doc.: ieee 802.11-05/1071r3 submission november 2005 bin wang, zte corporationslide 1 solve frequent...
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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.
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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
Jie Li ZTE Corporation Electronic West Road 3#, Electronic Industry Zone, Xi’an, P.R.China
+86-29-88723148
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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