We designed and successfully synthesized novel SiO x /ZnO heterostructures via one-step thermal reaction route. Orbicular SiO x dots regularly and alternately arrange in the middle of the up/down surfaces of a nanobelt to form a one-dimensional SiO x dot array, respectively, by their self-assembly. A high-resolution transmission electron microscopy study and a selected area electron diffraction pattern revealed that ZnO nanobelts are crystalline while SiO x dots are amorphous. The formation process of such heterostructure is discussed in terms of the Stranski-Krastanow growth mode of semiconductor quantum dots. Strong white luminescence was observed by bare eyes when the photoluminescence spectrum was measured.
Abstract-Spectral efficiency is one of primary concern in the design of any wireless data communications systems, where fading is the main problem. An approach that can be taken to overcome the problem of fading is to adapt the modulation scheme according to the instantaneous propagation channel conditions. In this paper, we present a simplified mathematical model to calculate the probability of SER for any given constellation of M-QAM. This model plays an important role in designing spectrally efficient adaptive modulation over nonlinear mobile channels. Instantaneous spectral efficiency and its histogram distribution are found for linear and nonlinear channel cases. The achievable spectral efficiency is obtained for linear and nonlinear channel and compared with non-adaptive system and Shannon capacity.
Spectral efficiency is one of primary concern in the design of any wireless data communications systems, where fading is the main problem. An approach that can be taken to overcome the problem of fading is to adapt the modulation scheme according to the instantaneous propagation channel conditions. In this paper, we present a simplified mathematical model to calculate the probability of SER for any given constellation of M-QAM. This model plays an important role in designing spectrally efficient adaptive modulation over nonlinear mobile channels. Instantaneous spectral efficiency and its histogram distribution are found for linear and nonlinear channel cases. The achievable spectral efficiency is obtained for linear and nonlinear channel and compared with non-adaptive system and Shannon capacity.
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