A question of voice quality

In traditional networks, voice quality hasn’t been a question for years. In spite of the famous “pin drop” ad campaigns, voice quality for circuit-based 64K bit/sec service is assumed to be quite good. But the quality for voice over IP remains an active issue, one that Steve addressed in a paper titled “Proactive Voice Quality Monitoring” and penned for Nortel.   The fundamental cause for concern about quality in VoIP is the impact of overall network traffic. If a traditional network runs out of bandwidth, the result is an “all circuits busy” signal. The quality of the call is of no concern because there is no call in the first place. But for a packet network the voice quality can change mid-call if the overall network traffic changes.

In traditional networks, voice quality hasn’t been a question for years. In spite of the famous “pin drop” ad campaigns, voice quality for circuit-based 64K bit/sec service is assumed to be quite good. But the quality for voice over IP remains an active issue, one that Steve addressed in a paper titled “Proactive Voice Quality Monitoring” and penned for Nortel. 

The fundamental cause for concern about quality in VoIP is the impact of overall network traffic. If a traditional network runs out of bandwidth, the result is an “all circuits busy” signal. The quality of the call is of no concern because there is no call in the first place. But for a packet network the voice quality can change mid-call if the overall network traffic changes.

The first step in monitoring voice quality is defining what can and cannot be measured. It’s reasonable to measure voice quality within the packet portion of a network. And that’s the portion of the network that’s subject to traffic-related impairments. But the digital network can’t measure the “true” quality based on the analog portion. If there’s a lot of background noise – or if you bought a phone for $3.99 on the discount table – you’re not dealing with a great signal in the first place. All you can guarantee is that the analog voice signal that’s received is reproduced faithfully on the far end.

The good news is that software/hardware combinations for monitoring voice quality are readily available. By looking at various parameters within the packet network, especially jitter, the actual quality can be monitored in an ongoing, non-invasive manner. And the availability of these tools could have an impact on the way voice services are bought and sold. We’ll address this next time.