Waveform and Space Precoding for Next Generation Downlink Narrowband IoT

Narrowband Internet of things (NB-IoT) was introduced by 3GPP in low power wide area network (LPWAN) to support low power and wide coverage applications. Since it follows long term evolution (LTE) standard, its signal quality is guaranteed and its deployment is straightforward via reusing existing infrastructures. Current NB-IoT supports low data rate services via using low order modulation formats for the purpose of power saving. However, with the increase of data rate driven applications, next generation NB-IoT would require data rate enhancement techniques without consuming extra battery power. In this work, a downlink framework, using a non-orthogonal signal waveform for next generation enhanced NB-IoT (eNB-IoT), is proposed and experimentally tested in both single-antenna and multi-antenna systems. In the single-antenna scenario, waveform precoding is used to pre-equalize the self-created inter carrier interference (ICI) distorted signal waveform. For the multiantenna multi-user scenario, both waveform and antenna space precoding have to be used. Measured results show that in both single-antenna and multi-antenna systems, the proposed signal waveform in eNB-IoT can increase data rate by ∼11% compared with NB-IoT occupying the same spectral resource in similar receiver computational complexity