wireless bandwidth formulas?

If I have an app that uses 5Mps of bandwidth, how do I figure out how
many connections of my app will run across a wireless technology like
802.11 that say's it's 54Mps or even Wimax which is 70Mps? Is it as
simple as 70Mps / 5Mps = 14 streaming data links?



William

On 27 Feb 2007 13:36:10 -0800, "William" <(E-Mail Removed)> wrote:

>If I have an app that uses 5Mps of bandwidth, how do I figure out how
>many connections of my app will run across a wireless technology like
>802.11 that say's it's 54Mps or even Wimax which is 70Mps? Is it as
>simple as 70Mps / 5Mps = 14 streaming data links?

I'm a bit concerned with your abrev. Is 5Mps "millions of packets per
second" or is it "millions of bits per second". I'll assume the
latter.

Well, 802.11a/b/g do NOT run at a fixed thruput. I'll assume TCP
instead of UDP to make my life easier. If you have a 54Mbit/sec
wireless connection, the most you can get for TCP thruput is about
25Mbits/sec. If you have a crappy signal and can only connect at
5.5Mbits/sec, you'll be lucky if you can get 2Mbits/sec thruput. See
the table at:
<http://wireless.wikia.com/wiki/Wi-Fi#Performance_and_Speed>
for the maximum speeds.

Once you've determined what thruput you can run at, then just divide
that speed by your 5Mbits/sec bandwidth as you indicated.

WiMax is quite different from 802.11a/b/g. The connection speed is
set by the ISP at the central access point. No ISP is going to give
you the full 70Mbits/sec connection speed because that would leave no
bandwidth for any other users. Basically, your bandwidth is a
function of your signal strength (which limits the bit or packet error
rate), and what your ISP will give you. Interference, QoS, load
limits, quotas, and other users will contribute to additional slowing.

If you're thinking of wireless video, compression methods have a huge
effect on thruput.

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