Accurate Performance Modeling of Uplink Transmission in NB-IoT

With the development of LPWA (Low Power Wide Area) technology, the emerging NB-IoT (Narrowband Internet of Things) has attracted much attention and enabled a wide range of applications. An uplink of NB-IoT is a link from a user equipment (UE) to a base station (BS). Uplink transmission is a key component of NB-IoT, accomplishing the sensor data collection task for many applications. However, the performance of uplink transmission has not been rigorously analyzed in the current literature, while uplink performance degradation like long latency could be harmful to many applications with strict uplink performance requirements. In this work, we show a way of mathematically analyzing the performance of uplink transmission for NB-IoT systems, concerning the transmission latency and transmission reliability. Our model is accurate with consideration of the protocol details and the new features of NB-IoT, including link quality, packet size, channel access contention, and etc. We validate the analytical results through detailed simulations. Results show that our analytical model can achieve 83% accuracy for latency calculation and 96% accuracy fur reliability calculation. Moreover, we demonstrate that the analytical results can be used to aid protocol design for performance optimization, e.g., repetition number tuning for reducing the transmission latency.