Teachers Name : Suman Sarker Telecommunication Technology

Subject Name : Mobile & Wireless Communication-2Subject Code : 9471Semester :7th

Department : Telecommunication

Ideal Institute Of Science & Technology (IIST)

Lecture – 08Ch- 8

Voice over Internet Protocol

Topics to Discuss

• History of VoIP• VoIP—Early Adopters• VoIP—Standards and Standards Bodies• VoIP—Making Sense of the Protocols• “The Great Voice Myth”• VoIP—Protocol Challenges• Summary

Why Move to VoIP?

• Cost savings—toll bypass• Open standards—H.323, SIP, MGCP• Multi-vendor interoperability• Integrated IP voice and data networks

Defining the VoIP Protocols• H.323An ITU Recommendation that defines “Packet-based multimediacommunications systems”. H.323 defines a distributed architecture forcreating multimedia applications, including VoIP• SIPDefined as IETF RFC 2543. SIP defines a distributed architecture forcreating multimedia applications, including VoIP• MGCPDefined as IETF RFC 2705. MGCP defines a centralized architecture forcreating multimedia applications, including VoIP• H.248An ITU Recommendation that defines “Gateway Control Protocol”. H.248 isthe result of a joint-collaborate with the IETF. H.248 defines a centralizedarchitecture, and is also known as “Megaco”• MegacoDefined as IETF RFC 2885. Megaco defines a centralized architecture

What is VoIP? Voice over IP is a set of technologies that uses a high-speed network connection to send your voice as packets of information versus using an analog signal over a traditional phone line. 

WVU has chosen to implement a Voice over IP telephone system as a replacement to the legacy ISDN and SRX systems that were installed previously. The manufacturer of the system we are using is Cisco Systems (you may hear telecom employees refer to the VoIP phones as “Cisco Phones”). 

Voice over Internet Protocol (VoIP)

Voice Over Internet Protocol = TI devices available

Voice Over Internet Protocol

DTMF (Cont.)

• In TDM world, all voice traffic is sent asuncompressed 64Kbs PCM streams; anythingsent on that circuit is an untouched stream ofbits; (e.g., voice speech, modem tones, faxtones, and DTMF digits)• DSP codecs designed to interpret humanspeech, can distort DTMF tones (machine-tones)• High b/w codecs less likely to distort• Distortion causes problems with voicemail andIVR systems

Next Lecture

Logical channel frame and cellular telephone