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Wi-Fi for Hotspot Deployments and Cellular Offload

Wi-Fi for Hotspot Deployments and Cellular Offload. Date: 2012-09-18. Authors:. Abstract. Ever increasing data traffic fueled by new devices and applications Network deployments moving to small cells and dense deployments A significant portion of such traffic on WiFi networks (12/936r0)

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Wi-Fi for Hotspot Deployments and Cellular Offload

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  1. Wi-Fi for Hotspot Deployments and Cellular Offload Date: 2012-09-18 Authors: Krishna Sayana, Samsung

  2. Abstract • Ever increasing data traffic fueled by new devices and applications • Network deployments moving to small cells and dense deployments • A significant portion of such traffic on WiFi networks (12/936r0) • As discussed in July meeting (12/910r0-Orange), increasing focus is on Wi-Fi outdoor hotspot deployments and cellular offload • Next Generation Wi-Fi should target support for these new scenarios • In this presentation, we share our views on scope of PHY/MAC techniques for this purpose Krishna Sayana, Samsung

  3. Background: Wi-Fi Trends Increasing portion of total network access on Wi-Fi Krishna Sayana, Samsung

  4. Next Generation Wi-Fi PHY PHY enhancements proposed for different application scenarios and available spectrum. • MU-MIMO • Increased spectral efficiency with multi-user support • OFDMA • Flexible resource allocation; Backwards compatible • Uplink MU-MIMO • Simultaneous access of multiple users for symmetric traffic scenarios • 6-10 GHz ac extension • Offload short-range applications when 5GHz spectrum saturates • Reuse PHY/MAC designs Krishna Sayana, Samsung

  5. Next Generation Wi-Fi MAC Goal for MAC enhancements to improve system capacity, avoid congestion (OBSS) and coexist with cellular networks • Scheduler improvements • Optimize for new PHY designs, e.g, DL-OFDMA, MU-MIMO • Coordination mechanisms • We discuss some examples Krishna Sayana, Samsung

  6. AP Scheduler Enhancements (1) • Currently, EDCA/HCCA used for throughput fairness • Allows different access categories and priorities • Configurable contention based access parameters • Ex: CW, IFS, CFW • Not very efficient and reduce overall throughput • Do not scale for future enhancements • PCF/HCCA not widely used • Collision with neighbor BSSs also responsible for limited gains Krishna Sayana, Samsung

  7. AP Scheduler Enhancements (2) Key techniques • Improved admission control, parameterization and coordination mechanisms • Improved TDM based access mechanisms • EDCA/HCCA parameterization improvements • In a later phase, consider PHY enhancements like OFDMA, MU-MIMO Krishna Sayana, Samsung

  8. Distributed Coordination Strategies (1) AP1 AP2 • Scenario: Slow coordination, Single/Multi-vendor APs • Load balancing • Power control • Directional beamforming • Handover optimization • Channel reuse in space, time and frequency • AP-AP information exchange (e.g. 802.11ah, wired backhaul) STA2 STA1 Krishna Sayana, Samsung

  9. Distributed Coordination Strategies (2) • How to introduce specification support for these schemes? • Slow coordination must be robust and allow higher latency to be supported • Define requirements on latency acceptable for individual schemes • Coordination targets interference management and resource allocations in multiple BSSs • Identify key parameters for exchange • Resource reservations, RRM parameters, Contention access, Spatial parameters • Identify a list of schemes • AP silencing, reduced power operations, transmission in null directions Krishna Sayana, Samsung

  10. Centralized Coordination Strategies (1) AP1 AP2 • Scenario: Cluster of APs with a central controller; fast backhaul • Dynamic joint scheduling and interference management • PHY layer coordination schemes • Semi-static coordination can also be used for interference management Null Steering STA1 STA2 STA3 STA4 Krishna Sayana, Samsung

  11. Centralized Coordination Strategies (2) • Centralized coordination can be supported in a later phase • Can reuse techniques developed for distributed coordination with fast exchange of parameters • Spatial coordination more effective with fast coordination • However some smart proprietary implementations are possible • What is additionally needed to improve support in WiFi specifications? • Transparent network operation and backwards compatible schemes preferred • Target spec support that improves over existing implementations Krishna Sayana, Samsung

  12. Synchronization • Do we need timing synchronization improvements for supporting coordination? • Some timing synchronization is needed to allow access to multiple APs • E.g Can consider mechanisms such as random access procedure and timing advance to align transmission timing of multiple STAs • Frame level alignment procedures for cellular/WiFi offload and coordination • The requirements are dependent on target scenarios, cell size, AP density etc., • As a first priority, can target scenarios that do not need efforts in this area Krishna Sayana, Samsung

  13. WiFi Cellular Offload • Offload macro cell users to WiFi APs • High level coordination between 3GPP gateway and WiFi network • Cell range extension based on network conditions • Handover between APs and cellular/small cells • Improvements to WiFi roaming • Certain parameters may be exchanged between different RATs • Ex: RRM, QoS, load and capability parameters • Current hotspot WLAN deployments have no integration with the cellular counterparts • UE experience is not seamless Krishna Sayana, Samsung

  14. Scenarios for Study • Hotspot Deployments • APs with distributed coordination/interference management capabilities • Backhaul Assumptions • Latency, capacity • Define relevant scenario parameters like • Density of APs, AP distribution • Number of UEs/AP, UE distribution • Channel models (Delay spread etc.,) • Traffic Types/Mix • Relative location of APs and Cellular BSs (co-located etc.,) Krishna Sayana, Samsung

  15. Objectives • Develop new scenarios for study with further input from vendors/service providers/operators in WNG • Identify important metrics e.g., latency, HO delays, throughput, cell-edge performance, carrier network performance • Identify schemes to • Improve performance of WiFi in dense deployments • Consider new PHY techniques that can also help meet these goals? • Enable seamless WiFi cellular offload Krishna Sayana, Samsung

  16. References • Carrier-Oriented-WiFi-Cellular-Offload, 12/910r0 • Review of Overlapping 802.11 Networks (OBSS) Status and IEEE 802.11 Solutions, 12/936r0 • Compatibility of 6-10GHz extensions with the 802.11ac PHY, 12/653r0 • Improved Spectrum Efficiency for the Next Generation WLANs, 12/820r0 Krishna Sayana, Samsung

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