Coded Msk System Synchronization Technology

In the ELF(extremly low frequency) and VLF(very low frequency) systems, it was used to need a low rate, great error correction ability code to communication between both sides. By far, several codes as Turbo codes, LDPC codes and sequential decoding would satisfy the conditions, and Turbo codes was the mostly research subject.As turbo codes were proposed, the performance of system was sensitive to synchronization parameters. Since turbo codes were intended to work in environments with very low SNR, conventional synchronization methods often failed. Synchronization word with information of timing and carrier phase was tested for estimation synchronization parameter. While testing the interrelation peak value, the timing and carrier phase were estimated. Then, as Turbo codes were decoding, Turbo's iterative function was utilized to iteratively estimate synchronization parameter. These methods make the synchronization arithmetic more precise. When the arithmetic was actually carried through, interpolation was used to update the demodulation data which needed to iteratively compute. The interpolation function increased the decoding complexity only a little.Simulation experimentation was operated on MSK signal. The simulation result indicated that the bit error rate of synchronization arithmetic compared with severe synchronization was lower less than 0.2dB.After software simulation, the synchronization arithmetic was executed in hardware stage. The DSP chip TMS320VC5416 of TI incorporation and audio output were used to simulate the transmitter, and the TMS320C6416 and audio input were used to simulate the receiver. The hardware simulation showed that the synchronization arithmetic had sufficient practicability.