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CONTENTS

MULTIPLE ACCESS

CDMA SPECTRUM

CDMA CODES CDMA CHANNELS

CDMA CALL PROCESSING

CDMA PERFOMANCE INDICATORS HARD HANDOFF

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MULTIPLE ACCESS

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PROCESSING GAIN

Chip Rate (Rc): The Chip Rate is the rate at which the PN sequence is generated. For

CDMA, IS95, the chip rate is 1.2288 * 10 ^ 6 cps (chips per second).

Bit Rate (Rb): The bit rate is base band user information (i.e. user voice/data) rate. In

CDMA, voice is digitized at different rates depending on the speech activity level. Thesystem parameters presented in this discussion are based on a maximum bite rate of 9.6

kbps and 14.4 kbps per IS95

For CDMA (IS95A/B):

Ex.Rc = 1.2288 Mcps, Rb = 14.4 kbps (max), resulting in a Processing Gain of 85.33 (19.3

dB).

Processing Gain is a term common to all direct sequence spread spectrum

systems.

Process gain is defined as the ratio of the Chip Rate (Rc) to theinformation bit rate (Rb).

This provides a measure of ``spreading'' in the system.

Processing Gain = Rc / Rb

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SOFT CAPACITY IN CDMA

YOU CAN ALWAYS ADD JUST ONE MORE CALLER TO A CDMACHANNEL AT THE COST OF QUALITY. CDMA SYSTEM CAPACITY IS

A COMPROMISE BETWEEN THE NUMBER OF USERS AND QUALITY

OF SERVICE.

CDMA

USERS

USER

TRAFFICQUALITY

TOTAL

BANDWIDTH

QUALITY IS ANALOGOUS TO PROCESSING GAIN

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CDMA SPECTRUM

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CDMA Cellular Spectrum

846.5MHz

825MHz

824

MHz

835

MHz

845

MHz

849

MHz

A A AB B Reverse link

891.5MHz

870MHz

869MHz

880MHz

890MHz

894MHz

A A AB B Forward link

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CDMA UP LINK DOWN LINK BANDSEPERATION

1.23MHz 1.23MHz

ReverseCDMA Channel

ForwardCDMA Channel

45 MHzFrequencyCDMA

ChannelFrequency

836.68 MHz881.68 MHz

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CDMA ADJACENT CHANNELS

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Spreading : What We Do, We Can Undo

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U1 = 0110010101001000

C1 ( 100110.10110010)*

=U1C1 ( 1001100000)

U1C1 ( 10011000000)

U1 = 0110010101001000

C1 ( 100110.10110010)*

=

UnCn

U4C4

U3C3

U2C2

UnCn*C1 = 0, UnCn*Cn = Un

U4C4*C1 = 0, U4C4*C4 = U4

U3C3*C1 = 0, U3C3*C3 = U3

U2C2*C1 = 0, U2*C2*C2 = U2

C1*C1 = 1, C2*C2 = 1. Cn*Cn = 1 BUT C1*C2 = 0C1*Cn = 0

DSSS Spreading/ Despreading

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CDMA CODES

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CODES IN CDMA

WALSH CODES O th l

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WALSH CODES-OrthogonalSequences

Definition:

Orthogonal functions have zero correlation. Two binary sequencesare orthogonal if the process of XORing them results in an equal

number of 1s and 0s. Example:0000

(XOR) 0101

------0101

Generation Sequence:

- Seed 0 0

0 1- Repeat: right & below

- Invert: diagonally

0 0

0 1

0 0

0 1

0 0

0 1

1 1

1 0

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Walsh Codes

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 1

0 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 00 1 0 10 0 1 10 1 1 0

0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 6 6 6 60 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 30

00

0

0000

0001111

11111

2222

222

222336666

012

3

4567

8901

234

5

678

90123

456

78901...0123

ORTHOGONALITY OF WALSH CODES

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ORTHOGONALITY OF WALSH CODES

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Orthogonal Spreading

1

0110011010011001100110010110011010011001011001100110011010011001

1001100101100110011001101001100101100110100110011001100101100110

Walsh Function #59

Pattern to be Transmitted

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Orthogonal Spreading

0

0 1 1 0

0

0 1 1 0

1

0 1 1 0

1

0 1 1 0

1

0 1 1 0

1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1

+1

-1

+1

-1

User Data

OrthogonalSequence

Tx Data

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Decoding Using a Correct Code

0

0 1 1 0

0

0 1 1 0

1

0 1 1 0

1

0 1 1 0

1

0 1 1 0

1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1

+1

-1

CorrectFunction

Rx Data

0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 11 1 1 1

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?

