Adapt and Aggregate: Adaptive OFDM Numerology and Carrier Aggregation for High Data Rate Terahertz Communications

We propose a communication framework suitable for data rate maximization in the Terahertz (THz) bands using adaptive Orthogonal Frequency Division Multiplexing (OFDM) numerology and carrier aggregation. OFDM is a widely adopted waveform due to the simplicity of its implementation and its effectiveness in combating frequency selectivity when the numerology is carefully chosen. However, it suffers from a multitude of limitations, including phase noise due to local oscillator inaccuracies, high peak-to-average power ratio, and is particularly sensitive to time-frequency synchronization errors, which can considerably impact its performance. This is especially relevant at THz frequencies where larger-than-usual bandwidth is available, and the choice of the numerology should be carefully made given the intrinsic transceiver constraints. Moreover, the abundance of frequency resources in the THz band imposes new design challenges that should be addressed, especially since the bandwidth usability at these frequencies depends on the communication distance. Hence, we propose a dynamic OFDM numerology adaptation mechanism, where the bandwidth of a Component Carrier (CC) covered by a single OFDM waveform is changed. For each CC, the Component Carrier Data Rate (CCDR) is evaluated while considering the effect of both hardware impairments and the wireless channel statistics. We further propose the adoption of a dynamic distance-aware CC allocation such that the available frequency resources are fully utilized, and maximize an Aggregated Data Rate (ADR) through the aggregation of several CCs. Simulation results show that the proposed approach yields the highest ADR out of all possible setups.