Research On The Realizability Of UNB Communications And VWDK

The increasingly rising conflict has produced the fact that communications technology of the time is earnestly longing for data transmitting technology with high frequency bandwidth efficiency, between the scarcity of frequency resource and the requirement of information transmitting with high speed and credibility. UNB (abbr. of Ultra Narrow Band UNB) communications, which is named as USM, abbr. of Ultra Spectral Modulation in business, is exactly the technology providing extremely high bandwidth efficiency up to 100bps per hertz, whose simulation based on Matlab platform was recently reported that had finished. UNB communications, firstly proposed by H. R. Walker, has developed from VPSK, Improved VPSK, and VMSK, edified by which, Prof. Wu Lenan etc. proposed a new UNB modulation approach named as VWDK (abbr. of Very Minimum Waveform Difference Keying) to PRK. Unfortunately, there exist heated controversies on the realizability of UNB communications. Therefore, the objective of this paper is to analyze the characteristics of VWDK and the realizability of UNB communications. Firstly, the definition of the basic concepts in relation to frequency and band were reviewed, and then the power spectrum density, the performance of correlation detection and the optimization of high-order harmonics of VWDK signals derived and simulated in detail. For the proof of UNB communications, the four patents were analyzed and rectified, based on which the promiscuous explanation of Walker were updated fundamentally. Furthermore, some improper or false arguments were corrected, the two sorts of zero-group delay filters of vital importance to UNB studied, and the steps for subsequent researches of the realizability of UNB drawn up. Because time was limited, the principles of UNB employing PRK were only developed qualitatively. The results indicated that the performance of correlation detection of VWDK, featured by ultra narrow bandwidth under the common definition, could be improved to some extent after optimization of the waveforms, but was not as satisfying as wish. And on the other hand, UNB communications should be treated as a technology of carrier communications, and could be realized to a certain extent. Nevertheless no sufficient proof was provided. The results of qualitative analysis could and should only be reckoned as a reference, which will give rise to more financial, material and intellectual resources afforded for the subsequent researches to reach the summit of this technology with fascinating perspective.