01CDMA Theory Unit Summary

7/25/2019 01CDMA Theory Unit Summary

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Copyright 2003, ZTE CORPORATION

Unit summary about CDMA theory


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I. CDMA

Overview


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Frequency

reuse factor is

1;

network design

and expandingbecome much

easier

Advantages of CDMA(1)AMPS, D-AMPS, N-AMPS

CDMA

30 300 !"#

$00 !"#

$%0 !"#

3 Users

& Users

$0 Users

$

3'

'

3$

%(

)

*y+ia re/ueny euse N1)

*y+ia re/ueny euse N1'

*y+ia re/ueny euse N1

2unerabiity

C4I ) 56

2unerabiity

C4I $-' 56

2unerabiity

7b4No(--) 56

8SM


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Large capacity:

8--10 times than AMPS46 times than GSM

.re/uen,

y

*ime

Power

.re/ue

n,y

*ime

Power

.re/

uen,y

*ime

Power

DMA

*DMA

CDMA

FDMA---Different user use different

frequency

TACS AMPS

TDMA---Different user use different

time slot of one frequency

GSM

DAMPS

CDMA---Different user use same

frequency at the same time,but with

different spreading code

Advantages of CDMA(2)


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large coverage

almost 2 times than GSM, save money for

operator

Example:cover 1000 km2

GSM need 200 BTS

CDMA only need 50 BTSAttention: exact result need Link Budget



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High privacy,hard to wiretapping

S+rea5 o5e

In9ormationsi:na

*;

Demo5uate5si:na

;

S+rea5 o5e

Spread signalEach user is belowthe noise deeply



7/38Copyright 2003, ZTE CORPORATION

CDMA make before break---soft handoffOther systems: make after break---hard handoff

CDMA make before break---soft handoffOther systems: make after break---hard handoff

Use soft handoff, decrease drop-call rate




Good voice quality, use 8k,13K(QCELP,EVRC)voice

codingthe best coding method in the world.

Voice quality(MOS)

6!PC"

#3!$%"

&!C'"A

#3!C'"A

&!EVRCC'"A




Perfect Power Control and voice activation make the MS

Power low, healthy for human bodygreen mobile phone.


Mean Power Max Power

GSM: 125mW 2W

CDMA: 2mW 200mW



II. CDMA

6ASIC PINCIP=7



Advantages of Spread Spectrum

Avoid interference arising from jamming signal or multi-

path effects

SS and demodulation, noise is suppressed and filtered

resist intercept and capture: difficult to detect

Achieve Privacy: Difficult to demodulate

Implement Multiple Access

Improve Freuency !euse "nlarge #apacity



Discriminating Among Forward

Code Channels

A Mobile Station receives a Forward Channel from a sector in aBase Station.

The Forward Channel carries a composite signal of up to 64 forwardcode channels.

Some code channels are traffic channels and others are overheadchannels.

A set of 64 mathematical codes is needed to differentiate the 64possible forward code channels.

The codes in this set are called Walsh Codes

SyncPilot

F$ %raffic&for user '()

Paging

F$ %raffic&for user '*)

F$ %raffic

&for user '+)



Discriminating Among Base

Station

A mobile Station is surrounded by Base Stations, all of them transmitting

on the same CDMA Frequency.

Each Sector in each Base Station is transmitting a Forward TrafficChannel containing up to 64 forward code channels.

A Mobile Station must be able to discriminate between different Sectorsof different Base Stations.

Two binary digit sequences called the I and Q Short PN Sequences (orShort PN Codes) are defined for the purpose of identifying sectors ofdifferent base stations.

These Short PN Sequences can be used in 512 different ways in a CDMAsystem. Each one of them constitutes a mathematical code which can be

used to identify a particular sector.

A

p to ./

#ode #hannels

p to ./

#ode #hannels



Discriminating Among Reverse

Code Channels The CDMA system must be able toidentify each Mobile Station that may

attempt to communicate with a BaseStation.

A very large number of Mobile Stationswill be in the market.

One binary digit sequence called theLong PN Sequence (or Long PN Code)is defined for the purpose of uniquelyidentifying each possible reverse codechannel.

This sequence is extremely long and

can be used in trillions of differentways. Each one of them constitutes amathematical code which can be used toidentify a particular user (and is thencalled a User Long Code) or a particularuser Reverse Traffic channel.

2 *ra99i9rom M.S.

>&3))3$00&2 *ra99i9rom M.S.

