Search results for "Computer network"
showing 10 items of 1634 documents
Enabling a win-win coexistence mechanism for WiFi and LTE in unlicensed bands
2018
The problem of WiFi and LTE coexistence has been significantly debated in the last years, with the emergence of LTE extensions enabling the utilization of unlicensed spectrum for carrier aggregation. Since the two technologies employ com-pletely different access protocols and frame transmission times, supporting coexistence with minimal modifications on existing protocols is not an easy task. Current solutions are often based on LTE unilateral adaptations, being LTE in unlicensed bands still under definition. In this paper, we demonstrate that it is possible to avoid a subordinated role for WiFi nodes, by simply equipping WiFi nodes with a sensing mechanism based on adaptive tunings of the …
Do Current Domestic Gigabit Wireless Technologies Fulfill User Requirements for Ultra High Definition Videos?
2017
We present the results from a measurement-based performance evaluation of wireless networks based on IEEE 802.11n and IEEE 802.11ac standards in an indoor environment, with the aim to analyze their performance under high definition streaming video applications. We focus our study on analyzing the highest performance of these standards using off-the-shelf equipment, both with synthetic TCP and UDP traffic to measure the saturation throughput as well as high definition video streams. The measurements have been conducted in the student labs of our university and show good performance for streaming purposes in high definition and also ultra-high definition from a subjective video quality point …
Assessing the effectiveness of IEEE 802.11e in multi-hop mobile network environments
2004
The IEEE 802.11e technology is receiving much interest due to the promising enhancements it offers to wireless local area networks in terms of QoS support. Until now, research has focused on single hop, access point based environments, which are the most common. We review the enhancements proposed in the last IEEE 802.11e draft (version 8.0). We analyze the performance of the IEEE 802.11e protocol on ad-hoc networks (multi-hop) in terms of throughput and end-to-end delay. We also measure the effectiveness for static and fully dynamic networks with a variable number of source stations. Finally, we analyze the performance of IEEE 802.11e when legacy IEEE 802.11 stations (no IEEE 802.11e suppo…
QoS Support for Time-Constrained Multimedia Communications in IEEE 802.11 WLANs: A Performance Evaluation
2005
During the past few years, we have been witnessing the massive deployment of IEEE 802.11 wireless LANs. Even though the widespread deployment of such wireless LANs, many studies are still underway aiming to design and develop simple yet effective QoS mechanisms for supporting time-constrained services over such platforms. In this paper, we first overview five different QoS mechanisms recently introduced in the literature as well as the upcoming IEEE 802.11e (EDCA) standard. We then carry out a comparative performance evaluation of all the QoS mechanisms. We focus our study on the effectiveness of the various QoS mechanisms for supporting time-constrained services.
QoS Mechanisms for IEEE 802.11 Wireless LANs
2004
Currently the Internet provides users with access to information across the world using IP technology. Until now most access points to the Internet have been fixed stations at given locations, but with increasing sales of mobile devices, mobility has become a major trend. Therefore, the Internet is becoming more and more heterogeneous due to the recent explosion of wireless networks. The IEEE 802.11 wireless LAN (WLAN) is the most widely used WLAN standard nowadays. Currently the IEEE 802.11 standard specifies an over-the-air interface between wireless devices. However, QoS services over this technology are still being defined aiming to provide support to multiple applications. Thus, a larg…
Time synchronization enhancements in wireless networks with ultra wide band communications
2022
The emergence of low cost Ultra Wide Band (UWB) transceivers has enabled the implementation of Wireless Sensor Networks (WSN) based on this communication technology. These networks are composed of distributed autonomous low cost nodes (also known as motes) with their own processing unit, memory and communications. Usually these nodes are power-limited and due to the poor performance and quality of their clocks, time synchronization is in the order of milliseconds and in some specific scenarios till microseconds. The integration of commercial UWB transceivers in these nodes can improve the synchronization accuracy. In particular, we focus on WSN nodes based on off-the-shelf commercial produc…
On-body and off-body transmit power control in IEEE 802.15.6 scheduled access networks
2014
Wireless Body Area Networks (WBANs) have received much attention due to the possibility to be used in healthcare applications. For these applications, energy saving is a critical issue, as in many cases, batteries cannot be easily replaced. A transmit power control scheme, able to adapt to the variations of the wireless body channel, will allow consistent energy saving and longer battery life. In this paper we propose a transmit power control scheme suitable for IEEE 802.15.6 narrowband scheduled access networks, in which the transmission power is modulated frame by frame according to a run-time estimation of the channel propagation conditions. A simple and effective line search algorithm i…
Statistical learning and multiple linear regression model for network selection using MIH
2014
Award of Appreciation; International audience; A key requirement to provide seamless mobility and guaranteeing Quality of Service in heterogeneous environment is to select the best destination network during handover. In this paper, we propose a new schema for network selection based on Multiple Linear Regression Model (MLRM). A horough investigation, on a huge live data collected from GPRS/UMTS networks led to identify the Key Performance Indicators (KPIs) that play the most important role in the handover process. These KPIs are: Received Signal Code Power (RSCP), received energy per chip (Ec/No) and Available Bandwidth (ABW) of the destination network. To extract a handover model from col…
Gatherer: an environmental monitoring application based on IPv6 using wireless sensor networks
2013
In this paper, we present an environmental monitoring application based on IPv6 using wireless sensor networks. We show the guidelines to connect this network to internet using the 6LowPAN standard with a real prototype in the evolution of the Internet of Things. We assign a unique IPv6 address to the different nodes motes of the network. Gatherer is based on TinyOS using IPv6 and UDP protocols and allows the data gathering of temperature and relative humidity from the different motes, requesting specific data from individual motes when required, increasing the accuracy of the measures. We compare the performance of our IPv6-based proposed application against others and show the benefits of…