cdma rf zte rakesh tripathi

CDMA Technology

FREQUENCY BANDS

DirectionGSM-900

Extended GSM

DCS 1800 PCS 1900

MHZ MHZ MHZ MHZUplink 890-915 880-915 1710-1785 1850-1910

Downlink 935-960 925-960 1805-1880 1930-1990

Direction Band Class-0 Band class-1Band class-

4Bans class-10

MHZ MHZ MHZ MHZUplink 824-849 1850-1910 1750-1780 806-824

Downlink 869-894 1930-1990 1840-1870 896-901

World wide GSM bands

World wide CDMA 2000 bands

CDMA Frequency Calculation：

450MHzBS receiver(Uplink): 450.00+0.025(N-1) BS sender(downlink): 460.00+0.025(N-1)

800MHzBS receiver(Uplink): 825.00+0.03NBS sender(downlink):870.00+0.03N

1900MHzBS receiver(Uplink): 1850.00+0.05NBS sender(downlink):1930.00+0.05N

• FDMA Frequency Division Multiple Access– Each user on a different frequency– A channel is a frequency

• TDMA Time Division Multiple Access– Each user on a different window period in

time (“time slot”)– A channel is a specific time slot on a

specific frequency

• CDMA Code Division Multiple Access– A channel is a unique code pattern– Each user uses the same frequency all the

time, but mixed with different distinguishing code patterns

FrequencyTime

Channel: An individually-assigned, dedicated pathway through a transmission medium for one user’s information.

The transmission medium is a resource that can be subdivided into individual channels according to the technology used.

Defining Our some Terms• CDMA Channel or CDMA Carrier or CDMA Frequency

– Duplex channel made of two 1.25 MHz-wide bands of electromagnetic spectrum, one for Base Station to Mobile Station communication (called the FORWARD LINK or the DOWNLINK) and another for Mobile Station to Base Station communication (called the REVERSE LINK or the UPLINK)

– In 800 Cellular these two simplex 1.25 MHz bands are 45 MHz apart

– In 1900 MHz PCS they are 80 MHz apart

• CDMA Forward Channel

– 1.25 MHz Forward Link

• CDMA Reverse Channel

– 1.25 MHz Reverse Link

• CDMA Code Channel

– Each individual stream of 0’s and 1’s contained in either the CDMA Forward Channel or in the CDMA Reverse Channel

– Code Channels are characterized (made unique) by mathematical codes

– Code channels in the forward link: Pilot, Sync, Paging and Forward Traffic channels

– Code channels in the reverse link: Access and Reverse Traffic channels

45 or 80 MHz

CDMA CHANNELCDMA

ReverseChannel 1.25 MHz

CDMAForwardChannel 1.25 MHz

Definition of Some Terms (1)• Channel

– Duplex channel made of two 1.2288MHz-wide bands of electromagnetic spectrum:

one for Base Station to Mobile Station communication (called the FORWARD LINK or the DOWNLINK) and another for Mobile Station to Base Station communication (called the REVERSE LINK or the UPLINK)

• Carrier or Frequency– In 800 MHz Cellular these two duplex 1.25 MHz bands are 45 MHz apart– In 1900 MHz PCS they are 80 MHz apart– In 450MHz,they are 10MHz apart

45 or 80 or 10 MHz

CDMA CHANNELCDMA

ReverseChannel 1.25 MHz

CDMAForwardChannel 1.25 MHz

Walsh code

CDMA Spread Code Selection

Walsh Codes

Short PN Sequences

Long PNSequences

Type of Sequence

Mutually Orthogonal

Orthogonal with itself at any time shift value except 0

near-orthogonal if shifted

Special Properties

How Many

64 chips1/19,200

32,768 chips26-2/3 ms75x in 2 sec.

