Channel Measurement And Mimo Transmission Technology Of Distributed Antenna System

The distributed network architecture is evolved from cellular cell layout, because it could improve signal quality of marginal areas, increase system throughput and improve system multiplexing performance. However, when considering the increasing demand of data rate with limited spectrum resources, and meet the needs of network optimization for future wireless data access. It has much theoretical and practical significance to study channel propagation characteristics and MIMO key technologies under distributed antenna system (DAS). Thus, the paper studied MIMO technology based on channel measurement results, combined with field measurements, parameter extraction, theoretical analysis and simulation in this study.The main contents and innovations of the paper include:(1) Studied on radio propagation characteristic of DAS. Through lots of channel measurement activities, the paper obtained the channel impulse response and propagation parameters, including: DAS path loss, building penetration loss, cross-layer penetration loss, shadow fading, root mean square delay spread, mean excess delay spread, the maximum delay spread and so on.(2) Research on DAS MIMO transmission technology.●In order to obtain closed form of outage probability functions under composed fading channels. The probability density function of Lognormal-Nakagami-m and Lognormal-Rician distribution has been derived. Furthermore, by using of Gauss-Chebychev function and the moment generating function, the expression of signal to interference ratio (SIR) has been deduced with cooperative transmission schemes.●In the aim of investigating the characteristics of correlated fading channels, the general framework of correlation matrix has been deduced with the expression of series of Bessel function. In the mean time, the correlation coefficients have been derived under Laplacian power angular spectrum, without any constraints of incidence angle.●In order to utilizing space freedom of DAS, the architecture of distributed generalized layered space time codes (GLST) has been considered. By using of basis vector from null space instead of orthogonal set, GLST can achieve both multiplexing gain and diversity gain. Moreover, OSTBC-Sphere decoding algorithm has been utilized with11.7dB improvement of system performance when compared with maximum likelihood method, while the bit error rate (BER) is equal to6.7×10-4.(3) Research on DAS MIMO antenna selection algorithms.●In the aim of improving system performance of DAS, the Gerschgorin circles based fast antenna selection algorithm has been proposed. While it can maximize the projection vectors of channel gain with minimum number of channel conditions. According to simulation results, the ergodic capacity has improved10.3%when compared with Gharavi-Alkhansari algorithm.●In order to lift minimum number restriction of traditional antenna selection methods, the transmit-receive joint detection antenna selection algorithm has been considered, where the optimal antenna arrays will be selected based on maximum capacity criteria. Furthermore, by using of matrix decomposition theorem, the computational complexity will be decreased from O(MLK4) to O(MLK2) with simplified calculation process.(4)Studied on DAS power allocation and channel prediction algorithms.●In the aim of solving channel prediction problem of DAS, the forward-backward minimum mean square error of channel prediction algorithm has been proposed based on Levinson-Durbin theory. In this way, the global optimization problem will be converted into local optimal solution, and the errors will not be cumulated during recursive process in which coupling is not existed between different recursive levels.●Based on the variation characteristic of motion state channel, the distributed power allocation algorithm has been proposed with the help of channel prediction method. Simulation results have confirmed that the proposed algorithm can match channel change effectively. Moreover, according to the residuals, average and variance of statistics data, the performance of proposed method will be improved by31.54%,25.31%and26.08%, respectively.●In order to verify the performance of different distributed power allocation algorithms, channel measurements have been conducted under urban micro cell scenarios, from which measurement results have confirmed the validity and reliability of proposed predictable pathloss water filling algorithm under single-cast and broad-cast mode.