1. IEEE 802.16m Identifying Femtocell BS and its Accessibility Document Number: IEEE C80216m-09_0068 Date Submitted: 2009-01-05 Source: Ying Li, Zhouyue Pi, Baowei Ji, Email: yli2@sta.samsung.com Phone: +1-972-761-7903yli2@sta.samsung.com Farooq Khan, Jaehee Cho Samsung Electronics Venue:IEEE Session #59, San Diego, CA. Base Contributions: Re: Call for Comments on IEEE 802.16m SDD 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 (1/3) IEEE 802.16m System Requirements – Shall support CSG (Closed Subscriber Group) – Shall allow dense deployment of large number of Femtocells – Shall support preferred access and handover of MS’s to their designated Femtocell BSs Some operations (such as Cell Selection, Network RE-/Entry) could be different for Femtocells and macro cells, and for CSG and OSG (Open Subscriber Group) Femtocells. Therefore, an MS may need to differentiate Femtocells from macro cells, CSG from OSG, or one CSG from the other CSG.

3. 3 Motivation (2/3) Accessibility of a BS – Macro BS: accessible to all MSs – OSG Femtocell BS: accessible to all MSs – CSG Femtocell BS: only accessible to its authorized MSs, though open to all MSs for emergency access. An MS needs to determine whether it is allowed to access a CSG Femtocell – CSG BS may not be accessible to many MSs, the chance that an MS cannot access to a CSG BS is large, so the accessibility should be checked early. – The number of SCH symbols for cell IDs may not be large enough to differentiate a potential large number of CSG Femtocells. – PBCH can be a good place to offer information for MS to check accessibility. – Consider methods avoiding using expensive PBCH payload.

4. 4 Motivation (3/3) CSG ID – to ease the management – Several Femtocell BSs could belong to a same CSG entity, which have the same group of authorized MSs. – Benefits of using a common CSG ID for this set of BSs  An MS can determine the accessibility of a Femtocell BS the registered CSG ID, otherwise, the MS may have to keep a list of all the Femtocell BSs of this CSG.  To ease the management at the paging controller, and avoid location update when the MS is moving inside the CSG.

5. 5 Proposed Scheme (1/2) BS Operation: – Macro BS, OSG Femtocell BS and specific CSG Femtocell BS are differentiated by scrambling the CRC of a P-BCH burst with different masks (called s-code herein). – Send: M + (CRC Xor s-code), where M is the P-BCH message, CRC is produced from M, s-code is a scrambling code.  All macro BSs uses s-code 0x0000, i.e., no scrambling  All OSG Femtocell BS uses a special s-code (e.g. 0x0001)  Each CSG Femtocell BS uses the s-code corresponding to its assigned CSG ID – Notes: there is no change to macro BS operation

6. 6 Proposed scheme (2/2) MS Operation: having acquired SCH, the MS starts decoding a P-BCH by Step 1. decode the message (M^) Step 2. calculate the CRC^ Step 3. calculate s-code^ = CRC^ Xor (CRC Xor s-code) – If s-code^ = 0x0000, it is a macro BS – If s-code^ = 0x0001, it is an OSG Femtocell BS – Otherwise, it is a CSG Femtocell BS with CSG-ID equals s-code^ For its accessible BSs, MS may further acquire unique BS ID in network entry or handover procedures.

7. 7 Pros and cons Pros – The operation of macro BS is not affected at all because of the zero scrambling – All BSs use the same pool of SCH preambles – Not overhead in either P-BCH or S-BCH – Shortening the network access time compared with using S-BCH payload for carrying CSG-ID or BS ID. Cons – Xor operation with CRC, but the computation cost is negligible.

8. 8 Comparing with other Proposals ProposalMacro or Femto OSG or CSG femto CSG IDProsCons This Proposal Scrambling the CRC of a P-BCH burst with different masks. - Macro BS unchanged. - same pool of SCH. - Not overhead in BCH - Fast BS classification - Extra Xor computation Proposal 1SCH preamble partition N/A [identify using BS ID] - faster BS classification- smallest SCH pool for each BS set - slower CSG identification using BS ID to check CSG accessibility - MS has to keep a long list of all accessible CSG Femtocell BSs Proposal 2SCH preamble partition 1 bit in P- BCH CSG-ID field in S- BCH - no PHY layer change for BS and MS operations - smaller SCH pool for each BS set - extra P-BCH and S-BCH overhead - Slower CSG identification using S- BCH Proposal 3SCH preamble partition 1 bit in P- BCH N/A [identify using BS ID] S-BCH may keep unchanged for Femtocells -smaller SCH pool for each BS set - extra P-BCH overheard - slower CSG identification using BS ID to check CSG accessibility - MS has to keep a long list of all accessible CSG Femtocell BSs

9. 9 Proposed text 17.X Femtocell BS Identification Macro BS, OSG Femtocell BS and CSG Femtocell BS are differentiated by scrambling the CRC of a P-BCH burst with different masks. No macro BSs does scrambling, i.e., the mask is 0x0000. All OSG Femtocell BSs use the same mask (e.g. 0x0001). Each CSG femtocell BS uses the mask corresponding to the CSG ID.

10. 10 SDD text changes in 11.7.2 11.7.2.2.1 Primary Broadcast Channel (PBCH) and Secondary Broadcast Channel (SBCH) (80216m-08_003r6, page 91, line 27) The Primary Broadcast Channel (PBCH) and the Secondary Broadcast channel (SBCH) carry essential system parameters and system configuration information. The PBCH is transmitted every superframe. Scrambling CRC of PBCH with different masks is used to differentiate macro BS, Open-Subscriber- Group (OSG) Femtocell BS, and Closed-Subscriber-Group (CSG) Femtocell BS. The SBCH may also be transmitted. When present, SBCH may be transmitted over one or more superframes. The information contents of PBCH and SBCH is FFS 11.7.2.1.1 Synchronization channel requirements (80216m-08_003r6, page 88, line 1, item 5) Cell ID set: The cell ID set is the set of unique SCH symbols for differentiating between among macrocell/femtocell/, sector/, and relay transmitters.