Performance analysis of STBC MIMO-OFDM transceiver using ICI self cancellation and cooperative diversity

Abstract

OFDM is popularly used techniques in modern broadband communication systems that are used for high data rate applications and for non-line of sight communication. OFDM is the best technology used for transmitting large data rates over smaller bandwidth. MIMO systems are used for obtaining diversity gains, array gain, spatial multiplexing and Interference reduction and avoidance. The combination of MIMO-OFDM gives the benefits of both OFDM and MIMO systems like high spectral efficiency and diversity gains. So, it can be said that MIMO in combination with OFDM is a promising technology for future wireless communication systems. In this thesis work, analysis of MIMO-OFDM communication systems using Space-Time Block Codes (STBC) under frequency selective channels have been carried out in terms of BER performance. BER analysis of STBC MIMO-OFDM using ICI self cancellation technique and cooperative diversity for both Rayleigh and Rician channels have been done. The OFDM system suffers from inter-carrier interference (ICI) due to the frequency offset that has been introduced in radio channels. Here in this thesis this problem have been answered by using ICI self Cancellation method in STBC based MIOM-OFDM system. To evaluate the performance of a STBC MIMO-OFDM system, physical layer of the same is simulated by using matlab. In the given thesis, a general STBC structure is proposed for 2x2 MIMO OFDM systems. The detection technique used is zero-forcing Equalization. Modulation technique employed in the given thesis to implement generalized STBC MIMO-OFDM system is MPSK and same has been used for STBC MIMO-OFDM with cooperative diversity. Modulation technique used for STBC MIMO-OFDM system using ISI self cancellation technique is BPSK. Rician and Rayleigh channels have been used for analysis purpose and how they affect the BER of the system is presented in the thesis. The improvement of 7dB in SNR at BER of 10-2.5 has been achieved for FFT based STBC MIMO-OFDM with cooperative diversity as compared to STBC MIMO-OFDM system without cooperative diversity. The proposed system with CFO of 0.3 has achieved an improvement of 3dB at BER of 10-3.7 as compared to the system having no ICI self cancellation. If the normalized CFO is 0.15 then there is an improvement of 3dB at BER of 10-3 has been achieved for said system.