TRƯỜNG ĐẠI HỌC ĐIỆN LỰC KHOA ĐIỆN TỬ - VIỄN THÔNG TỔNG ĐÀI & KỸ THUẬT CHUYỂN MẠCH Chương 1: Lý thuyết tổng quan và sơ V Truyền thoại sơ hạ tầng viễn thông Giảng viên: Phan Thị Thanh Ngọc EPU - 2012 Nợi dung • Cơ sơ hạ tầng viễn thông truyền các loại dữ liệu sau: – Voice – DTMF signals » over ISDN » over ISDN + GSTN » over GSM + ISDN/GSTN – Data » over ISDN » over ISDN + GSTN » over GSM + ISDN/GSTN J.Tiberghien - VUB TIN HIÊU DTMF  Quay sô kiêu tone (Tone dialing) * # 1477 Hz 1336 Hz 1209 Hz 697 Hz 770 Hz 852 Hz 941 Hz * # In - band signaling : audio tones J.Tiberghien - VUB DTMF over the GSTN PSTN Voice interface Signaling Prerecorded voice messages Numerical answers J.Tiberghien - VUB DTMF over the ISDN ISDN Voice interface Signaling via D channel Prerecorded voice messages (B) Numerical answers (B) Ad-hoc digital DTMF generator required in ISDN phones J.Tiberghien - VUB GSM : Main  Characteristics • Digital telephony – Special vocoder (A/D converter) in telephone set » Data rate = 13 Kb/s » Not compatible with standard telephony codec » High error rate (10-3) – Separate digital signaling channel » Calling party identification » Other goodies similar to Belgacom’s “Comfort” services J.Tiberghien - VUB DTMF over the GSM PSTN ISDN GSM Voice interface DTMF Signaling Prerecorded voice messages (B) Numerical answers DTMF Numerical answers send to DTMF generator as short messages J.Tiberghien - VUB Data over the  ISDN 64 Kb/s 1920 Kb/s ISDN Rate Adapter : appears to the user as a synchronous modem, the clock being generated in the network n * 64 Kb/s possible but some timing problems need to be solved in the RA's (# delays over # channels !) J.Tiberghien - VUB IP over  ISDN • Usage : – Temporary interconnections – Back-up for leased lines – Additional capacity for overloaded leased lines • Main problem : IP: Connectionless >< ISDN : Connection oriented • Solutions : – One call per datagram (fast connection) – Keep connection for entire billing units J.Tiberghien - VUB Data over ISDN and the  GSTN ISDN m PSTN m PSTN m V110 ISDN ISDN 10 m PSTN m m J.Tiberghien - VUB Data Modem Control  V110 for  ISDN Async/ sync M U X ISDN 64 kb/s Sampling Data carried in 80 bit frames at 16 Kb/s 48 bit for data (=9600 b/s) 32 bit for synchronization modem signals clock adjustment real data rate 11 J.Tiberghien - VUB Hybrid ISDN/PSTN  modems • Today's residential Internet access problem: – Residential users » most use analog lines (data rate