1. Issues on Subband Partitioning Document Number: IEEE C80216m-09_1148 Date Submitted: 2009-05-03 Source: HanGyu Cho, Wookbong Lee, Jin Sam Kwak Email: {hgcho, wbong, samji} @lge.com LG Electronics Venue: “802.16m AWD”: IEEE 802.16m-09/0020. ”Call for Contribution on Project 802.16m Amendment Working Document (AWD) Content” Category: AWD-Comments / Area: 15.3.5 DL-PHY Purpose: To discuss issues on subband partitioning and to keep the current DL subband partitoning equation adopted in the current Amendment Working Document 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 located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. Motivation  In the current AWD (C80216m-09_0010r1a), DL subband partitoning rule is already defined.  The subband partitioning rule defined in the AWD keeps the subband alignment while there exist another subband partitioning rule breaking the subband alignment.  This contribution summarizes pros. and cons. of two subband partitioning rules and suggests to keep the current subband partitioning rule defined in the AWD.

3. Allocated subbands aligned with physical subband index  Currently adopted in AWD  In 10MHz, for example,  Allocated subbands aligned with physical subband index  Resource reserved for minibands also aligned with physical subband index 1 23 4 5 67 8 9 1011 12 Physical subband index SAC=3 Allocated subbands Aligned

4. Allocated subbands not aligned with physical subband index  In 10MHz, for example (based on Motorola’s proposal), Physical subband index SAC=3  Allocated subbands not aligned with physical subband index  Resource reserved for minibands also not aligned with physical subband index  Moreover, there is mis-alignment of allocated subbands between different SACs Allocated subbands Not aligned 1 23 4 5 67 8 9 1011 12 SAC=5 Not aligned

5. Concerns on Each Case Related Issue ConcernSolutionRemarks Allocated subbands aligned with physical subband index DRU diversity issue DRU diversity loss when SAC is large - Power control for DRU (especially for A-MAP) - 4 PRU-based channel estimation - TDM-based multiuser diversity 1) Corner case or not? 2) How serious DRU diversity loss? 3) Solution is reasonable or not? Allocated subbands not aligned with physical subband index OL-MIMO precoder cycling In the current AWD, OL- MIMO predocer is defined in the unit of physical subband for simple operation. If subband CRU is not aligned with physical subband index, then, it might conflict with that. ? 1) N2 cycling? :N2 cycling shows poor performance than N1 cycling (1.6% to 11.5% in SE, 3.7% to 22.2% in CE) 2) N2 cycling for DRU/miniband CRU and N1 cycling for Subband CRU? Sounding - How to assign and signal sounding region? - Difficult to apply sounding for both DL and UL - Can cause compleixity and possible performance loss in sounding ? When allocated subbands aligned with physical subband index, sounding region is based on physical subband index and DL/UL reciprocity can be effectively and simply obtained in sounding Ranging How to assign resource for initial ranging? ? When allocated subbands aligned with physical subband index, the physical subband index will be broadcasted to MSs for initial ranging.

6. Sounding Issue  When allocated subbands not aligned with physical subband index, sounding operation becomes complex due to Mis-alignment of allocated subands with physical subband index Mis-alignment of allocated subbands between DL and UL  How to assign and signal sounding region? Based on logical subband index instead of physical subband index? How to assign sounding for DRU region which is not aligned with physical subband index? How to assign sounding for DL subband-CRU region when SAC and USAC are different in TDD? How to assign sounding for both DL and UL when SAC and USAC are different in TDD?  Large number of IoT test cases for sounding UL (SAC=3) DL (SAC=6)

7. Ranging Issue  When allocated subbands aligned with physical subband index, resource for initial ranging is assigned in the unit of subband, i.e., BS broadcasts physical subband index for initial ranging  Any physical subband index can be assigned for initial ranging If physical subband index for initial ranging corresponds to subband- CRU region, then, BS schedules subband-CRU data to subband- CRU region except for the subband assigned for initial ranging If physical subband index for initial ranging corresponds to DRU region, then, tile permutation for DRU is performed within DRU region except for the resource assigned for initial ranging

