Why is 54G really 21G?

[GadgetGuy]

I saw the recent review of the Linksys WRTG54 and while I do not want to look a gift horse in the mouth (21mb/s is great) can anyone tell me why no one can seem to get even close to 50% of 54mb? Will it ever be true? (I'm talking 802.11g mode only) Will we ever have 54mb with this standard, i.e. we're just experiencing growing pains/limited hardware, etc.

 

[kwebb68]

These are wireless hubs, using collision avoidance instead of collision detection, CSMA/CA for an 802.11b AP, CSMA/CD for a wired hub. Not very efficient. Similar reason as two why you would never see the full 100 Mb on a hub. Switch either for that matter. Protocol overhead is another reason. Acks and other variables contribute as well. Anyway, the same was true for .11b Even enterprise AP's peaked at around 6 1/2 Mb. The number you see on these devices is the wireless signalling rate, not the throughput or bandwidth. Signalling rate may be 11 or 54 Mb and depends primarily on signal strength and noise levels. Throughput depends on that, plus the encoding scheme, protocols used, and various other things that can degrade your bandwidth. On a side note, when the Aironet 802.11b AP was introduced, late 1998, it was much closer to a 2 Mb pipe than 11 Mb. firmware over the years has increased the potential for microwave transmission but I would think the best you could ever hope to see, because of the MAC protocol, is in the 25+ Mb range. Perhaps taking a peak at 30 Mb, but I'd be suprised. OFDM, the modulation type used by .11g and .11a, is not much more efficient, if at all, than CCK, the modulation type for 802.11b.

<P ID="edit"><FONT SIZE=-1><EM>Edited by kwebb68 on 03/26/03 04:45 PM.</EM></FONT></P>