## 2 The Evolution of Wireless Communication Networks  
Following the evolution of wireless communication networks, it can be concluded that a huge leap of progression is made every decade [3; 7; 34]. The first generation was first launched in 1980 with the sole functionality of providing voice communications to the pioneer users [3; 7; 34; 63]. The 1G network was designed based on the Advanced Mobile Phone System (AMPS) technology [64] and transmissions of data were achieved through the analog modulation method [3; 65; 66]. The 1G network encountered recurrent challenges with security issues, handover concerns, and extremely low reliability, and was unable to meet wireless transmission standards [3; 65]. After about a decade, the second generation (2G) was launched [7]. The 2G network was roughly launched between 1990 and 1992 [3; 7]. The GSM, in combination with the 3 GPP, and 3 GPP2 were the groups responsible for its development [34]. The 2G network provided the first bandwidth of 25 MHz from the analog system in the previous generation [7], and proceeded to provide services such as voice and text messaging [3]. Further improvement was achieved in the network speed (64 Kbps), architecture, and key technologies. Internet connectivity was introduced in the 2G network, and the narrowband was deployed [7]. Subsequently, between 2000 and 2002, the 3G network was launched. A three-layer architecture was adopted for the third generation (3G) mobile network as it was launched in the year 2000 [3; 66; 67]. It also adopted the Code-division Multiple Access (CDMA) for its system architecture to speed up data access at 8 megabits per second (Mbps) [3]. Services such as the downloading and uploading of videos, web browsing, e-mailing services, video conferencing, paging, fax, navigational maps, and multimedia became available [3; 64; 65]. Figure 1: Review organization. The 4G network provided added services, including video streaming, VoIP, TV streaming, and internet browsing, after it was launched between 2009 and 2010 [3; 7]. Other developments in the 4G network include ultraband internet connectivity, improved latency of 10 ms, and a mobility capacity of 350 km/h [7]. System architecture evolved into the MIMO, OFDM, Long-Term Evolution (LTE), and IoT domains [3]. These were further advanced to include Massive MIMO, OFDM-based cm Wave, and NR mm Wave in the 5G network. Applications such as the Smartphone began springing up in the 4G era [3], and continued to witness tremendous growth. A major improvement that differentiates the 4G network from its 3G predecessor is the data transfer rates and security [65]. This progression can be seen from its initial inception speed of 2 kbps in the 1G network, and the progression improved to 64 kbps (2G), 8 Mbps (3G), 50 Mbps (4G), 10 Gbps (5G), and up to the expected 100 Tbps in the future (6G) [7; 65]. The 5G network extended wireless communication to include human-to-device communication [3; 68], and began supporting services such as Industry 4.0, Virtual Reality (VR), Augmented Reality (AR), IoT, automated driving, internet of vehicles (IoV), and other distance experiences such as remote working, virtual meetings, robotics, etc. [3]. The 5G era witnessed the introduction of an IP-based network architectural paradigm such as information technology (IT), network slicing [64; 67], MEC, NFV, and SDN [46]. The 6 th-generation wireless network (6G) will be characterized by high-data rates and enhanced bandwidth (THz domain), giving it 99.99% ultra-reliable and low latency communication transmission capabilities [46]. Huge improvements will be witnessed in its sensing resolution and positioning accuracy, mobility, network energy efficiency, connectivity density, and network traffic capacity as compared to the current 5G [16; 22; 52]. The 6G network will support a plethora of services ranging from massive machine-type communication (mMTC) to mixed reality (MR), and facilitate the emergence of technologies such as holographic connectivity and ubiquitous connectivity [46].