QPSK is a kind of modulation which has high spectrum efficiency and strong anti-jamming, it is widely used in various communication systems. Such as WCDMA system in the 3G communication systems,Its Downlink Modulation take QPSK modulation. Using QPSK modulation, while ensuring that the signal transmission efficiency and BER. Joined the convolutional code encoder can be reduced effectively QPSK communication system bit error rate. can also ensure the signal transmission accuracy and reliability.
In this paper, based on convolutional code ,a QPSK system is analyzed, designed and simulated on computer. This paper mainly consists of four parts: the basic principles of QPSK system, the design of QPSK system witch based on convolutional coding, the design of QPSK system witch based on Viterbi encoding, the system simulation and the analysis of the results.
This paper has designed and simulated an intergrated baseband QPSK system, simulated the system with C language and given reference design process, First QPSK modulation，using convolutional codes to encode bits of data,through channel，then Demodulator and Viterbi decoding,calculating its error rate and depicting Simulation diagram.
