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TRƯỜNG ĐẠI HỌC ĐIỆN LỰC KHOA ĐIỆN TỬ - VIỄN THÔNG TỔNG ĐÀI & KỸ THUẬT CHUYỂN MẠCH Chương 1: Lý thuyết tổng quan sở III Ghép kênh trung kế - Mạng trung kế Giảng viên: Phan Thị Thanh Ngọc EPU - 2012 Mạng điện thoại Analog / Digital ABX ABX ABX ABX ABX ABX PABX PABX ABX J.Tiberghien - VUB Mang điện thoại Analog / Digital ABX ABX ABX ABX ABX ABX PABX PABX ABX J.Tiberghien - VUB Ghép kênh miền tần số sin( t) X sin( t) cos(( t cos(( t + ~ ~/ cos(( t kHz Ch0 Ch1 Ch2 Ch3 Ch4 frequency J.Tiberghien - VUB Ghép kênh miền tần số 420kHz 62kHz X Group X Supergroup 106kHz 12 X 612kHz X 16 supergroups are multiplexed into one 960 channels trunk line J.Tiberghien - VUB Mạng điện thoại Analog / Digital ABX ABX ABX ABX ABX ABX PABX PABX ABX J.Tiberghien - VUB Ghép kênh miền thời gian 0 1 1 0 1 Synchronous ! J.Tiberghien - VUB Biến đổi A -> D Codec 64 (or 56) Kb/s 11 3400 Hz 300 Hz Linear 12 A or law 11 or 12 bit logarithmic A to D encoder Converter 8000 Hz 8 P to S or 64 kHz J.Tiberghien - VUB Biến đổi D -> A P to S A or law logarithmic decoder 11 or 12 Codec Linear 11or12 bit D to A Converter 64 Kb/s 64 kHz Clock extraction J.Tiberghien - VUB Hệ thống Bell D2 (CCITT G733) 23 24 1 frame = 193 bit (= 24 * + 1) 125 S = / 8000 24 193 bit = * 24 + 1544 kHz = 193 / 125.10-6 least significant bit stolen once every frames Signaling rate : 1.3 kb/s = 8000 / Frame synchronization by bit Frame duration : Number of channels : Frame length : Bit frequency : Signaling : 10 J.Tiberghien - VUB Kiến trúc Plesiochronous Bit rates in kb/s N.America 64 1544 6312 44736 139264 Europe 64 2048 8448 34368 139264 Japan 64 1544 6312 32064 97728 Trans-Atl 64 2048 6312 44736 139264 Levels and : Strictly synchronous Levels 2, and : plesiochronous 29 J.Tiberghien - VUB CCITT level Data rate = 8448 Mb/s, Frame = 848 bits, T ~ 100 S Four 2048 kb/s are multiplexed (bit interleaving) Frames not related to frames of multiplexed channels A multiplexed frame contains 205 or 206 bits from each of the multiplexed channels Minimal channel data rate = Maximal channel data rate = 2042 kb/s 2052 kb/s The stuffing control bits are transmitted times 30 J.Tiberghien - VUB CCITT level 200 data bits 1111010000XR 208 data bits CCCC CCCC 208 data bits 204 data bits CCCCSSSS 212 data bits 31 J.Tiberghien - VUB Elastic Store for removing clock jitter Write Clock FIFO Buffer Storage level Read Clock low pass 32 J.Tiberghien - VUB Level Multiplexer E.S E.S E.S Framing + bit-stuffing E.S 33 J.Tiberghien - VUB Level Demultiplexer E.S E.S Framing + bit-stuffing 34 E.S E.S J.Tiberghien - VUB Kiến trúc đồng số • Problems with PDH – Each multiplexed section has its own clock – Each level of multiplexing has its own clock – Frame structure from multiplexed signals is not explicitly present in the multiplexed stream > Full demultiplexing required at each node ! 35 J.Tiberghien - VUB Kiến trúc đồng số • Synchronous trunk network – Common clock or synchronized clocks • Design principles – Based upon 125 S frames – Each frame caries payload and section overhead – The payload itself is a set of Virtual Containers – Virtual containers carry overhead and payload – At the lowest level of this recursive structure, the payload contains standard CEPT 2048 kb/s frames • Compatibility, at the higher levels, with the North American synchronous hierarchy, SONET 36 J.Tiberghien - VUB Kiến trúc đồng số SDH - SONET Data rate 51.84 155.52 466.56 622.08 933.12 1244.16 1866.24 2488.32 37 CCITT STM-1 STM-3 STM-4 STM-6 STM-8 STM-12 STM-16 USA-Elec STS-1 STS-3 STS-9 STS-12 STS-18 STS-24 STS-36 STS-48 USA-Opt OC-1 OC-3 OC-9 OC-12 OC-18 OC-24 OC-36 OC-48 J.Tiberghien - VUB STM-N 125S N*2430 bytes/frame N*9 b 38 N*261 bytes Each individual byte represents a synchronous 64 kb/s data flow J.Tiberghien - VUB STM-1 (155.52 Mb/s serial signal) 125S 39 Section overhead STM-1 virtual container (VC4) 261 J.Tiberghien - VUB STM-1 Virtual Container VC4 9*4 bytes tributary 9*4 bytes tributary 9*4 bytes tributary 9*4 bytes tributary Section overhead Path Overhead (155.52 Mb/s serial signal) 63*4 Each tributary = One CEPT 2048 b/s frame + overhead A VC4 can carry 63 * 30 = 1890 telephone circuits 40 J.Tiberghien - VUB Ghép kênh SDH Add-Drop STM-1 STM-1 Up to 63 Mb/s channels 41 J.Tiberghien - VUB Các vòng SDH 34 Mb/s 42 Mb/s J.Tiberghien - VUB Đồng khung SDH 43 J.Tiberghien - VUB ... Plesiochronous Bit rates in kb/s N.America 64 15 44 6 31 2 44 736 13 9264 Europe 64 2048 8448 34 368 13 9264 Japan 64 15 44 6 31 2 32 064 97728 Trans-Atl 64 2048 6 31 2 44 736 13 9264 Levels and : Strictly synchronous... Common 17 Bell D2 G 733 30 0 -34 00 Hz 8000 Hz (17 % are 7) 24 24 ( 23) 15 44 kb/s CEPT 30 G 732 30 0 -34 00 Hz 8000 Hz 32 30 2048 kb/s A 1. 3 kb/s (24) kb/s kb/s + 64 kb/s J.Tiberghien - VUB Ghép kênh đồng... decoder 11 or 12 Codec Linear 11 or12 bit D to A Converter 64 Kb/s 64 kHz Clock extraction J.Tiberghien - VUB Hệ thống Bell D2 (CCITT G 733 ) 23 24 1 frame = 19 3 bit (= 24 * + 1) 12 5 S = / 8000 24 19 3
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