Data Communication, NUML-Islamabad Chapter 5. Multiplexing Data Communication, NUML-Islamabad

Definition of Multiplexing Transmission of information (either voice or data) from more than one source to more than one destination on the same transmission medium (facility).” Or multiplexing is sending of number of separate signals together, over the same cable or bearer, simultaneously and without interference. TYPES: 1) frequency division multiplexing (FDM) 2) time division multiplexing (TDM). Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad Audio Channel 4-kHz Bandwidth Data Communication, NUML-Islamabad

5.2 Frequency-Division Multiplexing SUBCARRIERS: First modulating messages onto several subcarriers and forming a composite baseband signal that consists of the sum of these modulated subcarriers, and MAIN CARRIER: This composite signal may then be modulated onto the main carrier. FREQUENCY ALLOCATION: In FDM, each channel of system is assigned a discrete portion of transmitted frequency. Thus many narrow bandwidth channels can be accommodated by a single wide bandwidth transmission system. Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad 5.2.1 FDM Hierarchy BASIC GROUP: 12-Channels- 60 to 108 kHz. fc 0 4 f 1 104 108 112 0 4 f 108-4n 112-4n 116-4n n 100 104 112 2 100 104 104 108 0 4 f 60 64 68 12 60 64 Basic Group Voice circuit G1 (60-108 kHz) 11 10 9 8 7 6 4 3 60 108 frequency (kHz) Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad 60-Channel Supergroup 60 108 1 420 480 528 360 312 2 468 576 408 fc 3 516 624 456 4 564 672 504 5 612 720 552 312 360 408 456 504 f kHz G1 G2 G3 G4 G5 Super Group SG (312-552 kHz) Combining 5 groups of 12 ch into 60-ch supergroup Frequency range: 312 to 552 kHz Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad 960-Channel Mastergroup 1116 1364 1612 1860 2108 2356 2604 2852 3100 3348 SUPERGROUP CARIER FREQUENCIES 4340 4092 3844 3596 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 60 300 564 804 1060 1300 1556 1796 2052 2292 2548 2788 3044 3284 3540 3780 f ( kHz) 312 552 812 1052 1308 1548 1804 2044 2300 2540 2796 3036 3292 3532 3788 4028 SG1 SG2 SG3 SG16 MASTER-GROUP 60-4028 kHz Figure 5.2.1-3 16-supergroups assembly for 960 telephony channels Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad FDM Hierarchy Basic Group (12 ch) Voice circuit 1 2 12 G1 G2 G3 G4 G5 Supergroup SG1 SG2 SG3 SG16 Mastergroup 960 ch 12 ch/group (12 ch/group X 5 groups = 60 ch) (60 ch/SG X 16 SG = 960 ch) Figure 5.2.1-4 960-channels long-haul FDM hierarchy Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad FDM Bandwidths Type of baseband Bandwidth _________ Voice 3.4 kHz Audio channel 4 kHz Video 4 MHz Television channel 6 MHz Multiplexed voice: 12 channels 48 kHz 24 channels 96 kHz 36 channels 144 kHz 60 channels 240 kHz 120 channels 480 kHz 240 channels 960 kHz 300 channels 1.2 MHz 600 channels 2.4 MHz 900 channels 3.6 MHz 960 channels 3.84 MHz 1,200 channels 4.80 MHz 1,260 channels 5.04 MHz 1,800 channels 7.20 MHz 2,700 channels 10.8 MHz Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad RF Carriers Radio channels: 4GHz, 6GHz 1 2 N Number of multiplexed channels: Maximum up to 2700 telephone channels or television signal. RX TX Figure 5.2.1-5 Multiplexed channels for RF propagation Data Communication, NUML-Islamabad

5.3 Time-Division Multiplexing Definition: TDM is time interleaving of samples from several sources so that information from these sources can be transmitted serially over a single communication channel. Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad Pulse Insertion f1(t) T (a) One PAM signal f2(t) TX (c) Two PAM signals (a) Second PAM signal Tx :Time spacing between adjacent samples Tx= T/n n: number of input signals Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad Example Ch3 Ch4 Ch5 Ch6 Ch2 Ch1 t Multiplexed PAM waveform 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad Digital Multiplexing Forming High-Bit-Rate Signal: Several low-bit-rate signals can be multiplexed, or combined, to form one high-bit-rate signal to be transmitted over a high-frequency medium. Diverse Nature Signals: Signals from various incoming channels may be of such diverse nature as a digitized voice signal (PCM), computer output, telemetry data, a digital facsimile, and so on. Data Communication, NUML-Islamabad

Digital Multiplexing Techniques 1) BIT-BY-BIT Basis: Known as bit or digit interleaving 2) WORD-BY-WORD Basis: Known as byte or word interleaving). Figure 5.4-1 Digital multiplexing Data Communication, NUML-Islamabad

5.5 PCM Hierarchies – E1 System CAPACITY: No. of Time Slots: 32 1) No. of digital telephone channels: 30 of 64 kbit/s 2) plus one for synchronization/transmission of alarms 3) and other one for signalling. TRANSMISSION RATE: 32channels x 8bit/channel/125 µs =2.048 Mbit/s (32 TS x 64 kbps = 2.0248 Mbit/s) USAGE:E1 circuits are used to connect medium and large companies. E3 lines are used between exchanges countries, and have transmission speed of 34.368 Mbit/s. Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad T1 System Multiplexes 24 digital telephone channels of 64 kbit/s into a 1.544 Mbit/s (= 64 kbps x 24 channels). Aggregate Transmission Rate: (24channels x 8bit/channel + 1bit) / 125 µs = 1.544 Mbit/s Data Communication, NUML-Islamabad

PCM Frame Structure – E1 Format 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Time slot F 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 S 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Channel no. Figure 5.5-1 2.048 Mbps frame structure – E1 1 2 3 4 5 6 7 8 Bit no. 64 kbps Data Communication, NUML-Islamabad

PCM Hierarchy Data Rates Channels Ist Order MUX (30x1=30ch) 1 2 30 2nd Order (30X4=120 ch) 3 4 3rd Order (120x4=480 ch) 4th Order (480x4=1920 ch) 2.048 Mb/s 8.448 Mb/s 34.368 Mb/s 139.268 Mb/s Figure 5.5.1-2 PCM hierarchies (a) E-hierarchy levels (b) T-hierarchy levels (c) E-System multiplexing hierarchy levels showing data rates Data Communication, NUML-Islamabad

Data Communication, NUML-Islamabad 2048k (30 Ch)* 8448k (120 Ch) x4 34 386k (480 Ch) 139 268k (1920) Ch 564 264k (7680) Ch Europe　（CEPT） 1544k (24 Ch) 6312k (96 Ch) x5 32 064k 97 728k (1440 Ch) x3 397200k (5760 Ch) Japan x7 44 736k (672 Ch) North America Data Communication, NUML-Islamabad