Handoff Schemes Overview and Guidelines for Handoff Procedures in 802.16

IEEE 802.16 Presentation Submission Template (Rev. 8.3)Document Number:

IEEE S802.16sgm-02/24Date Submitted:

2002-09-19Source:

Avi Freedman Voice: +972-3-5101128Hexagon system Engineering Ltd. Fax: +972-3-51033312 Kaufmann st. E-mail: avi@hexagonltd.comTel-Aviv, 68012, Israel

Zion Hadad Voice: +972-3-9528440Runcom Technologies Ltd.2 Hhacoma st E-mail: zionh@runcom.co.ilRishon le-zion, Israel

Venue:Meeting #21, Cheju, South Korea

Base Document:IEEE C802.16sgm-02/24 <http://ieee802.org/16/mobile/C80216sgm-02_24.pdf>.

Purpose:Disccussion

Notice:This document has been prepared to assist IEEE 802.16. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in thisdocument is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release:The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standardspublication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others toreproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16.

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Handoff Schemes Overview andGuidelines for Handoff Procedures in

802.16

Avi Freedman

Hexagon

Zion Hadad

Runcom

3

Purpose

• Survey handoff schemes in cellular andWLAN networks

• Present guidelines for handoff supportin 802.16

• Offer handoff support within theframework of the OFDMA PHY

4

Definition

• Handoff - a basic mobile network capabilityfor dynamic support of terminal migration

• Handoff Management - the process ofinitiating and ensuring a seamless andlossless handoff of a mobile terminal from theregion covered by one base station toanother base station

5

Handoff Basics

• Measurements – UL and DL same andneighbor BS’s

• Decision – when and where to hand themobile terminal over

• Execution – transferring traffic and control toanother BS

6

Types of Handoffs

• Location of the HO

Execution

Mobile InitiatedHO

NetworkInitiated HO

Decision

MobileEvaluated HO

NetworkEvaluated HO

Measurements

MobileNetwork

7

Types of HO

• Network Elements Involved

IntraSector

Intracell

InterLayer

Intercell

Intersystem

8

Types of HO

• Number of active connections– Hard handoff: 1 connection active at a

time, “break before make”

– Soft Handoff: >1 connection at a time

– “make before break”

9

Types of HO

• Types of data transferred– Circuit Switched

– Packet Switched

10

Requirements for HO

• Latency: The time required to effect the handoffshould be appropriate for the rate of mobility of themobile terminal, as well as the nature of datatransferred.

• Scalability: The handoff procedure should supporthandoffs within the same cell, between different basestations in the same or in different networks

• Minimal drop-off and fast recovery• QoS maintained or re-negotiatied• Minimal additional signaling

11

Handoff Implementation

• Cellular SYSTEMS– 2G (GSM)

– 3G (UMTS)

• Wireless LAN– 802.11

– HIPERLAN 2

• Mobile IP

12

The Cellular Network

• MS – Mobile Station

• BTS – Basestation TransceiverStation

• BSC – Basestation Controller

• MSC – Mobile Switching Center

• HLR – Home Location Register

• VLR – Visitor Location Register

• EIR – Equipment Identity Register

• AuC – Authentication Center

BTSMS BTS BSC

Base Station

MSC

EIR

HLR VLR

AuC

OtherMSC

ExternalNetworks

Other

VLRs

BTS

13

GSM

• Types (network elements)– Intracell HO– Inter-Cell HO within the same BSC– Intra MSC HO– Inter MSC HO

• Types (function location)– Mobile initiated– Network initiated, mobile assisted

14

GSM (cont.)

• Measurements of the BroadcastChannel on a free time slot

• Decision according to:– Minimum acceptable performance

power control is preferred over HO

– Power budget algorithms

HO is preferred over power control

15

UMTS

• Intra-system Handover:• Intra-frequency HO

• Inter-frequency HO

• Inter-system HO• Different radio access technologies (e.g.

UMTS and GSM/EDGE)

• Different radio access modes (e.g.FDD/WCDMA and TDD/TD-CDMA)

16

UMTS (cont.)

• Soft Handoff– For intra frequency HO

– Active set controlled by the Radio NetworkController, based on mobile measurements

• Hard handoff– For inter-frequency HO, multi-layer

– Network evaluated, based on mobilemeasurements

17

UMTS (cont.)

• Compressed Mode can be used to provide“peeping window” in other frequencies

• Mobile required to monitor up to 32 BS in oneor two frequencies

• Broadcast channel and Primary CommonPilot channels are used by the HO process

• Measurements are filtered with 50-200µssymbols- for 60km/h mobiles

18

802.11

STA- Station

AP – Access Point

DS – Distribution System

BSS- Basic Service Set

ESS- Extended Service Set

ESS

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802.11 – Mobility Types

• No Transition– Static

– Local movement

• BSS Transition

• ESS Transition

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802.11 Process

• Use of the re-association DS service

• Handoff is mobile initiated, hard handoff

• Beacon frames are used forsynchronization and measurements

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HIPERLAN 2

• Consists of a number of Access Pointsand Mobile Terminals

• Centrally controlled:– In centralized mode: controlled by an AP

– In Direct mode: by one MT serving as CC

• Handover is restricted to business andpublic applications

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HL2- Function and Capabilities

• Functions:– MT Absence– Handover, determined by the CC (Radio Resource

Controller

• Capabilities– Association of MT to logically distinct subnetworks– Informing the core network of the changes of the

population associated to a subnetwork– Monitoring of radio conditions for handover and

for informing user and hosting core network of theprevailing radio/traffic conditions

23

HIPERLAN 2 (cont.)

• HL2 shall support:– Roaming between access networks– Continuous while in motion

• Rate of movement supported:– 10 m/s linear– 180 deg/sec rotation

• Packet loss or delay- to be handled byhigher layers

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Mobile IP

• A solution to direct IP packets to a user connectedvia different access points

Home region

HomeAgent

Foreign region

ForeignAgent

Care-of-address

Mobile Terminal

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Handoff Aware Wireless Access Internet InfrastructureHAWAII

• Reduces network load by handling local HO withinlocal area

Mobile Terminal

Routing information

Mobile Terminal

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Terminal Independent Mobile IPTIMIP

• The network is aware if a terminal hasmobile IP capability

• Basic parameters of the the mobile– Obtained by the network at an offline

registration process

– MIP is run by the network gateway ifmobile lacks MIP capability

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Cellular IP

• Uses layer 2 information

• Predicts possible handover

• Triggers Level 3 procedures beforeconnection

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Guidelines for 802.16 HO Procedures

– Mobile initiated

– Mobile evaluated

– Network initiated

– Network evaluated

– Intra sector

– Intra cell

– Inter cell

– Inter layer

– Inter system

Provide HO support of higher layers

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Requirements for 802.16 HO Procedures

• Measurements of signals of neighboringbase stations, in the same or in otherfrequencies

• Broadcasting of base station information

• Enabling intra-frequency handoff

• Enabling soft and softer handoff

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Requirements for 802.16 HO Procedures

• Means for authentication and serviceverification

• Mechanisms for inter-mode handoveramong the various 802.16 PHYs and theiroptions

• Support Mobile IP in both IPv4 and IPv6

• Provide signal strength and otherindications for Cellular IP support