Experimental Performance Evaluation of Cellular IoT networks in Deep-Indoor Scenario

Narrow-band Internet of Things (NB-IoT) and LTE-M are two emerging Low Power Wide Area Network (LPWAN) technologies in the IoT space. Both NB-IoT and LTE-M are based on the 3GPP LTE standard with added features specifically designed for Low Power, remote, and reliable IoT applications. Among other things, these Cellular-IoT (C-IoT) technologies promise improved deep-indoor performance (at least 20 dBm) over traditional LTE standards. In this paper, we have tried to evaluate the deep-indoor performance of NB-IoT and LTE-M. The technologies have been evaluated based on End-to-End delay, bitrate, received signal quality, and packet drop in uplink (UL) and downlink (DL) directions. The tests have been performed using the commercially deployed NB-IoT and LTE-M networks by operators in Denmark. These tests were conducted in the underground tunneling system of the Technical University of Denmark at levels L-1 and L-2 from the ground surface. The outcome of these tests was then compared with the outcome from the best-case scenario, where the base station is in the Line of Site (LOS) to the User Equipment(UE). In total, the tests were conducted at 18 different locations with a total of approx—two hundred eighty-eight thousand packets sent using both technologies, over two telecom operators with varying packet sizes. The goal behind experiments is to test the performance of C-IoT technologies in multi-technology deployment (in parallel with GSM, LTE, etc.) and gather real-world performance data from the networks. The idea is to determine whether C-IoT can be used for deep-indoor applications deployment. The results from these tests indicate that C-IoT networks had a degraded and unreliable performance in poor radio conditions.