Questions about 802.11G and Aironet 1200s

c.tenley · ‎06-12-2003

I have heard that if you install the new 802.11g radio module into an existing 1200 that runs 802.11b, the most you will get from throughput is still only 11Mb. Is that true? If this is true, is there a way to switch the exhisting internal 802.11b radio module to an 802.11a module and then install the 802.11g module, making it a aironet 1200 802.11a/g AP?

derwin · ‎06-12-2003

Cisco does not yet have an 802.11g radio on the market. It is comming soon.

Yes you will be able to have the dual band function of a/g in the 1200

chadcase · ‎07-11-2003

When will the 802.11g radios be coming out from Cisco

derwin · ‎07-13-2003

You will need to contact your account team for details but you should see them some time latter this year.

Remember 802.11g was only just ratified in the last few weeks any cards on the market are only based on draft standards and may require updates of either hardware software or both to be complainant

lbadman · ‎07-14-2003

Is it also true that IEEE, in the final draft of g, operationally capped it at 36 Mbps- not the expected a-equivelent of 54 Mbps?

derwin · ‎07-14-2003

NO !!!!

http://standards.ieee.org/announcements/80211gfinal.html

Most of the stories in varrious pubilcations around that have suggested that IEEE lowered the throughput of 802.11g have been based on a lack of understanding of half duplex communications or not qualifying stated speeds which give a misleading effect

The standard still states 54Mbps half duplex as per the link above but the lower figures quoted elsewhere have been effective throughput. Just the same as 11Mbps half duplex gives an effective throughput of around 5 or 6 Mbps

Dont know where the 36Mps one came from but ??

kalyanccie · ‎09-09-2003

hello derwin

when i update my 802.11B card in 1230 to G , do i have to change all my 350 adapter cards also ?

regards

jcleary · ‎09-09-2003

No,

802.11g is backwards compatible w/ 802.11b, You will not have to upgrade your clients

kalyanccie · ‎09-11-2003

thanks jcleary

but those B cards will take 11 mbps max, so i would have to upgrade to newer G cards to take full advantage of my AP, am i right ?

regards

nicol.dunlop · ‎09-12-2003

Mu understanding was that only the 1100 series would be able to use the 802.11b OR the 802.11g radios.

The 1200 series could use the 802.11a AND 802.11b at the same time.

From the above replies it seems that the 1200 may also use 802.11b AND (802.11a OR 802.11g.

Is this correct ?

licst1 · ‎09-12-2003

Yep. It is true in a mixed mode. Mixed mode is the environment with IEEE 802.11b mixed with IEEE 802.11g. Since both are in 2.4 GHz, the IEEE 802.11g standard addressed the slot time to be IEEE 802.11b slot time in a mixed mode. However, some vendors, including Intersil and Broadcom had come out a kind of reserved time frame to divide the time into 2 zooms, the 11b and 11g zooms to increase the fesibility and throughput. For more detailed information, please see 11g final standard at section 19.1.2 and 19.4.4. ("The slot time is 20 µs, except that an optional 9 µs slot time may be used when the BSS consists of only ERP STAs capable of supporting this option. The optional 9 µs slot time shall not be used if the network has one or more non-ERP STAs associated."). Basically, 11b deployed 20 µs slot time and 11g deployed 9 µs slot time.

I've no answer of your second question since I do not have Aironet 1200. But based on my understanding, the situation will not be changed, unless CISCO deployed the same time-division solutions as Intersil and Broadcom did, which is not described in the standard.

ddicky · ‎09-15-2003

Well,for the 1100 A.P and from the explanation from all the above it means that there is no need for any hardware upgrade on the clients which is using AIR-PCM352.But I would like to know how should the upgrade frm 11b to 11g on the 1100 AP been done since there is no slot to be slotted in?by firmware upgrare or ...?Any idea.

smith-richard · ‎11-13-2003

On the AP1100, it is the same upgrade as the AP1200 from 11b to 11g. It requires the replacement of the Mini-PCI fitted in the AP.

rkm · ‎11-12-2003

Is it possible to have 802.11b with throughput of 11mbps now, later upgrade it to 802.11g and get 54mbps

smith-richard · ‎11-13-2003

At the moment if you are running windows clients with 11b you will only get 5.5Mbps throughput, or if you are running Linux you should be able to get about 7Mbps throughput.

Not sure what the throughput will be on 11g but it will not be 54Mbps as OS overhead will still need to be taken into account.