May 28, 2015 - spectrum as a Supplemental Downlink to LTE technology operation using ... ANY PARTICULAR PURPOSE, AND ALL
Qualcomm Technologies, Inc.
LTE-U Technology and Coexistence May 28th, 2015
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Disclaimer and Copyright Notification Copyright © 2015 LTE-U Forum Companies: Alcatel-Lucent, Ericsson, LG Electronics, Qualcomm Technologies Inc., Samsung Electronics, Verizon. All rights reserved. This document provides initial information related to Long Term Evolution (LTE) technology operation using unlicensed spectrum as a Supplemental Downlink to LTE technology operation using licensed spectrum. All information provided herein is subject to change without notice. The information provided herein was considered technically accurate by the LTE-U Forum Companies at the time the documents were initially published, but LTE-U Forum Companies disclaim and make no guaranty or warranty, express or implied, as to the accuracy or completeness of any information contained or referenced herein. LTE-U FORUM COMPANIES DISCLAIM ANY IMPLIED WARRANTY OF MERCHANTABILITY, NON-INFRINGEMENT, OR FITNESS FOR ANY PARTICULAR PURPOSE, AND ALL SUCH INFORMATION IS PROVIDED ON AN “AS-IS” BASIS. Other than as explicitly provided below, LTE-U Forum is not providing any licenses under any intellectual property of any kind owned by any person (whether an LTE-U Forum Company or otherwise) that may be necessary to access or utilize any of the information contained herein, including but not limited to any source materials referenced herein, and any patents required to implement or develop any technology described herein. It shall be the responsibility of the developer to obtain any such licenses, if necessary. LTE-U Forum disclaims liability for any damages or losses of any nature whatsoever whether direct, indirect, special or consequential resulting from the use of or reliance on any information contained or referenced herein. Permission is given to reproduce this document in its entirety solely for the review, analysis, and implementation of LTE-U. Use of this document for any other reason without the permission of LTE-U Forum Companies is explicitly prohibited. ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Outline • Overview of LTE-U coexistence algorithms design − Channel selection, CSAT and OSDL − How to coexist with Wi-Fi BSSs within and outside CCA-ED
• Lab & OTA results for coexistence above and below CCA-ED − Different traffic applications − Wi-Fi/Wi-Fi, Wi-Fi/LTE-U fairness study
• Demos − Stress room demo with three different Wi-Fi AP vendors − OTA on-campus demo with two different Wi-Fi AP vendors ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Introduction • Throughout the LTE-U design and testing, coexistence has been a main principle that has been studied thoroughly with different applications, devices, and deployment models • We couldn’t rely just on 802.11 spec due to divergence by many implementations − Wi-Fi benchmark based on testing of Wi-Fi AP and chip vendors with the highest market shares
• What is presented here is Qualcomm’s design in accordance with LTE-U Forum spec − The spec provides guidelines and testing scenarios to be passed but doesn't dictate specific implementations − This is obviously not the only way for implementation
• The design covers a larger set of scenarios than those mandated by spec
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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LTE-U Coexistence Solutions State Diagram Initialization & Configuration
Channel Selection (ChS) Triggered by channel switch condition
CSAT Enabled
LTE-U UE added (or high traffic load)
No LTE-U UE (or low traffic load)
OSDL (LTE-U Off) ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Channel Selection Wi-Fi AP UE3 Wi-Fi AP UE2 STA Co-located LTE-U SC/Wi-Fi AP
UE1
Wi-Fi AP
LTE-U and WiFi NL(Network Listening) assisted with UE reporting LTE & Wi-Fi measurements and CQI/BLER to detect hidden nodes
LTE-U SC
LTE-U SC
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Channel Penalty Function
δ1
Wi-Fi AP Beacon RSSI Measurements, and whether channel is primary or secondary
LTE-U UE WiFi Measurements over RRC
× δ2
× δ3
LTE-U NL Measurements
×
+
Total Channel Penalty
δ4 LTE-U UE RRM measurements
× δ5
LTE-U UE CQI/ BLER
×
• Different penalty weighting for different interference sources, e.g. WiFi primary channel has higher penalty compared to secondary channel • Quantized penalty for robustness to measurement errors and to reduce bias due to outliers • Measures % of coverage area with some desense due to other AP interference • Built in mechanisms to detect and mitigate frequent channel switching ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Channel Selection- Summary 1. 2. 3. 4.