0 1 0 1

?

0 1 0 1

?

0 1 0 1

?

0 1 0 1

?

0 1 0 1

1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1

IncorrectFunction

Rx Data

0 0 1 1 0 0 1 1 1 1 0 0 1 1 0 01 1 0 0

Decoding Using a Incorrect Code

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Example: Spreading

+1

-1

+1

-1

+1

-1

+1

-3

Spread Waveform Representation ofUser As signal

Analog Signal Formed by the Summationof the Three Spread Signals

Spread Waveform Representation ofUser Cs signal

Spread Waveform Representation ofUser Bs signal

A=00

Walsh Code forA = 0101

B=10

Walsh Code forB = 0011

C=11

Walsh Code forC = 0000

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Despreading

Received Composite Signal

Walsh Code for User A = 0101

Product

+1

-3

+1

-1

+3

-1

Average=(5-1)/4=1 Average=(5-1)/4=1

0 0

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PN Code Generation

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PN Code Generation

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Masking

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Lookup Table for PN Offsets

Mask

001

010

011

100

101

110

111

Offset (in chips)

7

6

4

5

1

3

2

Transmitted Sequence

1001011

0010111

1011100

0101110

1100101

0111001

1110010

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Quadrature Spreading

To BasebandFilter

I

Q

1011000010110

0100011101011

0110111001011

Symbols Spread byWalsh Chips

0110111001011

0110111001011 1101111011101

0010100100000

Offset I PN Code

Offset Q PN Code

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Phase Shift Keying (PSK)

-sinwct(logic 0)

sinwct(logic 1)

1

0

1

DigitalSignal

Bipolar PSK Quadrature PSK

00

0111

10

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Orthogonal QPSK

I-ChannelInput Data

tb

b0 b1 b2 b3 b4

Q-Channel

Input Data

tb

a0

a1

a2

a3

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QPSK MODULATION USING PN-SHORT CODE

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PN Offset - Cell Identification

Quick and Easy Cell Acquisition Reuse Walsh Codes

100101001100111010111001010100

100101001100111010111001010100

1001010011001110101110010Offset inincrementsof 64 chips

#1

#2

#3

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FORWARD & REVERSE LINK CODES

C h / N C h

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Coherent / Non-CoherentDetection

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CDMA CHANNELS

The CDMA Physical

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The CDMA PhysicalLayer

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Physical Channel

Physical channels are described in terms of a wideband

RF channel and code sequence. As defined in IS95, each

RF channel is 1.2288 MHz wide. For each RF channel,

there are 64 Walsh sequences (W0 through W63)available for use on the forward link. These Walsh

sequences are commonly referred to as CDMA code

channels.

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The physical channel that carry specific types of information are

known as logical channels. Logical channels in CDMA are divided

into two categories: Traffic Channels and Control Channels. For

the forward link there are three types of Control/Signaling channels

and one Traffic Channel (per user). For the Reverse Link there isone type Signaling Channel and one Traffic Channel per user.

It is important to note that signals on the forward link are identified

by Walsh codes, however, signals on the reverse link are identified

by Long Codes.

Logical Channel

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Transmitting a spread spectrum signal involves:

1. Modulating the information signal with the spreading PN

sequence

2. Modulating the resulting signal with the desired carrier wave

3. Band Pass Filtering the output

4. Transmitting the resulting RF signal.

Receiving a spread spectrum signal involves:

1. Demodulating the signal with the RF carrier,

2. Low Pass Filtering the resulting wide band signal,

3. Demodulating with the signal with the known spreading

sequence, and

4. Integrating the despread signal over a bit time to recover the

information signal

Transmit and Receive Processes of SpreadSpectrum

C A S 9 C A S

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Four RF

CDMA IS-95 CHANNELS

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AIR INTERFACE

Control Channels

Downlink Uplink

Pilot Sync Paging Access

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AIR INTERFACE

TRAFFIC CHANNELS

SPEECH or DATA ASSOCIATED SIGNALLING

1 1/2 1/4 1/8 Blank &

Burst Dim &

Burst

Power

Control

Forward Link (Downlink)

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o a d ( o )

The logical channels for the Forward Link must provide identification

of the Base station, timing and synchronization of the transmissions

between the base station and mobile station, paging of mobile units in

the area, and the voice/data transmission from the base station to the

mobile unit. The forward link is comprised of:

The Pilot Channel,

Up to one Sync Channel,

Up to seven Paging Channels, andUp to 55 Traffic Channels

A Power Control SubChannel is continuously transmitted on the

forward traffic channel as part of the traffic frame. Information on this

channel commands the mobile unit to adjust its transmitted power + 1

dB every 1/16 of a speech frame (800 times per second).

Power Control SubChannel

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Reverse Link (Uplink)

The logical channel requirements of the reverse link must provide forthe identification and access request by the mobile unit to the base

stations in the area and the voice/data transmission from the mobile

unit to the base station. The reverse link is composed of:

Access Channels and

Traffic Channels.

These channels share the same CDMA center frequency on the reverse

link (a different frequency is used for forward link transmissions). The

total number of channels( max 55) is determined by base station

activity. .. The reverse link capability of a given base station is limited

by the number of traffic channels assigned (up to 55) and up to seven(7) access channels (correlating to a maximum of 7 paging channels).

Note that a mobile does not ``tie up'' an access channel, it only

borrows it for a short amount of time.

Pilot and Sync and Paging Channels

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The Pilot Channel allows a mobile station to acquire the timing of the

Forward Traffic Channel user information. It provides a phase reference

for coherent demodulation and provides a means for signal strengthcomparisons between base stations, which is used to determine when to

handoff. It consists of the un-modulated spreading sequences (PN short

codes). The Pilot signal is transmitted continuously on Walsh 0 by each

CDMA base station at the transmitter (cell/sector) level.

Pilot Channel

Sync Channel

The Synchronization Channel is an encoded, interleaved and modulated

spread spectrum signal that is used with the Pilot Channel to acquire initial

system time and synchronization. The sync channel is always transmitted

on Walsh 32.

The Paging Channel is used for transmission of control information to the mobile. When a

mobile is to receive a call it will receive a ``page'' from the base station. Up to seven (7)

channels may be configured for paging depending on the expected demand. Page channel

messaging to each user takes place in an 80 ms ``slot''. The 80 ms slots are grouped into

cycles of 2048 slots (cycle duration 163.84 s) referred to as maximum slot cycles. The base

station can limit the maximum slot cycle used by the mobile.

Paging Channel

Access and Traffic Channels

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Access and Traffic Channels

Access Channel

The Access Channel is used for the transmission of control information to the

base station. When a mobile is to place a call it uses the ``access'' channel toinform the base station. This channel is also used when responding to a ``page''.

Each Access Channel is identified by a distinct ``Access Channel Long PN Code

''. An Access Channel is selected randomly by the mobile unit from the total

number of access channels available from the serving cell/sector.

Traffic ChannelThe Traffic Channel carries all the calls (voice or data signal) from a given base station to

all the mobile units active in the coverage area or vice versa. Each user has a dedicated

TCH, and corresponding Walsh code, on the down link.

The forward traffic channel message consists of user voice (or data), power control data,

and error correction bits. The message is transmitted as a series of traffic frames. Thetraffic channel may also carry signaling information with or in place of user voice (or

data). A Walsh code is assigned by the base station for each Traffic Channel in use.

The Traffic Channel for the reverse link is identical to the forward link Traffic Channel

in function and structure. Each traffic channel is identified by a ``User Long PN Code''

which is unique to each CDMA user.

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Variable Low Bit Rate

Speech Coding

Convolution

encoding

Bit Interleaving

Encryption:Long Code

Scrambling

Quadrature

Carrier

Modulation

RF

Channel

Walsh Function

Modulation

Quadrature

Spreading and

Multiplexing

Variable Low Bit Rate

Speech Decoding

Channel Decoding

Bit Deinterleaving

Decryption: Long

Code Descrambling

Quadrature Carrier

Demodulation

Walsh Function

Demodulation

Quadrature

Despreading

CDMA Forward Link

Transmit Pathin Base Station

Receive path

in Mobile

INTERLEAVING IN FEC

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C

C

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Variable Low Bit Rate

Speech Coding

Concolution Encoding

Bit Interleaving

64ary Orthogonal

Walsh Symbol

Modulation

Quadrature

Carrier

Modulation

RF

Channel

Encryption: Long

Code Spreading

QuadratureSpreading

Variable Low Bit Rate

Speech Decoding

Channel Decoding

Bit Deinterleaving

64ary Orthogonal Walsh

Symbol Demodulation

Quadrature Carrier

Demodulation

Decryption: Long

Code Despreading

Demultiplexing andQuadrature

Despreading

Transmit Path

in Mobile

Receive path in

Base Station

CDMA Reverse Link

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Forward Link Code Channels

Pilot Channel

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Pilot Channel

26.67 ms frame period, repeated 75 times a second.

