module01 1xev-do airlink training

7/27/2019 Module01 1xEV-DO Airlink Training

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Infrastructure for All-IP Broadband Mobile WirelessAccelerating Access Anywhere

Module 1: 1xEV-DO Air Interface

Jay Weitzen

Airvana Performance Engineering


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Confidential & Proprietary 2

Objectives

To help you understand the 1xEV-DO air

interface Understand the commonalities with 1xRTT

and the differences

To review the basics of CDMA applicable to1xEV-DO, just for good measure

To understand how the 1xEV-DO forwardand reverse links work

To understand 1xEV-DO mobility


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Module Coverage

Introduction to IS-2000 Family (IS-95C/1xRTT, 1xEV-DO)

Basics of Qualcomm CDMA common to 1xRTT and 1xEV-DO

1xEV-DO Architecture and Protocol Stack

1xEV-DO Air Interface Characteristics Forward Link Overview

Physical Layer

Traffic Channel

MAC

Control Channel

Reverse Link Overview

Physical Layer

Traffic Channels

Access Channel

Power Control


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Summary of Wireless Telephony

1960 1990

Standards Evolution

MTS150MHz IMTS150MHz450MHz

AMPS800MHzN_AMPSD-AMPS

CDMA

PCS1900MHzGSMCDMA

AMPS, etc

ESMR800MHz

System Capacity Evolution - UsersDozens Hundreds 100,000s 1,000,000s

Technology Evolution

Analog AM, FM Digital ModulationDQPSK

GMSK

Access StrategiesFDMA

TDMA

CDMA

Vacuum Tubes Discrete Transistors MSI LSI VLSI, ASICs

AMPS = Advanced Mobile Phone System

N_AMPS = Narrowband AMPS (Motorola)

D-AMPS = Digital AMPS (IS-54 TDMA)ESMR = Enhanced Specialized Mobile Radio

PCS-1900 = Personal Communication Systems

FDMA = Frequency Division Multiple Access

TDMA = Time Division Multiple AccessCDMA = Code Division Multiple Access

Evolution of Public Mobile Telephony


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Generations of Wireless

First Generation, Analog Circuit Switched Voice, AnalogModem/Fax over Circuit Switched Voice

AMPS

2nd Generation: Digital Vocoded Circuit Switched Voice,Circuit Switched data 16-64 kbps

IS-95 A&B, IS-136, GSM (GPRS), IDEN,

3rd Generation, Digital Circuit Switched Voice, PacketSwitched Broadband Data

CDMA 2000 (IS-95C 1xRTT)+ 1xEV-DO, WCDMA, 1xEV-DV (IS-95D),

4th Generation, Broadband Packet Switched Voice(VOIP), Broadband Packet Switched Data MBPS

IEEE 802.16, IEEE 802.15, ??? 3xEV-DO,


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History of Mobile Phones (1)


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1xEV-DO Optimized forHigh speed packet data

1xRTT High EfficiencyVoice Plus Packet data

CDMA2000

NETWORKS

Commercial Deployments

Began 2002

Two Key Goals Of CDMA-2000


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1xEV-DO Introduction

HDR (High Data Rate) - pre-standard Qualcommname

1xEV-DO (Evolution Data Optimized) 3GPP2 & ITU standard IS-856 1x = 1.25MHz, EV = Evolution, DO = Data Optimized

CDMA2000 HRPD (High Rate Packet Data) New official name

Optimized for high speed/capacity asymmetric data

Theory Best to separate circuit switched voice and packetswitched data As opposed to 1xEV-DV


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Why 1xEV-DO?

Global Standard within CDMA2000 Family

At Least 3-4 Times Faster than CDMA2000 1x

Supports All-IP Network Architecture Hybrid Handsets Support Voice and 1xEV-DO

Enables Multiple Services

Mobile, Nomadic, Fixed

Supports Multiple Device Types

Handset, PDA, Laptop,..


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Applicable Standards

Standards

IS-856-1: CDMA2000 High Rate Packet Data AirInterface,

IS-878: IOS for 1xEV

IS-864: Access Network Minimum Performance spec

IS-866: Access Terminal Minimum performance spec

IS-890: Test Application spec

IS-919: Signaling Conformance Spec

IS-925: Enhanced Subscriber Privacy for HRPD

Other standards

IS-835: Wireless IP standard

IS-2001: CDMA2000 IOS standard


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What Makes A Good Packet Data Air Interface?

High Burst Rates

Good Multiplexing Efficiency Fast Connection Setup & Teardown

Support for QoS and other Multimedia Applications

Base

Station


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CDMA Review IS-95/IS-2000 and 1xEV-

DO


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Why Start with IS-95/IS-2000

1xEV-DO is derived from IS-95 and is

waveform compatible

Much of the Physical Layer of 1xEV-DO issimilar to IS-95, reverse link is very very

similar Hybrid mode operation requires

understanding of 1x Operation!!!


