1. LAA / Wi-Fi Coexistence evaluations with commercial hardware
Kyu-Han Kim, Liang Li, Eldad Perahia, Dorothy Stanley, Stuart Strickland, and Christina Vlachou
17 July 2019

2. Coexistence testbed LAA eNodeB Wi-Fi Access Point Client Devices
9/20/2019 1:44 PM
Coexistence testbed
LAA eNodeB
Commercially available LAA base station controlled using OpenEPC
Dual radio: one licensed primary and one unlicensed secondary cell
Compliant with 3GPP Release 13 with primary cell carrying uplink and control plane traffic in a single 20MHz channel of licensed spectrum and secondary cell carrying downlink traffic in a single 20MHz channel of Band 46 (5GHz)
Secondary cell implements listen-before-talk (LBT) per 3GPP specification with Energy Detect (ED) threshold of -72dBm and maximum Transmit Opportunity (TXOP) duration of 8ms
Wi-Fi Access Point
802.11ac access point configured to operate in a single 20MHz channel of unlicensed 5GHz spectrum
Implements Clear Channel Assessment (CCA) per IEEE specification with ED threshold of -62dBm, Preamble Detect (PD) threshold of -82dBm, and TXOP duration of < 2.528ms as specified for “best effort” traffic
Client Devices
Samsung Galaxy Note8 supporting ac and LAA in a single 20MHz channel of Band 46 as specified in 3GPP Release 13
Separate client devices dedicated to LAA and Wi-Fi
Traffic Models & Procedure
Full-buffer UDP traffic generated by iPerf for both Wi-Fi and LAA. Youtube video traffic for LAA in “real traffic” scenario
Throughput measured across several scenarios in which the LAA and Wi-Fi system were audible to each other above and below their respective LBT thresholds and maximum TXOP times were varied
Presenter Name

3. Wi-Fi Clear Channel Assessment
9/20/2019 1:44 PM
Wi-Fi Clear Channel Assessment
Interferer
Signal Strength
Wi-Fi systems base assessment of channel availability using a two-tiered method, detecting energy from any source and detecting preambles specific to Wi-Fi
Both LAA and other Wi-Fi transmissions are detected and deferred to by a Wi-Fi system if energy is detected at levels greater than -62dBm*
Other Wi-Fi transmissions are detected and deferred to if their preambles are detected at levels greater than -82dBm*
LAA transmissions received at levels below -62dBm and Wi-Fi transmissions received at levels below -82dBm are effectively hidden nodes creating unmitigated interference with a Wi-Fi system
No hidden terminals
-62dBm (ED)
LAA hidden terminals
-82dBm (PD)
LAA and Wi- Fi hidden terminals
Presenter Name
*20MHz bandwidth

4. SCENARIO 1: LAA Above Wi-Fi ED Threshold
9/20/2019 1:44 PM
SCENARIO 1: LAA Above Wi-Fi ED Threshold
Interferer
Signal Strength
LAA eNB and Wi-Fi AP in close proximity to each other and their respective clients
Results collected for LAA TXOP of 8ms and 4ms and Wi-Fi TXOP of ~2.5ms
Wi-Fi throughput reduced by 63% when LAA TXOP = 8ms and by 34% when LAA TXOP = 4ms
Wi-Fi MCS and SFER were not affected by collisions, suggesting that reduction in throughput is due to TXOP differences
-62dBm (ED)
-82dBm (PD)
LAA TXOP: 8ms
LAA TXOP: 4ms
Presenter Name
*20MHz bandwidth

5. SCENARIO 2: LAA & Wi-Fi BELOW ED ThresholdS
9/20/2019 1:44 PM
SCENARIO 2: LAA & Wi-Fi BELOW ED ThresholdS
Interferer
Signal Strength
eNB and all APs set to 13dBm Tx power and separated by 38ft such that all nodes were visible to each other at levels below their ED thresholds and above the Wi-Fi PD threshold of -82dBm
Wi-Fi SFER raised significantly by collisions with LAA and throughput impacted more severely by LAA than by Wi-Fi due to interference from hidden LAA nodes
-72dBm (ED)
-82dBm (PD)
Presenter Name
Impact of Wi-Fi on Wi-Fi
Impact of LAA on Wi-Fi
*20MHz bandwidth

6. SCENARIO 3: REAL Traffic ABOVE and BELOW Wi-Fi ED
9/20/2019 1:44 PM
SCENARIO 3: REAL Traffic ABOVE and BELOW Wi-Fi ED
Interferer
Signal Strength
Question: How does LAA affect Wi-Fi during actual use?
LAA client continuously streaming YouTube video at 1440p throughout a 180s test session
Wi-Fi system loaded with full buffer UDP traffic
Results: Wi-Fi performance suffers more when LAA is below its ED threshold, with frequent disconnects and points at which throughput drops below 1Mbps
-62dBm (ED)
-82dBm (PD)
Presenter Name
LAA Above Wi-Fi ED
LAA Below Wi-Fi ED
*20MHz bandwidth

7. CONCLUSIONS & RECOMMENDATIONS
9/20/2019 1:44 PM
CONCLUSIONS & RECOMMENDATIONS
OBSERVATIONS
Under common deployment scenarios, LAA can significantly degrade Wi-Fi performance
Above Wi-Fi ED, LAA can degrade Wi-Fi more than would another Wi-Fi system due to differences in TXOP duration
Below Wi-Fi ED, interference from hidden LAA nodes significantly degrades Wi-Fi performance
In the presence of streaming LAA connections below Wi-Fi ED, Wi-Fi suffers from continuous performance degradation and frequent disconnections
RECOMMENDATIONS
systems should adopt TXOP limits aligned with those of 3GPP systems operating in unlicensed spectrum to avoid unfairly disadvantaging Wi-Fi
and and 3GPP systems operating in unlicensed spectrum should establish a common preamble to interference from hidden nodes
Presenter Name

8. Our hyper-connected, data-driven world is rapidly creating new ways to redefine experiences, drive smarter operations and accelerate innovation. The explosion of data and built-in intelligence from the edge is reshaping markets and disrupting every industry. Your success depends on how quickly you can utilize all of the data created across your many edges and your multiple clouds and to turn data into insight and action. In today’s edge-to-cloud world, the future belongs to the fast.
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