Understanding LTE Model Internals and Interfaces

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1581 Understanding LTE Model Internals and InterfacesDL Frame Generator Block DiagramFrameGeneratorSchedulerSet Scheduler callbacks (dependingupon the pass)Reset the scheduler (erase transientmemory)Makes group1 currentQ 1Q 2Q 3Q 4Q 5Q 6Group 1 Group 2 Group 3Don’tterminateINVALID Q iGet (Q i , R i ) R i being therecommended bits to serveVALID Q iCalculate N i , the maximum number ofincremental allocation blocks that canbe given to this queue and S i , thecorresponding bits that can be servedAsk the RLC module to return one ormore RLC PDUs not exceeding (S i –MAC overheads)Recalculate N’ i
1581 Understanding LTE Model Internals and InterfacesUnderstanding How to Interface to the DLFrame Generator• Entry function: lte_enb_as_frame_dl_frame_for_harq_tx_generate()• Pass 1: Called for all queues. For GBR queues, only a maximum of contract bits served.• Pass 2: Called only for the GBR queues. Excess traffic in GBRs served.• Pass 3: Called if PDCCH gets congested before PDSCH.• In order to prevent creating new control channel elements, all unserved UEs areblocked, and remaining PDSCH resources are distributed only to the served UEs.• At the start of the framing, set scheduling callbacks:• lte_sched_support_q_selection_proc_set()• Procedure that finds the “next queue”• lte_sched_support_bit_selection_proc_set()• Procedure that “recommends” bits to be taken from the queue’s buffer• That’s pretty much it! Interface reduced potentially to 2 lines only• Frame generator in turn calls (until resources remain, or buffers are nonempty):• lte_sched_support_next_q_get(): Gets the queue ID (crnti, RB) and the “recommendedbits”• Frame generator has the ability to determine termination, reset the scheduler system, potentiallyset different callbacks each time, exclude/include queues in the scheduling process etc!• We recommend you leave the frame generator undisturbed!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.47
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Understanding LTE Model Internals and Interfaces

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