Research On Key Technologies And Methods Of TR Wireless Communication With High Reliability In Closed Cabin

In recent years,with advancements of human beings in outer-space exploration,the aerospace technology is developing vigorously.In the meantime,the demand for communication within the spacecraft is also increasing.The traditional method of wired communication faces the restriction of size and weight of devices,which has become a major challenge in the design of spacecraft.Thus,applying the technology of wireless communication in the spacecraft will be necessary.However,different from the scenario on the earth,spacecraft is a sealed capsule.The channel environment in the craft is extremely complex,and the multi-path effect is significant.This leads to severe interference between transmitted symbols and poor quality of communications.The reliability of the communication system cannot be guaranteed.Time Reversal(TR)technology has its unique features of space-time focusing and super-resolution focusing.The time focusing can dramatically increase the signal-noise ratio and effectively control the delay spread of the signal,thus reducing the interference between the symbols.And also,the super-resolution focusing enables the gap between antenna units to breakthrough the limit of ?2/,and reduces the size of devices and improves the capacity of the communication systems.Those features of TR technology make it unchallenged in the application of in-craft wireless communications.Based on this knowledge,this thesis studies the time-reversal wireless communications within the spacecraft,and analyzes the prospect of wireless communications in this scenario and their challenges.Chapter 1 introduces the system of traditional wired communications,analyzes the domestic and foreign development of the in-craft wireless communications,and also the prospect and challenges of this technology.Chapter 2 introduces the basic theory of OFDM,analyzes the phase diffusion of OFDM signals caused by the multi-path fading channel,and explores the possibility of eliminating the phase rotation by taking advantage of the space-time focusing of time reversed signal.Chapter 3 studies the TDD-TR system uplink channel pre-detection technology,analyzes the performance of LS-DFT and MMSE channel estimation algorithm in the space environment.The results show that the LS-DFT channel estimation algorithm not only has low computational complexity,but also has excellent estimation accuracy.This has laid a solid foundation for the application of the TDD-TR-OFDM wireless communication system in spacecrafts.Chapter 4 proposes the TDD-TR-MISO-OFDM system scheme based on the traditional MISO-OFDM system scheme,establishes the mathematical model of TDD-TR-MISO-OFDM system.The communication performance of the above system in spacecraft is evaluated by simulations.The simulation results show that the communication performance of TDD-TR-MISO-OFDM system is far superior to the traditional MISO-OFDM system.Chapter 5 proposes a new scheme of TR-MIMO focused wireless communication system based on the adaptive focusing feature of TR electromagnetic waves for the problem of communication performance degradation caused by the dense node distribution in WSN(wireless sensor network).The bit error rate performance of the above system are analyzed by simulations.The results show that the bit error rate of the new system approaches 0 as the signal-to-noise ratio increases.The above results fully validate the potential advantages of TR technology in wireless communication application.Chapter 6 summarizes the contents of this thesis and analyzes the prospect of the research.