Module12 Hybrid Training

7/27/2019 Module12 Hybrid Training

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Infrastructure for All-IP Broadband Mobile Wireless Accelerating Access Anywhere

Module 12: IS-856/IS-2000 Hybrid Mode

Operation

Jay Weitzen

Airvana Performance Engineering



Confidential & Proprietary 2

Module Objectives

• Understand Hybrid Mode operation

– Idle

– Traffic states

– Handover between 1xRTT and 1xEV-DO

• Understand Interaction between 1xEV-DOand 1xRTT




Contents

• Introduction

• Terminal provisioning

• Hybrid operation

• Non-hybrid operation

• Data session handoff

– Detecting end of coverage

• Data dedicated transmission mode (DDTM)




References




Introduction

• Why Hybrid Mode

– Augment IS-95/IS-2000 service offering by

adding IS-856 high speed packet data servicecapability

• Hybrid Mode:Key Functionality – All currently supported service options on IS-

95/IS-2000 including data

– Packet data service on IS-856

– Packet Session Handoff between IS-95/IS-2000

and IS-856




Terminal Modes




Terminal Provisioning




Sample QPST Hybrid PRL




Terminal Provisioning (Cont’d)




Hybrid Mode operation Call State Machine




Hybrid Operation: 1xRTT and 1xEV-DO Share

Same Air Interface

• Sleep timelines for IS-95/IS-2000 and IS-856 air interfaces are combined

– Wakeups for IS-95/IS-2000 and IS-856 air interfaces are scheduled on the same radiointerface

– Terminal can negotiate a desired offset for theIS-856 paging slot to avoid a collision with theIS-95/IS-2000 paging slot




IS-2000 Paging CH monitoring

• PreferredControlChannelCycle = R

– R can be set to avoid collision

80 msec

t

1x

Page

1x

Pagesleeping

2.56 sec (SCI = 1)

t

1xEV

Page sleeping

Always 5.12 sec

1xEV

Page

R*5.12/12

1x

Page




Hybrid Operation: Initialization State (2)

• When the device is in hybrid and loses 1x acquisition, previously it would commit the searcher to reacquiring 1xforever, never even trying to acquire 1x-EVDO.

• A change has been made (DMSS 3.3) to 1x acquisitionschedule to ensure that 1xEVDO gets a chance to acquirethe system even if 1x system is not acquired yet. – When the device is turned on, the 1x acquisition attempts are

interleaved with 1xEVDO system acquisition searches. If the 1xsystem is not acquired after going through the 1x channel list, the1x enters an enhanced power-save algorithm which ensures that1xEVDO gets a chance to acquire system. The device can operate

on 1xEVDO while 1x remains in the enhanced power-save mode.When the 1x system is found, the 1xEVDO service is moved to theco-located 1xEVDO system and normal Hybrid operation isresumed




Hybrid Operation: Initialization State (3)

• Initialization State

– After beginning IS-95/IS-2000 idle state slotted

operation, schedule IS-856 operation to try to acquireand IS-856 System

– Only attempt to acquire IS-856 systems in the PRL that

are identified as “associated” with the current IS-95/IS-

2000 system.

– Radio interface is shared for IS-95/IS-2000 idle state

procedures and IS-856 system acquisition procedures.

– Failure to acquire an IS-856 system after repeated

attempts will cause acquisition attempts to be scheduled

less frequently for power conservation




Hybrid Operation: Idle State

• Idle state procedures on the IS-95/IS-2000air interface are performed

– Paging channel monitoring, registration, idlehandoff

• Idle state procedures on the IS-856 air

interface are performed – Control channel monitoring, session

management, route update, idle handoff

– When no data session exists between the user and the network, the wakeup period is increasedfor power conservation in slotted mode




Hybrid Mode Operation: Idle State (2)

