Practical Evaluation of NC-OFDM System Designs in Dynamic Spectrum Access with Narrow-Band Interference

Spectrum pooling offers increased flexibility for spectrum management and raises the spectrum usage rate in overpopulated parts of the spectrum. As a result, the noncontiguous OFDM (NC-OFDM) scheme has been proposed as an option to solve this issue. In this work, the performance of NC-OFDM will be measured and evaluated using softwaredefined radio hardware in coexistence scenarios in the TV band. Thereby, two NC-OFDM system concepts, utilizing CP-OFDM and OQAM-OFDM, are presented and the requirements for the systems in the spectrum pooling approach are discussed. The performance is compared in terms of achievable average throughput and frame error rate over SIR for both systems in different resource allocation scenarios. Here the special focus is on the frame synchronization in NC-OFDM systems. A modified version of a proposed time-domain synchronization scheme is investigated to achieve synchronization even at low SIR. The results show that the OQAM-OFDM scheme can maintain its good spectral properties and achieves robustness against narrowband interference in a setup with common software-defined radio hardware as well as delivers a higher overall throughput under low SIR conditions. The modified time-domain synchronization thereby enables the transmission even at SIR levels of -30 dB and below compared to a complete loss of connection at -10 dB using common time-domain synchronization methods.