In this paper, the analyzing approaches proposed by Zhao Dongfeng, et al.(1997) have been extensively studied. The average cyclic times of the slotted multiple access systems are analyzed by using the average cycle me...In this paper, the analyzing approaches proposed by Zhao Dongfeng, et al.(1997) have been extensively studied. The average cyclic times of the slotted multiple access systems are analyzed by using the average cycle method. Analytic formulae for mean values of a successful period and a colliding period and an idle period are derived. The upper bounds of the system throughput with capture effect and collision resolution are provided. Finally, the simulation results of the slotted multiple access channels are given.展开更多
Quorum system is a preferable model to construct distributed access control architecture, but not all quorum system can satisfy the requirements of distributed access control architecture. Aiming at the dependable pro...Quorum system is a preferable model to construct distributed access control architecture, but not all quorum system can satisfy the requirements of distributed access control architecture. Aiming at the dependable problem of authorization server in distributed system and combining the requirements of access control, a set of criterions to select and evaluate quorum system is presented. The scheme and algorithm of constructing an authorization server system based on Paths quorum system are designed, and the integrated sys- tem performance under some servers attacked is fully analyzed. Role-based access control on the Web implemented by this scheme is introduced. Analysis shows that with certain node failure probability, the scheme not only has high dependability but also can satisfy the special requirements of distributed access control such as real-time, parallelism, and consistency of security policy.展开更多
4-ary pulse amplitude modulation(4PAM) signals with 33% and 50% return-to-zero(RZ) clocks are generated for passive optical network(PON). We demonstrate that RZ-4PAM signals with duty cycles of 33% and 50% after trans...4-ary pulse amplitude modulation(4PAM) signals with 33% and 50% return-to-zero(RZ) clocks are generated for passive optical network(PON). We demonstrate that RZ-4PAM signals with duty cycles of 33% and 50% after transmission over 20-km-long single mode fiber(SMF) at 10 Gbit/s can be directly detected by using one photo detector,and the original data can also be restored by one M-ary threshold detector and one 4PAM sequence decoder. The optical spectra of 33% and 50% RZ-4PAM signals are measured,and their eye-diagrams before and after transmission are also analyzed. Simulation results show that 33% and 50% RZ-4PAM downlink signals can be received effectively,and the received power values are-15.1 d Bm and-13.8 d Bm when the bit error rate(BER) is 10^(-6). Moreover,33% RZ-4PAM optical signals have better reception performance than 50% RZ-4PAM optical signals.展开更多
A new segmented correlating decoder of synchronous optical CDMA using modified prime sequence codes is proposed. The performance of the proposed system is analyzed under the assumption of Poisson shot noise model for ...A new segmented correlating decoder of synchronous optical CDMA using modified prime sequence codes is proposed. The performance of the proposed system is analyzed under the assumption of Poisson shot noise model for the receiver photodetector. The decoder technique is shown to be more effective to improve the bit error probability performance than the method using an optical hard-limiter.展开更多
A high performance ISDN/ATM multimedia integrated access system(THMAS 1) for real time interactive distance learning is proposed in this paper. It consists of remote access units and a central access/switching dev...A high performance ISDN/ATM multimedia integrated access system(THMAS 1) for real time interactive distance learning is proposed in this paper. It consists of remote access units and a central access/switching device. At the subscriber side, the ISDN PRI interface operating at E1 line rate (2.048Mb/s) is provided directly to the termination. When the transmission medium is double of twisted pair cable which has the specification of 0.6mm/22AWG, the longest transmission distance can come to 2.6km. One remote access unit has the capacity of equivalent accessing port of 256 E1s, and the typical capacity for whole THMAS 1 system is 30720 E1 ports. Optical fiber transmission link is adopted between the remote access unit and the central device, and the peak transmission distance under no relay can reach out 60km. To the network direction, a standard ATM UNI interface at STM 1 rate (155.520Mb/s) is designed, so an ISDN/ATM hybrid access system can be constructed. THMAS 1 has the capability of n× 64kb/s (1≤n≤30) ISDN time slots conformance switching, and has the features of small volume, low power consumption, low cost, flexible to reconstructing the network as well as wide coverage of geographical access space. So it is especially suitable for the real time interactive remote teaching.展开更多
The problem of accessibility of health institution, with respect to the available facility to serve the entire population leaving in an area, can be solved using GIS. This paper presents an analysis on accessibility o...The problem of accessibility of health institution, with respect to the available facility to serve the entire population leaving in an area, can be solved using GIS. This paper presents an analysis on accessibility of healthcare facilities in Enugu urban area in a GIS environment. This was achieved through acquisition of a base map of Enugu State showing geographic extent of Enugu Urban, determining the geometric positions of health institutions in Enugu urban using handheld GPS, Creation of a spatial database of existing healthcare facilities and demonstrating through various analyses the potentials of GIS in measurement of accessibility to healthcare facilities in Enugu urban Area. The analysis includes network analysis, used to determine the closeness of a facility and shortest route to these healthcare facilities. ARCGIS 9.3 was the main software used. This was supported by Geocal for coordinate conversion and Microsoft office packages. The result of the study showed the spatial distribution of health institutions, closest facilities in case of emergency and route to those health institutions within Enugu urban Area. It was noticed that most of the healthcare facilities were located within Enugu North local government area (LGA). Other settlements and LGAs had fewer healthcare facilities. Areas deprived of healthcare facility were also identified. Routes and closest facilities to those deprived areas were identified in the settlements/area. The analysis showed the efficacy of GIS in determining accessibility of healthcare institutions in Enugu urban area. The study is thus, recommended as a spatial decision support system for decisions regarding spatial accessibility of healthcare facilities in an urban area.展开更多
