Research On Key Technologies And Applications Of Adapative Transmission

As the growing demands of future Wireless Communication Systems, in order to improve the rate and reliability of data transmission and improve as high as frequency spectrum utilization under the condition of limited band resources, the technology of Link Adaptive Transmission has become one of the most critical technologies for future network communication systems and largely concerned by industries.The technology of Link Adaptive Transmission is to ajust the parameters of tramsmitter and receiver dynamically on the basis of variations of time, space and fenquence in wireless channels. This technology can improve the average frequency spectrum utilization; make use of wireless channel resources as much as possible under different requirments of different kinds of services and applications. The technology of Adaptive Modulation and Coding (AMC) is one of typical technologies in Link Adaptive Transmission, which ajust the models and functions of coding according to different channel environments and variations. AMC could choose low order modulation and lower code rate on the conditions of worse channel environments, and choose high order modulations and higher code rates on the conditions of better channel environments.The thesis focus on technologies of Link Adaptive Transmission, based on joint optimization and some advanced technologies such as AMC, HARQ and LTE-Turbo. This research work research and analyse the Adaptive Transmission of wireless communication systems deeply in two categories:theoretical research and practical application. We provide the cross-layer adaptive transmission schemes based on HARQ and AMC, expand the applications of LTE-Turbo and AMC-ARQ from single antenna channel evnironments to multi antenna channel environments, and discuss the applications about picture transmissions and video transmissions using link adaptive transmission.The mainly work and innovations are listed as follow:First, the research work provides the cross-layer adaptive transmission modes. This work based on the basic principles and features of AMC and HARQ and conbines the technology of Turbo code with them. We analyse the performances of HARQ, and apply the technologies of Type-Ⅱand Type-ⅢHARQ in the corss-layer design of physical and link layer under the link layer requirements of PER and delay. For fruther research, we study the cross-layer designs which combine the HARQ and AMC, drive the mathematical expression of average frequency spectrum utilization and average transmission numbers. The simulation results show that the PER of the system can be greatly reduced and the system frequency spectrum utilization can be dramatically increased by using the proposed corss-layer adaptative transmission scheme.Second, combined with the technology of LTE-Turbo, we propose the multi antenna link adaptive transmission system model. This system researches the applications of link adaptive transmission in the environments of single and multi antenna. Because in practical conditions, the wireless channel can be influenced by outer interferences and multipath fading so the received signal could be affected greatly. According to this feature, our researches apply the cross-layer design based on LTE-Turbo, the adaptive modulation and coding in physical layer and the scheme of ARQ in link layer. By comparing the performances of different schemes and modes, we draw the conclusion that combing the technologies of AMC and ARQ would increase the frequency spectrum utilization of the communication systems compared with the only using of ARQ or AMC.Third, the research expands the cross-layer design of AMC and ARQ from single-antenna systems to MIMO systems. Using the excellent coding gain and the technology of STBC, we could get the diversity gain; combing Turbo and STBC, we derive the mathemetical models and frequency spectrum utilizations under the channels of Nakagami-m and Rayleigh. The simulation results of different channel models and transmission and receiving schemes are shown, through comparing results of different schemes, we can see that under MIMO systems, using the scheme of AMC-ARQ could extremely imporve the character of frequency spectrum utilizations.Fourth, for applications, focusing on transmissions of static pictures and videos, the thesis researches the practical applications of these technologies of adaptive transmission. Through comparing the performance advantages of adaptive transmission upon other schemes, we analyse and conclude the potential practical problems in practical applications.