在传统的无线局域网(Wireless Local Area Network,WLAN)环境下,VoIP(Voiceover Internet Protocol)业务的传输容量严重受限,大大限制了无线VoIP的发展。通过分析与仿真,发现接入点(Access Point,AP)为限制无线局域网中语音传输容量的瓶...在传统的无线局域网(Wireless Local Area Network,WLAN)环境下,VoIP(Voiceover Internet Protocol)业务的传输容量严重受限,大大限制了无线VoIP的发展。通过分析与仿真,发现接入点(Access Point,AP)为限制无线局域网中语音传输容量的瓶颈,从而有针对性地提出了动态调整AP竞争信道优先级的方法。该方法在AP队列过长时提高AP发送数据的优先级,简单易行,并可有效缓解AP的瓶颈效应。多场景下的仿真结果表明,无线局域网中语音传输容量可提高20%,而信道接入延时可降低60%左右。展开更多
In announced hybrid protocols,there are two mechanisms usually employed.One operates in aCSMA family manner and the other follows a token passing family way.However,only one ofthem works efficiently when traffic is li...In announced hybrid protocols,there are two mechanisms usually employed.One operates in aCSMA family manner and the other follows a token passing family way.However,only one ofthem works efficiently when traffic is light or heavy.This results in an inefficient redundance and aburden to the protocol implementation.In this paper,we present a new hybrid concept and its idealmodel in which risky transmissions alternate with safe transmissions in response to the dynamicchange in traffic.Being similar to virtual time CSMA in the abstract,a single control mechanism isproposed to approach this ideal model.The mechanism is rather compact,and its implementationcan be designed to be simple,efficient,reliable,robust,and fully distributed without any centralizedelement at any instant.Simulation results show that the proposed mechanism performs well overthe entire range of the traffic load from light to heavy.展开更多
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
为了提高无线局域网(wireless local area network,WLAN)接入环境下的语音传输容量,通过估算和多场景仿真研究了多种因素对WLAN中语音传输容量的影响,包括语音编码、包头压缩、网络协议等,并提出可通过适当增加语音帧长及动态调整接入...为了提高无线局域网(wireless local area network,WLAN)接入环境下的语音传输容量,通过估算和多场景仿真研究了多种因素对WLAN中语音传输容量的影响,包括语音编码、包头压缩、网络协议等,并提出可通过适当增加语音帧长及动态调整接入点竞争信道的优先级来提高传输容量。多场景下的仿真结果表明:采用改进方案后,系统传输容量可提高20%以上。该方案简单可行,有效地改善了WLAN环境下的语音传输容量及服务质量。展开更多
文摘在传统的无线局域网(Wireless Local Area Network,WLAN)环境下,VoIP(Voiceover Internet Protocol)业务的传输容量严重受限,大大限制了无线VoIP的发展。通过分析与仿真,发现接入点(Access Point,AP)为限制无线局域网中语音传输容量的瓶颈,从而有针对性地提出了动态调整AP竞争信道优先级的方法。该方法在AP队列过长时提高AP发送数据的优先级,简单易行,并可有效缓解AP的瓶颈效应。多场景下的仿真结果表明,无线局域网中语音传输容量可提高20%,而信道接入延时可降低60%左右。
文摘In announced hybrid protocols,there are two mechanisms usually employed.One operates in aCSMA family manner and the other follows a token passing family way.However,only one ofthem works efficiently when traffic is light or heavy.This results in an inefficient redundance and aburden to the protocol implementation.In this paper,we present a new hybrid concept and its idealmodel in which risky transmissions alternate with safe transmissions in response to the dynamicchange in traffic.Being similar to virtual time CSMA in the abstract,a single control mechanism isproposed to approach this ideal model.The mechanism is rather compact,and its implementationcan be designed to be simple,efficient,reliable,robust,and fully distributed without any centralizedelement at any instant.Simulation results show that the proposed mechanism performs well overthe entire range of the traffic load from light to heavy.
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.
文摘为了提高无线局域网(wireless local area network,WLAN)接入环境下的语音传输容量,通过估算和多场景仿真研究了多种因素对WLAN中语音传输容量的影响,包括语音编码、包头压缩、网络协议等,并提出可通过适当增加语音帧长及动态调整接入点竞争信道的优先级来提高传输容量。多场景下的仿真结果表明:采用改进方案后,系统传输容量可提高20%以上。该方案简单可行,有效地改善了WLAN环境下的语音传输容量及服务质量。
