Zhang Qinyu

Capacity analysis for secondary user in cognitive radio network

In this paper, we discuss three dynamic spectrum assignment schemes: Random Spectrum Assignment, Non-Random Spectrum Assignment and Reservation based Non-Random Spectrum Assignment. A general definition of capacity for secondary user is given. By using quasi birth and death theory, we derive the closed-form solution of secondary capacity and analyze the relationships between system parameters and capacity. Based on analysis, we get an assertion that channel reservation always leads to the decrease of capacity.

Variable bandwidth spectrum access for secondary user in cognitive radio networks

In cognitive radio networks (CRNs), how to efficiently take advantage of vacant frequency bands for secondary users (SUs) has become a key to improve quality of service (QoS). Detection error has certain impacts on spectrum access, leading to overlook vacant frequency bands or occur the collision between primary users(PUs) and SUs. Since sensing mistake is inevitable, an optimal dynamic access scheme should be based on imperfect detection outcome. Therefore we propose a variable bandwidth spectrum access scheme with imperfect spectrum sensing. In this scheme, SUs can access different amount of frequency bands by detecting spectrum resources. As soon as PUs reclaim the frequency bands, SUs adjust own frequency bands according to the state of spectrum resources, meanwhile renewing their service quality level. Considering the impact of detection error on CRNs performance, this scheme is based on imperfect sensing and modeled by three-dimension Continuous-Time Markov Chain (3D-CTMC). We give the expression of performance metrics evaluating QoS of CRNs and use QBD theory to gain the solution of steady state probability. Theory analysis and simulation experiments show that the proposed scheme efficiently improves QoS of CRNs with an acceptable degradation of SUsservice quality level, the degradation has no influence on the normal transmission of SUs.

Deterministic simulation of UWB indoor propagation channel

A site-specific model of UWB pulse propagation in indoor environment is addressed. The simulation utilizes the principles of geometrical optics (GO) for direct and reflected paths tracing and the time domain technique for describing the transient electromagnetic field reflected from wall, floor, ceiling, and objects. The polarization of the received waveform is determined by taking into account the radiation pattern of the transmitting and receiving antennas, as well as the polarization changes owing to every reflection. The model provides more intrinsical interpretations for UWB pulse propagation in realistic indoor environment.

Simulation of UWB Pulsed Indoor Propagation Channel

A simulation of UWB impulse signals propagation within an indoor non-line-of-sight (NLOS) environment is addressed in this paper. The transmitter and the receiver are placed in two rooms respectively with a concrete wall blocking the line-of-sight (LOS) propagation path. The radiation pattern and the polarization pattern of transmitting/receiving antenna are modelled. The corresponding transient electromagnetic field transmitting through as well as reflected from the wall, the floor, the ceiling, the objects, etc. are calculated in time domain. The simulation results provide the space-time distribution of received pulsed field, which give more intrinsically interpretations for the mechanics of UWB impulse signals propagation in indoor NLOS environment.

The investigation of acquisition of the UWB signals based on BP neural network

Acquisition of the signals is a key technology in the UWB system. A new method based on BP neural networks is proposed here to implement the fast acquisition of UWB signals with the condition of low SNR. The BP neural network is used to match the extreme short pulse in this study. It could improve the performance of the acquisition efficiently. In this paper, the feasibility and efficiency of the new method are discussed. The influence of the SNR in UWB system is analyzed. The simulation results highly indicate the usefulness of the method pointed out in this study.

Heterogeneous sensor networks traffic control algorithm based on CARIMA prediction

Aiming at the problems that they are slowly responded, working unstably etc. in sensor networks traffic control algorithms, we propose a traffic control algorithm based on CARIMA prediction. According to the traffic distribution, the parameter in CARIMA model are recognized online. The CARIMA predictive control sequences are obtained by objective function. The generation rates of source nodes are updated based on control sequences. Simulation results show that the proposed algorithm can effectively improve network throughput and maintain the intermediate node queue length, which achieves congestion control and improves the network QoS performance.

Routing solution of high dynamic users oriented HAPs network

To solve the routing problems caused by high dynamic movement of the users in HAPs networks, HAPNRS (HAPs network routing solution) is proposed. It consists of the method of routing establishment and data forward and the handover strategy of high dynamic users. By HAPNRS, the problems of the difficulty of looking for which subnet the user is in and the break of data transmission are solved well. It is a valid routing solution by which HAPs networks can service for the high dynamic users.