L27 - Efficiency of CSMA = End-to-end propagation time TF =...

Info icon This preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Efficiency of CSMA ô = End-to-end propagation time F T = Average frame duration F â = ô / T Beta is the key parameter in determining efficiency. With CSMA/CD, For values of â < 1, approximate limiting efficiency is For â << 1, efficiency is almost perfect. For â near 1, efficiency is no better than unslotted ALOHA.
Image of page 1

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

View Full Document Right Arrow Icon
Timing with a center repeater station: Each sees the synchronized timing and the echo of its own signal as well as others. This allows the establishment of synchronized slots - as in Slotted ALOHA, reservation minislots, reserved slots.
Image of page 2
The collision resolution algorithm Assume time is slotted and all users observe (before next slot) if slot is unused, has a success, or has a collision ( number of colliders unknown). If collision occurs, only colliders will attempt until all are known successful. Then others may send. Goal: have an algorithm that resolves a collision in as few slots as possible, while also allowing all users to know when the collision has been resolved. The basic idea is called a splitting algorithm .
Image of page 3

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

View Full Document Right Arrow Icon
Illustration of the splitting algorithm Three colliders whose selected numbers are: A= .3, B=.4, C=.6. Let .5 divide the subsets, so A and B will transmit in the next slot and collide again, as shown: Efficiency and stability of ALOHA or CSMA/CD are improved with this algorithm.
Image of page 4
Wireless LAN protocols Not always true that all stations can hear each other. Suppose A and C both send to B. B and D see a collision, But A, C, E and F don’t see any collision.
Image of page 5

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

View Full Document Right Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern