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

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1. LTE unlicensed and Wi-Fi: moving beyond coexistence Monica Paolini, Senza Fili May 12, 2015 2. | 2 | Senza Fili Consulting LLC 2015 Why LTE unlicensed? June 15, 2015 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 3. | 3 | Senza Fili Consulting LLC 2015 Some terminology to start June 15, 2015 4. | 4 | Senza Fili Consulting LLC 2015 Wi-Fi or LTE unlicensed? A comparison June 15, 2015 5. | 5 | Senza Fili Consulting LLC 2015 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 June 15, 2015 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 6. | 6 | Senza Fili Consulting LLC 2015 Directional trends in LTE unlicensed and Wi-Fi performance June 15, 2015 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 7. | 7 | Senza Fili Consulting LLC 2015 LWA, LAA, and LWA with LAA June 15, 2015 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 8. | 8 | Senza Fili Consulting LLC 2015 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 June 15, 2015 9. June 15, 2015 Monica Paolini Senza Fili Cover photo by Lukas Rebec/; icons from Stoker-13/Shutterstock Download the report from New Senza Fili Report on LTE unlicensed and Wi-Fi in collaboration with RCR Wireless News 10. | 10 | Senza Fili Consulting LLC 2015 The 3GPP approach to LAA standardization June 15, 2015 Agreement to focus on the 5 GHz band Commitment to find a global solution LBT, with maximum transmission duration Dynamic frequency selection for radar avoidance Carrier selection Transmit power control Covered areas: Regulatory requirements Deployment scenarios Design targets and functionalities Coexistence evaluation and methodology 11. Backup slides 12. | 12 | Senza Fili Consulting LLC 2015 Why do operators care about LTE unlicensed? June 15, 2015 Efficient resource utilization is crucial Increase in traffic Stationary ARPU IoT Spectrum is a finite resource, but spectral efficiency/area can 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) 13. | 13 | Senza Fili Consulting LLC 2015 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 June 15, 2015 14. | 14 | Senza Fili Consulting LLC 2015 The LAA in LTE unlicensed: links between licensed and unlicensed transmission June 15, 2015 15. | 15 | Senza Fili Consulting LLC 2015 Mechanisms for LTE unlicensed and Wi-Fi coexistence June 15, 2015 16. | 16 | Senza Fili Consulting LLC 2015 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 June 15, 2015 17. | 17 | Senza Fili Consulting LLC 2015 3GPP LAA deployment scenarios June 15, 2015 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 coverage Scenario 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. 18. | 18 | Senza Fili Consulting LLC 2015 NTT DOCOMMO deployment scenarios and architecture June 15, 2015 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. 19. | 19 | Senza Fili Consulting LLC 2015 Sources of interference in the 5 GHz band with LTE unlicensed and Wi-Fi June 15, 2015 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. 20. | 20 | Senza Fili Consulting LLC 2015 Wi-Fi and LTE performance comparison: single operator June 15, 2015 Source: NTT DOCOMO In NTT DOCOMOs 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. 21. | 21 | Senza Fili Consulting LLC 2015 In NTT DOCOMOs 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