Chapter 3 : Medium Access Control
<ul><li>What is meant by transmission of signal? </li></ul><ul><li>Medium Access is part of which layer in OSI? </li></ul>
Why is special MAC required? <ul><li>Hidden and Exposed Terminal Problem </li></ul><ul><li>Near and Far Terminal Problem <...
Multiple Access Techniques <ul><li>Space Division Multiple Access:- used for allocating space to users </li></ul><ul><li>F...
Algorithms in TDMA <ul><li>Fixed TDMA </li></ul><ul><ul><li>Time slots </li></ul></ul><ul><ul><li>Fixed Delay </li></ul></...
(Contd.) <ul><li>Classical Aloha </li></ul><ul><ul><li>TDM without control </li></ul></ul><ul><ul><li>Invented at Hawaii U...
(Contd.) <ul><li>Slotted Aloha </li></ul><ul><ul><li>Time Slots </li></ul></ul><ul><ul><li>Transmission at the start of th...
(Contd.) <ul><li>Carrier Sense Multiple Access (CSMA) </li></ul><ul><ul><li>Sensing carrier to avoid collision </li></ul><...
(Contd.) <ul><li>Demand Assigned Multiple Access </li></ul><ul><ul><li>Reservation + Fixed TDMA </li></ul></ul><ul><ul><li...
(Contd.) <ul><li>Packet Reservation Multiple Access (PRMA) </li></ul><ul><ul><li>Similar DAMA </li></ul></ul><ul><ul><li>I...
(Contd.) <ul><li>Reservation TDMA </li></ul><ul><ul><li>N mini-slots for reservation </li></ul></ul><ul><ul><li>N*k data s...
(Contd.) <ul><li>Multiple Access with Collision Avoidance </li></ul><ul><ul><li>Request to send </li></ul></ul><ul><ul><li...
(Contd.) <ul><li>Polling </li></ul><ul><ul><li>Master station and slaves </li></ul></ul><ul><ul><li>Round Robin, Random or...
(Contd.) <ul><li>Inhibit sense multiple access (Digital sense multiple access) </li></ul><ul><ul><li>Base station signals ...
(Contd.) <ul><li>Code Division Multiple Access </li></ul><ul><ul><li>Orthogonal codes </li></ul></ul><ul><ul><li>Protectio...
(Contd.) <ul><li>Spread Aloha Multiple Access </li></ul><ul><ul><li>Aloha + CDMA </li></ul></ul><ul><ul><li>Same orthogona...
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3 mediumaccesscontrol-090302072045-phpapp01

  1. 1. Chapter 3 : Medium Access Control
  2. 2. <ul><li>What is meant by transmission of signal? </li></ul><ul><li>Medium Access is part of which layer in OSI? </li></ul>
  3. 3. Why is special MAC required? <ul><li>Hidden and Exposed Terminal Problem </li></ul><ul><li>Near and Far Terminal Problem </li></ul>
  4. 4. Multiple Access Techniques <ul><li>Space Division Multiple Access:- used for allocating space to users </li></ul><ul><li>Frequency Division Multiple Access:- comprises all algorithms allocating frequencies to transmission channel according to FDM </li></ul><ul><li>Time Division Multiple Access:- comprises technologies which allocate time slots for communication i.e., controlling TDM </li></ul><ul><li>FDMA + TDMA </li></ul>
  5. 5. Algorithms in TDMA <ul><li>Fixed TDMA </li></ul><ul><ul><li>Time slots </li></ul></ul><ul><ul><li>Fixed Delay </li></ul></ul><ul><ul><li>Efficient for constant Data Rate </li></ul></ul><ul><ul><li>Inefficient for bursty Data Rate </li></ul></ul>
  6. 6. (Contd.) <ul><li>Classical Aloha </li></ul><ul><ul><li>TDM without control </li></ul></ul><ul><ul><li>Invented at Hawaii University </li></ul></ul><ul><ul><li>Neither co-ordinates medium access nor resolve contention </li></ul></ul><ul><ul><li>No central arbiter and no co-ordination </li></ul></ul><ul><ul><li>Simultaneous transmission leads to collision </li></ul></ul><ul><ul><li>Light load </li></ul></ul><ul><ul><li>Max. throughput for an 18% load </li></ul></ul>