In this paper,we propose a novel polling algorithm to decrease the number of idle slots and collission slots during the polling cycle by evaluating the bandwidth request of the subscribe stations(SSs) in the next poll...In this paper,we propose a novel polling algorithm to decrease the number of idle slots and collission slots during the polling cycle by evaluating the bandwidth request of the subscribe stations(SSs) in the next polling cycle for broadband wireless access(BWA) systems.We firstly analyze the feature of silent time intervals and deduce the Hurst index which symbolizes the degree of self-similarity and long-relative nature.Then we represent the inactive OFF time intervals by the Pareto model and estimate the shape parameterαby the group measured data.Finally we can evaluate the transmission probability of a silent SS before the next polling cycle. By this algorithm,we can find the optimal transmission opportunities for the base station(BS) to achieve the least collision or void timeslots in order to achieve the largest bandwidth efficiency.The theoretical analysis and simulation results show that this polling algorithm can improve the performance for BWA system.展开更多
This paper deals with the design of an intelligent access control system based on the fingerprint sensor FPC- 1011C. The design uses the S3C2410 and TMS320VC5510A as the system processor. A fingerprint acquisition mod...This paper deals with the design of an intelligent access control system based on the fingerprint sensor FPC- 1011C. The design uses the S3C2410 and TMS320VC5510A as the system processor. A fingerprint acquisition module and a wireless alarm module were designed by using the fingerprint sensor FPC1011C and GPRS module SIM100 respectively. The whole system was implemented wireless alarm through messages and GPRS-Internet in the GSM/GPRS web. In order to achieve the simple and high Real-time system, the μC-Linux system migration was also implemented.展开更多
A description of the Systems Dynamics paradigm is given and the reduced Qualitative System Dynamics (QSD) form explained. A simple example is given to illustrate the diagram construction. The principles of states (lev...A description of the Systems Dynamics paradigm is given and the reduced Qualitative System Dynamics (QSD) form explained. A simple example is given to illustrate the diagram construction. The principles of states (levels), rates and feedback loops are outlined. The QSD method is used to address the problem of accessibility by using human control of automation as an example, and applying the QSD method to evaluate the effects of the researcher and user in the de- sign of an accessible artefact. This simple automation model illustrates what can be found out from such a picture, in this indicating how the feedback from users has an influence on the time to deliver such designs.展开更多
In this article, the peak to average power ratio (PAPR) performance of 8 quadrature amplitude modulation-orthogonal frequency division multiplexing (8QAM-OFDM) optical signals has been researched in broadband optical ...In this article, the peak to average power ratio (PAPR) performance of 8 quadrature amplitude modulation-orthogonal frequency division multiplexing (8QAM-OFDM) optical signals has been researched in broadband optical access system. The complementary cumulative distribution functions (CCDFs) are analyzed of two different 8QAM-OFDMsignals with 16, 32, 64, 128, 256, 512 sub- carriers by simulation. The simulation results show that, with the increase of the number of subcarrier, the PAPR value becomes higher. When the numbers of subcarrier are16 and 512, the PAPR of 8QAM-OFDM optical signals are smaller than 5.2 dB and 5.3 dB respectively. Hence, the number of sub-carriers should be chosen according to practical application.展开更多
In this letter, we present the generation, the balanced detection, and the transmission performance evaluation of dual polarization differential quadrature phase shift keying (DP-DQPSK) signals in optical access syste...In this letter, we present the generation, the balanced detection, and the transmission performance evaluation of dual polarization differential quadrature phase shift keying (DP-DQPSK) signals in optical access system integrated with fiber and free-space downlink. Polarization-multip- lexed (POLMUX) technique is introduced in the system for high spectral efficiency access utilization. 10 Gb/s DP-DQPSK downlink signals are successfully transmitted over 50 km SMF-28 and a 800 m wireless optical channel under the bad weather condition, such as fog and haze. The results show that the potentiality of DP-DQPSK optical access system is integrated with fiber and free- space downlink for providing flexible user access with high bandwidth efficiency.展开更多
文摘In this paper, the analyzing approaches proposed by Zhao Dongfeng, et al.(1997) have been extensively studied. The average cyclic times of the slotted multiple access systems are analyzed by using the average cycle method. Analytic formulae for mean values of a successful period and a colliding period and an idle period are derived. The upper bounds of the system throughput with capture effect and collision resolution are provided. Finally, the simulation results of the slotted multiple access channels are given.
