Research Of Narrow Band And Low Sample Rate TS-NMT

High quality and high transmission speed have always been the request of people to the communications technology. However, along with the popularization of network and increase of correspondence users, spectrum resources are becoming more and more limited over time, it has already become a big barrier which restricts development of communication technology. How to compress the signal's frequency spectrum, and how to enhance the frequency spectrum using efficiency, have been the popular direction which is researched in communications now. Orthogonal Frequency Division Multiplexing (OFDM) continues to be used until now since it was proposed because of its superior performance. However, the modulation technology does not have the unprecedented progress again for years. Time Shift Non-orthogonal Multi-modulation Technology(TS-NMT for short) was proposed by Professor Liang Dequn can break through the orthogonal limit. Through the strict theoretical analysis and the massive simulation experiment, it is proved that TS-NMT has higher frequency efficiency compared to other modulation systems.For the more effective using frequency resources, the narrow band technology and the ultra narrow band technology has been proposed one after another, which provided a new mentality to communications'development. Because the signal bandwidth is in inverse proportional to signal element period, through lengthen signal element period may compress signal bandwidth. To the tradition modulation system, lengthen signal element period will reduce transfer rate, and the signal power will be also enlarged at the same time. But TS-NMT, because of its time shift characteristic, can keep signal power basically constant, and maintains transfer rate invariable by increasing the wave number. Thus raises frequency efficiency greatly. This method is called narrow band TS-NMT. This article demonstrates rationality of narrow band TS-NMT' high frequency efficiency characteristic. However, new problems arise from lengthen signal element period.On the one hand it increases the signal's initial phase delay, on the other hand it enlarged the complexity of operation. Therefore we proposed the time-subsection demodulation method, this method can effective solute these two problems. Narrow band TS-NMT and time-subsection demodulation method are simulated by matlab.While the time shift Non-orthogonal characteristic of TS-NMT brings its high efficiency, also bring its disadvantage of high sampling rate. In the actual system, higher sampling rate requests system's hardware handling ability stronger, that will increase system's cost, and disbennifit to the promotion of TS-NMT. The frequency division modulation and demodulation method demodulation r can reduce TS-NMT the sampling rate effectively. This article made the theoretical analysis to this method and complete simulation.