DATA TRANSMISSION

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MECHANICAL MEASUREMENTS
Prof. Dr. Ing. Andrei Szuder Tel.
40.2.1.4112604 Fax. [phone] www.labsmn.pub.
ro szuder_at_labsmn.pub.ro
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DATA TRANSMISSION
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DATA TRANSMISSION

• An ideal data transmission system gives an output
  which is identical to the input Three problems in
  data transmission
• noise
• attenuation
• distortion.

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Noise

• A variation in output not caused by a variation
  in the measurand is noise
• It gives an error in the measurement unless it
  is removed
• It is quantified as the signal-to-noise ratio
  (SNR)

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Attenuation

• Energy losses in the transmission medium mean
  that the amplitude of the signal is reduced
• Reduces the SNR
• Reduces the signal level

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Distortion

• Arises when the frequency response of
  transmission system is inadequate to deal with
  the frequencies in the signal.

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Analogue data transmission

• Generally done by using conducting wires to feed
  the transducer output to the signal processing,
  recording and/or display unit.
• Wires may be simple single strand conductors, or
  may be co-axial cables.
• Co-axial cables consist of
• inner conductor
• insulating layer
• outer earthing and screening conductor
• final insulating layer outside.

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Analogue data transmission

• Thickness and purity of both conductors and
  insulators vary the cost varies accordingly.
• Reduction of attenuation and noise mean
  increased cost.

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Effect of noise on transmitted analogue data

• Low levels of noise enable the signal to be
  detected with very small errors
• High levels of noise may totally obscure the
  signal.
• Noise arises from
• external sources
• noise generated in the conductor itself.

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Effect of noise on transmitted analogue data

• Coaxial cables reduce these problems compared
  with single wires
• Internal noise is related to the size, length
  and quality of the conductors.
• Isolation from external pickup reduces with
  thicker, better quality insulation

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Effect of attenuation on transmitted analogue
data

• Attenuation is determined by the thickness and
  quality of the conductor in the cable.
• Also determined by distance (length of cable)

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Effect of distortion on transmitted analogue data

• Distortion effects are related to frequency
  response
• The transmission system deals adequately with the
  low frequency
• A higher frequency is, however, barely
  transmitted.
• The frequency response of co-axial cable varies
  with cost.

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Transmission distance

• The greater the distance, the more serious all
  these problems are
• Simple conducting wires may be adequate to carry
  a signal over a distance of a metre
• More expensive coaxial cable will be required to
  carry the same signal to the same display system
  over a longer distance.

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Serial data transmission

• Signal sent as a series of pulses
• '1' represented by pulses at one voltage level
• '0' represented by pulses at different voltage
  level. The received signal is converted back to
  the original binary number
• A pulse is recognised as either '0' or '1' when
  it falls within prescribed limits.

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SERIAL TRANSMISSION
TRANSDUCERS
COMUTATION
DATA TRANSMISSION
DISPLAY RECORDING
MEASURAND
CYCLE
TRANSDUCERS
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Serial data transmission

• If the noise and distortion are below specific
  amounts, the received signal is exactly equal to
  transmitted signal
• Transfer of data is controlled by various signals
  to indicate the start and finish of individual
  numbers
• Various methods for checking the data used
• Standard serial transmission line are available,
  e.g. RS232.

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PARALLEL TRANSMISSION
DISPLAY RECORDING
UTILIZATION
TRANSDUCER
SIGNAL TRANSMISSION
MEASURAND
SINCHRONIZATION
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PARALLEL TRANSMISSION

• Separate cables for each measurand
• Faster than serial
• More complex
• Communication systems between computers and other
  systems - Standards IEEE, S-100, CAMAC.

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Parallel data transmission

• The individual bits of the binary number are sent
  in parallel along separate lines.
• It is faster than serial transmission for a given
  rate of bit transfer
• It is more complex.
• A variety of such systems have been developed
  for communication between computers and other
  systems - IEEE, S-100, CAMAC.

