HARQ Architecture (Protocol and Timing) in IEEE m Document Number: IEEE S802.16m-08/411 Date Submitted: Source: Doo-hyun Sung, Hyungho Park, HanGyu Cho Voice: LG Electronic Inc. LG R&D Complex, 533 Hogye-1dong, Dongan-gu, Anyang, , Korea * Venue: IEEE m-08/016r1 - Call for Contributions on Hybrid ARQ Base Contribution: IEEE C802.16m-08/411r2 Purpose: To be discussed and adopted by TGm for use in the IEEE m SDD Notice: This document does not represent the agreed views of the IEEE 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 Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and. Further information is located at and.

HARQ Support in 16m  In legacy system, HARQ is supported as an optional feature  Drawbacks of HARQ support in legacy system  1. Not applicable to some transmissions such as RNG-REQ message transmission MS has to restart from the CDMA code transmission  2. Rather complicated & wasteful DL/UL MAP structure Adverse effect to increase DL control channel capacity  Propose to mandate HARQ operation in DL/UL unicast packet transmissions

HARQ Retransmission Mode (Signaling Aspect)  HARQ retransmission mode (signaling aspect) can be categorized into two mechanisms  1. Control Signaling Based Retransmission Referred as Asynchronous/Adaptive HARQ mode  Synchronous/Adaptive HARQ mode becomes a subset, if HARQ channel ID is defined After decoding an additional MAP (for retransmission), MSs perform retransmission according to it  2. No Control Signaling Based Retransmission Referred as Synchronous/Non-adaptive HARQ mode After detecting NACKs, MSs perform retransmission at pre-determined subframe

Downlink HARQ Retransmission  Propose to support “Control signaling based retransmission” in DL HARQ  Asynchronous/Adaptive HARQ  Why?  Available to increase BS’s scheduling gain via additional control signaling Fully exploit MSs’ feedback information  Available to avoid collisions with MBS subframes or persistent scheduling

Uplink HARQ Retransmission  Propose to support “No control signaling based retransmission” in UL HARQ  Synchronous/Non-adaptive HARQ  Why?  Hard to achieve scheduling gain from additional control signaling due to unexpectable interference from other cells and FFR mechanism It would be better for MSs to perform retransmission without additional control signaling

Number of UL HARQ Channels & Related Parameters  Number of UL HARQ channels  To support synchronized retransmission timing, the number of UL HARQ channels should be defined  MSs perform retransmission N th UL subframe, where N denotes the number of UL HARQ channels, from the subframe where the initial transmission was done  DL&UL ACK/NACK delay  Due to supporting subframe concept in 16m, DL&UL ACK/NACK delays become varied In legacy system, single values of DL& UL ACK/NACK delay would be enough

Number of UL HARQ Channels & Related Parameters (cont’) System Configuration UL MUXingFrame Configuration The number of UL HARQ Channels 16m onlyN.ADDDDDDDU1 16m onlyN.ADDDDDDUU2 16m onlyN.ADDDDDUUU3 16m onlyN.ADDDDUUUU4 16m onlyN.ADDDUUUUU5 16m onlyN.ADDUUUUUU8 16m onlyN.ADUUUUUUU11 16m onlyN.ADDUUDDUU4 ………… 16e/m co-exTDMDDDDDUUU1 16e/m co-exTDMDDDDDUUU2 16e/m co-exTDMDDDDDUUU2 16e/m co-exTDMDDDDDUUU1 16e/m co-exTDMDDDDUUUU2 16e/m co-exTDMDDDDUUUU1 16e/m co-exFDMDDDDDUUU3 16e/m co-exFDMDDDDDUUU4 16e/m co-exFDMDDDDUUUU5 ………… † D U: 16m, D U: 16e †† Propagation delay + Data processing interval = 2 TTIs Table 1. The number of UL HARQ channels

