目的利用数据挖掘方法探讨张仲景方药服量控制方法,为提高中药临床应用的有效性、安全性和经济性提供依据。方法对详细整理归纳的263首有明确方药记载的内服仲景经方的药物剂量和服用方法进行分析总结,运用SPSS24.0软件包进行描述性统...目的利用数据挖掘方法探讨张仲景方药服量控制方法,为提高中药临床应用的有效性、安全性和经济性提供依据。方法对详细整理归纳的263首有明确方药记载的内服仲景经方的药物剂量和服用方法进行分析总结,运用SPSS24.0软件包进行描述性统计分析。结果 263首有明确方药记载的内服经方中剂型各不相同,其中汤剂200首,散剂41首,丸剂22首。汤剂单次服用剂量以每服1升(相当于现代200 m L)最为常见,并常根据方药特点灵活变动。散剂分煮散和服散2种,其中煮散,多用以水七合和一升煮散顿服,亦有以水半盏或一盏半;服散,多服1方寸匕。丸剂分煮丸和服丸2种,煮丸多水煮一丸;服丸药量多以知为度,亦或定时定量服用。每日服用次数以日三服最为常见,其他日服次数为1、2、4……10次。服药时间以定时服药、每日三服最多,此外亦有顿服、平旦服、日夜连服等特殊定时服药,以及少少含咽、不拘时等不定时服药方式。结论医圣张仲景常依据临床病症的复杂性及患者个体的差异性,遵循"以知为度、中病即止"的方药服量控制原则,选择合适的中药剂型,确定合理的单次服用剂量和服用间隔时间(每日服用次数和服药时间),因人制宜,随症施量。展开更多
The explicit rate flow control mechanisms for ABR service are used to sharethe available bandwidth of a bottleneck link fairly and reasonably among many competitive users andto maintain the buffer queue length of a bo...The explicit rate flow control mechanisms for ABR service are used to sharethe available bandwidth of a bottleneck link fairly and reasonably among many competitive users andto maintain the buffer queue length of a bottleneck switch connected to the link at a desired levelin order to avoid and control congestion in ATM networks. However, designing effective flow controlmechanisms for the service is known to be difficult because of the variety of dynamic parametersinvolved such as available link bandwidth, burst of the traffic, the distances between ABR sourcesand switches. In this paper, we present a fuzzy explicit rate flow control mechanism for ABRservice. The mechanism has a simple structure and is robust in the sense that the mechanism'sstability is not sensitive to the change in the number of active virtual connections (VCs). Manysimulations show that this mechanism can not only effectively avoid network congestion, but alsoensure fair share of the bandwidth for all active VCs regardless of the number of hops theytraverse. Additionally, it has the advantages of fast convergence, low oscillation, and high linkbandwidth utilization.展开更多
In this paper, a novel admission scheme is proposed which provides high degrees of quality of service (QoS) guarantees for multimedia traffic carried in mobile networks. The proposed scheme combines the admission cont...In this paper, a novel admission scheme is proposed which provides high degrees of quality of service (QoS) guarantees for multimedia traffic carried in mobile networks. The proposed scheme combines the admission control and bandwidth reservation to guarantee QoS requirements. It considers both local information and remote information to determine whether to accept or reject a connection. In order to embody the characteristics of the algorithms proposed in the article, two traditional algorithms of admission control are used for comparison. In the end of the paper the simulation analyses are given and the results show that the proposed algorithm can adjust the bandwidth according to the current status of networks and decrease the probability of connections forcibly dropped. The most important thing is that the algorithm is based on the multimedia communications and can guarantee the QoS of real time connections through decreasing the bandwidth of non real time connections.展开更多
Today's Internet architecture provides only "best effort" services,thus it cannot guarantee quality of service(QoS) for applications.Software Defined Network(SDN)is a new approach to computer networking ...Today's Internet architecture provides only "best effort" services,thus it cannot guarantee quality of service(QoS) for applications.Software Defined Network(SDN)is a new approach to computer networking that separates control plane and forwarding planes,and has the advantage of centralized control and programmability.In this paper,we propose HiQoS that provides QoS guarantees using SDN.Moreover,HiQoS makes use of multiple paths between source and destination and queuing mechanisms to guarantee QoS for different types of traffic.Experimental results show that our HiQoS scheme can reduce delay and increase throughput to guarantee QoS.Very importantly,HiQoS recovers from link failure very quickly by rerouting traffic from failed path to other available path.展开更多
