Goshi Sato, Noriki Uchida, K. Hashimoto, Y. Shibata
Through the information network recovery experience on the East Japan Great Earthquake on March 11, 2011, we learned that the combination of various existing wireless network technologies such as satellite IP network, 3G/LTE, Wi-Fi was useful in term of connectivity. In this paper, by integrating those wireless networks into a cognitive wireless network, user can use this cognitive network as an access network to Internet by selecting the best performance network among the possible network links even though the serious disaster occurred and some of those network links were seriously damaged. We also introduce an OpenFlow based access network to automatically control link selection and route selections within the cognitive wireless network to Internet by periodically monitoring evaluating their network states. In order to verify the usefulness of our proposed system, a prototype Openflow based cognitive wireless network system is constructed by connection the disaster areas in the East Japan Great Earthquake and its performance is evaluated.
{"title":"Performance Evaluation of Software Defined and Cognitive Wireless Network Based Disaster Resilient System","authors":"Goshi Sato, Noriki Uchida, K. Hashimoto, Y. Shibata","doi":"10.1109/BWCCA.2014.135","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.135","url":null,"abstract":"Through the information network recovery experience on the East Japan Great Earthquake on March 11, 2011, we learned that the combination of various existing wireless network technologies such as satellite IP network, 3G/LTE, Wi-Fi was useful in term of connectivity. In this paper, by integrating those wireless networks into a cognitive wireless network, user can use this cognitive network as an access network to Internet by selecting the best performance network among the possible network links even though the serious disaster occurred and some of those network links were seriously damaged. We also introduce an OpenFlow based access network to automatically control link selection and route selections within the cognitive wireless network to Internet by periodically monitoring evaluating their network states. In order to verify the usefulness of our proposed system, a prototype Openflow based cognitive wireless network system is constructed by connection the disaster areas in the East Japan Great Earthquake and its performance is evaluated.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127168474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chuang Ma, Yongjian Yang, Zhanwei Du, Chijun Zhang
Pocket Switched Networks represent one particular intermittent communication network for handheld mobile devices. It is an important branch of delay tolerant network with broad application areas, taken as a necessary technology for human-centered pervasive computing. Compared with traditional networks, pocket switched networks have no stable topology structure. As for the other types of delay tolerant network, the nodes in pocket switched networks follow the mobility module as human society. Thus, the routing problem of pocket switched networks is more complex, and the existing works also focus their attention in this area. Technological advances of social networks are leading to a few routing protocols for pocket switched networks. A survey of current routing solutions is presented. The development of social network for pocket switched networks is introduced as three stages. Then the routing protocols for pocket switched networks are classified based on these three stages. The details of these routing protocols are shown in this paper. At last, the article discusses the trend of social based routing protocols. This work is hopefully beneficial to the researchers from the communities of pocket switched network analysis, social network mining, and pattern matching.
{"title":"Overview of Routing Algorithm in Pocket Switched Networks","authors":"Chuang Ma, Yongjian Yang, Zhanwei Du, Chijun Zhang","doi":"10.1109/BWCCA.2014.44","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.44","url":null,"abstract":"Pocket Switched Networks represent one particular intermittent communication network for handheld mobile devices. It is an important branch of delay tolerant network with broad application areas, taken as a necessary technology for human-centered pervasive computing. Compared with traditional networks, pocket switched networks have no stable topology structure. As for the other types of delay tolerant network, the nodes in pocket switched networks follow the mobility module as human society. Thus, the routing problem of pocket switched networks is more complex, and the existing works also focus their attention in this area. Technological advances of social networks are leading to a few routing protocols for pocket switched networks. A survey of current routing solutions is presented. The development of social network for pocket switched networks is introduced as three stages. Then the routing protocols for pocket switched networks are classified based on these three stages. The details of these routing protocols are shown in this paper. At last, the article discusses the trend of social based routing protocols. This work is hopefully beneficial to the researchers from the communities of pocket switched network analysis, social network mining, and pattern matching.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124909629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we evaluate the saturation throughput and saturation delay with direct/cooperative transmission strategies. Moreover, the cost function is introduced to tradeoff the system performance to determine the optimal strategy for adopting the cooperative transmission, and then we extend the model to support applications with quality of service (QoS) requirements. In order to improve the efficiency, TXOP mechanism which allows multiple consecutive frame exchanges during the TXOP duration is defined in IEEE 802.11e standard. We show the performance in term of saturation throughput, saturation delay and total throughput of the model. Numerical results show that TXOP mechanism is generally suitable for high traffic condition environments.
