Baseband Transmissions (1) Transmission Medium Sender Receiver Transmission Digital Signals 010 0 1...
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Transcript of Baseband Transmissions (1) Transmission Medium Sender Receiver Transmission Digital Signals 010 0 1...
Baseband Transmissions (1)
Transmission Medium
Sender ReceiverTransmission
Digital Signals 0 1 0 01
Signals all same shape
CS 590/490 Wireless Networks
Wireless_01/001
• A type of signal transmissions in which signals are directly inserted onto a signal transmission medium
Data
Transmission Medium
Signals all same shape
Analog Signals
CS 590/490 Wireless Networks
Fundamentals/002
Baseband Transmissions (1)
• A type of signal transmissions in which signals are directly inserted onto a signal transmission medium
Sender ReceiverTransmission
Baseband Transmissions (2)
• A type of signal transmissions in which signals are directly inserted onto a signal transmission medium
(the shape of the signals are same at the sender, in the transmission medium and even at the receiver)
• A type of signal transmissions that can transmit a signal from single sender at a time
(Transmission Medium)
CS 590/490 Wireless Networks
Fundamentals/003
Host A
Host B
Host C
Baseband Transmissions (2)
• A type of signal transmissions in which signals are directly inserted onto a signal transmission medium
(the shape of the signals are same at the sender, in the transmission medium and even at the receiver)
• A type of signal transmissions that can transmit a signal from single sender at a time
0 1 10 0 0 0 0 0
0 10 0 0 10 0 0
(Signals merged)
0 1 0 1 0 1 0 1
The receiver receives “01010101”,but can’t tell who sent which signals
CS 590/490 Wireless Networks
Fundamentals/004
(Transmission Medium)
Host A
Host B
Host C
• A type of signal transmissions in which signals are directly inserted onto a signal transmission medium
(the shape of the signals are same at the sender, in the transmission medium and even at the receiver)
• A type of signal transmissions that can transmit a signal from single sender at a time
(Transmission Medium)
The receiver will receive merged analogsignals, which will sound like gibberish
+
CS 590/490 Wireless Networks
Fundamentals/005
Baseband Transmissions (2)
Host A
Host B
Host C
(Signals merged)
Two major problems in baseband transmissions
Only one signal transmitter at a time
Can’t achieve (high-speed) (long distance) transmission
CS 590/490 Wireless Networks
Fundamentals/006
Baseband Transmissions (3)
Two major problems in baseband transmissions
Only one signal transmitter at a time
Wired networks = “transmission medium” is “cable”
CS 590/490 Wireless Networks
Fundamentals/007
Baseband Transmissions (3)
A
B
C
D
E
F
G
Cable A-F
Cable E-FCable A-D
Cable B-C
Cable B-G
• What if we need to support multiple simultaneous communication using the baseband transmission?
Install more cables!
(not efficient, but it would work)
Two major problems in baseband transmissions
Only one signal transmitter at a time
CS 590/490 Wireless Networks
Fundamentals/008
Baseband Transmissions (3)
• If we have to use the baseband transmission, only one user can use the cell phone at a time
We can’t install anothertransmission medium for thiscell.
Your cell phone company may haveTo build a tower for each active customer
Wireless networks = “transmission medium” is “open air”
Two major problems in baseband transmissions
Can’t achieve (high-speed) (long distance) transmission
Transmission Medium
Input(Sender)
Output(Receiver)Transmission
Digital Signals
Cable Length
?
Shorter Cable Length
CS 590/490 Wireless Networks
Fundamentals/009
Baseband Transmissions (3)
skew & distortion
We sacrificelong-distance
signal transmissions
Can’t achieve (high-speed) (long distance) transmission
Transmission Medium
?
