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In this paper we design and simulate OFDM (Orthogonal Frequency Division Multiplexing) to study the performance of the OFDM system at higher order modulation schemes. It is very important to evaluate performance of the communication system, to test the efficiency and quality of the service it can provide. We use Matlab program to design the functionality of OFDM, then BER(Bit Error Rate) is obtained to different SNR(Signal to Noise Ratio) values, for M-array PSK and M-array QAM modulations techniques. BER is widely used as performance measurement tool, it tells number of bits destroyed while the data is travelling from source to the destination, AWGN(Additive White Gaussian Noise) is used as transmission channel.Index Terms-OFDM, Bit error rate, QAM, noise, AWGN.

Spectrum sensing is a crucial task in Cognitive Radio networks. In this network some frequency bands are allocated for primary users. Secondary user can detect the unlicensed spectrum bands which are called white spaces without disturbing the primary user. The Common control channel, Channel estimation, Joint sensing and spectrum access, the location information are the other challenges of CR networks. To reuse the spectrum, spectrum sensing is necessary and several techniques available for spectrum sensing based on band of interest [2]. In this paper, Basis Pursuit(BP) and Orthogonal Matching Pursuit(OMP) algorithms are used for signal reconstruction[1]. All the simulations are carried out using MATLAB.

Nowadays mobile users require increased coverage, quality of service and capacity in wireless communications. By using adaptive antennas at both transmitter and receiver in wireless communication, we can easily reach the required improvement. In this paper Adaptive Antenna plays a major role to improve the performance of wireless communication systems. This antenna uses advanced signal processor that modifies self generated beam pattern to strengthen the desired signal and reduce the unwanted signal. This type of antenna is called as smart antenna. This paper presents the adaptive array antenna fundamentals, direction of arrival and several digital beamforming algorithms. Performance analysis of the MUSIC algorithm with LMS is studied because these results are useful for the smart antenna system design. All the simulations are carried out using MATLAB.