  As an attempt to tackle the low-data-rate issue of the conventional LoRa
systems, we propose two novel frequency-bin-index (FBI) LoRa schemes. In scheme
I, the indices of starting frequency bins (SFBs) are utilized to carry the
information bits. To facilitate the actual implementation, the SFBs of each
LoRa signal are divided into several groups prior to the modulation process in
the proposed FBI-LoRa system. To further improve the system flexibility, we
formulate a generalized modulation scheme and propose scheme II by treating the
SFB groups as an additional type of transmission entity. In scheme II, the
combination of SFB indices and that of SFB group indices are both exploited to
carry the information bits. We derive the theoretical expressions for
bit-error-rate (BER) and throughput of the proposed FBI-LoRa system with two
modulation schemes over additive white Gaussian noise (AWGN) and Rayleigh
fading channels. Theoretical and simulation results show that the proposed
FBI-LoRa schemes can significantly increases the transmission throughput
compared with the existing LoRa systems at the expense of a slight loss in BER
performance. Thanks to the appealing superiorities, the proposed FBI-LoRa
system is a promising alternative for high-data-rate Internet of Things (IoT)
applications.