2
1
0 01 1 0
Baseband Transmissions (3)
CS 590/490 Wireless Networks
Fundamentals/010
Two major problems in baseband transmissions
The minimum signal pattern possible
Time for one signal cycle= signal cycle time
# of signal cycles in one second
Signal frequency(in Hz)
skew & distortion
We sacrificeSignal frequency
(transmission speed)
Signal cycle
Baseband Transmissions (4)
Summary of baseband transmissions:
CS 590/490 Wireless Networks
Fundamentals/011
• A type of signal transmissions in which signals are directly inserted onto the transmission medium
• A type of signal transmissions that can transmit a signal from single sender at a time
• Two major problems in baseband transmissions
Since only one sender at a time, it is not an efficient for wireless signal transmissions
Can’t achieve (high-speed) (long distance) transmission
Wired signal transmissions
Either: (a) high-speed short distance transmissions
(b) low-speed long distance transmissions
• Baseband signals are susceptible to signal skews and distortions during during transmission (i.e. during propagation in the transmission medium
Cost-effective and high-speedsince no additional hardware
and processing is required
Baseband Transmissions (4)
CS 590/490 Wireless Networks
Since only one sender at a time, it is not an efficient for wireless signal transmissions
Can’t achieve (high-speed) (long distance) transmission
Wired signal transmissions
Either: (a) high-speed short distance transmissions
(b) low-speed long distance transmissions
PC Motherboard
MemoryModules
MemoryBus
Processor
Graphicsubsystem
InternalBus
0 0 01 1 1
0 0 01 1 1
0 0 01 1 1
0 0 01 1 1
High-speedShort-distance
Basebandtransmissions
Fundamentals/012
Baseband Transmissions (4)
CS 590/490 Wireless Networks
Since only one sender at a time, it is not an efficient for wireless signal transmissions
Can’t achieve (high-speed) (long distance) transmission
Wired signal transmissions
Either: (a) high-speed short distance transmissions
(b) low-speed long distance transmissions
PC Motherboard
MemoryModules
MemoryBus
Processor
Graphicsubsystem
InternalBus
keyboard Mouse
Printer
0 0 01 1 1
0 0 01 1 1
0 0 01 1 1
Slower I/O devices
Low-speedLong-distance
Basebandtransmissions
High-speedShort-distance
Basebandtransmissions
Fundamentals/013
• A type of signal transmissions in which signals are first modulated onto “carrier signals” and then modulated signals are inserted onto a signal transmission medium
Digital Signals
Modulator
ModulatedSignals
ModulatedSignals
DeModulator
Transmission Medium
Carrier Signal Carrier Signal
CS 590/490 Wireless Networks
Fundamentals/014
Broadband Transmissions (1)
Data
0 1 0 01
Carrier signal = sin curve analog signal defined by three parameters
Time0
+v
-v
Am
plit
ude
(vol
t or
pow
er)
t
A (Amplitude)
F (Frequency) = 1 second / t
CS 590/490 Wireless Networks
Fundamentals/015
Broadband Transmissions (2)
Carrier signal = sin curve analog signal defined by three parameters
Time0
+v
-v
Am
plit
ude
(vol
t or
pow
er)
t
t/4 2t/4 3t/4
CS 590/490 Wireless Networks
Fundamentals/016
Broadband Transmissions (2)
900 180 270
P (Phase) in degree (0 P 360 )
Why “carrier signal”?
Sin carrier signals are known to have no skew or distortion on the signal-shape (even for long distance transmission)
Each sin carrier signal has a specific frequency and two carriers with different frequency can be separated at a receiver
Broadband Transmissions (3)
CS 590/490 Wireless Networks
Fundamentals/017
Why “carrier signal”?
Sin carrier signals are known to have no skew even for long distance transmission
Input(Sender)
Output(Receiver)Transmission
Carrier signals with a specific frequency
Distance =
= not affected= not affected= decrease
• P• F• A
The only limiting factor for transmissiondistance = Transmission Power (W)
If there is no“noise”
Broadband Transmissions (3)
CS 590/490 Wireless Networks
Fundamentals/018
Why “carrier signal”?
Each sin carrier signal has a specific frequency and two carriers with different frequency can be separated at a receiver
Transmission Medium
Senders
FDMMultiplexer
FDMDe-Multiplexer
Receivers
Broadband Transmissions (3)
CS 590/490 Wireless Networks
Fundamentals/019
No “phase”, not “amplitudebut “frequency”
1
21 2
modulatedcarrier
Why “carrier signal”?
• Sin analog carrier signal itself does not have any meaning
SendersReceivers
• We override our payload signals on top of the carrier signal
Called “modulation”
FDMMultiplexer
FDMDe-Multiplexer
Tx Medium
carrier
carrier
carrier
carrier
modulatedcarrier
payloadsignals
payloadsignals
payloadsignals
payloadsignals
ModulatorDeModulator
Broadband Transmissions (4)
CS 590/490 Wireless Networks
Fundamentals/020