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LTE unlicensed and Wi-Fi: moving beyond coexistence

Monica Paolini, Senza Fili

May 12, 2015

| 2 | © Senza Fili Consulting LLC 2015

Why LTE unlicensed?

April 15, 2023

• Massive shift to wireless traffic – Mostly driven by Wi-Fi– Cellular only a small part of it

• Much of wireless access over 2.4 GHz band• High value of unlicensed spectrum

– High resource utilization– High spectral reuse– Increasing importance to carry IP traffic– Increasing demand for unlicensed spectrum

• Mobile operators have become interested in unlicensed spectrum– Overcome diffidence of Wi-Fi, when Wi-Fi offload

became necessary– LTE unlicensed widens the opportunities to used

the unlicensed band

Densification and multi-faceted networks make coexistence and integration of multiple technologies and

co-located networks crucial to efficient resource utilization


Some terminology to start

April 15, 2023


Wi-Fi or LTE unlicensed? A comparison

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Factors affecting relative performance

of Wi-Fi and LTE unlicensed• LTE unlicensed specifications (3GPP LAA-LTE specifications

are not yet finalized, so current simulations and trials have to make assumptions on what the specifications will be)

• Physical environment and deployment topology (including indoor versus indoor locations)

• Technologies features and versions • Hardware vendor, equipment specifications• Channel size; TDD or FDD inclusion of uplink; frequency

reuse• Spatial distribution of UEs and infrastructure nodes

(macro and small cells, Wi-Fi AP); collocated/non collocated equipment

• Synchronization• Traffic model, including assumptions on traffic mix (e.g.,

voice and video as a percentage of traffic)• Other simulation parameters

April 15, 2023

• Multiple simulations and trials done/ongoing

• Difficult to compare and generalize results

• Differences among results reflect differences among assumptions

• Useful to look at directionality of performance drivers


Directional trends in LTE unlicensedand Wi-Fi performance

April 15, 2023

Wi-Fi vs LTE (stand alone)

Wi-Fi and LTE (coexistence)

LTE has better spectral efficiency:- Transmission- Interference management- Coverage

LTE performance is more robust with:- Increased traffic load- Number of users

Combined Wi-Fi and LTE capacity can be higher than Wi-Fi only

Wi-Fi performance may increase with LTE as neighbor (instead of Wi-Fi)

Unclear impact of LBT and fair coexistence mechanisms- Standardization still in progress, so

difficult to assess impact- Could LBT erase most of the

performance advantages of LTE over Wi-Fi?

Spread of performance measurements vary among simulations and tests, but the trends are clear


LWA, LAA, and LWA with LAA

April 15, 2023

Source: Alcatel-Lucent

• LTE and Wi-Fi integration is also getting traction– Confirmation of importance of 5 GHz spectrum (traditionally not considered for

cellular)• 3GPP standardization for Release 13• Integration with Wi-Fi at the edge

– Complementary to other mechanisms for integration• Can complement or substitute LAA


Concluding remarks

• LTE unlicensed attracts attention of mobile operators because of increased spectral efficiency

• Wi-Fi users may feel threatened by LTE unlicensed– Some consider 5 GHz as “Wi-Fi spectrum”, but it is not only for Wi-Fi– Fair coexistence is possible, but industry collaboration is needed (beyond

regulation)• Success of LTE unlicensed is contingent on

– Availability and cost to add LTE unlicensed to mobile devices– Acceptance of LTE unlicensed by the Wi-Fi ecosystem– Performance advantage of LTE unlicensed over Wi-Fi (with LBT)– Per-bit cost spread for LTE unlicensed over Wi-Fi – Advancement in the Wi-Fi and cellular integration, as possible alternative

to LTE unlicensed

April 15, 2023

April 15, 2023

Monica PaoliniSenza Filiwww.senzafiliconsulting.commonica.paolini@senzafiliconsulting.com

Cover photo by Lukas Rebec/Shutterstock.com; icons from Stoker-13/Shutterstock

Download the report from http://content.rcrwireless.com/Analyst_Angle_LTE_Report

New Senza Fili Report on LTE

unlicensed and Wi-Fi in

collaboration with RCR Wireless

News


The 3GPP approach to LAA standardization

April 15, 2023

Agreement to focus on the 5 GHz band

Commitment to find a global solution

LBT, with maximum transmission

duration

Dynamic frequency selection for radar

avoidanceCarrier selection Transmit power

control

Covered areas:• Regulatory requirements• Deployment scenarios• Design targets and functionalities• Coexistence evaluation and methodology

Backup slides


Why do operators care about LTE unlicensed?