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Two Types of CDMA

There are Two types of CDMA:

Frequency-Hopping

Each users narrowband signal hops amongdiscrete frequencies, and the receiver followsin sequence

Frequency-Hopping Spread Spectrum(FHSS) CDMA is NOT currently used inwireless systems, although used by themilitary

Direct Sequence

narrowband input from a user is coded(spread) by a user-unique broadband code,then transmitted

broadband signal is received; receiver knows,applies users code, recovers users data

Direct Sequence Spread Spectrum (DSSS)CDMA IS the method used in IS-95commercial systems

User 1

Code 1

Composite

Time Frequency

+=

Direct Sequence CDMA

User 1 User 2 User 3 User 4Frequency Hopping CDMA

User 3 User 4 User 1 unused User 2

User 1 User 4 User 3 User 2 unused

Frequency

unused User 1 User 2 User 4 User 3


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DSSS Spreading: Time-Domain View

At Originating

Site: Input A: Users Data @

19,200 bits/second

Input B: Walsh Code #23 @

1.2288 Mcps

Output: Spread spectrumsignal

Input B: Walsh Code #23 @

1.2288 Mcps

Output: Users Data @19,200 bits/second just as

originally sent via air

interface

Drawn to actual scale and time alignment

XORExclusive-OR

Gate

1

1

Input A: Received Signal

Input B: Spreading Code

Output: Users Original Data

Input A: Users Data

Input B: Spreading Code

Spread Spectrum Signal

XORExclusive-OR

Gate

Originating Site

Destination Site


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Spreading from a Frequency-Domain View

Traditional

technologies try to

squeeze signal intominimum required

bandwidth

CDMA uses largerbandwidth but uses

resulting processing

gain to increase

capacity Spread Spectrum Payoff:Processing Gain

Spread SpectrumTRADITIONAL COMMUNICATIONS SYSTEM

SlowInformation

Sent

TX

SlowInformationRecovered

RX

NarrowbandSignal

SPREAD-SPECTRUM SYSTEM

Fast

SpreadingSequence

SlowInformation

Sent

TX

SlowInformationRecovered

RX

Fast

SpreadingSequence

Wideband

Signal


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CDMA Uses Code Channels

A CDMA signal uses many chips toconvey just one bit of information

Each user has a unique chip pattern,in effect a code channel

To recover a bit, integrate a large

number of chips interpreted by theusers known code pattern

Other users code patterns appear

random and integrate in a randomself-canceling fashion, dont disturbthe bit decoding decision being made

with the proper code pattern

Building aBuilding aCDMA SignalCDMA Signal

Bitsfrom Users Vocoder

Symbols

Chips

Forward ErrorCorrection

Coding and

Spreading


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CDMA: The Code Magic

if 1 =if 0 =

1

Analog

SummingUsers

QPSK RF

DemodulatedReceived

CDMA Signal

Despreading Sequence(Locally Generated, =0)

matches

opposite

Decision:

Matches!( = 0 )

TimeIntegration

1

Opposite( =1)

+10

-26

Received energy: Correlation

-16

BTS

This figure illustrates the basic technique of CDMA signal generation and recovery. The actual

coding process used in IS-95 CDMA includes a few additional layers, as well see in following slides.


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CDMAs Nested Spreading Sequences

CDMA combines three different spreading sequences tocreate unique, robust channels

The sequences are easy to generate on both sending andreceiving ends of each link

What we do, we can undo

SpreadingSequence

A

SpreadingSequence

B

SpreadingSequence

C

SpreadingSequence

C

SpreadingSequence

B

SpreadingSequence

A

InputData

X

RecoveredData

X

X+A X+A+B X+A+B+C X+A+B X+A

Spread-Spectrum Chip StreamsORIGINATING SITE DESTINATION


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Other Sequences: Generation & Properties

Other CDMA sequences are

generated in shift registers

Plain shift register: no fun, sequence

= length of register Tapped shift register generates a

wild, self-mutating sequence 2N-1

chips long (N=register length)

Such sequences match if

compared in step (no-brainer,

any sequence matches itself)

Such sequences appearapproximately orthogonal if

compared with themselves

false correlation typically


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Long CodeGeneration & Masking to Establish Offset

Generated in a 42-bit register, the PN Long code is more than 40 dayslong (~4x1013 chips) -- too big to store in ROM in a handset, so itsgenerated chip-by-chip using the scheme shown above

Each handset codes its signal with the PN Long Code, but at a unique

offset computed using its ESN (32 bits) and 10 bits set by the system this is called the Public Long Code Mask; produces unique shift

private long code masks are available for enhanced privacy

Integrated over a period even as short as 64 chips, phones with different

PN long code offsets will appear practically orthogonal

Long Code Register(@ 1.2288 MCPS)

Public Long Code Mask(STATIC)

User Long CodeSequence

(@1.2288 MCPS)

11 00 01 10 00 PERMUTED ESNAND

=SUMModulo-2 Addition


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The Short PN Code

The short PN code consists of two PNSequences, I and Q, each 32,768 chips

long

Generated in similar but differently-

tapped 15-bit shift registers Theyre always used together,

modulating the two phase axes of a

QPSK modulator

IQ

32,768 chips long26-2/3 ms.

(75 repetitions in 2 sec.)

CDMA QPSK Phase ModulatorUsing I and Q PN Sequences

I-sequence

Q-sequence

cos t

sin t

chip

input

QPSK-modulated

RFOutput

*

* In BTS, I and Q are used in-phase.

