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Network utilisation formula

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From: ANONYMOUS
Date: Mon 8th Jun, 10:05am
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Hi Chris, 

I just wanted to clarify how Utilisation is calculated. 

In SlottedAloha.c, the formula that was used was: 

utilisation = numSuccessfulTransmissions / numTimeslots.

Where:
numSuccesfulTransmissions = total num successful transmissions over the entire timeslot
numTimeslot = total num timeslot

However, based on what I gather from the slides, Utilisation is calculated as:

utilisation = S / G

Where:
S = throughput or successful packets over a time period
G = offered load or total packets over a time period

There's a slight difference in how Utilisation is calculated in the C code and the 
lecture slides. I think the C code version uses an estimate whereas the S/G equation is 
more accurate. 

If a question were to come up in the exam, should I use the S/G equation or the C code 
equation? 

Network utilisation formula

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From: Christopher M.
Date: Mon 8th Jun, 4:23pm
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ANONYMOUS wrote:

> There's a slight difference in how Utilisation is calculated in the C code and the 
> lecture slides. I think the C code version uses an estimate whereas the S/G equation is 
> more accurate. 
> 
> If a question were to come up in the exam, should I use the S/G equation or the C code 
> equation?

(well worded question; thank you).
If asked about slotted Aloha, they're effectively the same, as the nodes only transmit, or not, at 
the beginning of each slot, and defer until the beginning of following slots.
For pure Aloha, the formula utilisation = S / G is more correct because it accounts for the 
continuous, not discrete case, of nodes transmitting whenever they want to (including in the middle 
of time slots).
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