CI/FSK: bandwidth-efficient multicarrier FSK for high performance, high throughput, and enhanced applicability

In traditional binary frequency-shift keying (BFSK), two distinct carrier frequencies are used to represent binary data. In this letter, we propose transmitting multiple orthogonal, in-phase subcarriers around two distinct carrier frequencies to represent binary information. The envelope of the resulting FSK signal is a carrier interferometry pattern, and hence, the name carrier interferometry (CI/) FSK. We demonstrate that this technique is spectrally efficient when compared to traditional BFSK. Performance and data-rate benefits are also demonstrated with the use of a novel coherent reception technique. Moreover, while it is difficult to employ traditional BFSK in multipath channels, we show how the new CI/FSK scheme exploits frequency-diversity benefits when used in such channels.