Cdma2000 1xEV-DO Procedure Flow

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cdma2000 1xEV-DO Procedure Flow

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Chapter 1 Why to use 1xEV-DO?Chapter 1 Why to use 1xEV-DO?

Chapter 2 Network StructureChapter 2 Network Structure

Chapter 3 Channel StructureChapter 3 Channel Structure

Chapter 4 Forward LinkChapter 4 Forward Link

Chapter 5 Reverse LinkChapter 5 Reverse Link

Chapter 6 Overhead MessageChapter 6 Overhead Message

Chapter 7 Access ProcedureChapter 7 Access Procedure

Chapter 8 SHO & VSHOChapter 8 SHO & VSHO

Chapter 9 EVDO Procedure FlowChapter 9 EVDO Procedure Flow

Chapter 10 Air Link ParametersChapter 10 Air Link Parameters


Session Establishment

UATI assignment & configuration

negotiation

access authentication

location update

connection setup


Session Establishment(2)

a. The AT and the AN initiate HRPD session establishment. A session is

established where protocols and protocol configurations are negotiated,

stored and used for communications between the AT and the AN.

b-c. The AT and the AN initiate Point-to-Point Protocol (PPP) and LCP

negotiations for access authentication.

d. The AN generates a random challenge and sends it to the AT in a

CHAP Challenge message. AT sends the CHAP response message to

AN.

e-f. AN sends an Access-Request message on the A12 interface to the

AN-AAA. The AN-AAA looks up a password based on the User-name

attribute in the Access-Request message and if the access authentication

passes, the AN-AAA sends an Access-Accept message on the A12

interface.


Session Establishment(3)

g. The AN returns an indication of CHAP access authentication

success to the AT.

h. AN updates the ANID in the AT using the Location Update

procedure. The AN may also retrieve the PANID from the AT if

necessary.

i-m. The service connection of air interface and A8/A10 interface

are established.

n. The PPP link is established between AT and PDSN.

o. Now, connection is established, the user data packets can be

sent on the PPP link between AT and PDSN.

Following, we are going to talk about the detail of every step.


Unicast Access Terminal Identifier

24 bit104 bit

UATI 104 (Subnet) UATI 24

Color Code

8 bit

UATI 32

ATI Type

ATI Type Description

ATI Length (bits)

'00'Broadcast ATI

(BATI)0

‘01’Multicast ATI

(MATI)32

‘10’Unicast

ATI(UATI)32

'11'Random ATI

(RATI)32

RATI is used between AN and AT before UATI is assigned. BATI is used when AN broadcasts message on CC channel. After UATI assignment, UATI is used to identify AT on air interface. When subnet changed, AT should send UATIRequest for updating UATI. It

is similar to registration based on registration zone in 1x.


UATI Assignment

1. After AT acquired a network, it will send

UATIRequest with RATI for

UatiAssignment.

2. AN uses ESN for distinguishing AT. So,

AN sends HardwareIDRequest to enquery

ESN (Electronic Serial Number) of AT.

3. After getting ESN from

HardwareIDResponse, AN assigns an

UATI and sends it to AT. Including

UATIColorCode and UATI024.

4. AT responses it with UatiComplete.

AT

UatiRequest

HardwareIDRequest

HardwareIDResponse

AN

UatiAssignment

UatiComplete

UATI = UATIColorCode | UATI024

After UATI assignment, AT will use UATI to communicate with AN.


Configuration Negotiation

AN and AT may consult with each other on some air interface parameters.

We called this consulting procedure as configuration negotiation. Before negotiation, AN and AT communicate with default values.

After coming to agreement on a parameter, AN and AT will use the negotiated

value.

If AN and AT can not get consensus, they will use default value.

RF parameters needed to be negotiated for DO rev0:PilotIncrementSearchWindowActiveSearchWindowNeighborSearchWindowRemaining

PilotAddPilotComparePilotDropPilotDropTimerDynamicThresholdsSoftSlopeAddInterceptDropInterceptNeighborMaxAge

ProbeSequenceMaxProbeBackoffProbeSequenceBackoff

DataOffsetNomDataOffset9k6DataOffset19k2DataOffset38k4DataOffset76k8DataOffset153k6RPCStep

Transition009k6_019k2Transition019k2_038k4Transition038k4_076k8Transition076k8_153k6Transition019k2_009k6Transition038k4_019k2Transition076k8_038k4Transition153k6_076k8


Configuration Negotiation FlowAT AN

The sender uses the ConfigurationRequest message to provide an acceptable attribute value list of each attribute. The sender should list the acceptable attribute values of each attribute in the order of descended priority.

