Complete Telecom Fundamentals, The PSTN Telephone Network and IP Networks for Telecom Engineers first: PCM (64 kbit/s, A-law/μ-law), the DTMF matrix, Ethernet/IP/UDP headers, NAT, firewalls, QoS (DSCP EF) and Wireshark are used here without repeating the explanation.
One topic, one lesson: interactive slides, animations and packet diagrams, exercises with answer checking, and study notes in three languages (az, ru, en). Each lesson has a worked example, a “What can go wrong and how to find it” section, practice and a self-check. Hands-on labs run on Docker testbeds generating and analyzing live RTP streams with GStreamer, ffmpeg, sox, tc netem and Wireshark.
Course outline
01
How voice travels over IP
- end-to-end chain from microphone to packets
- packetization (10/20/30 ms)
- delay budget (ITU-T G.114)
- static and adaptive jitter buffers, packet loss and PLC
02
Codecs
- G.711 (A-law and μ-law)
- G.729, G.722, AMR (RFC 4867 and CMR)
- AMR-WB, EVS, Opus, H.264/H.265
- VAD/CNG/DTX (RFC 3389)
- transcoding, bandwidth and capacity planning, GStreamer/ffmpeg/sox
03
RTP and RTCP
- RTP header, payload types (PT)
- sequence number, timestamp and SSRC
- RTCP (SR, RR, XR) and rtcp-mux
- symmetric RTP (latching)
- media relaying, timeouts and RTP analysis in Wireshark
04
DTMF in VoIP
- in-band DTMF and distortion in compressed codecs
- RFC 4733 (telephone-event) format and packet sequence
- duplicate and lost digits
05
Voice quality
- quality factors, MOS and the R-factor (E-model, G.107)
- PESQ and POLQA, KPI thresholds
- echo cancellation (G.168)
- one-way and robotic audio, quality monitoring
06
Media security, fax and modems
- SRTP (RFC 3711) encryption and authentication
- Fax over IP (G.711 pass-through and T.38 IFP/UDPTL)
- ECM timing and modems over IP
07
Problems and solutions
- 21 cases, from one-way audio behind NAT and firewalls to jitter
- loss, echo, VAD clipping
- duplicate DTMF digits and T.38 fax drops
08
Project
- a VoIP network media plan — codec selection
- bandwidth calculation, QoS
- DTMF, fax, quality metrics and a troubleshooting checklist
The sixth course of the 14-course Telecom track, from the telephone line to 5G.