| As an important direction for short wave frequency hopping technology, differential frequency hopping has been the concern of many researchers. This kind of correlated frequency hopping system can provide a data transfer speed faster than ever before, and better resistance to jamming and interception capabilities. The DFH radio basically based on the DSP platform, so it is an important breakthrough in frequency hopping system digitalization. Due to the efforts of many scholars, the papers of the G function and frequency sequence decoding of DFH is vary more, but the research of DFH multi-access and networking technology is basically a blank, This is one important reason why DFH is not in equipment. This paper is from the point of DFH multi-access and proposed my own solutions.After describes the basic characteristics of differential frequency hopping technology, this paper at first studied the performance of DFH system when using traditional multi-access method. Under conditions of fair, find out that DFH frequency division multiple access method is superior to time-division multiple access method in AWGN performance, but its spread-spectrum anti-jamming capability is weaker than TDMA method. This paper also studied the design of G function family for multi-access approach. Because of this approach is still at the discussion stage of possibility, here just designed one approach for two users'condition, which is to decentralize frequency collision to design the G function. Although this approach can not be extended up to the case of multi-user, it is also can be a solution of duplex technology.The focus of this paper is to present a soft-orthogonal multiple access method of differential frequency hopping, and this method is a combination of DFH frequency division multiple access method and traditional frequency hopping CDMA method. The soft-orthogonal multi-access can be divided into two kinds of situations, orthogonal and quasi-orthogonal. Under the premise of not reducing spreading gain, the system BER performance is the same with DFH frequency division multiple access method in the orthogonal conditions. In the quasi-orthogonal case, the system is an interference limited system. For the problem of multi-access interference, this paper used a method of parallel multi-access interference cancellation technology, and verified the effectiveness of this technology by simulations.At final, this paper given a summary of the research, and proposed some directions of further research. |
