## 2 Broadband System
### Fixed-Line Broadband System  
In this subsection, we review various fixed-line broadband technologies and consider their capability of meeting future broadband network requirements. Note that this subsection is not meant to present exhaustive detail on different broadband technologies. However, it is intended not only to offer the basic technology overview, but also to be an enabling background for Section 3.  
Over a century, there have been three media technologies being employed for communication. One of such extensively deployed media, being initially utilized for delivering an analog telephone line to the subscribers' premises, is a twisted-pair copper wire. It has also been employed in digital data transportation in DSL technology. With TV-wide acceptance, operators have embarked on delivering TV signals into different homes from a master antenna (the headend) deployed in the area with the aid of coaxial cable. The concept was known as the community antenna TV (CATV) system. This technology has currently evolved to the state that the cable is not only capable of transporting TV signals for the satellite but can also support voice and telephony services [104].  
Furthermore, the evolution has led to a broadband network in which optical fiber and coaxial cable are combined. This network is known as a hybrid fiber-coax (HFC) system. Some of the notable advantages of optical fiber in the network are that, compared to that of coax, it exhibits very low signal loss and high-electromagnetic immunity. Based on that, signals can be efficiently transported over a very long distance with no need for amplification. Consequently, it can be translated into better quality, improved reliability, and lower operational expenses. Moreover, evolution results in FTTH. It has been observed that, when an operator migrates from either HFC or twisted-pair network to FTTH, about 75-95% saving in the operational expense could be realized [104].  
Moreover, to deliver the 'triple play' services (i.e., voice, data, and video) on a single connection, broadband service providers have been exploiting various competing technologies for effective service provision. However, note that each of the existing technologies has related limits regarding system reliability, cost, bandwidth, and coverage. Optical fiber-based technology has different inherent advantages that are highly promising for efficient service delivery. Therefore, these make the fiber-based technology to be dominance and unmatched with other current broadband technologies. Notwithstanding, there have been notable developments in other competing technologies. Consequently, they have been able to address the ever-growing bandwidth requirements [16].  
As previously mentioned, fixed-line broadband technologies implementation depends on a direct physical connection between the operator's network and the subscriber's building. A number of broadband technologies like digital subscriber line (xDSL), cable modem, and broadband over power lines (BPL) have significantly evolved and employed the current form of subscriber connection. For instance, the cable modem systems are based on the existing HFC Cable TV networks. Furthermore, the traditional twisted copper pairs being employed for voice services by the Plain Old Telephone Service (POTS) are used in the xDSL systems. Moreover, the power lines feeding the subscriber's home or apartment are employed in the BPL technology for broadband service delivery. On the other hand, depending on the network configuration, the FTTx system demands additional installation and connection of fiber from the central office (CO) straight to or in proximity tothe subscriber. This requirement makes FTTx system deployment relatively expensive [16]. In the subsequent subsections, we consider some fixed-line broadband systems.