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MULTIPLEXING DAN MEDIA TRANSMISI Anhar, MT
MULTIPLEXING DAN MEDIA TRANSMISIAnhar, MT
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OUTLINE
Pengantar FDM TDM WDM
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TIU
Dpt menjelaskan proses multiplexing analog dan digital serta pengembangan teknologinya
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PENGANTAR
Mengapa multiplexing??? Keterbatasan bandwidth Melahirkan teknik efisiensi kanal
Apa multiplexing
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JENIS MULTIPLEXING
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FDM Useful bandwidth of medium exceeds required bandwidth
of channel Each signal is modulated to a different carrier frequency Carrier frequencies separated so signals do not overlap
(guard bands) e.g. broadcast radio Channel allocated even if no data
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DIAGRAM FDM
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FDM PROSES
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FDM OF THREE VOICE BAND SIGNALS
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CONTOH 1 Asumsikan bhw sebuah channel suara menduduki bandwidth 4
KHz. Kita perlu utk menggabungkan tiga channels suara kedlm sebuah link dng bandwidth 12 KHz, dr 20 hingga 32 KHz. Tunjukkan susunannya dng menggunakan FDM tanpa menggunakan guard bands.
Modulasikan masing2 tiga channels suara utk bandwidth yg berbeda-beda, spt pd slide berikut.
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PENYELESAIAN :
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SISTEM MULTIPLEXING ANALOG
AT&T (USA) Hierarchy of FDM schemes Group
12 voice channels (4kHz each) = 48kHz Range 60kHz to 108kHz
Supergroup 60 channel FDM of 5 group signals on carriers between
420kHz and 612 kHz Mastergroup
10 supergroups
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SISTEM MULTIPLEXING ANALOG
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SYNCRONOUS TDM
Data rate of medium exceeds data rate of digital signal to be transmitted
Multiple digital signals interleaved in time May be at bit level of blocks Time slots preassigned to sources and fixed Time slots allocated even if no data Time slots do not have to be evenly
distributed amongst sources
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Time Slots dan FramesMasing2 terminal/host memberikan “sebagian” dr time (time slot)Dlm TDM, sebuah frame terdiri dr satu siklus lengkap dr time slots, dimana satu slot didedikasikan ke masing2 pengirim.
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SISTEM TDM
TDM FRAMES Pure TDM: mux-to-mux speed = penjumlahan terminal speeds No loss of data (similar to voice call multiplexing)
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TDM LINK CONTROL
No headers and tailers Data link control protocols not needed Flow control
Data rate of multiplexed line is fixed If one channel receiver can not receive data, the
others must carry on The corresponding source must be quenched This leaves empty slots
Error control Errors are detected and handled by individual
channel systems
DATA LINK CONTROL ON TDM
FRAMING
No flag or SYNC characters bracketing TDM frames
Must provide synchronizing mechanism Added digit framing
One control bit added to each TDM frame Looks like another channel - “control channel”
Identifiable bit pattern used on control channel e.g. alternating 01010101…unlikely on a data
channel Can compare incoming bit patterns on each
channel with sync pattern
PULSE STUFFING
Problem - Synchronizing data sources Clocks in different sources drifting Data rates from different sources not related
by simple rational number Solution - Pulse Stuffing
Outgoing data rate (excluding framing bits) higher than sum of incoming rates
Stuff extra dummy bits or pulses into each incoming signal until it matches local clock
Stuffed pulses inserted at fixed locations in frame and removed at demultiplexer
TDM OF ANALOG AND DIGITAL SOURCES
DIGITAL CARRIER SYSTEMS
Hierarchy of TDM USA/Canada/Japan use one system ITU-T use a similar (but different) system US system based on DS-1 format Multiplexes 24 channels Each frame has 8 bits per channel plus one
framing bit 193 bits per frame
DIGITAL CARRIER SYSTEMS (2)
For voice each channel contains one word of digitized data (PCM, 8000 samples per sec) Data rate 8000x193 = 1.544Mbps Five out of six frames have 8 bit PCM samples Sixth frame is 7 bit PCM word plus signaling bit Signaling bits form stream for each channel
containing control and routing info Same format for digital data
23 channels of data 7 bits per frame plus indicator bit for data or systems
control 24th channel is sync
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DCS
Hirarki sinyal digital utk layanan telepon yg menggunakan multiplexing digital..
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T LINES
DS : nama layanannya sementara T : nama saluran yg dipakai utk layanan tsb
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T-1 FRAME
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E LINES
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contoh 1
Empat koneksi 1-Kbps dimultiplexing bersama-sama. Satu unitnya 1 bit. Tentukan (1) durasi 1 bit sebelum dimultiplexing, (2) transmission rate dr link, (3) durasi dr time slot, and (4) durasi dr frame?
Penyelesaian
Kita dpt menjawabnya :1. durasi 1 bit adlh 1/1 Kbps, atau 0.001 s (1 ms).2. rate link adlh 4 Kbps.3. duratsi dr tiap time slot 1/4 ms atau 250 ms. 4. durasi dr sebuah frame 1 ms.
