Femtocell discovery and access Document Number IEEE C

Femtocell discovery and access Document Number: IEEE C 80216 m-08/1432 Date Submitted: 2008 -10 -31 Source: Jin Lee, Inuk Jung, Ronny Yongho Kim, Kiseon Ryu and Youngsoo Yuk LG Electronics Voice: E-mail: +82 -31 -450 -1856 {jins 978, cooper, ronnykim, ksryu, sixs}@lge. com Venue: TGm SDD: Femtocells Base Contribution: None Purpose: Discuss and adopt by TGm for Femtocell SDD Text 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: <http: //standards. ieee. org/guides/bylaws/sect 6 -7. html#6> and <http: //standards. ieee. org/guides/opman/sect 6. html#6. 3>. Further information is located at <http: //standards. ieee. org/board/pat-material. html> and <http: //standards. ieee. org/board/pat >.

Need to be considered for femtocells n n n Number of Femto Cells within a Macro Cell is too large and broadcasting such large information (e. g. Femto neighbor list) incurs too much overhead. Without a providing neighbor list to an MS, discovery (scanning) of Femto BSs in the vicinity of the MS becomes difficult and requires new procedures for it The scanning problem is critical for initial network entry and handover cases where neighbor Femto BS lists are required Scenarios for network entry and handover cases in Femto Cell need to be defined, since the cell has a heterogeneous entity design (Macro, Femto and Relay BS) with possibly complicated provider right issues (Femto accessible rights) Clear definition of Femto BS types (e. g. open, closed Femto BS, initial accessible BS types) need to be defined

Classification of femtocells n Since a large number of femtocells can be installed by subscribers, in certain scenarios femtocell access shall be restricted to certain subscribers who are authenticated and authorized for exclusive access and related network service. n Additionally, in cases where only closed femto BSs are scanned, where closed Femto BSs only provide service to a closed subscriber group, shall provide a mechanism delivering initial access information (e. g. frequency, BS ID, closed group information) to MSs in order to facilitate their network entry procedure to femtocells. n Femto BS can be classified into 4 types: l Based on bearer connection capability l Open femto BS : Provides bearer connectivity (full network services) to any MS l Closed femto BS : Only provides bearer connectivity to allowed (identifiable) MSs l Based on initial access information capability l Initial access able femto BS : Provides initial access information for any MSs (allowed or not before authentication). Some suggested information are system information of neighboring Femto BSs or CSG ID etc. l Initial access unable femto BS : Not allow to provide initial access information for unauthenticated MSs

Objective and Considered Scenarios n Based on the aforementioned clarifications, we propose Femto BS access procedures that allow efficient network entry and handover to Femto BSs with low overhead n Initial network discovery (Accessible Femto BS discovery) l There are two cases, where an MS powers on and starts to scan the DL l Finds a mixture of Macro and Femto BSs l Finds only Femto BSs n Handover from Macro BS to Femto BS l Serving BS coordinates the handover of MS from Macro BS to a Femto BS by provisioning information of allowed Femto BSs (assuming that mostly closed femto BSs are residing in) to scan for populating a Femto BS neighbor list.

Initial Network Discovery n Two initial access entry procedures (1) If a Femto BS with initial access capability is found, MS makes initial network access to that Femto Cell (2) Else, if only closed Femto BSs with no initial access capability are found, MS makes initial network access (without registration) to Macro BS n Initial access information gathering l l The information gathering procedure for network entry applies to the aforementioned initial access cases (1) and (2) During the initial access, MS transmits the information of found Femto BSs to the initially accessed BS entity (e. g. Macro/Femto BS managing entity) The BS entity populates a list of neighbor Femto cells residing in the vicinity of the MS based on the given extra Femto BS information by the MS The neighbor list, including the Femto Cells and their system information, is given to MS, who tries initial network entry to one of the provided Femto BS within the given list Fig 1. Initial Network Entry to Macro BS-case (2)

Handover n Femtocell discovery during handover (Macro BS Femtocell) (1) Since MS has been authorized by serving BS, serving BS can provide a list of accessible (permission to connect) femto BSs based on the initially given Femto BS information by Macro BS (2) The MS performs channel measurement on the femto BSs included in the list for HO candidate selection n Femtocell entry from connected macro BS l An MS performs femtocell search l The MS reports initially detected femto BS to macro BS l Macro BS may forward them to a femto BS managing entity to query a list of allowed Femto BSs residing in the vicinity of the MS based on the given extra Femto BS. If Macro BS has knowledge about femto BSs, macro BS may response immediately l The list, including the Femto BSs of which have permission to connect is given to MS l The MS scans accessible femto BS candidates based on the received list l The MS requests handover to one of femto BS candidates Allowed Femto BSs (1) MS sends initially detected Femto BS (here it might be FAP 7) Macro Cell FAP 2 Femto BS Managing Entity (3) Provide MS with coordination of which Femto BS to connect to (here a list might include FAP 7, 2, 1 under the allowed group) FAP 7 FAP 3 FAP 1 FAP 6 FAP 4 FAP 5 (2) Populate an allowed Femto NBR list based on the extra Femto BS information given by MS Non-allowed Femto BSs Fig 2. Handover

Proposed Text (1/3) 17. Support for femtocells The Femto BS is classified into two modes in terms of bearer connection capability and initial access capability. � Open Femto BS: Provides bearer connectivity (full network services) to any MS � Closed Femto BS: Only provides bearer connectivity to allowed (identifiable) MSs Initial access able Femto BS: Provides initial access information for any MSs (allowed or not before authentication). Some suggested information are system information of neighboring Femto BSs or CSG ID etc. � Initial access unable Femto BS: Not allow to provide initial access information for unauthenticated MSs

Proposed Text (2/3) 17. 1 Network Entry The IEEE 802. 16 m system shall support applicable procedures for entering and registering a new MS at a Femto BS. The network facilitates the initial network discovery procedure by providing network information (details are FFS) to the MS prior to full registration including authentication to a BS entity. An overall procedure of the network entry would be as follows. The MS scans the DL for any neighbor BS entities (Macro/Relay/Femto). Among the searched BSs, the MS distinguishes them and prioritizes them in terms of network entry candidates. The MS further prioritizes Femto BSs by their types (Open/Closed and initial access able/unable types). Based on the scan result, the MS makes network entry to the best BS candidate.

Proposed Text (3/3) 17. 2 Handover to Femto BS Macro BS facilitates femtocell scanning through the information on allowed femtocells for MS in order to save MS power and avoid unnecessary scanning. MS provides initially detected femtocell information to macro BS. This is to provide information that the macro BS utilizes for generating a HO candidate list, which includes a list of neighbor Femto BSs that the MS is able to establish connection (BSs with the same CSG ID). The HO candidate list is given to the MS by the macro BS. Upon receiving the list of HO candidate BSs, the MS scans the HO candidate BS list and selects the most preferable BS for HO.