Qinyu Zhang

Artificial Neural Network Based Spectrum Sensing Method for Cognitive Radio

Spectrum sensing is a key technology of cognitive radio (CR). In CR systems, the main requirement of spectrum sensing is the ability of rapid and accurate detection of the presence of the primary user. In this paper, we propose a spectrum sensing method using artificial neural network (ANN). Detailed analysis shows that the proposed scheme is appropriate to detect the signals under considerably low signal-to-noise ratio (SNR) environment and has reliable performance. Simulations also illustrate that the discussed method outperforms over previous approaches in noisy environment when sensing the spectrum for CR systems.

Design of Concatenated Fountain Code in Deep Space Communication

Fountain code is forward error correction technology for erasure channels, and proposed to solve the problems of huge delay, higher BER and probability of lost packets, asymmetric up and down link-width, intermittence of links in deep space communications. LDPC code is put into precoding in concatenated fountain encoding, and present a BP decoding enhancement algorithm using redundancies in the already received encoding blocks to improve the probability of performance of LT decoding. Compared with tradition deep space channel coding scheme, the simulation show that the concatenated fountain code has better error correcting performance and can be implemented with very low complexity to encode and decode.

QoS Based Resource Allocation for OFDM-Based Cognitive Radio Systems with Mixed Services

In this paper, a quality of service (QoS) based resource allocation for orthogonal frequency division multiplexing (OFDM)-based Cognitive Radio (CR) System with mixed services is proposed. We consider the resource allocation problem for downlink with unoccupied frequency sensed by CR users (CRUs) and total transmission power constraint of the CR base station. In mixed services CR system, the objective of the resource allocation is to ensure the QoS of real time (RT) service and improve the overall performance. We formulate the QoS based resource allocation problem which consists of both queue aware and channel aware scheduling as an optimization solution. A suboptimal with low complexity approach is suggested for practical system. Simulation results show that the proposed resource allocation algorithm performs better than existing algorithms.

An Optimal ARQ Timer Design of File Delivery Time in CFDP NAK Model

To support the file transferring in deep space communication environment, the negative acknowledgment mode of the Consultative Committee for Space Data Systems file delivery protocol was analyzed. For the single-hop point-to-point file transfer operation, a trigger method and ARQ timer setting rule was proposed for Asynchronous NAK mode, which minimized the expected time taken to transfer a file under the constraint of the throughput efficiency is maximized. Performance measures is mainly concerned for the expected file delivery time of Asynchronous NAK mode, and compared with that of Deferred NAK mode. The simulation results show that Asynchronous NAK mode has better performance in conditions.

Beam Pattern for Ultrawide-Band Impulse Signal of Linear Array in the Near Field

The beam pattern of ultrawide-band (UWB) impulse array in the near field is discussed in this paper. The basic principle of beamforming of linear array in the near field for UWB pulse is presented. Computer plots of beam patterns, such as peak amplitude pattern, peak power pattern and energy pattern are presented. The UWB nearfield array beamforming results in a directivity beam pattern having a narrow mainlobe and practically no sidelobes. The influence of every parameters, such as array length, interelement spacing, number of array elements and time duration of the pulse, to the beam patterns of a linear array for UWB Gaussian pulse is analyzed, which is useful to design a practical system. The difference of the beam patterns steering different positions in the near field is analyzed as well. According to the results, improved beam width can be achieved by either increasing the array length or decreasing the time duration of the Gaussian pulse. A reduction of the restlobe level can be achieved by either decreasing the array length or increasing the number of the array elements. However, the restlobe level in the near field beam pattern is higher than that in the far field, and it increases as the range between the source and the array decreases, which is a disadvantage to suppress the noise and interference in the near field.

Oblique Projectors-Based Blind Source Separation Using Information Maximization Principle

As a new research scope, blind signal separation (BSS) is attracting more and more interests. Independent component analysis (ICA) is an important solution to the problem of BSS, under the assumption conditions of ICA, a BSS algorithm using oblique projection operators is proposed in this paper. The autocorrelation matrix of mixing matrix is used to construct the objective function while the principle of information maximization is adopted to iterate and extract the component, and the mixing matrix can be obtained in a direct way. The description of the problem is demonstrated, and the detailed flow of the proposed method is listed. Simulation results show the suggested scheme is valid even when the weakest signal is less than -80dB to others.

LRD Traffic Predicting Based on ARMA

The prediction of long range dependence (LRD) is the critical problem in network traffic. The traditional algorithms, such as Markov model and ON/OFF model, may provide high computation cost and low precision. In this study, a novel method based on empirical mode decomposition (EMD) and ARMA model was proposed. The results show that EMD could offer the function of canceling the LRD in traffic data. After transforming LRD to SRD (short range dependence) by EMD processing, the LRD traffic data could be predicted with high accuracy and low complexity by ARMA model. Meanwhile, the results indicate the usefulness of EMD in the applications of network traffic prediction.

A Novel Transmission Scheme Based on Sine/Chirp Hybrid Carriers

In this paper, a novel hybrid carrier transmission scheme is presented, which adds a group of chirp-carrier users to tradition systems sine-carrier based, sharing same frequency and time resources. The issues of interferences between users adopting different type carriers are investigated, and interference suppression approaches based on the fractional Fourier transform (FRFT) are proposed.

One Method from LRD to SRD

Research of self-similarity has been the focus of flow prediction due to the complexity of self-similar traffic, but the LRD (long range dependence) traffic has the disadvantages of the high modeling algorithm complexity and poor precision. Therefore we tried to propose a way that can make the LRD traffic change to SRD (short range dependence) which is more simple than LRD in the field of modeling and predicting. The researchers adopted EMD (Empirical Mode Decomposition) to decompose LRD data which would be decomposed into several IMF (Intrinsic Mode Function) components. Then we found that IMF components had no longer self-similar property through theoretical analysis and simulation, thus people could use some SRD model to forecast traffic.

Composite Pulse-Multipath Channel Estimation for IR-UWB Communication System

In this paper, we develop a composite pulse-multipath channel estimation approach for impulse radio-ultra wideband (IR-UWB) system. The approach is realized by means of the nearest neighbor (NN) estimation algorithm. This reconstructed signal is subsequently used as a reference template in a correlator-based detector. The bit error rate (BER) performance of the proposed approach is analyzed and compared to that of traditional correlator-based detector. Extensive simulations show that for different propagation scenarios and transfer rates, detectors based on NN composite pulse-multipath channel estimation outperform traditional correlator-based detector.