As a creative and effective teaching method adopted by many countries, cooperative learning is one of the most widespread and fruitful areas in modern education theory. With the introduction of the concept of cooperat...As a creative and effective teaching method adopted by many countries, cooperative learning is one of the most widespread and fruitful areas in modern education theory. With the introduction of the concept of cooperative learning among College oral English teaching, students could undergo all-round training in English proficiency, cooperative ability, self-learning ability and sense of competition. This paper mainly focuses on how to make full use of cooperative leaning in College oral English teaching, and tries to verify that cooperative leaning is a practical and effective teaching mode which could enhance the College oral English classroom teaching quality.展开更多
The 3rd Generation Partnership Project(3GPP)defined a new architecture,called Home eNode B(HeNB).The 3GPP has also presented a protocol for communications between HeNB and core networks for mutual authentication.To re...The 3rd Generation Partnership Project(3GPP)defined a new architecture,called Home eNode B(HeNB).The 3GPP has also presented a protocol for communications between HeNB and core networks for mutual authentication.To reduce the authentication costs associated with communication,computation and energy,this paper proposes a simple and low-cost re-authentication protocol that does not compromise the provided security services.The proposed protocol uses as the re-authentication parameter a Master Session Key(MSK)that has already been computed in the initial authentication,and does not require the full initial authentication to be repeated.Moreover,the proposed protocol does not modify the 3GPP infrastructure,and is easily applied to the HeNB system.Finally,the security of the proposed protocol is verified by Automated Validation of Internet Security Protocols and Applications(AVISPA)and Burrows-Abadi-Needham(BAN)Logic;detailed evaluations of performance are also given.The analysis results illustrate that the proposed protocol can achieve at least 50%cost reduction in communication and 58%cost reduction in energy.The computational cost is also reduced by half compared with the initial authentication.展开更多
With the proliferation of small and mini drones, Drone Small Cells(DSCs) can cooperative multiple drones to provide communication service for ground users as emergency means or supplementary ones of traditional terres...With the proliferation of small and mini drones, Drone Small Cells(DSCs) can cooperative multiple drones to provide communication service for ground users as emergency means or supplementary ones of traditional terrestrial cellular networks. In this paper, we study the fundamental problem of optimizing the deployment density of DSCs to achieve the maximum coverage performance. Most related works do not consider cumulative inter-cell interference when studying the coverage performance of DSCs. First, we derive an approximate and closed-form expression of the cumulative inter-cell interference which comes from both probabilistic Line-of-Sight(Lo S) and Non-Line-of-Sight(NLo S) links. Then, we analyze the coverage performance of DSCs and derive the transcendental function of optimal deployment density to obtain the maximum coverage. Last, we propose an algorithm to get the optimal deployment density with low complexity. We conduct both field experiments and Matlab simulations to verify the correctness of theoretical analysis. In addition, we show the impact of some factors on the relation between the deployment density and coverage performance through extensive numerical simulations.展开更多
文摘As a creative and effective teaching method adopted by many countries, cooperative learning is one of the most widespread and fruitful areas in modern education theory. With the introduction of the concept of cooperative learning among College oral English teaching, students could undergo all-round training in English proficiency, cooperative ability, self-learning ability and sense of competition. This paper mainly focuses on how to make full use of cooperative leaning in College oral English teaching, and tries to verify that cooperative leaning is a practical and effective teaching mode which could enhance the College oral English classroom teaching quality.
基金supported by the China Scholarship Councilthe National Natural Science Foundation of China under Grants No. 60772136, No. 61102056+1 种基金the Fundamental Research Funds for the Central Universities under Grant No. JY10000901025the project supported by Natural Science Basic Research Plan in Shaanxi Province of China under Grant No. 2011JQ8042
文摘The 3rd Generation Partnership Project(3GPP)defined a new architecture,called Home eNode B(HeNB).The 3GPP has also presented a protocol for communications between HeNB and core networks for mutual authentication.To reduce the authentication costs associated with communication,computation and energy,this paper proposes a simple and low-cost re-authentication protocol that does not compromise the provided security services.The proposed protocol uses as the re-authentication parameter a Master Session Key(MSK)that has already been computed in the initial authentication,and does not require the full initial authentication to be repeated.Moreover,the proposed protocol does not modify the 3GPP infrastructure,and is easily applied to the HeNB system.Finally,the security of the proposed protocol is verified by Automated Validation of Internet Security Protocols and Applications(AVISPA)and Burrows-Abadi-Needham(BAN)Logic;detailed evaluations of performance are also given.The analysis results illustrate that the proposed protocol can achieve at least 50%cost reduction in communication and 58%cost reduction in energy.The computational cost is also reduced by half compared with the initial authentication.
基金supported in part by National NSF of China under Grant No.61472445,No.61631020,No.61702525 and No.61702545in part by the NSF of Jiangsu Province under Grant No.BK20140076.5
文摘With the proliferation of small and mini drones, Drone Small Cells(DSCs) can cooperative multiple drones to provide communication service for ground users as emergency means or supplementary ones of traditional terrestrial cellular networks. In this paper, we study the fundamental problem of optimizing the deployment density of DSCs to achieve the maximum coverage performance. Most related works do not consider cumulative inter-cell interference when studying the coverage performance of DSCs. First, we derive an approximate and closed-form expression of the cumulative inter-cell interference which comes from both probabilistic Line-of-Sight(Lo S) and Non-Line-of-Sight(NLo S) links. Then, we analyze the coverage performance of DSCs and derive the transcendental function of optimal deployment density to obtain the maximum coverage. Last, we propose an algorithm to get the optimal deployment density with low complexity. We conduct both field experiments and Matlab simulations to verify the correctness of theoretical analysis. In addition, we show the impact of some factors on the relation between the deployment density and coverage performance through extensive numerical simulations.
