In wireless communication environment, one of measures against eavesdropping is a secret information transmission scheme. This paper focuses on the scheme using multiple-input multiple-output (MIMO) system and examines its characteristics against eavesdropping. In the proposed method information signal is handled by non-linear signal processing using artificial noise and eigenbeam space division multiplexing (E-SDM) is used to maintain the confidentiality of communication. As a result of the study, it is proved that the proposed method is effective against eavesdroppers using independent component analysis (ICA).
An alternative approach for finding an optimal set of weights for antenna arrays which effectively nulls out fully coherent interferences is presented. Since the proposed technique does not require the signal matrix to be positive semidefinite the matrix can be formed at every observation time with the instantaneous values. The optimal weights are iteratively computed in a minimum number of steps at each snapshot. It is shown that the technique can be applied to the multipath problems occurring in mobile communication where the statistics of the signals may change at every observation time.< >
It is conceivable that changing the propagation characteristics of the environment actively in some ways enables us to improve transmission performance of wireless communication channel. We call such method "Active propagation control" (APC). In this paper we analyze the channel capacity of multiple-input multiple-output (MIMO) transmission system in order to show the fundamental effectiveness of APC. The change of the propagation characteristics is realized by rotating a metal plate in a room. We calculate the channel capacity by using the two-dimensional FDTD method and evaluate the improvement of the MIMO channel capacity of APC quantitatively.
An estimation method of a received signal at a remote location using array antenna has been studied. The previous studies have shown that high estimation accuracy can be obtained assuming a multipath environment where a limited number of waves having uniform intensities arrive to a receiver. In this paper, we evaluate the estimation accuracy assuming a multipath environment where a number of waves having nonuniform intensities arrive to a receiver considering propagation.
In order to avoid interference to primary users within cognitive radio, a multi-frequency RTS/CTS scheme is studied in this paper. Assuming that channels suffer from Rayleigh fading and shadowing, we derive a closed-form of interference avoidance criterion based on multi-frequency RTS/CTS scheme
