raptor, read-soloman, hamming etc.), , FEC SDP negotiation, packet loss calculation techniques

Abstract:In the recent years, development of a non-destructive and non-contacting type moisture measurement system has attracted considerable interest. Because of their inherent nature of being nondestructive, ability to travel through non-conductive medium and having deep penetrative properties, Microwaves have been the traditional choice in this kind of research. This paper is a comprehensive review of Microwave Based Measurement System used for grains and pulses. In this paper, moisture measurement and calibration techniques for the system are presented. The objective of the paper is to provide the readers a broad perspective of the various techniques.
Key words: Bulk density, Complex Permittivity, Moisture Measurement, Temperature Compensation