Cooperative Interference Avoidance Scheduler for Radio Resource Management in NB-IoT Systems

Narrow-Band Internet of Things (NB-IoT) is a licensed cellular technology aimed at servicing the low-power and long-range IoT applications. It is a variant of the Long Term Evolution (LTE) with reduced complexity to lower the cost of the devices. The NB-IoT's design changes on the physical (PHY) layer, i.e. the limited system bandwidth of one physical resource block (PRB), i.e. maximum 200 kHz, single antenna support, lower-order modulations, etc. inhibit the mapping of traditional LTE radio resource management techniques to NB-IoT systems. Consequently, possible interference due to massive connectivity may severely degrade the expected system performance. In this paper, we propose an interference avoidance scheduling algorithm for NB-IoT systems. The algorithm entails a cooperative strategy in which the base stations share their respective scheduling information i.e. location, SNR, device's path-loss, etc. (through X2 interface) which is then used to compute the interference between the users to be scheduled. The computed interference values are then used as input to individual base station schedulers to perform scheduling for the next radio frame. The scheduler then allocates the radio resources to the UEs with the lowest possible interference. Extensive simulations are carried out to analyze the performance of our proposed algorithm and compare it to the conventional Round-Robin scheduling scheme. The results show that our proposed algorithm provides up to 36% throughput improvement to the NB-IoT UE as compared to Round-Robin. Similarly, for the same device's locations, the UEs are experiencing relatively better maximum coupling loss (MCL) which results in lower repetition numbers per coverage class.