1. Call-back HO Procedure for Reentry Femtocell IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE C802.16m-09/1305 Date Submitted: 2009-07-06 Source: Whai-En Chen, Shih-Yuan Cheng wechen@niu.edu.tw National Ilan University Kanchei (Ken) Loa, Chun-Yen Hsu, Yung-Ting Lee, Tsung-Yu Tsai, Chiu-Wen Chen loa@iii.org.tw Institute for Information Industry Yang-Han Lee, Yih Guang Jan Tamkang University * http://standards.ieee.org/faqs/affiliationFAQ.html Re: 802.16m Amendment Working Document Call for contributions on “Support for Femtocellcell BS” Base Contribution: IEEE 802.16m-09/0010r2 Purpose: To be discussed and adopted by TGm for the 802.16m Amendment. 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. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. Problem Statement Since the backhaul link of a Femtocell may disconnect from network and reconnect to network sometimes, the proposed method for handling the associated AMSs to leave and return the recovered Femtocell should be designed in order to –continue the services, and –optimize the network performance. 2

3. Handover Trigger The WiMAX Forum document “Requirements for WiMAX Femtocell Systems” states that –A Femtocell BS SHALL disable its downlink air interface transmitter until the connection with the operator’s network is fully established. As the serving Femtocell BS 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 AMSs to record the original Femtocell BS information (e.g., Femtocell BS ID) and wait for any callback signal. 3

4. Call-back handover procedure After the Femtocell BS reconnects to the network, the Femtocell BS notify the network HO controller to initiate the call-back handover procedure for generating the callback HO message with the original Femtocell BS ID in order to call back those MSs who have recorded the information of original Femtocell BS. Upon receipt of the call-back handover signal from serving BS, the AMS will try to handover to the recorded Femtocell BS if the signal quality is better than the current connection. 4

5. Femtocell BS initiates handover when the backhaul link is lost 5

6. Network-initiated Call-back handover procedure 6

7. Proposed Text [Add the following section 15.x “Call-back Handover Support”] 15.x Call-back Handover Support After the backhaul connectivity is recovered, the Femtocell BS should inform the network controller to issue call-back handover signals with Femtocell BSID to the related ABSs for notifying those AMSs, which have stored the information of Femtocell BS, to handover back. 7