Media Integrated Communication Area (Babaguchi Laboratory ...
Laboratory 10: Communication General Engineering Polytechnic University.
-
Upload
ralf-evans -
Category
Documents
-
view
215 -
download
0
Transcript of Laboratory 10: Communication General Engineering Polytechnic University.
Laboratory 10:Laboratory 10:CommunicationCommunication
General Engineering
Polytechnic University
OverviewOverview
Objective Transmission of
Media LASER Fiber-Optics Signal Forms Number Systems
and Codes
Conversions Error Detection Error Correction Materials for Lab Procedure Written Assignment Recitation Topics Closing
ObjectivesObjectives
Learn the principles of free-space laser communication systems
Study the fundamentals of analog fiber-optic communications
Measure the frequency response of a fiber-optic link, and find its bandwidth
Demonstrate how digital data from a computer can be transmitted optically
Learn about computer ASCII characters Learn the difference between analog and digital
message signals
Transmission of MediaTransmission of Media
There are two types:
– Guided - Signal travel through a cableUses: Telephone
– Non-Guided - Signal travels through airUses: AM & FM Radio,
Television
LASER (Non-Guided)LASER (Non-Guided)
Powerful: Contains one frequency of light and the waves are coherent (in phase)– A light bulb has many
frequencies of light and the waves incoherent (out of phase), making it weak
LL
AA
SS
EE
RR
ightight
mplification mplification byby
timulatedtimulated
mission ofmission of
adiationadiation
LASER (Non-Guided)LASER (Non-Guided)
Applications– Industry
diamond cutting shape machine
tools
– Scientific Research study molecular
structures of matter
– Communication television telephone computers
– Medicine surgery eyes
– Military missile guidance
Fiber-Optics (Guided)Fiber-Optics (Guided)
Made of glass The light that travels through the cable is a LED
(light emitting diode) Uses the principle of Total Internal Reflection
– Light goes through cable by bouncing off the glass walls
– The light & signal gets reflected back into the medium
Light in Light out
Fiber-Optics (Guided)Fiber-Optics (Guided)
Advantages– Transmits date faster
than conventional means
– More than one signal can be sent at the same time
– No line of sight
Disadvantages– Expensive
– Transmission is lost if cable is cut or bent
Signal FormsSignal Forms
Analog - The signal is continuous (infinite number of states), ranging between a high and low voltage
Time (sec)
Voltage (V)
Signal FormsSignal Forms
Digital - The signal is discreet (only 2 states), there is no range only “on’s” and “off’s”– Active High (high=1)– Active Low (low=1)
Digitizing - Converting an analog signal to a digital signal
0
1Active Low
1 1
0 0 0
Time (sec)
Voltage (V)
Number Systems and CodeNumber Systems and Code American Standard Code
for Information Interchange (ASCII)– Each alphanumeric character is coded so that it can be stored and
read by the computer– Each character is given a specific number or code– An abbreviated chart can be found on page 92
Number Systems– Decimal
Based on 10 possible values; 0 to 9
57610 = (5*102) + (7*101) + (6* 100)
= 500 + 70 + 6 = 576– Binary
Based on 2 possible values; 0 and 1
ConversionsConversions
Binary to Decimal– Similar to expanding a decimal number– 11012 = (1*23) + (1*22) + (0*21) + (1*20)
= 8 + 4 + 0 + 1 = 1310
)2 1310
)2
6 R1)2
3 R0)2
1 R1
0 R1
Read
Do
wn
1310 = 11012
Decimal to Binary– Continue to divide the decimal number by 2, until
the quotient reaches zero– The remainder values become the binary value
Error DetectionError Detection
Whenever a signal is sent, there is possibility for error
Error can be detected by– Redundancy - repeating the entire message and
comparing the two transmissions (wastes channel and storage capacity)
– Parity Bit - A bit added on to a 7-bit character so the byte has an even or odd number of 1’s (only can be used to detect a single-bit error)
NOTE: NOTE: 8 bits = 1 byte8 bits = 1 byte
Error CorrectionError Correction
Error can be corrected by – Vertical & Horizontal Parity Check
