Offset-Aware Resource Allocation in NB-IoT Networks

Narrowband Internet of Things (NB-IoT) is a critical technology for fifth-generation (5G) and next sixth-generation (6G) networks to meet the high density and latency requirements for massive devices. Before data transmission or reception in NB-IoT networks, a device needs to monitor a search space in a narrowband physical downlink control channel (NPDCCH). When the NPDCCH resource is exhausted, neither data transmission in the narrowband uplink shared channel (NPUSCH) nor data reception in the narrowed downlink shared channel (NPDSCH) is possible, even if the two channels still have available radio resources. To solve the problem, the 3rd generation partnership project (3GPP) puts forth an NPDCCH offset mechanism for NB-IoT, which can set different offset values for different devices. Devices using different NPDCCH offset values can postpone different time intervals for monitoring their NPDCCH search spaces so that the devices do not need to contend for the same NPDCCH search space. However, this article finds that improper use of the NPDCCH offset mechanism will hurt the system's performance. Therefore, this article investigates how to use the NPDCCH offset mechanism in uplink and downlink resource allocation. The objective is to minimize the consumption of uplink and downlink radio resources while each device can transmit and/or receive its data. We propose an offset-aware resource allocation algorithm to solve the problem. Compared with two resource allocation algorithms with and without using the NPDCCH offset, the simulation results provide several insights and show that the proposed algorithm effectively reduces radio resource consumption.