Houtian Wang

An ant colony algorithm based on cross-layer design for routing and wavelength assignment in optical satellite networks

This paper introduces an ant colony routing and wavelength assignment algorithm based on cross-layer design (CL-ACRWA), which can overcome the adverse effects of Doppler wavelength shift on data transmission in optical satellite networks. Firstly, a cross-layer optimization model is built, which considers the Doppler wavelength shift, the transmission delay as well as wavelength-continuity constraint. Then an ant colony algorithm is utilized to solve the cross-layer optimization model, resulting in finding an optimal light path satisfying the above constraints for every connection request. The performance of CL-ACRWA is measured by the communication success probability, the convergence property and the transmission delay. Simulation results show that CL-ACRWA performs well in communication success probability and has good global search ability as well as fast convergence speed. Meanwhile, the transmission delay can meet the basic requirement of real-time transmission of business.

A decision feedback channel estimation approach of the satellite mobile communication system

In this paper we present a decision feedback channel estimation way for the mobile satellite communication system in order to improve the bit error performance. The transmission is disturbed not only by shadowing and multipath effects and additive white Gaussian noise, but also by the weather attenuation. The conventional Least Square(LS) is not well suited to detect the transmitter sequence, whereas the LS-based decision feedback is able to take into account the fading channel and therefore is able to detect the signal much better. The LS-based decision feedback channel algorithm first estimate channel response, then the estimation channel response use decision feedback estimation to get the next frame channel response. Our simulation results show that LS-based decision feedback channel estimation algorithm performs much better than the origin LS channel estimation method in terms of bit error rate(BER) with a gain of probably 1 dB.

A novel pre-coding orthogonal full diversity space-time block coding scheme for 4×4 MIMO system

In this paper we consider a novel design of space-time block code combined with pre-coding module transmission system. Theory of orthogonal designs has shown that such code cannot be simultaneously orthogonal, of rate 1, with full diversity order, for more than 2 transmit antennas. We propose in this paper a new way to overcome this limitation by adding a pre-coding module before transmitting space-time block signals, this scheme is a rate 1 coding scheme with full diversity, and is also an orthogonal one thanks to the new adding pre-coding weights.

Adaptive HPA Back-Off algorithm for interactive mobile satellite broadcasting system

In order to solve the problem of introducing additional Total Degradation (TD) in adaptive satellite system caused by fixed High Power Amplifier (HPA) operating point, the paper proposes an adaptive HPA Input Back-Off (IBO) algorithm carried out on the gateway side in the Forward Link of the system based on Adaptive Coding and Modulation (ACM) techniques. On the other hand, the traditional way of evaluation of system-level TD would cause inaccurate assessment if used in adaptive forward link satellite system, so Dynamic Real-Time Total Degradation (DRTTD) is proposed to evaluate overall system performance. Results show that, with the adaptive HPA IBO algorithm adopted, the whole system can obtain system-level DRTTD performance better. This indicates that more appropriate integral HPAs operating point can be obtained in the adaptive forward link of the interactive mobile satellite broadcasting system with the proposed adaptive HPA IBO algorithm than traditional fixed HPAs working status situation.

A novel 2D wavelength-time chaos code in optical CDMA system

Two-dimensional wavelength-time chaos code is proposed and constructed for a synchronous optical code division multiple access system. The access performance is compared between one-dimensional chaos code, WDM/chaos code and the proposed code. Comparison shows that two-dimensional wavelength-time chaos code possesses larger capacity, better spectral efficiency and bit-error ratio than WDM/chaos combinations and one-dimensional chaos code.