SISO to mmWave massive MIMO

The wireless evolution is reviewed in this chapter. By introducing the general wireless communication models in Section 2.1, the prior studies from single-input-single-output (SISO) to multi-input-multi-output (MIMO) is addressed in Section 2.3. The prior technologies and concerns of Global System for Mobile Communications in terms of the fourth generation (4G) are the main subject of Section 2.3. In Section 2.4, the emerging fifth generation (5G) studies and the massive MIMO are reviewed in addition to the energy efficiency (EE) issue, which has arisen as another important concern other than the spectrum efficiency (SE). The emerging topics in 5G are briefly introduced in Section 2.5.