# Revolution or Evolution? Technical Requirements and Considerations towards 6G Mobile Communications
## 2 Evolution of Mobile Communication  
In this era of wireless communication networks, the mobile communication industry, particularly its transmission technology and frequency bands, has demonstrated outstanding growth from the mobile system to the upcoming 6G mobile system. Every generation has its specific attributes, systems, and potentials [14]. The 1G mobile network, which relies on analog transmission for speech services, started in the earlier 1980s. Back in 1979 was the first launch of the Nippon Telephone and Telegraph (NTT) cellular system provider, which started in Tokyo, Japan. Then, two years later, Europe launched its cellular system. Total Access Communication Systems (TACS), and Nordic Mobile Telephones (NMT) were the most well-known analog systems [15]. Although 1G was the first mobile system, it caused a revolution in the mobile system technologies at that time. It used an analog transmission signal which supported only voice services with a minimum data rate of up to 2.4 kbps. Additionally, it operated at a frequency range of 800-900 MHz with a bandwidth of 40 MHz and 30 kHz of channel capacity. First generation used frequency division multiplexing (FDM). Since 1G used the analog signal for transmission, there were some problems, such as low-quality calls, high energy consumption, and poor data capacity security [16]. Following that, in 1991 the second generation (2G) mobile network was introduced. Conceptually, this mobile network involves a uniform distribution of several base stations (BSs) globally to provide multiple access points (i.e., FDMA, code-division multiple access (CDMA), and time-division multiple access (TDMA)) [17] for users to communicate with one another. Accordingly, 2G technologies, such as 2G Global System for Mobile Communications (GSM), 2.5G General Packet Radio Service (GPRS), and 2.75G Enhanced Data Rates for Global Evolution (EDGE), rely on the compression-decompression algorithm (codec) [18]. Compared to 1G, 2G provided some more services, such as \"short message service\" (SMS) and \"multi-media service\" (MMS), and it provided better quality in services. In addition, 2G was upgraded to work in the frequency range of 850-1900 MHz and data rate up to 64 kbps. Second generation used TDMA and CDMA. Overall, 2G gave a better mobile communication service and encrypted data transmission using digital technology [19]. The mobile network continued to develop with the introduction of the third generation (3G). Third generation involves technical standards of IMT-2000 that incorporate elements of reliability and speed, specifically a data transfer rate of at least 200 kpbs [20]. With higher connection speed, the network transformed from a conventional mobile network to portable media devices (e.g., computers, gaming consoles, and tablets). Apart from quality internet services, 3G offers improved security through user authentication features when users connect to other wireless devices [17]. Accordingly, three fundamental technologies for the 3G network are CDMA2000, Wideband Code Division Multiple Access (WCDMA), and Time Division Synchronous Code Division Multiple Access (TD-SCDMA). Then, 4G was introduced after 3G, where users could access the network anytime and anywhere. Fourth generation is synonymous with the term \"MAGIC\", which refers to \"mobile multimedia anywhere, global mobility solutions over integrated wireless and customized services\" [14]. Through 4G, users are able to experience smooth network access and end-to-end IP transmission as well as quality of service (QoS) management with higher service quality, mobility, and a data transfer rate of 20 Mbps. The commercial application of 5G started back in 2019, after the initial complete set of 5G standards was finalized. The introduction of 5G marks the start of a global digital era with revolutionary wireless technology standards, particularly in terms of data transfer rate, latency, mobility, and even the number of connected devices [21].