Number of UL HARQ Channels & Related Parameters (cont’) System Configuration UL MUXing Frame Configuration Subframe Index m onlyN.ADDDDDDDU m onlyN.ADDDDDDUU m onlyN.ADDDDDUUU m onlyN.ADDDDUUUU m onlyN.ADDDUUUUU333 16m onlyN.ADDUUUUUU33 16m onlyN.ADUUUUUUU3 16m onlyN.ADDUUDDUU3535 …………………………… 16e/m co-exTDMDDDDDUUU43 16e/m co-exTDMDDDDDUUU33 16e/m co-exTDMDDDDDUUU433 16e/m co-exTDMDDDDDUUU543 16e/m co-exTDMDDDDUUUU44 16e/m co-exTDMDDDDUUUU54 16e/m co-exFDMDDDDDUUU333 16e/m co-exFDMDDDDDUUU33 16e/m co-exFDMDDDDUUUU33 …………………………… † D, U: 16m, D, U: 16e †† Propagation delay + Data processing interval = 2 TTIs Table 2. UL ACK delay for DL HARQ transmission

Number of UL HARQ Channels & Related Parameters (cont’) Table 3. DL ACK delay for UL HARQ transmission System Configuration UL MUXing Frame Configuration Subframe Index m onlyN.ADDDDDDDU3 16m onlyN.ADDDDDDUU33 16m onlyN.ADDDDDUUU333 16m onlyN.ADDDDUUUU m onlyN.ADDDUUUUU m onlyN.ADDUUUUUU m onlyN.ADUUUUUUU m onlyN.ADDUUDDUU3535 …………………………… 16e/m co-exTDMDDDDDUUU4 16e/m co-exTDMDDDDDUUU55 16e/m co-exTDMDDDDDUUU44 16e/m co-exTDMDDDDDUUU3 16e/m co-exTDMDDDDUUUU44 16e/m co-exTDMDDDDUUUU3 16e/m co-exFDMDDDDDUUU555 16e/m co-exFDMDDDDDUUU655 16e/m co-exFDMDDDDUUUU6554 …………………………… † D U: 16m, D U: 16e †† Propagation delay + Data processing interval = 2 TTIs

Conclusion  We propose the following:  HARQ operation shall be supported for DL/UL unicast packet transmissions  DL HARQ retransmission shall be performed in Asynchronous/Adaptive manner BS signals additional control signalings for retransmission to MSs  UL HARQ retransmission shall be performed in Synchronous/Nonadaptive manner MSs perform retransmissions without any additional control signaling  The number of UL HARQ channels and DL&UL ACK/NACK delay need to be identified

Text Proposal for SDD u.u HARQ support HARQ operation shall be supported for DL/UL unicast packet transmission in both BS and MS. v.v Downlink HARQ operation DL HARQ retransmission is performed along with an additional control signaling for retransmission. This would be referred as Asynchronous/Adaptive HARQ. After decoding the control signaling, MSs receive retransmitted packets according to it. Through the additional control signaling, retransmission timing and transport format such as RB allocation, modulation, etc., could be changed in each retransmission. Table w.w shows UL ACK delay after which BS awaits ACK/NACKs from MSs corresponding to DL HARQ transmission. Table w.w UL ACK delay for DL HARQ transmission [ Insert Table 2 in slide 8] Start of the Text

Text Proposal for SDD x.x Uplink HARQ operation UL HARQ retransmission is performed without an additional control signaling for retransmission. This would be referred as Synchronous/Nonadaptive HARQ. MSs perform retransmissions at pre-determined subframe after identifying NACKs from the BS. Associated with the number of HARQ channels, the UL subframe wherein an MS performs the retransmission is implicitly determined; the Nth UL subframe from the initial tx. subframe. The value of N denotes the number of HARQ channels in Table y.y. Table z.z shows DL ACK delay after which MSs await ACK/NACKs from the BS corresponding to UL HARQ transmission. Table y.y The number of UL HARQ channels [ Insert Table 1 in slide 7] Table z.z DL ACK delay for UL HARQ transmission [ Insert Table 3 in slide 9] End of the Text