## 1 Introduction
These capabilities will help towards the provision of services such as safe drinking water through pollution-monitoring systems (SDG 6); extending business opportunities to rural areas through sustainable city creation (SDG 11); and extending affordable Internet connectivity to hard-to-reach locations to fast-track business opportunities by bridging the digital divide gap (SDG 9). A few of the most significant challenges of IoT adoption include the selection of the most efficient, secure, and cost-effective technology that will stand the test of time in this fast-changing technology regime. Focusing on the practicality of implementation, long-term cost efficiency, feasibility, and information security as performance indices [2], the performance of each IoT technology can be ranked based on the network QoS. However, the multiplicity of different IoT options makes the development of IoT networks a very difficult task, with issues including a shared hardware infrastructure at the gateway level, and the frequent lack of global harmonisation of spectrum bands suitable for IoT applications. As proposed in this paper, a unified proof of concept IoT platform solution will reduce the number of different types of physical infrastructure required across the IoT ecosystem as the technology evolves. Despite the promises of IoT, research involving testbeds' performance of cellular IoT networks is limited. Research into cellular IoT network performance, such as that of NB-IoT, often relies on simulations and theoretical approaches. Based on network performance analysis carried out on real hardware, we evaluated NB-IoT and LoRaWAN testbeds for applications of IoT in developing countries, hard-to-reach locations, and rural localities. Using the same IoT devices (UE) as sensor nodes in the NB-IoT network and as sensor nodes and gateways in the LoRaWAN allows establishing the networks performance baseline for building a multi-tenant IoT infrastructure. Specifically, the main contributions of this work are as follows:  
* A critical review of the requirements, opportunities, and challenges of the IoT for developing countries;
* A critical review of unlicensed and cellular LPWAN technologies, focusing on security, energy utilisation, standardisation, interoperability, policy & regulation, and QoS requirements;
* Evaluation of the performance of the NB-IoT testbed and proposal of a hybrid NB-IoT and LoRaWAN proof of concept to scale IoT deployment in developing countries;
* Investigation and evaluation of the performance of LPWANs. We compared the performance of both LoRaWAN and NB-IoT in terms of transmission latency, throughput, and battery utilisation, and analysed the benefits of NB-IoT for IoT applications against unlicensed LPWAN for developing countries;
* Through the evidence of the findings, we offer recommendations on the potential benefits and drawbacks of integrating LPWANs to scale IoT deployments. The remaining parts of this paper are organised into the following sections. Section 2 presents the review of the current literature on LPWANs. Section 3 presents the main research goals. Section 4 discusses both licensed and unlicensed LPWAN IoT deployment opportunities in developing countries. Using Nigeria as a case study, a more comprehensive analysis of the technical challenges, policy regulations, spectrum, and security issues of unlicensed and cellular IoT technologies are also presented. Section 5 explains the underlying principles of low-power cellular technologies for IoT, including those of NB-IoT, EC-GSM-IoT, LTE-M, and 5G. The design framework and implementation of NB-IoT and LoRaWAN testbeds are given in Section 6 to evaluate the real-world performance of IoT networks. Through comparative analysis, results on power utilisation, security, latency, and throughput are presented in Section 7.