High-efficiency Wi-Fi November 2011 doc.: IEEE 802.11-11/1507r1 March 2013 High-efficiency Wi-Fi Date: 2013-03-19 Authors: Laurent Cariou, Orange Stephen McCann, RIM

November 2011 xxx, Orange

November 2011 doc.: IEEE 802.11-11/1507r1 March 2013 Outline We propose to start a new study group to enhance 802.11 PHY and MAC in 2.4/5 GHz bands “High-efficiency Wi-Fi” targets the key issues that should be addressed to support continued growth and competitiveness of 802.11 across a broad range of market segments Laurent Cariou, Orange Stephen McCann, RIM

November 2011 doc.: IEEE 802.11-11/1507r1 March 2013 Status In July 2012 meeting, Orange presented some requirements for 802.11 to improve the Wi-Fi experience for mobile devices, emphasizing cellular offload as a strong use case [1]. A strawpoll proposing the creation of a study group was largely positive. We received strong support and interest from many 802.11 actors, interested in this topic and willing to contribute. In September 2012, Orange, Huawei, Samsung, NTT and others presented further arguments [2, 5, 3, 4, 8]. Since then, we continued our work to: clearly identify the main problems to solve in IEEE 802.11 and clarify the scope be confident that technical approaches exist that would allow these objectives to be met During this period, it became clear that many of the key issues that should be addressed for cellular offload are common with many other market segments. “High-efficiency Wi-Fi” enhancements have broad market appeal in multiple market segments to form a next-generation of 802.11. We believe the current proposal has sufficient maturity to move to Study Group creation Laurent Cariou, Orange Stephen McCann, RIM

The mobile data explosion March 2013 The mobile data explosion The mobile data explosion is a combination of three components: increased number of mobile devices (absolute, and per area) increased requirements for per-device data throughput increased usage of these mobile devices Per-device data throughput Today, a (reliable) 1 – 5 Mbps connection is adequate for a reasonable user experience with most mobile web applications, including video [6] This minimum satisfactory throughput will grow 50% per year in the coming years [7] due to increased cloud services, higher resolution video, … Increased usage of mobile devices The most significant contributor to the data explosion: predicted 45x growth in next 5 years 55 MB/month in 2011  2.5 GB/month in 2016 for smartphones [7] Operators will need to deploy Wi-Fi hotspots everywhere, including outdoors Most of the environments – residential, enterprise, public spaces – will become high density scenarios Laurent Cariou, Orange

High-Efficiency Wi-Fi March 2013 High-Efficiency Wi-Fi The key point is the increasing usage of 802.11 in high density scenarios This relates not only to operator hotspots, but equally to enterprise, residential, retail and ad-hoc scenarios We propose “High-efficiency Wi-Fi” as a theme to drive the next generation of 802.11 Resulting in enhanced Quality of Experience for a broad spectrum of 802.11 users in everyday scenarios Three key focus points: (1) To improve efficiency in dense networks with large no. of STAs (2) To improve efficiency in dense heterogeneous networks with large no. of APs (3) To improve efficiency in outdoor deployments Laurent Cariou, Orange

The main issues for enhancement March 2013 The main issues for enhancement Topic Scenarios (see details in Annex 1) Issues (see details in Annex 2-3) 1. Large no. of STAs hotspots in dense areas enterprise (BYOD) weak flexibility in use of resources (time, frequency, space) to multiplex users efficiently high collisions and weak MAC efficiency with many STAs, especially with mixed traffic and legacy devices 2. Large no. of APs APs deployed by operators, businesses and consumers in the same neighborhood Wi-Fi Direct devices (Miracast, sync-and-go, etc) and personal Wi-Fi routers limited spatial capacity with OBSS due to spatial protection, interference and lack of coordination with neighboring APs lack of framework for consistent and flexible admission control, load balancing and fairness weak airtime occupation ratio for management vs data 3. Outdoor hotspots in open areas small-cell deployments weak uplink and high interference, weak non-LOS reliability weak robustness to higher delay spreads and Doppler Laurent Cariou, Orange