>$0000)30?on aess hanne >@



CDMA Spread Code Selection

ash Co5es

Short PNSe/uenes

=on: PNSe/uenes

*y+e o9Se/uene

Mutually0rthogonal

0rthogonal1ith itself atany time shiftvalue e2cept 3

near-orthogonalif shifted

S+eiaPro+erties

('

$

"owMany

./ chips(4(5,*33

sec6

+*,7.8chips*.-*4+ ms792 in *sec6

*/* chips/( days

=en:th

0rthogonalModulation

&information

carrier)

;uadratureSpreading&Sectors

DataScram?ling toavoid stringsof (=s or 3=s

orwar5 =in!untion



Information Stream

Speech

#oding

#hannel

#oding

Scram?le Spread

SpectrumModulation !F

transmit

#hannel

decoding

De-

scram?leDe-spread

SpectrumDe-

Modulation!F

receive

Information Stream

CDMA Communication Model

Speech

decoding



III. CDMA C"ANN7=

S*UC*U7AND MODU=A*ION



Upon completion of this lesson, the student will be able tomaster:

Objectives

-- *he 9orwar5 hanne in IS-



IS-95 CDMA Channels



Forward Channel Diagram

Convolutional

coder

Code

repeater

Group

interleaving

Convolutional

coder

Code

repeater

Group

interleaving

Short code

generator

Frequency

splitter

Frame quality

indicator

Coder tail

bit

Convolutional

coder

Code

repeater

Walsh 0 1.2288c!s

Walsh "2 1.2288c!s

#.8$s!s#.8$s!s2.#$s!s1.2$s!s

r%1!2& '%(

(.)$s!s

#.8$s!s

1(.2$s!s

(.)$s!s1(.2$s!s 1(.2$s!s

Walsh * 1.2288c!s

1(.2$s!s1.2288c!s

Group

interleaving

1(.2$s!s

(.)$s!s

#.8$s!s

2.#$s!s

r%1!2& '%(

(.)$s!s

#.8$s!s

2.#$s!s

1.2$s!s

(.)$s!s

#.8$s!s

2.#$s!s

1.2$s!s

(.)$s!s

#.8$s!s

2.#$s!s

1.2$s!s

(.2$s!s

#.#$s!s

2.0$s!s

0.8$s!s

ultiuse

1(.2$s!s

Frequency

splitter

1(.2$s!s

Frequency

splitter

+ong code

generator 1.2288c!s

800,-

Walsh n

1.2288c!s

*ilot Channel

all 0/

Sync Channel

*aging Channel

long code cloc$serm/ orard

traic channel

inormation bit

8.)$s!s

#.0$s!s

2.0$s!s

0.8$s!s

serm/ mas$ code

*oer control bit800,-

A

A

A

A

Forward Logic Channel

See ne3t page



4ase band

ilter

4ase band

ilter

5

6

7 7 t

6 t

cosct

sinct

7 path pilot *9 code

1.2288c!s

6 path pilot *9 code 1.2288c!s

S t

Forward Logic Channel


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Reverse Logic Channel

:ata

randomi-er

Frame quality

indicator

Coder tail

bit

Convolutional

coder

Code

repeater1(.2$s!s(.)$s!s#.8$s!s2.#$s!s

r%1!2& '%(

(.)$s!s#.8$s!s2.#$s!s1.2$s!s

(.2$s!s#.#$s!s2.0$s!s0.8$s!s

+ong code

generator

1.2288c!s

8.)$s!s#.0$s!s2.0$s!s0.8$s!s

Convolutionalcoder

Coderepeater

Groupinterleaving

Shortcode

generator

r%1!"& '%(

;rthogonalmodulator

Codertail bit

4ase band

ilter

4ase band

ilter

D

28.8$s!s28.8$s!s

4ase band

ilter

4ase band

ilter

D

Group

interleaving

;rthogonal

modulator

5ccess channelinormation bit88 bit per rame/

#.8$b!s#.#$b!s 1#.#$s!s

)# scale/

Walsh

sub code

#.8$s!s%"0


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Cdma2000 1xRTT Channel


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Channel List: 1xRTT vs. IS-95@ IS-59 ?uilt on the IS-59A channels, and introduced t1o ne1 channels

Fundamental channel 1as the same as IS-5A traffic channel Supplemental code channels assigned to support rates a?ove

