In this paper, the system saturation throughput of the cooperative MAC with opportunistic relaying for ad hoc networks is evaluated by exploiting the proposed analytical model based on the Markov chain model of DCF. B...In this paper, the system saturation throughput of the cooperative MAC with opportunistic relaying for ad hoc networks is evaluated by exploiting the proposed analytical model based on the Markov chain model of DCF. Both of the cooperative scheme and opportunistic relaying are considered into the analytical model. Simulations are also performed to validate the proposed analytical model. Simulation results show that the cooperative MAC with opportunistic relaying can significantly improve the system performance. Furthermore, we also reveal the impact of the opportunistic relaying on the performance from the MAC layer perspectives.展开更多
In order to determine the effects of different mineral admixtures including fly ash （FA）, blast furnace slag （BFS） and metakaolin （MK） on hydration product phases from the nanoscale structure perspective, nanoin...In order to determine the effects of different mineral admixtures including fly ash （FA）, blast furnace slag （BFS） and metakaolin （MK） on hydration product phases from the nanoscale structure perspective, nanoindentation characteristics of the samples with similar 28-day strengths have been investigated. The results indicate that the volume fractions of porosity in po- rosity and hydration product phases of the samples with the same kind of mineral admixture are almost equal to each other, and are greater than that of the sample without mineral admixture. Mineral admixtures especially MK can decrease remarkably the volume fractions of CH in porosity and hydration product phases, and there exists a good linear relationship between the （AI＋Si）/Ca molar ratio of cementitious materials chemical compositions and the volume fraction of HD C-S-H gel in C-S-H gel. Therefore, it is possible to predict the volume fraction change of HD C-S-H gel in C-S-H gel by simply calculating the （AI＋Si）/Ca molar ratio of cementitious materials with similar 28-day strengths under the constant water-binder ratio.展开更多
With a cross-layer design approach, a novel random access protocol is proposed in this paper, which is based on conventional slotted ALOHA （S-ALOHA） using successive interference cancellation （SIC） technique to se...With a cross-layer design approach, a novel random access protocol is proposed in this paper, which is based on conventional slotted ALOHA （S-ALOHA） using successive interference cancellation （SIC） technique to separate collided packets and cooperative transmission to exploit the physical layer advantages. And a general theoretic analysis model is presented to obtain its throughput, which is also suitable for analyzing the performance of other protocols （such as S-ALOHA and S-ALOHA with cooperative transmission （C-ALOHA）） and is shown to be right and effective. Numerical results demonstrate that the proposed protocol can improve the maximal throughput by 190% and 132% over a Rayleigh fading channel, respectively, as compared with S-ALOHA and C-ALOHA. And the results show that our protocol can provide an effective random access method with high throughput for wireless transmission.展开更多
基金Supported by the Important National Science ＆ Technology Specific Project （No. 2010ZX03006 -002 -04） , and the National Natural Science Foundation of China （No, 60972051）.
文摘In this paper, the system saturation throughput of the cooperative MAC with opportunistic relaying for ad hoc networks is evaluated by exploiting the proposed analytical model based on the Markov chain model of DCF. Both of the cooperative scheme and opportunistic relaying are considered into the analytical model. Simulations are also performed to validate the proposed analytical model. Simulation results show that the cooperative MAC with opportunistic relaying can significantly improve the system performance. Furthermore, we also reveal the impact of the opportunistic relaying on the performance from the MAC layer perspectives.
基金supported by the National Basic Research Program of China("973"Program)(Grant No.2009CB623200)the Airport Building Research Program of Jiangsu Province China(Grant No.LKJC-11-KY-001)the Research and Application Program of China’s Ministry of Railways(Grant No.2010g004-h)
文摘In order to determine the effects of different mineral admixtures including fly ash （FA）, blast furnace slag （BFS） and metakaolin （MK） on hydration product phases from the nanoscale structure perspective, nanoindentation characteristics of the samples with similar 28-day strengths have been investigated. The results indicate that the volume fractions of porosity in po- rosity and hydration product phases of the samples with the same kind of mineral admixture are almost equal to each other, and are greater than that of the sample without mineral admixture. Mineral admixtures especially MK can decrease remarkably the volume fractions of CH in porosity and hydration product phases, and there exists a good linear relationship between the （AI＋Si）/Ca molar ratio of cementitious materials chemical compositions and the volume fraction of HD C-S-H gel in C-S-H gel. Therefore, it is possible to predict the volume fraction change of HD C-S-H gel in C-S-H gel by simply calculating the （AI＋Si）/Ca molar ratio of cementitious materials with similar 28-day strengths under the constant water-binder ratio.
基金Supported by the National Natural Science Foundation of China (Grant No. 60672079)the open research fund of National Mobile Communications Research Laboratory, Southeast University (Grant No. N200814)the Project of Natural Science Foundation of Jiangsu Province(Grant No. BK2007002)
文摘With a cross-layer design approach, a novel random access protocol is proposed in this paper, which is based on conventional slotted ALOHA （S-ALOHA） using successive interference cancellation （SIC） technique to separate collided packets and cooperative transmission to exploit the physical layer advantages. And a general theoretic analysis model is presented to obtain its throughput, which is also suitable for analyzing the performance of other protocols （such as S-ALOHA and S-ALOHA with cooperative transmission （C-ALOHA）） and is shown to be right and effective. Numerical results demonstrate that the proposed protocol can improve the maximal throughput by 190% and 132% over a Rayleigh fading channel, respectively, as compared with S-ALOHA and C-ALOHA. And the results show that our protocol can provide an effective random access method with high throughput for wireless transmission.
