Why is there no latency in local phone calls?

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Ultimate Geek

#46251 15-Sep-2006 16:59

Fraktul: Was that sold from Telstra Clear or wholesaled from them out of interest?

This connection was ordered through TelstraClear business and is using the old clear.net 'loop not UBS

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Fraktul

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#46253 15-Sep-2006 17:26

barf:
Fraktul: Was that sold from Telstra Clear or wholesaled from them out of interest?

This connection was ordered through TelstraClear business and is using the old clear.net 'loop not UBS

Is it PPPoE or PPPoA?

antoniosk

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#46257 15-Sep-2006 20:37

TelstraClear Business ADSL is PPPoA.

Internet is also sometimes supplied via 'other' technologies (wireless, frame relay, fibre), and these are presented as PPPoE.

paradoxsm

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#46279 16-Sep-2006 19:37

Enjoy the lovely instant, clear communications while they last alright, I must admit while I'm happy with italk and G.729 it does seem robotic and so artificial compared to a true land line, The latency on a mobile call especially mobile to mobile ins something chronic,

A bing question.......
Why in this day and age as data speeds rise and the capabilities are increased are we seeing the quality of our voice calls dropping?
I would have expected 44khz or even 22khz calls as commonplace now, Even in tech I programmed up somthing which offered 44khz sampling at 14k. it was not superb or fast but worked.

UMTS took a step forward with using AMR at 13k.
GSM is actually quite acceptable at 13k (EFR) theold 8k rate was pretty bad, Remember those telecom ads where the guy used his golf club to drive his GH021 Ericsson Bellsouth phone into the water? lol
CDMA took a large step backwards with EVRC at 8k Known for tinnyness and loss of speech)
CDMA 13k QCELP is a lot better sounding until packetloss kicks in where it clucks like a bunch of drunk turkeys.

NGN telecom will probably use G.729(low birate, high intellibility CELP) and block G.711 (PCM)
italk did support G.711 (uncompressed PCM) so it was kinda like landlines asides the latency, and jitter was a problem.

simon14

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#46280 16-Sep-2006 22:34

VoIP would get better once we can turn interleaving off though?

antoniosk

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#46289 17-Sep-2006 15:29

simon_nz90: VoIP would get better once we can turn interleaving off though?

Interleaving never really had a heavy impact on VOIP - it st*ffed the gaming community more.

VOIP will get better once the telco - Telecom - ups the transmission backhaul and minimum bandwidth per user. I saw in the weekend they were advertising their new faster speeds being available 26/10 - but if some dslams are still connected on 2mb/s backhaul....

I notice as well that FS/128 is completely flat rate - no overage - but FS/FS does have an overage component.

But where is Telecom's incentive in this? to finally marginalise it's retail business and let every twit with a softswitch into the country to offer NDD at 2c a minute?

I think the new BB rates are going to knacker every ISP who doesn't have some form of alternate network - the margins left in the UBS offer are so slim it's ridiculous.

Fraktul

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#46292 17-Sep-2006 16:41

antoniosk: TelstraClear Business ADSL is PPPoA.

Internet is also sometimes supplied via 'other' technologies (wireless, frame relay, fibre), and these are presented as PPPoE.

Why would you use PPPoE over Frame Relay? This would require you tunnel Ethernet over the Frame in the first place. Also few fibre implementations in NZ use PPPoE either:

Connect 4 Citylink- Source routed from ISP
Corp 10,100,1000 - Cant remember off the top of my head.
Telstra Clear Metro IP - majority is layer 3, source routed or via OSFP or other routing protocol back into ISP when wholesaled. Have never asked the network guys there if they use PPPoE for retail. Pretty rare you will ask for layer 2, fifty million subinterfaces in your aggregation router sucks.
PON, OO - PP VLANS at exchange with VFRs for distrubution into MPLS cloud, MAC Auth.
Vector - Cant remember of the top of my head either but I think layer 2 only.

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barf

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Ultimate Geek

#46295 17-Sep-2006 21:07

Fraktul: Is it PPPoE or PPPoA?

