Abstract-A comparative analysis of transmit diversity and beamforming for linear and circular antenna arrays in a wireless communications system is presented. The objective is to examine the effect of random perturbations, angular power distributions on transmit diversity and beamforming system. The perturbations are modeled as additive random errors, following complex Gaussian multivariate distribution, to the antenna array steering vectors. Using outage probability, probability of error, and dynamic range of transmitter power as performance measures, we have shown significant effects of array perturbations on the two systems under spatially correlated Rayleigh fading channel. We also examine the effect of angular power distributions (uniform, truncated Gaussian, and truncated Laplacian), which corresponds to different propagation scenario, on the performance of the two systems. Results show that the central angle-of-arrival can Corresponding author: A. W. Umrani (waheed.umrani@faculty.muet.edu.pk). 384Umrani, Guan, and Umrani have significant impact on system performance. And the transmit diversity system with truncated Laplacian distribution performs better as compared to other power distributions, and linear array is a preferable configuration for transmit diversity system. We conclude that array perturbations must not be neglected in the design of transmit diversity and beamforming systems.

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Carrier frequency offset CFO is one of major issues effecting performance of Orthogonal Frequency Division Multiplexing OFDM based systems. It is basically caused due to oscillator instability and Doppler shift introduced in the channel. It seriously degrades the system performance. This problem becomes even worse in uplink case because of random nature of users, since each user experiences different offset. Single Carrier FDMA is also an OFDM based system which is actually DFT based OFDM. Long Term Evolution LTE uses SC-FDMA instead of OFDM in uplink due to problem of Peak to Average Power Ratio (PAPR) as mobile handsets have limited battery power. In this research work, we focus on analyzing effect of CFO on the performance of LTE uplink system. The simulation results in terms of constellation diagrams and Bit Error Rate graphs show that system performance is seriously degraded due to carrier offset and suppression techniques have to be employed in order to save the integrity of user data.