dc.description.abstract | TCP is the most important and widely used transport protocol at present. With the advent of advanced wireless broadband technologies, TCP must be tuned and enhanced from traditional networks made up of purely wired links to wired-cum-wireless networks. As a result of high bit error rate (BER) in wireless links, TCP halves down its congestion window unnecessarily caused by random packet loss event continuously, and the performance is significantly degraded in wireless networks. The problem about differentiating congestion loss and random loss has been investigated recently by a number of schemes. Wireless TCP solutions, such as JTCP (jitter-based TCP) improve TCP performance for wireless networks. However, even if the enhanced solutions make efforts to distinguish packet losses,
some unavoidable events may occur to make TCP timeout frequently. Hence, we amend JTCP scheme to design a smooth transmission scheme to increase the correctness of loss distinction and avoid bursty transmission.
To have better transport performance, we design enhanced JTCP to provide better performance in sending data traffic under wire-cum-wireless environment. However, JTCP only have good performance in data traffic but multimedia traffic. For example, video streaming. Rate-based congestion control is an important issue for advanced video streaming. The widely adopted rate based congestion control scheme is TFRC. According to TCP-friendly rate estimation mechanism, TFRC can provide smooth perceptual quality in video streaming. However, video streaming needs not only smooth rate control but also higher priority in competing network bandwidth. Compare to data traffic, video streaming has minimum bandwidth requirement issue, however, data traffic only cares about integrity. If video streaming can not acquire network bandwidth in time, outdated video streaming packets will be dropped and network bandwidth wasted. In a word, TFRC is too conservative while it transmits video streaming service.
Measurement of end-to-end available bandwidth has received considerable attention due to its potential use in improving QoS. Available bandwidth enables the sending rate to adapt to network conditions, so that packet loss, caused by congestion, can be significantly reduced before error control mechanisms are finally employed. To this end, we propose a probing noise resilient available bandwidth estimation scheme, called JitterPath, which is adaptive to both the fluid and bursty traffic models. Two key factors, one-way delay jitter and accumulated queuing delay, are both
exploited to predict the type of queuing region for each packet pair. Then, the bottleneck utilization information included in the joint queuing regions is estimated and used to quantify the captured traffic ratio, which indicates the relationship between the probing rate and available bandwidth. The contributions of our method are as follows: (1) JitterPath can work without being restricted to fluid traffic models; (2) since JitterPath does not directly use the bottleneck link capacity to calculate the available bandwidth, it is feasible for use in a multi-hop environment with a single
bottleneck; (3) JitterPath inherently reduces the impact of probing noises under the bursty cross traffic model. Extensive simulations, Internet experiments, and comparisons with other methods were conducted to verify the effectiveness of our method under both single-hop and multi-hop environments. Before deeply discuss available bandwidth, we need to understand the major traffic in the Internet and the problem while it applied in wireless environment.
Beside issue of conservation, TFRC will malfunction in wireless environment if packet lost events were introduced by wireless channel loss but network congestion. Some State-of-arts try to utilize delay measurement to distinguish channel loss from observed packet loss events. However, these approaches do not take care the measurement noise came from background traffics. The bursty nature of background traffic breaks relationship between the delay measurement and congestion. To solve this issue, we proposed a new one-way delay jitter based method, OWDJ-TFRC, to achieve above two goals in wired-cum-wireless network. Simulation results also show that our method conducts performance improvement without intrusiveness issue under bursty background traffic in wire-cum-wireless network.
| en_US |