基金Supported by the National Natural Science Foundation of China (70771043, 60873225, 60773191)
文摘Quorum system is a preferable model to construct distributed access control architecture, but not all quorum system can satisfy the requirements of distributed access control architecture. Aiming at the dependable problem of authorization server in distributed system and combining the requirements of access control, a set of criterions to select and evaluate quorum system is presented. The scheme and algorithm of constructing an authorization server system based on Paths quorum system are designed, and the integrated sys- tem performance under some servers attacked is fully analyzed. Role-based access control on the Web implemented by this scheme is introduced. Analysis shows that with certain node failure probability, the scheme not only has high dependability but also can satisfy the special requirements of distributed access control such as real-time, parallelism, and consistency of security policy.
基金supported by the National Natural Science Foundation of China(No.61107064)the Chongqing University Innovation Team Founding(No.KJTD201320)+3 种基金the Natural Science Foundation of Chongqing Science & Technology Commission(Nos.cstc2014jcyj A40046 and cstc2016jcyj A1233)the Science and Technology Special Funds of Wanzhou District in Chongqing Citythe Chongqing Graduate Student Research Innovation Project(No.CYS15225)the Chongqing Three Gorges University Graduate Scientific Research Innovation Project
文摘4-ary pulse amplitude modulation(4PAM) signals with 33% and 50% return-to-zero(RZ) clocks are generated for passive optical network(PON). We demonstrate that RZ-4PAM signals with duty cycles of 33% and 50% after transmission over 20-km-long single mode fiber(SMF) at 10 Gbit/s can be directly detected by using one photo detector,and the original data can also be restored by one M-ary threshold detector and one 4PAM sequence decoder. The optical spectra of 33% and 50% RZ-4PAM signals are measured,and their eye-diagrams before and after transmission are also analyzed. Simulation results show that 33% and 50% RZ-4PAM downlink signals can be received effectively,and the received power values are-15.1 d Bm and-13.8 d Bm when the bit error rate(BER) is 10^(-6). Moreover,33% RZ-4PAM optical signals have better reception performance than 50% RZ-4PAM optical signals.
文摘A new segmented correlating decoder of synchronous optical CDMA using modified prime sequence codes is proposed. The performance of the proposed system is analyzed under the assumption of Poisson shot noise model for the receiver photodetector. The decoder technique is shown to be more effective to improve the bit error probability performance than the method using an optical hard-limiter.
文摘A high performance ISDN/ATM multimedia integrated access system(THMAS 1) for real time interactive distance learning is proposed in this paper. It consists of remote access units and a central access/switching device. At the subscriber side, the ISDN PRI interface operating at E1 line rate (2.048Mb/s) is provided directly to the termination. When the transmission medium is double of twisted pair cable which has the specification of 0.6mm/22AWG, the longest transmission distance can come to 2.6km. One remote access unit has the capacity of equivalent accessing port of 256 E1s, and the typical capacity for whole THMAS 1 system is 30720 E1 ports. Optical fiber transmission link is adopted between the remote access unit and the central device, and the peak transmission distance under no relay can reach out 60km. To the network direction, a standard ATM UNI interface at STM 1 rate (155.520Mb/s) is designed, so an ISDN/ATM hybrid access system can be constructed. THMAS 1 has the capability of n× 64kb/s (1≤n≤30) ISDN time slots conformance switching, and has the features of small volume, low power consumption, low cost, flexible to reconstructing the network as well as wide coverage of geographical access space. So it is especially suitable for the real time interactive remote teaching.
