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Top1. Introduction
In the fifth generation of mobile technology 5G, a huge number of smart phones and based on IoT (Internet of Things) devices will produce a huge amount of data traffic varying from low number bytes up to numerous gigabytes. The need for high data rates come from smartphones, IoT, gaming, AR/VR (Augmented Reality / Virtual Reality, etc.). For example, devices connected to the IoT service are expected to increase by 19 percent growth rate in each year until 2023 as shown in Figure 1. Examples of IoT devices include machines, cars, sensors, meters, consumer electronics, point of sale terminals, and consumer wearables. Research has shown that the expected growth in data traffic will be in the rate of over 1,000 times over the next 10 years. Therefore, it is impossible to handle data traffic of 5G with the conventional mobile networks of today.
Figure 1. Global Mobile Data traffic since 2013 until 2023 (Ericsson Mobility Report, 2020)
Web based augmented reality (WAR) further offers a lightweight, cross-platform, and pervasive solution on the web. However, it faces more technical challenges in terms of QoE (Qiao, 2019). The emerging Mobile Edge Computing MEC paradigm provides an opportunity for the performance improvement of computationally intensive applications such as WAR. To achieve user proximity, MEC servers are deployed at both the Macro Base Station (MBS) and/or Small Base Station (SBS) which results in a dense deployment of MEC servers. Since MEC servers are densely distributed, mobile users face a user association dilemma (Dai, 2018). That is, each mobile user should determine whether or not to associate with a particular base station for offloading. The user association decision is of significant importance for offloading as it directly affects communication data rate. The user association scheme in MEC should not only consider bandwidth, power, and interference but also should take both computation data size and delay requirement of applications into consideration (Chen, 2019).
One of the most effective key technologies in 5G is using multi-tier heterogeneous networks. The existing Macrocell Base Stations (MBSs) are regularly deployed with high transmission power to provide wide-range area coverage and wireless access for mobile users (Zhang, 2014). With a shorter telecommunication area, Pico BS proceed the licensed spectrum with intermediate transmission power and offload traffic data from the Macro BS in the operation areas (Zhang, 2014), (Peng, 2015). Femto cells, that have a quite small coverage range and a very low transmission power, have the ability to supply better QoS (quality of service) and very high data rates for users associated with it. Also, the huge number of operated small cell base stations (SBSs) or Femto base stations (FBS) reduce the energy consumption in the cellular network. Consequently, this causes a great increase in the operational encumbrance of cellular network and enclose up to the green evolution of heterogeneous small cell networks.