Mobile communication and internet of things (IoT) applications become highly common recently and they are expected to be widely spread in the near future [1 - 4]. According to Cisco global mobile data traffic forecast [5], the global mobile data traffic for a month will be nearly 49 exabytes by the year of 2021, and the annual traffic will exceed half a zettabyte. Moreover, mobile traffic will represent 20 % of total internet protocol (IP) traffic, and 78 % of the world’s mobile data traffic will be video which need a data rate in range of 20 Mbps to watch a 4K video. Also, 75 billion IoT devices are expected to be connected to the Internet by 2025, where each device includes sensors that collect data, interact with the environment, and communicate over a network. 

To cope with these expected demands, researchers begin to direct their attention to 5G networks as a solution to provide massive data rate up to multiple Gbps and ultra-low latency in the range of 1 ms with high availability, spectral efficiency, energy efficiency, user experience, reliability and security [6 - 9]. 

This 5G networks can be enabled through one of three axes. 

1-      The first one is network densifications using heterogenous networks and interworking among licensed and un-licensed bands [10 - 12]. 

2-      The second axis is increasing the spectrum efficiency of the existing 4G network using massive MIMO and cognitive radios [13 - 15]. 

3-      Finally, immigration towards higher frequency bands such as the millimeter wave (mmWave) band [16 - 19] and the visible light (VL) band [20 - 22]. As they have unlicensed wideband spectrum. 

This is a simple thoughts about 5G network, and I will publish another ideas in this blogs in the future.