In handset, Q is delayed 1/2 chip to

avoid zero-amplitude crossings which

would require a linear power amplifier


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Putting it All Together: CDMA Channels

The three spreading codes are used in different ways to create the forward andreverse links

A forward channel exists by having a specific Walsh Code assigned to theuser, and a specific PN offset for the sector

A reverse channel exists because the mobile uses a specific offset of the Long

PN sequence

BTS

WALSH CODE: Individual User

SHORT PN OFFSET: Sector

LONG CODE OFFSET:

individual handset

FORWARD CHANNELS

REVERSE CHANNELS

LONG CODE:Data

Scrambling

WALSH CODES:used as symbolsfor robustness

SHORT PN:used at 0 offset

for tracking


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Functions of the CDMA Forward Channels

PILOT: WALSH CODE 0

The Pilot is a structural beacon whichdoes not contain a character stream. It is atiming source used in system acquisitionand as a measurement device duringhandoffs

SYNC: WALSH CODE 32

This carries a data stream of systemidentification and parameter informationused by mobiles during system acquisition

PAGING: WALSH CODES 1 up to 7

There can be from one to seven pagingchannels as determined by capacity needs.They carry pages, system parametersinformation, and call setup orders

TRAFFIC: any remaining WALSH codes

The traffic channels are assigned toindividual users to carry call traffic. Allremaining Walsh codes are available,subject to overall capacity limited by noise

Pilot Walsh 0

Walsh 19

Paging Walsh 1

Walsh 6

Walsh 11

Walsh 20

Sync Walsh 32

Walsh 42

Walsh 37

Walsh 41

Walsh 56

Walsh 60

Walsh 55


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Code Channels in the Reverse Direction

Channel Element

Access Channels

Vocoder

Vocoder

Vocoder

Vocoder

more more

Receiver,Sector X

A Reverse Channel is identified by:

v its CDMA RF carrierFrequency

v the unique Long Code PN Offset ofthe individual handset

Channel Element

Channel Element

Channel Element

Channel Element

Long Code Gen

Long Code Gen

Long Code Gen

Long Code Gen

Long Code Gen

more

LongCode

LongCodeLongCode

LongCode

LongCode

LongCode


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1xEV-DO Long Code Offsets


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Short Codes in 1xEV-DO


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Near/Far Problem (I)

Performance estimates derived using assumption

that all users have same power level

Reverse link (mobile to base) makes thisunrealistic since mobiles are moving

Adjust power levels constantly to keep equal

1k


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CDMA-2000 Reverse Power Control

Three methods work in tandem to equalize all handset signal levels at theBTS:

Reverse Open Loop: handset adjusts power up or down based on receivedBTS signal (AGC)

Reverse ClosedLoop: Is handset too strong? BTS tells up or down 1 dB 800times/second

Reverse OuterLoop: BSC has FER trouble hearing handset? BSC adjustsBTS setpoint

RX RF

TX RF Digital

BTSBSC

SetpointBad FER?

Raise Setpoint

Stronger thansetpoint?

ReverseRF

800 bits per second

Occasionally,as needed

Handset

Open

Loop

Closed

Loop

Digital

All Users must be seen by the BTS at the same power level.


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Whats In a CDMA-2000/1xEV-DO Handset?


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The Rake Receiver

Every frame, handset uses combined outputs of the threetraffic correlators (rake fingers).

Each finger can independently recover a particular PN offsetand Walsh code.

Fingers can be targeted on delayed multipath reflections, oreven on different BTSs.

Searcher continuously checks pilots.

Handset Rake Receiver

RF

PN Walsh

PN Walsh

PN Walsh

SearcherPN W=0

Voice,Data,

Messages

Pilot Ec/Io

BTS

BTS


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Pilot Sets and Handoff Parameters 1xEV-DO


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Pilot Set Definition

Active Set: The set of pilots (specified by the pilots PN offset and the pilotsCDMA Channel) associated with the sectors currently serving the access terminal.When a connection is open, a sector is considered to be serving an access terminalwhen there is a Forward Traffic Channel, Reverse Traffic Channel and ReversePower Control Channel assigned to the access terminal.When a connection is notopen, a sector is considered to be serving the access terminal when the accessterminal is monitoring that sectors control channel.

Candidate Set: The pilots (specified by the pilots PN offset and the pilots CDMAChannel) that are not in the Active Set, but are received by the access terminal with

sufficient strength to indicate that the sectors transmitting them are good candidatesfor inclusion in the Active Set.

Neighbor Set: The set of pilots (specified by the pilots PN offset and the pilotsCDMA Channel) that are not in either one of the two previous sets, but are likely

candidates for inclusion in the Active Set.. Remaining Set: The set of all possible pilots (specified by the pilots PN offset and

the pilots CDMA Channel) on the current channel assignment, excluding the pilotsthat are in any of the three previous sets.


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Pilot Search Order, Speed, and Implications

Actives & candidates have the biggest influence.

Keep window size as small as possible

During soft handoff, this set dominates searcher

Minimize excessive Soft HO! Neighbor set is second-most-important

Keep window size as small as possible

Keep neighbor list as small as possible

But dont miss any important neighbors!

Remaining Set: pay your dues, but get no reward

You must spend time checking them, but the system cant assign one to you

SEARCHING FOR PILOTS:

The searcher checks pilots innested loops.

