Timing and carrier frequency offset estimation are critical issue for OFDM cooperative communications. In view of the complexity and high accuracy requirement, 1/2 and 1/4 pilot symbol cycle CAZAC sequence structures ...Timing and carrier frequency offset estimation are critical issue for OFDM cooperative communications. In view of the complexity and high accuracy requirement, 1/2 and 1/4 pilot symbol cycle CAZAC sequence structures are defined as the pilot frequency sequence. Estimation within one symbol cycle is carried out through averaging samples of two neighboring symbol cycles, after which the operation is expanded to all the symbol cycles in one band group. Taking multipath effect into account, the concept of phase rotation is proposed for a further step. Adjust the phase difference of estimated symbols by phase rotation, and cross estimation could be done. Meanwhile, timing scheme works within one cycle training sequence. Theoretical and simulation analysis indicate that CRLB does not only relate to estimation symbol length, but also be influenced by phase difference of estimation symbols seriously. In the condition that the length of estimation is fixed, the bigger the phase rotation angle is, the smaller the CRLB is. The complexity of proposed algorithm is less than full cycle average estimation method for almost 50%. Meanwhile, the estimation accuracy is approximate with the full cycle average estimation method as well. Timing scheme with the defined preamble structure is also proposed. Simulation proves its efficiency.展开更多
A novel decentralized service composition protocol was presented based on quality of service (QoS) for mobile ad hoc networks (MANETs).A service composition in MANETs is considered as a service path discovery in a ser...A novel decentralized service composition protocol was presented based on quality of service (QoS) for mobile ad hoc networks (MANETs).A service composition in MANETs is considered as a service path discovery in a service network.Based on the concept of source routing,the protocol integrates route discovery, service discovery and service composition and utilizes a constrained flooding approach to discover the optimal service path.A service path maintenance mechanism was exploited to recover broken service paths.Simulation experiments demonstrate that the proposed protocol outperforms existing service composition protocols.展开更多
The paper study communication protocol, the structure of the circuit, antenna design of radio frequency identification technology （RFID）, and puts forward a scheme based on IOT application： RFID logistics tracking ...The paper study communication protocol, the structure of the circuit, antenna design of radio frequency identification technology （RFID）, and puts forward a scheme based on IOT application： RFID logistics tracking system. Finally, the paper study the logistics distribution center information management model from three aspects of the system design objectives, system function analysis and system architecture design based on RFID.展开更多
基金supported by the National Natural Science Foundation of China (No. 61371092 , No. 61401175)the Doctoral Fund of Ministry of Education of China (No. 20130061120062)the China Postdoctoral Science Foundation (No. 2014M551184)
文摘Timing and carrier frequency offset estimation are critical issue for OFDM cooperative communications. In view of the complexity and high accuracy requirement, 1/2 and 1/4 pilot symbol cycle CAZAC sequence structures are defined as the pilot frequency sequence. Estimation within one symbol cycle is carried out through averaging samples of two neighboring symbol cycles, after which the operation is expanded to all the symbol cycles in one band group. Taking multipath effect into account, the concept of phase rotation is proposed for a further step. Adjust the phase difference of estimated symbols by phase rotation, and cross estimation could be done. Meanwhile, timing scheme works within one cycle training sequence. Theoretical and simulation analysis indicate that CRLB does not only relate to estimation symbol length, but also be influenced by phase difference of estimation symbols seriously. In the condition that the length of estimation is fixed, the bigger the phase rotation angle is, the smaller the CRLB is. The complexity of proposed algorithm is less than full cycle average estimation method for almost 50%. Meanwhile, the estimation accuracy is approximate with the full cycle average estimation method as well. Timing scheme with the defined preamble structure is also proposed. Simulation proves its efficiency.
基金The National Natural Science Foundation of China(No.60503041)The Shanghai Commission of Science and Technology/International Cooperative Project(No.05SN07114)
文摘A novel decentralized service composition protocol was presented based on quality of service (QoS) for mobile ad hoc networks (MANETs).A service composition in MANETs is considered as a service path discovery in a service network.Based on the concept of source routing,the protocol integrates route discovery, service discovery and service composition and utilizes a constrained flooding approach to discover the optimal service path.A service path maintenance mechanism was exploited to recover broken service paths.Simulation experiments demonstrate that the proposed protocol outperforms existing service composition protocols.
文摘The paper study communication protocol, the structure of the circuit, antenna design of radio frequency identification technology （RFID）, and puts forward a scheme based on IOT application： RFID logistics tracking system. Finally, the paper study the logistics distribution center information management model from three aspects of the system design objectives, system function analysis and system architecture design based on RFID.