The receiver uses the ConfigurationResponse message to provide the accepted attribute value list of each attribute. These accepted attribute values are selected from the acceptable attribute value list.

When all configuration negotiations are complete, the sender sends the ConfigurationComplete message.

The sender uses the ConfigurationRequest message to provide an acceptable attribute value list of each attribute. The sender should list the acceptable attribute values of each attribute in the order of descended priority.

The receiver uses the ConfigurationResponse message to provide the accepted attribute value list of each attribute. These accepted attribute values are selected from the acceptable attribute value list.

When all configuration negotiations are complete, the sender sends the ConfigurationComplete message.


Access Authentication

1. Setup connection between AN and AT

(i.e. traffic channel of air interface). Refer

to AN Originated Connection Setup.

2. The AT and the AN initiate PPP and LCP

negotiations for access authentication.

Refer to IETF: RFC 1661, Point-to-Point

Protocol.

3. The AN generates a random challenge

and sends it to the AT in a CHAP

Challenge message.

4. The AT answers it with CHAP response

message which carries access user

name and encrypted password.

AT AN AN-AAA

Connection Setup

LCP Configure-Request

LCP Configure-Ack

CHAP Challenge

CHAP Response

A12 Access Request

A12 Access Accept/ A12 Access reject

CHAP(authorization result)

Connection Close


Access Authentication (2)

5. When the AN receives the CHAP response message from the AT, it sends an

Access-Request message on the A12 interface to the AN-AAA. Which carries:

access user name (Network Access Identifier),

CHAP-Password,

IP address of AN,

CHAP-Challenge = challenge value issued by AN,


Access Authentication (3)

6. The AN-AAA looks up a password based on the User-name attribute in the

Access-Request message. If the access authentication passes, the AN-AAA

assigns an IMSI and sends an A12 Access-Accept message back to AN.

7. If the access authentication fails, the AN-AAA sends an Access-Reject message

on the A12 interface.

IMSI = 250092040002807

8. The AN returns an

indication of CHAP

access authentication

success or failure to

the AT.

9. IMSI is used between

AN and PDSN and

PDSN-AAA.


Case – two ATs with same access user name (Nigeria)

Access user name is written in AT’s memory. If there is an access user

name written into two ATs. That is two ATs get the same access user

name.

AN-AAA assigns IMSI according to access user name for every AT. So,

the two ATs will get same IMSI.

AN uses ESN to distinguish the ATs, and setup two traffic channel for

these two ATs. But PCF and PDSN use IMSI to distinguish ATs and setup

only one link.

So, both of the two ATs can not transmit packets to internet.

AP1

AP2

AN PCF PDSN

INTERNET

AT


Location Update

The AN uses LocationRequest to query

the AT of its Location information.

The AT sends the LocationNotification

message to AN either in response to the

LocationRequest message or in an

unsolicited manner.

If the subnet changed, the AN May send a

LocationAssignment message to update

the Location information.

If the AT receives a LocationAssignment

message, it shall send a

LocationComplete message.

AT

LocationRequest

LocationNotification

AN

LocationAssignment

LocationComplete

LocationValue Length

SID 15

NID 16

PACKET_ZONE_ID 8


AT Originated Connection Setup

Detail:

① AT requests AN to

setup connection.

② AN acknowledges

reception of CR. AT

stops probe when rx

this Ack.

③ establish A8 & A10.

the forward packets

between and are ③ ⑦buffered at PCF.

④ AN prepares terrestrial

and air link resource

for TCH.

⑤ AN send TCA to AT.

AT AN PCF PDSN

ConnectionRequest(RouteUpdate Message)

TrafficChannelAssignment

TrafficChannelComplete

A9 Setup A8

A9 Connect A8

ACAck

RTCAck

Pilot+DRC

A11 registration request (lifttime ≠0)

A11 registration reply(accept)

A11 registration request (accounting)

A11 registration reply

A9 Update A8

A9 Update A8 Ack

PPP link negotiation and establishment ⑨

④

①

②

③

⑤

⑥

⑦

⑧


AT Originated Connection Setup (2)

⑥ when AN acquire the

reverse pilot channel

and decode DRC

channel, it sends

RTCAck to AT. Now

both forward and

reverse links are

ready.

⑦ AN tells PCF that PCF

can send downlink

packets now.

⑧ and PCF sends

accounting information

to PDSN.

⑨ PPP link is etablished

between AT andPDSN. PPP parameters are negotiated and IP address is allocated.

⑩ now the user’s service data can be transmitted on the link.


AN Originated Connection Setup

◎ in dormant, A10 and PPP link is maintained. Air link and A8 were torn down.

