1. Network Assisted Femtocell BS Detection Document Number: C80216m-09/0838 Date Submitted: 2009-04-24 Source: Fang-Ching (Frank) Ren, Yan-Xiu Zheng, Chie Ming Chou, Yung-Han Chen E-mail:frank_ren@itri.org.twfrank_ren@itri.org.tw ITRI Venue: IEEE Session #61, Cairo, Egypt Base Contribution: N/A Re: Comments on 802.16m SDD (802.16m-08/003r8) Purpose: Discussion and Approval 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. 2 Motivation To support handover between macro cell and femtocell, fast cell search on femtocell BSs is necessary for MS. However, the number of femtocells overlaid within a macro cell may be large. –The method to announce femtocells in a broadcating neighborhood list is not efficient. –Also, femtocell may not be deployed everywhere. The process of femtocell search should be performed in right time (i.e., the MS is really in coverage of femtocells) for a limited number of candidates.

3. 3 SDD description in 802.16m-08/003r8 15.2.1 PHY level cell identifier Femtocell BSs and macro BSs are differentiated using Cell IDs, which shall be obtained from the A-PREAMBLE. It enables MSs to quickly identify cells types, avoid too frequent handover attempts into and out of a Femtocell BS, and avoid performing unnecessary network entry/re- entry.

4. 4 Proposal I: Femtocell Existence Detection IEEE 802.16m Synchronization structure –Hierarchical structure composed of PA-Preamble and SA-Preamble –PA-Preamble: Less sequences: less than 20 Less complexity for sequence matching Cell type identification in PA-Preamble for IEEE 802.16m except for OSG and CSG femtocell BS –SA-Preamble Physical Cell identification Large number of sequences: at least 512 Huge effort and complexity for cell scan OSG/CSG Femtocell existence can be detected based on PA-Preamble detection.

5. 5 Macro Camp on suitable macro cell Cell Type Identification CSG Detect PA-Preamble OSG Proposal I: Femtocell Existence Detection Concept of Cell Identification Identify a SA- Preamble from macro cell OSG Femtocell Identification Camp on suitable OSG Femtocell CSG Femtocell Identification Camp on suitable CSG Femtocell Cell Identification on SA- Preamble may also be differentiated to prevent unnecessary identification attempts.

6. 6 Proposed Text

7. 7 Proposal II: Femtocell Identification Based on PA-Preamble can be used to distinguish signal from macro BSs, OSG Femtocell BSs, and CSG Femto BSs, –a MS may start Femtocell identification after OSG/CSG Femtocell PA-Preamble detected. –The candidate set of SA-Premable can be further reduced for cell identification (ID).

8. 8 Proposal II: Femtocell Identification Ranging-based femtocell BS identification procedure –Step1: MS sends an preserved ranging code in a preserved raging slot. –Step2: Femtocell BS responses an localized Identification Code. –Step3: MS sends a selected ranging code to reply the one of BS –Step4: The selected Femtocell BS send Cell ID message, e.g. Cell ID, SA-Preambe sequence, etc (1) Preserved ranging code (2) Localized BS identification codes (3) Selected initial ranign code (4) Cell ID message Cell search based on Cell ID message

9. 9 Proposal II: Femtocell Identification Example for supporting Macro to Femtocell HO –In subclause 15.5.1, SDD said “The network provides certain system information to MSs for supporting handover between a macro BS and a Femtocell BS” Reserved ranging code (said C 0 ) and reserved ranging slot in Femtocell. The channel allocation for transmission of “Femtocell Localized ID codes”. Femtocell Localized ID codes (D 1 ~D N ) and corresponding ranging codes (C 1 ~C N ). The channel allocation for the selected Femtocell BS to send Cell ID message.

10. 10 Proposal II: Femtocell Identification Example (Cont’d) –Step 0: MS detects the PA- Preamble from Femtocells. –Step 1: MS send ranging code C 0. –Step 2: Femtocells response localized ID code D 1,D 2, D 3, and D 5 to the MS. –Step 3: The MS sends ranging code C 1 due to localized ID code D 1 was detected and selected. –Step 4: Femtocell D1 sends Cell ID message. D1 D2 D3 D4 D5 D4 Macro BS

11. 11 Proposed Text