Yang Shi-zhong

An Effective Low-Complexity Method for PAPR Reduction in OFDM-Based Systems

OFDM-based system is a strong candidate for future wireless communication. One major disadvantage of OFDM is the high peak-to-average power ratios (PAPR). This paper concentrates on the PAPR reduction and proposes an effective method. In the method, the transmitted sequence in frequency domain is separated into two sequences and are implemented IFFT respectively, and one of the two sequences is cyclic shifted, and then they are added together. The OFDM symbol with minimum PAPR is transmitted. After FFT in receiver, the data only needs to be multiplied with a simple revising matrix. Simulations and computational complexity analysis show that the proposed method compared with SLM and PTS can reduce the PAPR significantly, and has lower computational complexity.

Adaptive filtering algorithm to GPS/INS integrated system

GPS/INS integrated systems have applications in the self-positioning of highly dynamic targets. This paper conceives state equations and observation equations by the integrated system and GPS observation, respectively. An adaptive filtering algorithm is introduced which estimates observation noise covariance with observation data, and estimates dynamic noise covariance by use of the Sage-Husa filtering algorithm which has faster convergence speed and better stability than the conventional Kalman filtering algorithm. Finally, simulations are given to verify the effectiveness of the algorithm.

A new technique of the multi-targets management in small satellites system

Under the operating mode of a small satellites system which uses multi-satellites or multi-constellations, more satellites exist at the same time in the view area of one TTC (telemetry tracking and command) station than in traditional systems. Obviously, it is unable to manage them by traditional methods. This paper proposes a new technique, which combines SDMA (space-division multiple access) with spread spectrum CDMA (code-division multiple access). Multi-beamforming is available by parallel data processing and one small satellite is tracked by one beam. Finally, simulation results of digital beamforming are provided.

The beamforming for an adaptive antenna system in multi-vehicles TT&C environment

In a multi-vehicle environment, a TT&C (tracking, telemetry and command) system is realized through a unified spread spectrum framework. Adaptive antenna digital beamforming technologies are used to track, measure and command objects. A constant modulus array (CMA) and an adaptive signal canceller estimate the direction of arrival (DOA) of every signal and use the optimum weighted vector to form the beams. The phase-weighted vectors estimated from the DOA improve the processing gain as well as being utilized in transmitting a tele-command signal to form the beam for a specified object. Its processing performance is researched and simulated.

All digital closed-loop FOG detection system

A new type of all digital closed-loop fiber-optic gyroscope (FOG) detection scheme named digital phase ramp feed-back is introduced. After a detailed analysis of its principle and design, a complete FOG signal detection system is developed and set-up. Experiments and tests show that the scheme can solve problems such as scale factor error and dynamic range effectively.

A modified model for multi-paths distribution under mobile environment

In mobile communication systems, objects which can reflect and scatter radio waves exist between transmitter and receiver. The relative position of these objects varies with the random movement of transmitter and receiver, making the radio waves reach the receiver via different paths. The extent of fading and distortion of the reception signals depends on the actual path distribution of the radiowave propagation. The author presents a Poisson distribution function of paths by use of two stochastic processes. The first process, which is a Poisson process, describes the paths occurring, and the second one, which is an exponential process, describes the paths standing. However, a notable error exists between the Poisson and the measurement results. The author also provides a modified Poisson model which is more consistent with the measurement model.

A method to improve the decoding iteration convergence performance of turbo codes

Based on the universal decoding method of turbo codes, a step increment factor was introduced to improve the iteration convergence performance. The method to generate the step increment factor was also presented as well as its computer simulation.

GPS/INS integrated measurement system on Earth-circling spacecraft

This paper proposes GPS/INS integrated to implement the positioning and the attitude determination of the Earth-circling spacecraft. Observability analysis shows that the integration system, in which only GPS pseudo-range and delta pseudo-range are the observable, cannot assure favorable observability of the attitude error angles. The GPS carrier phase observable can be introduced to enhance the reliability and the precision in attitude determination. Here receiver autonomous integrity monitoring (RAIM) is used to eliminate the anomalous data, so as to get an improved adaptive filtering algorithm, which has a faster convergent speed and better stability than the conventional Kalman filtering algorithm. Finally, simulations are given to verify the effectiveness of the algorithm.