{"title":"The Performance Analysis of Direct/Cooperative Transmission with TXOP Scheme in WLANs","authors":"Chien-Erh Weng, Lie Yang, Hsing-Chung Chen","doi":"10.1109/BWCCA.2014.137","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.137","url":null,"abstract":"In this paper, we evaluate the saturation throughput and saturation delay with direct/cooperative transmission strategies. Moreover, the cost function is introduced to tradeoff the system performance to determine the optimal strategy for adopting the cooperative transmission, and then we extend the model to support applications with quality of service (QoS) requirements. In order to improve the efficiency, TXOP mechanism which allows multiple consecutive frame exchanges during the TXOP duration is defined in IEEE 802.11e standard. We show the performance in term of saturation throughput, saturation delay and total throughput of the model. Numerical results show that TXOP mechanism is generally suitable for high traffic condition environments.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125072595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Yousaf, S. Ahmed, M. Akbar, N. Javaid, Z. Khan, U. Qasim
Cooperative routing is a promising technique which exploits the broadcast nature of wireless medium to enhance network performance. Sensor nodes simultaneously transmit their data on different links and utilize cooperation between nodes. In this paper, a new protocol, Co-CEStat, Cooperative Critical data transmission in Emergency for Static Wireless Body Area Networks, is proposed. The protocol utilizes the merits of both direct and cooperative transmission to achieve higher stability period and end-to-end throughput with greater network lifetime. Simulations are conducted in MATLAB to compare the Co-CEStat's performance with that of three other contemporary non-cooperative routing protocols.
{"title":"Co-CEStat: Cooperative Critical Data Transmission in Emergency in Static Wireless Body Area Network","authors":"S. Yousaf, S. Ahmed, M. Akbar, N. Javaid, Z. Khan, U. Qasim","doi":"10.1109/BWCCA.2014.54","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.54","url":null,"abstract":"Cooperative routing is a promising technique which exploits the broadcast nature of wireless medium to enhance network performance. Sensor nodes simultaneously transmit their data on different links and utilize cooperation between nodes. In this paper, a new protocol, Co-CEStat, Cooperative Critical data transmission in Emergency for Static Wireless Body Area Networks, is proposed. The protocol utilizes the merits of both direct and cooperative transmission to achieve higher stability period and end-to-end throughput with greater network lifetime. Simulations are conducted in MATLAB to compare the Co-CEStat's performance with that of three other contemporary non-cooperative routing protocols.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"384 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115220976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Admir Barolli, Tetsuya Oda, L. Barolli, F. Xhafa, M. Takizawa, V. Loia
In our previous work, we presented WMN-GA (Wireless Mesh Networks-Genetic Algorithm) system. In this paper, we use WMN-GA and analyze the simulation results considering packet delivery ratio (PDR), throughput and delay metrics. For simulations, we used ns-3 simulator and Hybrid Wireless Mesh Protocol (HWMP). We evaluate the performance of WMN for Exponential and Weibull distributions by sending multiple constant bit rate (CBR) flows and different transmission rates in the network. From simulation results, we found that for 10, 20 and 30 number of connections, the PDR is less than 60% when the transmission rate is more than 1200 kbps for Exponential distribution. The PDR for Weibull distribution is higher than Exponential distribution. For different number of connections, the throughput is increased linearly with the increasing of the transmission rate. The throughput of Exponential distribution is higher than Weibull distribution. With increasing of the number of the connections and the transmission rate, the delay is increased. For 10 connections, the delay is very small until the transmission rate is 800 kbps. The delay of Exponential distribution is smaller than that of Weibull distribution.
