Understanding LTE Model Internals and Interfaces
Understanding LTE Model Internals and Interfaces
Understanding LTE Model Internals and Interfaces
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
1581 <strong>Underst<strong>and</strong>ing</strong> <strong>LTE</strong> <strong>Model</strong> <strong>Internals</strong> <strong>and</strong> <strong>Interfaces</strong>Appendix E: H<strong>and</strong>ling of UL HARQRetransmissionslte_enb_as_ul_frame_harq_rtx_process()Find all UEs that transmitted at n-8(ACK || max RTX exceeded) && (UEmade a “correct” transmission)*Else if UE made an “incorrect”transmission*ElseFree the HARQ process for newtransmissions.Send a fake ACK to this UE to stopfurther retransmissions <strong>and</strong> mark for“adaptive” retransmissionAttempt synchronous retransmission:lte_enb_as_ul_frame_harq_implicit_rtx_process()Failed due to collision with anotherRTX or RACHFor each open “segment”, attempt adaptiveretransmission:lte_enb_as_ul_frame_harq_explicit_rtx_process()ElseSend NACK. TheUE will retransmitimplicitlyFailedSend a fake ACK to stop retransmissionSucceededSend NACK <strong>and</strong> a grant forRTX with NDI = 0*Incorrect transmission: An incorrect transmission is a consequence of the following scenario: ACK to NACK <strong>and</strong> lost grant fornew data. In this case, the UE retransmits using a previous grant instead of doing a transmission using the new grant. In realsystems, HARQ/PHY can detect this by noting reception of a packet on wrong frequencies.CONFIDENTIAL ─ RESTRICTED ACCESS: This information may not be disclosed, copied, or transmitted in any format without the prior written consent of OPNET Technologies, Inc. © 2010 OPNET Technologies, Inc.86