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PENYELESAIAN SECARA RINCI :1
3/0
4/2
02
3
31Framems
FrameTimeSlotTimeSlots
berChannelNumrationTimeSlotDu
ionFrameDurat
TimeSlotsTimeSlotbitbits
UnitSizenBitDuratiorationTimeSlotDu
bitsbitms
ondbit
bit
bps
bitnBitDuratio
bpskbpskbpsDataRate
link
link
link
/1
/4*/250
/250/1/250
/250/25.0
sec/4000
1
4000
1
4000414
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INTERLEAVING Multiplexer/Demultiplexer memproses terminal/host’s unit
saling berkebalikan Character (byte) Interleaving
Multiplexing membentuk satu/lebih karakter(s) or byte(s) pd sebuah waktu (one byte per unit)
Bit Interleaving Multiplexing membentuk one bit pd satu waktu (one bit per unit)
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Contoh 2
Empat kanal dimultiplex menggunakan TDM. Bila masing2 kanal mengirimkan100 bytes/s dan kita memultiplex 1 byte per kanal, tunjukkan perambatan frame pd link, ukuran dr frame, durasi dr frame, kecepatan frame, dan bit rate dr link.
Penyelesaian
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PENYELESAIAN RINCI1
3/0
4/2
02
3
34
framemsFrameRate
ionFrameDurat
ondframeframebit
ondbit
FrameSizeDataRateFrameRate
bpsondbytes
ondbytesDataRate
framebitframebyte
timeslotbyteframetimeslot
UnitSizeberChannelNumFrameSize
link
link
/10
1
sec/100/32
sec/3200
/
3200sec/400
sec/1004
/32/4
/1/4
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Contoh 3
Sebuah multiplexer menggabungkan empat 100-Kbps kannels menggunakan sebuah time slot dr 2 bits. Tunjukkan output dng empat input sembarang. Berapakah frame ratenya? Berapakah durasi frame? Berapa bit rate? Berapa bit duration?Solution
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PENYELESAIAN RINCI
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36framems
ondframe
FrameRateionFrameDurat
ondframe
ondkframeframebit
ondkbit
FrameSizeDataRateFrameRate
bitondkBitRate
nBitDuratio
kbpskbpsDataRate
framebittimeslotbitframetimeslot
UnitSizeberChannelNumFrameSize
link
link
link
/20sec/000,50
1
1
sec/000,50
sec/50/8
sec/400
/
/sec400
11
4001004
/8/2/4
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SINKRONISASI
Satu /lebih Framing bit (s) ditambahkan ke masing2 frame utk singkronisasi antara multiplexer dan demultiplxer
Bila framing bit per frame, framing bits berubah-ubah antara 0 dan 1
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Contoh 4
Kita memiliki 4 sumber, masing2 membangkitkan 250 karakter per second. Bila interleaved unit adlh sebuah karakter dan 1 singkronisasi bit is ditambahkan ke masing2 frame, tentukan (1) data rate dr masing2 sumber, (2) durasi dr masing2 karakter dlm masing2 sumber, (3) frame rate, (4) durasi dr masing2 frame, (5) jumlah bits pd masing2 frame, dan (6) data rate dr link.
Penyelesaian
Lihat slide berikutnya
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Penyelesaian
Kita dpt menjawab pertanyaan tsb sbb berikut :
1. Data rate dr masing2 sumber adlh 2000 bps = 2 Kbps.2. Durasi dr sebuah karakter adlh 1/250 s, or 4 ms.3. Link diperlukan utk mengirim 250 frames per second.4. Durasi dr masing2 frame adlh 1/250 s, or 4 ms. 5. Masing2 frame adlh 4 x 8 + 1 = 33 bits.6. Data rate dr link adlh 250 x 33, or 8250 bps.
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PENYELESAIAN
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ondbit
framebitsondframe
FrameSizeFrameRateDataRate
ondframeFrameRate
framebits
framebittimeslotcharacterframetimeslot
gBitsFraUnitSizeberChannelNumFrameSize
sec/8250
/33sec/250
sec/250
/33
/1/1/4
min
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Contoh 5
Dua kannels, satu dng bit rate 100 Kbps dan yg lain dng bit rate 200 Kbps, dimultiplex. Bagaimana hal ini dpt dilakukan? Berapakah frame rate? Berapa frame duration? Berapa bit rate dr link?
Penyelesaian
Kita dpt mengalokasikan satu slot utk channel pertama dan dua slot utk channel kedua. Masing2 frame membawa 3 bits. Frame ratenya adlh 100,000 frames per second krn ia membawa 1 bit dr channel pertama. Frame duration nya adlh 1/100,000 s, atau 10 us. Bit rate adlh 100,000 frames/s x 3 bits/frame, atau 300 Kbps.