• • • • •
Has to be both during initial boot up as well as dynamically during operation Choose the cleanest channel in general If possible avoid primary channels of WiFi If possible avoid channels occupied by other LTE-U operators and choose channel occupied by the same LTE-U operator (Forum coexistence spec 6.1.2) Channel selection is aided by Small Cell NL(Network Listening) and/or UE measurements Can be done through passive or active scan- our design uses active Scanning typically happens every few seconds Channel selection can happen at any time, but typically within 10s seconds Channel selection is conservative in that it considers any found beacon to be active − Taking channel loading in consideration is for further optimization ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Carrier Sense Adaptive Transmission (CSAT) • A TDM transmission pattern on the LTE-U SCell with TCSAT cycle
− This pattern leverages existing LTE carrier aggregation MAC signaling ( MAC control element for activating and deactivating an SCell) − This pattern is triggered based on transmissions measured from Wi-Fi APs
• Wi-Fi medium utilization measurement is performed during LTE-U SCell OFF time, to adjust ON/OFF duty cycle − Adaptive trade-off between LTE-U and other systems (e.g. Wi-Fi) performance.
Gating Cycle (TCSAT) LTE-U ON
LTE-U OFF
Ton /Toff adaptive
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Wi-Fi Medium Utilization (MU) Estimation Input to CSAT loop • Wi-Fi MU monitoring is done where all LTE-U small cells are required to turn 5GHz RF transmission OFF in this period − guarantees overlapping OFF time across neighbor LTE-U small cells for sensing Wi-Fi
• Sensing time is selected sufficiently large to allow the co-located Wi-Fi NL module for reliable MU monitoring of the operating channel. MU is also averaged across multiple observations • Wi-Fi NL decodes the preamble of any WiFi packet detected during this time and records its corresponding received signal strength indicator (RSSI), duration in μs (or NAV), modulation, coding scheme (MCS) and source/destination address
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Wi-Fi MU Estimation Averaged weighted observed activity over a monitoring window • The algorithm divides packets into different categories based on their attributes and each category is assigned a weight • If the packet is found to be an ACK, or CTS, and the preceding data packet is not detected, the packet is classified as generated from a hidden node and count the packet as full duration (nominal value of around 4msec) • Let Wi and Di denote the weight and duration of i-th detected packet during MU monitoring time, assume that K packets were detected during the monitoring time. The instantaneous MU is computed as 𝐾𝐾
1 � 𝑊𝑊𝑖𝑖 × 𝐷𝐷𝑖𝑖 𝑀𝑀𝑀𝑀(𝑛𝑛) = 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀
• WiFi medium utilization is filtered as follows:
𝑖𝑖=1
