scholarly journals Παροχή ποιότητας υπηρεσιών σε ασύρματα τοπικά δίκτυα πολυμέσων τεχνολογίας ΙΕΕΕ 802.11e

2011 ◽  
Author(s):  
Αναστάσιος Πολίτης
Keyword(s):  
Ieee 802.11 ◽  
Local Area ◽  
Multimedia Applications ◽  
Ieee 802.11E ◽  
Medium Access ◽  
Large Numbers ◽  
Integrated Architecture ◽  
Wireless Infrastructure ◽  
Networking Technology

The fast growth of Wireless Local Area Networks (WLANs) during the last decade, has led to their wide acceptance by the vast majority of electronic equipment users as the dominant wireless networking technology. The indisputable functionality standard of WLANs is the IEEE 802.11. At the same time, multimedia applications technology has received a similar success. It was, therefore, an expected result that the users of both technologies required that multimedia applications were adequately supported by the wireless infrastructure. Towards this direction, the IEEE has published a series of amendments to the initial WLAN standard. The widely accepted amendment for supporting multimedia in WLANs is the IEEE 802.11e. This specification defined the functionality of a new Medium Access Control (MAC), capable of providing Quality of Service (QoS) to applications with high demands from the network.However, the IEEE 802.11 has received negative reviews regarding its capability of multimedia support in highly congested wireless networks. These conditions are quite common, especially in infrastructure networks with large numbers of users (e.g., public hotspots, university networks etc.). As a response to this challenge, the international scientific community, has designed and proposed various enhancements mechanisms to improve the IEEE 802.11e functionality in high load situations.This thesis contributes to this international effort of QoS provisioning in multimedia WLANs, by developing and assessing a novel mechanism which combines, adapts and enforces the characteristics and the design techniques that have been proposed in the international bibliography, into an integrated architecture. The efficiency of the mechanism is evaluated and compared to other implementations, and the related experimental results are proven to be very promising.

scholarly journals Improving WLAN Quality of Services (Qos) Using Opnet

2016 ◽  
Vol 9 (3) ◽  
pp. 204-211
Author(s):  
Ishwar Baidari ◽  
S. P. Sajjan ◽  
Ajeet Singh
Keyword(s):  
Ieee 802.11 ◽  
Local Area Networks ◽  
Local Area ◽  
Wireless Local Area Networks ◽  
Ieee 802.11E ◽  
Distributed Coordination ◽  
Medium Access ◽  
Access Delay ◽  
Coordination Function

Wireless local area networks (WLANs) are in a period of great expansion and there is a strong need for them to support multimedia applications. With the increasing demand and penetration of wireless services, users of wireless networks now expect Quality of Service (QoS) and performance comparable to what is available from fixed networks. Providing QoS requirements like good throughput and minimum access delay are challenging tasks with regard to 802.11 WLAN protocols and Medium Access Control (MAC) functions. This research is done to study, the presently implemented schemes (the Point Coordination Function (PCF) of IEEE 802.11, the Enhanced Distributed Coordination Function (EDCF) of the proposed IEEE 802.11e extension to IEEE 802.11), solves these issues and what can be done to improve them further. The metrics used were Throughput, Data Drop, Retransmission and Medium Access Delay, to analyze the performance of various MAC protocols in providing QoS to users of WLAN. Two scenarios, with same Physical and MAC parameters, one implementing the DCF and other EDCF, were created in the network simulation tool (OPNET MODELER) to obtain the results. The results showed that the performance of EDCF was better in providing QoS for real-time interactive services (like video conferencing) as compared to DCF, because of its ability to differentiate and prioritize various services. Index Terms - Wireless local area networks (WLANs),

scholarly journals Latency and Jitter Analysis for IEEE 802.11e Wireless LANs

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Sungkwan Youm ◽  
Eui-Jik Kim
Keyword(s):  
Local Area ◽  
Ieee 802.11E ◽  
Distributed Coordination ◽  
Mac Layer ◽  
Medium Access ◽  
Distributed Coordination Function ◽  
Packet Latency ◽  
Coordination Function ◽  
The Voice

This paper presents a numerical analysis of latency and jitter for IEEE 802.11e wireless local area networks (WLANs) in a saturation condition, by using a Markov model. We use this model to explicate how the enhanced distributed coordination function (EDCF) differentiates classes of service and to characterize the probability distribution of the medium access control (MAC) layer packet latency and jitter, on which the quality of the voice over Internet protocol (VoIP) calls is dependent. From the proposed analytic model, we can estimate the available number of nodes determining the system performance, in order to satisfy user demands on the latency and jitter.