Arrange message in 4 x 4 array Choose parity bits to make all columns and
rows have even (or odd) number of 1’s
– Hamming Code Place message bits in overlapping circles Choose parity bits, so each circle has even
parity
Vertical & Horizontal Parity CheckVertical & Horizontal Parity Check
MessageMessage Horizontal Parity Horizontal Parity BitBit
Vertical Parity Vertical Parity BitBit
00
00
11
1100 111111
00 00 1111
00 0011 11
Place a 0 Place a 0 to keep even to keep even amount of amount of one’sone’s
Place a 1 Place a 1 to get even to get even amount of amount of one’sone’s
Place a 1 to Place a 1 to get even amount get even amount of one’sof one’s
Place a 0 to Place a 0 to keep even keep even amount of one’samount of one’s
Place a 1 Place a 1 to get even to get even amount of amount of one’sone’s
Place a 0 Place a 0 to keep even to keep even amount of amount of one’sone’s
Place a 0 to Place a 0 to keep even keep even amount of one’samount of one’s
Place a 1 to Place a 1 to get even amount get even amount of one’sof one’s
11 0011 11
00 001111
11 0011 11
00 001111
00 00 1111
1100 111100
still evenstill even
still evenstill even
still evenstill even
still evenstill even still evenstill even still evenstill even
ODD!ODD!
ODD!ODD!
WRONGWRONG
BITBIT
Message SentMessage Sent
1110 1010 0111 01011110 1010 0111 0101
NOTE: The NOTE: The parity bits do parity bits do NOT changeNOT change
Message SentMessage Sent
1110 1010 0111 01011110 1010 0111 0101
Message Sent
1110 1010 0111 0101
Message ReceivedMessage Received
1110 1010 0011 01011110 1010 0011 0101
Hamming CodeHamming Code
P3
P1P2 P1P2
P3
Message SentMessage Sent
MM1 1 11
MM22 0 0
MM3 3 11
MM4 4 1100 11
11
11
P1
1
P2
P3
P2
M4
M3M2
M1
0 1
0
1
0
Place 0 to keep Place 0 to keep even amount of even amount of one’s in gray one’s in gray circlecircle
Place 1 to get Place 1 to get even amount of even amount of one’s in pink one’s in pink circlecircle
0Place 0 to keep even Place 0 to keep even amount of one’s in amount of one’s in green circlegreen circle
ODD amount of onesODD amount of ones
((BAD!BAD!))
Save circle for laterSave circle for later
ODD amount of onesODD amount of ones
((BAD!BAD!))
Save circle for laterSave circle for later
Even amount of ones Even amount of ones ((GOOD!GOOD!))
Disregard circleDisregard circle
Only message bit in Only message bit in allall the “ODD” circles the “ODD” circles therefore…therefore… WRONG WRONG
BITBIT
NOTE: Parity bits do NOTE: Parity bits do NOT changeNOT change
Message SentMessage Sent
MM1 1 11
MM22 0 0
MM3 3 11
MM4 4 11
Message SentMessage Sent
MM1 1 11
MM22 0 0
MM3 3 11
MM4 4 11
Message Sent
M1 1
M2 0
M3 1
M4 1
Message ReceivedMessage Received
MM1 1 11
MM22 0 0
MM3 3 00
MM4 4 11
Materials for LabMaterials for Lab
Function Generator 1 BNC connector Amplified Speaker 2 Coax cables (BNC to
alligator clip) 4 miniature clip leads Computer with
LabVIEW Oscilloscope
Fiber-optic Trainer
– Transmitter
– Receiver
– 5-meter fiber-optic cable
ProcedureProcedure
Laser Demonstration -
Performed by Instructors– Components:
Audio Cassette Recorder - Source of the music, modulates the intensity of the laser
Helium-neon Laser - What the music will travel along, optical transmitter
Photo-diode - Responds to the light and produces a electrical signal proportional to the music signal, recovering the music, optical receiver, demodulates laser beam
Speaker - Destination of the music
•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System -on System -DigitalDigital
ProcedureProcedure
Laser Demonstration -
Performed by Instructors•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System - on System - DigitalDigital
Cassette
Recorder
Helium-Neon
Laser
Photo-DiodeSpeaker
Music Signal Light Free-Space
Music Signal
ProcedureProcedure
Laser Demonstration -
Performed by Instructors•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System - on System - DigitalDigital
ProcedureProcedure Fiber-Optic Communication System - Analog
