Qos in wlan
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Transcript of Qos in wlan
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BYWAQAS SHEHZAD
FAST NU PAKISTAN
QoS In WLAN
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Outline
IntroductionQoS Parameters.802.11 medium access control schemes
(MAC).802.11e medium access control
schemes (MAC).Conclusion.Reference.
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Introduction
What is 802.11?802.11 refers to a family of specifications
developed by the IEEE for wireless LAN technology.
802.11 Standards.1997 - 802.11 up to 2Mbps (900MHZ).1999 - 802.11b 2.4GHZ and up to 11Mbps.1999 – 802.11a 5GHZ and up to 54Mbps.200x – 802.11g 2.4GHZ and up to 54Mbps.200x – 802.11e for QoS.
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Quality of Service (QoS)
QoS is the capability to provide resource assurance in a network.
QoS Parameters: Bandwidth. Delay.(how long it takes for a bit of data
to travel across the network from one node or endpoint to another.)
Packet loss rate. Jitter.
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QoS in TP link wireless router
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IEEE 802.11e
HCF Controlled Channel Access
Enhanced DCF Channel Access
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802.11 medium access control schemes (MAC).
There are two basic medium access control (MAC) modes:
Distributed Coordination Function (DCF).
Point Coordination Function (PCF).
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Distributed Coordination Function (DCF)
Contention-Based.Based on Carrier Sense Multiple
Access with Collision Avoidance (CSMA/CA) algorithm.
Designed for a best-effort service.Supports Asynchronous transmission.
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Limitation of Distributed Coordination Function (DCF)
Does not provide any QoS guarantees.Does not support real-time application.Designed for equal priorities.Does not support the concept of
differentiating frames with different user priorities.
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Point Coordination Function (PCF)
Contention free-based.Uses a centralized polling scheme.Differentiation Considered based on
priority.Supports synchronous transmission..
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Limitation of Point Coordination Function (PCF)
poor QoS performance.Uses a simple round-robin
algorithm, which can not handle the various QoS requirements.
Transmission time of the polled stations is unknown.
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Hybrid Coordination Function (HCF)
There are two methods of channel access:
Enhanced DCF channel access (EDCA).
HCF controlled channel access (HCCA).
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Enhanced DCF Channel Access (EDCA)
Contention-Based channel access(many users to use the same radio channel without pre-coordination).
Provides service differentiation.Classifies the traffic into 8 different
classes.Each station has 4 access categories
to provide service differentiation.
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EDCA
Priority Access Category (AC)
Designation (Informative)
0 0 Best Effort
1 0 Best Effort
2 0 Best Effort
3 1 Video Probe
4 2 Video
5 2 Video
6 3 Voice
7 3 Voice
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HCF Controlled Channel Access ( HCCA)
Provides Guaranteed Services with a much higher probability than EDCA.
Combines the advantages of PCF and DCF.
Coordinates the traffic in any fashion (not just round- robin).
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Conclusion
The IEEE 802.11 wireless LAN (WLAN) has become one of the most widely used wireless technologies in these days.
The 802.11 standards can not provide any QoS guarantees due to poor performance.
The 802.11e offers QoS support to time-sensitive applications, such as, audio and video communications.