Pilotless FS-FBMC for Flexible Spectrum Access and Sharing

The RF spectrum is increasingly congested. Filter Bank Multicarrier (FBMC) is a promising technology for fine-grained spectrum sharing and exploiting the pockets left by co-existing heterogeneous technologies. However, the use of FBMC is hindered by the lack of techniques to support its potential for flexibility and agility. We introduce a spectrum-flexible design for Frequency Spreading Filter Bank Multicarrier (FS-FBMC). The key novelty of our approach, to achieve practical flexibility, is that it does not require pilot subcarriers for its operation. Therefore it can operate over narrow pockets of spectrum as well as wider bands without the need to restructure the physical layer. This gain in agility and spectral efficiency, requires the design of new channel estimation and equalization algorithms, as virtually all existing FBMC (and OFDM) systems rely on pilot subcarriers. We introduce a novel pilotless iterative channel equalization algorithm for FS-FBMC. We implement and extensively evaluate our approach. We demonstrate its robustness, and spectral efficiency. For instance, relatively to (Wi-Fi) OFDM the pilotless feature of our system and absence of Cyclic Prefix results in 46% better spectral efficiency. We also demonstrate that our system is flexible and can scale from 156 kHz to 16 MHz, therefore able to fit in most spectrum pockets. Our system was a finalist in the DARPA Spectrum Collaboration Challenge (SC2) in 2019 (and the base of our winning team in 2017 and 2018).