Study Of Differential Frequency Hopping System, Multi-user Detection Techniques

In recent years, the short-wave Differential Frequency Hopping (DFH) technology,combines modulation, encoding and frequency hopping technology organically, enormously improves the data transmission capacity, anti-interference and anti-fading ability of the communication system, represents the research direction of new generation HF anti-jamming communication scheme.Although thorough researches have been done on DFH, they are mostly restricted to the scope of single-user algorithms, only very few of them are focused on the subject of multi-user communication. Based on this premise, this thesis summarizes the author's researches on DFH multi-user detection, including multiple-access performance and detection technology. This thesis briefly introduces the developments of short-wave frequency hopping communication as well as the overseas application and research situation on DFH technology, and describes in detail the DFH communications system's overall framework. Design criteria for the frequency transfer function, the key technology in a DFH communication system, is described in detail, both for single user and multi-user.Based on the studies on frequency trellis decoding which is essential for the Differential Frequency Hopping system, we get the path metrics of the frequency trellis decoding. Two optimal multi-user algorithms based on the criteria of ML and MAP are listed as examples, their complexity is exponential with respect to the number of users ( ( )O M N), this is obviously too complicated for application. Applying successive interference canceling (SIC) technology, we bring forward a new algorithm. This algorithm is sub-optimal, but it has the linear complexity with respect to the number of users, which makes it to be more practicable. Performance of this algorithm is discussed later, and simulations are given to testify it.At the end of this thesis, we summarize the work of this thesis and give the work to be continued.