March 2013 Summary “High-efficiency Wi-Fi” aims to achieve a very substantial increase in the real-world throughput achieved by each user in such scenarios Creating an instantly recognizable improvement in Quality of Experience of the major use cases Generating spatial capacity increase (area throughput) PHY-MAC enhancements for carrier-oriented Wi-Fi are also applicable to broad market segments (residential, enterprise, retail, …) We propose a single SG to integrate these requirements in the overall evolution of 802.11 avoid interdependencies between SGs; timelines may not be much different in practice We believe such evolution will create a broad market appeal for multiple market segments and ecosystem players Consumers, enterprise, operators, Wi-Fi Direct service providers, device vendors, TV/video, medical, … Laurent Cariou, Orange

Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2013 Proposal and timeline We propose to start a new study group to add new PHY and MAC enhancements focused on “High-efficiency WLAN” The scope and duration should be kept focused Focus on the primary spectrum of 802.11 in 2.4 and 5GHz, preserving backward compatibility Main objectives of the study group will be: Prepare use case documents, detail the list of problems and requirements Develop performance metrics to address use cases and quantify objectives Prepare PAR & 5C documents Laurent Cariou, Orange John Doe, Some Company

November 2011 doc.: IEEE 802.11-11/1507r1 March 2013 Straw Poll Should IEEE 802.11 consider the creation of a study group to further discuss the topic of “High efficiency Wi-Fi” ? Yes No Abstain Laurent Cariou, Orange Stephen McCann, RIM

Motion to create a Study Group November 2011 doc.: IEEE 802.11-11/1507r1 March 2013 Motion to create a Study Group Request approval by IEEE 802 LMSC to form an 802.11 Study Group to consider High-efficiency Wi-Fi [as described in doc 11-13-xxxx] with the intent of creating a PAR and five criteria. Moved: <name>, Seconded: <name>, Result: y-n-a Laurent Cariou, Orange Stephen McCann, RIM

March 2013 References [1] 12/0910r0, Carrier oriented WIFI for cellular offload, Orange [2] 12/1123r0, Carrier oriented WIFI for cellular offload, Orange [3] 12/1126r0, Wi-Fi techniques for hotspot deployment and cellular offload, Samsung [4] 12/1063r0, Requirements for WLAN Cellular Offload, NTT [5] 13/0098r0, 802.11: Looking Ahead to the Future – Part II, Huawei [6] Cisco WLAN design guide for High Density [7] Cisco VNI mobile 2012 [8] 13/0113r0, Application and Requirements for Next Generation WLAN, Samsung Laurent Cariou, Orange

March 2013 Annexes Laurent Cariou, Orange

Hotspot deployment scenarios Annex 1 Hotspot deployment scenarios Hostpot deployments will scale between: Street deployment for a blanket coverage of a neighborhood (typical cellular network pico-cell deployment) 50 APs per km², 150-200m distance between hotspots Very high density deployments (stadiums, train stations, …) 6400 APs per km², 12-20m distance between APs 0.5 users per m² AP STA 160-200m MCS0 range MCS0 range MCS6 range MCS6 range Laurent Cariou, Orange

Pico-cell street scenario Annex 1 Pico-cell street scenario Characteristics of outdoor street deployments: most deployments will be made with placement below rooftop (3 - 10m): lamp poles, hanged on cables, stuck to walls… mostly side coverage (omni or directional) ITU Micro (UMI) model could be a good fit deployment is costly (backhaul, site rental…). As a consequence: the distance between APs must be as high as possible (2 neighbor deployed APs will overlap close to the minimum sensitivity) – around 150-200 meters AP Tx Power is high (23-30dBm) less constraints on frequency reuse high density of STAs, spread over the whole BSS coverage heterogeneous dense deployment: potential high proportion of interfering APs in the coverage of hotspots indoor home or shop private APs leaking outdoors (usually in hidden node situation) at 2.4GHz, between 15 to 20 APs in all 3 channels (beacons already occupy 20% of channel) other public hotspots coordination is feasible if they belong to the same operator, is very difficult with other APs 160-200m AP STA Laurent Cariou, Orange