𝑀𝑀𝑀𝑀 𝑛𝑛 = 𝛼𝛼𝑀𝑀𝑀𝑀 𝑀𝑀𝑀𝑀 𝑛𝑛 + 1 − 𝛼𝛼𝑀𝑀𝑀𝑀 𝑀𝑀𝑀𝑀 𝑛𝑛 − 1 where filter coefficient 𝛼𝛼𝑀𝑀𝑀𝑀 could be set small for smaller monitoring time to allow more averaging
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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CSAT Adaptation Outer loop to decide on Ton in a given CSAT cycle • CSAT algorithm will increase/decrease 𝑇𝑇𝑂𝑂𝑂𝑂 if MU is below/above a certain threshold
• CSAT adaptation is done as follows:
𝑇𝑇𝑂𝑂𝑂𝑂 𝑛𝑛 + 1 = m𝑖𝑖𝑖𝑖 𝑇𝑇𝑂𝑂𝑂𝑂 𝑛𝑛 + ∆𝑇𝑇𝑈𝑈𝑈𝑈 , 𝑇𝑇𝑂𝑂𝑂𝑂,𝑚𝑚𝑚𝑚𝑚𝑚
where
𝑖𝑖𝑖𝑖 𝑀𝑀𝑀𝑀 𝑛𝑛 < 𝑀𝑀𝑀𝑀_𝑇𝑇𝑇𝑇𝑇1
𝑇𝑇𝑂𝑂𝑂𝑂 𝑛𝑛 + 1 = 𝑇𝑇𝑂𝑂𝑂𝑂 𝑛𝑛 𝑖𝑖𝑖𝑖 𝑀𝑀𝑀𝑀_𝑇𝑇𝑇𝑇𝑇1 ≤ 𝑀𝑀𝑀𝑀(𝑛𝑛) ≤ 𝑀𝑀𝑀𝑀_𝑇𝑇𝑇𝑇𝑇2 𝑇𝑇𝑂𝑂𝑂𝑂 𝑛𝑛 + 1 = m𝑎𝑎𝑎𝑎 𝑇𝑇𝑂𝑂𝑂𝑂 𝑛𝑛 − ∆𝑇𝑇𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 , 𝑇𝑇𝑂𝑂𝑂𝑂,𝑚𝑚𝑚𝑚𝑚𝑚 𝑖𝑖𝑖𝑖 𝑀𝑀𝑀𝑀 𝑛𝑛 > 𝑀𝑀𝑀𝑀_𝑇𝑇𝑇𝑇𝑇2
− 𝑇𝑇𝑂𝑂𝑂𝑂,𝑚𝑚𝑚𝑚𝑚𝑚 bounds LTE-U ON interval to ensure LTE-U receives a fair share of the medium − 𝑇𝑇𝑂𝑂𝑂𝑂,𝑚𝑚𝑚𝑚𝑚𝑚 bounds LTE-U OFF interval to allow time to sense Wi-Fi activity − ∆𝑇𝑇𝑈𝑈𝑈𝑈 and ∆𝑇𝑇𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 determine the convergence speed of CSAT adaptation
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Adjust TON,min for Fairness Selecting TON,min independent of the number of neighbor Wi-Fi APs and LTE-U SCs might result in unfair resource sharing. To mitigate this issue, TON,min is selected as below after every AP scan: 𝑇𝑇𝑂𝑂𝑂𝑂,𝑚𝑚𝑚𝑚𝑚𝑚 where − − − −
𝑁𝑁 + 1 × 𝑇𝑇𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 = 𝑚𝑚𝑚𝑚𝑚𝑚 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇, 𝑁𝑁 + 1 + 𝑀𝑀 + 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁
𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 is a configurable parameter controlling minimum duty cycle below ED N is the number of LTE-U SCs with the same PLMN ID measured by the specific LTE-U SC M is the number of LTE-U SCs with different PLMN ID Number of Wi-Fi Devices (how to weigh in STA activity (visible to the algorithm) is still being optimized) − Always go 1/num_of_Tx vs 1/num_APs vs a mix
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Protecting Latency Sensitive WiFi Applications - Subframe Puncturing Gaps inside Ton • Subframe puncturing introduces frequent gaps in the LTE-U ON duration to help Wi-Fi flush delay-sensitive data and management packets that may be queued at the AP because of LTE-U transmissions • In the specified punctured pattern, the subframes which are punctured are not used for scheduling any data • Typically few msec every few 10s of msec (2/20msec is typical) eNB Tx Power
Few ms SF puncturing every 20ms
TON 80ms
Example: Punctured CSAT Waveform TOFF 80ms 20ms
Tim e
• Another way to accommodate latency sensitive applications is to run short CSAT cycles − Recent design allows LTE-U to go to as low as 20msec of Ton ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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CSAT Cycles • Typical CSAT cycles − 80msec total ON/OFF duration (i.e. like 40/40) & 160msec (i.e. like 80/80msec)
