Calculating Transmission Speeds (1 Viewer)

[Seraph]

Hi all

just wondering does anyone have any information on calculating speeds of transmission given certain devices and there Bandwith capabilities?

i saw a question like this in one of the papers at this site and i had no idea how to do it as i have not learnt this yet
Ive looked in my book has nothing about it!!!

?

 

[redslert]

i no longer have any ipt textbooks
so i don't have any questions which i can show you have to work it out

it would be nice if you can post up some questions and i can go through it in detail

some basics

size:
1 bit - smallest and most basic size
8 bits = 1Byte (notice capital B for Byte)
reason for lower and upper case: 1b = 1 bit, 1B = 1 Byte
1024bytes = 1KiloByte (KB)
1024KB = 1MegaByte (MB)
1024MegaBytes = 1GigaByte (GB)

these are the basic elements which you should know

Picture:
quite complicated, you have to work out pixel counts, resolution, what colour bit rate it is using....
hmmm i think they go through this in the textbook

Video:
FPS - frames per second
resolution - screen size
time - length of video

for video, you work under the impression that a video is a single file, compiled on a number of pictures put together to create motion

question:
say for example a video of 24mins, at 27FPS, with a resolution of 640*480. If the size of each frame was 23KB, how big is this video if no compression is utilised? (write answer in KB, MB, GB)

solution:
at 24minutes this equates to 24*60 = 1440seconds
at 27FPS, this equates to 27*1440 = 34560frames
if each frame is 23KB in size
.'. 23*34560 = 794880KB

now to simplify
794880KB
776.25MB
0.758GB (to 3decimal place)

audio:
Take note there is too kinds of audio, mono and stereo
mono meaning 1 channel, where as stereo is 2 channels
meaning if a questions states stereo, this means you 'might' have to multiply it by 2
'might' because it all depends on the question being asked
audio like pictures are complicated
you will have to take into account, the frequency of audio, MHz or Hz....bit rate....which is annoying and i can't create an example at the moment causing i can't remember any...

 

[Seraph]

oh no not those ones

those are all file sizes in the multimedia topic

In the communication systems topics apparently you have to calculate speeds given a network which has particular computers , file servers and switches etc

and they say like How long would a certain size file take to transfer to a certain node within the network..

 

[redslert]

oh i see
do you have sample questions?!
would really help

ok the same basics still follows

size:
1 bit - smallest and most basic size
8 bits = 1Byte (notice capital B for Byte)
reason for lower and upper case: 1b = 1 bit, 1B = 1 Byte
1024bytes = 1KiloByte (KB)
1024KB = 1MegaByte (MB)
1024MegaBytes = 1GigaByte (GB)

networks have various speeds, usually they are
- 10Mbits
- 100Mbits
- 1000Mbits

now your modem speeds are
- 28.8Kbps
- 36.6Kbps
- 56.6Kbps

hmmm

ok Say you are using a 56.6Kbps modem connection and trying to download a file which is 30MBs, how long would this take?

first work out 56.6Kbps (Kilobits per second)
notice that Kbps <- small 'b' which means bits, so to work out Bytes
56.6 / 8 = 7.075KB/s
that is the maximum speed at which your modem would go

with a file of say 30MBytes would be better to convert it to KiloBytes
.'. 30 * 1024 = 30720KiloBytes

finally
30720KB / 7.075KB/s = 4342seconds (nearest second)
4342 / 60 = 72.36minutes
72.36 / 60 = 1 Hour 12 Minutes (rounded to nearest minute)

small example.....rounding off depends on the question

with network speeds 10Mbits, 100Mbits.....

10Mbits = 1.25MB/s
100Mbits = 12.5MB/s
......(divide by 8 to get MegaBytes)

 

[SamD]

Originally posted by Seraph
Hi all

just wondering does anyone have any information on calculating speeds of transmission given certain devices and there Bandwith capabilities?
?

Be careful with your terms, bandwidth refers to the range of frequencies a signal occupies. It is related to speed, but it is definitely NOT a measure of speed.

Post the question you speak of?????

 

[Seraph]

http://www.boredofstudies.org/courses/techsci/ipt/Barker_IPT_2001_sol.zip

Question 23

(yea i know it has solutions i didnt really understand it though)

 

[redslert]

hmm reading that question at first did seem quite complicated and scary, but if you work thought it slowly, it seems very basic and easy

23) i)
From the given information the file takes 5minutes and 20second to get from the Clerk to the file server.
5min 20sec = 320 seconds
The Clerk has a connection of 250Kb/sec, for this question it is best to keep everything in the most basic units to aviod over complicating things, we shall use Kilobits as the basic unit
Now to work out how big the file was. All we have to do is multiply the time required to send the file by the maximum amount of bandwidth the Clerk has
320Kb * 250Kb/s = 80,000Kbits
Now looking at the Artist who has a connection speed of 10Mbits, this will mean
10Mbits/s = 10,000Kbits/s
So all we have to do is divide the file size in the fileserver by the speed at which the Artist can download, you must use the same units

80,000Kb / 10,000Kb/s = 8seconds

 

[Seraph]

yea i looked at it again , wasnt that hard at all!!

Hmm so 10mbit basically equivalent to 10meg a sec... i didnt really know that

 

[sunny]

Hmm so 10mbit basically equivalent to 10meg a sec... i didnt really know that

No 10MBit is not the same as 10meg (megabyte) a sec.

10 mbits/s = 10 240 kbits/s
10 240 kbits/s = 10 485 760 bits/s
10 485 760 bits/s = 1 310 720 bytes/s
1 310 720 bytes/s = 1 280 kbytes/s
1 280 kbits/s = 1.25 Mbytes/s.

 

[rckl]

can anyone tell me if i am wrong:


the text book that i am using is Heineman IPT HSC

when i am reading through it.. i realise the use of short way of represent Kilobytes, Megabytes or whatever.... in the book is shows Kb, Mb, Gb etc..

but it suppose to be KB, MB and GB, isn't it? because the capital "B" means bytes, and the lower case "b" mean bit?

 

[SamD]

but it suppose to be KB, MB and GB, isn't it? because the capital "B" means bytes, and the lower case "b" mean bit?

Correct.
Bits, with a lower case b, is only routinely used in relation to communication. And even then it is generally in regard to speed, as in 10Mbps.

HTH
Sam