Trends Price of Phone Calls NY — London

Trends: Price of Phone Calls: NY - London

Internet

Speech Coders Waveform Coders Time Domain: PCM, ADPCM Frequency Domain: e. g. Sub-band coder, Adaptive transform coder Source Coders Linear Predictive Coder Vocoder

Speech Coders Waveform Coders Time Domain: PCM, ADPCM Frequency Domain: e. g. Sub-band coder, Adaptive transform coder Source Coders Linear Predictive Coder Vocoder

Example: GSM Digital Speech Coding

Typical User. Agent Protocol stack for Internet Terminal Control/Devices Q. 931 H. 245 RAS RTCP TPKT TCP Terminal Control/Devices Codecs UDP RTP Codecs SIP SDP RTCP

IP SIP Phones and Adaptors

ecse. rpi. edu

PBX PSTN External T 1/CAS Internal T 1/CAS (Ext: 7130 -7139) Gateway Ethernet Regular phone (internal) sipc Bob’s phone sipd 7134 => bob

PBX PSTN External T 1/CAS Gateway (10. 0. 2. 3) Internal T 1/CAS Ethernet 5551212 Regular phone (internal, 7054) Bob calls 5551212 sipc sipd Use sip: 85551212@10. 0. 2. 3

Dial 853 -8119 Phone is ringing Disconnect Bob can listen to his voice mails by dialing some number.

Bob phone 1. office. com Alice vm. office. com

Bob phone 1. office. com; CANCEL 200 OK Alice 200 OK RTP/RTCP v-mail vm. office. com; SETUP rtspd

Q. 931 SETUP Q. 931 CONNECT Terminal Capabilities Open Logical Channel Destination address (Bob@office. com) INVITE 200 OK Media capabilities (audio/video) Media transport address (RTP/RTCP receive) ACK