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will a 768KB cable internet line be ok for VoIP?

A

amheck

Golden Member
Assuming the only thing using the 768KB line is the VoIP service (no router, just phone adapter hooked into the cable modem) will that speed be sufficient for the good phone quality?

How much speed/throughput does a VoIP connection usually take up?

Thanks!
Aaron
 
Should be just fine, I don't know about the specifics of the different VOIP technologies but a typical voice codec won't use more then 128kbit/s
 
interesting....I thought it was a bunch more. So what is it about wireless that makes VoIP a little flaky? Is it the non-reliability of the transmissions? I got the 768kb line cause I had read that VoIP is hit or miss over wireless, but I thought that was because it took up a lot of bandwidth.

When I did a speed test between my wireless PC and the new 768kb line, I was amazed at how much faster the wireless was.
 
VOIP depends also on the uplink. Your download might be 768 but if your upload is only 50 or 60kb, your VOIP will suffer. VOIP can be fine over wireless, it depends on the environment though, has to have a low latency, uninterrupted connection.
 
It depends what kind of wireless you're talking about. If you're talking about something like cellular broadband or Clearwire type service, then the reason VoIP does not work well is because of the extremely high latency. Most VoIP traffic is over what's called RTP, which is NOT a reliable protocol, meaning that VoIP itself expects some packet loss. However, what'll happen if your latency is high is that packets will not just be out of order but will also come in bursts which won't sound good.

If you're talking about over a wireless bridge, then VoIP's quality depends almost entirely on your operating environment. It can sound just fine...or it can sound like crap.

Most commercial VoIP services use a variant on the g.729 codec, which can be as low as 20 kbps for one-way audio. If they're using g.711, it'll be closer to 80 kbps one-way.
 
Thanks for the added info guys. Yeah, sorry, I was talking about wireless over an ethernet bridge. Well, I guess I have the dedicated line. I suppose I could get a wireless bridge, and see if it's aceptable. If not, then I always have the roadrunner lite. If it's ok, then I guess I can save the $15/month.

Would a DD-WRT based router be better for this sort of set up? I'm assuming you can do some sort of QOS and give priority to the VoIP? I have a Linksys WRT54GS now. Will have to check if that's one of the ones that can use the DD-WRT
 
DDWRT's QoS is only available for traffic going through it as a router, not for traffic going to or from its wireless network to or from its wired network. So, configured as a wireless bridge, no, you wouldn't get any QoS from DD-WRT unless you configured it as a bridge where the WLAN NATed to the wired switch, however, this would introduce double NAT which I can virtually guarantee will not work with VoIP.

I've used VoIP over a Cisco wireless bridge, and it worked fairly well. I haven't tried it over DDWRT.

My personal policy is that VoIP should be wired. Always. I do not endorse setting it up over wireless. In fact, I won't even use 802.11g wireless SIP phones. I make them get a cheap 900mhz analog cordless phone and then use an ATA.
 
A G711 conversation takes up 80Kbps, while a G729A conversation takes up 24Kbps (w/o L2 overhead).

As you can see, it's quite easy to cover the required bandwidth, assuming you only have single conversation at any given time.
The biggest concern w/ VoIP is latency & packet drops.

You could have a 20/20 Fios connection, and still have shitty voice calls.
Unfortunately you're at the mercy of the ISP, since usually there's no SLA of any kind for home connections.



 
Interesting phone. I looked at some of the Skype stuff, but didn't investigate too much, for some reason. I ended up with the dedicated $15/month cable connection (just for this VoIP, no data will be used over it) and then the $25 Vonage plan. I do wish I could have found something a little cheaper, as I'll really only ever use this phone a few days a week at most, but I guess I'm not tied into a contract with either one, so if I find something better, I can always switch.

Thanks for all of the info here guys. Interesting stuff.

On a side note, I did a little reading, took a big leap of faith, and upgraded my router with DD-WRT. Pretty neat. I dig it, although I will never used 98% of the features.
 
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