A new measuring method of track irregularity for high-speed railway is proposed by using dual-frequency laser interference technique. The linear deviation between the phase-locked gauging head and the center line of the railway route can be calculated by comparing the phase difference variation of the laser beat signal in the test ray path and the reference ray path when the portable track inspection car is moving forward along the track. While we use laser ranging technique to measure gauge, after processing data, the static irregularity of track will be acquired by changing straightness deviation of phase-locked gauging head into straightness deviation of left-right two tracks. The method is different from the existing techniques for detecting high-speed railway irregularity, such as the inertial reference method, the measuring method of chord and the method of laser alignment; it utilized the accuracy of the time to accomplish the high-precision measurement of the space and achieved innovation in theory.
CDMA system capacity is interference limited. The multiuser transmission (MUT) with adaptive antenna arrays for the downlink direction is considered to increase system capacity and to eliminate the multiple-access interference (MAI) and the inter-symbol interference (ISI) of the CDMA system. In this paper, the angular gain of the spatial filter is modeled by a piece-line function to analysis the interference difference between the in-beam users and the out-beam users. Based on this analysis, a lower complexity MUT scheme using spatial classes is proposed for avoiding MUT computation complexity, which can achieve the nearly same performance with the conventional MUT scheme. The bit-error probability approximation of this MUT scheme is also analyzed as well. The simulation result is used to confirm the availability of this lower complexity MUT scheme.
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