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Time-Efficient Power Allocation Scheme for Two-Way Multi-relay Cognitive Radio Networks

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Chinese Journal of Electronics 2016年第2期25卷 357-363页

作者： ZHOU Zhikang zhu qi The Key Wireless Lab of Jiangsu Province School of Telecommunication and Information EngineeringNanjing University of Posts and Telecommunications Key Lab on Wideband Wireless Communications and Sensor Network Technology of Ministry of Education

Cooperative relaying has been emerging as a key technology in Cognitive radio(CR) networks. A two-way Amplify-and-forward(AF) based multi-relay CR network is considered, where a primary user coexists with a pair of secondary users and multiple relays. A Timeefficient sub-optimal power allocation scheme(TESOPA)based on Cauchy-Schwarz inequality is provided to maximize the total end-to-end transmission rate of the secondary system. TESOPA is proposed under maximal transmission power constraints, while ensuring the quality of service of the primary user during the whole communication process. The computational complexity is sharply decreased by using the Cauchy-Schwarz inequality. Simulation results show that the proposed TESOPA scheme performs very close to the near-optimal Interior point method based power allocation(IPMPA), especially in interference dominant networks where interference constraints play a key role in determining power allocation results instead of maximal transmission power constraints.

关键词： Power allocation Relay network Cognitive radio Amplify-and-forward Two-way communication

Network selection based on multiple attribute decision making and group decision making for heterogeneous wireless networks

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The Journal of China Universities of Posts and Telecommunications 2012年第5期19卷 92-98,114页

作者： SHI Zheng zhu qi Jiangsu Key Laboratory of Wireless Communications Nanjing University of Posts and Telecommunications Nanjing 210003 China Key Laboratory on Wideband Wireless Communications and Sensor Network Technology Ministry of Education Nanjing University of Posts and Telecommunications Nanjing 210003 China

One of the key issues for radio resources management is network selection strategy in heterogeneous scenarios. In order to provide ubiquitous service, the paper puts forward a network selection algorithm based on multiple attribute decision making （MADM） and group decision making （GDM）. Firstly, the proposed algorithm acquires attribute weights＇ vectors of the subjective and objective decision makers based on MADM, and then the two attribute weights＇ vectors are synthesized to be a new attribute weights＇ vector by using GDM. Considering that the results of GDM should be reasonable and convincible, the criterion of consistency is adopted for judging the compatibility of group judgments. More specit]cally, the algorithm takes into account not only objective attributes of networks but also the preference of subscribers and traft]c class Hence it guarantees that the subscribers can not select the networks with poor performance depending on their preference. The simulation results show that the proposed algorithm can effectively reduce the handoff number and provide subscribers with satisfactory quality of service （QoS）.

关键词： heterogeneous wireless networks group decision making compatibility criterion analytic hierarchy process entropy method

Mechanical properties and fracture behaviors on 6061 aluminum alloy under shear stress state

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Rare Metals 2011年第5期30卷 550-554页

作者： zhu Hao qi Fangjuan College of Materials Science and Engineering Shijiazhuang Tiedao University Shijiazhuang 050043 China

The mechanical properties and fracture behaviors of 6061 aluminum alloy were investigated by the tensile shear tests and in-situ tensile shear tests with tensile shear specimen devised. The results indicate that many slip bands parallel to tensile direction are produced on the surfaces of the specimens. With shear strain rates increasing, the shear yield stress and shear ultimate stress of 6061 aluminum alloy remain constant basically, but the shear fracture strain decreases obviously. The shear strain rates have no influence on the fracture surfaces. The grain boundaries of 6061 aluminum alloy are the weakest area and microcracks initiate at the grain boundaries parallel to tensile direction under shear stress. With the shear stress increasing, the microcracks extend and coalesce. The fracture of specimens is due to coalescence or shearing between the microcracks.

关键词： aluminum alloys tensile shear test mechanical properties fracture

Rapid growth of ZnO hexagonal tubes by direct microwave heating

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International Journal of Minerals,Metallurgy and Materials 2010年第1期17卷 80-85页

作者： Zhen-qi zhu Jian Zhou School of Materials Science and Technology Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Zinc oxide hexagonal tubular crystals were synthesized by direct microwave heating from ZnO powders within 5 min without any metal catalysts or transport agents. ZnO source materials were evaporated from the high-temperature zone in an enclosure, and crystals were grown on the self-source substrate in an appropriate condition. The ZnO vapor formed in the high-temperature zone can deposit and grow on the powders located in the low-temperature zone to form crystals. The scanning electron microscopy （SEM） reveals that these products are hexagonal tube crystals with 80 ~rn in diameter and 250 μm in length, having a well faceted end and side surface. A possible growth mechanism and the influence of reaction temperature on the formation of crystalline ZnO hexagonal tubes were presented. The photoluminescence （PL） exhibits strong ultraviolet emission at room temperature, indicating the potential applications in short-wave light-emitting photonic devices.

关键词： ZnO crystal microwave heating vapor growth photoluminescence (PL)

Game-theoretic spectrum sharing for cognitive radio based on the expectation of primary users

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The Journal of China Universities of Posts and Telecommunications 2010年第3期17卷 6-12页

作者： MA Liang zhu qi Jiangsu Key Laboratory of Wireless Communications Nanjing University of Posts and Telecommunications Nanjing 210003 China National Mobile Communications Research Laboratory Southeast University Nanjing 210003 China

Cognitive radio is a new intelligent wireless communication technique for remedying the shortage of spectrum resource in recent years. Secondary users have to pay when they share available spectrum with primary users while price is an important factor in the spectrum allocation. Based on the game theory, an improved pricing function is proposed by considering the expectation of primary users. In this article, expectation represents the positivity of sharing spectrum with primary users. By introducing the positivity, price not only becomes different for different secondary users, but also can be adjusted according to the positivity. It is proved that the Nash Equilibrium of the new utility function exists. The simulation results show that spectrum sharing can not only be determined by the channel quality of secondary users, but also can be adapted according to the expectation of primary users. Besides, the proposed algorithm improves the fairness of sharing.

