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Mobile Skype: Quality Issues?

VOIP peer-to-peer pioneer Skype on Tuesday made a big move by porting its popular desktop VOIP client to certain wireless handhelds. Sounds neat, but now that the news has digested, the big question appears to be: Will it really be worth it?

Skype's introduced a PDA version that will work with 802.11b-enabled Pocket PC handhelds with more than 40 Mbytes of memory onboard (see Skype Me? Skype You! on the regular Skype client).

In theory, this is an application that enables users to -- at least partially -- bypass wireless carriers: If users live in an area with plentiful WiFi hotspot access and all their friends and family use Skype.

That's a big if, if you consider the nature of hotspot coverage when compared with traditional mobile networks: It's spotty, at best...

How spotty? Get all the details on Unstrung.

— Dan Jones, Site Editor, Unstrung

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dljvjbsl 12/5/2012 | 1:55:51 AM
re: Mobile Skype: Quality Issues? Yep. data propellerheads? You mean the ones that created SONET? CO switching? Unix? DWDM?

Wow, and you stormed the beaches at Normandy, too? Anything else you'd like to take credit for


Technonerd, he was just mocking you.

The technologies that he mentioned all came from the telephone industry. They came along with the dedication to service, quality, customers that was taught to me when I joined the industry those many years ago.
technonerd 12/5/2012 | 1:55:56 AM
re: Mobile Skype: Quality Issues? Yep. data propellerheads? You mean the ones that created SONET? CO switching? Unix? DWDM?
Wow, and you stormed the beaches at Normandy, too? Anything else you'd like to take credit for?
mavericktel 12/5/2012 | 1:55:59 AM
re: Mobile Skype: Quality Issues? dljvjbsl,
Yeah he's probably a troll with too much time on his hand. A Dilbert. He doesn't even understand the basics of transmissions yet he acts like he's some old school Bellhead. He's like your weird Uncle who says things and no one bothers to challenge him because he just barks and eventually you realize he's loony.
mavericktel 12/5/2012 | 1:55:59 AM
re: Mobile Skype: Quality Issues? That's an obvious point technonerd doesn't understand. If you don't even understand TCP/IP and why UDP is the only choice rather than any connection-oriented protocol since it has lower "overheard" in terms of getting your voice encapsulated packets from one endpoint to another, then trying to enter the debate is moot.
My understanding is that UDP is best for packet video conferencing because dropped packets aren't retransmitted. I can hire people to figure out the rest of it.

Hire people. LOL. You sort of got it right.


TDM is simply Time Division Multiplexing. PCM is Pulse Code Modulation. Then we have to discuss sampling ( 2x the frequency minimum per Nyquist theorem), companding, and then we arrive at mu or a-law for basically relying on a log-type scaling to capture voice samples. This is all part of circuit switching.
We don't have to discuss any of these things. Unless, by chance, we are data propellerheads wishing to hide behind tech-talk to avoid the real issues at hand. Gotta admit, you guys are good at that.

Why not? Can't even understand Old School voice?

The PSTN is built upon TDM with its DS hierarchy.Even SONET rings which CO's sit on as nodes rely on SONET's (US version) basis on the DS3 formatas the basic payload for its payload envelope.

That's why gateways are required to hand off voice traffic to the PSTN. These boxes have to accept let's say PRI voice T1 circuits from the Telco and they also rely on codecs to do TDM/VoIP conversion.
O.K., now what was the point of going through this? Because I used the "map to" insead of "convert?" Geez, no wonder data propellerheads are such dweebs.

Yep. data propellerheads? You mean the ones that created SONET? CO switching? Unix? DWDM?
lastmile 12/5/2012 | 1:56:04 AM
re: Mobile Skype: Quality Issues? Mobile quality issues are really not of great concern to Skype at this time. Skype mobility is an offshoot of the initial success of the original P2P Skype. The quality is astounding and there is a steady increase in the number of users. I have noticed figures as high as 350,000 at any one time.
350,000 is by no means a small number. The number of users are far in excess of that figure.
Let us not discuss quality issues for stuff that is free.


aswath 12/5/2012 | 1:56:15 AM
re: Mobile Skype: Quality Issues? So the total bandwidth upstream is reasonable, unless there are an awful lot of subscribers/node.

