1. Handover in Femtocell IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE C80216m-09_0800 Date Submitted: 2009-04-24 Source: Raunak Maheshwari,Yongseouk Choi,Namsuk Lee,Sookjin Lee Voice: +82-42-860-5679 ETRI E-mail: {raunak,choiys,namsuk,sjlee}@etri.re.kr 138 Gajeongno, Yuseong-gu, Daejeon, 305-700, KOREA * http://standards.ieee.org/faqs/affiliationFAQ.html Venue: IEEE 802.16 Session #61, CAIRO, EGYPT Base Contribution: None Purpose: To discuss and adopt the proposed text in the next revision of the 802.16m 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. 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. Background Current Handover Process –Serving BS periodically broadcasts neighbor list (MOB_NBR-ADV) which contains information about the neighboring macrocell BS. –Each BS updates its neighboring Macrocell BS using backbone. –Due to limited number of neighboring BS, this list is manageable & efficient Femtocell –Low Powered BS installed indoors by subscribers. –Expected Numbers: Tens of thousands –In such scenario, neighbor list based handover mechanism to femtocell will become inefficient due to List management overhead Possibility of inaccuracy of information Large scanning time for MS Signal outside coverage area is weak –Scanning based on information in neighbor list may not produce results as detection of femtocell BS outside its coverage area will be difficult Need of Handover scheme not based on neighbor list in case of handover to femtocell BS MOB_NBR-ADV Backbone This proposal does not change procedure followed in macrocell to macrocell handover which uses the neighbor list advertisements by the service macro BS. Huge Femtocell Deployment – Every individual indoor premise can have one femtocell BS installed

3. Handover in Femtocell Femtocell Detection –MS is able to detect femtocell by analyzing A-Preamble. Handover from Macrocell to Femtocell –In the femtocell coverage area (indoor), the power of signal received from the macrocell will be lower than the power of signal received from the femtocell. –The HO should be triggered on the power of the signal received from serving macrocell BS going below a threshold level. –When the HO is triggered, MS shall first try to detect the femtocell by channel estimation process. –If MS detects femtocell, the process of HO to the femtocell BS shall be initiated. –If MS does not detect femtocell, the normal HO procedure (macrocell to macrocell) shall be initiated which uses the neighbor list MSSBSTFBS Channel Estimation Handover Initiation Candidate Group Association Neighbor Advertisement (Unicast) Fast Re-entry This scheme is not dependent on neighbor list for handovers to femtocell The neighbor list broadcasted by macrocell BS will only contain information about neighboring Macrocell BS which may be used by MS while handover from macrocell BS to another macrocell BS is performed.

4. Handover from femtocell Once outside the coverage area of a femtocell, MS can be in –coverage area of another femtocell –coverage area of macrocell. MS shall search for a femtocell BS first –If femtocell BS is found, HO to femtocell BS shall be initiated –If femtocell BS is not found, HO to macrocell shall be initiated HO Trigger FBS Found? HO to FBSHO to MBS Whenever HO is triggered, MS shall first search for FBS, if found, HO to FBS shall be performed, otherwise HO to MBS shall be performed YesNo

5. Proposed text Text in red color to be removed Text in blue color to be added ---------------------------------------------------Start of Proposed Text---------------------------------------------------------- 15.5.1 Handover from Macro BS to Femtocell BS The network provides certain system information (e.g., carrier frequency of the Femtocell BS, and mapping information of overlay macro BSs and Femtocell BSs) to MSs for supporting handover between a macro BS and a Femtocell BS. An MS may cache this information for future handover to the specific Femtocell BS. HO should be triggered based on certain criteria, such as signal strength, the proximity of MS to the Femtocell BS, and /or loading, etc. The macro BSs shall not broadcast the system information of the neighbor CSG Femtocell BSs in its neighbor list. When the trigger conditions for handover are met, the MS will first search for Femtocell BS. If Femtocell BS is found, handover from Macrocell BS to the Femtocell BS shall be performed. If Femtocell BS is not found, normal handover procedure shall be followed. Handover from Macrocell to Femtocell will follow the steps given below 1.The MS will perform channel estimation to know the Cell IDs of the nearby Femtocells 2.After the MS has detected femtocell(s) by analyzing A-Preamble, it will send message to SBS which will include the cell IDs of the Femtocells 3.The SBS will choose one or more femtocell BSs from the group depending on the system parameters and Access Type (OSG, CSG). 4.The SBS will form association with the chosen femtocell BSs. 5.The SBS will send a message to MS to inform it about the one or more chosen femtocell BSs. This message will include parameters which will help perform an optimized HO. 6.The MS would then perform optimized handover.

6. Proposed Text Contd… 15.5.2 HO from Femtocell BS to Macro BS or other Femtocell BS The set of macro BSs and/or Femtocell BSs that are the potential handover targets from the current serving Femtocell BS are provided by the network or cached in the MS. The serving Femtocell BS broadcasts or unicasts this list of neighbor accessible Femtocell BS and/or macro BSs to the MS. The handover process between Femtocell BS and macro BS or between Femtocell BS and Femtocell BS is the same as defined in section 10.3.2 with the exceptions as defined in this subsection When the trigger conditions for handover are met, the MS will first search for another Femtocell BS. If another Femtocell BS is found, handover procedure to femtocell BS as described in 15.5.1 shall be followed. If femtocell BS is not found, handover from Femtocell BS to Macro BS shall be followed. -------------------------------------------------------End of Proposed Text----------------------------------------------------