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So before I start: Disclaimer: I sell VoIP, PBXs and adapters, etc. I also don't sell VoIP to save money - I sell it to increase flexibility. It is possible to save money on calls, but that's not my primary reason for it.
On Tue, 23 Dec 2008, Henry Bremridge wrote:
I am trying to move to VoIP and currently use Vonage, but am told by "the powers that be" that voice quality is not good enough.
Quality means a lot of things to a lot of people. It's one of the biggest headaches I have - almost as bad a hearing "my computer doesn't work" is "the phone sounds bad" ... Narrowing down the actual "quality" part of a connection is sometimes quite hard.
In terms of pure audio quality, (assuming no packet loss), if the device you are using (ATA, desk phone, soft phone, etc.) is using a G.711 CODEC then the quality of the call should not be discernible from the quality of a standard call placed over the BT network - because BT use G.711 CODEC inside their own digital network once the analogue call hits the exchange.
In many cases it should actually be better, as you don't have the analogue signal going over 50 year old copper wires to the exchange before the conversion to digital happens.
So what can go wrong, quality wise.Firstly the provider (or device) might be using a compressed CODEC. In simple terms there is G.711 which although compressed in one manner of speaking isn't "lossy", then there is everything else which is "lossy". (Compare PNG which is compressed but not lossy vs. JPG which is both compressed and lossy)
G.729 is popular, but there are others. GSM we're all familiar with as it's used on our mobile phones. G.726 is typically used between DECT handsets and their base-stations.
Transcoding degrades quality - like copying copies of VHS tapes, or continually edit/save/edit/save JPG images. DECT phones typically use G.726 between the handsets and base stations, so a DECT phone connected to an analogue adapter which when converts to VoIP can be quite "lossy" indeed: analogue -> G.726 -> analogue -> G.711 -> VoIP ...
Compression is often used on international links too - especially if the call is bridges to the PSTN at some point. That can really make things worse. One of my wholesale providers gives me the option of 2 different rates - one which they call their "gold" rates and that's using better routes for some calls (presumably lower/no compression). Costs more though.
The other issues you might get is echo. But that's another bag of wurms in it's own right )-:
Then there's the quality of the phone you're using. If a headset on a PC/Laptop, how good is it really? Do some local recordings and check. Sure, sound cards might be dolby zippity doo dah on the output side, but what's their input quality like?
And not all desk phones are created equal. Grandstreams, which I like, and sell a lot of are inferior, sound quality wise to Snoms. But Snoms are twice the price. ATL250s are better too, and half the price, but utterly useless as a phone. So you pay your money and takes the chances...
So the above is all quality at the audio end. If we're sorted that out, then we're left with Internet quality.
In this country, Packet loss is what we're up against. Latency isn't normally an issue, but jitter is (jitter is the variance between packet times - we can tolerate high latency, as long as the time between each packet is relatively similar)
So why do we get packet loss...Your ISP and what you're doing with your own broadband connection are the major contributors. Some ISPs do have internally congested networks, and some people use p2p downloads ... and expect everything else to just work...
Unless you pay for it, (and pay dearly!) all Internet access is contended. (Ye canny change the laws o' fizix!) The "trick" is to pick a system with the least contention for the best price.
Can anyone provide recommendations to improving voice quality?
The biggest single thing I've found is to use a GOOD ISP, and employ good working practices on your own network.
But what makes a good ISP? Pick 2 of these 3: Speed, Service, Price.I reckon there's a good number of ISPs in the middle-range - ones who still have a UK based call centre, not too small to have their own internal networks swamped, but not too big to not really care about customer service. You'll find a few, but for most home users, IME, you'll find them out of your price range. Which is why I deal with SMEs :)
So for example: If you're currently paying £15 a month for the ISP, but upgrade to a £23 a month ISP - wouldn't that £7 a month be better off being spend on BT to move yourself to option 3 rather than to a better ISP to then get free VoIP calls?
It's a real minefield in the residential area - much easier for SMEs to make that decision.
So if you're looking to using VoIP to reduce call charges, then investing in a good ISP, good routers, VoIP phones, headsets, etc. may well be counter productive in the money savings department.
Issues that I have seen / heard are the following - Implement QoS on the router - Upgrade the router - Change from Vonage to another provider - Change Internet Connection to a fixed line speed (rather than a variable max rating) - Make sure ISP does not limit VoIP - Get VoIP phone rather that relying on Vonage
Right now I'm not aware of any ISPs that limit VoIP. Some do "accidentally" by providing you with a router that might be locked into their own VoIP solution which won't allow VoIP on the inside. (BT...) and some routers break VoIP because they've got buggy software in them anyway.
QoS/Traffic shaping will only work on outgoing data.By the time incoming data has clocked its way over the wire into the device, it's too late to do anything about it. This is generally OK though because it's the outgoing data that's going to be the more problematic because our output speed here in the UK is typically 10 to 20 times slower than incoming. I've used Draytek and Zyxels with their traffic shaping/QoS in the past with good results, but when the network is managed in a business sense (ie. no streaming media, no p2p, no pron, etc.) then it's OK too.
No amount of QoS will protect you against a rubbish ISP or a determined teenager stealing music & videos. Ever had random slow downloads? Web pages only half loaded? Imagine that on a VoIP call... I know I keep going on about it, but getting a good ISP is 90% of the problem solved.
Some other information: A single VoIP call, using a G711 CODEC needs 80Kb/sec *each way* and 50 packets per second *each way* to work. A lot of people overlook the packets per second requirement, and the full duplex nature of voice communications plays havoc with Wi-Fi which is only a half-duplex solution, so don't use Wi-Fi and VoIP. (It can work and I have Wi-Fi VoIP handsets which do work, but I really don't recommend it)
And then it really depends on what you want out of VoIP. If you want cheap phone calls, then look into one of the standard BT packages. (seriously). Or use one of the prefix-diallers - eg. one of the Betamax resellers "18866", etc. (I think) Or use a cheap VoIP provider, but with a cheap ISP, be prepared for call quality issues, but maybe you can put up with that for cheap or even free calls? Your choice...
Right now, I think it's hard for your average home user to benefit from VoIP - unless they're really keen and prepared to spend their own time in testing, experimenting, etc. but if you've got the time, there are free VoIP carriers and free calls to be made out there! I don't use these services for my business customers because they've got no backup, but for home use, where you're not depending on it, they're OK.
I think I've witterd on enough now :) I'll bring some kit/toys along with me to Paignton... Wonder if we can get a wired connection to their network..
Cheers, Gordon
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