The IEEE 802.11e standard is proposed to provide QoS support in WLAN by providing prioritized differentiation of traffic. Since all the stations in the same priority access category (AC) have the same set of parameter...The IEEE 802.11e standard is proposed to provide QoS support in WLAN by providing prioritized differentiation of traffic. Since all the stations in the same priority access category (AC) have the same set of parameters, when the number of stations increases, the probability of different stations in the same AC choosing the same values will increase, which will result in collisions. Random adaptive MAC (medium access control) parameters scheme (RAMPS) is proposed, which uses random adaptive MAC differentiation parameters instead of the static ones used in the 802.11e standard. The performance of RAMPS is compared with that of enhanced distributed coordination access (EDCA) using NS2. The results show that RAMPS can reduce collision rate of the AC and improve the throughput by using adaptive random contention window size and inter-frame spacing values. RAMPS ensures that at any given time, several flows of the same priority have different MAC parameter values. By using the random offset for the inter-frame spacing value and the backoff time, RAMPS can provide intra-AC differentiation. The simulation results show that RAMPS outperforms EDCA in terms of both throughput and end-to-end delay irrespective of the traffic load.展开更多
The difference between the college English reading and writing class which is supported by network and the traditional courses is that teachers and students use information technology to complete the study task and ac...The difference between the college English reading and writing class which is supported by network and the traditional courses is that teachers and students use information technology to complete the study task and achieve the teaching objectives in the process of teaching and learning. The role of the teacher is a guider and organizer, the teaching is student-centered teaching. This paper takes the teaching practice in reading and writing class as an example, explain how to use video file, screen demonstration, chat rooms, BBS, E-mail and other different multimedia network technology and approach, how to make full use of multimedia network resources in teaching college English reading and writing, how to improve the teaching effect.展开更多
基金Project(60673164) supported by the National Natural Science Foundation of ChinaProject(06JJ10009) supported by the Natural Science Foundation of Hunan Province, China+2 种基金Project(20060533057) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(2008CB317107) supported by the Major State Basic Research and Development Program of ChinaProject(NCET-05-0683) supported by the Program for New Century Excellent Talents in University
文摘The IEEE 802.11e standard is proposed to provide QoS support in WLAN by providing prioritized differentiation of traffic. Since all the stations in the same priority access category (AC) have the same set of parameters, when the number of stations increases, the probability of different stations in the same AC choosing the same values will increase, which will result in collisions. Random adaptive MAC (medium access control) parameters scheme (RAMPS) is proposed, which uses random adaptive MAC differentiation parameters instead of the static ones used in the 802.11e standard. The performance of RAMPS is compared with that of enhanced distributed coordination access (EDCA) using NS2. The results show that RAMPS can reduce collision rate of the AC and improve the throughput by using adaptive random contention window size and inter-frame spacing values. RAMPS ensures that at any given time, several flows of the same priority have different MAC parameter values. By using the random offset for the inter-frame spacing value and the backoff time, RAMPS can provide intra-AC differentiation. The simulation results show that RAMPS outperforms EDCA in terms of both throughput and end-to-end delay irrespective of the traffic load.
文摘The difference between the college English reading and writing class which is supported by network and the traditional courses is that teachers and students use information technology to complete the study task and achieve the teaching objectives in the process of teaching and learning. The role of the teacher is a guider and organizer, the teaching is student-centered teaching. This paper takes the teaching practice in reading and writing class as an example, explain how to use video file, screen demonstration, chat rooms, BBS, E-mail and other different multimedia network technology and approach, how to make full use of multimedia network resources in teaching college English reading and writing, how to improve the teaching effect.
