[MLB-WIRELESS] Theoretical limits of 2.4 GHz band

[Michael_Florence at dlink.com.au]

Craig Mead from Sydney Wireless did and thought it was a great cost effective
way to create backbone links.

-Michael








"Tristan Gulyas" <zardoz at 2600.org.au> on 17/11/2002 11:35:39 PM
                                                                                
                                                                                
                                                                                


                                                              
                                                              
                                                              
 To:      melbwireless at wireless.org.au                        
                                                              
 cc:      (bcc: Michael Florence/Sales/DLINK-AUST)            
                                                              
                                                              
                                                              
 Subject: Re: [MLB-WIRELESS] Theoretical limits of 2.4 GHz    
          band                                                
                                                              







Has anybody done any realistic tests of the 802.11b+ 22Mbit/sec gear?

Those D-link APs, if running at high rate and if effective, could be a good
solution for those long range links that need to carry lots of data.

.t

----- Original Message -----
From: "Robert Graham Merkel" <rgmerk at mira.net>
To: <melbwireless at wireless.org.au>
Sent: Monday, November 18, 2002 12:20 AM
Subject: [MLB-WIRELESS] Theoretical limits of 2.4 GHz band


> A topic that has come up with some regularity in discussions about
> wireless networking is that the network could never supply the kind
> of data bandwidth that people would like.  It's clear that 802.11b,
> wonderful as it is, can't do the real heavy lifting that we'd like.
> However, the existence of gear like the new 22mbps Dlink range, and
> the upcoming 802.11g standard, demonstrates that we technology can
> get us more carrying capacity out of the 2.4 Ghz band than we currently
> get.
>
>
> However, there is an ultimate theoretical limit to how much data you
> can carry with a certain amount of radio spectrum and the signal/noise
> ratio.  From what I recall from my computer networking class (I'm a
> CS guy, not an electronic engineer), and a bit of research, the formula
> (called Shannon's Theorem) is:
>
> <discussion of Shannon's Theorem, skip if you already understand it>
>
> Channel Capacity = (Hardware Bandwidth) * LOG2(1 + Signal/Noise ratio).
>
> Now, the hardware bandwidth is simply the chunk of spectrum allocated
> to the communication.  If we used the entire 2.4 Ghz band that's 100
> Mhz, so hardware bandwidth = 10^8 for this calculation.
>
> The signal/noise ratio, for this formula, has to be the actual ratio,
> not the decibel ratio.  The decibel ratio is 10 log10(S/N), so the actual
> signal to noise ratio is 10^((signal-to noise in db/10))
> <end discussion>
>
> Anyway, the point of all this, is given the signal-noise ratio and the
> amount of the 2.4 Ghz band you want to use, you can determine how much
> data could ultimately be carried on the band.
>
> However, I'm not sure what values to use for the signal-noise ratio.
> Has anybody got some measured or calculated data on S/N ratios for
> interesting configurations
> that we could plug into Shannon's Theorem and see what technology might
> ultimately give us?
>
>
> --
> --------------------------------------------------------------------------
-
>                                            Robert Merkel
>                                           rgmerk at mira.net
> I know the human being and fish can coexist peacefully.
>   -- George W. Bush.
> --------------------------------------------------------------------------
>
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