Actives and Candidates are

the innermost loop.Neighbors are next, advancesone pilot each time Act +Cand finish

Remaining is slowest,advances one pilot each

time Neighbors finish

Remaining

Active+Cand

Neighbor

WindowSize (Chips)

14 (7)

DatafillValue

Search Time(ms)

Max Delay(s)

4 5.7 19

20 (10) 5 8.1 15

40 (20) 7 16.3 12

60 (30) 8 24.4 18

80 (40) 9 32.6 19

100 (50) 10 40.7 25

130 (65) 11 52.9 30

160 (80) 12 65.1 40

226 (113) 13 92 54

Notice that when the window size is set to28 chips, the search time has a minimum.

SEARCH TIME FOR ONE PILOTAS A FUNCTION OF WINDOW SIZE

28 (14) 6 11.4 10

320 (160) 14 130 76

452 (226) 15 184 108


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Optional: Quick Primer on Pilot Search Windows

The phone chooses one strong sectors signal andlocks to it as Primary PN

accepts its offset as being exactly the PNannounced by that BTS messages

measures the offsets of all other signals bytiming comparison with it

In messages, system gives to handset a neighbor listof nearby sectors PNs

Propagation delay skews the apparent PN offsets ofall other sectors, making them seem earlier or laterthan expected

To overcome skew, when the phone searches for aparticular pilot, it scans an extra wide delta of chipscentered on the expected offset (called a searchwindow)

Search window values can be datafilled individually

for each Pilot set: There are pitfalls if the window sizes are improperly

set too large: search time increases, slows

too small: overlook pilots from far away

too large: might misinterpret identity of a distant BTSsignal

One chip is 801 feet or 244.14 m

1 mile=6.6 chips; 1 km.= 4.1 chips

PROPAGATION DELAYSKEWS APPARENT PN OFFSETS

BTS

BTSA

B

33Chipsdelay

4Chipsdelay

If the phone is locked to BTS A, the

signal from BTS B will seem 29 chips

earlier than expected.

If the phone is locked to BTS B, thesignal from BTS A will seem 29 chips

later than expected.


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Softer Handoff

Each BTS sector has unique PN offset & pilot.

Handset will ask for whatever pilots it wants.

If multiple sectors of one BTS simultaneously serve ahandset, this is called Softer Handoff.

Handset is unaware, but softer handoff occurs in BTS in a

single channel element. Handset can even use combination soft-softer handoff on

multiple BTS & sectors.


RF

PN Walsh

PN Walsh

PN Walsh

Searcher

PN W=0

Voice,Data,

Messages

Pilot Ec/Io

BTS

BSCSwitch

Sel.


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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.

All messages sent by dim-and-burst, no muting! Each end of the link chooses what works best, on a frame-by-

frame basis! Users are totally unaware of handoff.


RF

PN Walsh

PN Walsh

PN Walsh

Searcher

PN W=0

Voice,Data,

Messages

Pilot Ec/Io

BTS

BSCSwitch

BTS

Sel.


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1xEV-DO From the Top to Bottom of the

Protocol Stack


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RNAirLink

RNC

RN

PDSNA10

AT

IPPPP

R-PR-P

L1

IP

L2

IPPPP

RLP

L1AirLink

MAC

& other

IP-Abis

AirLink

MAC

& other

RLP

Backhaul

Network

L1

IP

L2

IP-Abis

IP

L2

L1

IP

L2Dedicated, Frame RelayRouter Network, Metro Ethernet

MIX & MATCH

1xEV Protocol Architecture

1xEV (IS-856)

3GPP2 (IS-878, other)


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Airvana 1xEV-DO Network Architecture

DOM

AT

AN-AAA

RNC PDSN

CN-AAA

IP Core

NetworkInternet

Backhaul

Network &

Routers

RANCore

NetworkEMSBTS


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1xEV-DO Protocol Map


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1xEV-DO Protocol Stack


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Application Layer

Signaling Application Protocol

SNP (Signaling Network Protocol)

Which protocol is the receiver of signaling message

SLP (Signaling Link Protocol)

Fragmentation, reliable/best effort delivery

Packet Application Protocol RLP

Next slide

Location Update Protocol SID, NID, PZID

Essential to provide seamless packet service through PDSN

selection and handover


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Application Layer (contd)

RLP

Retransmission to provide low error rate to

applications If MAC Packet Error Rate is Pe

After RLP error rate ~ Pe2

Example: PER = 1%, PER (after RLP) = 0.01%


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Session Layer

Session Mgmt Protocol

Address Mgmt Protocol

UATI

Session configuration Protocol


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Security Layer

Generic Security Protocol Time stamp, avoid replay attack

Key Exchange Protocol Dynamically generatedby both AT and RNC using Diffe-Hellman algorithm

Authentication Protocol MD5

Encryption Protocol

Standard defined, yet to be implemented in

chipset. Rely on end-to-end encryption to avoid double

overhead


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MAC Layer

Control CH MAC Protocol

Access CH MAC Protocol

Forward TCH MAC Protocol

Fixed size : 1002 bits

Reverse TCH MAC Protocol


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Introduction to 1x-EV-DO Air Interface

