ith billions of low-cost devices with long battery life. The third cornerstone targets the provision of very low latency below 1 ms with ultra-high 99.9999% reliability. 5G Technology Components The targets of 5G networks are beyond the capabilities of existing mobile networks. A number of new technologies are needed to fulfill all those targets. The main new technology components are shown in Figure 1.3. 1. New spectrum. 5G is the first mobile radio technology that is designed to operate on any frequency band between 400 MHz and 90 GHz. The low bands are needed for coverage and the high bands for high data rates and capacity. The initial 5G deploy- ments use Time Division Duplex (TDD) between 2.5 and 5.0 GHz, Frequency Divi- sion Duplex (FDD) below 2.7 GHz, and TDD at millimeter wave at 24-39 GHz. 2. Massive Multiple Input Multiple Output (MIMO) beamforming can increase spec- tral efficiency and network coverage substantially. Beamforming is more practical at higher frequencies because the antenna size is comparable to the wavelength, and the antenna size becomes smaller at higher frequencies. In practice, massive MIMO can be utilized at frequencies above 1 GHz in the base stations and at millimeter wave even in the devices. Massive MIMO will be part of 5G specifications and deployments from day 1. 1 Introduction #1 New spectrum #2 Beamforming #4 LTE dual connectivity and LTE coexistence 90 GHz 30 GHz 10 GHz #3 Network slicing #5 Cloud-optimized architecture 3 GHz 10 cm 300 MHz Gateway Figure 1.3 Key 5G technology components. 3. Network slicing. Physical and protocol layers in 5G need flexible design in order to support different use cases, different frequency bands, and to maximize the energy and spectral efficiency. Network slicing will create virtual network segments for the different services within the same 5G network. This slicing capability allows opera- tors to support different use cases and enterprise customers without having to build dedicated networks. 4. Dual connectivity and Long Term Evolution (LT