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Exponential Smoothing Waiting Times for CSMA/CD to Reduce Collisions

IP.com Disclosure Number: IPCOM000037560D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Johnson, JM: AUTHOR [+3]

Abstract

In Carrier-Sense Multiple Access with Collision Detection (CSMA/CD), exponential back off is used to determine the wait time after a collision before retransmitting. Instead of exponential back off, single exponential smoothing provides a better method to determine back off time after each collision. Exponential smoothing has the advantage of giving a higher weighting to the most recent values.

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Exponential Smoothing Waiting Times for CSMA/CD to Reduce Collisions

In Carrier-Sense Multiple Access with Collision Detection (CSMA/CD), exponential back off is used to determine the wait time after a collision before retransmitting. Instead of exponential back off, single exponential smoothing provides a better method to determine back off time after each collision. Exponential smoothing has the advantage of giving a higher weighting to the most recent values.

Though there are different methods of exponential smoothing, single exponential smoothing will be sufficient. Single exponential smoothing has the form given below.

Fn = AXt + (1-A)Ft

Here, the different variables mean the following:

Ft is the latest forecast value.

Fn is the forecast value for next period.

Xt is the most recent actual value.

A is the smoothing constant.

The initial value for a single exponential smoothing can be an estimate based on the past data.

The value of A (smoothing constant) is between 0 and 1. A large value of A like 0.9 gives little smoothing, while a small value of A like 0.1 gives considerable smoothing.

The starting value or the first random delay value before next transmission after the first collision gives us Xt. For calculating the next delay, as per binary exponential back off, we double the value of Xt. This gives us the value of Ft. Instead of taking this value of Ft, for the random delay value, we use the value of Fn obtained by single exponential smoothing.

So after...