Pilot channels are kept at 4-6 dB higher then rest of the channels

BB

BB

All 0s

Walsh W0

1.2288 Mcps

I Pilot PN sequence1.2288 Mcps

Q Pilot PN sequence1.2288 Mcps

To QPSKModulator

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Sync Channel Frames

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Sync Channel Frames

Convolutional encoder not zeroed out after each frame

No CRC bits at frame level, SOM (Start Of Message)

SOM 31 Information Bits

32 bits / 26.67 ms

BB

BB

Sync ChannelMessage Walsh W32

1.2288Mcps

I Pilot PN sequence1.2288 Mcps

Q Pilot PN sequence1.2288 Mcps

To QPSKModulator

ConvolutionalEncoderRate=1/2,

SymbolRepetition

1.2Kbps

2.4Ksps

BlockInter-leaver19.2

Ksps

19.2Ksps

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Paging Channel

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Paging Channel

BB

BB

Paging ChannelMessage

Walsh W1-7

1.2288Mcps

I Pilot PN

1.2288 Mcps

Q Pilot PN1.2288 Mcps

To QPSKModulator

ConvolutionalEncoderRate=1/2,

SymbolRepetition

4.8/9.6Kbps

9.6/19.2Ksps

BlockInter-leaver19.2

Ksps

19.2Ksps

Long CodeDecimator

Long CodeGenerator

1.2288Mcps

64:1Long-code MaskforPaging Channel

Forward Traffic Channel

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Forward Traffic Channel

BB

Walsh Wn

1.2288Mcps

I Pilot PN1.2288 Mcps

Q Pilot PN

1.2288 Mcps

To QPSKModulator

ConvolutionalEncoderRate=1/2,

SymbolRepetition

BlockInter-

leaver 19.2Ksps

DecimatorLong Code

Generator 1.2288Mcps

64:1Long-codeMask

Decimator

Mux

24:1

Power Control

Bits (800bps)

BB

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Reverse Link Code Channels

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Access Channel Frames

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Access Channel Frames

Tail Bits Zero Convolutional Encoder, No CRC Bits At Frame Level

Preamble Comprised of Zero Filled Frames

88 Information Bits 8 TailBits

20 ms

BB

BB

Access ChannelMessage

1.2288Mcps

I Pilot PN

1.2288 Mcps

Q Pilot PN1.2288 Mcps

To QPSKModulator

ConvolutionalEncoderRate=1/3, K=9

SymbolRepetition

4.8/9.6Kbps

14.4Ksps

BlockInter-leaver28.8

Ksps

64-aryOrthogonalModulator

Long CodeGenerator

1.2288 McpsLong-codeMask

Reverse Traffic Channel

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Reverse Traffic Channel

BB

BB

1.2288

Mcps

I Pilot PN1.2288 Mcps

Q Pilot PN1.2288 Mcps

To QPSK

Modulator

ConvolutionalEncoderRate=1/3, K=9

SymbolRepetition

RS1/RS2

Block

Inter-leaver28.8

Ksps

64-ary

OrthogonalModulator

Long Code

Generator

1.2288McpsLong-code

Mask

Data

BurstRandomizer

28.8Ksps

4.8Ksps

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Summary ofCodes

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The Long Code is a PN sequence that is 2^42 1 bits (chips) long. It is generated at a rate

of 1.2288 Mbps (or Mcps) giving it a period (time before the sequence repeats) ofapproximately 41.4 days. The long code is used to encrypt user information. Both the base

station and the mobile unit have knowledge of this sequence at any given instant in time

based on a specified private ``long code mask'' that is exchanged.

PN Long Code

The Short Code is a PN sequence that is 2 ^ 15 bits (chips) in length. This code isgenerated at 1.2288 Mbps (or Mcps) giving a period of 26.67 ms. This code is used for final

spreading of the signal and is transmitted as a reference known as the ``Pilot Sequence''

by the base station. All base stations use the same short code. Base stations are

differentiated from one another by transmitting the PN short code at different ``offsets'' in

absolute.

PN Short Code

CDMA defines a group of 64 orthogonal sequences, each 64 bits long, known as Walsh

Codes. These sequences are also referred to as Wash Functions. These codes are generated

at 1.2288 Mbps (Mcps) with a period of approximately 52 s. These are used to identify

users on the forward link. For this reason they are also referred to as either Walsh

Channels or TCH. All base stations and mobile users have knowledge of all Walsh codes.

Walsh Codes

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