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Session-Based QoS Management Architecture for Wireless Local Area Networks
Abstract and Figures
Growing demands for the public wireless broadband services will require more capacity than the one provided by IP-based service
providers (ISPs). The increasing popularity of WLANs due to the use of license-free radio spectrum with low-cost, easily deployable,
high-data-rate wireless services, has encouraged service providers to consider their deployment in high density usage areas
such us public hotspots to provide complementary broadband access to their networks and services. In order to provide consistent
QoS control for multimedia applications (VoIP, VoD,...) over hotspots, a Session Initiation Protocol (SIP) based QoS management
architecture is proposed in this article. Performance evaluations are discussed to illustrate the feasibility of the proposed
architecture.
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In this paper, we propose a QoS control mechanism that estimates the congestion of wireless channels in the wireless LAN and evaluates the voice packet drop ratio based on the estimated congestion status. The mechanism adjusts the voice packet transmission rate according to the evaluated packet loss ratio, and thereby resolves the congestion situation. In this way, the mechanism can keep users' quality of experience levels within acceptable ranges.
Voice over Wireless LAN (VoWLAN) is becoming more and more helpful in our life and is expected to be among the most important applications in next generation networks. However, the maximum number of VoIP sessions that a WLAN can ensure is very small. Moreover, when the WLAN reaches its capacity the addition of one VoIP session affects the QoS parameters of all VoIP sessions. In this paper, we propose an adaptive technique to ensure the active VoIP sessions of users with high priority (from a provider perspective). Thus, in order to guarantee the quality of high priority sessions, we propose to downgrade the quality (low but acceptable MOS) of user sessions with low priority by changing their used codecs (e.g., ITU G729 instead of ITU G711). This technique and all related monitoring functions are defined into the proposed session-based QoS management architecture. In order to validate our approach a complete test-bed is made up by which we have performed some feasibility and gain tests.
The increasing popularity of WLANs-due to the use of license-free radio spectrum with low-cost, easily deployable and high-data-rate wireless services- has encouraged service providers to consider deploying them in high density usage areas, such as public hotspots, to provide complementary broadband access to their networks and services. This article proposes a Session Initiation Protocol based QoS management architecture that aims to provide consistent QoS control for multimedia applications (VoIP, VoD, ...) over wireless access networks. In particular, we will present a generic QoS based management architecture for decentralized management of multimedia applications over wireless access networks, such as WLAN. We will apply our architecture to the management of the WLAN in order to assure QoS (throughput and delay) for the delivered multimedia applications according to users' priorities and providers' objectives. Performance evaluations are discussed to illustrate the feasibility and the efficiency of the proposed architecture through the implementation of a real-world testbed.
The aim of program specialization is to optimize programs by exploiting certain knowledge about the context in which the program will execute. There exist many program manipulation techniques which allow specializing the program in different ways. Among them, one of the best known techniques is partial evaluation , often referred to simply as program specialization, which optimizes programs by specializing them for (partially) known input data. In this work we describe abstract specialization , a technique whose main features are: (1) specialization is performed with respect to "abstract" values rather than "concrete" ones, and (2) abstract interpretation rather than standard interpretation of the program is used in order to propagate information about execution states. The concept of abstract specialization is at the heart of the specialization system in CiaoPP, the Ciao system preprocessor. In this paper we present a unifying view of the different specialization techniques used in CiaoPP and discuss their potential applications by means of examples. The applications discussed include program parallelization, optimization of dynamic scheduling (concurrency), and integration of partial evaluation techniques.
To effectively manage the traffic distribution inside a network, traffic splitting is needed for load sharing over a set of equal-cost-multi-paths (ECMPs). In this paper, a new traffic splitting algorithm, called Table-based Hashing with Reassignments (THR), is proposed. Based on the load sharing statistics collected, THR selectively reassigns some active flows from the over-utilized paths to under-utilized paths. The reassignment process takes place in such a way that the packet out-of-order problem is less severe. Simulations show that THR provides close-to-optimal load balancing performance but suffers about 5% of packets arrived out-of-order. Although additional traffic monitoring function is needed by THR, we show that the extra complexity incurred is marginal. (c) 2005 Elsevier B.V. All rights reserved.
Onion routing is an infrastructure for private communication over a public network. It provides anonymous connections that are strongly resistant to both eavesdropping and traffic analysis. Onion routing's anonymous connections are bidirectional, near real-time, and can be used anywhere a socket connection can be used. Any identifying information must be in the data stream carried over an anonymous connection. An onion is a data structure that is treated as the destination address by onion routers; thus, it is used to establish an anonymous connection. Onions themselves appear different to each onion router as well as to network observers. The same goes for data carried over the connections they establish. Proxy-aware applications, such as Web browsers and e-mail clients, require no modification to use onion routing, and do so through a series of proxies. A prototype onion routing network is running between our lab and other sites. This paper describes anonymous connections and their implementation using onion routing. This paper also describes several application proxies for onion routing, as well as configurations of onion routing networks
This paper investigates the long-lived TCP bulk through- put over the CDMA 1x EV-DO service that provides high-speed \always on" Internet connectivity in a wide-area mobile environment. Although the peak rates of downlink/uplink are specied as 2.4 Mbps/153 Kbps, the user-experienced application-layer throughput has not been much reported and analyzed. In our experiment, it was shown that average TCP throughputs over downlink/uplink are 572.5/94.7Kbps and the av- erage packet loss rates of 1x EV-DO downlink/uplink are 0.2/4.7%. The average end-to-end round-trip delay was 417.4ms with the variance of 14,995ms. Although the packet loss rate is low, bursty packet losses fre- quently occur because of packet corruption with TCP checksum fail- ures, which result in TCP performance degradation by the retransmis- sion timeout. Our study showed that this TCP checksum errors are re- lated with the TCP/IP header compression algorithm at link layer proto- cols such as PPP. Our measurement-based analysis of TCP performance could be used for the correct model of the 3G wireless link characteristic and for the real-world simulation of TCP behavior over the 3G wireless network.
