1 Selected Topics in Telecommunication Engineering I

504460

15 2558 .

FDMA/TDMA/CDMA/SDMA

FDMA/TDMA CDMA

FDMA/TDMA CDMA

2

FDMA

TDMA ( 3 ) 20

CDMA

SDMA -

3

Definitions FDMA Frequency Division Multiple Access

TDMA Time Division Multiple Access

CDMA Code Division Multiple Access

4

FDMA

5

FDMA Used in analog cellular phone systems (i.e. AMPS)

Uses Frequency Division Duplexing (FDD)

DQPSK modulation scheme

Used in analog cellular phone systems (i.e. AMPS)

6

Number of FDMA Channels

7

2

- total spectrum

- guard band

- channel bandwidth

f guard

c

f

guard

c

N

=

In the U.S. each cellular carrier is allocated 416 channels where:

8

12.5

10

3012.5 2 10 416

30

f

guard

c

MHzkHz

kHzMHz kHzN

kHz

=

=

=

= =

FDMA ()

bit rate digital code

9

FDMA guard bands

RF filter

10

FDMA

11

FDMA

12

OFDM

!

!

FET (Time domain to frequency domain)

13

OFDM

!

!

!

4 FFT

14

OFDM FDMA

OFDM 50%15

OFDM

16

OFDM

17

OFDM

18

guard band

19

PAPR (Peak to Average power ratio)

20

SC-FDMA

21

SC-OFDM PARR (Peak to Average power

ratio) OFDM

22

23

TDMA Used in Digital AMPS

DQPSK modulation scheme

Uses Time Division Duplexing (TDD)

24

TDMA

25

TDMA

26

TDMA

27

- overhead bits per frame - number of reference bursts per frame - number of traffic bursts per frame

- number of overhead bits per reference burst - number of overhead bits per preamble p

OH

r

t

r

p

bNNbb

( )

er slot

- number of equivalent bits in each guard time interval

- frame duration

- bit rate of the radio-frequency channel

1 100%

g

f

rf

OH r r t p t r g

total f rf

OHf

total

bTR

b N b N b N N bb T R

bb

=

=

$ %= & '( )

TDMA Classical Aloha

Slotted Aloha ( Time Synchronized)

CSMA/CA

28

TDMA Bit rate frequency guard band narrowband hands off

29

TDMA

DSP

uplink

Multipath

30

CDMA CDMA

31

CDMA

32

CDMA

(Frequency Hopping Sperad Spectrum: FHSS)

(Direct Sequency Sprectrum: DSSS)

33

DSSS

34

DSSS!

DSSS

35

DSSS

Jamming

36

FHSS

37

FHSS FHSS a

b

38

FHSS

jamming

39

FHSS

FHSS (Channel assignment) (Channel use)

Synchornization

40

41

SDMA SDMA

MIMO SDMA Adhoc RFID

42

SDMA

43

44

45