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Idle mode operation for supporting FemtoCells

Document Number:IEEE C802.16m-08/1433

Date Submitted:2008-10-31

Source:Giwon Park, Rony Yongho Kim, Jin Lee,Kiseon Ryu and Youngsoo Yuk Voice: +82-31-450-1876LG Electronics, Inc. E-mail: {gwpark, ronnykim, jins978, ksryu, sixs}@lge.com 533, Hogye-1dong, Dongan-gu Anyang-si, Gyeonggi-do, Korea*<http://standards.ieee.org/faqs/affiliationFAQ.html>

Venue:TGm SDD: Femtocells

Base Contribution:None

Purpose:To be discussed and adopted by TGm for femtocell SDD text in SDD

Notice:This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who 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 802.16.

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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>.Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.

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Motivation

• IEEE 802.16 system supports Femtocells which operate similar to the currently defined Macro BS. However, a large number of Femtocells can be installed in the network, which may cause inefficiency in idle mode operation.

• CSG (Closed Subscriber Group)– A Closed Subscriber Group identifies subscribers of an operator who are

permitted to access one or more cells of the network but which have restricted access.

• When CSG is considered in femtocell system, efficient Idle mode operation can be designed:– The number of location update which MS performs between femtocells can be

minimized with CSG based paging group.– The paging controller broadcasts the paging message to only the femtocells with

same CSG ID of the MS instead of paging all femtocells within macro paging group.

• We propose a “CSG (Closed Subscriber Group) based paging group”.

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CSG based Paging Group

• Proposed CSG based Paging Group– Paging Area Design considering CSG (Closed Subscriber Group) in femtocell

systems.

– The unit of paging group is same as unit of CSG.

• Advantages of CSG based paging group– Paging controller broadcasts the paging message to only the femtocells with

same CSG ID of the MS instead of paging all femtocells within macro paging group.

– The number of location update which MS performs can be reduced in femtocell systems.

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CSG based paging group structure

Paging Controller

Femto Cell 1

Femto Cell 2

Femto Cell 7

Femto Cell 8

MS moves in femtocell 3 (CSG 1) and does not perform the location update.

MS moves in femtocell 4 (CSG 3) and performs the location update to Macro BS.

MS move into femtocell 1 and performs the location update to

femtocell 1(CSG 1).

Femto Cell 4

MS

Macro CellMacro Cell

CSG 3

Femto Cell 5Femto Cell 6

CSG 2Femto Cell 9

Macro Cell

CSG 1Femto Cell 3

MS’s CSG is CSG 1 and CSG 2

MS moves in femtocell 7 (CSG 2) and performs the location update to femtocell 7 (CSG 2).

MS leaves femtocell 4 coverage and stays in Macro BS paging group.

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Location update and paging for idle mode MS in femtocell systems

• The location update procedure– The MS performs location update when it moves from a macro cell into a

femtocell which is the MS’s CSG.• To reduce the overhead of location update, location update trigger conditions, such as

user speed, should be considered. – Fast moving MS does not perform the location update to femtocell because it is most likely

to pass through the femtocell quickly.

– The MS performs the location update to macro BS when it leaves the femtocell area which allows CSG of MS.

– The MS does not perform the location update when it moves from a femtocell to

a femtocell with same CSG ID of the previous femtocell.

• The paging procedure– The paging controller broadcasts the paging message to only the femtocells with

same CSG ID of the MS instead of paging all femtocells within macro paging group.

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Text Proposal for 802.16m SDD [1]

17. Support for Femtocell

17.x. Idle mode operation for Femtocell Idle mode in Femtocell is intended as a mechanism to provide efficient power saving for the MS

by allowing the MS to become periodically available for DL broadcast traffic messaging (e.g. Paging message) from femto BS without registration at a specific femto BS.

17.x.x. Paging group for Femtocell The paging groups for femtocells are organized based on CSG (Closed Subscriber

Group) to minimize the number of location updates by the MS and paging signaling overhead by the Femto BSs.

17.x.x. Location update process The MS performs location update when the MS detects Femto BS which supports the

MS’s CSG or when the MS moves out of its CSG area. Location update to a femto BS is performed conditionally considering the user status, such as user speed.

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