242 chips~41 days

Length

Orthogonal Modulation(information

carrier)

Quadrature Spreading (Zero offset)

Distinguish

Reverse Link Function

User identitywithin cell’s signal

Distinguish Cells & Sectors

Data Scrambling to avoid strings of 1’s or 0’s

Forward Link Function

Information Stream

SpeechCoding

ChannelCoding

Scramble SpreadSpectrum

Modulation RFtransmit

Channeldecoding

De-scramble

De-spreadSpectrum

De-Modulation

RFreceive

Information Stream

CDMA Communication Model

Speechdecoding

Advantage of CDMA

Frequency reuse factor is 1;network design and expanding become much easier

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

30 30 10 kHz

200 kHz

1250 kHz

1 3 1 Users

8 Users

20 Users1

Typical Frequency Reuse N=7

Vulnerability:C/I 17 dB

Vulnerability:C/I 12-14 dB

Vulnerability:Eb/No 6--7 dB

Large capacity:8--10 times than AMPS4—6 times than GSM

FrequencyTime

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)

large coveragealmost 2 times than GSM, save money for operator

Example:cover 1000 km2 ： GSM need 200 BTS CDMA only need 50 BTS Attention: exact result need “Link Budget ”

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

Use soft handoff, decrease drop-call rateUse soft handoff, decrease drop-call rate

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

the best coding method in the world.

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

the best coding method in the world.

Voice quality(MOS)

64kPCM

13kGSM

8kCDMA

13kCDMA

8kEVRCCDMA

64kPCM

13kGSM

8kCDMA

13CDMA

Perfect Power Control and voice activation make the MS

Power low, healthy for human body—green mobile phone.

Perfect Power Control and voice activation make the MS

Power low, healthy for human body—green mobile phone.

Technology Mean Power Max Power

GSM: 125mW 2W

CDMA: 2mW 200mW

Technology Mean Power Max Power

GSM: 125mW 2W

CDMA: 2mW 200mW

95A 95B Software update Replace MS to

get new service

95B 1X Add 1X channel

board Software update Replace MS to ge

new service

1X 1XEV Add 1XEV

channel board Software update Replace MS to

get new service

inexpesive

TechnicalScheme ：

Smooth migration to 3G and the operator’s benefit is protected at the most

Almost free inexpensiveEconomicScheme ：

CDMA Channels

Sync Channel MessagePILOT_PN(Pilot PN Sequence Offset Index)

Set to the pilot PN offset for the base station (in units of 64 chips), assigned by the network planner

LC_STATE ( Long Code State )Provides the mobile station with the base station long code state at the time given by the SYS_TIME field, generated dynamically

SYS_TIME (System Time )GPS system-wide time as 320 ms after the end of the last super-frame containing any part of this message, minus the pilot PN offset, in units of 80 ms, generated dynamically

PRAT (Paging Channel Data Rate ) The data rate of the paging channel for this system, determined by the network planner,00 if 9600 bps;01 if 4800 bps

Paging Channel Overhead Messages

Mobile-Station-Directed Messages

OverheadMessages

Access Parameters MessageAccess Parameters Message

System Parameters MessageSystem Parameters Message

CDMA Channel List MessageCDMA Channel List Message

Extended System Parameters MessageExtended System Parameters Message

Extended Neighbor List MessageExtended Neighbor List Message

ConfigurationParameterMessages

Global Service Redirection MessageGlobal Service Redirection Message

PagingMessages

ACC_MSG_SEQ

CONFIG_MSG_SEQ

Forward Traffic Channels

• Used for the transmission of user and signaling information to a specific mobile station during a call.

• Maximum number of traffic channels: 64 minus one Pilot channel, one Sync channel, and 1 Paging channel.– This leaves each CDMA frequency with at least 55 traffic channels.– Unused paging channels can provide up to 6 additional channels.

Forward Traffic Channel

Paging

Forward Traffic Channel

CDMA Cell Site

9600 bps4800 bps2400 bps1200 bps

28.8ksps

R=1/3,K=9

1.2288McpsUser AddressMask

LongPN Code

Generator

28.8ksps Orthogonal

Modulation

Data BurstRandomizer

307.2kcps

1.2288Mcps

Q PN(no offset)

I PN(no offset)

1/2 PNChipDelay

Direct Sequence Spreading

ConvolutionalEncoder &Repetition

BlockInterleaver

Reverse Traffic Channel Generation

Uses Rate 1/3 Convolutional Encoder Uses 32*18 block interleaving array 64-ary Orthogonal Modulation Data burst randomizing

CDMA Channels Description

Power On Mobile

Sync Channel

Paging Channel

Handoff in CDMA

Handoff Handoff is the process by which a mobile station maintains

communications with the Mobile Telephone Switching center(MSC), when traveling from the coverage area of one base station to that of another

