Abstract: A method forming a grating device includes: providing a substrate; entering the substrate into a process chamber; and depositing a grating material on the substrate to form a grating material layer on the substrate. A refractive index of the grating material gradually changes during depositing the grating material in the process chamber. The grating material layer includes a varying refractive index.

Abstract: A channel estimation apparatus and a method for the same are provided. The channel estimation apparatus includes a preamble buffer unit, a gain adjusting unit, a demodulation unit, and an estimation unit. The preamble buffer unit receives and temporarily stores a plurality of symbols in preamble signal. The symbols correspond to a plurality of gain control values. The gain adjusting unit adjusts the symbols to a plurality of gain normalized symbols according to the gain control values. The demodulation unit receives the gain normalized symbols and demodulates the same to obtain a frequency domain demodulation signal. The estimation unit receives the frequency domain demodulation signal and performs a channel estimation about the frequency domain demodulation signal and a frequency domain reference value of a standard preamble signal, so as to obtain a channel frequency response.

Abstract: An apparatus and a method for estimating noise power in frequency domain are provided. The apparatus and the method are applied to a state where no packet is transmitted over the channels. And the apparatus and the method acquire noise in every sub-carrier, and obtain the transmission status in every sub-channel to adjust bit-loading in every sub-carrier and improve the spectral-efficiency.

Abstract: A channel estimation apparatus and a method for the same are provided. The channel estimation apparatus includes a preamble buffer unit, a gain adjusting unit, a demodulation unit, and an estimation unit. The preamble buffer unit receives and temporarily stores a plurality of symbols in preamble signal. The symbols correspond to a plurality of gain control values. The gain adjusting unit adjusts the symbols to a plurality of gain normalized symbols according to the gain control values. The demodulation unit receives the gain normalized symbols and demodulates the same to obtain a frequency domain demodulation signal. The estimation unit receives the frequency domain demodulation signal and performs a channel estimation about the frequency domain demodulation signal and a frequency domain reference value of a standard preamble signal, so as to obtain a channel frequency response.

Abstract: An apparatus and a method for estimating noise power in frequency domain are provided. The apparatus and the method are applied to a state where no packet is transmitted over the channels. And the apparatus and the method acquire noise in every sub-carrier, and obtain the transmission status in every sub-channel to adjust bit-loading in every sub-carrier and improve the spectral-efficiency.

Abstract: Two multi-rate transmission schemes, multi-code (MC) and variable-spreading-length (VSL) code, for realizing multimedia communications on three types of OFDM-CDMA systems are proposed. These systems can be integrated into a programmable structure such that the operation can be controlled and adjusted by system parameters and thus the transceiver can be used in different systems without changing the fundamental hardware and software architecture, which serves the trend of software-radio for future application. A transceiver architecture of multi-rate OFDM-CDMA systems is illustrated and showed its programmability such that the general system can operate under different scenarios with a common hardware structure and reconfigure by software implementation.

Abstract: Two multi-rate transmission schemes, multi-code (MC) and variable-spreading-length (VSL) code, for realizing multimedia communications on three types of OFDM-CDMA systems are proposed. These systems can be integrated into a programmable structure such that the operation can be controlled and adjusted by system parameters and thus the transceiver can be used in different systems without changing the fundamental hardware and software architecture, which serves the trend of software-radio for future application. A transceiver architecture of multi-rate OFDM-CDMA systems is illustrated and showed its programmability such that the general system can operate under different scenarios with a common hardware structure and reconfigure by software implementation.