This paper addresses the power con- trol problems of Cognitive Radio (CR) trader transmission power and interference tempera- ture constraints. First, we propose the interfer- ence constraint which ensures that the ...This paper addresses the power con- trol problems of Cognitive Radio (CR) trader transmission power and interference tempera- ture constraints. First, we propose the interfer- ence constraint which ensures that the Quality of Service (QoS) standards for primary users is considered and a non-cooperative game power control model. Based on the proposed model, we developed a logical utility function based on the Signal-to-Interference-Noise Ratio (S/NR) and a novel algorithm network power control. that is suitable for CR Then, the existence and uniqueness of the Nash Equilibrium (NE) in our utility function are proved by the principle of game theory and the corresponding optimi- zations. Compared to traditional algorithms, the proposed one could converge to an NE in 3-5 iterative operations by setting an appropriate pricing factor. Finally, simulation results ver- ified the stability and superiority of the novel algorithm in flat-fading channel environments.展开更多
A new kind of volume control hydraulic press that combines the advantages of both hydraulic and SRM(switched reluctance motor) driving technology is developed.Considering that the serious dead zone and time-variant no...A new kind of volume control hydraulic press that combines the advantages of both hydraulic and SRM(switched reluctance motor) driving technology is developed.Considering that the serious dead zone and time-variant nonlinearity exist in the volume control electro-hydraulic servo system,the ILC(iterative learning control) method is applied to tracking the displacement curve of the hydraulic press slider.In order to improve the convergence speed and precision of ILC,a fuzzy ILC algorithm that utilizes the fuzzy strategy to adaptively adjust the iterative learning gains is put forward.The simulation and experimental researches are carried out to investigate the convergence speed and precision of the fuzzy ILC for hydraulic press slider position tracking.The results show that the fuzzy ILC can raise the iterative learning speed enormously,and realize the tracking control of slider displacement curve with rapid response speed and high control precision.In experiment,the maximum tracking error 0.02 V is achieved through 12 iterations only.展开更多
To provide scalable and simple Quality of Service(QoS) mechanism for multicast services, Probe-Based Multicast Admission Control (PBMAC) scheme was proposed. In this paper, PBMAC is studicd and a so-called subsequ...To provide scalable and simple Quality of Service(QoS) mechanism for multicast services, Probe-Based Multicast Admission Control (PBMAC) scheme was proposed. In this paper, PBMAC is studicd and a so-called subsequent request problem is found in PBMAC, which degrades system performance significantly when the network traffic is heavily loaded. Based on the analysis on subsequent request problem, an Enhance PBMAC (EPBMAC) scheme is proposed, in which complementary probing is devised to solve the problem. Using a new metric of normalized requested equivalent link capacity, the pertbrmance of PBMAC and EPBMAC is analyzed and evaluated. Two implementations are proposed for incremental dcployment. The paper finally introduces evaluation with packet-based simulations. Both analytical and simulation results show the significant improvement in performance.展开更多
In the service economic age, the hotel service becomes the focus among the hotel. The competition among the hotels is fierce day by day. So, the requirement to the service quality of the guests becomes higher and high...In the service economic age, the hotel service becomes the focus among the hotel. The competition among the hotels is fierce day by day. So, the requirement to the service quality of the guests becomes higher and higher. The service quality of the hotel reflects the comprehensive quality of the hotel management. If a hotel wants to make guests be satisfied, it must pay its best effort.In this paper, the concept and significance of quality management in food and beverage service was first elaborated, and then methods of quality control at different phases are discussed in detail. Finally, some strategies for quality control in food and beverage service are put forward.展开更多
