Multiple acessing
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The document discusses different multiple access protocols at the data link layer. It describes random access protocols like ALOHA, CSMA, CSMA/CD, and CSMA/CA. It also covers controlled access methods using reservation, polling, and token passing. Finally, it mentions channelization techniques for multiple access like FDMA, TDMA, and CDMA that divide the channel bandwidth between stations using frequency, time, or code respectively.
Multiple acessing
- 2. Data link layer divided into two functionality-oriented sublayers LOGIC LINK CONTROL-Error and flow control MAC LAYER-Multiple access resolution
- 3. Taxonomy of multiple-access protocols discussed in this chapter
- 4. RANDOM ACCESS In random access or contention methods >No scheduling of time station >No rule that which station should send next Protocol used in this method- ALOHA Carrier Sense Multiple Access Carrier Sense Multiple Access with Collision Detection Carrier Sense Multiple Access with Collision Avoidance
- 5. >1972-for Radio >Pure/Slotted >Globally used >Acknowledgement >Back off time TB >Vulnerable time-Time in which possibility of collision ALOHA
- 6. 12.6 Frames in a pure ALOHA network
- 7. >Carrier sense multiple access >Vulnerable time-Time need to propagate from one to another >Senses the medium >Method- 1.Persistent I 2. Non Persistent- Random amount of time 3.P-Persiustance- change of slot duration> max propagation time CSMA
- 8. 12.8 Figure 12.10 Behavior of three persistence methods
- 9. >Carrier sense multiple access/collision Detection >Arguments algorithm to handle for collision >Monitors CSMA/CD
- 11. >Carrier sense multiple access/collision avoidance >Two signal >For wireless –because collision cannot be detected >Three strategy-Interframe Space(short ifs high priority) Contention window Acknowledgement CSMA/CA
- 12. Flow diagram for CSMA/CA
- 13. 12.13 CONTROLLED ACCESS In controlled access, the stations consult one another to find which station has the right to send. A station cannot send unless it has been authorized by other stations. Reservation Polling Token Passing Three popular controlled-access methods
- 15. Select and poll functions in polling access method >Primary device >Link is available >Select-selection of primary >Poll-primary device verify and allow to transmit
- 16. Logical ring and physical topology in token-passing access method
- 17. CHANNELIZATION Channelization is a multiple-access method in which the available bandwidth of a link is shared in time, frequency, or through code, between different stations. Frequency-Division Multiple Access (FDMA)-Guard band Time-Division Multiple Access (TDMA)-Access method of DLL to control PL Code-Division Multiple Access (CDMA)-One chanel all transmission, simuntaniously Protocol