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Is VOIP Over WLAN DOA?
prostoalex writes "Voice-over-IP in Wireless LAN environment - a futurist's dream of always-on always-connected service. Guy Kewney from eWeek tests the technologies that try to satisfy this market today and finds nothing but disappointment. " The best result we got was that just once, I heard his voice with a delay of about 15 seconds, saying "You just have to speak up!"--which was part of a 20-second burst of speech from him. The rest was lost.""
Well i have used stantaphone over my home wifi worked ok (1-1.5 sec delay) normal for anything of that nature.
802.11 standard was modeled around having a CSMA/A algorithm that tried to be as much like Ethernet as possible. There is no provision in the BASIC standard to provide for clients to shut up for higher priority voice clients at all! This means that a data client can blow the voice guy to kingdom come.
There are extensions to the 802.11 standard like 802.11e and WME that will allow priority queuing and some minimalistic scheduling to take place. Other companies play tricks with the protocol to allow for voice clients to perform better under the BASIC standard but there are drawbacks.
In the end, it is too early to judge VOIP over WLAN because clients and access points have yet to adopt extensions to the basic standard.
-Ho
VOIP over WLAN is DOA? WTF? I'm going back to DTMF over POTS ASAP!
In Soviet Rush, today's Tom Sawyer gets high on you.
IMHO the VOIP RFC for WLAN was OK, FWIW.
But IIRC, its FUBAR WRT the FCC and maybe IRS.
A FOAF says the MSFT will BSOD it b/c its w/o DRM.
IAC, the US DOJ, FBI, CIA & IRS also dislike it.
So FTTB VOIP WLAN is SOL. HTH... HAND! -JPH
I've used Skype ( http://www.skype.com/ ) quite extensively (windows only at the moment but they have a linux version in the works) over my LAN and via my cable connection to people ranging from 160 miles away to people in other countries.
Sure, there is a slight "houston, this is tranquility base) type of delay, but within a couple of hours use this becomes second nature.
Many of the calls I made exceeded one hour in duration, god alone knows what they would have cost via telephone.
Every call was end to end encrypted, yes, even the voice signal.
To call what is effectively a brand new technology which is basically still in public beta DOA is nothing other than complete and utter bollocks and a sure sign that whoever is applying such a label to VOIP is either...
a/ terminally fucking clueless
b/ blunkett (UK) / cheney or rice (US) / a telco shitting themselves.
BT has just started rollout of 21CN which will involve the ENTIRE NETWORK moving over to IP based traffic routing, so some 30,000,000 telephones in the UK alone will be, guess what, VOIP within a few years... link here http://www.theregister.co.uk/2004/06/09/bt_ip_net
Slashdot is rapidly declining to the point where Pissy World (UK) / Fry's (US) sales staff will start calling what THEY percieve as stupid clueless customers as "slashdotters" as a term of generic abuse.
"News for Nerds" ??? Give me a fucking break, Twaddle for Teletubbies is more accurate a decription of the content lately.
http://slashdot.org/~GuyFawkes/journal
You can simulate a VoIP call and get the MOS voice quality score. So if you want to see how your Wireless setup fares, visit testyourvoip.com.
Even if you don't care about VoIP, it is a useful test of the latency and bandwidth of your connection. VoIP is pretty sensitive to late packets so this tool highlights connectivity problems.
-ben
First of all, full disclosure: I work at Avaya, for their security practice. What I'm about to say may seem pretty self-serving for the company, but I can only hope my posting history establishes me as some sort of credible source.
Second warning -- I'm actually raving about my own company's gear here. I'm way more likely to get in trouble over this, but heh -- can't let an entire nascent industry get tarred over a temporary generation of *ahem* lesser performing equipment.
So, warnings aside -- I was at Hivercon last year. Hivercon's a fun show, set in the middle of Dublin, Ireland (which, btw, is a fantastic city.) I'm sitting there, on:
1) My laptop
2) Wireless
2.1)HOTEL wireless
3) VPN (IPSec w/ 50% packet overhead!)
4) An international link
5) VoIP into a conference call
By all rights, the quality should have been awful. I mean, it had every right to be...
Now, we have VoIP at home too -- Vonage, to be specific. Our Vonage link runs over an 1.5mbit SDSL line provided by Speakeasy/COVAD, is QoS'd at our firewall, and connects directly to our home telephone wiring.
The quality on the international, wireless, IPSec'd, laptop'd conference call through my Avaya softphone exceeded what I was used to from our home VoIP provider. It was basically landline equivalent -- yes, it was even better than my cell phone.
I was _shocked_. I remember PowWow, FreeSpeak, and all those other systems that ran VoIP over Modem lines. In what alternate universe did VoIP become a quality leader under difficult network conditions?
Turns out that implementation matters. I went and harassed some of the people who worked on the phone equipment (heh Brian) and asked how this system could possibly be working at all. Apparently Avaya got a bunch of the people from Bell Labs (it came from Lucent, which came from AT&T, which itself came from Ma Bell), so there was all this knowledge lying around already in how to manage reliable communications like lives depended on it. The big things being used were:
1) Error Concealment
2) Dynamic Jitter Buffers
Error concealment is simple -- there's necessarily 50 packets per second on a 20ms-latency link (1000ms / 50 packets per second = 20ms of audio per packet), and speech is massively redundant. So rather than simply dropping out when packets were missing, the voice client was "filling in the gaps" with neighboring content. Since the overall frequency profile was kept relatively consistent, short term drops were kept outside the range of human perception. Neat -- obvious, and not entirely unique to this particularly implementation (there's direct support for concealment in some of the G.72x codecs), but neat.
The dynamic jitter buffers are cooler. The basic idea here is that some links are high quality and others are less so, and sometimes the quality of the link will change in the middle of a call. As a response, the Avaya architecture will negotiate a longer buffer for packets to be stored before they're output to the listener to be heard. This buffer starts at ~10ms and can scale up to ~300ms -- distracting, but users have been accustomed to higher latency through their love of cell phones (sad, but true). The key is that the human auditory system can't easily detect speed changes at subsecond resolutions, so you simply execute a non-pitch-shifting slowdown of output speech over a second or two and now you've got a jitter buffer far more tolerant of inclement network conditions. Mind you, this is an absolute nightmare for automated testing equipment, which expects time to be constant, but it's great for everything else -- even TTY's! You'd think a 150bps modem could travel over any link, but apparently not...
Anyway, we keep hearing about how Motorola and Avaya are putting out some kind of VoIP phone, so I'm actually pretty hopeful that we'll see a GOOD VoIP/WiFi solution sometime in my lifetime. I can say this much, though -- simply spurting ulaw on the wire and calling it VoIP ain't my idea of a good time.
--Dan