VoIP Voice and Fax Signal Processing

20.4 VoIP VOICE QUALITY SUMMARY

VoIP can closely match PSTN quality when taking care of the several improvements listed in the previous sections. A short critical items list is given below:

• Use of G.711 compression
• Low end-to-end delay with no or negligible packet drops
• Improved echo cancellers
• Front-end interfaces, and end-to-end signal transmission meeting, local country requirements

VoIP will achieve an extra benefit because of

• Short loops at the user telephone.
• Global portable numbers—able to keep the same number globally and able to interface directly with digital phones, Bluetooth, digital enhanced cordless telecommunications (DECT), and wireless fidelity (WiFi) phones.
• Continuous voice quality monitoring.
• VoIP G.711 calls can deliver much higher quality than G.726-based overloaded PSTN channels with DCME.

In addition to the above benefits of VoIP, VoIP quality can be made to exceed PSTN quality because of

• Use of wideband codecs to create more natural and comfortable conversation
• Automatic level control to deliver required signal levels
• Elimination of the background disturbances in voice algorithms
• The benefit of short loop lengths at the gateway
• Ability to minimize number of transcoding stages while communicating with different communication links