Analysis And Simulation Of Frenquency Hopping Communication System Based On No-Hit-Zone Code

Networking is the key for the frequency hopping (FH) communications to be working properly in the FH system. There are two main networking techniques, that is, synchronous and asynchronous networking. The synchronous networking requires that Hamming correlation of the FH sequence set used is zero at the zero shift, but all users in the system must access the system synchronously. On the other hand, the asynchronous networking requires that Hamming correlation of FH sequence set is as small as possible although it is impossible to design the FH sequences with no hits at all according to the theoretical bounds. In this thesis, the No-Hit-Zone (NHZ) hopping sequences are employed. The NHZ code sequences have no hits at all within a predefined correlation zone in the vicinity of zero shift.In this thesis, a new quasi-synchronous multiple access scheme suitable for FH communication system employing NHZ hopping code is proposed. In particular, the design and realization of an FH communication simulation platform is investigated in details.For comparison purpose, two simulation platforms for FH systems employing RS code and NHZ code are set up respectively by using MATLAB6.5/SIMULINK as simulation tools, and lots of experiments are carried out based on the platforms. Our analysis and simulation results show that the bit error rate (BER) is improved significantly in multi-user environment while nearly no improvement in single-user situation. The reason is that the multi-access quasi-synchronization scheme assures the time delay among transmitters to be limited in no hit zone of NHZ code.