Elements from: Physical, MAC and

Connection Layer


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Design Goals of 1xEV-DO

Capacity at least 3x that of 1xRTT data

technology

System optimized for asymmetric burstydownload patterns

Some Compromise on Latency to enhance

throughput

Separate Circuit Switched Voice from Packet

Switched Data


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Guardbands are required between CDMA and non-CDMA signals

CDMA signals appear as a raised noise floor to other technologies receivers

Non-CDMA signals appear as noise to CDMA receivers

No guard band is customarily used between frequency-adjacent CDMA

signals; there is a slight decrease in capacity due to adjacent-frequency

interference but it is negligible in normal operation

260 kHz

Guard Band

260 kHz

Guard Band

Frequency

Po

wer

1.77 MHz

1.25 MHz

CDMA Carrier

CDMA SIGNAL

Coexistence of CDMA with Other Systems

iff 1 O


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Whats Different about 1xEV-DO


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1 EV DO C d Ch l


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1xEV-DO Code Channels

F d 1 EV DO Ch l


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Forward 1xEV-DO Channels

1 EV Ch l St t FL


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1xEV Channel Structure - FL

DRC

Lock

DRC

Lock

1 EV FL T ffi CH


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1xEV FL Traffic CH

TDM Constant Power

Full power for Pilot and MAC

Idle Slot Gain

Airlink Scheduler

Variable Rate (38.4kbps 2.46Mbps)

DRC (Date Rate Control) reported by AT based on SNRmeasurement based on pilot

AN MUST follow the DRC

HARQ Turbo Code + Puncturing/Repetition

Rate 1/3 & 1/5

C t l MAC d Pil t Ch l


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Control, MAC and Pilot Channels

Ad ti M d l ti (1)


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Adaptive Modulation (1)

Channel Condition Varies

Widely depending on location

Quickly due to mobility

Coding and Modulation Adapted to Varying Channel Condition to

Optimally Utilize the Channel Range of Burst Rates: 38.4 Kbps ~ 2.4 Mbps (QPSK, 8-PSK, 16-QAM)

Channel Condition Measured in Every Time Slot Using FL Pilot

Channel State Feedback: DRC Channel

DRC

Packet Data

Pilot

RN

Reverse DRC Channel is Used to Control


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Forward Rate



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FL

RL

DataPil

ot

FLTime

Slot

1.67 msec

Pil

ot

DRC

Adapti e Mod lation and Coding (3)


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Adaptive Modulation and Coding (3)

A i t F d R t C/I (AWGN)


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Approximate Forward Rate vs. C/I (AWGN)

0 dB C/I: 2 equal

strength pilots

above noise

-3 dB C/I: 3equal strength

pilots above noise

=+

=

2

1

iio CWN

C

I

CData rate[Kbps] C/I [dB]

38.4 -11.5

76.8 -9.5

153.6 -6.5

307.2 -3.0

614.4 -1.0

921.6 1.3

1228.8 3.0

1843.2 7.2

2457.6 10.5

Pilot add and

drop thresholdsdesigned to

guarantee 76.8

kbps Control

Channel

Forward Link Rate Distribution


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Forward Link Rate Distribution

1228.8

1843.2

2457.6

153.6

921.6614.4

307.2

2.4Mbps

2 Pilot

InterferenceLimited Region

Range limited

Interference +

Noise Region or

3+ pilot Soft

HandoffInterference

Limited Region

Single

Sector Data

Ratelimited by

Range

Adaptive Modulation and Coding


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Adaptive Modulation and Coding

Type II Hybrid ARQ (HARQ)


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Type II Hybrid ARQ (HARQ)

Type II Hybrid ARQ (2)


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Type II Hybrid ARQ (2)

1 1FL

RL 1

NAK ACK

2 23 54

2

NAK

6 7 8

2

ACK

13 4

ACK ACK

5

ACK

DRC Cannot Always Predict Future Channel Conditions Accurately Fast fading is unpredictable

Inter-sector interference is unpredictable

HARQ Further Improves Performance

Fast retransmission at physical layer using incremental redundancy

Increased time diversity due to interlacing

4 HARQ channels

Adaptive Hybrid ARQ (3)


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Adaptive Hybrid ARQ (3)

HARQ Example (153 6kbps: 4 slot packet)


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HARQ Example (153.6kbps: 4 slot packet)

Transmit

Slot 1

n n + 1 n + 2 n + 3 n + 4 n + 5 n + 6 n + 7 n + 9n + 8

Transmit

Slot 2

Transmit

Slot 3

Transmit

Slot 4

NAK

DRC

Request for153.6 kbps

NAK

Slots

Forward Traffic

Channel Physical

Layer Packet

Transmissions

with 153.6 kbps

DRC Channel

Transmission

Requesting153.6 kbps

ACK ChannelHalf-Slot

Transmissions

NAK ACKor

NAK

n + 10 n + 11 n + 12 n + 13 n + 14 n + 15

One Slot

One-Half Slot Offset

HARQ Example (4 slot packet)


