Research On TCM-CPM Modulation And Demodulation Techniques

With the rapid development of wireless communication technology in recent years,the demand of communication system is higher and higher to people.In theory,we can improve the information transmission rate by extending bandwidth,but it will cause the spectrum resources to increasingly tense,how to achieve efficient data transmission within a limited bandwidth is a major problem in nowadays society.Therefore,we need to consider the impact of various factors to improve the reliability and effectiveness of transmission in the communication transmission.After years of exploration and research,trellis-coded-modulation(TCM)gradually developed.TCM is a combination of modulator and encoder and the metric is based on the Euclidean distance between the symbol sequences for the overall design so that the Euclidean distance between the symbol sequence maximum.With the rapid development of TCM technology,we gradually combine various encoding with modulation.Under the condition of keeping transmission power and bandwidth the same,we should ensure optimal diversity of signal space and increase the free distance between sequences to obtain the coding gain so that we can improve the reliability of digital transmission system.Continuous phase modulation(CPM)is an efficient modulation technique with constant envelope and continuous phase characteristics.Compared with other modulation techniques,it can further weigh the relationship between power and bandwidth and improve the reliability of system.Therefore,we introduce the general form and characteristics of CPM signal firstly and analyze the method of CPM tilt phase expression,on which basis to achieve an effective combination with the TCM to obtain TCM-CPM system,which provides a theoretical basis for efficient data transmission within a limited bandwidth.The low complexity demodulation algorithms of TCM-CPM detection is analyzed and studied on the basis of conventional demodulation.In coherent demodulation,we use the phase-based path exclusion algorithm to reduce the amount of calculation by filtering out the possible signals that are not substantially similar to the received signal before performing the correlation operation and the simulation shows that its performance has less loss than the conventional coherent demodulation algorithm.In the non-coherent demodulation,we use the reduced state non-coherent sequence detection algorithm combined with decision feedback.In order to reduce the demodulation complexity we merge state to simplify the state so that it can reduce the number of decoding states.We also introduce a rotation invariant system of TCM-CPM.Taking into account the particularity of CPM phase continuity,it is analyzed and studied to ensure that the communication system with phase ambiguity work properly.Due to the high complexity of phase synchronization in frequency hopping system,the modulation method of TCM-CPM is studied and analyzed on the basis of CPM data assisted phase synchronization and the performance of quasi-coherent demodulation algorithm is analyzed through computer simulation.