– Turn on the transmitter and receiver circuit boards of the fiber-optic trainer & set the slide switch to “Analog” on both boards
– Connect the boards together with the use of the fiber-optic cable
– Connect the speaker to the receiver using two miniature clip leads
– Speak into the microphone on the transmitter board while your partner listens to the speaker at the receiver’s side
– Unplug the fiber-optic cable from the receiver input to observe the visible light beam emitted from the cable
•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System - on System - DigitalDigital
ProcedureProcedure
Fiber-Optic Communication System - Analog•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System - on System - DigitalDigital
Analog Fiber-Optic Transmitter (with Microphone)
Analog Fiber-Optic Receiver(with Audio Power Amplifier)
Speaker5-Meter
Critical Fiber
NOTE: Setup Diagram A on page 90
ProcedureProcedure
Fiber-Optic Communication System - Analog– Adjust the function generator to produce 200mV
peak-to-crest (0.2 V), 1 kHz sine wave– Connect the function generator, the DAQ board
and the circuit boards according to Diagram B on page 91
– Measure the gain vs. frequency (f) and complete the data sheet on page 91
Vout denotes the amplitude of the sinusoidal voltage appearing at the receiver's output
Vin represents the amplitude of the sinusoidal transmitter input signal
•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System - on System - DigitalDigital
ProcedureProcedure
Fiber-Optic Communication System - Analog•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System - on System - DigitalDigital
Function Generator200mV peak-to-crestSine Wave
Analog Fiber-Optic Transmitter
LabVIEW Oscilloscope
Analog Fiber-Optic Receiver(with Audio Power Amplifier)
5-Meter
Critical Fiber
Vout
Vin
NOTE: Setup Diagram B on page 91
ProcedureProcedure TCP/IP Communication System - Digital
– Establish a connection between two computers by using the ‘Talk Active’ and ‘Talk Passive’ VIs
– Type a message (e.g. “HELLO BETH”) and click the send button on the VI.
Sent messages are displayed in the “Local” window Received messages are displayed in the “Remote” window
– Disconnect the computers and reconnect them using the ‘Writer’ and ‘Reader’ VIs
– Type in a message (16 characters or less) on the transmitting computer
– Compare the number displayed on the receiving computer with the ASCII code on page 92 and find the corresponding alphanumeric character
•Laser Laser DemonstratioDemonstrationn
•Fiber-Optic Fiber-Optic CommunicatiCommunication System - on System - AnalogAnalog
•TCP/IP TCP/IP CommunicatiCommunication System - on System - DigitalDigital
Written AssignmentWritten Assignment
Full Team Report (one report per team) Use the guidelines on page 5 for help Create a graph of gain vs frequency of the table you
completed on page 91– Be sure to use a log scale for the x-axis– Find the 3dB point and bandwidth of your
communication system Make sure your instructor initials your original data Include the topics found on the next slide Remember to create a title page
Written TopicsWritten Topics Each of the following topics must be addressed in the
full report and should be placed in the proper sections– Explain the lab demonstration on the laser communication
system
– What is the significance of the bandwidth measurement of the frequency response graph?
– From your result would you say your fiber-optic-link is capable of transmitting video signals from a camcorder which requires frequencies of about 5 MHz?
– Describe the results obtained with the TCP/IP connection you set up. Were there any problems?
– Summarize the advantages of fiber-optic systems. Are there any disadvantages?
Recitation TopicsRecitation Topics
Discuss the differences between analog and digital signals
Discuss the relative strengths and weaknesses of the three communication media covered in this lab.
Discuss the relationship between bandwidth and frequency as they relate to gain, baud rate, and scan rate
ClosingClosing
Return all the equipment back to your instructor