patibility with legacy LTE systems. Massive MIMO: As the extension of multi-user MIMO concept to large number of antennas at the base station, it has offered a promising solution to significantly increase the user throughput and network capacity by allowing beamformed data and control transmission and interference management. The effect of considerably increased path Introduction and Background xxix Candidate technologies Massive MIMO Full-duplex radio Flexible duplex New coding, modulation and waveforms Non-orthogonal multiple access Spectral and energy efficiency mmWave bands Unlicensed bands New spectrum Spectrum sharing Heterogonous carrier aggregation Software-defined networks New network architecture Network virtualization Ultra dense networks Cloud RAN/virtual RAN Machine to machine/infrastructure communications Mobile edge computing Figure 2 Mapping KPIs to candidate 5G technologies [2]. loss in very high frequencies is compensated by higher antenna gains (directivity), which is made possible by increasing number of antennas at the base station using adap- tive beamforming and active antenna schemes. New network architecture: NFV and cloud-based radio access and core network archi- tecture have been promising approaches to attain flexibility and versatility in 5G net- work design, where the objective is to run today's network functions, which are typically implemented on dedicated hardware, as virtualized software functions on general-purpose hardware comprising servers, storage, and hardware accelerators. This is further extended to the radio network by splitting base stations into remote radio units and baseband processing units (connected via optical fiber links, high-speed Ethernet cables, or wireless fronthaul) and pooling baseband functions in the virtualized XXX Introduction and Background Communication and Internet Mobile broadband slice Mobile broadband applications Logistics, agriculture, climate Massive MTC slice Massive MTC applications Mission-Critical loT slice Automotive (V2X), factory 5G n