With the fast development of highspeed railways,a call for fulfilling the notion of communication at "anytime,anywhere" for high-speed train passengers in the Train Operating Control System is on the way.In ...With the fast development of highspeed railways,a call for fulfilling the notion of communication at "anytime,anywhere" for high-speed train passengers in the Train Operating Control System is on the way.In order to make a realization of that,new railway wireless communication networks are needed.The most promising one is the Long Term Evolution for Railway which will provide broadband access,fast handover,and reliable communication for high mobility users.However,with the increase of speed,the system is subjected to high bit error rate,Doppler frequency shift and handover failure just like other system does.This paper is trying to solve these problems by employing MIMO technique.Specifically,the goal is to provide higher data rate,higher reliability,less delay,and other relative quality of services for passengers.MIMO performance analysis,resource allocation,and access control for handover and various services in a two-hop model are proposed in this paper.Analytical results and simulation results show that the proposed model and schemes perform well in improving the system performances.展开更多
In order to guarantee the overall return on investment (ROI), improve user experience and quality of service (QoS), save energy, reduce electra magnetic interference (EMI) and radiation pollution, and enable the susta...In order to guarantee the overall return on investment (ROI), improve user experience and quality of service (QoS), save energy, reduce electra magnetic interference (EMI) and radiation pollution, and enable the sustainable deployment of new profitable applications and services in heterogeneous wireless networks coexistence reality, this paper proposes a cross-network cooperation mechanism to effectively share network resources and infrastructures, and then adaptively control and match multi-network energy distribution characteristics according to actual user/service requirements in different geographic areas. Some idle or lightly-loaded base stations (BS or BSs) will be temporally turned off for saving energy and reducing EMI. Initial simulation results show that the proposed approach can significantly improve the overall energy efficiency and QoS performance across multiple cooperative wireless networks.展开更多
A novel Multiple Access Control (MAC) protocol - User-dependent Perfect-scheduling Multiple Access (UPMA) protocol, which supports joint transmission of voice and data packets, is proposed. By this protocol, the bandw...A novel Multiple Access Control (MAC) protocol - User-dependent Perfect-scheduling Multiple Access (UPMA) protocol, which supports joint transmission of voice and data packets, is proposed. By this protocol, the bandwidth can be allocated dynamically to the uplink and downlink traffic with on-demand assignment and the transmission of Mobile Terminals (MTs) can be perfectly scheduled by means of polling. Meanwhile, a unique frame structure is designed to guarantee Quality of Service (QoS) in voice traffic supporting. An effective collision resolution algorithm is also proposed to guarantee rapid channel access for activated MTs. Finally, performance of UPMA protocol is evaluated by simulation and compared with MPRMA protocol. Simulation results show that UPMA protocol has better performance.展开更多
Admission control plays an important role in providing QoS to network users. Motivated by the measurement-based admission control algorithm, this letter proposed a new admission control approach for integrated service...Admission control plays an important role in providing QoS to network users. Motivated by the measurement-based admission control algorithm, this letter proposed a new admission control approach for integrated service packet network based on traffic prediction. In the letter, FARIMA(p, d, q) models in the admission control algorithm is deployed. A method to simplify the FARIMA model fitting procedure and hence to reduce the time of traffic modeling and prediction is suggested. The feasibility-study experiments show that FARIMA models which have less number of parameters can be used to model and predict actual traffic on quite a large time scale. Simulation results validate the promising approach.展开更多
A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performanc...A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performance but also the efficient utilization of the communication resources. We observe that at a large time scale the data packet delay in the communication network is roughly varying piecewise constant, which is typically true for data networks like the Internet. Based on this observation, a dynamic data packing scheme is proposed within the recently developed packet-based control framework for networked control systems. As expected this proposed approach achieves a fine balance between the control performance and the communication utilization: the similar control performance can be obtained at dramatically reduced cost of the communication resources. Simulations illustrate the effectiveness of the proposed approach.展开更多
Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, cont...Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, contention based bandwidth request scheme can be used to indicate bandwidth demands to the base station for the non-real-time polling and best-effort services. These two services are used for most applications with unknown traffic characteristics. Due to the diverse QoS requirements of those applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth allocation priorities at different packets arrival probability. The effectiveness of the differentiation schemes is evaluated by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth allocation priority, the SD performances will be better.展开更多
文摘目的利用数据挖掘方法探讨张仲景方药服量控制方法,为提高中药临床应用的有效性、安全性和经济性提供依据。方法对详细整理归纳的263首有明确方药记载的内服仲景经方的药物剂量和服用方法进行分析总结,运用SPSS24.0软件包进行描述性统计分析。结果 263首有明确方药记载的内服经方中剂型各不相同,其中汤剂200首,散剂41首,丸剂22首。汤剂单次服用剂量以每服1升(相当于现代200 m L)最为常见,并常根据方药特点灵活变动。散剂分煮散和服散2种,其中煮散,多用以水七合和一升煮散顿服,亦有以水半盏或一盏半;服散,多服1方寸匕。丸剂分煮丸和服丸2种,煮丸多水煮一丸;服丸药量多以知为度,亦或定时定量服用。每日服用次数以日三服最为常见,其他日服次数为1、2、4……10次。服药时间以定时服药、每日三服最多,此外亦有顿服、平旦服、日夜连服等特殊定时服药,以及少少含咽、不拘时等不定时服药方式。结论医圣张仲景常依据临床病症的复杂性及患者个体的差异性,遵循"以知为度、中病即止"的方药服量控制原则,选择合适的中药剂型,确定合理的单次服用剂量和服用间隔时间(每日服用次数和服药时间),因人制宜,随症施量。
文摘The explicit rate flow control mechanisms for ABR service are used to sharethe available bandwidth of a bottleneck link fairly and reasonably among many competitive users andto maintain the buffer queue length of a bottleneck switch connected to the link at a desired levelin order to avoid and control congestion in ATM networks. However, designing effective flow controlmechanisms for the service is known to be difficult because of the variety of dynamic parametersinvolved such as available link bandwidth, burst of the traffic, the distances between ABR sourcesand switches. In this paper, we present a fuzzy explicit rate flow control mechanism for ABRservice. The mechanism has a simple structure and is robust in the sense that the mechanism'sstability is not sensitive to the change in the number of active virtual connections (VCs). Manysimulations show that this mechanism can not only effectively avoid network congestion, but alsoensure fair share of the bandwidth for all active VCs regardless of the number of hops theytraverse. Additionally, it has the advantages of fast convergence, low oscillation, and high linkbandwidth utilization.
文摘In this paper, a novel admission scheme is proposed which provides high degrees of quality of service (QoS) guarantees for multimedia traffic carried in mobile networks. The proposed scheme combines the admission control and bandwidth reservation to guarantee QoS requirements. It considers both local information and remote information to determine whether to accept or reject a connection. In order to embody the characteristics of the algorithms proposed in the article, two traditional algorithms of admission control are used for comparison. In the end of the paper the simulation analyses are given and the results show that the proposed algorithm can adjust the bandwidth according to the current status of networks and decrease the probability of connections forcibly dropped. The most important thing is that the algorithm is based on the multimedia communications and can guarantee the QoS of real time connections through decreasing the bandwidth of non real time connections.
基金supported partly by NSFC(National Natural Science Foundation of China)under grant No.61371191 and No.61472389
文摘Today's Internet architecture provides only "best effort" services,thus it cannot guarantee quality of service(QoS) for applications.Software Defined Network(SDN)is a new approach to computer networking that separates control plane and forwarding planes,and has the advantage of centralized control and programmability.In this paper,we propose HiQoS that provides QoS guarantees using SDN.Moreover,HiQoS makes use of multiple paths between source and destination and queuing mechanisms to guarantee QoS for different types of traffic.Experimental results show that our HiQoS scheme can reduce delay and increase throughput to guarantee QoS.Very importantly,HiQoS recovers from link failure very quickly by rerouting traffic from failed path to other available path.
