## 1 Introduction  
The emergence of low power consumption wireless technologies is one of the main enablers of the Internet of Thing (IoT) and the emergence of the Fifth Generation (5G) wireless standard in 2020 will be the key to IoT growth and its establishment as a tangible concept to the user. A key enabling factor for IoT traffic growth is the proliferation of wearable devices and sensors. These devices can be worn on a person and have the potential to communicate to the network directly through wireless connectivity or indirectly through a smartphone using Bluetooth, ZigBee and Wi-Fi or any other standards. Such devices include smart watches, smart glasses, smart health sensors, fitness sensors, navigation and tracking devices and so forth [1]. The huge growth of mobile traffic is generated by billions of connected devices. Moreover, the introduction of Machine Type Communications (MTC) is significantly accelerating this growth. To meet these demands, 5G must have the technologies to support such growth. MTC describes technologies, algorithms and mechanisms that enable connected devices and services to perform data transaction seamlessly without human intervention. Seamless MTC connectivity is vital, especially when the number of devices involved can be significantly large and therefore, it would be meaningful and more sensible if the MTC devices communicate directly without human intervention [2]. One of the main challenges of the future 5G network is how to handle massive MTC traffic due to billions of connected devices and machines that need wireless connectivity. In IoT, a huge number of MTC devices (billions of sensors) will need access to the network periodically to transmit their payloads with very low data rates requirements. These devices include wireless sensors, weather and environment sensors and vehicular communication [3]. In addition, there are wearable sensors that are used to measure user health status (body temperature, blood pressure and heart beat)--these wearable devices monitor the health of patients and can trigger an alert when a health issue arises. Globally, 325 million MTC wearable devices existed in 2016, where 11 million of them have embedded cellular connections. This figure is anticipated to reach 11.6 billion connected devices in 2021, exceeding the world population in that year [4]. These devices include car GPS systems and tracking devices, smart metering and utilities, health sensors that help patient's record their health status, home and office security, maintenance sensors, building automation, automotive and consumer electronic gadgets. This growth in smarter devices and MTC connections is an indication of the massive growth of IoT, which brings together people, machines, processes and data, to make mobile computing and machine connectivity very pervasive in the 5G era. MTC capabilities are experiencing an evolution from 2G to 3G, 4G and new wireless technologies. As per Cisco Virtual Network Index (VNI), the traffic size of the M2M category will dramatically increase from 0.157 Exabytes per month in 2016 to 2.224 Exabytes per month in 2021, with a Compound Annual Growth Rate (CAGR) of 70% [4], as shown in Figure 1.  
In this paper, the concept of Distributed Base Stations (DBS) with Remote Radio Units (RRUs) is adopted in order to sidestep the lack of coverage that characterises millimetre wave band (mmWave) communications, particularly in the pioneer band at 26 GHz [5]. The use of RRUs in a mobile network was originally proposed to improve the indoor coverage of a cellular network [6]. In Reference [7], RRUs were used to improve the network coverage in high data rate demands areas, the authors conducted empirical measurements regarding the links connecting the BBUs and RRUs. An algorithm was developed in Reference [8] in order to optimise the number of RRUs deployed in a network using game theory. Multipoint transmission coordination of distributed RRUs has been investigated in References [9; 10].