The other liming factor is the backhaul bandwidth available from CMTS. I read somewhere that in South korea the ratio between backhaul interface and the access interface is very high compared to US. Can anybody provide any empirical data? (Apparently it was stated in WTF 2004 hosted by Isenberg.)
fgoldstein 12/5/2012 | 1:56:19 AM
re: Mobile Skype: Quality Issues? 348> The upstreams on the MSO DOCSIS plant are fairly small pipes and you can't do many simultaneous VoIP sessions using G.711 uLaw codec technology.

Well, not really a problem in typical use. While a DOCSIS 1.1 upstream is limited in bandwidth (typically set to 5 Mbps, often 2.5M), it's common for a CMTS to have four upstream carriers per downstream. So the total bandwidth upstream is reasonable, unless there are an awful lot of subscribers/node. (Okay, we do know of some such cable operators.) DOCSIS 2, of course, provides for much more upstream bandwidth, provided the modems are also at 2.0+.
dljvjbsl 12/5/2012 | 1:56:22 AM
re: Mobile Skype: Quality Issues?
O.K., now what was the point of going through this? Because I used the "map to" insead of "convert?" Geez, no wonder data propellerheads are such dweebs.


I promised myself that I would not point out any of your howlers again but this is too juch. Have you nay idea about transmission and signalling? You have not given any indication that you know anything about encoding or switching. Indeed you have given every indication that you do not.

Tell us teh truth. is this just one big troll?
stephenpcooke 12/5/2012 | 1:56:44 AM
re: Mobile Skype: Quality Issues? mavericktel wrote:

The PSTN is built upon TDM with its DS hierarchy. Even SONET rings which CO's sit on as nodes rely on SONET's (US version) basis on the DS3 format as the basic payload for its payload envelope.

That's why gateways are required to hand off voice traffic to the PSTN. These boxes have to accept let's say PRI voice T1 circuits from the Telco and they also rely on codecs to do TDM/VoIP conversion.


SONET is my backyard. DS3 is A supported payload but so is anything that is 'bulk-mapped' providing that you have a mapper card to do the mapping/de-mapping for you, it can be literally anything. ATM has its own standardized mapping into an STS-1/STS-3c/STS-12c/..., DS-1 has its own, Packet Over SONET (POS) has its own, etc.

Yes, the PSTN is based on T-circuits and SONET transport but neither of these limit the choice of higher layer traffic other than maximum provisioned bandwidth, which can be increased by adding more equipment/wavelengths, etc. as necessary. Most newer SONET equipment has cards that do all sorts of mapping/de-mapping and it is quite likely that some equipment providers will leverage their installed base to offer additional capabilites for quite some time. The only protocol conversions necessary are due to the class 5 switch, not the transport mechanisms.
technonerd 12/5/2012 | 1:56:44 AM
re: Mobile Skype: Quality Issues? Some technology will succeed. ATM to the desktop? Ferggetaboutit.
ALERT! Religious debate among engineers dead ahead!


It's just the 'Net and applications are not as simple and closed off as the PSTN so potential security exploits are always a problem. Years ago, a very bright fellow who was an old school data comm veteran mentioned that VoIP will open up a can of worms in terms of security issues.
Just wait until these enterprises that have moved to VoIP have their phones killed by some 16-year-old hacker; the "consultant" who sold it to them is nowhere to be found; and the IT staff wants to shut the whole thing down for the rest of the day.


Video is not the killer app. It's VoIP.
The sole reason for VoIP is regulatory arbitrage of one sort or another.


If consumers want silly cameras stuck in their phones, so be it.
You mean you're not doing up-skirt photography with your cellphone? What kind of engineer are you? Don't you realize you could be locked out of the next IEEE meeting?!
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