Performance Analysis and Evaluation of IEEE 802.11E MAC in WLANs with Hidden Stations and Multimedia Applications

2010 ◽  
pp. 161-174
Author(s):  
Mamun I. Abu-Tair
Keyword(s):  
Performance Evaluation ◽  
Loss Probability ◽  
Multimedia Applications ◽  
Mac Protocols ◽  
Heterogeneous Traffic ◽  
Ieee 802.11E ◽  
Wireless Multimedia ◽  
Medium Access ◽  
Access Delay ◽  
Medium Utilization

Recently there have been considerable interests focusing on the performance evaluation of IEEE 802.11e Medium Access Control (MAC) protocols, which were proposed for supporting differentiated quality of services in wireless local area networks (WLANs). Heterogeneous traffic generated by wireless multimedia applications and hidden stations arisen from the wireless transmission power constraints have significant impact on the performance of MAC protocols. This study performs extensive simulation experiments and conducts comprehensive performance evaluation of the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) protocol in WLANs in the presence of hidden stations and heterogeneous traffic. For this purpose, non-bursty Poisson, bursty ON/OFF, and fractal-like self-similar processes with high variability are used to model and generate heterogeneous network traffic. The performance results have shown that this protocol is able to achieve differentiated throughput, access delay, packets loss probability, and medium utilization. However, the hidden stations can degrade the throughput and medium utilization as well as increase greatly the medium access delay, packets loss probability, and collision ratio under heterogeneous traffic.

scholarly journals The Impact of Dynamic RTS Threshold Adjustment for IEEE 802.11 MAC Protocol

2009 ◽  
Vol 5 (1) ◽  
pp. 5-20 ◽  
Author(s):  
Mostafa Mjidi ◽  
Debasish Chakraborty ◽  
Naoki Nakamura ◽  
Norio Shiratori
Keyword(s):  
Ieee 802.11 ◽  
Data Transmission ◽  
Mac Protocol ◽  
Threshold Value ◽  
Local Area ◽  
Wireless Channel ◽  
Main Element ◽  
Medium Access ◽  
Hidden Terminal ◽  
The Impact

In recent years, wireless technologies and application received great attention. The Medium Access Control (MAC) protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel in wireless local area networks (WLANs). IEEE 802.11 introduced the optional RTS/CTS handshaking mechanism to address the hidden terminal problem as well as to reduces the chance of collision in case of higher node density and traffic. RTS Threshold (RT) determines when RTS/CTS mechanism should be used and proved to be an important parameter for performance characteristics in data transmission. We first investigate to find a meaningful threshold value according to the network situation and determine the impact of using or disengaging the RTS/CTS optional mechanism and dynamically adjust the RTS Threshold to maximize data transmission. The results show a significant improvement over existing CSMA/CA and RTS/CTS schemes. Our adaptive scheme performed even better when data rate increases. We verify our proposed scheme both analytically and with extensive network simulation using ns-2.

scholarly journals QoS-Based Two-Level user Scheduling Scheme for MU-MIMO Wireless LANs

2019 ◽  
Vol 9 (1S3) ◽  
pp. 32-39
Keyword(s):  
Local Area Networks ◽  
Local Area ◽  
Wireless Local Area Networks ◽  
User Scheduling ◽  
Medium Access ◽  
Frequency Selective Fading ◽  
High Data ◽  
Rate Transmission ◽  
Data Rate Transmission

The advances in physical layer technology has led to the performance upgradation of wireless local area networks (WLANs). More recently, multi-input multi-output (MIMO) is considered to be a key technology to enable high data rate transmission in WLANs. However, the actual benefit of this approach can be utilized, if there is an appropriate mechanism to select and schedule the users. Also, providing Quality of Service (QoS) support to user demands has become a major task in WLANs. In this paper, a two-level user scheduling approach for WLANs is discussed and its performance is evaluated using high-transmission rates with the assumption of frequency selective fading. For the purpose of comparison, some well-known medium access control (MAC) scheduling schemes are considered. It is shown that, the proposed scheme enhances throughput and achieves fairness among the users. Further, this scheme can be used to reduce contention during the acquisition of channel feedback.

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