Research Of Hybrid DS-FH Spread-spectrum Communication System Resisting Near-far Effect

Spread-spectrum communication is one of the communication mode, which has vast vista and is widely used in military communication and in civil communication.A new hybrid spread-spectrum (DS-FH) communication mode is discussed in detail in this paper, Walsh sequence is used as frequency-hopping sequence in this mode. By analyzing the spectrum feature and correlation feature of Walsh sequence, we find that it has the spectrum feature of DS/FH (direct spread/frequency hopping) communication mode. Combining Walsh sequence with direct spread spectrum sequence, we can construct hybrid DS-FH spread-spectrum communication mode. This is very important for the mode to have better performance on anti-multiple-access inference and anti-near-far inference.To assure that the hybrid DS-FH spread-spectrum communication mode has better capability of information safety and inference suppression, I bring forward a design scheme of DS-FH spread-spectrum communication system and solving effectively the crucial problem such as how to choose the user address, how to choose the hopping frequency and how to avoid the collision of the frequency which is used by different users at the same time. By simulation of DS system and DS-FH system, we can get the performance of the two spread spectrum communication mode. The consequence verifies that DS-FH system has better inference suppressing performance than DS system and it can ameliorate the capability of resisting near-far effect.To combine theoretical and simulating productions with the practical application, we use CPLD chip to realize the hardware flat of hybrid DS-FH spread spectrum communication system, which provides the basic of the further practicability.