Asterisk VoIP Voice Quality

A lot of different things can cause voice quality issues. When using SIP a variety of things could be to blame, and not at all easy to track down.

Causes of poor sip voice quality can be one of the following :

• 1. VoIP to Analogue convertor

  A loss of signal always occurs when you jump between analogue and digital signals. Some convertors are better than this than others, some include echo canceling, some don’t.
  Symptoms of this problem are echos in conversations, delays when speaking, low volume, people can’t hear you. You can occasionally get echos in conversations from upstream Analogue to VoIP conversion as well.

  Using VoIP equipment through the entire network can resolve this issue.

• 2. PABX not playing nice with VoIP to Analogue conventor.
  

  Symptoms of low volume, calls not connecting, or answering. Weird timing issues can exist.

• 3. Physical phones.
  

  Some phones don’t like the conversion process or voip. Radio portal phones can also be problematic. Some voip phones are faulty and cause poor phone quality. To test see if using a softphone has the same issue.

• 4. Codec mismatches between provider / PABX / Phones or codec conversion issues.

  In jumping between G729, G711, alaw or a variety of other codecs some voice quality loss can occur. Using same codec everyhere resolves this issue. In high use situations you can get go silent, or calls lagging, delays.

• 5. Over used internet connection.

  Symptoms are poor ping times (60+ms to sip provider), packet loss, and calls that go silent for seconds at a time indicates this is a problem.

  A second internet connection line can fix this. If your internet line is used heavily consider a second line. Using G729 codec on your phone system also reduces issues over poor quality internet connections.

• 6. Sip Provider overloaded or too far away

  Poor quality can occur upstream.
  Some ways to narrow voip quality issues down is :

  • a. Plug in half a dozen voip phones into the network, connect them to the sip provider directly.
    Test to see if they get same poor quality or not when making calls while using network heavily at the same time. This will narrow down the fault to a networking or phones issues.
  
  
  • b. Check if quality varies in time, if number of analogue lines in use or internet use effects call quality. Is there any call issues with quality on the weekend/after hours or only during normal day usuage.
  
  
  • c. Check codecs are consistent across network
  
  
  • d. Try different codecs to see if it improves quality.
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