Using iburst with low signal

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fergus

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I have a UTC (pcmcia version) and this morning I was at a location probably on the fringe of iburst coverage - one of those light green areas. My signal showed as 30 - 40%. I managed to connect but the connection was largely unusable. The frame error rate was all over the place going from 40 to 70% or higher. I managed to download some emails but that was about all I could do, not even surf the web effectively. Is there anything one could do to make the connection more usable when you've barely got signal (besides getting an antennae - I rarely am far from a tower, its only once in a while so its not worth my while getting an antenna for that). What about that MTU thingy? Would fiddling with that make a difference?
 
I would recommend an external aerial - oh hold on you have a UTC ??? Ask Kei i think he would probably have more knowledge about this than me. Sorry .
 
MTU doesn't help at all under those circumstances... I wouldn't even bother in low signal condition as NOTHING helps. I've fiddled and tried! The problem is that if you're too far away the basestation cannot receive your UTD's transmissions without excessive errors and that's why everything falls apart.
 
Kei mate , would an external aerial on the UTD help this at all ? I am quite shocked at how my service has improved on installing the aerial. I know he has the UTC which i assume is pretty k@k but would it help with a UTD ? Thanks
 
fergus said:
What about that MTU thingy? Would fiddling with that make a difference?
Click to expand...
optimal MTU doesn't work on Iburst like it does with fixed line broadband where you set the packet size as high as you can in order to recieve faster speeds, the pings change constantly and so does the packet fragmentation size, meaning with iBurst the point of MTU isn't to set it high to optimize packets for faster speeds it is to set it low enough so it never fragments, you sound like you might recieve packet fragmentation on the default settings (although some applications and network libs will try dynamically calculate the best MTU at the time you create a connection), try set the MTU to 1352, but this won't help people when thier connection is fine it will just help people who get constant packet fragmentation.

If you were wondering what MTU is its the max transmission unit AKA the size of the packets you send, if the packets are too big and get fragmented you have to send the data twice which causes slow down.
 
Yes it would. IMHO the UTD is capable of much more than the UTC and has probably got a better RF subsystem i.e. more powerful transmitter
 
slimothy said:
optimal MTU doesn't work on Iburst like it does with fixed line broadband where you set the packet size as high as you can in order to recieve faster speeds, the pings change constantly and so does the packet fragmentation size, meaning with iBurst the point of MTU isn't to set it high to optimize packets for faster speeds it is to set it low enough so it never fragments, you sound like you might recieve packet fragmentation on the default settings (although some applications and network libs will try dynamically calculate the best MTU at the time you create a connection), try set the MTU to 1352, but this won't help people when thier connection is fine it will just help people who get constant packet fragmentation.

If you were wondering what MTU is its the max transmission unit AKA the size of the packets you send, if the packets are too big and get fragmented you have to send the data twice which causes slow down.
Click to expand...
Thanks for that slim. I vote slim our resident iburst guru!!

Ok, so how do I change the MTU :confused:
 
MTU means nothing if your RF QOS is bad it simply doesn't help. MTU is at a much higher level of abstraction than the medium itself. The medium carries a formatted datastream which encapsulates the TCP/IP packets.

What this means is, if you are far away from the basestation your data is being lost due to corruption as opposed to your data being lost due to crappy MTU setting. There is a big differenece between your packet being fragmented or dropped due to MTU and your packet being ruined by the basestation receiving a noisy signal from your UTD due to antenna issues. That is why I can't see MTU helping if you have problems with reception. Fix the reception problem first, then the MTU problem.
 
Ok, so how do I change the MTU
Click to expand...

use DrTCP

or

add "MTU" key to your windows registry under services/tcpip and give it a value of 0x578 (=1400) or as per what value you wish.
 
The probability that small packets will be corrupted is probably less likely than that of larger packets, so it may be worthwhile experimenting with smaller MTU's
 
if you have a bad quality of signal then your pings are slower and the packets will fragment at a smaller size, which is why in that case you wanna set the MTU low.

as I recall seburn I think it was (or swordfish, someone with a 's' nickname) had really bad signal and they changed thier MTU to a lower value which obviously meant less packet fragmentation and they managed to double thier speed, albeit 200kbit or so but it is still much better than 60 - 100kbt. But like I said if your connection works at an acceptable level and you are looking to MTU to optimize your connection for speed, think again unless you use a less dynamic connection like ADSL.
 
Kei said:
use DrTCP

or

add "MTU" key to your windows registry under services/tcpip and give it a value of 0x578 (=1400) or as per what value you wish.
Click to expand...
Thanks for the tip Kei and everyone else. I'm back home now (+/- 50 meters from tower :)) but when I'm out and about again I'll try play with the MTU and see what happens.
 
just a quick note although in a few cases with iBurst MTU can help if you ever find yourself calling the helpdesk and getting told to change your MTu please take that as a synonim for 'i don't know whats wrong but i'm going to pretend I do'
 
fergus, i have the desktop if you wanna swop it for the pcmcia card
 
Pcmcia Card and external antennae

fergus said:
I have a UTC (pcmcia version)
Click to expand...

One can use an external antennae on the UTC [pcmcia card], look on the side of the card there is a plastic cap, open it and plug in a pig tail.
 
ok i might be a bit off topic but would someone tell me whats the best for getting a best speed....

I have UTD modem connected to Northcliff
Signal 100% non-stop....(some times during download the green leds turn off and come back again)
Error Frame rate : from 0.00% - 30%
Packet Size:MTU 1352 bytes
Size of receive Window: 65000 bytes

Speed: uncapped from 120kbps-700kbps
Speed: capped from 20kbps-62kbps

Would someone give me advice is my settings right or not? or at least are they looking fine or bad?
 
That was me slim -- MTU did double my speed, but it neva quite fixed the problem -- That was due to being able to reposition my arial in another direction (I used to only get any signal in a wierd direction pointing away from any tower. When I tryed about a month later in one of the previously tryed position (I was actually trying all the time) I got signal and speed and low pings.

Low signal can be used according to Shaun Green - he got faster(70kBytes) speed at one customer location pointing in a direction that got only 3 lights signal than another direction with 5 lights(5kBytes or less). But you can only test to see.
 
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