Differential STFLC With Resource Grid Mapping for Robust IoT Connectivity in Time-Varying Frequency-Selective Channels

Wireless communication systems under high mobility and multipath conditions suffer from severe channel variations in time and frequency. To overcome this issue, this study extends a differential space-time line coding (DSTLC) scheme to an orthogonal frequency-division multiplexing framework, i.e., a differential space-time-frequency line-coded (DSTFLC) system. In the DSTFLC system, communication performance depends on how the DSTFLC symbols are arranged on the time-frequency resource grid. To address this issue, three resource grid mapping (RGM) schemes are proposed: time-first RGM, frequency-first RGM, and Gilbert (generalized Hilbert) RGM schemes. As verified by the numerical results, three RGM schemes exhibit distinct benefits under different channel conditions, namely, time-varying channels with short delay spreads, frequency-selective channels in low-mobility scenarios, and time-varying frequency-selective channels. The proposed RGM schemes would provide practical design guidelines for deploying various Internet of Things applications under dynamic channel conditions.