It's PPPoE ADSL2+
AFAIK TelstraClear have an IP-core network, so frame-relay is probably only used for UBS and between ADSL modem and DSLAM

hmm maybe UBS should stand for Unreliable Broadband Speeds

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Fraktul

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#46298 17-Sep-2006 22:22

barf:
Fraktul: Is it PPPoE or PPPoA?

It's PPPoE ADSL2+

Interesting, retail have been very slow on offering this product. They have had it in production for best part of 20 months however..

AFAIK TelstraClear have an IP-core network, so frame-relay is probably only used for UBS and between ADSL modem and DSLAM

hmm maybe UBS should stand for Unreliable Broadband Speeds

Huh? I think you might be getting confused with DSL's super frames. Frame Relay does not really have anything to do with ADSL.

barf

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#46299 17-Sep-2006 23:10

i was under the impression the PVC layer in PPPoATM was a type of frame relay, just not exactly a SDI/G.703 frame-relay, but i'll stand corrected.

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Fraktul

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#46323 18-Sep-2006 10:22

There are some similarities in the concepts, thats about it.

Old Grey Geek

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#46327 18-Sep-2006 11:24

Going back to the original post "Why is there no latency in local phone calls?"
Local calls on POTS (plain old telephone system) are analogue so they "travel" at close to the speed of light where as any digital network, be it mobile or VOIP, is encoded then decoded (hence CODEC) and is delayed by system clocks, wait times, interleaving and many other network delays, latency.
You will notice this if you compare a digital TV next to an analogue TV showing the same station or even the audio out signal from a digital TV compared to the TV speaker.
I thought we all knew this stuff?

Bung

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#46330 18-Sep-2006 11:58

Only analogue on the local copper, for last 20 years most exchanges and trunks between exchanges in NZ have been digital. But we all knew this :-)

Fraktul

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#46331 18-Sep-2006 12:00

Very true, back in 1940. Most PSTNs have been digital for all by the last mile for quite some time. Even if A and B parties are off the same exchange its not direct analog.

Also the speed of light, the speed of any electromagnetic propogation, varies substantially by medium.

Regarding the digital tv, thats because it goes through another encoding process true but also involves usually several intermediate transmission points and the extra distance involved. If your analog signal had to propogate down a very wiggley wire for up to space for satellite transmission instead of the straight parth transmission from a terrestrial transmitter you would be able to measure the extra latency also.

Good quality DSPs, correctly designed, should induce very minimal latency. All else equal you most likely wont be able to pickup the difference between an analog signal and an analog signal with anaglog -> digital -> analog conversion with the human ear in a blind test.

It is this process possible happening multiple times, serial delays, link congestion etc as you also point out which is what gives you the delay in VoIP

Old Grey Geek

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#46378 18-Sep-2006 15:32

Bung: Only analogue on the local copper, for last 20 years most exchanges and trunks between exchanges in NZ have been digital. But we all knew this :-)

I think we were talking about local calls

Fractul: Also the speed of light, the speed of any electromagnetic propogation, varies substantially by medium.

"The speed of a charged particle in copper is very slow: about 0.01 cm/s.
At this rate, it takes about 3 hours for a charge to travel about one
meter. The electric field (signal) travels at the speed of light through
copper. The charge is not carrying the information, per se, but the
information is transmitted by the electric field. It is like a molecule of
water does not travel across the ocean, but the wave does."
from: http://www.newton.dep.anl.gov/askasci/phy99/phy99488.htm

But then there are arguments about this as there is about everything it seems.

Fractul: Regarding the digital tv, thats because it goes through another encoding process true but also involves usually several intermediate transmission points and the extra distance involved. If your analog signal had to propogate down a very wiggley wire for up to space for satellite transmission instead of the straight parth transmission from a terrestrial transmitter you would be able to measure the extra latency also.

What I meant was; 2 TV's in one room, same, analogue, signal. The delay you will notice, in the audio, is soley due to the DSP. And, the losses on your wiggley wire would be so much you would be waiting till way past bedtime before you gave up.

So there NAH x 5
;-)

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