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Noise, attenuation and distortion in digital
transmission

• None of these are a problem unless '1's cannot be
  distinguished from '0's.
• Sampling rate must be high enough to 'see' all
  frequencies - Nyquist criterion

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Optical fibres for data transmission

• Used only for digital data transmission.
• They have been extensively developed for use in
  telecommunications
• They operate at frequencies of many GHz.
• They have very low attenuation over long
  distances
• A major advantage is that they are not subject
  to interference from external EM sources.

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Optical fibres for data transmission

• They are much lighter than copper cables
• They are better in hazardous environments where
  intrinsically safe equipment is required
  (explosive environments such as mines, chemical
  factories).
• They are much lighter than copper cables

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Optical fibers for data transmission

• They are available with a variety of performance
  specifications
• The higher the specification, the more
  expensive.
• Currently more expensive than the equivalent
  conducting system
• May change as the raw material (sand) is much
  cheaper than copper or other metals.

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Analogue vs. digital data transmission

• Analogue data transmission is simpler, therefore
  cheaper than digital data transmission.
• Normally the first choice if the signal has to
• travel a long distance
• go through an electrically noisy environment or a
  hazardous atmosphere
• is at a high frequency

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Analogue vs. digital data transmission

• If the signal is to be input to a computer, it
  may be worth converting to it to digital form
  before transmission.

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DATA TRANSMISSION SUPPORT

• FILAR CABLE
• COAXIAL CABLE
• OPTICAL FIBERS Eliminating noise, electrical
  insulation,
• optoelectronics
• RADIO
• Long distance
• Close distance (10-100 m) technology BLUETOOTH
• INTERNET
• INTRANET

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Transmission of data using EM propagation

• Used for transmission
• over long distance
• through hostile environments
• The signal is superimposed on a radio wave at a
  much higher frequency (carrier wave) as either
• amplitude modulation (AM)
• frequency modulation (FM).

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Transmission of data using EM propagation

• The radio wave is transmitted through the air
• It is picked up by a receiver
• It is then demodulated back into its original form

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RADIOTRANSMISSION
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RADIO TRANSMISSION
APLLICATIONS
RANGE
RANGE
Classic telephone
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RADIO TRANSMISSION
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Carrier wave
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AM modulation
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AM modulation
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FM modulation

• Carrier frequency changes according to the level
  of the signal
• FM much less susceptible to noise and distortion
  and noise than AM

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FM modulation
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Fibrele optice pentru transmiterea datelor

• Utilizate pentru transmiterea digitala a datelor.
  
• Sunt utilizate in telecomunicatii
• Functioneaza la frecvente extrem de mari
• Atenuare foarte mica pe distante mari
• Nu sunt supuse interferentelor cu surse externe
• Sunt mai usoare decat cablurile de Cu
• Mai scumpe

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TRANSMISIA DATELOR

• Intr-un sistem ideal de transmisie a datelor
  marimea de intrare este identica cu cea de iesire
  
• Probleme care apar la trensmiterea datelor
• zgomot
• atenuare
• distorsia semnalelor.

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• Zgomot
• O variatie a marimii de iesire ne cauzata de o
  variatie a masurandului. Surse externe si
  interne. Calitatea izolatiei
• Produce o eroare de masuare daca nu este
  indepartat
• Se masoara prin raportul semnal - zgomot

• Atenuare
• Pierderile energetice in timpul transmisiei se
  manifesta prin reducerea amplitudinii semnalului.
  
• Reduce raportul semnal-zgomot si nivelul
  semnalului
• Calitatea si lungimea cablului

• Distorsia
• Se produce cand raspunsul in frecventa a
  sisstemului de transmisie este neadecvat cu
  frecventa semnalului. Depinde de calitatea
  cablului
• Mai mare la frecvente mare.