{"title":"Analysis of WMN-GA Simulation System Results: A Comparison Study for Node Placement in WMNs Considering Exponential and Weibull Distributions and Different Transmission Rates","authors":"Admir Barolli, Tetsuya Oda, L. Barolli, F. Xhafa, M. Takizawa, V. Loia","doi":"10.1109/BWCCA.2014.142","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.142","url":null,"abstract":"In our previous work, we presented WMN-GA (Wireless Mesh Networks-Genetic Algorithm) system. In this paper, we use WMN-GA and analyze the simulation results considering packet delivery ratio (PDR), throughput and delay metrics. For simulations, we used ns-3 simulator and Hybrid Wireless Mesh Protocol (HWMP). We evaluate the performance of WMN for Exponential and Weibull distributions by sending multiple constant bit rate (CBR) flows and different transmission rates in the network. From simulation results, we found that for 10, 20 and 30 number of connections, the PDR is less than 60% when the transmission rate is more than 1200 kbps for Exponential distribution. The PDR for Weibull distribution is higher than Exponential distribution. For different number of connections, the throughput is increased linearly with the increasing of the transmission rate. The throughput of Exponential distribution is higher than Weibull distribution. With increasing of the number of the connections and the transmission rate, the delay is increased. For 10 connections, the delay is very small until the transmission rate is 800 kbps. The delay of Exponential distribution is smaller than that of Weibull distribution.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116451129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Dang, Zheng Yan, Fei Tong, Weidong Zhang, Peng Zhang
The sharp increase of the number of mobile applications attracts special attention on mobile application trust. It becomes more and more crucial for a user to know which mobile application is trustworthy to purchase, download, install, execute and recommend. This paper presents the design and implementation of a trust-behavior based reputation system for mobile applications based on an Android platform. The system can automatically evaluate a user's trust in a mobile application based on application usage and generate application reputation according to collected individual trust information. We implement the system and evaluate its performance based on a user study. The result shows that our system is effective with regard to trust/reputation evaluation accuracy, power efficiency and system usability.
{"title":"Implementation of a Trust-Behavior Based Reputation System for Mobile Applications","authors":"T. Dang, Zheng Yan, Fei Tong, Weidong Zhang, Peng Zhang","doi":"10.1109/BWCCA.2014.52","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.52","url":null,"abstract":"The sharp increase of the number of mobile applications attracts special attention on mobile application trust. It becomes more and more crucial for a user to know which mobile application is trustworthy to purchase, download, install, execute and recommend. This paper presents the design and implementation of a trust-behavior based reputation system for mobile applications based on an Android platform. The system can automatically evaluate a user's trust in a mobile application based on application usage and generate application reputation according to collected individual trust information. We implement the system and evaluate its performance based on a user study. The result shows that our system is effective with regard to trust/reputation evaluation accuracy, power efficiency and system usability.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129527982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In software system, functional requirements are primary system requirements. Client cannot explicitly depicted security requirements and the development team is hard to understand security requirements, makes security requirements difficult to specific implant software system. In software system development process, security requirements often neglected and ignored. However, the cost of correcting security flaws in maintenance phase is over 100 times in requirements phase. Can't effectively improve the system security, enterprises loss is bound to continue to expand. In order to enhance the security of software system, this paper combines the popular software development methodology IID (Interactive and Incremental Development) with BDD (Behavior Driven Development), institutionalized requires functional requirements must be integrated into security requirements. And, using BDD process features to evaluate the major quality of security functional requirements. Timely identifies and modifies the quality defects of security functional requirements item, effectively enhance the security of software systems.
{"title":"Combining IID with BDD to Enhance the Critical Quality of Security Functional Requirements","authors":"Sen-Tarng Lai, Fang-Yie Leu, W. Chu","doi":"10.1109/BWCCA.2014.78","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.78","url":null,"abstract":"In software system, functional requirements are primary system requirements. Client cannot explicitly depicted security requirements and the development team is hard to understand security requirements, makes security requirements difficult to specific implant software system. In software system development process, security requirements often neglected and ignored. However, the cost of correcting security flaws in maintenance phase is over 100 times in requirements phase. Can't effectively improve the system security, enterprises loss is bound to continue to expand. In order to enhance the security of software system, this paper combines the popular software development methodology IID (Interactive and Incremental Development) with BDD (Behavior Driven Development), institutionalized requires functional requirements must be integrated into security requirements. And, using BDD process features to evaluate the major quality of security functional requirements. Timely identifies and modifies the quality defects of security functional requirements item, effectively enhance the security of software systems.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129735582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
For the past decade, approximate nearest neighbor (ANN) search in high dimensional space has been studied extensively. However, it supports only ANN search over palintext in traditional locality sensitive hashing (LSH). How to perform ANN search over encrypted data becomes a new challenging task. In this paper, we make an attempt to formally address the problem. We propose a new secure and efficient ANN search scheme over encrypted data based on Sorting Keys-LSH (LSH) and mutable order-preserving encryption (mOPE). In our construction, we exploit SK-LSH to generate indexes locally. While data and indexes should be outsourced to the cloud in encrypted form, which complicates computations on the encrypted data. Then, we encrypt LSH indexes using mOPE for efficient ANN search. Through rigorous security and efficiency analysis, we show that our proposed scheme is secure under the proposed model, while correctly realizing the goal of secure ANN search over encrypted data.
