Toward frequency- and energy-efficient high mobility wireless

The 1^st generation (1G) public mobile wireless networks using analog technology appeared in 1990´s. Since then, we have seen new wireless technology every decade, from 1G to 3.9G, called LTE. In a few years, we will see the 4^th generation (4G) called LTE-advanced. In the 1G and 2G networks, voice conversation was the dominant communication service. High speed data services including video are popular in 3G and will become more and more popular in 3.9G. The wireless traffic volume has been increasing rapidly by about 2 times per year. However, the available wireless bandwidth is limited. How to cope with such a rapid increase of wireless traffic while the available frequency bandwidth is limited?