Narrowband internet of things (NB-IoT) is a recent cellular radio access technology based on Long-Term Evolution (LTE) introduced by Third-Generation Partnership Project (3GPP) for Low-Power Wide-Area Networks (LPWAN). The main aim of NB-IoT is to support massive machine-type communication (mMTC) and enable low-power, low-cost, and low-data-rate communication. NB-IoT is based on LTE design with some changes to meet the mMTC requirements. For example, in the physical (PHY) layer only single-antenna and low-order modulations are supported, and in the Medium Access Control (MAC) layers only one physical resource block is allocated for resource scheduling. The aim of this survey is to provide a comprehensive overview of the design changes brought in the NB-IoT standardization along with the detailed research developments from the perspectives of Physical and MAC layers. The survey also includes an overview of Evolved Packet Core (EPC) changes to support the Service Capability Exposure Function (SCEF) to manage both IP and non-IP data packets through Control Plane (CP) and User Plane (UP), the possible deployment scenarios of NB-IoT in future Heterogeneous Wireless Networks (HetNet). Finally, existing and emerging research challenges in this direction are presented to motivate future research activities.

The fifth-generation (5G) and beyond 5G (B5G) wireless networks introduced massive machine-type communications (mMTC) to cope with the growing demand of massive Internet of things (IoT) applications. However, the heterogeneous characteristics of massive IoT and diverse quality of service (QoS) requirements may lead to severe interference that could degrade the expected QoS of the cellular ecosystem.Therefore, this paper studies the impact of interference caused by mMTC connections. We theoretically model the inter-cell interference (ICI) minimization problem for the existing orthogonal multiple access (OMA) technique and propose its corresponding solution. Furthermore, we jointly solve the ICI and the co-channel interference minimization problem for the IoT users when the non-orthogonal multiple access (NOMA) technique is used. For the proposed OMA and NOMA schemes, we design a cooperative scheduler to reduce the impact of such interference. The results show that our proposed schemes provide up to 58%, 75%, and 100% more improvements in terms of user's data rates, energy consumption, and connection density, respectively

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In this paper, we propose an inter-cell interference (ICI) minimization scheme for uplink transmission in the narrowband internet of things (NB-IoT) systems. We first establish the theoretical ICI problem formulation and propose its corresponding solution for the orthogonal multiple access (OMA) NB-IoT system. Based on the theoretical formulation, we design a cooperative radio resource scheduler that reduces the impact of ICI and allocates transmit powers to reduce the energy consumption to the scheduled users in a multi-cell scenario. We compare the performance of the proposed scheme with that of some benchmark OMA schedulers. The results show that the proposed technique significantly reduces the impact of ICI and hence is more suitable for the massive connectivity of the NB-IoT system. For example, the users operating under the proposed approach experience up to 50% reduced energy consumption when compared to the best channel quality indicator (CQI) scheme. Furthermore, 30% and 35% improvements in terms of achieved user's data rates are obtained as compared to the MaxMin and round-robin schemes, respectively.