Research On Several Key Technology Of New Type Short-Wave Radio

The instability of shortwave channel leads to the smaller capacity and lower reliability. MIMO technology is an effective way to solve this problem, by virtual collaborative MIMO channel which is constructed by a plurality of users, to represent transmission diversity on the mobile terminal, and transmission quality in multi-antenna reception of the receiving terminals, improving the wireless communications system quality.To design and develop a shortwave MIMO communication system, we need to consider the transmission characteristics of the channel, establish a more accurate channel model and simulate the channel. Channel simulation accuracy and performance will directly affect the development and design of shortwave communication system. Therefore, the structures and channel simulation model is the premise to understand the channel characteristics and development of the system. In the same scene multiple antennas, the number of communication links between the sending and receiving end increased, the simulation should consider how to reduce the complexity of channel emulation, providing fast and accurate shortwave MIMO channel simulation model. This thesis provides a solution to those problems firstly.Shortwave MIMO communication system can support multi-user communications, providing a new scenario for the short-wave communications. With the increasing number of users, the interference between users will affect system performance. Pre-coding technology can effectively eliminate interference between users, and thus become a hot topic of MIMO technology. Pre-coding techniques using channel state information in the signal originating preprocessing, to enhance receiver signal detection and reduce inter-user interference, thereby improvingsystem performance. Because of the relatively narrow bandwidth andlonger delay, it is more difficult to perform real-time channel stateinformation feedback. How to improve the performance of pre-codedshortwave channels is this thesis’ second topic.After a detailed analysis of the article shortwave transmissioncharacteristics and features of HF channel in the ionosphere, this paperintroduced scientific advanced inherent characteristics of traditionalshortwave transmission scheme based on traditional link layer and physicallayer shortwave transmission scheme based on the inherent characteristicsin recent years, and for the delay spread, Doppler shift and Dopplerfrequency between the extended defects which the inherent characteristicsof these traditional shortwave program currently can not be accuratelydescribe, which leads to a comparative analysis based on statisticalproperties of the Watterson HF channel model, Watterson plus Gaussianrandom delay model, sub-parallel model and ITS model with severaltypical HF channel models, and finally select ITS HF channel model as thebase of the HF channel modeling program improvement. For itscalculation and simulation are difficult issues, this paper presents animproved power distribution function of the delay, the distribution functionof the realization of the new proposed process is simple, and have similarstatistical properties with the ITS models. Meanwhile, based on improvedbroadband HF channel model, this paper made model realization tomid-latitude and high-latitude measured shortwave communicationchannel, which prove the validity of the proposed power distributionfunctions to improve delay programs.In wideband HF channel simulation, it needs to generate a greatamount of colored Gaussian random process which are unrelated, based onthe idea of traditional MEDS methods and compensation thought, thispaper proposed a new method of simulation models: the CompensationMethod of Exact Doppler Spread (CMEDS Method). For Gaussian power spectrum, comparing with existing methods, the new proposed method notonly has statistical properties closer to the theoretical model, but alsosignificantly improved simulation efficiency.For time-varying and the frequency shift characteristics of shortwavechannel, this paper established the channel prediction model. Then thepaper takes shortwave channel characteristics into consideration, andstudies the limited feedback pre-coding technique in MU-MIMO downlinkshortwave communication system, the application of limited feedbackpre-coding technology can greatly improve the data transfer rate ofshortwave communication system. The paper also analyzed the impact ofDoppler frequency shift and time-varying factors to MU-MIMO downlinkshortwave communication system.