DTC <me@nothingtoseehere.zzx> hath wroth:

>jrb wrote:
>> I am trying to figure out if going to 802.11n from an 802.11g is
>> really worth it. My internet service is listed as being upto 7MB. Any
>> thoughts on the switch?

Required reading on MIMO:
<http://www.veriwave.com/gurus/index.asp>
This is very much up to date.

802.11n is all about speed. Great for video and massive local file
transfers. Doesn't add much in the way of range. The rule-of-thumb
is that 4 times the speed, will give you 1/2 the range. By the time
you get to speeds greater than 54Mbits/sec, you're talking about 5 to
10 meter ranges.

However, that's for multiple streams (Airgo). To make sure that it's
a total muddle, 802.11n Draft 2 includes beam forming and steering
(Atheros and Ruckus Wireless), which for some amazing reason is
classified as MIMO. It offers no speed enhancements, but does offer
substantial indoor reflection and interference reduction. One thing
that all the various MIMO mutations have in common is that you cannot
easily add an aftermarket antenna (or antennas). If you can't get the
range with what is supplied by the manufacturer, too bad.

>Even 802.11b at 10 Mbps would be adequate for a 7 Mbps internet connection.

Ummm... nope. Thruput is roughly half the connection speed. An
11mbit/sec connection would yield about 5Mbits/sec thruput, which is
much less than the 7Mbit/sec internet speed. The message header for
the OP shows that he's on Cox.net, which has "PowerBoost" speeds to
about 10Mbits/sec for preferred and premier service levels. To
utilize 10Mbits/sec thruput, he needs at least a 24Mbit/sec connection
speed.

>802.11g is rated at 54 Mbps and would be useful for faster file
>exchanges within your own network. While it uses ODFM modulation, it is
>more robust (more reliable at longer ranges and less with than optimum
>signal levels), that advantage is lost as it requires more than twice
>the signal level for the higher speed. Locking down 802.11g to 10 Mbps
>would give you a very reliable wireless network.

Locking it down at 24Mbits/sec would be required to prevent bandwidth
constipation at 10Mbits/sec thruput. However, that doesn't work too
well. I've been recommending that locking down the speed to the
slower OFDM speeds offers a reliability improvement in that the access
point isn't constantly trying to go as fast as possible. That works
well at the slower speeds (I use 12Mbits/sec OFDM). That will a bit
slow for a 7Mbit/sec cable internet, but will not work if the OP has
burstable service. However, my experiments with locking the speed at
much faster rates (I was testing at 36Mbits/sec) has not been so
wonderful. Packet loss starts to creep up. Susceptibility to noise
interference increases. Signal loss and disconnects are more abrupt
and of course, at a shorter range. It will probably work just fine
for a closed room environment (coffee shop, conference room, bedroom,
etc), but isn't too good when going through walls, floors, or in the
presence of substantial interference.

I haven't tried the same tests with any of the MIMO devices, so I can
tell if MIMO adds anything. I doubt it because outside of fairly
short ranges, the typical Airgo MIMO access point reverts to
802.11b/g.

Incidentally, many low end routers can barely move data at cable
internet speeds, or handle many connections:
<http://www.smallnetbuilder.com/component/option,com_chart/Itemid,189/chart,121/>

>802.11n could be considered an upgrade to 802.11g in terms of robustness
>and range.

Ummm... I hope you're not referring to the 2x, 4x, now up to 12x
stickers that are appearing on the retail packages? When I see the
manufactories run a BER/PER test, at various ranges and speeds, I
might believe that manure. Meanwhile, some MIMO articles:
<http://www.smallnetbuilder.com/content/view/30224/100/>
<http://www.smallnetbuilder.com/content/view/30230/100/>
are quite revealing.

>If your 802.11b networks works fine the way it is, there's no advantage
>in spending the money to move up to 802.11n.

Sure there is. There's great benefits to all the 802.11n Draft 2
confusion. It's bad enough that most of what I buy is obsolete in a
few years. With 802.11n Draft 2, I can buy products that are obsolete
on arrival and with no guarantee of a later upgrade to the final
standard. There's also no incentive to produce such an upgrade path,
because that will cut into future replacement sales.

Bah Humbug;
E. Scrooge and Associates.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558