In this paper, digital terrestrial multimedia broadcast (DTMB) signals and long term evolution (LTE) signals are used for hybrid positioning in urban environment. This paper mainly introduces the time of arrival (TOA) estimation of DTMB by using the method of PN sequence correlation. In the multipath environment, constant false alarm rate (CFAR) detector and matched pursuit (MP) algorithm are used to estimate the direct path. With the pseudo-range of DTMB and LTE signals, we used extended Kalman filter (EKF) to fix a position. In the experiment, the DTMB signals can be used for the supplement of LTE signals to achieve the hybrid positioning in urban environment. Compared to positioning method with LTE only, the hybrid positioning system with DTMB-LTE improved the availability of positioning by 27% over a trajectory of 600m. The 2-D position root-mean squared error (RMSE) of DTMB-LTE system was improved by 4.55m compared to the LTE positioning only over a trajectory of 438m. Furthermore, the proposed system achieved an RMSE of 26.26m over a trajectory of 162m when only 1 LTE and 1 DTMB stations were used. The hybrid positioning system with DTMB-LTE provided an RMSE of 20.45m over a trajectory of 600m.

Path fading and non-line-of-sight (NLOS) signals constitute serious problems in the wireless localization process. These problems cause unpredictable degradation in the localization precision. In this paper, a novel wireless localization approach, which is based on twice receiving array signal spectra fusions and asymmetric second-order stochastic resonance (ASSR) networks, is proposed. By combining and repetitively processing the above two techniques, the receiving signal-to-noise ratio (SNR) can be enhanced. Additionally, the receiving array signal without the line-of-sight (LOS) component can be determined and removed from the spectra fusion process. The theoretical analyses presented verify the unbiasedness and asymptotic efficiency of the proposed twice receiving spectra fusion approach. Computer simulations demonstrate that the fused spectra can significantly improve the wireless localization precision compared with conventional and up-to-date localization methods, especially under low SNR conditions.

Frequency diverse array- (FDA-) based directional modulation (DM) is a promising technique for physical layer security, due to its angle-range dependent transmit beampattern. However, the existing schemes are not suitable for the broadcasting scenario, where there are multiple legitimate users (LUs) to receive the confidential message. In this paper, we propose a novel random frequency diverse array- (RFDA-) based DM scheme to realize the point to multi-point broadcasting secure transmission in both angle and range dimension. In the first stage, the beamforming vector is designed to maximize the artificial noise (AN) power, while satisfying the power requirement of LUs for transmitting the confidential message simultaneously. In the second stage, the AN projection matrix is obtained by maximizing signal-to-interference-plus-noise ratio (SINR) at the LUs. The proposed scheme only broadcasts the confidential message to the locations of LUs while the other regions are covered by AN, which promotes the security of the wireless broadcasting system. Moreover, it is energy efficient since the power of each LU is under accurate control. Numerical simulations are presented to validate the performance of the proposed scheme.