Quadrupling the Data Rate for Narrowband Internet of Things without Modulation Upgrade

This work proposes a novel signalling method for Narrowband Internet of Things (NB-IoT) mobile system where a quadrupled data rate can be achieved by combining two orthogonal techniques; the frequency orthogonal Fast-Orthogonal Frequency Division Multiplexing (Fast-OFDM) scheme coupled with the time orthogonal Hilbert transform (HT) pair. In this paper, the orthogonality features of one dimension in Fast-OFDM and of the HT pair are explored. The newly designed system structure is presented where the HT pulse pair is generated by square root raised cosine (SRRC) filter with a matched configuration at the receiver. System performance is investigated in terms of bit error rate (BER), effective data rate and spectral efficiency. Simulation results show that the HT-Fast-OFDM system provides 4 times the data rate relative to an OFDM system employing the same modulation scheme and occupying the same bandwidth. Furthermore, the proposed system has compelling advantages over 16- QAM OFDM for it achieves a better BER performance at the same spectral efficiency.