IEEE Access Special Section Editorial: New Waveform Design and Air-Interface for Future Heterogeneous Network Towards 5G

Unprecedented levels of spectral and energy efficiency are expected from next-generation wireless networks to achieve ubiquitous communications between anybody, anything, and at any time. Fifth-generation (5G) radio access technology is expected to take a huge leap compared to the previous radio generations by supporting cognitive radio, machine type communication, and the Internet of Things, besides traditional mobile broadband access. The necessity of supporting new services targeted by 5G has made researchers to question the suitability of the orthogonal frequency-division multiplexing (OFDM) waveform as adopted in Long-Term Evolution (LTE). However, the demerits of OFDM are recognized to be its large out-of-band emissions, which affect the coexistence of asynchronous services or devices, as well as its sensitivity to phase noise, Doppler frequency shift, and large peak-to-average power ratio (PAPR). Significant research effort is currently being spent on the design and analysis of alternative solutions aimed at overcoming the inefficiencies of present waveforms. Candidate multicarrier solutions rely on different degrees of filtering to obtain lower sidelobes than OFDM, thus improving robustness to asynchronous transmission. For example, in filter bank multicarrier (FBMC) approaches, universal filter multicarrier (UFMC), and generalized frequency-division multiplexing (GFDM). Even though the mentioned solutions offer undeniable advantages in terms of spectrum containment, their suitability as 5G waveforms when considering complexity constraints, as well as realistic impairments, is still disputable. In particular, the extension to multiple-input multiple-output (MIMO) antenna transmission with multiple streams seems rather cumbersome. Thus, this will lay down an interdisciplinary research agenda that combines energy and time-efficient spectrum schemes into waveform design.