Analysis of carrier interferometry OFDM based satellite communication system

Abstract

Earth to space satellite communication channel is exposed to many impairments, including scattering effect, free space path loss, rain, cloud, water vapor, scintillation, antenna misalignment, and fading effects. Moreover, orthogonal frequency division multiplexing (OFDM) based satellite systems suffer from a high peak to average power ratio (PAPR). The high PAPR in the OFDM system causes nonlinear distortion in the transmitter's high power amplifier section. To overcome PAPR effects, several techniques such as block scaling, nonlinear companding, tone reservation, and others have some limitations and implementation complexity. Hence, the potential for CI-OFDM (Carrier Interferometry Orthogonal Frequency Division Multiplexing) is being considered for the Earth to space satellite communication links. Therein the data are modulated by QAM method, then Cyclic Prefix is added. After IFFT operation the signal is spread by the Carrier Interferometry (CI) codes over multiple sub-carriers and propagates through the Earth to space satellite communication channel. The spreading in the frequency domain achieved by the spreading codes is exploited to reject the phase noise and also reduces the peak to average power ratio (PAPR). Besides the CI-OFDM technique has major advantages of low complexity in hardware implementation and good bit error rate (BER) performance. However, there is little work on the performance analysis of satellite systems using CI-OFDM. This thesis considers the joint presence of several channel impairments for CI-OFDM based satellite communication systems. Moreover, the theoretical expression for the bit error rate (BER) of CI-OFDM system is analyzed considering the joint presence of several channel impairments in Rayleigh fading channel. Simulations are performed over additive white Gaussian Noise channel and Rayleigh fading channel. The results verify the effectiveness of theoretical analysis and demonstrates that the CI-OFDM system reduces high PAPR significantly compared with conventional OFDM system. Results also show that satisfactory BER performances were achieved by our design.