• CSAT cycles on primary WiFi channel are typically shorter to enable beacon transmissions and connection setup activities • In general CSAT cycles are constant but can change in scenarios where LTE-U share is too small − i.e. 10% LTE-U share may be 40msec/360msec as opposed to 10msec out of 100msec
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Benefit of WiFi NL Not fundamental
• Most coexistence functionalities can be achieved without NL albeit more complexity and less optimal trade-offs • Examples: − NL can help though reacting to some less common scenarios like hidden nodes − NL may allow better tradeoff of coexistence since it allows distinction between one node vs multiple nodes when both scenarios show same medium activity − NL allows distinction between LTE-U and WiFi nodes allowing the ability to run reuse 1 if need be on the former ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Lab and OTA Testing
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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LTE-U / Wi-Fi Coexistence Setup • Extensive lab test on LTE-U coex − Wi-Fi: Multiple AP and STA brands − LTE-U: Test eNB and UE MTP
• Current focus: Non-LBT/CSAT design
CSAT Wi-Fi Testing Logical Setup Diagram
TBS eNB
− LBT-based test depend on 3GPP progress − Key Non-LBT coex feature is CSAT − CSAT has dynamic duty cycle, max 100-ms ON time, and long + shortPL OFF gaps PCell − Note LTE-U coexistence in reality would be better with proper channel selection
APUT
FC PLeNB,APUT PLeNB,UE
eNB,UE
• Cabled-up test in controlled environment − 80 MHz max bandwidth assumed for Wi-Fi − LTE-U on one of secondary channels of Wi-Fi
AP
PLAPUT,AP
PLeNB,STAUT
PLAPUT,STAUT
SCell
PLAPUT,STA
PLAP,STA
PLAP,STAUT PLSTAUT,STA
FC
LTE-U UE
STAUT
STA
1x1 AWGN Cabled Up, 802.11ac, 80 MHz
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Full Buffer TCP Throughput Results (Below ED) Below ED AP ID
CINR
TCP Throughput
1
0 dB
0.9x
1
5 dB
1.1x
1
15 dB
1.8x
2
0 dB
0.9x
2
5 dB
0.95x
2
15 dB
1.85x
Baseline throughput = x (50% of isolated Wi-Fi throughput – optimistic assumption) CINR = Wi-Fi signal energy / LTE signal energy at Wi-Fi STA
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Wi-Fi YouTube Streaming Results – Wi-Fi/Wi-Fi vs. Wi-Fi/LTE-U Below ED AP 1 Metrics
Baseline (w/ Wi-Fi)
AP 2
w/ LTE-U
Baseline (w/ Wi-Fi)
w/ LTE-U
No. of video stalls
6.00
1.67
12.33
2.67
Playback interrupt time (s)
7.94
7.40
4.77
2.00
Initial Buffer Time (s)
0.67
1.33
0.33
0.33
Avg. Thpt (Mbps)
3.49
4.49
3.17
5.89
Avg. PHY Rate (Mbps)
19.81
39.88
65.65
83.55
LTE-U hit is an erasure LTE-U with CSAT is a better neighbor than Wi-Fi ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Overview of OTA Campus Network OTA Campus Network
WB LTE-U eNB
WC Wi-Fi AP1 (Above CCA-ED)
Wi-Fi AP2 (Below CCA-ED)
Inset Video Footage
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Carrier Wi-Fi VoIP: Primary CH, Above ED, 160msec CSAT, 2/20 Puncturing
AP backs off for energy during the LTE-U ON period except for gaps in the waveform provided by MBSFN when packets are flushed.
