November 2005

Bin Wang, ZTE Corporation

Slide 1

doc.: IEEE 802.11-05/1071r3

Submission

Solve Frequent Handover Requirement

Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document 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 Standards publication; 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 to reproduce 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 802.11.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart.kerry@philips.com> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>.

Date:2005-11-01

Name Company Address Phone email Bin Wang. ZTE Corporation Electronic West Road 3#,

Electronic Industry Zone, Xi’an, P.R.China

+86-29-88723141

Wang.binxa @zte.com.cn

Feng Li ZTE Corporation Electronic West Road 3#, Electronic Industry Zone, Xi’an, P.R.China

+86-29-88723130

li.feng8@zte.com.cn

Jie Li ZTE Corporation Electronic West Road 3#, Electronic Industry Zone, Xi’an, P.R.China

+86-29-88723148

li.jiexa@zte.com.cn

Authors:

November 2005

Bin Wang, ZTE Corporation

Slide 2

doc.: IEEE 802.11-05/1071r3

Submission

Abstract

This document suggests the requirement to solve frequent handover of STAs in ESS for Wireless Network Management.

November 2005

Bin Wang, ZTE Corporation

Slide 3

doc.: IEEE 802.11-05/1071r3

Submission

Agenda

• Introduction• Frequent handover illustration• The harm of frequent handover• Current of commercial equipment• Proposed text

November 2005

Bin Wang, ZTE Corporation

Slide 4

doc.: IEEE 802.11-05/1071r3

Submission

Introduction

• The meaning of frequent handover:– Because of the movement of STA or the change of

wireless circumstance and network condition, STAs in the overlapped range of two or more APs will handover from one to another and check back just after a little while.

– In a fixed period, STA may in this kind of “check out and check back” status continuously;

– So called “Ping-Pang” effect.

November 2005

Bin Wang, ZTE Corporation

Slide 5

doc.: IEEE 802.11-05/1071r3

Submission

Frequent handover illustration

22000mm

1337

5m

m

AP1

AP2

AP3STA1

November 2005

Bin Wang, ZTE Corporation

Slide 6

doc.: IEEE 802.11-05/1071r3

Submission

Frequent handover illustration

time

AP

of

ST

A1

time

Loa

d

time

AP

of

ST

A1

timeL

oad

AP1AP2AP3

handover

0:0:0 AP1->AP20:0:2 AP2->AP10:0:3 AP1->AP30:0:5 AP3->AP20:0:8 AP2->AP1

……

With Frequent handover Without frequent handover

November 2005

Bin Wang, ZTE Corporation

Slide 7

doc.: IEEE 802.11-05/1071r3

Submission

The harm of frequent handover

• Most part of frequent handover is unnecessarily– STA decided to handover just because of the signal

strength.– Sometimes, The service STA can acquire from APs

involved in frequent handover has no substantively difference, or unluckily, becoming worse.

• High risk of application interrupt– The time consumed during once handover will up to

100ms even with the 80211r help, it is unacceptable for some time urgent application. (e.g. VoWLAN)

– The 2-layer router information must updated as soon as possible to keep the application continuous.

November 2005

Bin Wang, ZTE Corporation

Slide 8

doc.: IEEE 802.11-05/1071r3

Submission

The harm of frequent handover 2

• Increase the AP’s management overhead– The APs involved in frequent handover must

management the whole process of STA’s movement, including disassociation, deauthentication, authentication, association……

• Deteriorate the radio environment– The AP’s resources will be wasted on this kind of

unnecessarily handover.

• Disarrange the load balancing schedule– Maybe the STA moved to the direction inconsistent

to the AP’s load balancing status.

November 2005

Bin Wang, ZTE Corporation

Slide 9

doc.: IEEE 802.11-05/1071r3

Submission

Current of commercial equipment

• Use window protocol to control frequent handover.– Only when the target AP’s signal is higher than that of current

AP’s over the threshold can the STA initiate a DISASSOCATION.– Advantages:

• Signal strength means link quality.• Can eliminate the arbitrariness in a degree.

– Disadvantages:• Signal strength doesn't means STA can acquire equivalent service in

new AP.• The value of threshold is hard to select.• Can not ensure efficiency.• May cause confusions in roaming.

• Load balancing can not completely eliminate frequent handover.– Current load balancing mechanism can lead to frequent

handover sometimes.

November 2005

Bin Wang, ZTE Corporation

Slide 10

doc.: IEEE 802.11-05/1071r3

Submission

Possible approach for frequent handover avoid

• Distinguish different kind of handover ;• During handover, do FH detect;

– Evaluate the history of signal strength;– Evaluate the transmit power;– Evaluate the load information;– Evaluate the channel quality;– Evaluate the location information;– Evaluate the handover window status;

• Record the FH result, for further judgments.

November 2005

Bin Wang, ZTE Corporation

Slide 11

doc.: IEEE 802.11-05/1071r3

Submission

Frequent handover avoid illustrator

STA APs

Handover report

FHdetect

FHavoid

Handover req

FHcontrol

STAHandover

policy

APsHandover

policy

Handover rsp

Handover policy update

November 2005

Bin Wang, ZTE Corporation

Slide 12

doc.: IEEE 802.11-05/1071r3

Submission

Possible FH Avoid Policies

• Time_varying wireless channel environment– radio circumstance– client's movement

• Requirement of load balancing– user number or traffic– traffic’s level, QoS

• Transmit power adjustment or advanced power control

• Support dynamic channel select• And so on

November 2005

Bin Wang, ZTE Corporation

Slide 13

doc.: IEEE 802.11-05/1071r3

Submission

Proposed text

• TGv should consider to solve the problem of frequent handover in wireless network management, supply detect/avoid/control mechanism.

• TGv should take the following factors into account when solve frequent handover:– Signal strength– Single direction channel caused by AP’s different emission

power from different vendors or different model.– Network resources or load information

• To include Frequent Handover Control as requirement item to TGv work list

• To include Frequent Handover Control as additional item in the TGv Objectives document

November 2005

Bin Wang, ZTE Corporation

Slide 14

doc.: IEEE 802.11-05/1071r3

Submission

Poll for TGv Objectives

• Should TGv take frequent handover as a new requirement ?

• Yes:• No:• Abstain:

November 2005

Bin Wang, ZTE Corporation

Slide 15

doc.: IEEE 802.11-05/1071r3

Submission

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