[MLB-WIRELESS] 802.11g Starts Answering WLAN Range Questions

[Jason Brice]

What sort error correction methods must we be talking here to account for that large a loss in (potential) throughput?
and what sort of error rates?

I know the framing overhead on traditional wired connections doesn't take up nearly that much bandwidth.
Even with PPP overhead on something as crappy as a dial-up modem connection we see a much, better ratio of Layer 2 throughput to physical bandwidth than we are talking about with 802.11a
I understand that a wireless connection is likely to experience MANY more errors that a wired network, but the throughput still seems quite low to me..?

Does anyone have more details on this?

________________________
jason brice
senior network engineer
kiandra system solutions
level 9, 455 bourke st melbourne vic 3000
(t) +61 3 9600 1639
(f) +61 3 9600 1656



-----Original Message-----
From: Michael_Florence at dlink.com.au [mailto:Michael_Florence at dlink.com.au] 
Sent: Thursday, 16 January 2003 6:43 PM
To: John Dalton
Cc: Tristan Gulyas; melbwireless at wireless.org.au
Subject: Re: [MLB-WIRELESS] 802.11g Starts Answering WLAN Range Questions




John, that is an excellent explanation.

Michael







John Dalton <john.dalton at bigfoot.com> on 16/01/2003 01:56:39 PM
                                                                                
                                                                                
                                                                                


                                                              
                                                              
                                                              
 To:      Tristan Gulyas <zardoz at 2600.org.au>                 
                                                              
 cc:      melbwireless at wireless.org.au(bcc: Michael           
          Florence/Sales/DLINK-AUST)                          
                                                              
                                                              
                                                              
 Subject: Re: [MLB-WIRELESS] 802.11g Starts Answering WLAN    
          Range Questions                                     
                                                              







> So how come it only appears to operate at 22Mbit/sec?

It could be that the diagrams refer to MAC data rate.

The 802.11a spin always seems to quote 54Mbit/s as the data rate. These are funny numbers to the point that it could be argued to be misleading.

54Mbit/s is based on the data rate at the bottom of the physical layer (ie. what is actually transmitted and received). Layered on top of this 54bit/s stream is error correction and other such things which 'consume bits' to operate.  The end result is that the MAC actually transmits and receives at something closer to 20Mbit/s.  (Compared to around 10Mbit/s under similar assumptions for 802.11b).

Ultimately the net data rate for 802.11a is not that big an improvement on 802.11b (Depending on what you define to be big), especially at similar ranges.

Regards
John

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