Presentation on 802.11n MAC Sublayer

1. MAC Sublayer in
WLAN 802.11n
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Presented by
Syed Ahamad
Abhishek Raj
CS252 – Computer Network

2. Outline
 Introduction
 Architecture
 Physical layer
 MAC Sublayer
 Conclusion
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3. References
 Wikipedia
 Text book – Tanenbaum
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4. Introduction
 WLAN – most popular for mobile equipment’s
 Interoperability
 Mobility
 Flexibility
 cost-effective deployment
 Standardize and maintain as IEEE 802.11 by IEEE
LAN/MAN Standards Committee(IEEE 802)
 Established in 1997
 802.11a/b/g
 802.11n
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5. Architecture components
 Stations
 Basic Service set
 Extended Service set
 DS (Distribution System)
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6. WLAN Architecture 6
• Infrastructure
• Ad hoc

7. Factor - 802.11n
 Limited Capacity
 Channel Efficiency
 Multipath
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8. Limited Capacity 8

9. Channel Efficiency 9

10. Multipath 10

11. Key Structure – 802.11n 11

12. RF Signal Fidelity
 Parallel Streams
 Multiple antennas
 Identification of each frame
 Echo cancellation
 Timer setting
 Much reduce frame duplication
 Transmission beam forming
 When receiver is busy – sender finds the best way to
transmit.
 High quality of signal
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13. Physical layer
 Rate adaptation
 802.11b(11Mbps) – spread spectrum method
 Spreading sequence – Barker Sequence
 802.11a(54Mbps) – OFDM method
 But 5 GHz
 802.11g(54Mbps) – OFDM method
 Here 2.4 GHz
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14. Physical layer
 802.11n(100+Mbps) – OFDM and MIMO method
 Bandwidth - 20MHz to 40MHz
 Reduced the framing overhead
 Parallel streams
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15. 15Protocol Stack

16. MAC Sublayer
protocol efficiency
 WMM Mandatory
 WMM – allows AP to control devices
 Assures the quality of service standards
 802.11 – CSMA/CA protocol
 Minimum contention overhead
 Selective retransmission
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17. 802.11 MAC Protocol 17

18. 802.11n MAC Protocol 18
• Mode operation
• DCF(Distributed Coordination Function)
• PCF(Point Coordination Function)

19. Hidden and Exposed
problem
 Transmission Range
 Solution – Physical and virtual sensing.
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20. Virtual Sensing 20

21. Interframe Spacing 21

22. Frame format 22

23. Conclusion
 Limitation
 Spiky and time variant
 Transmission Range
 Power saving – beacon frames
 Trade off
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