An Analytical Model for Assessing the Performance of NB-IoT
Résumé
As part of its ongoing effort to standardize 5G and become a key enabler of the Internet of Things, 3GPP introduced NB-IoT – an LPWAN access technology for massive Machine Type Communications (mMTC) – in Release 13. Rooted in LTE, NB-IoT introduces several innovation aimed at meeting the 5G IoT requirements, especially in terms of capacity. Already a commercial success with 94 deployments in over 35 countries, the performance of NB-IoT remains, however, poorly understood.In this paper, we introduce a theoretical model based on M/D/1-PS queues for assessing the performance of NB-IoT as function of different network settings and protocol configurations. Our model is the first to accurately capture the random access procedure for connection establishment (the contention phase) and the entire communicate process, with signalling, connection release and uplink, downlink messages (the congestion phase).After using simulations to demonstrate its accuracy, we use our model to assess the performance of NB-IoT as function of its key parameters. Our analysis reveals a) the NPRACH/NPUSCH ratio has to be chosen carefully and take into account the traffic distribution, and b) for small packet sizes, the NB-IoT signalling becomes a significant bottleneck to the number of UEs that can be supported.