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ETHERNET CONNEXIONS
10 Base - T
10 Base - 2
CABLURI TORSADATE 100 m 10Mbps
COAXIAL GROS 500 M MAX 10 Mbps
COAXIAL FIN 185 m 10 Mbps
HUB
100 Base - TX
COAXIAL
100 Base - FX
FIBRA OPTICA 2000 m 100 Mbs
CABLURI TORSADATE 100 m 100Mbps
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INTERNET
GPRS - General Packet for Radio Services EGPRS -
Enhanced General Packet for Radio Services UMTS -
Universal Mobile Telecommunication System
SERVER WAP
BASE STATION
2001- GPRS si EGPRSPhoto E_ commerce Muzica
(MP3) Ziare Banca max 144si 384 Kbits/s F 900
si 1800 MHz
2002 - UMTS TV pictures Radio
Games Videophon max 2 Mbits/s F 2 GHz
1999 - GSM Voice Fax Mesages E_Mail max 9,6
Kbits/s F 900 si 1800 MHz
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SATELITTE DATA TRANSMISSION
Satellite frequency (FS) 10,729 la 12,670 GHz
SATELLITE
PARABOLIC ANTENNA
LN C Oscillator frequency local (FOL) 9,75 GHz
13 or 18V (Polarization)
SATELLITE DEMUDALATOR 950 at 2150 MHz
TV
Frequency in cable (FC) 979 MHz at 2920 MHz FC
FS-FOL
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PROTOCOLURI TCP / IP
Principiu - Comutarea pachetelor Mesajele
decupate in pachete Pachete trimise pe drumul cel
mai scurt Noduri terminal - calculatoarele care
schimba informatii Rutare dinamica - leagatura
pate fi facuta prin multiple intinerarii Transmis
ion Control Protocol - Controleaza integritatea
informatiei Internet Protocol - Transmterea
informatiei
Adresare logica - Placa retea. Numar
identificare calculator ID Rutare - citeste
adresle logice si orienteaza datele catre
destinatar Nume si adrese - Corespondenta dintre
adresa ID si Numele de Domeniu -DNS Controlul
erorilor si debitelor (data flow) Suportul de
aplicatie - Intrefata pentreu ca aplicatiile se
pe calculator sa poata accede la retea
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PROTOCOLURI TCP / IP
MODULELE TCP / IP

• ACCES RETEA - INTERFATA CU RETEAUA
• Formateza datele dupa normele sub retelei tinând
  cont de adresele destinatarilor
• Controleaza erorile
• INTERNET - ADRESARE LOGICA
• Asigura rutarea datelor
• Evita aglomerarea datelor
• TRANSPORT - CONTROLUL FLUXULUI DE DATE
• Gestioneza si contoleaza erorile
• Interfata pentru aplicatii
• APLICATIE - FURNIZEAZA APLICATIILE PENTRU
  TRANSFERUL DE FISIERE
• APLICATIE PREZENTARE - FORMATAREA, CRIPTAREA SI
  COMPRESIA DATELOR SESIUNE - DESCHIDE SESIUNILE
  CARE LEAGA APLICATIILE PE
• CALCULATOARELE INTERCONECTATE

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WAP - WIRELESS APPLICATION PROTOCOL
UTILIZAREA COMUNA A TELEFONIEI MOBILE SI A
INTERNETULUI
Comunicarile GSM - 9,6 Kbits / s , Internet 56,6
Kbits/ s47 Utilizarea standardelor de comunicare
internet in forma concisa Limbajul HTML -
WML ( Wireless Markup Language) 1997 Traducere
care ia timp. Viteza de transfer
redusa. Legatura infrarosu IrDA pentru
transferarea datelor pe calculator Consum mare
de energie (Autonomie max 6 ore)
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BLUETOOTH
MODUL GESTIONARE asigura compatibilitatea între
protocolul BLUETOOTH si interfata utilizator
PC SISTEMACHIZITIE DATE
EMITATOR / RECEPTOR 2,4 GHz
MODUL CONTROL
Lungimea mesaj 625 ?s
Canale voce - 64 Kb/s Canal asincron 433,9 Kb/s
in mod sincron
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COMPRESIA DATELOR
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DECOMPRESIA DATELOR
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ISDN
Services integration Transmssion voice, images,
data
Digital link duplex shared by independent
channels time multiplexed pe A Analogical
telephone channel -4 KHz B- Digital cable 64
Kbits/s (PCM- Pulse Code Modulation) C Digital
channel 8 or16 Kbits/s D - Digital channel 16
or64 Kbits/s for signalization
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TRANSMISIA NUMERICA IN BANDA DE BAZA
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TRANSMITEREA PRIN MODULAREA IMPULSURILOR
CODIFICATE