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Transmit

Slot 1

n n + 1 n + 2 n + 3 n + 4 n + 5 n + 6 n + 7 n + 9 n + 10 n + 11n + 8 n + 12

Transmit

Slot 2

Transmit

Slot 3

Transmit

Slot 1

NAK

DRC

Request for

153.6 kbps

NAK ACK

Slots

Forward Traffic

Channel Physical

Layer PacketTransmissions

with 153.6 kbps

DRC Channel

TransmissionRequesting

153.6 kbps

ACK ChannelHalf-Slot

Transmissions

First Slot for the Next

Physical Layer Packet

Transmission

One-Half Slot Offset

One Slot

2.4 Mbps DRC cannot really benefit from Hybrid ARQ

HARQ Example (4 slot packet)

1xEV-DO MAC Channel


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1xEV-DO MAC Channel

Adaptive Data Scheduler: Basics


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Adaptive Data Scheduler: Basics

Airlink Scheduler


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Airlink Scheduler

Scheduler assigns the next available time slot to one of ATs

who has data in scheduler queue

Scheduler decision based on channel condition, fairness,

and/or QoS

RN

307.2

Kbps

153.6 Kbps

2.4

Mbps 614.4

Kbps

Packet Data @ 153.6 Kbps

Airlink Scheduler (cont)


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Airlink Scheduler (cont)

Getting the Most Out of Each Slot


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Getting the Most Out of Each Slot

1xEV FL Traffic CH


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76

2457

1228

614

921

307

1228

921

153

1228

76IDLE

2457

BurstRate(

Kbit/s)

BurstRate(

Kbit/s)

TimeTime

Control

User 1

User 2

User 3

User 4

BTS

User 1

User 2

User 3

User 4Rate Requests

DRC DRC

DRC DRC

Conceptual diagram

1xEV FL Traffic CH

Multi-User Diversity Gain (1)


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Higher gain when there is more fluctuation in channelcondition and/or when there are more users


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Multi User Diversity Gain (2)

For example,

Assumptions

Rayleigh fading

Unlimited bandwidth

No rate quantization

Simulation shows 50 ~ 100%

gain achievable even at small

N = 4 ~ 8 Drive test shows up to about

40% gain at N = 40 2 4 6 8 10 12 14 16

1

1.5

2

2.5

3

3.5

N = Number of Users

K(N)

=

=Nn n

NK,...,1

1)(


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Proportional Fairness Scheduler


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Next time slot at time t+1 given to an AT with the highestmetric given by

DRCi(t): DRC of i-th AT at time t

Ri(t): Time-averaged throughput of i-th AT at time t

Steady state analysis shows that ideally User throughput Ri is proportional to its time averaged DRCi(t)

Each AT gets the same number of time slots

Similar to round robin except multi-user diversity gain K(N) isobtained, where N is the number of ATs

Proportional Fairness Scheduler

)(

)(

tR

tDRC

i

i

N

DRCNKR ii )(=

QC G-Scheduler


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QC G Scheduler

Give slot to user i who has biggest

A_i(t)*DRC_i(t)/R_i(t)

DRC_i (t): Instantaneous Requested Rate of User i at time t (every slot,

time varying in general) R_i (t): Average Throughput of User i at time t

Features

Flexible Fairness : setting A_i(t) as a fcn of Average DRC QoS: setting A_i(t) as a fcn of QoS

Intra-User QoS Scheduler


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Intra User QoS Scheduler

Differentiated QoS Services for Multiple Flows within an AT

Three Classes of QoS

EF: Expedited forwarding

For delay and jitter sensitive traffic

Guaranteed to meet a pre-configured delay bound

Subject to overload control to prevent it from starving resources for

flows in other classes

AF: Assured forwarding

For rate sensitive traffic

Guaranteed to meet a pre-configured required rate

BE: Best effort Other non-QoS flows get remaining time slots not used by EF or AF

flows

Uses proportional fairness algorithm

Flexible Fairness Scheduler


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Proportional fairness can be very unfair

Fairness scheduler can reduce sector throughput significantly

Trade-off between sector throughput and fairness

Airvanas flexible fairness scheduler allows any fairness

between Completely Fair and Proportionally Fair

Proportional

FairnessScheduler

Flexible Fairness

Scheduler

Forward Link User Throughput

%of

Users

Forward Link Fast Selection Handoff


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Soft handoff provides Seamless handoff

Macro diversity

Soft handoff is not desirable in the forward link Synchronized transmission of high speed data from multiple

base stations is not easy

Increased backhaul traffic

Fast selection handoff provides

Near-seamless handoff (interruption time ~100 msec)

Similar macro diversity gain as soft handoff

Enables fast scheduling at BTS


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1xEV-DO MAC Layer and MessagingStructure

How the Network Communicates

With the Access Terminal Over the

Air Interface

MAC Channel


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3 subchannels RA (Reverse Activity) Channel

RAB: For reverse rate control, 1 bit per sector

RPC (Reverse Power Control) Channel

1 bit for each active AT

DRCLock Channel 1 bit for each active AT

RPC CH and DRCLock CH in TDM

RAB & (RPC, DRCLock) are in CDM (Walsh 64)

MacIndex (0 63) RAB gain & (RPC, DRCLock) gain (sum is always full power)