• Periodic system reselection may be

performed on the IS-95/IS-2000 air

interface and the IS-856 air interfaceindependently to attempt to acquire a more

preferred system, in accordance with thePRL




Hybrid Mode Operation: Access State

• IS-95/IS-2000 access state

– Radio interface is dedicated to the IS-95/IS-2000 air

interface for the duration of an access attempt – Radio interface is denied to the IS-856 air interface,

which may be in the initialization, idle, or traffic state

• IS-856 access state – Radio interface is dedicated to the IS-856 air interface

for the duration of an access attempt

– Radio interface is denied to the IS-95/IS-2000 air interface, which may be in the idle state




Hybrid Mode Operation: Traffic State

• IS-95/IS-2000 traffic state

– Radio interface is dedicated to the IS-95/IS-2000 air

interface for the duration of the traffic state – Radio interface is denied to the IS-856 air interface,

which may be in the initialization, idle, or traffic state

– This may cause the IS-856 air interface to return toinitialization state if the Control Channel supervision

timer expires (on AT) or connection to drops at

RN/RNC due to RTCLost (RLL Fade Timer)




Hybrid Mode Operation: Traffic State (2)

• IS-856 Traffic Mode

– IS-95/IS-2000 idle state procedures are performed

during IS-856 traffic state to connect incoming IS-2000services

– IS-95/IS-2000 slotted operation causes periodic tune-

away during IS-856 traffic state for IS-95/IS-2000

paging slot monitoring

– Tune away or connection to IS-95/IS-2000 will cause

the IS-856 connection to be automatically closed by the

network due to fade timer expiration, or control channel

supervision (AT) timer expiration




Hybrid Mode Operation: Traffic State (3)

• Key Notes on 1xEV-DO connection close settings:

– RL Fade Timer, FTC time out, and AT supervision lost

timers all are set at 5 seconds – Any combination of activities which causes the AT to

spend more than 5 seconds on 1x during a tune away

will result in the 1xEV-DO connection closing

– If the AT resets first, then it will become confused, and

reset

– See example due to failed 1x Idle Handoff followed byconnection close




Hybrid Operation: Packet Data Origination

• Attempted on the currently acquired IS-856

system first, if available

• Attempted on the IS-95/IS-2000 if origination on the currently acquired IS-856

system is not successful




Hybrid Operation: Non-Packet Data Origination

• Attempted on the currently acquired IS-

95/IS-2000 system

• Attempted on an alternate IS-95/IS-2000system if it is not successful on the

currently acquired IS-95/IS-2000 system




Non-Hybrid Operation

• Single-system operation

– Provides service on the most preferred available

system in accordance with the PreferredRoaming List and the Mode Preference

– Performs periodic “more preferred” system

reselection if the currently acquired system is

not the most preferred system listed in the PRL

– Only supports incoming services on thecurrently acquired system




Non-Hybrid Operation (2)

• Call Origination

– Attempts to originate packet data service on the

currently acquired system – Attempts to originate service other than packet

data service on an IS-95/IS-2000 system in the

PRL, if none listed in PRL then it will fail




Data Session Handoff

• The terminal will attempt to maintain a dormantdata session across an intersystem air interfacehandoff between IS-2000 and IS-856 systems – The goal is to preserve the existing PPP session state and IP

address.

– This is only possible if the same Packet Data Service Node(PDSN) is shared by both IS-95 and IS-856

– If the PDSN is not shared by IS-95/IS-2000 and IS-856 systems,the PPP session must be renegotiated with the new target PDSN.

– The data session handoff procedure is initiated by the terminal bysending a signaling message to the target system in accordancewith the requirements specified in the IS-2001 and IS-878standards

– Any required PPP renegotiation procedures are initiated by thePDSN.