基金partially supported by the National Natural Science Foundation of China under Grant No.61172073the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University under Grant No.2012D19+1 种基金the Fundamental Research Funds for the Central Universities,Beijing Jiaotong University under Grant No.2013JBZ01the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No.NCET-12-0766
文摘This paper addresses the power con- trol problems of Cognitive Radio (CR) trader transmission power and interference tempera- ture constraints. First, we propose the interfer- ence constraint which ensures that the Quality of Service (QoS) standards for primary users is considered and a non-cooperative game power control model. Based on the proposed model, we developed a logical utility function based on the Signal-to-Interference-Noise Ratio (S/NR) and a novel algorithm network power control. that is suitable for CR Then, the existence and uniqueness of the Nash Equilibrium (NE) in our utility function are proved by the principle of game theory and the corresponding optimi- zations. Compared to traditional algorithms, the proposed one could converge to an NE in 3-5 iterative operations by setting an appropriate pricing factor. Finally, simulation results ver- ified the stability and superiority of the novel algorithm in flat-fading channel environments.
基金Project(2007AA04Z144) supported by the National High-Tech Research and Development Program of ChinaProject(2007421119) supported by the China Postdoctoral Science Foundation
文摘A new kind of volume control hydraulic press that combines the advantages of both hydraulic and SRM(switched reluctance motor) driving technology is developed.Considering that the serious dead zone and time-variant nonlinearity exist in the volume control electro-hydraulic servo system,the ILC(iterative learning control) method is applied to tracking the displacement curve of the hydraulic press slider.In order to improve the convergence speed and precision of ILC,a fuzzy ILC algorithm that utilizes the fuzzy strategy to adaptively adjust the iterative learning gains is put forward.The simulation and experimental researches are carried out to investigate the convergence speed and precision of the fuzzy ILC for hydraulic press slider position tracking.The results show that the fuzzy ILC can raise the iterative learning speed enormously,and realize the tracking control of slider displacement curve with rapid response speed and high control precision.In experiment,the maximum tracking error 0.02 V is achieved through 12 iterations only.
文摘To provide scalable and simple Quality of Service(QoS) mechanism for multicast services, Probe-Based Multicast Admission Control (PBMAC) scheme was proposed. In this paper, PBMAC is studicd and a so-called subsequent request problem is found in PBMAC, which degrades system performance significantly when the network traffic is heavily loaded. Based on the analysis on subsequent request problem, an Enhance PBMAC (EPBMAC) scheme is proposed, in which complementary probing is devised to solve the problem. Using a new metric of normalized requested equivalent link capacity, the pertbrmance of PBMAC and EPBMAC is analyzed and evaluated. Two implementations are proposed for incremental dcployment. The paper finally introduces evaluation with packet-based simulations. Both analytical and simulation results show the significant improvement in performance.
文摘In the service economic age, the hotel service becomes the focus among the hotel. The competition among the hotels is fierce day by day. So, the requirement to the service quality of the guests becomes higher and higher. The service quality of the hotel reflects the comprehensive quality of the hotel management. If a hotel wants to make guests be satisfied, it must pay its best effort.In this paper, the concept and significance of quality management in food and beverage service was first elaborated, and then methods of quality control at different phases are discussed in detail. Finally, some strategies for quality control in food and beverage service are put forward.
基金the support from NSFC under Grant 61222105the 863 Plan of China under Grant 2014AA01A706+3 种基金the project of State Key Lab under Grant RCS2012ZT013the Key Project of Chinese Ministry of Education under Grant 313006the Key Project for Railway Ministry of China under Grant 2012X008-Athe project of State Key Lab under Grant No. RCS2011ZZ002
文摘With the fast development of highspeed railways,a call for fulfilling the notion of communication at "anytime,anywhere" for high-speed train passengers in the Train Operating Control System is on the way.In order to make a realization of that,new railway wireless communication networks are needed.The most promising one is the Long Term Evolution for Railway which will provide broadband access,fast handover,and reliable communication for high mobility users.However,with the increase of speed,the system is subjected to high bit error rate,Doppler frequency shift and handover failure just like other system does.This paper is trying to solve these problems by employing MIMO technique.Specifically,the goal is to provide higher data rate,higher reliability,less delay,and other relative quality of services for passengers.MIMO performance analysis,resource allocation,and access control for handover and various services in a two-hop model are proposed in this paper.Analytical results and simulation results show that the proposed model and schemes perform well in improving the system performances.