关键词： cognitive radio game theory spectrum allocation pricing function

Heterogeneous wireless network selection algorithm based on group decision

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The Journal of China Universities of Posts and Telecommunications 2014年第3期21卷 1-9页

作者： ZHANG Shuo zhu qi Jiangsu Key Laboratory of Wireless Communications Nanjing University of Posts and Telecommunications Key Laboratory on Wideband Wireless Communications and Sensor Network Technology Nanjing University of Posts and Telecommunications

In the environment of heterogeneous wireless networks, it is vital to select a currently optimal network for applications and subscribers. The use of multiple attribute decision making （MADM） for heterogeneous network selection can provide subscribers with satisfactory service quality. Converting heterogeneous network selection into a MADM problem, the authors present an improved algorithm for MADM based on group decision theory. The algorithm combines weight vectors of multiple attribute decision making to obtain a combinational weight vector. Then the results＇ compatibility will be assessed. If they do not meet the requirements of compatibility, the judgment matrix will be modified until a comprehensive vector that satisfies compatibility requirements is produced. The vector is combined with simple weighting method （SAW） for network selection. Simulation shows that the algorithm can provide users with satisfactory quality of service （QoS）.

关键词： heterogeneous network MADM group decision compatibility

Automatic modulation classification based on the combination of clustering and neural network

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The Journal of China Universities of Posts and Telecommunications 2011年第4期18卷 13-19,38页

作者： LIUAi-sheng zhu qi Jiangsu Key Laboratory of Wireless Communications Nanjing University of Posts and Telecommunications Nanjing 210003 China Key Laboratory on Wideband Wireless Communications and Sensor Network Technology Ministry of Education Nanjing University of Posts and Telecommunications Nanjing 210003 China

In this paper, we propose a new modulation classification method based on the combination of clustering and neural network, in which a new algorithm is introduced to extract key features. In order to recognize modulation types based on the constellation diagram such as phase shift keying （PSK） and quadrature amplitude modulation （QAM）, fuzzy C-means （FCM） clustering is adopted for recovering the constellation under different number of clusters. Then cluster validity measure is applied to extract key features which discriminate between different modulation types. The features are sent to neural network so that modulation types can be recognized. In order to conquer the disadvantages of standard back propagation （BP） neural network, conjugate gradient learning algorithm of Polak-Ribiere update is employed to improve the speed of convergence and the performance of modulation recognition. Simulation results show that classification rates of the algorithm proposed in this paper are much higher than those of clustering algorithm.

关键词： modulation classification clustering BP neural network FCM

Resource allocation for NOMA based D2D underlaid cellular networks

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The Journal of China Universities of Posts and Telecommunications 2019年第6期26卷 20-29页

作者： Chi Linman zhu qi Jiangsu Key Lab of Wireless Communications Nanjing University of Posts and TelecommunicationsNanjing 210003China Engineering Research Center of Health Service System Based on Ubiquitous Wireless Networks Nanjing University of Posts and TelecommunicationsMinistry of EducationNanjing 210003China

This paper puts forward a user clustering and power allocation algorithm for non-orthogonal multiple access(NOMA) based device-to-device(D2 D) cellular system. Firstly, an optimization problem aimed at maximizing the sum-rate of the system is constructed. Since the optimization problem is a mixed-integer non-convex optimization, it is decomposed into two subproblems, namely user clustering and power allocation subproblem. In the subproblem of user clustering, the clustering algorithms of cellular user and D2 D pair are proposed respectively. In the power allocation subproblem, the gradient assisted binary search(GABS) algorithm and logarithmic approximation in successive convex approximation(SCA) are used to optimize the power of subchannel(SC) and D2 D transmitted power respectively. Finally, an efficient joint iterative algorithm is proposed for the original mixed inter non-convex non-deterministic polynomial(NP)-hard problem. The simulation results show that the proposed algorithm can effectively improve the total system rate and the larger the ratio of cellular users(CUs) to total users, the larger the total system rate.

关键词： NOMA D2D communication user clustering SCA logarithmic approximation

Cooperative automatic modulation recognition in cognitive radio

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The Journal of China Universities of Posts and Telecommunications 2010年第2期17卷 46-52,71页

作者： CHEN Mei zhu qi Jiangsu Key Laboratory of Wireless Communications Nanjing University of Posts and Telecommunications Nanjing 210003 China National Mobile Communications Research Laboratory Southeast University Nanjing 210003 China

In this article, a new effective method of cooperative modulation recognition （CMR） is proposed to recognize different modulation types of primary user for cognitive radio receivers. In the cognitive radio （CR） system, two CR users respectively send their feature parameters to the cooperative recognition center, which is composed of back propagation neural network （BPNN）. With two users＇ cooperation and the application of an error back propagation learning algorithm with momentum, the center improves the performance of modulation recognition, especially when one of the CR users＇ signal-to-noise ratio （SNR） is low. To measure the performance of the proposed method, simulations are carried out to classify different types of modulated signals corrupted by additive white Gaussian noise （AWGN）. The simulation results show that this cooperation algorithm has a better recognition performance than those without cooperation.

关键词： cooperative modulation recognition cognitive radio (CR) feature parameter neural network