studying the impact of lte-u on wi-fi downlink performance
TRANSCRIPT
Amr ABDELFATTAH
Naceur MALOUCH
Studying the Impact of LTE-U on Wi-Fi Downlink Performance
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Why LTE-U is needed?
What are LTE-U’s requirements?
How LTE-U could be achieved?
Duty Cycled LTE (LTE-U) Wi-Fi downlink performance Wi-Fi downlink/uplink performance
Conclusion.
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AGENDA
Opportunistic use of unlicensed spectrum to address the mobile data growth challenges
Unified network compared to WLAN data offloading
Operators are more free to chose between LTE-U and LTE/Wi-Fi interworking
Efficient utilization of unlicensed spectrum resources
Licensed spectrum ensures quality of service and unlicensed spectrum for boosting data speeds
…etc
LTE-U small cell deployment scenario
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(from C. Hoymann, \LTE in unlicensed spectrum|technical and regulatory aspects")
Why LTE-U is needed ?
Effective and fair coexistence with Wi-Fi
Should not impact Wi-Fi services (data, video and voice services) more than an additional Wi-Fi network on the same carrier
Effective and fair coexistence among LTE-U networks deployed by different operators
With/Without coordination among operators
User equipment capability
User equipment supports two technologies (Wi-Fi & LTE-U) in the same spectrum
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What are LTE-U’s requirements?
How LTE-U could be achieved?
1) TDM (USA, China and Korea )
Backward compatibility Based on Rel.10,11 and 12 Time division multiplexing
• Blank subframe Allocation • Scell Activation/Deactivation
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2) LBT (Europe and Japan)
Global solution Based on Rel. 13 Listen Before Talk
• Load Base Equipment (LBE)• Frame Based Equipment (FBE)• …etc
Duty cycled LTE configuration:
A. Duty cycle period Short (1 ̴10 ms) Long (20 ̴100x ms) Long + Short
B. Duty cycle percentage 50%, 30%, ... , depends on Wi-
Fi needs
C. ON/OFF periods distribution M = number of disjoint
transmission periods per duty cycle.
Wi-Fi performance:
A. Throughput Delay Data + Voice or Video
B. 50% duty cycle is not enough to share equally the channel
C. As M , Throughput
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Duty Cycled LTE (LTE-U)
Periodic DTMC with period M = 3 7
Duty Cycled LTE (LTE-U)
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Random Walk / Renewal Process
0
Duty Cycled LTE (LTE-U)
For a given period, N has an upper bound nmax, where With
Similarly, we can compute all other transition probabilities. Now we can deduce the probability of occurrence of each state at multiples of M , ϵ (1,…,M).
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Duty Cycled LTE (LTE-U)
Probability of Collision
Downlink Wi-Fi Throughput
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, ,
Duty Cycled LTE (LTE-U)
Analytical model Vs
Duty Cycled
5x0
3x2
4x1
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Duty Cycled LTE (LTE-U)
5X0 ON/OFF pattern
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Collisions degrade the throughput by a non-marginal amount
Standard behavior of Wi-Fi throughput versus packet size is not valid anymore
For small packet size, the probability of collision has a positive linear relationship
After a specific packet size, the probability of collision shows some ripples
Throughput ripples are so much sharp that may cause loosing up to 26% of throughput compared to the maximum
50% ON/OFFduty cycle is not enough
Duty Cycled LTE (LTE-U)
5X0 ON/OFF pattern
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As Wi-Fi speed increases :
The impact of LTE-U on Wi-Fi performance decreases
Throughput ripples and collision probability stairs start to appear for a larger packet sizes
Duty Cycled LTE (LTE-U)
3X2 ON/OFF pattern
4X1 ON/OFF pattern 14
Duty Cycled LTE (LTE-U)
6Mbps
12 Mbps 15
Duty Cycled LTE (LTE-U)
165X0 ON/OFF pattern with number of Wi-Fi stations = 10
Duty Cycled LTE (LTE-U)
Using our analytical model, we quantify the impact of LTE-U on Wi-Fi performance
The impact of LTE-U on Wi-Fi performance depends on both network configuration parameters:
• LTE-U duty cycle configuration ( M parameter, Duty cycle period and percentage) • Wi-Fi Network (number of station, data rate and packet size )
We tie up between the different TDM schemes of LTE-U and Wi-Fi performance, henceforth, it is possible to find the required compensation that makes the sharing equal between the two systems
We provide a novel Wi-Fi throughput analysis in case of a hidden node (i.e. LTE-U) using a random walk approach
The duty cycled LTE-U traffic (i.e. deterministic traffic ) cannot be approximated by an exponential traffic as the PASTA property does not hold which leads to the need of our model
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Conclusion
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Questions