Mimo-ofdm Transmit Signal Design And Detection Algorithm

MIMO is known as a big breakthrough in smart antenna techniques of wireless mobile communication areas. It can enhance spectral efficiency several times without increasing bandwidth. The combination of MIMO and OFDM is of the key techniques of 4G for its higher spectral efficiency and the ability to combat multi-path fading.Although MIMO and OFDM have achieved great developments during the past years, there still remain many problems unsolved. This dissertation tracks the most recent direction of MIMO-OFDM systems studies and makes a thorough research on the key technique and algorithms of the transmitter signal design as well as detection algorithms at the receiver. In this dissertation, a full and detailed instruction of MIMO-OFDM signal detection algorithms is given together with the computer simulation results. Besides, the lattice theory and basis reduction are introduced in MIMO-OFDM signal detection to get better performance. Three MIMO-OFDM transmitter signal designs are defined and well described in this dissertation, from the intention to the specific parameter configuration. The performances of the schemes are tested under different channel environments.Chapter 1 gives an introduction of MIMO signal model and the principles of OFDM techniques. The most recent studies and the key techniques are summarized with emphasis on spatial processing. The significance of transmitter signal design and the detection algorithms in MIMO-OFDM systems are made clear.Chapter 2 introduces a universal MIMO-OFDM signal model. Based on this model, a full introduction of all kinds of signal detection algorithms is given. The Lattice Theory is introduced and formed a new MIMO-OFDM system on Lattice space. With LLL basis reduction applied on this model, the detection algorithms are optimized. At the end, the .detection performance is given.Chapter 3 investigates a MIMO-OFDM transmitter signal design scheme based on spatial multiplexing named V-BLAST MIMO-OFDM. Using MMSE SIC algorithms and Turbo detection, the system performance is near to Shanno band.Chapter 4 investigates two kinds of MIMO-OFDM transmitter signal design schemes which named SFBC/V-BLAST MIMO-OFDM and SFBC/V-BLAST MIMO-OFDM respectively. Simulation results and analysis indicate that the latter can combat multi-path fading and fast fading at the same time.Chapter 5 summarizes this dissertation and gives the future research direction and the next step of work for signal design and detection algorithms.In this dissertation, the detection algorithms of MIMO systems are introduced in MIMO-OFDM system with the performance tested by compter simulation. LLL basis reduction is used to optimize the BER performance of the hard decision output detection algorithms. Besides, the transmitter signal design of MIMO-OFDM systems is studied. Computer simulation results indicate that the hybrid STBC/V-BLAST MIMO-OFDM system can combat multi-path fading and fast fading at the same time.