ECE- 4074 W eb Si te http: //w w w . csc. gatech. edu/~copel - - PowerPoint PPT Presentation

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ECE- 4074 W eb Si te http: //w w w . csc. gatech. edu/~copel - - PowerPoint PPT Presentation

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ECE- 4074 W eb Si te http: //w w w . csc. gatech. edu/~copel and/4074 Pr of . John A . Copel and j ohn. copel and@ ece. gatech. edu 404 894- 5177 O f f i ce: GCA TT 579 F or of f i ce vi si t, em ai l or

slide-1
SLIDE 1

ECE- 4074

W eb Si te http: //w w w . csc. gatech. edu/~copel and/4074

Pr

  • f

. John A . Copel and j

  • hn.

copel and@ ece. gatech. edu 404 894- 5177

O f f i ce: GCA TT 579

For

  • f

f i ce vi si t, em ai l

  • r

cal l m e

  • r

dr

  • p

by dur i ng

  • f

f i ce hour s posted

  • n

the W eb Si te

A ppendi ces 3A - 3C, pp 115- 120

  • Fr

am i ng

  • Rati
  • s

as Deci bel s

  • Char

acter i sti c I m pedance

  • Scr

am bl i ng

EE4074. 03 v8

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SLIDE 2

Char acter i sti c I m pedance

A uni f

  • r

m tr ansm i ssi

  • n

l i ne w i l l conduct an el ectr i cal pul se

  • i

n

  • ne

di r ecti

  • n

at a constant speed ( usual l y ~ 2E8 m /s)

  • w i

thout r ef l ecti

  • n

i f the end i s ter m i nated w i th R = Zo

+

  • R

V ol tage Di stance Tr ansm i tter Tr ansm i ssi

  • n

Li ne, Zo = R

slide-3
SLIDE 3

Deci bel s = 10 * l

  • g

(Rati

  • )

Loss f actor = . 05

  • 13

dB Gai n f actor = 40 =16 dB Gai n f actor = 100 = 20 dB Loss f actor = . 01 =

  • 20

dB Loss f actor = . 02 =

  • 17

dB Ci r cui t Gai n = . 05 x 100 x . 02 x 40 x . 01 0. 04

Ci r cui t Gai n =

  • 13

dB +20 dB

  • 17

dB +16 dB

  • 20

dB

  • 14

dB

.

05 = 10**- 1. 3

100

= 10**+2.

.

02 = 10**- 1. 7

40

= 10**+1. 6

.

01 = 10 **- 2.

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SLIDE 4

Deci bel Rel ati

  • nshi

ps

Rati

  • dB

Q ui ck Cal cul ati

  • n

1 1 = 10**0 1. 25 1 1. 25 = 5/4 = 7- 6 dB 2 3 (5/4)**3 = 125/64 4 6 2*2 = 3+3 dB 5 7 10/2 = 10- 3 dB 8 9 2*2*2 = 3+3+3 dB 10 10 10**1 100 20 10**2 1000 30 10**3 1/R

  • D

w her e R

  • >

D l

  • g(1/x)

=

  • l
  • g(x)

1+0. 25*f f f < 1 (f r acti

  • n)

M em or i ze the r ati

  • s

cor r espondi ng to 1, 3, and 10 dB, and you can qui ckl y cal cul ate the r ati

  • f
  • r

any dB.

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SLIDE 5

Bi t- O r i ent Fr am i ng

10010111111001101000011001010110110001101000110111110011 1001 01111110 01001000 01000101 01001100 01001100 01001111 10011 Start H E L L O O ne techni que i s to use a speci al 8- bi t "f l ag" code (byte

  • r
  • ctet)

that contai ns si x "1"s i n a r

  • w

(01111110). A str eam

  • f

0' s and 1' s ar e r ecei ved. W e know i t i s text data (char acter s encoded as 8- bi t codes). W her e ar e the f i r st bi ts

  • f

a code? Flag Flag Dat a The "f l ags" "f r am e" the "data". Thi s type

  • f

str uctur e i s cal l ed a "packet", "cel l "

  • r

"f r am e" dependi ng

  • n

the pr

  • tocol

.

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SLIDE 6

Bi t Stuf f i ng

To pr event a f l ag- l i ke sequence appear i ng i n the data, the f

  • l

l

  • w i

ng r ul e i s appl i ed w hen the f r am e i s f

  • r

m ed:

  • A f

ter f i ve "1"s i n a r

  • w ,

an extr a zer

  • i

s "stuf f ed" i nto the bi t str eam (w hether the next bi t i s a "1"

  • r

a "zer

  • ").

