"jameshanley39@yahoo.co.uk" <jameshanley39@yahoo.co.uk> hath wroth:
>I have a MIMO 802.11g router, and USB wireless adaptor.
You have a problem. Let me know when you are able to read the label
and supply the vendor and model numbers of your inadequate equipment.
>range is insufficient.
So are your expectations. Could I trouble you to describe what manner
of range you were expecting? Over what terrain? Through how many
walls?
>What is a good value for
>that signal to noise ratio?
It depends on the connection speed. For a BER (bit error rate) of
about 1 error in 10^5 bits, or about 10% PER (packet error rate):
Speed SNR(dB)
11 6.99
5.5 5.98
2 1.59
1 -2.92
54 24.6
48 24.1
36 18.8
24 17.0
18 10.8
12 9.0
9 7.8
6 6.0
See:
<http://groups.google.com/group/alt.internet.wireless/msg/b806cb8cf93c9724>
for an explanation. What I managed to leave out is that these figures
are for a fairly lousy error rate. One needs to add in the
anticipated fade margin to get real numbers. Add about 20dB to each
of the SNR numbers for what is considered "good values" for viewing
with Netstumbler.
>I read that USB wireless has a rubbish internal "chip" antenna , and
>that makes for small range. I have one and it doesn't go past 2
>flights of stairs.
My stairs do not fly. You're correct. USB dongles have very small
antennas. Antenna gain is very roughly proportional to the size of
the antenna. The tiny chip or PIFA antennas have a gain of about
-6dBi to optimistically 0dBi gain. A typical non-MIMO PCMCIA card
will have an antenna gain of about 2dBi, but it's rather directional.
Please note that your flight of stairs implies that you have a change
of vertical elevation and that you might be going through a floor or
ceiling. The pattern from the USB dongle is a close approximation of
a hemisphere, so orientation isn't terribly important. However,
that's not the case with the typical access point vertical coaxial
antenna, especially if it's an add-on higher gain antenna. These
trade gain in the vertical and horizontal direction (i.e through the
floor and ceiling) in trade for more gain in the horizontal direction.
>I'd like a wireless 802.11g MIMO PCI Card, that comes with a
>reasonable antenna, but i'd also like it to have a connector for an
>antenna. (so I only have to buy an external antenna if it's not good
>without one).
Forget it for now. MIMO functionality relys heavily on the matching
between 3 or more antennas. As a result, an external antenna would
need to have 3 antennas, 3 coax cables, and 3 connectors. There are
some with external antennas, such as Linksys WMP300N but they're all
PCI cards, where there's no other alternative to locating an antenna.
All the other clients and access points have non-removable antennas or
internal antennas.
>Changing the router isn't an option at the moment.
Change what router into what? If you're going to practice
enchantments and transmogrification, perhaps a practicing wizard or
alchemist would be more helpful.
>(I did try pointing the aerials, including so the length of the aerial
>as oppose to the tip, faces the wireless usb adaptor, but no use. I
>didn't try moving the wireless usb adaptor around on a usb cable. I
>don't plan on getting a wireless usb adaptor with an antenna, but I
>might)
Indecision is the key to flexibility.
>I'd like to know the power of these things before buying.. I've heard
>that Buffalo make powerful wireless stuff. But they don't seem to have
>any PCI, and I can't see the power rating.
The transmit power is usually specified on the manufactories data
sheets. If that's not available, it can be found on the FCC ID search
page under the type certification test data. Buffalo makes various
models. The WHR-HP-G54 transmits up to 250mw. 50mw is the default
value.
>(the buffalo website is a silly design anyway. each irrelevant
>picture links to a directory, the directory's name reveals what it's
>about. - so if you ever want to browse it, that's the way!)
Right. The product quality must be directly related to the quality of
the web site.
>I know linksys show power rating, but a few have recommended buffalo.
Both manufacturers have their benefits and detriments. I don't want
to go into a point by point comparison. See:
<http://www.smallnetbuilder.com/component/option,com_chart/Itemid,189/>
for reviews and comparison charts.
Incidentally, there may be some confusion here when using the latest
MIMO buzzword. In the context of this discussion, there are 3 types
of MIMO.
1. Airgo (Qualcomm) based chipset which in my opinion is "true" MIMO.
<http://www.cdmatech.com/products/wlan.jsp>
2. Ruckus Wireless based chipsets, which are basically beam steering,
beam forming, or antenna aiming systems.
<http://www.ruckuswireless.com/technology/beamflex.php>
3. Gross misuse of the MIMO term by Buffalo on the WHR-HP-G54
claiming "MIMO like performance" with having any features that even
remotely involve MIMO technology.
<http://www.buffalotech.com/technology/our-technology/high-power/>
--
Jeff Liebermann
jeffl@comix.santa-cruz.ca.us
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Re: getting good range .. - ditching USB wireless adaptor. What PCI one? 
Linear Mode
