Understanding LTE Model Internals and Interfaces

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1581 Understanding LTE Model Internals and InterfacesDemo 1: A Planning Study Example• Inputs:• eNodeB with a 3 MHz UL and DL channel• Each UE has an FTP upload/download application• 96 Kbps for both upload and download• The initial planning committee made some advanced calculations and determined that UEs with the followingcharacteristics should be supported:MCS Index092028Number of UEs161631• Requirements:• SLA requirement is that each upload/download should occur in less than 1 second• Planning question:• Can this be done? If not, how many UEs can really be served without violating the SLA?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.32
1581 Understanding LTE Model Internals and InterfacesDemo 1: Planning Approach• First use the admission control module to figure out how many UEs“should” be served• Admission control provides rough estimates only• Scenario: capacity_planning_demo: 53 were admitted using 96 Kbps contract• The initial planning committee was pretty close in their estimate• Results: SLA violated – delays ~ 30 seconds• Reason: The uplink is saturated! Uplink also carries extra signaling overhead(for HARQ ACKs) that we shall study later• Now make the admission criterion stricter• Make the loading factor < 1• First decreased to 0.75 (Scenario: capacity_planning_demo2): Still large delays• At 0.6 loading factor (Scenario: capacity_planning_demo3), stable performancewas observed with 33 admissions• Uplink is pretty close to the saturation point• Hence 33 UEs is the best we can do under the circumstances!• Of course there is R&D• You can improve scheduling algorithms…here is an idea: Schedule on theDownlink only if the probability of getting scheduled on the Uplink is high…thisminimizes wastage on the Uplink and it won’t be the bottleneck!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.33
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Understanding LTE Model Internals and Interfaces

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