Enhancements of narrowband IoT in 3GPP Rel-14 and Rel-15

In 3GPP Rel-13, a narrowband system, named Narrowband Internet of Things (NB-IoT), has been introduced to provide low-cost, low-power, wide-area cellular connectivity for the Internet of Things. Further enhancements have been made to this system in subsequent 3GPP releases. In this paper, we describe Rel-14 enhancements that have been standardized for NB-IoT. They include positioning support, multicast support, higher data rates, and non-anchor carrier enhancements. In addition, we summarize upcoming Rel-15 enhancements and expected improvement. Representative performance results are also provided to illustrate potential improvements from the enhancements.