(/6/B?ps

@ IS-*333 (2!%% continue to ?uild on the IS-59 channels IS-59 channels continue to ?e supported in IS-*333 to support IS-59

mo?iles

Piot hanne

Syn hanne

Pa:in: hanne Aess hanne

orwar5 *ra99i Channe everse *ra99i Channe

un5amenta hanne un5amenta hanne

Su++ementa Co5e hanne ?-SCC"@ Su++ementa Co5e hanne ?-SCC"@

Su++ementa hanne ?-SC"@ Su++ementa hanne ?-SC"@

ui! Pa:in: hanne ?-PC"@ everse Piot hanne ?-PIC"@

IS-


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For1ard ;uicC Paging #hannel&F-;P#)For1ard Supplemental #hannel&F-S#)

!everse Pilot #hannel

!everse Supplement #hannel&!-S#)

Additional Channel in 1X

Commercial System


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Benefits of the CDMA2000 1x

Increased MS stand?y ?attery life &via ;uicC Paging#hannel)

se For1ard ;uicC Po1er #ontrol&via !everse Pilot

channel) %otal ?acC1ard compati?ility to reuse s1itch and call

processing features

*-+ d ?etter coverage

Provides igh speed (9+6. C?ps pacCet data capa?ilities


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I2. CDMA

E7F *7C"NO=O8F


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Contents

/6( Po1er #ontrol In #DMA

/6* Soft andoff In #DMA


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Why Power Control? All CDMA users occupy the same frequency

at the same time! Frequency and time arenot used as discriminators.

CDMA operates by using CODES todiscriminate between users.

CDMA interference comes mainly fromnearby users

Each user is a small voice in a roaring crowd-- but with a uniquely recoverable code.

Transmit power on all users must betightly controlled so their signals reach

the base station at the same signal leveland at the absolute minimum power levelnecessary to ensure acceptable servicequality

i:ure o9 Merit 74Io, 7b4No

?ener:y +er hi+ GbitH 4

inter9erene GnoiseH s+etra 5ensity@

CDMA 74Io-) to -$ 56

CDMA 7b4No(to) 56

i:ure o9 Merit 74Io, 7b4No

?ener:y +er hi+ GbitH 4

inter9erene GnoiseH s+etra 5ensity@

CDMA 74Io-) to -$ 56

CDMA 7b4No(to) 56


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Goals of the Power Control- To maintain the transmit power at no higher than the demand.

Each user doesn't get any more than the minimum Eb/ Io, to make

the smallest contribution to the total noises seen by other users as

possible.

Effective power control maximise the capacity of the system.

- To reduce the effect of fading.

- To solve the near-far effect.

?


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Power Control Types

Reverse Power Control

;pen=loop *oer Control

Closed=loop *oer Control(Forward traffic Channel)

Outer-loop Power Control

Inner-loop Power Control

Forward Power Control

6S=(@ *oer Control

6S=2000 Fast *oer Control >everse *ilot Channel/

Outer-loop Power Control

Inner-loop Power Control


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Summary of Power Control

All types of po1er control 1orC together to minimiEes po1er consumption

at the mo?ile stations, and increases the overall capacity of the system

transmit po1er6

F"! F"!

Mobie 6*S 6SC

Si:na Stren:th

Measurement

Set+oint

or

A5Just w5.

+ower

everse Outer

=oo+ Power

Contro

everse Cose5 =oo+

Power Contro

orwar5 =in! Power Contro

everse O+en =oo+

Power Contro


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Contents

/6( Po1er #ontrol In #DMA

/6* Soft andoff In #DMA


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Handoff

andoff is the process ?y 1hich a mo?ile station maintainscommunications 1ith the Mo?ile %elephone S1itching

center&MS#), 1hen traveling from the coverage area of one

?ase station to that of another

andoff Ceep the call esta?lished during the follo1ingconditions:

Su?scri?er crosses the ?oundaries of a cell

Su?scri?er e2periences noise or other interference

a?ove a specified thresholdA ?ase station component e2periences an out-of-service

condition during a call


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CDMA Handoffs

Durin:a Ca

I5e "an5o99

So9t "an5o99

So9ter "an5o99

CDMA-to-CDMA "an5o99

Inter-System So9t "an5o99

CDMA-to-Anao: "an5o99

hie in the

I5e State


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Different types of handoffSC

4SC 4AS SBC

;C;:

. CB C5>. AD*B hando/

S SS D S D S Soter

S S S : S : D ,al sot

S S D : S :S

Sot

S S : : D : D ,ard

S D : : S : S Sot

S: : : D : S ,ard

01CDMA Theory Unit Summary

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