3G at large public events

Plebs

Does the bandwidth/latency drop considerably at football matches/rock festivals/etc.?

Do Meteor for example, have portable base stations that they bring in for the afternoon?

watty

The contention can indeed be high with phone calls only and no data capacity left. But such places usually have dedicated masts. They don't bring in more.

Patrickswell is a very small village. But there is a mast at Garda station, a Mast at the Cork/Tralee road junction and of course a mast at the Limerick Race course.

Latency rises toward 2000ms for data as there are more users and speed drops as the bandwidth is a fixed 5MHz per mast sector. Each operator only has 3 x 5MHz duplex channels nationally. Hence there is also a limit on power or masts / modems/ Handsets interfere and reduce the speed and capacity even more.

Voice has priority as it has 100x to 300x the value per Euro spent compared to Data.

Plebs

watty wrote: »

The contention can indeed be high with phone calls only and no data capacity left. But such places usually have dedicated masts. They don't bring in more.

Patrickswell is a very small village. But there is a mast at Garda station, a Mast at the Cork/Tralee road junction and of course a mast at the Limerick Race course.

Latency rises toward 2000ms for data as there are more users and speed drops as the bandwidth is a fixed 5MHz per mast sector. Each operator only has 3 x 5MHz duplex channels nationally. Hence there is also a limit on power or masts / modems/ Handsets interfere and reduce the speed and capacity even more.

Voice has priority as it has 100x to 300x the value per Euro spent compared to Data.

Do you think it would be possible to send small amounts of data disguised as voice? Can Android OS for example do this? I'd like to achieve very low latency. My bandwidth requirements aren't very high...

watty

You can't have low latency on Mobile. It's not technically possible. (Pings below 50ms is Broadband quality, ideally less than 15ms is low latency).

If you disguised data as voice it would be less than 2kbps so as to be not messed up and you could only connect to another phone number, not the internet. Of course the other phone number could be dialup internet and then you would be emulating an analogue Modem. Reliabilty would be terrible, latency poor and I doubt if the Internet POP would go as a slow as 1200bps or so needed.

I'm not sure you can even go as fast as 1200bps or 2400bps putting analogue modem via the voice channel. GSM has a native modem at 14,400bps and GPRS uses a variable speed X.25 like connection at about 40kbps to 50kbps, very high latency.

Also voice traffic per Mbyte, at 14.4kbps data rate is 100x to 300x more expensive than most data packages.

Conclusion:
You can't do it.

Plebs

watty wrote: »

You can't have low latency on Mobile. It's not technically possible. (Pings below 50ms is Broadband quality, ideally less than 15ms is low latency).

If you disguised data as voice it would be less than 2kbps so as to be not messed up and you could only connect to another phone number, not the internet. Of course the other phone number could be dialup internet and then you would be emulating an analogue Modem. Reliabilty would be terrible, latency poor and I doubt if the Internet POP would go as a slow as 1200bps or so needed.

I'm not sure you can even go as fast as 1200bps or 2400bps putting analogue modem via the voice channel. GSM has a native modem at 14,400bps and GPRS uses a variable speed X.25 like connection at about 40kbps to 50kbps, very high latency.

Also voice traffic per Mbyte, at 14.4kbps data rate is 100x to 300x more expensive than most data packages.

Conclusion:
You can't do it.

Hey! Never say never! I'd love to see a "soft" dial-up modem for Android that connects over the voice channel. I mean companies like blue-face can get voice off the internet, so I'm sure it *could* be done. Does voice get a higher priority than data? Does a voice channel get guaranteed bandwidth? Would be a total hack, but if you really needed low latency/low bandwidth in your application, it could be an option.

Also, data may be x100 to x300 more expensive for the operator, but surely for the customer, it's a function of the plan?

I'm getting ok ping results when I ping google: min ~200ms, average ~350ms, max ~700ms.

I've only got one or two bars on my phone. I'm hoping when I get my external antenna, I can knock between 20% and 50% off those figures.

jor el

Plebs wrote: »

Hey! Never say never! I'd love to see a "soft" dial-up modem for Android that connects over the voice channel. I mean companies like blue-face can get the voice onto the internet, so I'm sure it *could* be done. Does voice get a higher priority than data? Does a voice channel get guaranteed bandwidth? Would be a total hack, but if you really needed low latency/low bandwidth in your application, it could be an option.