Handoff keep the call established during the following conditions:– Subscriber crosses the boundaries of a cell– Subscriber experiences noise or other interference

above a specified threshold– A base station component experiences an out-of-service

condition during a call

Types of CDMA Handoff

Duringa Call

Idle Handoff

Soft Handoff

Softer Handoff

CDMA-to-CDMA Handoff

Inter-System Soft Handoff

CDMA-to-Analog Handoff

While in the Idle State

CDMA Idle Handoff

PN 104

PN 108

Paging Channel M

Sync Channel M

104 108

Idle handoff neither soft handoff nor hard handoff.

CDMA Idle Handoff(Cont.)

PN 104

PN 108

Paging Channel M

Sync Channel M

sg104 108

Ec/Io>3dB

CDMA Soft Handoff

Soft Handoff:The mobile station starts communications with a target base station without interrupting communications with the current serving base station– Make-before-break– Directed by the mobile not the base station,Undetectable by user– Improves call quality

Can involve up to three cells simultaneously and use all signals– Mobile station combines the frames from each cell

Cell SiteB

Cell SiteA

Cell SiteB

CDMA Soft Handoff Mechanics

CDMA soft handoff is driven by the handset Handset continuously checks available pilots Handset tells system pilots it currently sees System assigns sectors (up to 6 max.), tells handset Handset assigns its fingers accordingly

Each end of the link chooses what works best, on a frame-by-frame basis Users are totally unaware of handoff

Pilot Strength Measurement Message

The Pilot Strength Measurement Message is used by the mobile station

to direct the Base Station Controller(BSC) in the handoff process.This

message uses in the Reverse Traffic Channel

A PSMM is sent to the system under one of the following conditions:

If MS finds a pilot in Neighbor or Remaining sets exceeds T_ADD

If an active set pilot drops below T_DROP after T_TDROP time

If a Candidate pilot exceeds an active pilot by T_COMP

Pilot Channel

Timing

Traffic Channels

CDMA Softer Handoff Softer Handoff is between sectors of

the same cell,that means multiple sectors of one BTS simultaneously serve a handset

Softer handoff occurs in BTS in a single channel element

Communications are maintained across both sectors until the mobile station transition has completed

MSC is aware but does not participate All activities are managed by the cell

site Signals received at both sectors can

be combined for improved quality

CDMA-to-CDMA Hard Handoff

Between cells operating on different frequencies Between cells that could be on the same frequency, but which are

subordinated to different MSC

A(ƒ1)

B(ƒ2)

T1 or E1 LinksTIA/EIA-41D

Why Power Control

CDMA is an interference-limited system based on the number of users,

the interference comes mainly from nearby users

each user is a noise source on the shared channel,this creates a

practical limit to how many users a system will sustain,so CDMA

also called soft capacity limit

The goal is to keep each MS at the absolute minimum power level

necessary to ensure acceptable service quality

Ideally the power received at the base station from each mobile

station should be the same(minimum signal to interference)

MS which transmit excessive power increase interference to other

Mobile station

Power Control Types

Reverse Power ControlOpen-loop Power Control

Closed-loop Power Control (Forward traffic Channel)Outer-loop Power ControlInner-loop Power Control

Forward Power ControlIS-95 Power Control

IS-2000 Fast Power Control (Reverse Pilot Channel)Outer-loop Power ControlInner-loop Power Control

Reverse Open-loop Power Control

Reverse open loop power is mobile station controlling its transmit power Reverse open loop power control consists of :

estimating how strong the mobile station should transmit based on a coarse measurement of how much power it is receiving from the base station

some correcting parameters delivered in the access parameters message The Reverse open loop method of power control provides a quick response to

changes in signal conditions.

