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In recent progress in Wireless Sensor Networks (WSNs) has been developing into one of the main attractive networking technologies, as it can be deployed without communication structures. A sensor network is composed of a number of sensor nodes which are responsible for regulation of the physical experience and transmission of the periodical results to the BS (base station). Consequently, minimize the energy consumption and extend the network lifetime are the key challenges in wireless networks. In this aspect, we proposed a hierarchical clustering method algorithm, PESCA (Position Energy Spectral Cluster Algorithm) that determine the number of clusters in a network automatically, depending on residual energy and BS distance. The idea of this clustering scheme is to modifY the /c-means algorithm and proposes new features of the network nodes .In addition, we present a distance-energy cluster structure algorithm (DECSA) based on the classic clustering algorithm LEACH. The experiments results show that the proposed algorithm presents a significant performance improvement in terms of energy and efficient clustering.

n this paper, Root-MUSIC algorithm for direction of arrival (DOA) estimation of uncorrelated signals is explored both for uniform linear and uniform circular arrays. The basic problem in Uniform Linear Arrays (ULAs) is Mutual coupling between the individual elements of the antenna array. This problem is reduced in Uniform Circular Arrays (UCAs) because of its symmetric structure. The DOA estimation of uncorrelated signals that have different power levels is simulated on a MATLAB environment. And the noise consider is white across all the array elements. The factors considered for simulation are number of number of snapshots, array elements, radius of circular array, array length, and signal to noise ratio.

Abstract:The era of entirely wireless, mobile communication is rapidly approaching.Increasingly; users are demanding versatile and convenient modes of communication along with high-speed broadband and technology in the premise of guaranteeing certain quality of communication without losing performance and efficiency. The challenges are to give users high-speed, high-performance in different channel conditions. So, Orthogonal Frequency Division multiplexing (OFDM) has been recognized as one of the most promising techniques to meet these challenges. Space Time block Coding (STBC) has drawn much attention in 4G wireless technologies just because of its decoding simplicity. This paper presents the performance evaluation of STBC-OFDM systems covering channel model and coding scheme, it includes Rayleigh fading channels by which it is observed that Bit Error Rate(BER) is reduced to achieve the high data rate.In this work, a performance criterion such as bit error rates for low SNR is analyzed. The BER for OFDM system over Rician fading channel is observed to be 0.1273.It has been reduced to 0.03919 over Rayleigh fading channel with Line of Sight (LOS) for the same Signal to noise ratio (SNR).

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