High-frequency Data Communications Research

How to improve the bit rate of limited bandwidth is the primary research direction of HF communication, and it is also the primary research direction of other communication system. When we improving the bit rate, the error bit rate should be guaranteed too. The most work of this paper is on the two topics. At last, I have researched the ability of the HF communication station set up to network. This paper is organized like this:Chapter one: I have introduced the characteristic and application of HF communication. The history and status in quo of HF communication is be introduced too.Chapter two: I have researched the characteristic of HF channel, supplied the model of HF channel, studied QAM modulation and designed digital filter with software and hardwire. The channel estimation based of OFDM with pilots have been studied systemic. The result of HF communication based on 16QAM-OFDM has been provided.Chapter three: I have studied the coding and decoding algorithm of convolutional code and Turbo code particularly. I have studied the turbo decoding algorithm in rayleigh fading channels , simulating the rayleigh fading channels by Jake method. I adopt a new algorithm which combine channel estimation with Turbo code .Simulation results have shown great performance in this system.Chapter four: I have analyzed the ALOHA protocol on OPNET., studied the simulation technology of network. I have simulated the HF communication network bade ALOHA protocol on OPNET.