الفهرس | Only 14 pages are availabe for public view |
Abstract Multiple Input Multiple Output - Orthogonal Frequency Division Multiplexing (MIMO - OFDM) technology becomes a new promising technique for future wireless communication systems. The idea behind MIMO is that the signals on the multiple transmit antennas at one end and multiple receive antennas at the other end are combined in such a way that the quality or the capacity is improved. On the other hand, OFDM divides the allowed channel bandwidth into sub-channels with narrower bandwidth. OFDM provides also efficient usage of spectrum due to orthogonal carriers, simple equalization and easy implementation. MIMO-OFDM system, like any wireless communication systems, must know the channel at the receiver side to recover the transmitted data again; this can be achieved by using a channel e timator. This thesis demonstrates the main characteristics of any wireless communication channels, different propagation models and various statistical distributions for multipath channel. OFDM basic are illustrated and MATLAB simulations have been conducted to evaluate the performance of OFDM ystem with perfect channel state information at the receiver side only. The analysis and simulation of MIMO system with different Space Time Block Code (STBC) techniques and Layered Space Time (LST) coding are demonstrated. For space time block code, different orthogonal design codes are presented and the performance of Maximum Likelihood (ML) receiver is evaluated through simulation. .. The layered space time codes involve many architecture for receivers including Zero Forcing (ZF) Minimum Mean Square Error (MMSE) and successive cancellation receiver like QR decomposition, VBLAST/ZF and V-BLASTIMMSE.The analysis and simulation of MIMO-OFDM wireless communication systems are demonstrated using different channel estimators including Least Square (LS) and Maximum A Posteriori (MAP) in multiplexing. New algorithms for decoding of Alamouti coded OFDM system over time varying channel are proposed by considering the channel is changed over two successive time periods, over Alamouti symbol, instead of assuming the channel is unchangeable (static) over Alamouti symbol as stated in the literature. The simulation is done for the new AJamouti coded OFDM decoding algorithms with different channel estimators including Least Square (LS) and Maximum A Posteriori (MAP) and prove superior to the other decoding algorithms. Key words: Multiple Input Multiple Output (MIMO), Orthogonal Frequency Division Multiplexing (OFDM) , Space Time Block Code (STBC), Layered Space Time (LST), Zero Forcing (ZF), Minimum Mean Square Error (MMSE) , Maximum Likelihood (ML), Vertical Bell Laboratory Layered Space Time (V-BLAST), QR decomposition, Least Square (LS), Maximum A Posteriori (MAP), channel estimation, Alamouti coded OFDM. |