.3 The Gpp Lte Link Adaptive Technology In Collaboration Communications Applications

Mobile communication has gradually influenced people's lives in a deep way, since it first stepped into people's daily life. At present, the field of mobile communication is experiencing an intensive growth, and the new generation mobile communication system is evolving from proposals and specifications into applications and entities. The continuous development of novel wireless services induces mobile communication to have properties of broadband and diversity. At the mean time, cellular communication, mobile radiated television and wireless broadband network are accelerating to penetrate and mix with each other, and these networks will gradually merge to be one united network system. In such a thriving situation, the research and development of the new generation communication system have realistic meanings.The Long Team Evolution (LTE) project was proposed by 3rd Generation Partnership Project (3GPP), and 3GPP has devoted an enormous effort to this 3G evolution project. The mission is to construct the framework of next generation mobile communication system, which will be the foundation of developing 4G system. Currently, LTE-Advance project which is the candidate of 4G scheme has aroused more and more concern by the researchers. New technologies are being applied into the system to accomplish a more efficient future mobile communication system. Among them, cooperative communication, also known as relay technology, which is one of the new technologies used in LTE-Advance, can provide the system with more diversity gains.In order to have a deep insight into LTE system, we developed a LTE physical layer baseband communication system according to the LTE specifications and massive proposals from 3GPP members. Also we conducted a thorough simulation to evaluation the system's performance, and compared it with the test results of other companies to verify the whole system. This article mainly investigated the link adaptation schemes of LTE system based on this simulation platform, and simulated adaptive modulation and coding (AMC) and Hybrid ARQ schemes in the platform. These two link adaptation schemes adaptively control system parameters in different way, and simulation results showed that AMC and Hybrid ARQ schemes further improve system throughput. In addition, this article simulated various kinds of Hybrid ARQ schemes and proposed a novel adaptive Hybrid ARQ scheme according to the phenomenon of different gains of traditional Hybrid ARQ schemes in different channel conditions, as well as the error accumulation after combining in the receiver. Its key idea is to adaptively choose Hybrid ARQ schemes in the transmitter and selectively combine packages in the receiver to improve the throughput performance of currently existing Hybrid ARQ schemes.Meanwhile, this article studied the cooperative communication system which was adopted in LTE-Advance project, introduced existing cooperative Hybrid ARQ schemes and designed a modified cooperative Hybrid ARQ scheme based on rate compatible punctured convolutional (RCPC) codes to apply into the cooperative communication system, so as to further improve the date rate, communication reliability and system throughput rate. Numerical simulation results showed that the novel Hybrid ARQ scheme employed in the cooperative system can effectively ameliorate the system performance.