Joint PAPR and OBP Reduction for NC-OFDM Systems

The spectrum resource is always a critical issue for wireless communications since it directly impacts the data rate and capacity. However, the problem of spectrum resource scarcity always exists. Moreover, spectrum resource scarcity becomes more severe as new communication technologies and wireless applications sprout. Noncontiguous orthogonal frequency division multiplexing (NC-OFDM) is a multicarrier method for bandwidth utilization. Unfortunately, this system has two fatal defects: high peak-to-average power ratio (PAPR) and considerable out-of-band power (OBP), which are detrimental to the system's performance. To solve these two problems, we propose a convex optimization-based method for joint PAPR and OBP reduction in NC-OFDM Systems. The strategy is to permit the secondary user to utilize the unoccupied spectrum of the primary user with dynamic spectrum sharing (DSS) based on a cognitive radio network (CRN). To this end, a flexible system operating over noncontiguous bands and DSS scenarios is necessary. The simulation results have shown that our method could effectively improve the overall performance and outperform other schemes, i.e., projections onto convex sets (POCS) and alternating projections onto convex and non-convex sets (APOCNCS), without harming the transmission of the primary system. The collaboration between secondary and primary systems is viable with the proposed method.