Unified Ranging Structure for Femtocell BSs Document Number

Unified Ranging Structure for Femtocell BSs Document Number: C 80216 m-0811 Date Submitted: 2009 -04 -24 Source: Yih-Shen Chen, Peikai Liao and Paul Cheng Media. Tek Chie-Ming Chou, Yung-Han Chen and Frank Ren ITRI E-mail: yihshen. chen@mediatek. com E-mail: chieming@itri. org. tw, frank_ren@itri. org. tw Venue: IEEE Session #61, Cairo, Egypt Base Contribution: This is base contribution Re: IEEE 802. 16 m-09/0021, “Call for Comments on Project 802. 16 m System Description Document (SDD)” - CR to SDD: Chapter 15 Support of Femtocell Purpose: For TGm members’ 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: <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 >. 1

Ranging Channels in 802. 16 m • In current SDD, there are three types of ranging channels: – Non-synchronized ranging channel • Initial ranging – MS adjusts its frequency/timing/power with its potential serving cell during initial network entry • HO (handover) ranging – MS adjusts its frequency/timing/power with its target cell during handover – Synchronized ranging channel • Periodic ranging – MS adjusts its frequency/timing/power with its potential serving cell – BR (bandwidth request) ranging • MS sends out its transmission intention and requirements 2

Discussion on Synchronization Issue in Femtocell • After DL synchronization with femtocell SCH, the maximal offset of a MS is within synchronization requirement, given the cell coverage is 30 meters at most – RTD: (2*30)/(3*108) 0. 2μs • Synchronization requirement: – For any duplexing, all SSs shall acquire and adjust their timing so that all UL OFDMA symbols arrive time coincident at the BS to a accuracy of ± 25% of the minimum guard-interval or better (8. 4. 10. 1. 2, Rev 2/D 8) – Wi. MAX profile requirement: • Question: do we still need the differentiation, given shortrange? 3

Proposed Ranging Structure for Femtocell: Unified Ranging Structure • Single unified ranging channel configuration for all the ranging purposes – The PHY of the ranging channel consists of preamble and message part (preamble+MSG PHY; i. e. , BR PHY) • Benefit: – High spectral efficiency » No guard channel is required » Few subcarriers are required (ex: 18) – High bandwidth efficiency » BW request for RNG-REQ is sent along with preamble » MS ID may be sent with preamble for UL ranging if a specific femto-only ID is assigned (CSG scenario) 4

Example (Preamble+MSG PHY) Contention-based ranging code Ranging message 5

Procedure of Initial Ranging in Femtocell (a) if the MSG part is correctly decoded (b) if the MSG part is not correctly decoded 6

HO Ranging to Femtocell • Bandwidth request as well as HO preamble sequence are sent to femtocell target at once – Shorten handover interruption time 7

Performance Analysis of the Proposed Unified Ranging Channel • The timing offset of initial ranging can be absorbed by CP – Short coverage (≦ 30 m) • Low collision probability – Small population number (≦ 10) – ex: for 10 Vo. IP users, the arrival rate is 0. 02/frame • For OUG scenario, femto-BS can allocate more ranging opportunities to reduce the collision probability 8

Performance Analysis of the Proposed Unified Ranging Channel ~ spectral efficiency • Assume PRBS code is reused for 16 m initial ranging – The total occupancy resources will be 144 x 6 – The saving for unified ranging channel is 88. 9% per subframe • 1 - [ (6*6*3)/(6*6*3+144*6)] = 88. 9% • There might be more than thousand femto. BS installments – FDM/TDM spectral utilization is required • Spectral saving would be critical in femtocell deployment 9

Implementation Impact • No modification is required on ranging PHY structure • No two analog filters are required – In macrocell deployment, CP length is different for initial ranging channel and BR ranging channel • Re-define some parameters in the quick access message – One or few access-IDs • Current only 12 out of 19 are defined for flow IDs – BW-REQ ID may be ignored or apply a pre-configured common ID • ID may be pre-configured in CSG scenario – 2 -bit BW field can be re-defined as BW requirement for RNGREQ 10

Conclusion • Unified ranging channel for femtocell can provide – Better spectral efficiency – Easier deployment – Shorter access latency 11

Text Proposal [Adopt the following text modification into section 15. 4. 3 of P 802. 16 m SDD] BR ranging channel is configured as a unified ranging channel for Femtocell BS to accommodate all types of ranging purposes. The PHY structure of BR ranging channel is identical as macro BS. AMS can send ranging preamble with associated flow ID inside the quick access message to differentiate the ranging purposes. In order to optimize the radio resource utilization and functional capability in Femtocell BS, the Femtocell BS and other different kind of BSs should have different attributes of ranging codes. The Femtocell BS ranging codes may be assigned for different Femtocell BS operation, and some ranging codes may be known only to the special group of MSs. 12

Appendix 13

Unsynchronized Ranging Channel for Macrocells 14

UL Ranging Procedure for 802. 16 e • RNG-REQ size mismatch problem [1]: – Multiple TLVs are optional in RNG-REQ BS has to figure out an appropriate size by itself – This is an IOT issue, identified by Samsung in Wi. MAX TWG [1]080717_TWG_Samsung_r 4_allocation_of_RNG_REQ_size. doc 15