Santiago Pérez

EDCA 802.11e Performance under Different Scenarios: Quantitative Analysis

The global throughput of an 802.11e WLAN is determined by EDCA (Enhanced Distributed Channel Access) parameters, among other aspects, that are usually configured with predetermined and static values. This study carefully evaluates the Quality of Service (QoS) of Wi-Fi with EDCA in several realistic scenarios with noise and a blend of wireless traffic (e.g., voice, video, and best effort, with Pareto distribution). The metrics of the benefits obtained in each case are compared, and the differentiated impact of network dynamics on each case is quantified. This study proposes a new experimental scenario based on the relative proportion of traffic present in the network. Stations have been implemented using HSANs (Hierarchical Stochastic Activity Networks) and simulated using the Möbius tool.

Tuning Mechanism For IEEE 802.11e EDCA Optimization

The overall performance of a WLAN 802.11e is determined, among other things, by the Enhanced Distributed Channel Access (EDCA) parameters, typically configured with default and static values. The same does not vary according to the dynamic requirements of Quality of Service (QoS) of the network. To achieve significant improvements in the performance of the network, and simultaneously comply with the specifications of QoS, a new algorithm of tuning is proposed to make the adjustment of these parameters dynamically, which we call Algorithm for the Differentiation of Traffic Multiple (MTDA). The algorithm has been evaluated in realistic scenarios with noise, reaching a initialization effective, rapid convergence, and the differentiation of effective multiple wireless traffic (voice, video and best effort with Pareto distribution). It adopted a model of wireless station implemented in Hierarchical Stochastic Activities Networks (HSANs), which runs on the simulator Möbius.

Experimental Study of Multicast and Unicast Video Traffic in WAN Links

In recent years there has been an exponential increase in the growth in multimedia applications, and in particular in video applications. Understanding the behavior of the video traffic and the requirements for the network helps network administrators to improve the traffic. In this work, a quantitative analysis is performed by experimentation, in order to evaluate the behavior and impact of video traffic on WAN networks. We propose a WAN test bed with fourth subescenarios that allows to inject unicast or multicast video traffic, compressed with several codecs. The generic topology used includes a computer running as a streaming server and up to 20 desktop computers (PCs) as clients connected at the ends of a network as if outside a WAN. This network WAN is formed by routers and switchs with different types of links interconnecting the same. For the operation between routers was configured the OSPF routing protocol v2. For the same routers are configured the routing multicast protocol PIM in dense mode. From capturing video traffic, we identified several interesting performance and Qo metrics, such as unicast and multicast throughput, delay, jitter, and Pareto distribution. We include detailed contributions on the impact produced by several factors, such as the codec used for the compression, and the use of unicast and multicast traffic when there are restrictions on the bandwidth, as in a corporate real WAN link of some few Mbps. The work oriented on the configurations to be taken into account for an adequate management of similar networks and an efficient use of the resources available, without compromising the performance and the expected QoS. Besides facilitates the comparison of the results with those obtained from analytical studies and modelling for different contexts.

Experimental study of unicast and multicast video traffic using WAN test bed

The deployment of IP multicast protocols in each router in the path is needed to access the benefits of the multicast. IP multicast exists today mainly in LAN networks and in small areas of highly controlled interconnected networks. In fact, some companies started to offer tailored solutions to try to overcome these limitations. On the other hand, over the last decade, the multimedia applications have expanded rapidly, and in particular in video applications. There are Internet sites that offer movies on-line; and it is common for users to upload and download videos with sites like YouTube (© Google Inc.). The video call via the Internet is common with applications, such as Skype (© Microsoft). The growth of video traffic should be taken into account when designing a network. Understanding the behavior of the video traffic and the requirements for the network helps network administrators to improve the traffic planning. In this work, a quantitative analysis is performed by experimentation, in order to evaluate the behavior and impact of video traffic on WAN networks. We propose a WAN test bed composed by a video traffic server and several client stations that allows injecting unicast and multicast video traffic, compressed with several codecs. From capturing video traffic, we identified several interesting unicast and multicast performance metrics, such as: throughput, number of frames, delays, jitter, and interframe spaces and frame sizes distributions. Several factors have been taken into account: the video resolution configuration, the type of video, and restrictions on the bandwidth, as in a corporate real WAN link of some few Mbps. This study facilitates the comparison of the results with those obtained from analytical and modelling studies for different contexts.

An evaluation of QoS for intensive video traffic over 802.11e WLANs

With the continuing development of the wireless technologies (Wi-Fi, 3G, 4G, WiMax and Bluethooth), the study of wireless multimedia transmissions has gained lately more attention. For example, the expectations of the company leaders on the growth of Wi-Fi video traffic has updated the lines of research on the standard IEEE 802.11e introduced to provide QoS (Quality of Service) to WLAN (Wireless LAN) networks. A quantitative analysis has been performed by simulation. We use a node model EDCA (Enhanced Distributed Channel Access) 802.11e with the tool Möbius of the University of Illinois, which supports an extension of SPN (Stochastic Petri Networks), known as HSAN (Hierarchical Stochastic Activity Networks). This formalism favors the comparison of the results with those obtained from other tools, based mainly on simulation languages, for Wi-Fi stations with the capacity to transmit voice, video or best effort traffic in presence of error. This article introduces novel scenario that varies the load by increasing the number of active stations from 5 to 45 but maintaining their relative traffic proportion. The proportion of traffic injected by stations is 65% video, 2% voice, and 33% best effort. Measured performance metrics were absolute or direct performance, relative performance, average delay of queue, and average queue size.