## 2 Broadband System
### Mobile Network Evolution  
Although the path to a real mobile wireless communication system has been considerably lengthy, there has been a great evolution in the networks. The system has revolutionized from being an expensive analog signal delivery technology that can be afforded by a small number of diginitaries to ubiquitous systems being employed by a majority of people for supporting enhanced multimedia applications and services [20]. For instance, from the analog first-generation (1G) mobile communication, the digital transmission second-generation (2G) mobile networks, which are based on the global system for mobile communications (GSM) have evolved to high-speed third-generation (3G) mobile networks such as Universal Mobile Telecommunications System (UMTS) [16; 17]. The 3G systems being the first mobile networks with broadband data handling, have also evolved to the LTE, which through further evolutionary steps, subsequently developed to the true 4G systems, LTE-Advanced (LTE-A) [20; 21]. In this section, we discuss generations of mobile networks that could be considered broadband technologies. In addition, we present an overview of the mobile wireless network evolution considering features like data rates, employed technologies, supported services, and adopted multiplexing schemes, summarized in Table 6. Furthermore, a typical  
Figure 8: A typical heterogeneous database-assisted TVWS network architecture. TVA: TV Antenna, TVWS: TV white space, MSU: Macro secondary user, Macro base station (MBS), FSU: Femto secondary users, and FBS: Femto base station. cal mobile wireless network architecture that could be distributed and/or centralized is depicted in Figure 9 and explained in Section 6. 1G Mobile Systems: As previously mentioned, 1G is an analog radio transmission system. The 1G major technologies are Nordic Mobile Telephony (NMT), Advanced Mobile Phone System (AMPS), and Total Access Communication System (TACS). Note that the 1G-based mobile communication systems are limited. This is due to the fact that voice services are only supported by the system [20,21]. 2G Mobile Systems: The first analog mobile communication systems present certain challenges regarding quality and capacity. To address these challenges, the 2G digital mobile system has been developed. The standard digital 2G GSM-based mobile systems support voice, as well as limited (low) data services. Note that the GSM is a circuit-switched network in which Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) are employed to support multiple user  
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline
**Features** & **1G** & **2G** & **3G** & **4G** & **5G** & **Reference** \\ \hline Deployment & 1970-1980 & 1990–2004 & 2004–2010 & 2010–2020 & 2020 & [17,194–198] \\ \hline Switching & Circuit & Circuit, packet & Packet encoder for air interface & All packet & All packet & [17,194,199–201] \\ \hline Technology & Analog cellular: AMPS, NMT, TXS, RTDA, TACS, TACS, TACS, CSR, CPGS, PDBC, BSCP & Digital cellular: CSMS & UMTS (WCDMA), CSMS \& CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS, CS CS, CS, CS CS, CS, CS CS, CS CS, CS CS, CS CS, CS CS, CS CS CS, CS CS CS, CS CS CS CS, CS CS CS CS CS CS CS CS CS CS CS CS CS  
access at transfer rates of \(\sim\)14.4 kbps [16]. As faster rates are not supported by the related modulation technique and the GSM channel structure, the High-Speed Circuit-Switched Data (HSCSD) service is presented in the GSM Phase 2+. Furthermore, in order to permit several CA for higher speed, packet-switched functionality is added to the GSM via General Packet Radio Service (GPRS) development. Additionally, further improvement on the GSM technology with advanced modulation schemes results in the Enhanced Data rates for Global Evolution (EDGE). This helps in enhancing the data rate by about threefold in the same bandwidth.