e Telecommunications/ICT Sector in the Twenty-First Century networks. One may note that in the 1990s only about 1% of the global population had a mobile cellular subscription and about 11% had a fixed telephone subscription. Nowa- days, mobile subscribers' penetration is near saturation, with almost everyone on this planet having a mobile phone/device. Mobile broadband is the most dynamic market segment, surpassing fixed broadband access in the second decade of the twenty-first century. The number of Internet users is also constantly growing over the entire world population (Figure 1.1). What is broadband? One may define broadband as access network bitrates and end-to-end network bitrates in both directions (downstream and upstream) which support all available types of services with satisfactory quality. For example, in the first decade of the twenty-first century broadband access meant offering hundreds of kbit/s, while a decade later it means access with Mbit/s or tens of Mbit/s (as measurement units for data speeds), enabling, for example, the provision of HD (high definition) video and ultra-HD video streaming (some of the most demanding services). Broadband can be divided into two main categories (similar to type of access net- works): Fixed broadband. Fixed broadband access technologies are provided by copper (twisted pairs) by reusing local loops deployed for fixed telephony for IP-based access via ADSL (asymmetric digital subscriber line), VDSL (very-high-bit-rate digital subscriber line), or generally X digital subscriber line (xDSL); or by cable access (by reusing coaxial cable networks, primarily developed for TV distribution, and FTTH (fiber to the home) or more general FTTx (fiber to the x), which is a long-term future for fixed broadband access in all regions. On the other side, almost all transport networks nowadays are fiber-based (accompanied by satellite networks, where optical transport is not present), SO the differences remain mainly in the last mile. Mobile broadband. Mobile broadband access