Abstract
Although UNB is scorned by the advanced in the art, a new view of understanding it is presented through power spectra and bandwidth analysis. Bandwidths of UNB modulation schemes such as VMSK are analyzed by deducing their power spectrum analytical forms. Both mathematical analysis and simulation results show that UNB modulation schemes cannot attain high bandwidth efficiency. A conclusion is reached that VMSK etc. are not "ultra narrow spectrum" modulation, but a kind of "wideband" modulation with carrier. Or, UNB is to mean that frequency band occupied by the carrier is "Ultra narrow", but signal bandwidth including modulation information is "wideband". ZGD filters are analyzed. And it is proposed that CSVMSK modulation can achieve a high bandwidth and power efficiency using bps/Hz/W as measurement unit, power spectrum of which, without discrete line spectrum components, can be lower than -60 dB only if proper modulation parameter N is selected, thus, its spectrum can underlay to the licensed spectra and share them. So, UNB can be understood from the view of spectrum sharing and cognitive radio. The theoretical bit error rates (BER) of VMSK, BPSK and CSVMSK are presented and simulation results verify the theoretical values: BPSK and CSVMSK have the same BERs, which are better than VMSK, but CSVMSK has a better bandwidth and power efficiency than BPSK. Besides, CSVMSK has the performance like xMax technology.
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