8. Ranging Issue  When allocated subbands not aligned with physical subband index, how to assign resource for initial ranging?  The possible ways are 1) to physically pre-reserve resource for initial ranging before data resource mapping  Concern) since pre-reserved resource for initial ranging is different between cells, multi-cell resource mapping is impossible for the remaining data resource  Concern) since there is mis-alignment of allocated subbands between subframes with and without ranging, contiguous CRU allocation trhough multiple subframes is impossible  freq. selective diversity gain could be reduced 2) to allocate initial ranging region only in allocated subbands (subband-CRU region)  Concern) subband-CRU region is restrictive 3) to allocate initial ranging region only in DRU region (except for physical subband index the allocated subbands are related to)  Concern) DRU region is also restrictive (especially when USAC becomes large)

9. OL-MIMO Precoder Cycling Issue  When allocated subbands not aligned with physical subband index, N1 cycling is impossible This conflicts with the current AWD  There might exist two solutions N2 cycling (See more details in C80216m-09/0662r1)  Performance loss in localized mode  Miniband can be used for link adaptation mode (MFM 3) as well as diversity mode (MFM 1), but for not aligned case, we can’t use this miniband for link adaptation mode N2 cycling for DRU/miniband CRU while N1 for subband CRU  Result in more complex operation in MS when MS calculates CQI  Anyway, if we adopt one of two solutions, then, DRU diversity loss issue becomes less serious. See the performance results in the following slide [2Tx, 2Rx]N1 granularityN2 granularity Uncorrelated Channel Normalized Spectral Efficiency10098.4 Normalized Cell Edge throughout10096.3 Highly correlated Channel Normalized Spectral Efficiency10088.5 Normalized Cell Edge throughout10077.8

10. DRU Diversity Issue  Investigation on DRU diversity loss when SAC is very large (when allocated subbands aligned with physical subband index)  Consideration on possibility of DRU diversity loss cases Possibie cases  SAC=4 or 5 for 5MHz  SAC=10 or 11 for 10MHz  SAC=22 or 23 for 20MHz The cases seem extreme because  When the number of assigned users become large, DRU size for A-MAP increases  When VoIP users increases, DRU size also increases  In macro cells, when considering cell-edge and/or high mobility users, DRU size increases  In UL, the possibility becomes less The only possibility is when a small number of users with low mobility occupies all the resources in DL in an indoor (or isolated) cell

11. DRU Diversity Issue  Consideration on performance loss DRU (whole, N1): This represents optimal case performance for DRU where all the resource are assigned for DRU Subband (N1): This represents performance of DRU where only one subband is assigned for DRU with N1 cycling (current working assumption) Subband (N2): This represents performance of DRU where only one subband is assigned for DRU with N2 cycling Miniband (N2): This represents performance of DRU where 4 PRUs forming 4 DRUs are distributed across the whole bandwidth mPedB 3km/hrmVehA 30km/hr

12. DRU Diversity Issue  Another solutions to the extreme cases Power boosting for A-MAP Performance improvement based on 4PRU- based channel estimation for the extreme cases TDM-based multi-user diversity (e.g.) one user occupies 8 subband-based CRU+ 12miniband- based CRU instead of 11 subband-based CRU)  Conclusion on DRU diversity loss DRU diversity loss only for extreme cases Even for the extreme cases, DRU diversity loss is not critical

13. Conclusions  Allocated subbands shall be aligned with physical subband index To exploit operational simplicity in OL-MIMO procoder cycling To exploit operational simplicity in sounding To efficiently assign resource for initial ranging and to allow contiguous CRU allocation trhough multiple subframes in UL DRU diversity loss is only for extreme cases and even for the extreme cases, it is not serious and can be solved by some solutions  Keep the current DL subband partitioning rule defined in equations (175) and (177) of the C80216m-09_0010r1a