Abstract: To address the issues of spectrum inefficiency, high throughput, and low power consumption in 5G communications, we study the spectrum efficiency and energy efficiency issues. First, 5G cognitive network model, where cognitive femtocell coexist with picocell, was built based on cooperative spectrum sensing scheme and dynamic time-division multiple-access scheduling mechanism. Then, formulate energy efficiency function and optimization problem with respect to transmission power. To resolve the non-convexity of the formulated optimization problem, Pareto-optimal solution was involved in global optimality. The simulation results show that the proposed schemes significantly enhance the energy efficiency of the cognitive femto user compared with another schemes, and ensure the accuracy and time agility of spectrum sensing.