Half-Sine Waveform Design for Narrowband IoT

Narrowband Internet of Things (NB-IoT) is a cellular based IoT technique, which can send messages at a long distance using repetitive transmission and single tone frequency hopping. However, retuning of the RF front-end for each narrowband hop could cause frequency offset. Since each tone is shaped by a sinc pulse, when combining tones into a complete signal at the receiver, the side lobe of the sine pulse would result in significant signal interference in the frequency offset condition. In this work, we propose a half-sinc (HS) waveform for uplink channels via cutting half band using the Hilbert transform to intentionally reserve a frequency offset protection gap. It is verified that the half-sinc waveform can tolerate up to 100% frequency offset via simulation and can practically remove the half side signal band in a software defined IoT platform.