文摘The problem of accessibility of health institution, with respect to the available facility to serve the entire population leaving in an area, can be solved using GIS. This paper presents an analysis on accessibility of healthcare facilities in Enugu urban area in a GIS environment. This was achieved through acquisition of a base map of Enugu State showing geographic extent of Enugu Urban, determining the geometric positions of health institutions in Enugu urban using handheld GPS, Creation of a spatial database of existing healthcare facilities and demonstrating through various analyses the potentials of GIS in measurement of accessibility to healthcare facilities in Enugu urban Area. The analysis includes network analysis, used to determine the closeness of a facility and shortest route to these healthcare facilities. ARCGIS 9.3 was the main software used. This was supported by Geocal for coordinate conversion and Microsoft office packages. The result of the study showed the spatial distribution of health institutions, closest facilities in case of emergency and route to those health institutions within Enugu urban Area. It was noticed that most of the healthcare facilities were located within Enugu North local government area (LGA). Other settlements and LGAs had fewer healthcare facilities. Areas deprived of healthcare facility were also identified. Routes and closest facilities to those deprived areas were identified in the settlements/area. The analysis showed the efficacy of GIS in determining accessibility of healthcare institutions in Enugu urban area. The study is thus, recommended as a spatial decision support system for decisions regarding spatial accessibility of healthcare facilities in an urban area.
基金the National Natural Science Foundation of China(No.60675024)the Natural Science Foundation of Shandong(No.Y2008G37) the Soft Science Foundation of Shandong(No.2010RKGA1033)
文摘In this paper,we propose a novel polling algorithm to decrease the number of idle slots and collission slots during the polling cycle by evaluating the bandwidth request of the subscribe stations(SSs) in the next polling cycle for broadband wireless access(BWA) systems.We firstly analyze the feature of silent time intervals and deduce the Hurst index which symbolizes the degree of self-similarity and long-relative nature.Then we represent the inactive OFF time intervals by the Pareto model and estimate the shape parameterαby the group measured data.Finally we can evaluate the transmission probability of a silent SS before the next polling cycle. By this algorithm,we can find the optimal transmission opportunities for the base station(BS) to achieve the least collision or void timeslots in order to achieve the largest bandwidth efficiency.The theoretical analysis and simulation results show that this polling algorithm can improve the performance for BWA system.
文摘This paper deals with the design of an intelligent access control system based on the fingerprint sensor FPC- 1011C. The design uses the S3C2410 and TMS320VC5510A as the system processor. A fingerprint acquisition module and a wireless alarm module were designed by using the fingerprint sensor FPC1011C and GPRS module SIM100 respectively. The whole system was implemented wireless alarm through messages and GPRS-Internet in the GSM/GPRS web. In order to achieve the simple and high Real-time system, the μC-Linux system migration was also implemented.
文摘A description of the Systems Dynamics paradigm is given and the reduced Qualitative System Dynamics (QSD) form explained. A simple example is given to illustrate the diagram construction. The principles of states (levels), rates and feedback loops are outlined. The QSD method is used to address the problem of accessibility by using human control of automation as an example, and applying the QSD method to evaluate the effects of the researcher and user in the de- sign of an accessible artefact. This simple automation model illustrates what can be found out from such a picture, in this indicating how the feedback from users has an influence on the time to deliver such designs.
文摘In this article, the peak to average power ratio (PAPR) performance of 8 quadrature amplitude modulation-orthogonal frequency division multiplexing (8QAM-OFDM) optical signals has been researched in broadband optical access system. The complementary cumulative distribution functions (CCDFs) are analyzed of two different 8QAM-OFDMsignals with 16, 32, 64, 128, 256, 512 sub- carriers by simulation. The simulation results show that, with the increase of the number of subcarrier, the PAPR value becomes higher. When the numbers of subcarrier are16 and 512, the PAPR of 8QAM-OFDM optical signals are smaller than 5.2 dB and 5.3 dB respectively. Hence, the number of sub-carriers should be chosen according to practical application.
文摘In this letter, we present the generation, the balanced detection, and the transmission performance evaluation of dual polarization differential quadrature phase shift keying (DP-DQPSK) signals in optical access system integrated with fiber and free-space downlink. Polarization-multip- lexed (POLMUX) technique is introduced in the system for high spectral efficiency access utilization. 10 Gb/s DP-DQPSK downlink signals are successfully transmitted over 50 km SMF-28 and a 800 m wireless optical channel under the bad weather condition, such as fog and haze. The results show that the potentiality of DP-DQPSK optical access system is integrated with fiber and free- space downlink for providing flexible user access with high bandwidth efficiency.
