1. The Internet and Real-Time Applications Identifying Voice Transmission and Switching Issues for Packet Data Networks S. Wood Nov. 2006 Copyright 2006 Modern Systems Research

2. Voice Transmission Impairments Analog PCM Packet Copyright 2006 Modern Systems Research

3. Transmission Effects Copyright 2006 Modern Systems Research

4. Acceptability Rating & Mean Opinion Score Layer 8: The Human Bell SystemVoIP Copyright 2006 Modern Systems Research

5. Analog Transmission CableLoaded cable VF Repeatered Cable Copyright 2006 Modern Systems Research

6. Analog Transmission Improvements: –Loading coils –VF repeaters Impairments –Frequency response and loss change with cable length and gauge Copyright 2006 Modern Systems Research

7. Digital TDM Transmission With out echo cancellers With echo cancellers Copyright 2006 Modern Systems Research

8. Digital TDM Transmission Improvements –Echo cancellers Impairments –Codec design –bit errors –Synchronization –clock jitter –clock wander –frame slips Copyright 2006 Modern Systems Research

9. Digital Packet Transmission G729A codec (Coding used by most VoIP) Packetizes 30mS of audio Copyright 2006 Modern Systems Research

10. Digital Packet Transmission Improvements –Use extra high bandwidth –Use QOS Impairments –Packet loss comes from network congestion –Packet arrival time jitter causes increased jitter buffer length which add to latency time –Packet length packetization time 30mS –Increasing the number of hops increases packet arrival time jitter –Codec design issues Copyright 2006 Modern Systems Research