April 15, 2023

• Efficient resource utilizationis crucial– Increase in traffic– Stationary ARPU– IoT

• Spectrum is a finite resource, but spectral efficiency/areacan increase

• Density• Technology• Topology

• 5 GHz band is a good target for spectrum utilization improvement– But use of unlicensed spectrum

requires a new approach from mobile operators (this is not Wi-Fi offload)


Beyond LTE unlicensed in the 5 GHz band:

alternatives and complementary approaches

Stand-alone LTE unlicensed Carrier Wi-Fi LTE and Wi-Fi

aggregation

3.5 GHz LTE LTE unlicensed in other bands

April 15, 2023


The LAA in LTE unlicensed:links between licensed and

unlicensed transmission

April 15, 2023


Mechanisms for LTE unlicensed and Wi-Fi coexistence

April 15, 2023


3GPP standardization crucial to establish LTE unlicensed worldwide

From 3GPP R-141817, on coexistence with Wi-Fi:

It is not enough to minimize interference simply for regulatory aspects. It is also essential to insure that a deployed system will operate as a “good neighbour”, and not significantly impact legacy systems.

[The purpose is to] identify and define design targets for coexistence with other unlicensed spectrum deployments, including fairness with respect to Wi-Fi and other LAA services. This should be captured in terms of relevant fair sharing metrics, e.g., that LAA should not impact Wi-Fi services (data, video and voice services) more than an additional Wi-Fi network on the same carrier; these metrics could include throughput, latency, jitter etc. This should also capture in-device coexistence for devices supporting LAA with multiple other-technology radio modems, where it should, e.g., be possible to detect Wi-Fi networks during LAA operation

April 15, 2023


3GPP LAA deployment scenarios

April 15, 2023

Scenario 1: CA between licensed macro cell (F1) and unlicensed small cell (F3)Scenario 2: CA between licensed small cell (F2) and unlicensed small cell (F3), no macro coverage (e.g., indoor deployment)Scenario 3: CA between licensed small cell (F1) and unlicensed small cell (F3), with macro coverageScenario 4: CA between licensed small cell (F2) and unlicensed small cell (F3), with macro coverage (F1). With ideal backhaul between macro and small cell, CA among F1, F2 and F3 is possible. Dual connectivity between macro cell and small cell can be enabled.


NTT DOCOMMO deployment scenariosand architecture

April 15, 2023

NTT DOCOMO deployment scenarios

Source: NTT DOCOMO

NTT DOCOMO has considered indoor and outdoor scenarios, with and without co-location of licensed and unlicensed small cells. Integration between licensed and unlicensed LTE is highest when CA is used.

NTT DOCOMO LTE unlicensed architecture

Source: NTT DOCOMO

LTE unlicensed can be integrated closely at the RAN. The offloading region is more restricted, but HetNet functionality can be more effectively implemented.


Sources of interference in the 5 GHz band

with LTE unlicensed and Wi-Fi

April 15, 2023

Source: NTT DOCOMO

Intra-RAT interference among LTE unlicensed network can be managed with intra-operator or inter-operator synchronization. Inter-RAT transmission can be managed with LBT.


Wi-Fi and LTE performance comparison: single operator

April 15, 2023

Source: NTT DOCOMO

In NTT DOCOMO’s simulation, as the traffic load increases, LTE unlicensed spectral efficiency decreases more slowly than for Wi-Fi, making LTE unlicensed better in high-traffic environments.


In NTT DOCOMO’s simulation, under medium traffic load assumptions, LTE is more spectrally efficient than Wi-Fi and, when combined with Wi-Fi, lead to an overall increase in spectral efficiency.

Source: NTT DOCOMO

Wi-Fi and LTE performance comparison:

coexistence scenario, two operators

Download - LTE unlicensed and Wi-Fi: moving beyond coexistence from Monica Paolini, Senza Fili

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