Ma Zhengxin

Robust recognition of noisy speech using speech enhancement

In this paper, a robust speech recognition system in the presence of additive background noise is studied. We adopt speech enhancement as the front-end processing module to improve the signal-to-noise ratio (SNR) of the input noisy speech for recognition in the latter stage. Three different speech enhancement algorithms were tested on six types of additive noises. Experimental results show that the cascading of the speech enhancer and a hidden Markov model (HMM) based speech recognizer can significantly improve recognition accuracy in noisy environments.

Compensation of nonlinear distortion using a new method combining predistortion with reconstruction in OFDM systems

This paper presents a new method of nonlinear distortion compensation for OFDM systems. The proposed scheme compensates for the performance degradation due to the nonlinear distortion by using the combination of predistortion and reconstruction. The computer simulation results show that the proposed scheme can compensate for degradation due to the nonlinear distortion significantly. Furthermore, since the proposed scheme utilizes the iterative method, its implementation is relatively simple.

A novel carrier recovery method for CPFSK demodulation

Continuous phase frequency shift keying (CPFSK) is a power and bandwidth efficient modulation. This paper proposes a novel method for carrier recovery in CPFSK demodulation. Its complexity is very low, and it is also easy to implement, especially for software implementation. The proposed method has an excellent bit error rate performance.

Modulation index estimation for CPFSK signals and its application to timing synchronization

Modulation index is an important parameter of CPFSK (continuous phase frequency shift keying) signals, which affects the system performance significantly. In noncooperative communication systems, this index is unknown to the receiver and must be estimated. This paper proposed a fast modulation index estimation algorithm for CPFSK signals based on short time Fourier transform (STFT). Simulations show the estimation results fit the actual value well. Furthermore, this paper evaluated the performance of timing synchronization and BER using the estimated modulation index, which is near to the performance using the real index.

Link state feedback control based on linear estimation

A link feedback control scheme (LFCS) is proposed in this paper to alleviate the inaccuracy of link state information. This scheme is based on linear estimation of flow rate and feedback control between neighbor nodes. Simulation results show that, when the LFCS scheme is adopted, the stability of link state is improved and, as a result, the queuing delay and loss probability of the congestion node is reduced by an order of magnitude.

A State Stability-Based Triggered Update Mechanism for Distance Vector Algorithm

Triggered update is a common mechanism of distance vector (DV) algorithm to accelerate network convergence and alleviate routing loops. However, triggered update based on variety of absolute value of state is difficult to reflect dynamic characteristics of state fluctuations and may trigger around the trigger boundary or threshold frequently and meaninglessly. This paper proposes a state stability-based triggered update mechanism for DV algorithm (SSB-TU). SSB-TU acquires the stability variety of delay state according to second-moment-based function of statistical parameters and then generates and transfers triggered update. Computer simulation and analysis indicate that, SSB-TU can clearly reflect state fluctuation and guarantee important network performances like network throughput etc., meanwhile, timely update network state that varies distinctively and efficiently mitigate routing loops

MMC03-1: A State Stability-Based Triggered Update Mechanism for Distance Vector Algorithm

Triggered update is a common mechanism of the distance vector (DV) algorithm for the acceleration of network convergence and alleviating routing loops. But the traditional triggered update is based on the change of absolute value of state, which is difficult to reflect dynamic characteristics of state fluctuations and may trigger around the trigger boundary or threshold frequently and meaninglessly. This paper proposes a state stability-based triggered update mechanism for DV algorithm (SSB-TU). SSB-TU acquires the stability variety of delay state according to second-moment-based function of statistical parameters and then generates and transfers triggered update. Computer simulation and analysis indicate that, SSB-TU can clearly reflect state fluctuation and guarantee important network performances like network throughput, meanwhile, timely update network state that varies distinctively and efficiently mitigate routing loops.

Network state information aided scheduling algorithms with statistical guarantees

Statistical guarantee can dramatically increase the utilization of link bandwidth compared with deterministic guarantee. With aiding of network state information, scheduling schemes can reduce the probability of end-to-end delay violation and improve the overall performance. In this paper, we first investigate the single node performance of EDF (earliest deadline first) scheduler with statistical guarantees. Then based on these results, we propose two network state information aided scheduling mechanisms, named as DP-EDF and DDP-EDF, and validate their advantage over traditional EDF by both theoretical analysis and simulations.

A resource allocation method based on onboard processing for satellite ATM

The basic transport mechanism that has been defined for the broadband integrated service digital network (B-ISDN) is the asynchronous transfer mode (ATM). Recently, more and more interests are focused on satellite ATM because of its unique advantages over terrestrial networks. In this paper, a novel resource allocation method is proposed based on onboard processing, which can be implemented simply and efficiently. It uses a combination of fixed-rate and variable-rate DA (demand assignment). Simulation results show it is a useful method for a long propagation delay environment.