Stadium / train station scenario Annex 1 Stadium / train station scenario Characteristics of stadium/train station deployments: side or overhead coverage (omni or directional) very high user density (ex: hypothesis of 0.5 users/m²). As a consequence, the distance between APs is reduced as much as possible (2 neighbor deployed APs will overlap largely) – around 12-20 meters AP Tx Power is usually reduced (6-12dBm) high AP density: high constraints on frequency reuse: multi-BSS spatial capacity improvements high density of STAs, regrouped over a limited range (higher MCSs) and not on the whole AP coverage (MCS0 range) high co-channel interference coming from neighboring APs reusing the same frequencies coordination is possible via the controller potential interference coming from soft APs more difficult to coordinate MCS0 range MCS0 range MCS6 range MCS6 range Laurent Cariou, Orange

What are the main problems? Annex 2 What are the main problems? High number of STAs per AP 802.11 channel access has been designed for and is effective with a limited number of users. However, with a high density of STAs: limitations of CSMA-CA: inefficient after a certain density of STAs due to increased collisions MAC efficiency/airtime use limitations: - much less efficient for a high number of users, each with limited throughput applications - airtime use can be very inefficient with a traffic mix (small and big packets) - a significant proportion of packets are very small - e.g. web browsing: <100B packets represent 90% UL packets and 25% DL packets airtime use can be also very inefficient with a mix of legacy devices management frames (e.g. probe requests/responses) consume a large fraction of the available airtime Laurent Cariou, Orange

Illustration: collision issues with high STA density per BSS Annex 2 Illustration: collision issues with high STA density per BSS Average PER increases rapidly with the number of STAs, approaching 50% for 25 STAs Throughput and latency and power consumption is strongly impacted Most rate prediction algorithms in devices lower MCS when PER increases, leading to a spiraling down of throughput. Example with a rate prediction AARF (PER based) AARF reference: IEEE 802.11 rate adaptation: a practical approach Mathieu Lacage, Mohammad Hossein Manshaei, Thierry Turletti International Workshop on Modeling Analysis and Simulation of Wireless and Mobile Systems - MSWiM , pp. 126-134, 2004  AP sum throughput collapses Laurent Cariou, Orange

What are the main problems? Annex 2 What are the main problems? In very high density deployment scenarios (large no. of APs) saturation with high number of STAs per AP channel reuse is almost impossible co-channel interference strongly limits spatial capacity problem is harder in environments without walls where propagation is very good other interferences (adjacent-channel interference, non Wi-Fi interference) inefficient cohabitation with tethering devices (soft APs) and Wi-Fi Direct devices difficult to achieve consistent admission control, load balancing and fairness behavior to optimize networks even when APs deployed together CCA protection zone Typical scenario: e.g. user density: 0.5 user/m² cellular-like APs planning (with frequency reuse pattern) AP density: 6400 AP/km² (distance between neighboring APs: 14m) Channel reuse 3 Laurent Cariou, Orange

What are the main problems? Annex 2 What are the main problems? In outdoor deployment scenarios delay spread issue in typical outdoor ITU UMI channels links can hardly be maintained in non-LOS, even with good received SNR (with Rx power below -70/75 dBm) uplink is the limiting factor - especially with smartphones (10-12dBm Tx power) high levels of interference home gateways leaking outdoors minimum of 15-20 uncoordinated APs per channel (2.4GHz) under coverage (with rather small Rx power – but sufficient to cause interference, especially at BSS-edge) saturation with a high number of STAs per AP Typical scenario: Pico-cell/AP deployment 50 to 60 APs per km²: inter-AP distance of 150-200m 500Mbps on 20000m² (80m-radius BSS) Laurent Cariou, Orange