CSE350 Lec2 Data Transmission

8/6/2019 CSE350 Lec2 Data Transmission

1/33

CSE 350

Lecture 2: Data Transmission

Maheen Islam


2/33

Terminolo 1

Receiver

Guided medium

. . ,

Unguided medium

e.g. air, water, vacuum


3/33

Terminolo 2

No intermediate devices

- -

Direct link

Multi-point


4/33

Terminolo 3

One direction e. . Television

Half duplex

Either direction but onl one wa at a time

e.g. police radio

Full duplex

Both directions at the same time

e.g. telephone


5/33

Fre uenc , S ectrum and Bandwidth

Continuous signal Various in a smooth wa over time

Discrete signal

Maintains a constant level then changes to another constantlevel

Periodic signal

a ern repea e over me Aperiodic signal


6/33

Continuous & Discrete Si nals


7/33

Periodic

gna s


8/33

Sine Wave Peak Am litude A

maximum strength of signal volts

Frequency (f)

Rate of change of signal Hertz (Hz) or cycles per second

Period = time for one repetition (T)

Phase ()


9/33

Var in Sine Waves


10/33

Wavelen th

Distance between two points of corresponding

= vT

c = 3*108 ms-1 (speed of light in free space)


11/33

Fre uenc Domain Conce ts

Components are sine waves

made up of component sine waves


12/33

FrequencyComponents


13/33

Frequency

omain


14/33

S ectrum & Bandwidth S ectrum

range of frequencies contained in signal

Absolute bandwidth

width of spectrum

Effective bandwidthOften just bandwidth

Narrow band of frequencies containing most of the energy

DC Component

Component of zero frequency


15/33

Si nal with DC Com onent


16/33

Data Rate and Bandwidth

frequencies


17/33

Analo and Di ital Data Transmission

Entities that convey meaning

Electric or electromagnetic representations of data

Communication of data by propagation and processing

of si nals


18/33

Data

Continuous values within some interval

Digital

e.g. text, integers


19/33

Acoustic S ectrum Analo


20/33

Si nals Means b which data are ro a ated

Analog Continuously variable

Various media

wire, fiber optic, space Speech bandwidth 1 Hz to 7kHz

Telephone bandwidth 300Hz to 3400Hz

Digital


21/33

Data and Si nals

analog signals for analog data

Modem

Compact Disc audio


22/33

Analog Signals Carrying Analog and

g a a a


23/33

Digital Signals Carrying Analog and

g a a a


24/33

Analo Transmission

May be analog or digital data

Use amplifiers to boost signal

so amp es no se


25/33

Di ital Transmission

Integrity endangered by noise, attenuation etc.

Repeater receives signal

xtracts t pattern

Retransmits

Attenuation is overcome Noise is not amplified


26/33

Advanta es of Di ital Transmission Di ital technolo

Low cost LSI/VLSI technology Data integrity Longer distances over lower quality lines

Capacity utilization Hi h bandwidth links economical High degree of multiplexing easier with digital techniques

Security & Privacy

ncryption Integration Can treat analo and di ital data similarl


27/33

Transmission Im airments

Analog - degradation of signal quality-

Caused by

enua on an a enua on s or on

Delay distortion


28/33

Attenuation Signal strength falls off with distance

Depends on medium

Received signal strength:

must be enough to be detected

must be sufficiently higher than noise to be receivedwithout error

Attenuation is an increasing function of frequency


29/33

Dela Distortion

Propagation velocity varies with frequency


30/33

Noise 1

receiver

Due to thermal agitation of electrons

Uniforml distributed

White noise

Signals that are the sum and difference of original

frequencies sharing a medium


31/33

Noise 2

A signal from one line is picked up by another

Irregular pulses or spikes

Short duration

Hi h am litude


32/33

Channel Ca acit

In bits per second

Bandwidth

Constrained by transmitter and medium


33/33

Re uired Readin

Date post:	07-Apr-2018
Category:	Documents
Upload:	khaled-bin-yousuf-sujhon
View:	219 times
Download:	0 times

CSE350 Lec2 Data Transmission

Documents