Concerning the shortcomings in improving the sensing ability and reducing the amount of data transmission of the conventional dual-threshold cooperative spectrum sensing under the communication environment of uncertain noise, an improved dual-threshold cooperative spectrum sensing algorithm based on two-step fusion was introduced in Fusion Center (FC). Firstly, this algorithm got rid of the negative influences of some drop-out users by filtering all cognitive users. Then set the dual-threshold adaptively according to the uncertainty of the noise to strengthen the sensing adaptability of system under uncertain noise circumstance. Finally, by adopting a strategy of two-step fusion in FC, this algorithm made a compromise between the high detection ability and low amount of the data transmission. Compared with the conventional dual-threshold spectrum sensing algorithm, the theoretical analysis and simulation indicate that the proposed algorithm can not only avoid the cognitive failure and enhance the cognitive performance on the condition of a low data transmission, but also show an obvious improvement under a high noise uncertainty.
To quickly design a two-sided dipole antenna, which is used to Wireless Local Area Network (WLAN), with small size, dual-band and broadband characteristics, the dipole patch were printed on opposite sides of the dielectric substrate, and balun feed mode was used to achieve better broadband matching. Two arms of the dipole were slotted to achieve the small and dual-band characteristics, and to meet the dual-band requirements of WLAN of 2.45GHz and 5.49GHz. The size of the whole antenna is 28mm×44mm×1.6mm. And the Neural Network (NN) with electromagnetic simulation software named High Frequency Structure Simulator (HFSS) was combined to optimize the key size of the antenna and speed up the design process. The simulation results show that, when the S11 is less than -10dB, the bandwidth of the antenna in low frequency and high frequency can reach 470MHz (2.29—2.76GHz) and 3650MHz (4.96—8.61GHz) respectively; When the S11 is less than -14dB, the bandwidth of the antenna can reach 210MHz (2.36—2.57GHz) and 770MHz (5.13—5.9GHz) respectively. The pattern has good omni-direction, and the measurement and simulation results are in good consistency. The antenna can meet the requirements of WLAN.