① packets from PDSN arrived at PCF. PCF send A9 BS service request to ask AN re-active the traffic link.

② AN page the AT by sending paging message on CC.

④ A10 already exist, it is not necessary to build it again.

AT AN PCF PDSN

ConnectionRequest(RouteUpdate Message)

TrafficChannelAssignment

TrafficChannelComplete

A9 Setup A8

A9 Connect A8

ACAck

RTCAck

Pilot+DRC

A11 registration request (accounting)

A11 registration reply

A9 Update A8

A9 Update A8 Ack

Dormant, PPP link is maintained ◎

④

①

②

⑤

⑥

⑦

⑧

paging

packet data arrivedA9 BS service request

A9 BS service response

③


Connection Release (by AT or AN)

If the AT receives a

ConnectionClose message, it

shall send a ConnectionClose

message to AN.

If AN receives a

ConnectionClose message, it

shall consider the connection

closed. It is not necessary to

send ConnectionClose to AT.

A9 release-A8 carries release

cause “Packet call going

dormant”.

A11 registration request is not

for release A10 but for carrying

accounting information.


Connection Release (Initiated by PDSN)

Connection Releasing Initiated by PDSN will tear down A10 and PPP link

together with air traffic channel and A8 link.

lifetime =0 means to release the A10 link


Session Release

If AT receives sessionClose message, it will send sessionClose to AN.

If AN receives sessionClose message, it is not necessary to send sessionClose to AT.

with A8 connection

without A8 connection


Soft Handoff

Correct neighbor list and GPS clock is essential important for

SHO.PN1 = 4 PN2 = 172

MS can’t see PN2 until find it in remainder set

Neighbor list:

PN1, 340

PN2, 64

PN3, 128

PN4, 72

PN1 = 4 PN2 = 172, but BTS send PN=174 caused by wrong clock.

MS can’t see PN2 even in remainder pilot set. PN2 becomes an island.

Neighbor list:

PN1, 340

PN2, 172

PN3, 64

PN4, 128

PN5, 72 SHO depends on AT reporting RouteUpdate


(DRCCover = 2)

(DRCCover = 2)

(last packet number)

(to clear the remainder packets in BTS buffer)

Virtual Soft Handoff

1. DRCCover = 1, BTS1 is the serving sector. BSC sends packets to BTS1 and BTS1

sends packets to AT.

2. When AT moves to BTS2, DRCCover change to 2, i.e. BTS becomes serving sector.

3. BTS2 requests BSC

to send packets to it,

while BTS1 requests

BSC to stop sending

packets, and tells

BSC the last packet

number it sent.

4. So, BSC turns to

BTS2, and BTS2

begin to send traffic

data to AT.

5. BTS1 clear its buffer

for handoff back


Case – imbalance of forward and reverse link (Romania)

In soft handoff, a branch maybe has best forward link but not best

reverse link. Maybe caused by high site, different tx power, reverse

interference. For example: forward link of AP1 is better than AP2, but reverse link of

AP2 is better.

1. Only AP1 in the active set. C/I of AP1 is 3dB, its reverse link is not good, but

power control can increase the AT’s power. DRC channel is OK!

2. When AP2 added, it will indicate AT to decrease its power. And AP1 can lock

DRC channel. The serving sector will switch to AP2.

AP1 AP2

DRC ok!

AT

AP1

AT

DRC ok!

Tx = 10dBm

C/I = 3dBAP1 can

not lock DRC

Tx = 0dBm

C/I = 3dBC/I = 0dB

DRC = 921.6kbps DRC = 614.4kbps

try best to avoid

this situation


Keep Alive

AN will check periodically (default

period is 54/3 hours, MOD DOGCNP)

whether AT is alive or not. If not, the

session will be closed. In idle (with session without

connection), AN and AT use keepalive

message to shake hand with each

other. In connection state, AN will send TCA

to check AT alive or not.

connection established


Hybrid Access Terminal

Hybrid AT Rulers: A HAT supports operation on both IS-2000(1x) and IS-856(EVDO)

network. With only one antenna/transceiver, it operates in a time-multiplexed

fashion referred to hybrid mode. If acquired 1x network only: In idle or dormant data session on 1x, HAT

periodically attempt to acquire EVDO. If acquired EVDO network only, In idle or dormant data session on EVDO

system, HAT periodically attempt to acquire 1x. If acquired both networks, In idle on both IS-856 and IS-2000 systems,

dormant data session should be on EVDO system. A HAT performs 1x idle state slotted operation regardless of whether the

hybrid access terminal is idle, dormant, or active on EVDO network. For handoff between 1x and EVDO network, the IMSI registered in AN-

AAA should be same as IMSI registered in HLR.


