Table 1.

The latest research directions and contributions.

Reference	Research Field	Method	Contribution
Ref. [19]	Filtered antenna system	Dual-port filtered antenna	Flat response in the passband with two sharp transmission zeros at the stopband
Ref. [20]	MIMO antenna system	Two-element MIMO antenna	Possesses salient features, e.g., polarization diversity
Ref. [21]	FPRA for UWB and CR application	A new compact reconfigurable antenna	Suitable for UWB and CR application
Ref. [22]	Idle spectrum prediction	Time series forecasting learning method	Promotion in the prediction performance
Ref. [23]	Power allocation in CR	Supermodel game power allocation method	Energy acquisition allocation scheme
Ref. [24]	CR application	A novel market-driven CR scheme	Improves spectrum utilization in radio and television frequency
Ref. [25]	CR communication and networking	CR schemes in maritime navigation	Proves the possibility of CR in maritime navigation
Ref. [26]	GNU radio and CR application	GNU radio integration in mobile communication	Highlights CR technology and explores its development prospects