MCS Adaptation and Feedback Mechanism in 802 16

MCS Adaptation and Feedback Mechanism in 802. 16 m MBS IEEE 802. 16 Presentation Submission Template (Rev. 9) Document Number: IEEE S 80216 m-08/1151 Date Submitted: 2008 -09 -17 Source: Hung-Yu Wei, Ching-Chun Chou Department of Electrical Engineering, National Taiwan University Chun-Yen Wang, Richard Li, ITRI Voice: E-mail: [Telephone Number (optional)] hywei@cc. ee. ntu. edu. tw f 95921098@ntu. edu. tw Chun. Yen@itri. org richard 929@itri. org Venue: MAC aspect of enhanced MBS; in response to the TGm Call for Contributions and Comments 802. 16 m-08/033 for Session 57 Base Contribution: IEEE C 80216 m-08/1151 Purpose: To be discussed and adopted by TGm for use in the IEEE 802. 16 m 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 >.

Introduction: MCS Adaptation in MBS • Modulation and Coding Scheme (MCS) adaptation and feedback mechanism in 802. 16 m MBS – MCS adaptation for high-rate transmission • Not just using the lowest data rate – Applying MCS adaptation to MBS • Feedback mechanism for MCS state reporting Most Robust MCS Good Channel 64 QAM SS 1 16 QAM QPSK BPSK MBS Group SS 2 SS 3 => Should use QPSK

MCS Adaptation and Feedback • MCS configuration for MBS – Initialization of MBS – Periodic MCS level re-selection – Dynamic adaptation • Fast adaptation for more robust MCS • The adaptation depends on CSI report from MS – Full probing MCS Feedback • Positive reporting • Collect Max-min information – Fast feedback • Negative Reporting • Reduce rate if at least one MS complain SS 1 SS 2 SS 3 MBS Group

Fast Feedback with Negative Reporting • An MS finds the current wireless channel condition is unable to support current MCS. • BS applies more robust MCS • Negative reporting => more robust transmission – When 1 or more MS sends negative reporting – Busy Tone Negative reporting • Busy Tone NACK – Negative-preamble reporting • NACK-preamble

Full Probing with Positive Feedback • We need a feedback mechanism to MCS selection – Initialization – Periodic re-selection • Procedures – MS measures downlink CSI and appropriate MCS • Report CSI info to BS – The BS might configure that all MS could report positive reporting periodically. • Or on-demand polling for MCS full probing is used. • For the cumulative info of the positive reporting – Trigger the positive MCS adaptation for MSs in the MBS group.

Joint Signaling of MBS and MCS Adaptation • Using MBS polling for MCS adaptation is natural – However this results in additional signaling overhead. – Signal the ACK scheme in MBS and MCS adaptation simultaneously! • For example, we could use 2 codes for MBS – Code (I): NACK with no MCS change • Retransmission with no rate adjustment – Code (II): NACK with MCS change • Retransmission & rate adaptation • More codes could be applied for other combinations of MBS and MCS adaptation. – 4 codes for NACK/ACK & MCS changes

Summary • MBS would require MCS adaptation – Adequate way of MCS adaptation could give better MBS Qo. S • Positive / Negative reporting for MCS adaptation • Joint signaling could be done with reliable MBS and MCS adaptation – Joint feedback for efficient signaling

Proposed Text 11. 9. 1. 6. 1 E-MBS feedback for MCS selection MCS feedback mechanism is needed for MCS adaptation in E-MBS. Fast feedback mechanism could be used for quick adjustment of MCS. Full probing mechanism could be used for initialization and accurate MCS selection. MCS adaptation and reliability feedback could be jointly applied for efficient feedback signaling. 11. 9. 1. 6. 1. 1 Fast Feedback for MCS adaptation in E-MBS Fast feedback for MCS adaptation could be used for timely adjustment to a more robust MCS transmission in E-MBS. When an MS's CSI cannot support current MCS, the fast feedback trigger the downgrading of MCS to a more robust MCS.

Proposed Text 11. 9. 1. 6. 1. 2 Full Probing for MCS selection in E-MBS Full probing is needed for selecting the appropriate MCS for robust transmission in EMBS. MS measures the downlink CSI, determines the appropriate MCS, and reports to the BS. The full probing for MCS is conducted during the initialization phase of an EMBS service. The full probing could be conducted periodically in time-varying wireless environment. 11. 9. 1. 6. 1. 3 Joint Feedback for MCS adaptation and Acknowledgement in E-MBS Joint feedback for MCS adaptation and Acknowledgement is design to provide efficient signaling mechanism for reliable transmission and robust MCS selection in Joint Feedback for MCS adaptation and Acknowledgement in E-MBS. CDMA codes could be used for joint feedback for MCS adaptation and packet reception condition. Joint signaling feedback could be used to indicate Acknowledgement (ACK) or Negative Acknowledgement (NACK) along with MCS adjustment request.