Understanding LTE Model Internals and Interfaces

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1581 Understanding LTE Model Internals and InterfacesUL Frame Generator at the eNodeB• Very similar to the DL frame generator• Called in the same 3 phases• Uses the same scheduler and callback functions• Does not deal with RLC, since it is the UE’s job• Only creates grants, and understands how many bits could fill the spaceallocated in a grant – The eNodeB knows the UE’s needs from BSRs• Conditionally reuses some grants created by the DL Frame Generator forHARQ acknowledgment purposes• In case the scheduler does not choose such UEs, the UL frame generator isaware that 1 allocation block would eventually be given to the above UE.• Does not use the space allocated to the control channels, such as PUCCH andRACH• Function: lte_enb_as_ul_frame_generate()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.52
1581 Understanding LTE Model Internals and InterfacesUplink “Segments”PUCCHSynchronousHARQ RTXRACHSynchronousHARQ RTXPUCCHA typical 5 MHz Uplink Subframe1 block4 blocks6 blocks2 blocks• For every “contiguous segment”, UL framegenerator is run separately• In this example, no UE can get more than 6allocation blocks, although a total of 13 blocks arefree• A UE scheduled in one segment cannot bescheduled again in another segment due toSCFDMA• When all UEs in one segment are scheduled,their bursts are also placed in that segment• Grants created for DL HARQ ACKs can go inany segment in the end. It is guaranteed that ULframe generator will leave enough space toallocate them.• lte_enb_as_frame_ul_frame_for_harq_tx_generate() to enter the whole UL frame generationprocess• lte_subframe_free_prb_segments_create() tofind the number of free segments• lte_subframe_free_prb_segments_next_seg_get() to find the dimension of next free segment (interms of start index and number of alloc.Blocks)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.53
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Understanding LTE Model Internals and Interfaces

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