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Bobcat79
Premium
join:2001-02-04

Short or Long Preamble?

I'm switching from a D-Link to a ZyXEL wireless router, and I noticed that the default settings for the preamble are different. The D-Link defaults to short, and the ZyXEL defaults to long. Which is better?

The routers' documentation is not much help, in particular:

said by D-Link :
High network traffic areas should use the shorter preamble type.
said by ZyXEL :
Short preamble takes less time to process and minimizes overhead, so it should be used in a good wireless network environment when all wireless clients support it. Select Long if you have a 'noisy' network...

Use long preamble... to provide more reliable communication in 'noisy' networks.
So one says to use short preamble in high network traffic areas (which I would consider to be noisy environments), but the other says to use long in noisy environments. Any opinions here?


funchords
Hello
Premium,MVM
join:2001-03-11
Yarmouth Port, MA
kudos:6

ZyXEL doesn't mean traffic, they mean interference (either natural or man made).

The preamble is a length of null signal before data. It gives time for receivers on the network to detect the signal and prepare to receive the data.

Short preamble:
Ummmmmmmmmmm, DATADATADATADATA

Long preamble:
Ummmmmmmmmmmmmmmmmmmmmmmm, DATADATADATADATA

In most cases, short is more efficient. If you have a station that is having trouble downloading, setting preamble to long should be a solution to try.
--
Robb Topolski -= funchords.com =- Hillsboro, Oregon USA
~ Keeper of the D-Link FAQ ~ Did you Search? ~ More features, Free! Join BBR! ~


Bobcat79
Premium
join:2001-02-04

I'm having much better results with the ZyXEL, which defaults to long preamble, than I did with the D-Link. I'll have to try the ZyXEL w/ short and see what happens.

Although it doesn't apply to my situation, if there were multiple routers using the same or overlapping channels, would using long preamble be best?



funchords
Hello
Premium,MVM
join:2001-03-11
Yarmouth Port, MA
kudos:6

said by Bobcat79:

Although it doesn't apply to my situation, if there were multiple routers using the same or overlapping channels, would using long preamble be best?
Not automatically, but yes, probably.

I kinda wonder if all this MIMO and Pre-N stuff that has been rushed to market will cause the rest of us to switch to long Preamble.
--
Robb Topolski -= funchords.com =- Hillsboro, Oregon USA
~ Keeper of the D-Link FAQ ~ Did you Search? ~ More features, Free! Join BBR! ~

Bobcat79
Premium
join:2001-02-04

I switched to short preamble, but didn't notice any difference. Speed during a LAN-LAN FTP transfer was the same. I think I'll stick to long, since I don't see any benefit to using short.

Another question: What is IAPP? My ZyXEL router has it enabled. If I'm only using one wireless router / access point, should I disable IAPP?



funchords
Hello
Premium,MVM
join:2001-03-11
Yarmouth Port, MA
kudos:6

IAPP allows authorized wireless stations to move from one AP to another without interruption. In your case, it won't do anything.

I'm lazy. My practice is to try to stay as close to the defaults as I can. It makes it easier to start over, if necessary. Trying to remember all the tweaks I've made, and applying them and waiting for the reboot to finish, is tiresome.

I also figure that most of the final testing that went into a particular firmware was probably done at or near the defaults, and any support that I may be given will probably assume that I'm running at or near the defaults.
--
Robb Topolski -= funchords.com =- Hillsboro, Oregon USA
~ Keeper of the D-Link FAQ ~ Did you Search? ~ More features, Free! Join BBR! ~



Vchat20
Landing is the REAL challenge
Premium
join:2003-09-16
Columbus, OH
reply to Bobcat79

This is actually an interesting topic. I own a DI-524 myself and alot of those wireless settings I have left default without really looking into what they do. I am currently running into a problem here where even though my laptop is no more than about 20 feet from the router going through a ceiling/floor, my signal often bottoms out to as low as 1mbit, 'extremely low' (according to WZC). I have yet to determine if its a case of extreme interference or anything like that (although I did spot 2 other AP's nearby but both are on distanced channels. im on channel 11 and the others show on 1 and 6 respectively). Would setting the router from its default of short preamble to long preamble help me out or would it pretty much make no difference?
--
I reject your reality and substitue my own! -- Adam Savage, Mythbusters


Bobcat79
Premium
join:2001-02-04

You could trying changing to long preamble. If it doesn't help, it's easy to change it back.

You might also try turning off encryption temporarily to see if it's related to that.



funchords
Hello
Premium,MVM
join:2001-03-11
Yarmouth Port, MA
kudos:6
reply to Vchat20

Antennas radiate much more power from the sides then they do from the tip and base. Since you're above the antenna, you should move the antenna to favor your direction.

On the DI-524, move the antenna so it runs parallel with the floor/ceiling instead of the normal direction parallel with the walls.

I wouldn't change any configuration settings unless you are experiencing an actual problem -- such as frequent disconnects or slow upload or slow download. Basically, I'm saying don't worry about the strength indicator unless it is accompanied by an actual symptom.

If you are having those symptoms along with a low signal, then it may help to set preamble to long, you could also set the fragmentation threshhold to 50% or 75% of the default value.
--
Robb Topolski -= funchords.com =- Hillsboro, Oregon USA
~ Keeper of the D-Link FAQ ~ Did you Search? ~ More features, Free! Join BBR! ~


vincentfox

join:2003-03-18
Davis, CA
reply to Bobcat79

The "long and short of it" from a multi-vendor perspective, is that there are cards that don't like short. I operate a small WISP and set all my AP to long preamble.