Điện tử viễn thông c1 4 điện thoại số và truy nhập số khotailieu

TRƯỜNG ĐẠI HỌC ĐIỆN LỰC KHOA ĐIỆN TỬ - VIỄN THÔNG TỔNG ĐÀI & KỸ THUẬT CHUYỂN MẠCH Chương 1: Lý thuyết tổng quan và sơ IV Điện thoại số và truy nhập số mạng VT Giảng viên: Phan Thị Thanh Ngọc EPU - 2012 Nội dung • • • • ISDN DECT GSM TETRA J.Tiberghien - VUB The Telephone Analog / Digital Network ABX ABX ABX ABX ABX ABX PABX PABX ABX J.Tiberghien - VUB ISDN Đặc tính chính • Communication channels : – B = 64 kb/s data channel – D = 16 or 64 kb/s signaling channel • Data rates : – Basic Access : 144 kb/s = 2B+D(16) – Primary Rate Access : 2048 kb/s = 30 B + D(64) • Standard services – # simultaneous communications = # B channels – Calling line identification J.Tiberghien - VUB The Telephone Network ISDN Basic Access A/D converter in phone Digital switch S bus 144Kb/s twisted pair, average length 2.5 Km modem * 64 Kb/s + 16 Kb/s 144Kb/s modem J.Tiberghien - VUB ISD N Sbus NT2 T NT1 Terminal Adapter Analog Terminal Adapter V24 Terminal Adapter Fax Gr U J.Tiberghien - VUB Belgacom TWIN S bus available for extensions 192 Kb/s Up to terminals Terminal Adapter Terminal Adapter Network Terminator U interface NT12ab J.Tiberghien - VUB The Telephone Calling Line Identification Protocol Network ABX ABX ABX ABX ABX ABX PABX PABX ABX J.Tiberghien - VUB The Telephone Cordless Telephones Network ABX ABX ABX ABX ABX ABX PABX PABX ABX J.Tiberghien - VUB Digital Cellular Radio Systems Name Freq.(MHz) CT2 DECT GSM 864-868 1880-1890 890-915 935-960 10 # can.rad 40 10 124 P.max.(W) 0.01 0.25 r.max.(Km) 0.2 0.15 30 datarate (Kb/s) 32 32 13 J.Tiberghien - VUB Reuse of Frequencies Pr/sa = Pt/r2 r transmitter 15 J.Tiberghien - VUB Cellular Radio 16 J.Tiberghien - VUB Cellular k = number available frequencies per cell Radio S = Area of a cell = Π *r2 n = Number of simultaneous calls per km2 pt = Power of transmitter P0/Sa= Minimal field strenght at receiver input n =k/S pt = p0/Sa * r2 17 With smaller cells, - more antenna sites are needed - more simultaneous calls are possible - transmitted power can be reduced J.Tiberghien - VUB Flanders Cellular Radio Ardennes in practice 18 J.Tiberghien - VUB Cellular Radio 19 J.Tiberghien - VUB GSM System Architecture BSS R A D I O NSS 16Kb/s GSTN TRAU 64Kb/s MSC ISDN BSC VLR SS7 BTS HLR NSS MS 20 BSS : Base Station Sub-system BSC : Base Station Controller BTS : Base Transceiver Station TRAU : Transcoder / Rate Adapter Unit NSS : Network and Switching Sub-system MSC: Mobile service Switching Center HLR : Home Location Register VLR : Visitors Location Register J.Tiberghien - VUB GSM • MS : Mobileacronyms Station – ME : Mobile Equipment – SIM : Subscriber Identity Module • BSS : Base Station Sub-system – BSC : Base Station Controller – BTS : Base Transceiver Station – TRAU : Transcoder / Rate Adapter Unit • NSS : Network and Switching Sub-system – MSC: Mobile service Switching Center – HLR : Home Location Register – VLR : Visitors Location Register 21 J.Tiberghien - VUB Mobilit • Location Management : y options – Ubiquitous paging : » call made in all cells » No need to know where MS is » Waste of radio capacity – Systematic location updating » call made in the single cell where MS is » Overload of NSS – Location Area » call made in a group of adjacent cells » location information transmitted only when leaving the area 22 J.Tiberghien - VUB GSM Radio Transmission • Two transmission modes – Idle Mode - via a "common channel" » MS lists to paging messages » Monitors radio environment to select base station » Sends and receives short messages – Dedicated Mode - via a "Traffic Channel" 23 » A TCH (13 kb/s full duplex) is assigned to a specific call for voice/data transmission » A "Slow Associated Control Channel" is used for radio measurements » For "Fast associated signaling" (needed for handover), capacity is stolen from the TCH J.Tiberghien - VUB GSM security MS VLR i:K i HLR Ki imsi rand sres data & signalling enciphered by Kc 24 vlr,imsi sres = A3(Ki,rand) rand,sres, Kc Kc = A8(Ki,rand) J.Tiberghien - VUB GSM Voice Transmission Layers Analog 13 Kb/s 64 Kb/s 25 J.Tiberghien - VUB GSM Radio Slots frequency Tx 200 KHz 45 MHz Rx 15/26 ms 26 time J.Tiberghien - VUB Wireless Interference Margins Cause considerable loss in transmission capacity Frequency • Considerable room for improvements by controlling interferences Time – Signal hardening – Signal recovery – Signal expansion Space 27 = Next generation mobile networks (UMTS) J.Tiberghien - VUB Multi-path Interference Different paths have different lengths and different delays 28 2nd generation (GSM) : interference = noise 3rd generation (UMTS) : add similar input signals with appropriate delays so that they reinforce each J.Tiberghien - VUB other Other Cellular • GSM & UMTS Protocols offer a mobile to fixed service • Some professional users communities need – Broadcast – Group communications – Mobile to mobile communications – Precise mobile localization • TErestrial Trunked Radio is the answer ! – Used by police & emergency services in » Belgium » The Netherlands » Germany 29 J.Tiberghien - VUB ... channels : – B = 64 kb/s data channel – D = 16 or 64 kb/s signaling channel • Data rates : – Basic Access : 144 kb/s = 2B+D(16) – Primary Rate Access : 2 048 kb/s = 30 B + D( 64) • Standard services... switch S bus 144 Kb/s twisted pair, average length 2.5 Km modem * 64 Kb/s + 16 Kb/s 144 Kb/s modem J.Tiberghien - VUB ISD N Sbus NT2 T NT1 Terminal Adapter Analog Terminal Adapter V 24 Terminal Adapter... J.Tiberghien - VUB Digital Cellular Radio Systems Name Freq.(MHz) CT2 DECT GSM 8 64- 868 1880-1890 890-915 935-960 10 # can.rad 40 10 1 24 P.max.(W) 0.01 0.25 r.max.(Km) 0.2 0.15 30 datarate (Kb/s) 32 32 13