Wireless networks have become increasingly popular in recent decades for both residential and commercial networking. Currently, people use smart mobile devices that are fitted with a range of wireless networking interfaces to conduct short-term or long-term business, connect, socialize, and browse the Internet. Because wireless technologies and mobile devices have made amazing advancements, users need smooth, continuous, and faultless services with Quality of Service (QoS) from every origin to device at any given time while on the go or stationary. In order to accommodate the increasing traffic demands and service requirements, the next generation of wireless infrastructures (5G) paradigm will feature a high deployment of base stations and a variety of RATs, including Wireless Local, Metropolitan and Wide Area Networks (WLAN, WMAN, WWAN), Long Term Evolution (LTE), and Wireless Broadband (WiBro). However, no single RAT can simultaneously provide mobile users with high bandwidth, low latency, widespread coverage, and high QoS levels. Hence, this book chapter seeks to elucidate the varying kinds of vertical handover techniques that could be adopted to meet the demands of mobile users based on QoS and QoE.

A 2-way combined G-band differential power amplifier (PA) designed using a 130-nm SiGe BiCMOS technology is shown in this work. A differential PA is designed at 200GHz using cascode topology (CT) resulting in an overall gain and saturated output power of >27 dB and >16.5dBm respectively. To complete the design of the 2-way combined PA, a balun was also loaded with two differential PAs which improved the bandwidth to 80GHz. The area occupied by the chip of the manufactured PA was 0.55 mm2, which demonstrates a reduction of 59.25 % when compared to the existing approach. Simulation results showed that the 2-way combined G-band PA achieved a peak gain of 27dB, which showed of 4.24% increase in the gain obtained when compared with the 4-way combined PA, which was 25.9dB. Additionally, the 2-way combined G-band PA achieved a PAE value of 5.4%, which demonstrated a percentage increase of 54.2% in comparison to the 4-way combined PA, which had a PAE of 3.5%. As a result, a 3.3% decrease was observed in the DC power consumed by the 2-way combined G-band PA.