Variable Bandwidth Multicarrier Communications: A New Waveform for the Delay-Scale Channel

In this paper, we develop a new waveform for communicating over a delay and time-scale spread wideband channel. This waveform, named Variable Bandwidth Multicarrier (VBMC) waveform, comprises multiple subcarriers that are constructed from chirp pulses used in radars and sonars, and is a multicarrier analogue of the sweep spread carrier waveform that time multiplexes the digital symbols onto a single chirp pulse. We design the subcarrier chirps to occupy progressively increasing, frequency-dependent bandwidth from the lower to upper frequency edge of the communication band. Due to this, the subcarriers of the VBMC waveform maintain their near mutual orthogonality even after passing through a delay and scale spread channel, resulting in low inter-carrier interference, and thereby facilitating a low complexity subcarrier-by-subcarrier decoding at the receiver. Numerical simulation of the bit error rate over delay-scale channels shows that the VBMC waveform outperforms the widely used Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) and the recently developed Orthogonal Time-Frequency Space (OTFS) waveforms.