基金supported by the National Natural Science Foundation of China ( NSFC)( No. 60902041)Chinese Academy of Sciences ( No. 2010045)the Ministry of Science and Technology( MOST) of China ( No. 2010DFB10410,No. 2009DFB13080 and No. 2009ZX03003-009)
文摘In order to guarantee the overall return on investment (ROI), improve user experience and quality of service (QoS), save energy, reduce electra magnetic interference (EMI) and radiation pollution, and enable the sustainable deployment of new profitable applications and services in heterogeneous wireless networks coexistence reality, this paper proposes a cross-network cooperation mechanism to effectively share network resources and infrastructures, and then adaptively control and match multi-network energy distribution characteristics according to actual user/service requirements in different geographic areas. Some idle or lightly-loaded base stations (BS or BSs) will be temporally turned off for saving energy and reducing EMI. Initial simulation results show that the proposed approach can significantly improve the overall energy efficiency and QoS performance across multiple cooperative wireless networks.
基金Supported by the National Natural Science Foundation of China(No.69872028)and National '863' Project (No.863-317-03-03-99)
文摘A novel Multiple Access Control (MAC) protocol - User-dependent Perfect-scheduling Multiple Access (UPMA) protocol, which supports joint transmission of voice and data packets, is proposed. By this protocol, the bandwidth can be allocated dynamically to the uplink and downlink traffic with on-demand assignment and the transmission of Mobile Terminals (MTs) can be perfectly scheduled by means of polling. Meanwhile, a unique frame structure is designed to guarantee Quality of Service (QoS) in voice traffic supporting. An effective collision resolution algorithm is also proposed to guarantee rapid channel access for activated MTs. Finally, performance of UPMA protocol is evaluated by simulation and compared with MPRMA protocol. Simulation results show that UPMA protocol has better performance.
基金Supported in part by the National Natural Science Foundation of China under grant No.69872025,the Information Office of Tianjin Municipal Government and a Gift from Cisco System
文摘Admission control plays an important role in providing QoS to network users. Motivated by the measurement-based admission control algorithm, this letter proposed a new admission control approach for integrated service packet network based on traffic prediction. In the letter, FARIMA(p, d, q) models in the admission control algorithm is deployed. A method to simplify the FARIMA model fitting procedure and hence to reduce the time of traffic modeling and prediction is suggested. The feasibility-study experiments show that FARIMA models which have less number of parameters can be used to model and predict actual traffic on quite a large time scale. Simulation results validate the promising approach.
基金supported by the National Natural Science Foundation of China(Grant Nos.6142230761174061&61304048)+4 种基金the Scientific Research Starting Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of Chinathe National Hi-Tech Research and Development Program of China("863"Project)(Grant No.2014AA06A503)the Youth Innovation Promotion Association,Chinese Academy of Sciences,in part by the Youth Top-Notch Talent Support Programthe 1000-Talent Youth ProgramZhejiang 1000-Talent Program
文摘A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performance but also the efficient utilization of the communication resources. We observe that at a large time scale the data packet delay in the communication network is roughly varying piecewise constant, which is typically true for data networks like the Internet. Based on this observation, a dynamic data packing scheme is proposed within the recently developed packet-based control framework for networked control systems. As expected this proposed approach achieves a fine balance between the control performance and the communication utilization: the similar control performance can be obtained at dramatically reduced cost of the communication resources. Simulations illustrate the effectiveness of the proposed approach.
基金the National Basic Research Program(973) of China (No. 2005C13321804)
文摘Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, contention based bandwidth request scheme can be used to indicate bandwidth demands to the base station for the non-real-time polling and best-effort services. These two services are used for most applications with unknown traffic characteristics. Due to the diverse QoS requirements of those applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth allocation priorities at different packets arrival probability. The effectiveness of the differentiation schemes is evaluated by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth allocation priority, the SD performances will be better.