Baseband Transmissions (1)

Transmission Medium

Sender ReceiverTransmission

Digital Signals 0 1 0 01

Signals all same shape

CS 590/490 Wireless Networks

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• 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

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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

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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

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(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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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)

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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

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