Ronghua Zhou

EMD-Based Denoising of UWB-IR Signal

The empirical mode decomposition (EMD) applied to analysis of nonstationary and nonlinear signals has attracted great research interests. In this paper, a novel adaptive approach based on EMD framework is introduced to remove noise from ultra wide band impulse radio (UWB-IR) signals. Specifically, the noisy UWB-IR signal is decomposed into a finite number of oscillatory modes known as intrinsic mode functions (IMFs) and a residue. Due to different correlation characteristics of signal and noise in IMF domain, significant features of signal are improved when noise is suppressed by multiplying adjacent IMF components directly. By comparing values of original IMF with results of correlation, signal points are extracted resulting in removing noise. The proposed denoising approach is complemented by numerical examples to illustrate the efficient elimination of noise on UWB-IR signal and to demonstrate the signal-to-noise ratio (SNR) improvement induced by this approach as a performance criterion.

A QoS Routing Algorithm Based on Game Theory for Ad Hoc Networks Having Small-World Characteristics

With the development of network theory, the new science of complex networks has brought new ideas for the ad hoc network research. The small-world network has a high clustering coefficient and small average path length characteristics. This paper designs a multi-constraint QoS routing algorithm of ad hoc network having small-world characteristics. It is aimed at the dynamic environment of ad hoc network and link state information is uncertain, even ambiguous. Through Game analysis, this paper looks for the NP-complete problem of optimal or sub-optimal solution and enables users and network providers to meet the utility of Nash Equilibrium Pareto optimal. The simulation shows that the algorithm is feasible and effective.

A Novel Channel Estimation Scheme for Wideband OFDM Aeronautical Communication

The aeronautical wireless channel is a time-frequency double-selective channel, which will destroy the orthogonality of the OFDM sub-carriers remarkably, inducing a severe inter-carrier interference (ICI). The aeronautic channel is also a sparse channel. So we could utilize the property of sparseness to design an appropriate channel estimation method. In this paper, a novel channel estimation scheme is proposed for OFDM systems applied in wideband aeronautical communication. The scheme mainly consists of three parts, including the blocks of phase lock loop, channel parameters estimator, and iterative cancellation. We investigated the scheme in en-route scenarios. Simulation results were carried out to evaluate the BER performances of OFDM systems with the proposed estimation scheme.

Circuit Noise Effect on Sampling Clock in Frequency-Domain Radio Receiver IF Digitization

Quantization of the coefficients obtained by the projection of a continuous time signal over an orthogonal space is proposed recently as a new analog to digital (A/D) converting solution. The new A/D technique is to sample the input signal in orthogonal domains which may lead to reduce the degree of signal distortion and significantly less demanding A/D conversion characteristics. As a particular case, the frequency domain analog to digital converter (ADC) overcomes some of the difficulties encountered in conventional time-domain methods for A/D conversion of signals with very large bandwidths, such as ultra-wideband (UWB) signals. Analytical expressions for the A/D conversion with clock jitter error are developed. The computer simulations are presented to show the relationship between sampling clock jitter and A/D conversion performance.

Channel Estimation in MIMO-OFDM Systems by Tracking the Delay-Subspace

A time domain channel estimation method in MIMO- OFDM systems by tracking the delay-subspace is proposed. The time impulse response is estimated by transmitting known pilot symbols, and the estimation performance is improved by the Givens rotation based delay-subspace tracking and amplitudes tracking based on the LMS filtering. The simulations prove that the time domain channel estimation by tracking the delay- subspace can track faster fading channels, and is more accurate with low complexity.