Performance Evaluation of OFDM Systems Using Blind Phase Noise Compensation in the Presence of Jammer Noise

Abstract

The popularity of multimedia data services is skyrocketing. The fourth-generation (4G) wireless communication technology is based on orthogonal-frequency-division-multiplexing (OFDM), one of the most reliable multi-carrier technique. It is attributed to its large capacity accommodating more number of users, high data rate and the provision of worldwide coverage with high mobility. Despite this, OFDM is significantly influenced by phase noise due to imperfections of the oscillators. As a result, the presence of phase noise in an OFDM symbol block rotates the constellation and introduces inter-carrier-interference (ICI), which in turn causes loss of orthogonality amid the subcarriers. The deleterious effects of phase noise can be classified into common-phase-error (CPE) and ICI, and these effects get reflected in the bit-error-rate (BER) performance of the system. It is necessary to compensate for these effects of phase noise, and it is done by the usage of several techniques, which may be pilot-based or blind techniques. The blind compensation techniques are advantageous over the pilot-based techniques because they do not use pilot symbols and as a result, these are bandwidth efficient techniques. One such blind compensation technique has been taken into consideration for the purpose of research in this thesis work. This research work presents the performance evaluation of a blind algorithm used for compensating the phase noise effects in the wireless OFDM communication systems, in which the time-average of phase noise within an OFDM symbol block is calculated at the subblock level. It contributes towards the estimation of common phase error term, which is used for the excision of ICI. The main focus of presented research work is on the effects of phase noise on the performance of underlying OFDM system for the different number of subcarriers, for the different M-ary phase-shift-keying (PSK) modulation techniques, and it emphasizes on the impact of jammer noise, while using the zero-forcing (ZF) and minimum-mean-square-error (MMSE) techniques for detection. Simulation results are demonstrated to verify efficacy of the blind-phase-noise-compensation (BPNC) technique under the multipath Rayleigh fading environment, which manifest that the MMSE detector performs marginally better than ZF detector in the presence of jammer noise. However, the long OFDM symbol block length or the large number of subcarriers can prove to be helpful in combating the impact of jammer noise.