Towards 5G

14New Physical-layer Waveforms for 5G

Gerhard Wunder,¹ Martin Kasparick,¹ Peter Jung,¹ Thorsten Wild,² Frank Schaich,² Yejian Chen,² Gerhard Fettweis,³ Ivan Gaspar,³ Nicola Michailow,³ Maximilian Matthé,³ Luciano Mendes,³ Dimitri Kténas,⁴ Jean-Baptiste Doré,⁴ Vincent Berg,⁴ Nicolas Cassiau,⁴ Slawomir Pietrzyk,⁵ and Mateusz Buczkowski⁵

¹ Fraunhofer Heinrich Hertz Institute, Berlin, Germany

² Alcatel Lucent Bell Labs, Stuttgart, Germany

³ Technische Universität Dresden, Dresden, Germany

⁴ CEA, LETI, Grenoble, France

⁵ IS-Wireless, Piaseczno, Poland

14.1 Why OFDM Fails

The main hypothesis of this chapter is that the underlying design principles – synchronism and orthogonality – of the PHY layer of today’s LTE-A radio access network constitute a major obstacle for the envisioned service architecture. Synchronism means that the senders operate with a common clock for their processing. Orthogonality means that no crosstalk occurs in the receiver’s waveform detection process. Often, both are related, such that some rough synchronization is required to establish orthogonality. LTE-A OFDM modulation keeps the subcarrier waveforms orthogonal even after the channel, provided the discrete Fourier transform (DFT) window can be properly adjusted by a suitable synchronization mechanism, which is then near-optimal processing in a single cell if a capacity-achieving scheme such as superposition coding is used per subcarrier. However, as soon as the orthogonality is destroyed (for example, due ...