ACK and NACK Feedback Schemes for HARQ Operation

ACK and NACK Feedback Schemes for HARQ Operation IEEE 802. 16 Presentation Submission Template (Rev. 9) Document Number: IEEE S 80216 m-08/294 Date Submitted: 2008 -05 -05 Source: Hung-Yu Wei, Ching-Chun Chou Department of Electrical Engineering, National Taiwan University Voice: E-mail: [Telephone Number (optional)] hywei@cc. ee. ntu. edu. tw f 95921098@ntu. edu. tw Chun-Yen Wang, Chun. Yen@itri. org. tw Richard Li , richard 929@itri. org. tw ITRI, Venue: IEEE 802. 16 m-08/016 - Call For Contribution on Project 802. 16 m System Description Document (SDD), shoot for “Hybrid ARQ (protocol and timing)” topic Base Contribution: IEEE C 80216 m-08/294 r 5 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 • We proposed ACK/NACK schemes for HARQ – NACK schemes • Parallel NACK • Busy Tone NACK • NACK-preamble NACK – ACK schemes • Parallel ACK / Polling ACK / Periodic ACK • The proposed schemes could provide reliable transmission and flexibility to the system – Combined scheme may be more useful.

Parallel NACK Scheme • Each MS is assigned a non-interfering radio resource block – NACK messages could be sent to the BS in parallel • The transmission is done within the same frame. – The radio resource block could be • Time slot/Frequency channel/CDMA code channel/ OFDM channel/Other wireless channel • Multiple NACK could be sent simultaneously. • It would consume more resources for single data block’s retransmission.

Example: Parallel NACK Scheme • BS transmits data to MS (1, 2, 3, 4, 5). • MS 1 & MS 3 didn’t receive the data block. – The NACK is transmitted using the Parallel NACK scheme to the BS – MS 2, 4, 5 don’t need to trigger NACK. • The radio block is left unused. Unused radio resource for (MS 2, 4, 5) NACK by MS 1 BS data NACK by MS 3 BS re-tx data

Busy Tone NACK Scheme • Busy Tone is a predefined sequence/code to be transmitted at a given time. – The tone is sent using preconfigured wireless channel • MS transmits Busy Tone to the BS to indicate NACK – When an MS does not receive the anticipated data block • BS would receive one or more Busy Tone for NACK – BS knows at least one MS does not receive the data block. – BS retransmits the missing data block.

Example: Busy Tone NACK Scheme BS Downlink to MS 1, MS 2, MS 3 data 1 data 2 data 3 Re-transmission NACK MS 1 rx rx MS 2 rx rx MS 3 rx rx rx NACK

NACK-preamble NACK Scheme • NACK-preamble: a predefined sequence – Indicating that the NACK IE is transmitted successively after the NACK-preamble. – If BS receives one or more preamble, then BS knows that there are data loss for the transmission. • NACK IE (Information Element) – The actual NACK message. – Containing detail information of NACK. • Node ID/HARQ parameters and configurations/ CSI/Other helpful information for data retransmission. • The NACK-preamble indicates data loss. – Even the NACK IE may be corrupted or collide with each other.

Example: NACK-preamble NACK Scheme • There are two MS using the NACK-preamble NACK scheme. – The NACK IE might collide between the MS – The BS could still get the NACK-preamble. • This would initiate the retransmission. • Successful reception of NACK IE gives more retransmission information. Collision of IE Still get NACKpreamble NACK IE 1 NACK IE 2 Received NACK IE

ACK Schemes • Parallel ACK scheme – Each MS is assigned a unique radio resource block for ACK. • Actually, the block could be ACK or NACK. – ACK could be transmitted in parallel to the BS. • Polling ACK scheme – The MS only transmits ACK when BS polls it. – The ACK message could contain the reception condition of multiple data blocks • Within the polling period. • Periodic ACK scheme – The BS configures the ACK sequence for the MS. – The MS sends the ACK periodically • According to the BS’ setting for the ACK period. • The ACK could still contain the reception condition.

Integrated Schemes • The NACK/ACK schemes could be applied simultaneously. – Better flexibility – The cooperation might yield better results. • The pros might be conserved and cons might be relieved • The integrated scheme is favored as: – Immediate ACK aids fast retransmission. • Lost data are reported immediately. – Delayed ACK reduces signaling overhead. • It contains cumulative feedback info and saves the number of signaling messages. – The combination of the two schemes would give more flexibility and better performance.

Example: Busy Tone + Periodic ACK • The periodic ACK might suffer from larger retransmission delay. • Busy Tone NACK’s simple design gives less reception condition information. • The integrated scheme would relieve the disadvantages while still preserve the advantages. Time period for periodic ACK Periodic ACK with cumulative info BS data busy tone NACK BS data Retransmission Periodic ACK with cumulative info BS data time No busy tone NACK is transmitted

Conclusion • We proposed ACK/NACK schemes for HARQ operation. • These schemes could be used under different HARQ requirement. – Channel state and other information could also be collected. • Integrated schemes could provide even better results.

Proposed Text • 10. x. x ACK and NACK Design Acknowledgement (ACK) and Negative Acknowledgement (NACK) are crucial for HARQ operation. The design criterions for the ACK and NACK could be considered from the following aspects. • 10. x. x. 1 Acknowledgement Feedback Latency The timing of transmitting ACK and NACK could be immediately after the data retransmission, delayed for certain period, or the integration of the two schemes. For integrated ACK/NACK, multiple types of ACK/NACK are allowed for flexibility. 10. x. x. 2 Channel Access and Allocation for Acknowledgement The ACK and NACK mechanism should be able to operate on specific preconfigured channels. The number of preconfigured wireless channels could be the same as the node number or less. If the BS receives one or more acknowledgement indicating that certain data block is lost, the BS should trigger the retransmission for the specific data. •