  7. 7. (Contd.) <ul><li>Slotted Aloha </li></ul><ul><ul><li>Time Slots </li></ul></ul><ul><ul><li>Transmission at the start of the load </li></ul></ul><ul><ul><li>No control </li></ul></ul><ul><ul><li>Max. throughput for an 36% load </li></ul></ul><ul><ul><li>No transmission guarantee </li></ul></ul>
  8. 8. (Contd.) <ul><li>Carrier Sense Multiple Access (CSMA) </li></ul><ul><ul><li>Sensing carrier to avoid collision </li></ul></ul><ul><ul><li>Hidden Terminals Problem </li></ul></ul><ul><ul><li>Back-off algorithms </li></ul></ul><ul><ul><li>Types </li></ul></ul><ul><ul><ul><li>Non-Persistent CSMA </li></ul></ul></ul><ul><ul><ul><li>1-Persistent CSMA </li></ul></ul></ul><ul><ul><ul><li>p-Persistent CSMA </li></ul></ul></ul><ul><ul><ul><li>CSMA/CA </li></ul></ul></ul><ul><ul><ul><li>EY-NMPA </li></ul></ul></ul>
  9. 9. (Contd.) <ul><li>Demand Assigned Multiple Access </li></ul><ul><ul><li>Reservation + Fixed TDMA </li></ul></ul><ul><ul><li>Reservation period+ Transmission period </li></ul></ul><ul><ul><li>Satellite Transmission </li></ul></ul><ul><ul><li>Reservation List </li></ul></ul><ul><ul><li>Explicit Reservation Scheme </li></ul></ul>
  10. 10. (Contd.) <ul><li>Packet Reservation Multiple Access (PRMA) </li></ul><ul><ul><li>Similar DAMA </li></ul></ul><ul><ul><li>Implicit reservation </li></ul></ul><ul><ul><li>Collision during Reservation </li></ul></ul><ul><ul><li>Ensures guaranteed data rate </li></ul></ul>
  11. 11. (Contd.) <ul><li>Reservation TDMA </li></ul><ul><ul><li>N mini-slots for reservation </li></ul></ul><ul><ul><li>N*k data slots </li></ul></ul><ul><ul><li>Guarantees min. bandwidth and delay </li></ul></ul><ul><ul><li>Free slots allocates using round-robin or uncoordinated. </li></ul></ul>
  12. 12. (Contd.) <ul><li>Multiple Access with Collision Avoidance </li></ul><ul><ul><li>Request to send </li></ul></ul><ul><ul><li>Hidden and exposed terminals </li></ul></ul><ul><ul><li>No fixed access patter and co-ordinated </li></ul></ul>
  13. 13. (Contd.) <ul><li>Polling </li></ul><ul><ul><li>Master station and slaves </li></ul></ul><ul><ul><li>Round Robin, Random or reservation schemes used for polling </li></ul></ul><ul><ul><li>List of stations during contention phase </li></ul></ul>
  14. 14. (Contd.) <ul><li>Inhibit sense multiple access (Digital sense multiple access) </li></ul><ul><ul><li>Base station signals busy medium </li></ul></ul><ul><ul><li>Base station acknowledges successful transmission </li></ul></ul><ul><ul><li>Collision is detected by absence of positive acknowledge </li></ul></ul>
  15. 15. (Contd.) <ul><li>Code Division Multiple Access </li></ul><ul><ul><li>Orthogonal codes </li></ul></ul><ul><ul><li>Protection against tapping </li></ul></ul><ul><ul><li>Examples </li></ul></ul>
  16. 16. (Contd.) <ul><li>Spread Aloha Multiple Access </li></ul><ul><ul><li>Aloha + CDMA </li></ul></ul><ul><ul><li>Same orthogonal key </li></ul></ul><ul><ul><li>High power, short period </li></ul></ul><ul><ul><li>Phase difference </li></ul></ul><ul><ul><li>Synchronization </li></ul></ul><ul><ul><li>Max. throughput for 18% load </li></ul></ul><ul><ul><li>Includes advantages of spread spectrum </li></ul></ul>
  17. 17. Thank-you
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