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Carrier Wi-Fi VoIP: Primary CH, Below ED, 160ms CSAT, 2/20 Puncturing Sequence Number Time Trace
2645
Sequence Number
2640
2635
VoIP packets sent during gaps in the CSAT ON duration
2630
2625
CSAT OFF duration 2620
2615 13.3
13.4
13.5 Time (s)
13.6
13.7
13.8 ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Carrier Wi-Fi VoIP: Primary CH, 160ms CSAT, 2/20 MBSFN • Wi-Fi VoIP Calling Statistics† Scenario
|Jitter| > 50ms
Packet Loss
> 3 Consec. Packet Loss
Above ED
6.6%
1.1%
0.1%
Below ED
1.0%
0.7%
0.0%
DL VoIP Packet-to-Packet Jitter CDF
DL VoIP Cycle-to-Cycle Jitter CDF
1 0.9
1 Primary CH, Below ED Primary CH, Above ED
0.9
0.8
0.8
0.7
0.7 0.6
0.5
CDF
CDF
0.6
0.4
0.5 0.4
0.3
0.3
0.2
0.2
0.1 0 -60
Primary CH, Below ED Primary CH, Above ED
0.1 -40
-20 0 20 DL VoIP Packet-to-Packet Jitter (in ms)
40
60
0 -60
†Calculated per WFA-VE guidelines; Packet arrival one approx. every 20ms
-40
-20 0 20 DL VoIP Cycle-to-Cycle Jitter (in ms)
40
60
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Carrier WiFi VOIP: Secondary CH, Below ED, 640ms CSAT, 2/20 MBSFN DL Data Rate Time Trace 30
Smart BW mgmt. forces VoIP to go on the clean primary channel for PER. No degradation in voice quality.
DL Data Rate (Mbps)
25
DL Packet BW CDF 1
20
15
0.9
10 0.8 0.7
5 0
0.6
1
2
3
4
5 Time (s)
6
7
8
9
10
0.5
93.1% of the time packets are sent on the primary 20MHz channel.
0.4 0.3 0.2 0.1 0 0
5
10
15
20 DL Packet BW
25
30
35
40
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Fast CSAT: Low latency MAC Activation/Deactivation • MAC CE for activation is sent xms before start of on time • If deactivation time (Toff) is < Thr, UE is expected to be ready to decode PDCCH in 1-2ms (short cDRX behavior)-no minimum 8ms for activation as in spec • MAC CE for deactivation is sent before end of Ton • Error events of losing or misinterpreting activation/deactivation have to happen ith low probability by design (to the level the can be handled and absorbed by UE tracking loops) CRS ON or Ton
CRS OFF or Toff δ
MAC CE Activation
MAC CE Deactivation
MAC CE Activation
Ton
Activation Overhead
MAC CE Deactivation
Time UE is ready fro grants
• To be accompanied with sending CTS2S with MAC activation after contention − To protect against BI − To protect WiFi rate control ©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
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Stress Room Testing
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Stress Test Chamber
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Stress Test Chamber Setup AP is inside RF shielded box
1 WiFi AP and 1 LTE-U node under test
AP1
AP2
AP3
AP4
STA1
STA2
STA3
STA4
− The WiFi AP-UT is inside an RF shielded box
8 Reference WiFi nodes − 4 APs inside RF box to allow below ED scenarios
3 Enterprise grade WiFi APs + Controller − Referred to as Vendor A, B, and C
AP under test
Gigabit Ethernet switch
STA under test
STA8
STA7
STA6
STA5
AP8
AP7
AP6
AP5
Results presented in these slides − All links above CCA-ED − 8WiFi+WiFi vs. 8WiFi+LTE-U − LTE-U duty cycle = 1/9
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©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Demo GUI Summary (Vendor A) LTE-U outperforms Wi-Fi 6.7 5.8
Wi-Fi
Baseline
LTE-U maintains Wi-Fi performance 6.6
6.8
Wi-Fi
Wi-Fi
Baseline
CSAT
LTE-U LTE-U
CSAT
Unit Under Test Unlicensed throughput
Average Wi-Fi throughput 30
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Demo GUI Summary (Vendor B- more aggressive in winning medium) LTE-U outperforms Wi-Fi
LTE-U maintains/improves Wi-Fi performance
6.6 4.8
Wi-Fi
Baseline
LTE-U
4.9 3.9
LTE-U
CSAT
Unit Under Test Unlicensed throughput
Wi-Fi
Wi-Fi
Baseline
CSAT
Average Wi-Fi throughput
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©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Demo GUI Screenshot (Mixture of Vendor A and B)
