Study On Scheduling Multi-Elements Optimal Algorithms For MIMO Systems

MIMO (Multiple-Input Multiple-Output) technique utilizing multiple antennas to realize multiple transmissions and multiple receiving can exploit space resource adequately and can improve channel capacity without any loss in bandwidth and transmitting power. So it can meet the need of high data transmission in future wireless communications. Multi-antenna systems, such as smart antenna and space-time code, are well-known as the best choice to meet above targets. Beamforming comes from smart antenna with strengthening desired signal and suppressing inter-users interference as its typical technical superiority. It is also the base to realize SDMA (Space Division Multiple Access). STBC (Space Time Block Code) is the main method to realize MIMO diversity, and it is good at mitigating the influence of wireless multipath fading. In view of development trend, the combination of beamforming and STBC will adequately exert the advantage of multi-antenna systems and result in enhancing the system performance significantly. Antenna selection is low-cost and low-complexity alternative to capture many advantages of MIMO systems. It becomes very import for wireless communications because of its significance in theory analysis and applications.Aiming at MIMO system transmit/receive antenna elements, several scheduling elements optimal algorithms are designed and studied, and logical select antennas algorithms is proposed for low-cost and low-complexity based on array signal processing theory in this dissertation. Then these methods are verified by theoretical analysis and computer simulations. The primary contributions included in this dissertation can be summarized as follow:1. A novel selective receiver switching scheme combined with beamforming is proposed for making arbitrary complex quasi orthogonal STBC matrix achieve full transmission as well as full diversity. An efficient selective receiver switching scheme is proposed for STBC with full code and non-orthogonal design. In the proposed scheme with the aid of beamforming, the scheme divides the received signals into two groups according to the encoded matrix. By this way, it can eliminate the interference from the neighboring signals almost by half. The simulation results with the example of matrix demonstrate that the proposed scheme can provide the improved performance and more transmit diversity. On the other hand, because of the reduced interference, not only the processing complexity at the decoder can be reduced but also it have a stable performance independent of DOA and angular spread. Finally, based on Maximal ratio combining (MRC) techniques, dissertation use the probability density function (PDF) of the square of the maximum singular value of the channel matrix to obtain exact closed-form expressions for BER of the coherent reception of M-PAM and M-QAM. It has the conclusion from analysis result that how to scheduling antenna makes the performance better.2. The MIMO system has radio frequency (RF) the same as antennas. Electronic elements of RF include power amplifier, analog to digital conversion, digital to analog conversion and transducer are very expensive. Transmit antenna selection and equal-gain transmission systems are investigated. The algorithm of calculating the minimum number of transmit antennas based on average SNR is obtained. Since the system is not entirely proportional to the number of RF chains, the algorithm of determining optimal number of RF chains is brought forward. A low complexity approach to receive antenna selection for capacity maximization and error rate minimization, based on the theory of convex optimization. Then, we describe a new scheme for approximately solving this problem. It gives a subset selection as well as a bound on the best performance that can be achieved by any selection of antennas. Finally, antenna subarray weight groups are allocated to a linear combination of the responses of a subset of the available all antenna elements, which maximizes the effective channel capacity.3. Two multiuser schemes which have the same frequency, time slot and channel are proposed for MIMO systems. The impulse response of the channel between the transmit array and receive array must be independent in order to make space time code get full order diversity gain. The transmitter performs eigenvalue-decomposition on the spatial covariance matrix and utilizes the obtained eigenvectors as weighting vectors to form orthogonal eigenbeams to carry space time code. A composite weighting based joint multiuser STBC and beamforming method is proposed. The key feature of the method is that interference canceling for other users and full order transmit diversity for desired user is realized simultaneity. The composite weight vector can be equivalent to a convolution operation of two sub-weight vector, one to realize inter-users interference suppressing and the order to construct uncorrelated channel for STBC, respectively. Then, to combine the cochannel interferences (CCI) suppression ability of beamforming techniques with the Alamouti transmission and achieve the receiver computational simplicity, the MS (Mobile Subscriber) beamforming process maximizes the channel capacity; the BS (Base Station) beamforming process maximizes the output SINR to suppress CCI. Since, the technique preserves algebraic structure of the Alamouti STBC and sustain the orthogonally of the virtual MIMO channel in the presence of beamforming, the Maximum-likelihood (ML) decoding process is achieved simple linear processing.