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PENYELESAIAN RINCI
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framesondframe
FrameRateionFrameDurat
ondframe
ondkframeframebit
ondkbit
FrameSizeDataRateFrameRate
framebit
UnitSizeUnitSizeFrameSize
kbpskbpskbpsDataRate
link
link
/10sec/000,100
1
1
sec/000,100
sec/100/3
sec/300
/
/3
300200100
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WDM
WDM dirancang utk membawa data dng kec tinggi...
Secara prinsip sama dng FDM... Hanya menggunakan perbedaan panjang
gel..
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STATISTICAL TDM
MEDIA TRANSMISI - OVERVIEW
Guided - wire Unguided - wireless Characteristics and quality determined by
medium and signal For guided, the medium is more important For unguided, the bandwidth produced by the
antenna is more important Key concerns are data rate and distance
DESIGN FACTORS
Bandwidth Higher bandwidth gives higher data rate
Transmission impairments Attenuation
Interference Number of receivers
In guided media More receivers (multi-point) introduce more
attenuation
ELECTROMAGNETIC SPECTRUM
GUIDED TRANSMISSION MEDIA
Twisted Pair Coaxial cable Optical fiber
TWISTED PAIR
TWISTED PAIR - APPLICATIONS
Most common medium Telephone network
Between house and local exchange (subscriber loop)
Within buildings To private branch exchange (PBX)
For local area networks (LAN) 10Mbps or 100Mbps
TWISTED PAIR - PROS AND CONS
Cheap Easy to work with Low data rate Short range
TWISTED PAIR - TRANSMISSION CHARACTERISTICS
Analog Amplifiers every 5km to 6km
Digital Use either analog or digital signals repeater every 2km or 3km
Limited distance Limited bandwidth (1MHz) Limited data rate (100MHz) Susceptible to interference and noise
UNSHIELDED AND SHIELDED TP
Unshielded Twisted Pair (UTP) Ordinary telephone wire Cheapest Easiest to install Suffers from external EM interference
Shielded Twisted Pair (STP) Metal braid or sheathing that reduces
interference More expensive Harder to handle (thick, heavy)
UTP CATEGORIES
Cat 3 up to 16MHz Voice grade found in most offices Twist length of 7.5 cm to 10 cm
Cat 4 up to 20 MHz
Cat 5 up to 100MHz Commonly pre-installed in new office buildings Twist length 0.6 cm to 0.85 cm
NEAR END CROSSTALK
Coupling of signal from one pair to another Coupling takes place when transmit signal
entering the link couples back to receiving pair
i.e. near transmitted signal is picked up by near receiving pair
COAXIAL CABLE
COAXIAL CABLE APPLICATIONS
Most versatile medium Television distribution
Ariel to TV Cable TV
Long distance telephone transmission Can carry 10,000 voice calls simultaneously Being replaced by fiber optic
Short distance computer systems links Local area networks
COAXIAL CABLE - TRANSMISSION CHARACTERISTICS
Analog Amplifiers every few km Closer if higher frequency Up to 500MHz
Digital Repeater every 1km Closer for higher data rates
OPTICAL FIBER
OPTICAL FIBER - BENEFITS
Greater capacity Data rates of hundreds of Gbps
Smaller size & weight Lower attenuation Electromagnetic isolation Greater repeater spacing
10s of km at least
OPTICAL FIBER - APPLICATIONS
Long-haul trunks Metropolitan trunks Rural exchange trunks Subscriber loops LANs
OPTICAL FIBER - TRANSMISSION CHARACTERISTICS
Act as wave guide for 1014 to 1015 Hz Portions of infrared and visible spectrum
Light Emitting Diode (LED) Cheaper Wider operating temp range Last longer
Injection Laser Diode (ILD) More efficient Greater data rate
Wavelength Division Multiplexing
OPTICAL FIBER TRANSMISSION MODES
WIRELESS TRANSMISSION
Unguided media Transmission and reception via antenna Directional
Focused beam Careful alignment required
Omnidirectional Signal spreads in all directions Can be received by many antennae
FREQUENCIES
2GHz to 40GHz Microwave Highly directional Point to point Satellite
30MHz to 1GHz Omnidirectional Broadcast radio
3 x 1011 to 2 x 1014
Infrared Local
TERRESTRIAL MICROWAVE
Parabolic dish Focused beam Line of sight Long haul telecommunications Higher frequencies give higher data rates
SATELLITE MICROWAVE
Satellite is relay station Satellite receives on one frequency, amplifies
or repeats signal and transmits on another frequency
Requires geo-stationary orbit Height of 35,784km
Television Long distance telephone Private business networks
BROADCAST RADIO
Omnidirectional FM radio UHF and VHF television Line of sight Suffers from multipath interference
Reflections
INFRARED
Modulate noncoherent infrared light Line of sight (or reflection) Blocked by walls e.g. TV remote control, IRD port
REQUIRED READING
Stallings Chapter 4 Komunikasi data by Dony