Stress Test: 8 Wi-Fi + LTE-U
Baseline: 8 Wi-Fi + Wi-Fi
Vendor B
Vendor A
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©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Demo GUI Summary (Mixture of Vendor A and B) LTE-U outperforms Wi-Fi 6.7 LTE-U 1.9 Wi-Fi Baseline (A)
LTE-U
CSAT
Unit Under Test Unlicensed throughput
LTE-U maintains Wi-Fi performance 5.8
5.8
Wi-Fi
Wi-Fi
Baseline
CSAT
Average Wi-Fi throughput
33
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Demo GUI Screenshot (Mixture of Vendor A and C)
Stress Test: 8 Wi-Fi + LTE-U
Baseline: 8 Wi-Fi + Wi-Fi
Vendor A
Vendor C
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©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Demo GUI Summary (Mixture of Vendor A and C) LTE-U outperforms Wi-Fi 7.1 4.5 Wi-Fi
Baseline
LTE-U maintains Wi-Fi performance 6.6
6.7
Wi-Fi
Wi-Fi
LTE-U LTE-U
CSAT
Unit Under Test Unlicensed throughput
Baseline
CSAT
Average Wi-Fi throughput
35
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Summary of Stress Room Testing Main Observations
In general LTE-U preserves or enhances Wi-Fi user experience If Wi-Fi nodes are fair in medium sharing, LTE-U gains are lower, as its link level gains are not exposed by this dense setup If Wi-Fi nodes are aggressive in medium occupancy, frequent collisions occur and LTE-U provides better user experience for WiFi nodes by deterministically clearing the medium after its fair share decreasing relative number of collisions − LTE-U gains over Wi-Fi are more pronounced in this case and mostly due to MAC 36
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Fairness Testing
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©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Introduction to fairness study We studied how different Wi-Fi APs coexist with each other − Later compared to coexistence with LTE-U as well
Conducted measurements using commercially available Wi-Fi Certified WLAN devices − 5 top-selling retail APs (11ac) based on ‘best-seller lists’ determined from top industry magazines and online-retailers − Product diversity of 5 OEMs and 3 chipset-vendors − Labelled – A thru E
− STA (11ac, 1x1) – a top-selling mobile-device − Same brand of STA device used with all APs to limit combinations 38
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Test Setup Four Networks with 1 AP having 1 STAs each − All APs set to VHT20 in Ch#153 − All combinations of APs from set of 5 considered
Both APs are doing fullbuffer downlink traffic (iperf) to the STAs Average throughput determined over a 90sec period
RF Screen Room STA1
Traffic Source
AP1
STA2
AP2
Traffic Source
STA3
Traffic Source
AP3
STA4
AP4
Traffic Source
39
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Test Results
Different APs achieve different levels of throughput share Wide variation in channel aggregate throughput of different devices despite similar link conditions (high SNR regime)
40
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Fairness between Wi-Fi/Wi-Fi and Wi-Fi/LTE-U Test Setup AP1
STA1
STA under test
AP under test
Gigabit Ethernet switch
Tests are performed using two Wi-Fi connection pairs across different AP models, and one LTE-U link with one Wi-Fi AP link across different AP models 41
©2013-2015 Qualcomm Technologies, Inc. All Rights Reserved.
Consumer grade Fairness with and without LTE-U (Air time) Testing pair-wise airtime sharing across 4 Wi-Fi AP models and between Wi-Fi/LTE-U
Duty Cycle Cycle CDF Duty
1 0.9 0.8
W in 1W+1W W in 1W+1L L in 1W+1L
0.7
CDF
0.6 0.5 0.4
• Points corresponding to coexistence with AP model A • AP model A does not obey CCA-ED rule and does not backoff to LTE-U Points corresponding to all 4 Wi-Fi AP models
0.3 0.2 0.1 0 0
10
20
30
40 50 Percentage
60
70
80
90
42
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