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Topic Title: WiFi 802.11n on the standard PCI bus
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Created On: 25 August 2010 09:38 PM
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 25 August 2010 09:38 PM
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PMK

Posts: 6
Joined: 12 October 2007

Dears,

Thinking about upgrade my WiFi card from g to n standard on the PCI slot. One thing gives me small headache - what's the point to upgrade up to 300 Mbps on a card if standard PCI bus can handle up to 133 Mbps? Even assuming, that average transmission speed between a WiFi card and a router is much lower, say 200 Mbps, there's still much overhead which will wait in a buffer. The only point for such upgrade - what I can see - is that actual average speed for WiFi is around 150 Mbps (or lower) and therefore might roughly match PCI bus speed. Am I right?

Cheers, Pete
 26 August 2010 08:48 AM
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ectophile

Posts: 526
Joined: 17 September 2001

I think it's safe to say that you will never get 300Mbps from 802.11n in the real world.

In any case, the older 802.11g is limited to 54Mbps theoretical, so an increase to over 100Mbps is still a large improvement.

-------------------------
S P Barker BSc PhD MIET
 26 August 2010 09:10 AM
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Roundtrip

Posts: 247
Joined: 17 June 2006

Only makes sense if the rest of your network is also 802.11n kit.

Obvious benefits:
1. Higher speed but not as high as "marketed".
2. The MIMO antennae system ensures better range.
3. Streaming of content is likely to be less problematic.

Checkout:
http://www.computerworld.com/s...1n_wireless_networking

-------------------------
Best wishes & regards

John A Thomson
allayit
 26 August 2010 05:10 PM
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PMK

Posts: 6
Joined: 12 October 2007

Originally posted by: ectophile

I think it's safe to say that you will never get 300Mbps from 802.11n in the real world.


Certainly I won't. However, I was more optimistic about the average transmission speed, say 150-200 MBps. In fact the actual one seems to be less than 100 MBps. And yes - this is still a large improvement compared with 'maximum' 54 MBps (so again in fact much less) from the older standard. And yes - 133 MBps for the standard PCI bus is more than required to carry the input from the newest WiFi.

Cheers, Pete
 26 August 2010 05:19 PM
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PMK

Posts: 6
Joined: 12 October 2007

Originally posted by: Roundtrip

Only makes sense if the rest of your network is also 802.11n kit.


By 'rest of the network' you mean a router broadcasting according to 802.11n specs? Yes, got it.

Obvious benefits:

1. Higher speed but not as high as "marketed".

2. The MIMO antennae system ensures better range.

3. Streaming of content is likely to be less problematic.


That makes sense, thanks, will order this card for my machine.

Cheers, Pete
 26 August 2010 06:15 PM
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Roundtrip

Posts: 247
Joined: 17 June 2006

By 'rest of the network' you mean a router broadcasting according to 802.11n specs?


I also mean any other network client device.


That makes sense, thanks, will order this card for my machine.


Glad to be of assistance.

-------------------------
Best wishes & regards

John A Thomson
allayit
 27 August 2010 02:27 PM
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jakegreenland

Posts: 66
Joined: 04 May 2009

Whilst the raw maximum data rate of 802.11n might be 300Mbps the actual throughput of a TCP stream is unlikely to ever achieve much more than 140-150Mbps [similarly 802.11g rarely gives more that 22-25Mbps] and in the real world even with systems like Meru that garauntee airtime fairness I've rarely seen real throughput of over 100Mbps.

The big question to ask is do you need the upgrade. If all you are doing is accessing the internet and already get solid 802.11G performance then unless your internet connection is faster that 25Mbps you're not going to see any benefit from the upgrade. If, however, you are streaming video around the house, moving large quantities of data on and off a NAS regularly or transferring large files between wireless PCs then it's going to help.

Finally as someone has already suggested the MIMO antenna system coupled with the fact that pretty much all 802.11N APs use diversity and multipath then if you do have signal problems it would help somewhat.

HTH

-------------------------
Jake Greenland, CEng MIET.
CCIE #22595
 08 September 2010 04:19 PM
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Lasiciae2005

Posts: 3
Joined: 01 August 2010

Hello House,
The wireless 802.11n standard has not been ratified yet you IEEE, so there no point upgrading.
 08 September 2010 04:20 PM
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Lasiciae2005

Posts: 3
Joined: 01 August 2010

Hello House,
The wireless 802.11n standard has not been ratified yet you IEEE, so there no point upgrading.

Lasiciae

Lasisi Taofik, DCE,TMIET.
 08 September 2010 05:22 PM
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lowson_i

Posts: 130
Joined: 23 June 2008

Originally posted by: PMK

Dears,



Thinking about upgrade my WiFi card from g to n standard on the PCI slot. One thing gives me small headache - what's the point to upgrade up to 300 Mbps on a card if standard PCI bus can handle up to 133 Mbps? Even assuming, that average transmission speed between a WiFi card and a router is much lower, say 200 Mbps, there's still much overhead which will wait in a buffer. The only point for such upgrade - what I can see - is that actual average speed for WiFi is around 150 Mbps (or lower) and therefore might roughly match PCI bus speed. Am I right?



Cheers, Pete


The difference is the "b"! 300 Megabits per second and 133 megabytes per second are different speeds. See here for more information on the general PCI bus.

There are 8 bits in a byte. thus 133 x 8 = 1064 Megabits = 1 gigabit.
Also a PCI bus could be 64bits (8 bytes) wide. Thus can have a burst speed of 1064 Megabytes = 8512 Megabits = 8.5 gigabits!

Also the marketed speed is the one way communcation speed. Each packet sent on a network requires acknowledgement, this reduces the practical speed by half before any error bits are added and or error handling by resending of packets etc. Thus I'd expect a 100Mb (megabyte) file to transfer across a 100mbps (megabit) network to take about 20 seconds.
Point-to-point communication of the "marketed speed" is correct but can be likened to giving the rpm of a tyre when quoting the top speed of a car!

-------------------------
Ian Lowson MIET

Do or do not, there is no try!

Edited: 08 September 2010 at 05:31 PM by lowson_i
 09 September 2010 09:27 AM
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jakegreenland

Posts: 66
Joined: 04 May 2009

Originally posted by: Lasiciae2005

Hello House,

The wireless 802.11n standard has not been ratified yet you IEEE, so there no point upgrading.

Lasiciae
.


The 802.11n standard was ratified by the ieee a year ago on september 11th 2009 as per the announcement from the IEEE found at

http://standards.ieee.org/anno...endment_ratified.html

Even then the 2007 draft N standard was pretty complete, to the point that the WiFI alliance were certifying gear based on it, and any decent 802.11n device will have had a software based Radio that would allow implementation of the final specification through a simple firmware change so that should never have been regarded as a barrier to upgrading if the requirements are such that it demands the speed.

-------------------------
Jake Greenland, CEng MIET.
CCIE #22595
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