But you won't get low latency, just low bandwidth by doing this. Voice is always prioritised over data on mobile phone networks, but you're guaranteed nothing. Ever had a phone call drop out, especially at a large public gathering? It can be impossible to send a text sometimes.

Plebs wrote: »

Also, data may be x100 to x300 more expensive for the operator, but surely for the customer, it's a function of the plan?

It's expensive for the operator which is why they won't want you doing this.

Plebs wrote: »

I'm getting ok ping results when I ping google: min ~200ms, average ~350ms, max ~700ms.

I've only got one or two bars on my phone. I'm hoping when I get my external antenna, I can knock between 20% and 50% off those figures.

The antenna will not improve your pings, just your signal strength. A stronger signal does not mean you'll see any improvement on any of your stats, it just means you have a better signal. Ping, speed, disconnects will likely remain unchanged.

If your plan is to stream some sort of video feed from an event using the mobile phone network then you can pretty much forget about it. It's not going to happen.

Plebs

jor el wrote: »

But you won't get low latency, just low bandwidth by doing this. Voice is always prioritised over data on mobile phone networks, but you're guaranteed nothing. Ever had a phone call drop out, especially at a large public gathering? It can be impossible to send a text sometimes.



It's expensive for the operator which is why they won't want you doing this.



The antenna will not improve your pings, just your signal strength. A stronger signal does not mean you'll see any improvement on any of your stats, it just means you have a better signal. Ping, speed, disconnects will likely remain unchanged.

If your plan is to stream some sort of video feed from an event using the mobile phone network then you can pretty much forget about it. It's not going to happen.

Not trying to stream video at all. Just events happening. For a betting application. Hence the low latency requirements.

I understand that if the latency goes over 250ms in a voice call, the callers can percieve a delay. 250ms would be great if I can get that over a network with a high level of reliability.

Using bi-directional sockets that are always open to trickle the data back and forth and work very well over WiFi/copper with very low latency. Just want to get the lowest possible latency. The large crowd could be a problem and I'm trying to get the opinions of maybe some techs who work close to the network and can help me.

So who's got the lowest latency network? Meteor/o2/vodafone/3? Can you pay for priority?

jor el

Plebs wrote: »

Using bi-directional sockets that are always open to trickle the data back and forth and work very well over WiFi/copper with very low latency. Just want to get the lowest possible latency. The large crowd could be a problem and I'm trying to get the opinions of maybe some techs who work close to the network and can help me.

So who's got the lowest latency network? Meteor/o2/vodafone/3? Can you pay for priority?

You can't get low latency on a mobile network. They're all the same, though actual performance at any time depends on the current conditions in your particular location. With lots of people will come terrible speeds and latency. Whatever it is you're looking to do, you can't do it on 3G.

Plebs

jor el wrote: »

You can't get low latency on a mobile network. They're all the same, though actual performance at any time depends on the current conditions in your particular location. With lots of people will come terrible speeds and latency. Whatever it is you're looking to do, you can't do it on 3G.

Gosh! You're so pessimistic!

Getting good latency this evening in a different location. Consistent 150ms to 200ms pings to my site over 3G. That's pretty good IMO. I'd like to keep it as far below 500ms as possible.

A steady average around 250ms with very low probability (i.e. <1%) of packets going above 500ms should be grand for my needs. I think the 3G network is capable of this with by utilizing smart network protocols and getting some help from a high gain antenna.

watty

over 80ms latency is poor.
150ms is terrible.
50ms jitter (variation) is horrific.

30ms is good
15ms is excellent

Any packet loss is abysmal.

The 3G network can't do a steady 250ms. That's not possible. It will do 90ms to 300ms with rapid variation in latency as people, phone calls and data quantities change. A very small change in number of users or kind of data they are using will create 200ms changes in latency. That's over 20 times an acceptable jitter.

mayo.mick

Would the rollout of 3.5/4g improve this? is it called hspa+? 56mbs download

BEASTERLY

mayo.mick wrote: »

Would the rollout of 3.5/4g improve this? is it called hspa+? 56mbs download

Is this planned for Ireland? Would be very good news if it was!

I would prefer to get 3mbps speed and 50ms ping rather than 30mbps and 150ms ping!

watty

HSPA+ can do 42Mbps. But it needs two channels and perfect signal and no-one else using it. So it's marketing hype.

