In recent years, MIMO technology is used in many mobile terminals to increase channel capacity. MIMO uses multiple antennas, however, if MIMO antennas are put closely such as a small terminal, a strong mutual coupling occurred. Then it causes decreasing radiation efficiency and channel capacity.

Besides, CA technology which uses multiple frequencies is also utilized. Therefore, reducing the mutual coupling at multiple frequencies is required corresponding to CA. In the previous study, a method of adding a branch element connecting by inductor L and capacitor C has been proposed. In this paper, focusing on the relationship between the number of decoupling frequencies and current paths, we propose a novel triple-band decoupling method without connecting and confirm that the proposed model performed decoupling and increased radiation efficiency.

In this paper, we consider the problem of improving the accuracy of time difference of arrival (TDOA) and frequency difference of arrival (FDOA)-based geolocation for unknown emitters. Our approach integrates multiple geolocation results by using a recursive least mean square (RLMS) algorithm and removing outliers. Simulation results show that the proposed method improves geolocation accuracy and that gating effectively removes the outliers. For instance, if two out of 20 measurements are outliers, then the root mean square error (RMSE) of the proposed method has been reduced by 74.31% (12.84 km) compared with conventional methods.

With the spread of the WLAN, WLAN devices densely exist, and radio interferences between devices which degrade performance of WLAN systems have been increasing. In this study, we propose the WLAN system which has the transmission standby in which devices with poor channel condition wait for transmissions, and other devices can transmit frames without radio interferences from the devices which are waiting for transmissions. Simulations to evaluate transmission performance of WLAN systems show the transmission standby technique reduces radio interferences and effectively utilizes radio resources.

In this paper, we propose a semi-blind channel estimation method for faster-than-Nyquist (FTN) signaling. The proposed method combines the least-squares (LS) method using training symbols with a blind estimation method using knowledge of the pulse shape. It is shown that the proposed semi-blind method requires fewer training symbols than the LS method, and it is superior to the blind method regardless of the packing ratio of FTN signaling.