Intersystem Data Session Handoff Types

• Handoff from an IS-856 system to an IS-

95/IS-2000 system

– Performed when IS-856 service is lost andcannot be reacquired

– IS-856 End of Coverage is Detected (before

service is lost




IS-856 to IS-2000 End of Coverage

• The Hybrid AT can optionally support IS-856 to IS-2000 active data session handoff if end of IS-856coverage is detected, rather than waiting for loss of

service – In IS-856 connected state, the AT computes the metric sum of Ec/Io

for IS-856Active, Candidate, Neighbor Set pilots

– If the sum is less than a predetermined threshold (Default:T_ADD) or

a predetermined period (Default:T_DROP_SEC), then AT checks theEc/Io for 1x pilot

– If IS-2000 pilot Ec/Io is more than a predetermined threshold(Default: T_ADD), then it is determined that IS-2000 coverage isstronger than IS-856

– Data session is handed down from IS-856 to IS-2000 in IS-856connected state

– This algorithm is enabled at compile time, and applies only duringHybrid mode only.




Handoff From an IS-95/IS-2000 System to an IS-

856 System

• Performed when IS-856 service is acquired

and an IS-856 session is successfully

established• Terminal transmits an unsolicited

LocationNotification message containingthe {SID,NID,PZID} from the IS-95/IS-

2000 system




Other Data Session Handoff Scenarios

• The terminal also performs an inter-

BSC/RNC handoff (or transfer) within an

IS-95/IS-2000 system or an IS-856 systemin order to maintain an existing data

session.

– IS-95/IS-2000 inter-BSC handoff

• Performed when the SID, NID, or packet zone

(PZID) changes• Terminal transmits an Origination message with the

DRS bit set to zero




Other Data Handoff Scenarios (2)

• IS-856 inter-BSC handoff

– Performed when crossing an IS-856 subnet

boundary – If a new UATI is assigned and the session

information was retrieved successfully from the

old BSC, no further action is taken – If the session information could not be

retrieved, a new session is egotiated and the

terminal transmits an unsolicitedLocationNotification message containing thelocation information from the previous system

(whether it was 1xEV-DO or 1x)

D t D di t d T i i M d (DDTM)




Data Dedicated Transmission Mode (DDTM)

(Not Currently Supported)

• DDTM is an optional feature which allows hybrid

mode AT to minimize IS-2000 visit durations

• During DDTM operation, the AT: – Will not process any mobile-directed messages

– Will not perform registration

– Will process broadcast messages (Broadcast SMS andOverhead)

– Will not start 1x access probes

– May perform idle handoff or 1x system reselection

– Suitable for data-only terminals or data-focused

applications



Hybrid Mode: What Can Go Wrong

Debugging Issues Related To Hybrid

Mode Operation




If Hybrid Mode Is Operating Correctly

• Normal Tune Away to 1x should take

between 150 and 250 ms at most.




What Can Go Wrong

• If there is poor 1x Signal Quality or No

signal, AT will not return from tune or

return after 5 seconds at whichRLFadeTimer will timeout and drop

connection causing long FTP stalls.

• Pages may be missed during tune away

• Dropped Call rate may be higher than

desirable




Identifying Hybrid Mode Issues

• CAIT is the Best Tool to identify hybrid

mode tune away problems




Using CAIT to debug Hybrid Mode Operation

• Configure log mask as shown in next slide

• Collect the Following data:

– Log File data using Log Mask

– “F3” Mobile Diagnostic Messages

– ! Make sure that the collection times for LogFile and “F3” screens correspond in time

• Normal Debugging data as outlined in

Performance Debug module




Airvana Recommended Logging Mask




Additional Logging Parameters

If you want

GPS PositionCollect

these if in

hybrid

mode

Where to Look for Telltale Signs of Hybrid Tune




Where to Look for Telltale Signs of Hybrid Tune

Away Problems

• Airlink Summary:

• F3 or Event Messages indicating CDMA

resets, idle handoffs, ecio, hashing




Exercise: Look at CAIT Log Files




1xEV-DO Traffic State Hybrid Examples

• Normal Tuneaway mode

• Failed 1xRTT Idle Handoff followed by

1xEV-DO connection release – What can go wrong with hybrid mode when

1xEVDO performance is tied to 1xRTTcoverage



Thank You

Accelerating Access Anywhere

Module12 Hybrid Training

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