{"title":"Secure Approximate Nearest Neighbor Search over Encrypted Data","authors":"Yaqian Gao, Meixia Miao, Jianfeng Wang, Xiaofeng Chen","doi":"10.1109/BWCCA.2014.118","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.118","url":null,"abstract":"For the past decade, approximate nearest neighbor (ANN) search in high dimensional space has been studied extensively. However, it supports only ANN search over palintext in traditional locality sensitive hashing (LSH). How to perform ANN search over encrypted data becomes a new challenging task. In this paper, we make an attempt to formally address the problem. We propose a new secure and efficient ANN search scheme over encrypted data based on Sorting Keys-LSH (LSH) and mutable order-preserving encryption (mOPE). In our construction, we exploit SK-LSH to generate indexes locally. While data and indexes should be outsourced to the cloud in encrypted form, which complicates computations on the encrypted data. Then, we encrypt LSH indexes using mOPE for efficient ANN search. Through rigorous security and efficiency analysis, we show that our proposed scheme is secure under the proposed model, while correctly realizing the goal of secure ANN search over encrypted data.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126688604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper investigates the outage performance of dual-hop amplify-and-forward (AF) two-way relaying systems with multiple co-channel interferers at the AF relay and two noisy end-sources. For such, a tight closed-form approximation is derived for the outage probability of the considered systems. In particular, in high SIR regions, with an increasing system SIR, the outage performance does not vary with the number of interferers once the total interference power is given. Simulation results are presented to corroborate the proposed theoretical analysis.
{"title":"Outage Analysis of Interference-Limited Dual-Hop Amplify-and-Forward Bidirectional Relaying Systems","authors":"Honghang Wen, J. Ge, Jifu Wang","doi":"10.1109/BWCCA.2014.66","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.66","url":null,"abstract":"This paper investigates the outage performance of dual-hop amplify-and-forward (AF) two-way relaying systems with multiple co-channel interferers at the AF relay and two noisy end-sources. For such, a tight closed-form approximation is derived for the outage probability of the considered systems. In particular, in high SIR regions, with an increasing system SIR, the outage performance does not vary with the number of interferers once the total interference power is given. Simulation results are presented to corroborate the proposed theoretical analysis.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123887208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Application processes have to be efficiently performed on servers in a cluster with respect to not only performance but also electric energy consumption. In this paper, we consider a process migration (MG) approach to energy-efficiently performing application processes on servers in a cluster. First, a client issues an application process to a server in a cluster. A process performed on a current server is migrated to another server if the server is expected to consume smaller electric energy to perform the process than the current server and the deadline constraint on the process is satisfied on the server. In the evaluation, the total electric energy consumption of servers is shown to be smaller and the average execution time of each process to be shorter in the MG algorithm than the round robin and random algorithms.
{"title":"A Process Migration Approach to Energy-Efficient Computation in a Cluster of Servers","authors":"Dilawaer Duolikun, T. Enokido, M. Takizawa","doi":"10.1109/BWCCA.2014.63","DOIUrl":"https://doi.org/10.1109/BWCCA.2014.63","url":null,"abstract":"Application processes have to be efficiently performed on servers in a cluster with respect to not only performance but also electric energy consumption. In this paper, we consider a process migration (MG) approach to energy-efficiently performing application processes on servers in a cluster. First, a client issues an application process to a server in a cluster. A process performed on a current server is migrated to another server if the server is expected to consume smaller electric energy to perform the process than the current server and the deadline constraint on the process is satisfied on the server. In the evaluation, the total electric energy consumption of servers is shown to be smaller and the average execution time of each process to be shorter in the MG algorithm than the round robin and random algorithms.","PeriodicalId":195099,"journal":{"name":"2014 Ninth International Conference on Broadband and Wireless Computing, Communication and Applications","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123646114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：