calculating the time taken for downloading a 20 mb file via 3g network

how to find out the time that will be taken for downloading a 20 mb file via 3g mobile ? In theory w开发者_如何学编程hat is the mathematics to find that out ?

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Theoretically 3G has a 1.75 MB/s downlink upper limit and a 0.25 MB/s lower limit, most actual implementations probably will be close the that minimum but if you are be optimistic and use 0.5 MB/s as a average speed you can divide 20 MB by that and get 40 seconds, the time it would take to download it.

(Momentarily my 3G bandwidth clocks at 0.20 MB/s, the lower limit is more of a recommendation you see, not enforced)

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If you just break down the size into kb and divide that by an average transmission rate (that varies based on pretty much everything - including how you hold the phone) you can get a meaningful, but by no means precise, number.