When wireless hosts use different rates to transmit data in IEEE 802.11 networks, it will take on the state of performance anomaly which will severely decrease the throughputs of all the higher rate hosts. Hence, it i...When wireless hosts use different rates to transmit data in IEEE 802.11 networks, it will take on the state of performance anomaly which will severely decrease the throughputs of all the higher rate hosts. Hence, it is bad for video service transmission. Considering that video is very sensitive to packet delivery delay but can tolerate some packet losses, we propose a novel cross-layer scheme which takes these two characteristics into consideration. Firstly, the maximum number of retransmissions for a video Medium Access Control (MAC) frame is computed in MAC layer according to video frame rate requirement of application layer and current access delay of MAC layer. Secondly, within the margin of the tolerant Packet Loss Rate (PLR) of application layer, several video MAC frames are allowed to drop so that we can adaptively select the transmission rate as high as possible for the rest of video MAC frames in terms of current channel quality and the maximum number of retransmissions. Experiment results show that the proposed method can reduce the delay and jitter of video service and improve the throughputs of fast hosts. Therefore, it increases the quality of reconstructed video to a certain extent and relieves the performance anomaly of network effectively.展开更多
为了提高多速率无线网络的网络性能,文章提出了一种基于速率组合的低平均时延网络编码(low average delay network coding algorithm based on rate combination,LADRC)算法。该算法充分考虑了各数据包传输速率的差异性,遵循高速率数据...为了提高多速率无线网络的网络性能,文章提出了一种基于速率组合的低平均时延网络编码(low average delay network coding algorithm based on rate combination,LADRC)算法。该算法充分考虑了各数据包传输速率的差异性,遵循高速率数据包优先发送以及速率相近数据包组合编码的原则,有选择性地添加附带数据包,从而确定最终的编码方案。在IEEE802.11b标准下得到的仿真试验结果表明,与贪心算法和最小传输速度优先编码(minimum transmission rate first encoding,MTRFE)算法相比,该算法在传输时间和平均时延上都有明显的减少。展开更多
基金Supported by the National Natural Science Foundation of China(No.61071091,No.60802021)the Research and Innovation Program for University Postgraduates of Jiangsu Province(CX10B_188Z)
文摘When wireless hosts use different rates to transmit data in IEEE 802.11 networks, it will take on the state of performance anomaly which will severely decrease the throughputs of all the higher rate hosts. Hence, it is bad for video service transmission. Considering that video is very sensitive to packet delivery delay but can tolerate some packet losses, we propose a novel cross-layer scheme which takes these two characteristics into consideration. Firstly, the maximum number of retransmissions for a video Medium Access Control (MAC) frame is computed in MAC layer according to video frame rate requirement of application layer and current access delay of MAC layer. Secondly, within the margin of the tolerant Packet Loss Rate (PLR) of application layer, several video MAC frames are allowed to drop so that we can adaptively select the transmission rate as high as possible for the rest of video MAC frames in terms of current channel quality and the maximum number of retransmissions. Experiment results show that the proposed method can reduce the delay and jitter of video service and improve the throughputs of fast hosts. Therefore, it increases the quality of reconstructed video to a certain extent and relieves the performance anomaly of network effectively.
文摘为了提高多速率无线网络的网络性能,文章提出了一种基于速率组合的低平均时延网络编码(low average delay network coding algorithm based on rate combination,LADRC)算法。该算法充分考虑了各数据包传输速率的差异性,遵循高速率数据包优先发送以及速率相近数据包组合编码的原则,有选择性地添加附带数据包,从而确定最终的编码方案。在IEEE802.11b标准下得到的仿真试验结果表明,与贪心算法和最小传输速度优先编码(minimum transmission rate first encoding,MTRFE)算法相比,该算法在传输时间和平均时延上都有明显的减少。
文摘IEEE802·11在物理层支持多速率.目前已提出许多机制通过自动调整速率充分利用多速率能力.本文观察到在无线网络中,相对于单跳的低速率链路,多跳高速率的路径可以减少信道占用时间,并提出了中继协助的媒体接入协议(Relay Aided Media Access,RAMA).RAMA利用中继节点将一跳低速链路拆为两跳高速链路.大量仿真结果表明,RAMA能够提供更好的吞吐量和时延性能.