W hen data i s taken

  • ut
  • f

a f r am e at the r ecei vi ng end, the f

  • l

l

  • w i

ng r ul e r estor es the data:

  • w henever

f i ve "1"s i n a r

  • w

appear , the next bi t i s di scar ded.

Data: 0110111110110001011111100101000000 Framed Data: 0111111001101111100110001011111010010100000001111110

slide-7
SLIDE 7

Encodi ng Rul e V i

  • l

ati

  • n

Fr am i ng x 1 1 1

M an- chester Encodi ng Bi t str eam I n som e system s, the tr ansm i tter w i l l send a si gnal that vi

  • l

ates an encodi ng r ul e to si gnal the star t

  • f

a f r am e. Exam pl es:

1 X 1 1

A l ter nate M ar k- I nver si

  • n

A M I Bi t str eam

slide-8
SLIDE 8

Char acter

  • O r

i ented Fr am i ng

Som e char acter

  • r

i ented pr

  • tocol

s need to di vi de a str eam

  • f

char acter s (octets, bytes) i nto f r am es. Thr ee codes ar e used to bui l d f r am es w hi ch ar e desi gnated:

  • "Data

Li nk Escape"

  • r

DLE

  • "Star

t Tr ansm i ssi

  • n"
  • r

STX

  • "End

Tr ansm i ssi

  • n"
  • r

ETX The r ul es ar e:

  • Fr

am es ar e star ted w i th the tw o-

  • ctets:

DLE STX

  • Fr

am es ar e ended w i th the tw o

  • ctets:

DLE ETX Si nce al l 256 possi bl e 8- bi t codes can appear i n the data, w henever a DLE

  • ctet

appear s, a second DLE i s stuf f ed i nto the char acter str eam af ter i t.

Data: A B DLE C D STX F ETX G H Framed Data: DLE STX A B DLE DLE C D STX F ETX G H DLE ETX

slide-9
SLIDE 9

Char acter

  • O r

i ented Fr am e Decode Framed Data: DLE STX A B DLE DLE STX D E F ETX G H DLE ETX Data: A B DLE STX D E F ETX G H

Decodi ng r ul e: w henever a DLE char acter appear s i n the i ncom i ng char acter str eam , i t i s i nter pr eted i n com bi nati

  • n

w i th the next char acter accor di ng to thi s tabl e:

  • DLE

STX = Star t

  • f

Fr am e (di scar d, star t savi ng data)

  • DLE

DLE = Repl ace w i th si ngl e DLE

  • DLE

ETX = End

  • f

Fr am e (di scar d, pass data to hi gher l evel )

  • DLE

[anythi ng el se] = codi ng er r

  • r

.

slide-10
SLIDE 10

Scram bl ers Ther e ar e pr

  • bl

em s w hen l

  • ng

str i ngs

  • f
  • nl

y "0"s

  • r
  • nl

y "1"s ar e tr ansm i tted. To pr event thi s a scr am bl er can be used at the tr ansm i tter , and a m atchi ng descr am bl er at the r ecei ver . Scr am bl er : B(m ) = A (m ) ⊕ B(m - 3) ⊕ B(m - 5)

  • w her

e ⊕ i n the "excl usi ve

  • r

"

  • A (m )

i s the m ' th bi t i nput

  • B(m )

i s the m ' th bi t

  • utput.

Descr am bl er : C(m ) = B(m ) ⊕ B(m - 3) ⊕ B(m - 5)

  • B(m )

i s the m ' th bi t i nput

  • C(m )

i s the m ' th bi t

  • utput.

p. 147- 149

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SLIDE 11

Shi f t Regi ster Scr am bl er s

Scr am bl er : B(m ) = A (m ) ⊕ B(m - 3) ⊕ B(m - 5) Descr am bl er : C(m ) = B(m ) ⊕ B(m - 3) ⊕ B(m - 5)

A (m ) B(m )

C(m ) C(m ) = B(m ) ⊕ B(m - 3) ⊕ B(m - 5) C(m ) = {A (m ) ⊕ B(m - 3) ⊕ B(m - 5)} ⊕ B(m - 3) ⊕ B(m - 5) C(m ) = A (m ) si nce X ⊕ X = 0, Y ⊕ = Y

B(m - 3) B(m - 5) B(m - 1) B(m - 2) B(m - 4)