| The future wireless mobile communication systems are required high data-rate, high reliable transmission, and spectral efficiency, which is also to be the focus research field recently. OFDM is a efficiently high speed communication technique by the orthogonality between different carriers and avoid ISI by appending a cyclic prefix to each OFDM frame. Multiple element array antennas achieve diversity gain by increase the number of antennas. OFDM combined with multiple antennas has been widely regard as a most promising elution and is efficient for future wireless transmission because of its high ability of mitigating the effects of ISI and anti multipath fading.In real transmission environment, there exists multipath fading, spatial correlation and line of sight(LOS) propagation. Different transmission model and different design purpose make different between the descriptions of the performance and capacity, so we need to integrate channel models considering all kinds of channel fading properties for MIMO-OFDM system. More domains in time, frequency and space increase the complexity of the scheme's deduce and analyse. This dissertation investigate Space-time diversity, channel estimation, adaptive subchannel allocation and adaptive power allocation for OFDM systems combined with multiple antennas. The main achievements are listed as follows:(1) Based on the MIMO-OFDM channel models, This dissertation investigate several space time coding scheme, such as STBC in a frequency selective fading channel, Differential Unitary Space-time Modulation and V-BLAST System under Correlated Rician Fading. The pairwise error probabilities of space-time diversity coding are obtained under spatial-temporal correlated Rayleigh and Rician fast fading. The performance of MIMO-OFDM system using space-time diversity coding under spatial-temporal correlation and Rician fading is discussed. The distance criterion and inner product criterion of code design under spatial-temporal correlated Rayleigh and Rician fast fading are suggested. The maximum diversity advantage, coding advantage and the change of coding advantage under correlated fast fading of system are quantitatively discussed. The SNR limitation and error limitation of differential unitary space-time modulation under Ricain fast fading are derived. Based on Gauss-Innovations model and SNR limit, we obtain the pairwise error probability of system adopting differential unitary space-time modulation which is validated through our simulation results. Symbol to symbol maximum likelihood (SSML) detection decision with minimum BER and its simulate result are presented for V-BLAST considering the spatial correlation and LOS propagation. (2) The dissertation presents subgroup channel estimation algorithm for the Subcarrier Grouping MIMO-OFDM systems. The criterion of optimal pilots design is suggested and the complexity analysis of scheme is provided. Simulation results show the performance of system based on the MSE under multipath fading channel. In the Space-Time-Frequency (STF) coded MIMO-OFDM system, dividing the subchannels into groups of less correlated subchannels and applying STF coding to group STF(GSTF) subsystems, this paper proposes novel the optimal training design for GSTF systems where one group is assigned for training and others groups are for data, and the channel estimation based on the optimal training sequence is extended into Space-Time-Frequency dimensions by considering the time dimension. The traditionally shared criteria have better performance of channel capacity by combining the pilot with the data, but it also have more spending of allocation feedback and more complexity. Theoretical analysis and numerical results show that the scheme gives distinct improvements in the channel estimates with low coding and decoding complexity.(3) In order to meet the optimal subcarrier allocation under the Subcarrier Grouping MIMO-OFDM systems, several subgroup allocation scheme that distributes the total power optimally between the training and data symbols are deduced with the acquisition of the channel state information (CSI) and its Empirical Mode Decomposition (EMD). The proposed optimal subgroup allocation scheme performs EMD on the channel fading of subcarrier sequence and then provide the definition of subgroup's envelope gene and fluctuation gene. The dissertation presents the average subcarrier allocation algorithm based on the subgroup's fluctuation gene, the power exponent subcarrier allocation algorithm based on the subgroup's envelope gene and the bitmap subcarrier allocation algorithm based on both gene. The power exponent algorithm have good ability of diversity gain and weaken spending of allocation feedback. Simulate results show the promoted algorithms have better application value under Subcarrier Grouping MIMO-OFDM systems with less spending of allocation feedback and low compute complexity.(4) The dissertation presents a optimal power allocation algorithm with the definition of subgroup's power gene under the Subcarrier Grouping MIMO-OFDM systems, which based on the foregoing subcarrier allocation and EMD. several subgroup allocation scheme that distributes the total power optimally between the training and data symbols are deduced with the acquisition of the channel state information (CSI) and its Empirical Mode Decomposition. The water-filling method is the optimal power allocation method for traditional independent parallel channels, but also have several handicap: (a)It has compute complexity with matrix's SVD, (b)It cannot provide real optimal power allocation with big granularity as antennas under the frequency selective fading channel of the broadband wireless systems, (c)It need to consider the influence of subcarrier sequence. As a substitute of water-filling under Subcarrier Grouping MIMO-OFDM systems, the subgroup's power gene allocation algorithm can solve the several difficulty. Simulate result can show the better performance of channel capacity and spectral efficiency and much more simple.
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