Real-time Implementation of Interference Adaptive OFDM using GNU Radio and the USRP

Software-defined radio (SDR) has emerged in recent years as the enabler of cognitive radio (CR). The easy configurability of SDR allows for quick prototyping of physical layer (PHY) and media access control layer (MAC) algorithms and features. Priced at a low cost, SDR has gained wide popularity in academic and commercial communities involved in modern wireless communications research.;In this study, we aim to explore the GNU Radio SDR platform along with the Universal Software Radio Peripheral (USRP) by implementing various wireless communications systems using open source softwares. We develop a single-carrier modulation system utilizing BPSK, QPSK, and 16-QAM modulation schemes. In addition, we analyze the orthogonal frequency domain multiplexing (OFDM) modulation system provided by GNU Radio using BPSK, QPSK, and 16-QAM modulated subcarriers. Moreover, we create an interference adaptation (IA) MAC protocol for OFDM to allocate subcarrier modulation schemes based on subchannel interference and noise levels. Real-time experiments in an open lab environment provide insight to the achievable performance of the SDR wireless communication systems. Our results show a moderate improvement in performance in terms of packet receive rate and bit error rate when IA is applied to OFDM under channel conditions where interference is present.