Özet:
The objective of this thesis is to study whether the combination of Orthogonal Space-Time Block Coding (OSTBC) for Multiple-Input-Multiple-Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) technologies in wireless communication systems would significantly improve the transmission reliability over multi-path MIMO fading channels. A MIMO system takes its benefits from spatial diversity, which is obtained from spatially separated antennas in a dense multipath scattering environment. In order to use the additional antennas for spatial diversity, the MIMO method implements space-time block coding. There are different types of Space-Time Coding techniques, such as Alamouti Space Time Coding, Orthogonal Space-Time Coding, Quasi Orthogonal Space Time Coding, etc. The Orthogonal Space-Time Coding technique is preferable over other techniques because it provides more reliable transmission than other Space-Time Coding techniques by utilizing the same number of transmitting and receiving antennas. OFDM system is an excellent way to utilize the spectrum. In contrast to serial communication systems, OFDM is a type of parallel data transmission that promises a lower reduction in service quality with a higher data rate. In OFDM, a single channel on adjacent frequencies uses multiple sub-carriers. The MIMO (OSTBC) OFDM combination system is currently accepted for modern mobile wireless communication schemes as one of the most competitive technologies. In this thesis, an OSTBC configuration is proposed for MIMO OFDM systems in 1 × 1, 2 × 2, 3 × 3 and 4 × 4 antenna configurations. In this work, analyses of modulations such as QPSK, 16 QAM and 64 QAM on the MIMO (OSTBC) OFDM system are presented and for the analysis, Rician and Rayleigh channels are used. Their effects are studied in detail on the bit error rate for high data rates. A comparative study shows that the performance of MIMO-OFDM using OSTBC with different types of modulation improves for high order antenna configurations for channel conditions and a given data rate. Such a performance improvement inevitably leads to a lower bit error rate (BER).
