Understanding LTE Model Internals and Interfaces

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1581 Understanding LTE Model Internals and InterfacesAppendix C: What if Your SchedulerDoesn’t Produce the “Next Queue”• Case study: My scheduler already decided all the UEs to schedule andall the associated RBs…I also know how many blocks are given toeach RB…how do I interface my system to OPNET?• This problem can be solved as follows:• Step 1: Overwrite the output of lte_sched_support_next_q_get() with yourown (c_rnti, rb_id), so that frame generator will service your queue insteadof letting the callback choose one for you• When you are done, assign the variable return_ q_id the valueLTEC_SCHED_Q_INVALID for termination• Step 2: Overwrite the calculation of the variables “num_alloc_blocks_ptr”and “small_alloc_blocks_ptr” in the functionlte_enb_as_dl_frame_gen_blocks_and_bits_compute()• “Small allocation blocks” is important to know for subframes withspecial channels such as primary/secondary synchronizations and BCCH.• That’s pretty much it!• As long as you have produced a “correct frame” (i.e. not allocating moreresources than what actually exist), things will work fineCONFIDENTIAL ─ 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.84
1581 Understanding LTE Model Internals and InterfacesAppendix D: Handling of DL HARQRetransmissionslte_enb_as_dl_frame_harq_rtx_process()Find all UEs that should have receivedand processed their acknowledgementsby now: (UEs that transmitted at n-8, andall NACKed UEs that got “pushed” tothe current SF). Find the HARQ contextof the UE.ACK || max RTX exceededElseFree the HARQ process for newtransmissions.Examine if resources are available onPDSCH, PDCCH and conditionallyPUSCH:lte_enb_as_dl_harq_rxmt_dci_obtain()All resources availableElsePerform retransmission in the currentsubframeFind a future subframe for retransmission:No other HARQ process for this UE shouldbe scheduled for retransmission in that SF.lte_enb_as_async_dl_harq_rtx_perform()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.85
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Understanding LTE Model Internals and Interfaces

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