Active Slot

Idle Slot

Data40 0

Chips

Data40 0

Chips

Data40 0

Chips

Data40 0

Chips

1/2 Slot

1,024 Chips

1/2 Slot

1,024 Chips

Pilot96

Chips

MAC64

Chips

MAC64

Chips

Pilot96

Chips

MAC64

Chips

MAC64

Chips

Pilot96

Chips

MAC64

Chips

MAC64

Chips

Pilot96

Chips

MAC64

Chips

MAC64

Chips

1xEV Control CH


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Serves the function of IS-95s Sync & Paging CH

Control Channel Cycle (256 slots)

Synchronous Capsule (SC)

CCSyn

CCSynSS

Paging & QuickConfig must come here

Asynchronous Capsule (AC) Fixed Rate: 38.4 or 76.8kbps

CCH carries only signaling (no user data traffic)

ACH too

Example of Messages


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p g

Complete list in IS-856 Specification Each message shows in which MAC

channel it can be sent Example)

QuickConfig

Sync SectorParameters

ConnectionRequest

BroadcastReverseRateLimit Etc.

Idle State Messages


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g

Connected State Messages


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g

1xEV FL Control CH


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Control Channel Cycle(256 slots = 426.66 ... ms)

Control Channel Cycle(256 slots = 426.66 ... ms)

SC ACSCAC

An SC with 2 MAC

Layer packets

SC: Synchronous Control Channel capsule.

AC: Asynchronous Control Channel capsule.

Offset Offset1 time slot = 1.66 msec

Fixed Rate: 38.4 or 76.8kbps

IS-2000 and 1xEV-DO Paging Cycle


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g g y

PreferredControlChannelCycle = R R can be set to avoid collision

80 msec

t

1xPage

1xPagesleeping

2.56 sec (SCI = 1)

t

1xEV

Page sleeping

Always 5.12 sec

1xEV

Page

R*5.12/12

1xPage

Basic Data Units


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PPP IP Data PayloadIP packet

from RAN

1002 bits22 bits

MAC packet

always 1024bits

22 bits

22 bits

1002 bits

1002 bits

At 38.4 DRC

must use 16

time slots to

send this

packet

At 2.4 Meg

DRC can

send 4 ofthese in one

time slot

22 bits 1002 bits

1 4

. .

Handoff


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RL : Soft handoff FL : Virtual Soft handoff

Selection Handoff

DRC Cover

SofterHandoffDelay, SoftHandoffDelay

DRC_Cover = sector A

DRC = 76.8kbps

A B

FL

1xEV Channel Structure - RL


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DRC

Lock

DRC

Lock

1xEV-DO Reverse Channels


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Reverse MAC Channels


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DRC Length


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a) DRCLength = 1

b) DRCLength = 2

c) DRCLength = 4

d) DRCLength = 8

DRC ChannelTransmission

Forward Traffic Channel Slots

Where the Information in theDRC Channel Transmission is

Used for New Physical LayerPacket Transmissions

DRC ChannelTransmission

Forward Traffic Channel SlotsWhere the Information in theDRC Channel Transmission is


DRC Channel

Transmission

Forward Traffic Channel SlotsWhere the Information in theDRC Channel Transmission is

Used for New Physical Layer

Packet Transmissions

DRC Channel

Transmission

Forward Traffic Channel Slots

Where the Information in the

DRC Channel Transmission is


One Slot

Higher DRC Length

Pros: Less power

Cons: Less accurate DRC

1xEV Reverse Traffic Channel


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Variable-rate code division multiple access User Rate = 9.6-153.6 kbit/s

Sector Max = 350 kbit/s Rate Control

Reverse Activity Bit (RAB)

Rate Limit messages

Power Control

RPC bit in MAC channel Frame = 26.66 msec (16 slots)

Reverse Traffic Channel


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Pilot CH MAC CH

RRI (Reverse Rate Indicator)

DRC (Data Rate Control)

ACK CH

For HARQ

Data CH

Starts at FrameOffset (0 15)

These CHs multiplexed in I&Q, TDM, CDM For both User Traffic & Signaling

Capacity: Over 200 kbps (> 2 times of IS-95A)

Reverse Link Modulation


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1616161616Number ofSlots

409620481024512256Bits/packet

BPSKBPSKBPSKBPSKBPSKModulationType

153.676.838.419.29.6Data Rates

(kbps)

Access Channel


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AT transmits a random access probe sequence to access toAN before the reverse link power control loop is closed.

An access probe consists of a preamble part transmitting a

pilot signal, and a two-frame long access channel data packetat 9.6 kbps.

The MAC channel of the access data packet consists of only a

RRI channel punctured into the pilot channel.

Pilot Pilot Pilot/MAC

Message Capsule

(9.6 or 19.2 kbps)

I phase

Q phase

Preamble Frame 1 Preamble Frame 2

Pilot/MAC

Access Channel Data Packet

Data Frame 1 Data Frame 2

Access Channel


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9.6kbps

Actual Access Probe Transmission

Preamble

(PreambleLength x 16 slots)

Capsule

( up toCapsuleLength

Max x 16 slots)

AccessCycleDuration AccessCycleDuration

Beginning of an

Access Channel

Cycle

Beginning of an

Access Channel

Cycle

...

Access Probes


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probe

probe

sequence

p

1 2 3 Np

1

persiste

nce

s

p

1 2 3 Np

2

persiste

nce

p

1 2 3 Np

Ns

persiste

nce

Time

...

