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Wireless Link (wireless + link)

Distribution by Scientific Domains

Engineering	87%

Selected Abstracts

Novel DLC model for QoS enhancement of bursty VBR traffic in wireless ATM networks

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 8 2008
Hosam El-Ocla
Several data-link control (DLC) protocol procedures have been proposed in order to provide reliable data transmission over powerless radio links. However, many quality of service (QoS) issues still need to be achieved such as balance between cell transfer delay (CTD) and cell loss rate (CLR), absence of cell delay variation (CDV) and network traffic utilisation. The main problem with wireless ATM is how to overcome the unreliability of the wireless link in order to maintain QoS requirements especially for variable bit rate (VBR) application. Here, we propose a model that provides QoS support for ATM virtual connections (VC) and solves the unreliability problem of the wireless ATM through an efficient DLC protocol for bursty VBR traffic. This model mainly concerns with enhancing QoS to gain error-free wireless transmission and regulating VBR Traffic. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Performance of TCP on low-bandwidth wireless links with delay spikes

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2008
Pasi Lassila
We model the goodput of a single TCP source on a wireless link experiencing sudden increases in Round Trip Time (RTT), that is delay spikes. Such spikes trigger spurious timeouts that reduce the TCP goodput. Renewal reward theory is used to derive a straightforward expression for TCP goodput that takes into account limited sending rates (limited window size), lost packets due to congestion and the delay spike properties such as the average spike duration and distribution of the spike intervals. The basic model is for independent and identically distributed (i.i.d.) spike intervals, and correlated spike intervals are modelled by using a modulating background Markov chain. Validation by ns2 simulations shows excellent agreement for lossless scenarios and good accuracy for moderate loss scenarios (for packet loss probabilities less than 5%). Numerical studies have also been performed to assess the impact of different spike interval distributions on TCP performance. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Empirical evaluation of receiver-based TCP delay control in CDMA2000 networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2007
Oh-keun Kwon
Abstract Wide-area broadband wireless technologies such as CDMA2000 often suffer from variable transfer rate and long latency. In particular, TCP window-based rate control causes excessive buffering at the base station because of the lower transfer rate of the wireless link than that of the wired backhaul link. This performance characteristic of TCP further increases the end-to-end delay, and additional resources are required at the base station. This paper presents a practical mechanism to control the end-to-end TCP delay for CDMA2000 networks (or other similar wireless technologies). The key idea is to reduce and stabilize RTT (round-trip time) by dynamically controlling the TCP advertised window size, based on a runtime measurement of the wireless channel condition at the mobile station. The proposed system has been implemented by modifying the Linux protocol stack. The experiment results, conducted on a commercial CDMA2000 1x network, show that the proposed scheme greatly reduces the TCP delay in non-congested networks, while not sacrificing the TCP throughput in congested networks. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Retransmission strategies for an acceptable quality of HDTV in the wireless and wired home scenario

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2007
Frederik Vanhaverbeke
Abstract We evaluate the performance of various retransmission schemes to achieve the goal of less than one visible distortion in twelve hours for high definition television. The focus is on an indoor wireless link and a DSL link, and we consider systems where the packets are protected by means of retransmissions with and without forward error correcting (FEC) codes. In order to achieve a satisfactory performance with restricted latency, we propose an unconventional retransmission procedure. The overall conclusion is that retransmissions without FEC achieve the best performance with the lowest latency, lowest overhead and lowest complexity, both in the wireless and the wired home scenario. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Enhancing multimedia streaming over existing wireless LAN technology using the Unified Link Layer API

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2007
Tim Farnham
This paper examines how multimedia streaming scenarios can be enhanced by cross-layer interaction, and in particular link performance information and configuration options provided by the recently developed Unified Link Layer API (ULLA). It provides results of an experimental implementation developed for this purpose in a wireless LAN (WLAN) environment. Multimedia streaming is an application that is gaining in popularity for mobile devices and in particular mobile Internet-based content broadcasting is rapidly emerging as a key feature on mobile devices. In these scenarios, the wireless link (last hop) is normally the performance bottleneck due to the dynamic and limited capacity of the wireless medium. The use of ULLA in this context can provide the ability to tailor the video transmission to the wireless link performance and also to configure the links in response to performance problems or environmental changes. For this purpose the focus of multimedia streaming has been on WLAN link technology and dynamic adaptation (i.e., dynamic channel selection and video transcoding) using a dynamic resource reservation overlay protocol. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Performance of TCP on low-bandwidth wireless links with delay spikes

Wireless video streaming with TCP and simultaneous MAC packet transmission (SMPT),

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2004
Frank H. P. Fitzek
Abstract Video streaming is expected to account for a large portion of the traffic in future networks, including wireless networks. It is widely accepted that the user datagram protocol (UDP) is the preferred transport protocol for video streaming and that the transmission control protocol (TCP) is unsuitable for streaming. The widespread use of UDP, however, has a number of drawbacks, such as unfairness and possible congestion collapse, which are avoided by TCP. In this paper we investigate the use of TCP as the transport layer protocol for streaming video in a multi-code CDMA cellular wireless system. Our approach is to stabilize the TCP throughput over the wireless links by employing a recently developed simultaneous MAC packet transmission (SMPT) approach at the link layer. We study the capacity, i.e. the number of customers per cell, and the quality of service for streaming video in the uplink direction. Our extensive simulations indicate that streaming over TCP in conjunction with SMPT gives good performance for video encoded in a closed loop, i.e. with rate control. We have also found that TCP is unsuitable (even in conjunction with SMPT) for streaming the more variable open-loop encoded video. Copyright © 2004 John Wiley & Sons, Ltd. [source]

WTCP: an efficient mechanism for improving wireless access to TCP services

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2003
Karunaharan Ratnam
Abstract The transmission control protocol (TCP) has been mainly designed assuming a relatively reliable wireline network. It is known to perform poorly in the presence of wireless links because of its basic assumption that any loss of a data segment is due to congestion and consequently it invokes congestion control measures. However, on wireless access links, a large number of segment losses will occur more often because of wireless link errors or host mobility. For this reason, many proposals have recently appeared to improve TCP performance in such environment. They usually rely on the wireless access points (base stations) to locally retransmit the data in order to hide wireless losses from TCP. In this paper, we present Wireless-TCP (WTCP), a new mechanism for improving wireless access to TCP services. We use extensive simulations to evaluate TCP performance in the presence of congestion and wireless losses when the base station employs WTCP, and the well-known Snoop proposal (A comparison of mechanisms for improving TCP performance in wireless networks. In ACM SIGCOMM Symposium on Communication, Architectures and Protocols, August 1996). Our results show that WTCP significantly improves the throughput of TCP connections due to its unique feature of hiding the time spent by the base station to locally recover from wireless link errors so that TCPs round trip time estimation at the source is not affected. This proved to be critical since otherwise the ability of the source to effectively detect congestion in the fixed wireline network is hindered. Copyright © 2003 John Wiley & Sons, Ltd. [source]