Part_8_macprocedures

Part_8_macprocedures - Medium Access Control EE450:...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
EE450, USC, Zahid 1 Medium Access Control EE450: Introduction to Computer Networks Professor A. Zahid
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EE450, USC, Zahid 2 Medium Access Control z Single shared broadcast channel z Two or more simultaneous transmissions by nodes: interference z collision if node receives two or more signals at the same time Multiple Access Protocol z Distributed algorithm that determines how nodes share channel, i.e., determine when node can transmit z Communication about channel sharing must use channel itself!
Background image of page 2
EE450, USC, Zahid 3 Classifications of MAC Protocols Three broad classes: z Channel Partitioning z Divide channel into smaller “pieces” (time slots, frequency, code) z Allocate piece to node for exclusive use z Random Access z Channel not divided, allow collisions z “Recover” from collisions z “Taking turns” z Nodes take turns, but nodes with more to send can take longer turns
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EE450, USC, Zahid 4 IEEE802 Standards for LANs
Background image of page 4
EE450, USC, Zahid 5 IEEE802.3 ( Based on Ethernet) “Carrier Sense Multiple Access”
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EE450, USC, Zahid 6 Carrier Sense Multiple Access z CSMA/CD: Carrier sense, multiple access with collision detection z collisions detected within short time z colliding transmissions aborted, reducing waste z Persistent, non-persistent and P-persistent retransmission z Collision Detection: z On baseband bus, collision produces much higher signal voltage than transmitted signal z For twisted pair (Hub-topology) activity on more than one port is collision
Background image of page 6
EE450, USC, Zahid 7 Behavior of Three Persistent Scenarios
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EE450, USC, Zahid 8 Collisions in CSMA/CD • Collisions can still occur: propagation delay means two nodes may not hear each other’s transmission • When collision occur, entire frame is wasted • Collision is detected by comparing transmitted and received signal strengths (Hard to do in WLANs, TBD)
Background image of page 8
EE450, USC, Zahid 9 Vulnerable Time in CSMA
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EE450, USC, Zahid 10 Collision Detection
Background image of page 10
EE450, USC, Zahid 11 Flow Chart of CSMA/CD
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/29/2009 for the course EE 450 at USC.

Page1 / 40

Part_8_macprocedures - Medium Access Control EE450:...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online