...

Access Channel Parameters


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Access channel is 9.6k

Access Parameter Message

Access Cycle Duration, OpenLoopAdjust,ProbeInitialAdjust, ProbeNumStep,

PreambleLength, Apersistence

Attributes

CapsuleLengthMax, PowerStep, ProbeSeqMax,

ProbeBackoff, ProbeSeqBackoff

Transition Probabilities and RL MAC


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1xEV RL Rate Control


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Rate


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CurrentRate

RABCondition MaxRateTrue MaxRateFalse

0 0 True 9.6kbps N/A

9.6kbps 0 x < Transition009k6_019k2 19.2kbps 9.6kbps




153.6kbps 0 False N/A 153.6kbps

0 1 False N/A 9.6kbps

9.6kbps 1 False N/A 9.6kbps





Non-deterministic uneven RL Rate among Users

RL Power Control


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Similar to IS-95, 800 times/second

Pilot power is controlled

Based on RPC bit, increase/decrease/stay pilot power

If any sector says to go down, the power will be

decreased

Data power is relative to Pilot power 9.6kbps ~ pilot power + 3.75dB

153.6kbps ~ pilot power + 18.5dB

Power Control


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Optimize AT transmit power to achieve minimum possibletransmit power with acceptable Frame Error Rate

Open-Loop Power Control

- Estimates output power from the received Forward Pilot Channel- Implemented entirely in the AT

Closed-Loop Power Control Inner-Loop Power Control

AN sends UP/DOWN commands at 600 Hz to keep AT Txpower at setpoint

Implemented in the BTS. FL and RL may not be balanced, agood FL may not always guarantee good RL. RN can dictate

based on S/I ratio

Outer-Loop Power Control

Sets the PC setpoint to target a x% FER

Implemented in the BSC

1xEV-DO Reverse Power Control


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Three methods work in tandem to equalize all handset signal levels at theBTS:

Reverse Open Loop: handset adjusts power up or down based on receivedBTS signal (AGC)

Reverse ClosedLoop: Is handset too strong? BTS tells up or down 1 dB 800

times/second

Reverse OuterLoop: BSC has FER trouble hearing handset? BSC adjustsBTS setpoint

RX RF

TX RF Digital

BTSBSC

SetpointBad FER?Raise Setpoint

Stronger thansetpoint?

ReverseRF

800 bits per second

Occasionally,as needed

Handset

OpenLoop

Closed

Loop

Digital

All Users must be seen by the BTS at the same power level.


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1xEV-DO Mobility

Mobility between RNs


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Similar to cdma2000

Dormant AT

Actively monitoring only one sector

Distance based RouteUpdate (RouteUpdateRadius)

Tradeoff : signaling activity from routeUpdate vs. paging area

RouteUpdateMessage Dormant AT: Distance based RouteUpdateMessage

Active AT: based on SNR measurement

Sent whenever Access Probe is sent E.g.) Connection Request

Mobility between RNs (Contd)


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Active AT AT sends RouteUpdateMessage based on SNR

measurement

AN makes final decision based on ATRouteUpdate Message

TCA message

Non-Dynamic

PilotAdd, PilotDrop, PilotCompare, PilotDropTimer,NeighborMaxAge

Dynamic

Above + AddIntercept, DropIntercept, SoftSlope

Soft Handoff Call Flow


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RN2

BetaRNCAT PDSN

ABIS: RemoveTcReq

ABIS: RemoveTcRsp

Forward Link Traffic

Soft Handoff Call Flow

AddingPilot

RN1Alpha

RTC: RouteUpdate (AlphaPN, BetaPN)

ABIS: SetSoftHoReq

ABIS: SetSoftHoRsp

ABIS: AddTcReq

ABIS: AddTcRsp

ACAck

ABIS: FtcDesiredInd

ABIS: RtcAcquiredInd

FTC: TrafficChannelAssignment (AlphaPN,BetaPN)

FTC: RTCAck

RTC: TrafficChannelComplete (AlphaPN, BetaPN)

RTC: RouteUpdate (AlphaPN with Keep=0,BetaPN)

ABIS: SetSoftHoReq

ABIS: SetSoftHoRsp

ACAck

FTC: TrafficChannelAssignment (BetaPN)

RTC: TrafficChannelComplete (BetaPN)

Alpha Pilot Drops below PilotDrop

Beta Pilot rises above PilotAdd

ABIS: FtcStoppedInd

ABIS: FlushFtcQueueReq

Forward Link Traffic

AT points DRC to Beta Sector

DRC

Switch

DroppingPilot

LEGEND

AC Access Channel

CC Control Channel

FTC Forward Traffic ChannelRTC Reverse Traffic Channel

Important Change in Neighbor Processing


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Beginning with release 2.2 to speed up inter-RNCtransfer:

Pilots which are not neighbors will not be added to theactive set.

The RNC will treat them as pilots from a neighboring

RNC subnetwork. Getting the neighbor list right is even more

important.

From the AT view, it will look like the remainingset search window is 0, but do not do this becauseyou cannot transfer to a different RNC then.


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End of ModuleThank You

Accelerating Access Anywhere

module01 1xev-do airlink training

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