doc.: IEEE 802.11-12/1126r0 Submission September 2012 Krishna Sayana, Samsung Slide 1 Wi-Fi for Hotspot Deployments and Cellular Offload Date: 2012-09-18 N am e A ffiliations A ddress Phone em ail K rishna Sayana Sam sung 1301 E LookoutD r, Richardson, TX , 75082 +1-972-680-4559 k.sayana@ samsung..com Charlie Zhang Sam sung +1-972-761-7872 jianzhong.z@ samsung.com Authors:
Doc.: IEEE 802.11-12/1126r0 Submission September 2012 Krishna Sayana, SamsungSlide 1 Wi-Fi for Hotspot Deployments and Cellular Offload Date: 2012-09-18.
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doc.: IEEE 802.11-12/1126r0
Submission
September 2012
Krishna Sayana, SamsungSlide 1
Wi-Fi for Hotspot Deployments and Cellular Offload
Date: 2012-09-18
Name Affiliations Address Phone email Krishna Sayana Samsung 1301 E Lookout Dr,
Richardson, TX, 75082 +1-972-680-4559 [email protected]
Charlie Zhang Samsung +1-972-761-7872 [email protected]
Authors:
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 2
doc.: IEEE 802.11-12/1126r0
Submission
Background: Wi-Fi Trends
September 2012
Krishna Sayana, SamsungSlide 3
Increasing portion of total network access on Wi-Fi
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 4
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 5
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 6
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 7
doc.: IEEE 802.11-12/1126r0
Submission
Distributed Coordination Strategies (1)
• 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)
September 2012
Krishna Sayana, SamsungSlide 8
AP1 AP2
STA1
STA2
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 9
doc.: IEEE 802.11-12/1126r0
Submission
Centralized Coordination Strategies (1)• 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
September 2012
Krishna Sayana, SamsungSlide 10
AP1 AP2
STA1
STA3
NullSteering
STA2
STA4
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 11
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 12
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 13
doc.: IEEE 802.11-12/1126r0
Submission
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.,)
September 2012
Krishna Sayana, SamsungSlide 14
doc.: IEEE 802.11-12/1126r0
Submission
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
September 2012
Krishna Sayana, SamsungSlide 15
doc.: IEEE 802.11-12/1126r0
Submission
September 2012
Krishna Sayana, SamsungSlide 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
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