HAT Acquire Network

HAT first acquires 1x, then EVDO.

When acquiring 1x, accessing 1x,

or active in 1x, HAT does not

monitor EVDO.

When accessing EVDO, HAT

does not monitor 1x.

In 1x sleep state,

HAT monitor

EVDO.

In EVDO sleep

state, HAT

monitor 1x.


HAT Monitor 1x & DO in Dormant or Idle

In idle, hybrid AT monitors both 1x and DO network in slot mode. To ensure that mobile-terminated 1x services can be supported whenever

an 1x network is available, a hybrid AT performs 1x idle state slotted

operation regardless of whether the hybrid AT is idle, dormant, or active

on an EVDO network. In 1x active state, AT will not monitor EVDO network.

5.12s2.56s

1x monitoring slots

DO monitoring slots


Case - HAT Monitor 1x Paging Channel In EVDO Active

This is a CAIT picture of EVDO from Romania network. In active state of EVDO, AT went to 1x paging channel every 2.56s. Every

time AT send DRC = null to prevent AN from sending packets.


1x -> DO Dormant Handoff with HRPD Session Already

Hybrid AT moves from 1x only area to EVDO covered area. It prefers EVDO

for data service.

Location

Notification carries

the packet zone id,

which will be send

to PDSN. A9 setup A8

carries DRS=0, so,

PCF will setup A10

but not setup A8.


1x -> DO Dormant Handoff without HRPD Session


DO -> 1x Dormant Handoff

If hybrid AT in DO dormant lose the air link, it will handoff to 1x network. In 1x

dormant, it still search DO network periodically. But, after re-active in 1x, it will lock on 1x continuously.


Case – why the EVDO only get 70kbps? (Nigeria)

The average rate in 1x network is 50-70kbps.

When Hybrid AT moves from 1x+DO area to 1x only area, it will dormant

handoff from EVDO to 1x network. Its data speed should be much less

than EVDO. But user does not know the fact and complain it.

AT dialing software or phone screen should give some indication to user.

1x + DO

only 1x

AT


Terminated Voice Call in DO Active State

In DO active state,

hybrid AT still

monitor 1x network

in slot mode.

When AT received

page. It just turns to

1x network without

notifying AN.

Source AN lost air

link, and release

traffic link to

dormant.

Target BSS setup

voice call for AT.

5s

3s


An Example of Hybrid AT


Inter-AN Dormant Handoff

UATIRequest carries

the UATI of source

AN.

The first 8 bits of UATI

is the color code of

source AN. So target

AN can find source

AN to request old

session information.

Target AN copy the

old session

configurations and

store them. It is not

necessary to

negotiated again.


User Signaling Flow Tracing at Local Maintenance Terminal

If you want to trace A12, A13, ESN must be input.

For other interface, IMSI is necessary.

If you want to trace A12, A13, ESN must be input.

For other interface, IMSI is necessary.


User Signaling Flow Tracing at Local Maintenance Terminal (2)


Case – some bottlenecks reducing the speed

Abis: in general, 3 sectors of BTS share the bandwidth of Abis. If Abis bandwidth is

not enough, it will limit the download and upload speed directly. A10: in general, A10 bandwidth is enough. But sometimes, it also become a

bottleneck. Landswitch: the active Landswitch of Boise ever fault, some packets sent to it got

lost. It reduce the data speed greatly. After we switch it to backup Landswitch, it

restored. If there are any packets lost at territory link, they will be re-transmitted by TCP. It

will be very harmful to data speed. It is more than air interface, because there is

RLP in the air interface to compensate packet error.

Internet

ftp server

PDSNAN/PCF

Abis

BTS

UmA10/A11

AT

Landswitch2

Landswitch1


Chapter 1 Why to use 1xEV-DO?Chapter 1 Why to use 1xEV-DO?

Chapter 2 Network StructureChapter 2 Network Structure

Chapter 3 Channel StructureChapter 3 Channel Structure

Chapter 4 Forward LinkChapter 4 Forward Link

Chapter 5 Reverse LinkChapter 5 Reverse Link

Chapter 6 Overhead MessageChapter 6 Overhead Message

Chapter 7 Access ProcedureChapter 7 Access Procedure

Chapter 8 SHO & VSHOChapter 8 SHO & VSHO

Chapter 9 EVDO Procedure FlowChapter 9 EVDO Procedure Flow

Chapter 10 Air Link ParametersChapter 10 Air Link Parameters

Documents

Cdma2000 1xEV-DO Procedure Flow