Less than 2% of Mobile Data users see the full sector speed. ALL four Mobile operators only have 3 channels. You need 3 channels and ideally NINE to do a proper cellular system.

See 3rd table here: http://www.techtir.ie/comms/fixed-wireless-broadband-better
That shows how few people can get 21Mbps

Also this is likely % Users by cell area

Speed is for only ONE user (phone or Data) connected vs likely location
About 1% of or less locations see any improvement between 7Mbps, 14Mbps, 21Mbps or 42Mps peak speed masts.
If only THREE to Four people using the sector continiously (YouTube), then speed can be 1Mbps to 2Mbps on average per user even on a 42Mbps Mast.

BEASTERLY

Well hve a look at this link: http://www.phonescoop.com/articles/article.php?a=376

It is a recent review of various mobile internet solutions , they tested HSDPA+ , Wimax and normal 3G.

In various locations they saw massive improvements in both speed and latency in HSDPA+ comparing to wimax and normal 3G.

So watty , at the moment on o2 i'm getting 1mbps up/down and pings of 300ms+ , so you're saying I would see no improvement in my service at all if o2 switched to HSDPA+ in the morning?

According to your chart above 75% of users will see speeds of about 0.2mbps , this doesn't seem correct at all!

jor el

Plebs wrote: »

Gosh! You're so pessimistic!

I prefer realistic, but it's often similar

Plebs wrote: »

Getting good latency this evening in a different location. Consistent 150ms to 200ms pings to my site over 3G. That's pretty good IMO. I'd like to keep it as far below 500ms as possible.

Good for 3G, but not low latency. If your target is 500ms, then 3G is definitely an option, but when congestion goes up, that figure is going to rise.

Realistically, it's not going to work for you reliably. Whatever it is, it will not be stable.

watty

BEASTERLY wrote: »

According to your chart above 75% of users will see speeds of about 0.2mbps , this doesn't seem correct at all!

50% of coverage area. Its a log scale. It's 50% of users if the users are evenly distributed.

BEASTERLY

Ok so I have done some research because I tought it was strange that vodafone was rolling out HSDPA+ , but there wasn'tt a sound out of o2 or others.

I found this on the net: http://www.trustedreviews.com/networking/news/2009/12/15/O2-Deploys-LTE-In-UK/p1

Turns out that o2 are rolling out LTE in the UK , might explain why they are keeping quiet here about HSDPA+ , could they be planning LTE for Ireland once analouge TV is shut down. It would be pointless going ahead with HSDPA+ if they might be opting for LTE ina years time anyway.

Will LTE bring any big leap forward over HSDPA or is it another very smart marketing ploy?

Plebs

jor el wrote: »

Realistically, it's not going to work for you reliably. Whatever it is, it will not be stable.

You say that with such authority. I'm gonna try it on Sunday at the match in Croke Park and see what happens. The latency distribution will be very interesting.

I tried searching the web for some bandwidth vs. number of users in the cell or latency vs. number of user in the cell and I couldn't find anything.

rebel.ranter

Plebs wrote: »

Do Meteor for example, have portable base stations that they bring in for the afternoon?

Most networks will bring in temporary masts for events like Electric Picnic, Oxegen, ploughing championships, concerts at Slane, etc. Some venues that continuously host events have dedicated solutions installed.

PogMoThoin

Plebs wrote: »

You say that with such authority. I'm gonna try it on Sunday at the match in Croke Park and see what happens. The latency distribution will be very interesting.

I tried searching the web for some bandwidth vs. number of users in the cell or latency vs. number of user in the cell and I couldn't find anything.

You're gonna need this tool to show You just how inconsistent mobile internet is, its a traceroute over time that shows the fluctuations in pingtimes and packetloss:
http://www.bitwizard.nl/mtr/

Available for windows here:
http://winmtr.sourceforge.net/

Plebs

PogMoThoin wrote: »

You're gonna need this tool to show You just how inconsistent mobile internet is, its a traceroute over time that shows the fluctuations in pingtimes and packetloss:
http://www.bitwizard.nl/mtr/

Available for windows here:
http://winmtr.sourceforge.net/

Network Tools is included with Ubuntu 10.04 by default.

I'm most interested in latency over WebSocket protocol for which I've written some code that outputs some gnuplot box plots.

PogMoThoin

Plebs wrote: »

Network Tools is included with Ubuntu 10.04 by default.

But mtr isn't, "sudo apt-get install mtr"