Transcript IEEE C802.16m-08/1438r1

Call-back HO Procedure for Reentry Femtocell
Document Number:
IEEE C802.16m-08/1438r1
Date Submitted:
2008-11-05
Source:
Yung-Ting Lee, Hua-Chiang Yin
E-mail : [email protected]
Coiler
Shiann-Tsong Sheu, Chih-Cheng Yang
National Central University (NCU)
Whai-En Chen
National Ilan University (NIU)
Kanchei (Ken) Loa,Yi-Hsueh Tsai, Chun-Yen Hsu,Youn-Tai Lee
Institute for Information Industry (III)
Venue:
IEEE 802.16m-08/040-Call for Comments and Contributions on Project 802.16m System Description Document (SDD), on the topic of
TGm SDD Femtocells
Base Contribution:
IEEE 802.16m-08/003r5
Purpose:
For discussion and approval by IEEE 802.16m Working Group
Notice:
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1
Problem Statement
• Since the femtocell backhaul link may
disconnect from network and reconnect to
network sometimes, the method for
handling the associated MSs to leave and
return the femtocell should be designed in
order to
– continue the services, and
– optimize the network performance.
Handover Trigger
• The WiMAX Forum document “Requirements for
WiMAX Femtocell Systems” states that
– A Femto BS SHALL disable its downlink air interface
transmitter until the connection with the operator’s
network is fully established.
• As the serving femtocell loses the backhaul
connection, it shall command all the associated
MSs to perform handover procedure.
– The handover request signal shall include the reason
code, which is used to notify the MSs to record the
original Femto BS information and wait for any
callback signal.
Call-back handover procedure
• As the femto BS reconnects to the network
again, the femto BS or the network HO
controller initiates the call-back handover
procedure to generate the callback HO
message with the original femto BS ID for
related BS in order to call back those MSs who
have recorded the information of original femto
BS.
• Upon the MS receiving the call-back handover
signal from serving BS, it will try to handover to
the recorded femto BS if the signal quality is
better than the current connection.
Call-back handover procedure
(case 1 : femtocell initiated)
Femto BS
MS
Macro BS/Femto BS
Lost
backhaul link
MOB-HO_REQ
MOB-HO_IND
HO to target BS
Recover
backhaul link
MOB-CallBack_HO_REQ (via backhaul link)
MOB-CallBack_HO_RSP (via backhaul link)
MOB-CallBack_HO_REQ
MOB-CallBack_HO_IND
HO to original BS
Call-back handover procedure
(case 2 : network handover
controller initiated)
Femto BS
MS
Macro BS/Femto BS Network HO
controller
Lost
backhaul link
MOB-HO_REQ
MOB-HO_IND
HO to target BS
Recover
backhaul link
Re-register to network via backhaul link
MOB-CallBack_HO_REQ
MOB-CallBack_HO_REQ
MOB-CallBack_HO_RSP
MOB-CallBack_HO_IND
HO to original BS
Proposed Text
[Add the following sections 17.x.1 “Handover Request
Support” and 17.x.2 “Call-back Handover Support”]
17.x.1 Handover Request Support
As the femto BS loses the connectivity of backhaul
link, it shall send the handover request signal with
reason code to all associated MSs. All the notified
MSs shall perform handover procedure to reassociate with the designated BSs, if any.
17.x.2 Call-back Handover Support
Upon the backhaul connectivity is recovered, the
femto BS and/or the network handover controller may
issue call-back handover signals with femto BS ID to
the related BSs for notifying those MSs, who have
stored the information of femto BS, to handover back.