Mobile BTS

Reverse Open LoopPower Control

Problems with Reverse Open Loop Power Control– Assumes same exact path loss in both directions; therefore,

cannot account for asymmetrical path loss– Estimates are based on total power received; therefore the

power received from other cell sites by mobile station introduces inaccuracies

Reverse Open-loop Power Control

Reverse Closed Loop Power Control

Compensates for asymmetries between the forward and reverse paths Consists of power up (0) & power down (1) commands sent to the

mobile stations, based upon their signal strength measured at the Base Station and compared to a specified threshold(setpoint)

Each command requests a 1dB increase or decrease of the mobile station transmit power

Transmitted 800 times per second, always at full power Allows to compensate for the effects of fast fading

Mobile BTS

Signal StrengthMeasurement

Setpoint

Reverse Closed LoopPower Control

Reverse Outer Loop Power Control

Most gradual form of reverse link power control– Setpoint is varied/dynamic according to the FER on the Reverse

Traffic Channel (determined at the Base Station Controller)– Sampled at a rate of 50 frames per second (20 ms / frame)– Setpoint adjusted every 1-2 seconds

Mobile BTS BSC

Reverse Outer Loop Power

Control

Setpoint

The goal of outer loop power control is adjusting the setpoint(Eb/No)

based on the reverse traffic channel FER value

If the received power from the mobile station,as measured at the

base station,is below the specified S/N threshold(setpoint),the base

station sends a “0”power control bit directing the MS to raise its

output power;if it is higher,it sends a “1” power control bit directing

the mobile station to lower its output power

The setpoint itself is raised or lowered by the reverse outer loop

power control to guarantee the desired frame error rate(FER)

level,typically 1%

Output power control bit is transmitted on the power control subchannel

in forward traffic channel

Closed-loop Power Control ProcedureReceived the FrameQuality Information

from the Reverse Link

Eb/Nt>Eb/No?

Outer-loopAlgorithm

Up PowerControl Bit

Down PowerControl Bit

Puncture toPower ControlSubchannel

Power ControlCommand

Measurement

Demodulate andmeasure Eb/Nt

Outer Loop Correction

Closed-loop Control

Base Station

Mobile

Reverse Power Control in ZTE System The open loop power control is implemented in mobile station

The outer loop power control algorithm is implemented in SVE module of

BSC, the output Eb/No is sent to Channel Card

The closed loop power control algorithm is implemented in Channel

Card, the output power control command is punctured in the forward

Fundamental Channel (traffic channel).

Forward Power Control in IS-95

The base station continually and slowly decreases power to each mobile station(each user’s forward traffic channel)

As the FER (determined at the mobile station) increases, the mobile station requests a Forward Traffic Channel power increase

Mobile BTS BSC

Adjust Fwd.power

Forward Link Power Control

The power control frequency is maximum 50Hz Power Control based on Messages for Radio

Configuration 1 Power Control based on EIB for Radio Configuration 2

Forward Power Control in IS-95(Cont.)

In CDMA2000, there is a faster method used for Forward Power Control operating much like the IS-95 Reverse Link Power control described next

In order to implement Forward Link Quick Power Control,we use Reverse Pilot channel which includes power control subchannel

Forward Quick Power Control in IS-2000

Forward Quick Power ControlReceived the FrameQuality Information

from the Forward Link

Eb/Nt>Eb/No?

Outer-loopAlgorithm

Up PowerControl Bit

Down PowerControl Bit

Puncture toPower ControlSubchannel

Measurement

Demodulate andmeasure Eb/Nt

Outer Loop Correction

Closed-loop Control

Mobile Station

Base Station

Summary of Power Control

All types of power control work together to minimizes power consumption at the mobile stations, and increases the overall capacity of the system transmit power.

FER FER

Mobile BTS BSC

Setpoint

Adjust Fwd.power

Reverse Outer Loop Power

Control

Forward Link Power Control

Reverse Open LoopPower Control

CDMA MA Call ProcessingPower-UpPower-Up

InitializationInitialization

IdleIdle

SystemAccess

TrafficTraffic

Mobile station has fully acquired

system timing

Mobile station receives a Paging Channel message requiring ACK or response, originates a call, or

performs registration

Mobile station is directed to a Traffic Channel

Mobile station ends use of the Traffic Channel

Mobile station receives an ACK to an Access Channel transmission

other than an Origination Message or a Page Response Message

Mobile station is in idle handoff with NGHBR_CONFG equal to

‘011’ or is unable to receive Paging Channel Message

In coming Call Flow

Outgoing call flow

Access failure at a glance

Thank You

cdma rf zte rakesh tripathi

loop control

btsorsignal

power control

power control

loop power

forward power

base station

base station

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