The demands on each generation ofÂ WiFi technologyÂ has been different. When it started off, WiFi did not have to address any of the applications that run over it today. It was just going to be a cable replacement for basic enterprise data. IfÂ 802.11acÂ was all about enablingÂ high throughput,Â 11axÂ is expected to do a lot more. Customers have been promisedÂ higher throughput, lower latency (4x lower!!!) and higher user density. That is a lot to deliver on.
Although there have beenÂ announcements galore, there are a veryÂ limitedÂ number of devices (especially Clients) in the market today withÂ full 802.11axÂ support. Chip vendors and OEMs are busy delivering products to their announced roadmaps. WithÂ no ready to use test equipment, interoperability remains a major challenge. It was being addressed at multiple Plug fests.Â 802.11axÂ is fundamentally moreÂ complexÂ than earlier WiFi technologies, imposing manyÂ technical challengesÂ for all participants in the ecosystem. Current testing is focused mostly on functionality using very specificÂ MATLAB Models for 802.11 ax.
With this landscape in the backdrop, how does one start preparing and understanding what it will take toÂ test a full-fledged 802.11axÂ solution? How is it possible to model what the user is going to experience. We being aÂ Test & Measurement company, asked this question to ourselves, a year back. I would like to share our thought process here.
We need to go back to basics and askÂ what is uniqueÂ in 802.11 ax? Unique does not mean just the features like OFDMA based physical layer multiplexing the users, higher MIMO or higher QAMs. We need to understand theÂ User ExperienceÂ aspect of AX solution, rather than focusing merely onÂ technology featuresÂ that are tangible. For user experience testing, basics are different. We need toÂ predict the usageÂ and try toÂ createÂ a similar environment andÂ measureÂ acceptable KPIs.
High Density WLAN with current technology
High-densityÂ wireless LAN network will have aÂ large number of clientsÂ andÂ more number of Access points within a specific area. Big campuses with multiple floors, distributed buildings/ large apartments, enterprises, and large event spaces are considered high density due to the number of access points and devices connected to the network
The most commonÂ examples ofÂ high densityÂ environmentsÂ include:
- Stadiums, Arenas and Concert Halls
- Conference Halls, Exhibition Halls
- Campuses & lecture halls
- Transport hubs â€“ airports, railway stations
- Transport systems â€“ metros, trains, aircrafts, cruise liners
High-density environments with more number of devices and Access Points always createÂ challengesÂ for designing, deploying and testing the network.Â ConnectivityÂ has become as indispensable to our current generation as the air we breathe. Failing toÂ ensure strong WiFiÂ in aÂ high-density environmentÂ can seriously impact service objectives and overall image. WiFi users will expectÂ seamless availability and superior experience all the time.
The number of devices accessing the network and number of access points in dense deploymentsÂ make the infrastructure truly uniqueÂ and demanding. The density along with applications running on these devices are driving theÂ demand for high reliability, andÂ high-performance connectivity. Bandwidth requirements for some popular high bandwidth consuming applications are as follows:
|Streaming Audio||128-320 kbps|
|Video Streaming||728 kbps|
|Video Conferencing||1.5 Mbps|
|HD video streaming||768kbps â€“ 8 Mbps|
|4K video streaming||8 Mbps â€“ 20 Mbps|
For example, let us consider a large hotelÂ conference hallÂ that accommodates 1000 clients. Assume that there is aÂ High-density WiFiÂ network that is capable of handling 1000+ with an SLA of 2Mbps per user. When it comes to theÂ real world, can you assure that all 1000 users can simultaneouslyÂ stream a 2MbpsÂ demo video without interruptions and artifacts? How do youÂ verify the sameÂ before you give access to users? Do you think it will be easy toÂ replicateÂ the scenario with 1000 real devices?
How do you test User Experience
WLAN Installers focus on coverage rather thanÂ End-User Experience. To the end user, networkÂ experience mattersÂ irrespective of the technology deployed. You can not just rely onÂ theoretical numbersÂ and believe that network would work fine with 1000s of users. How can you thenÂ guarantee the user experienceÂ in dense deployments like Stadiums, Auditoriums, and Airports?
How to prepare for 802.11 ax?
HEWÂ is also working towards developing and understanding High DensityÂ deploymentÂ scenarios. We also want toÂ understand 802.11axÂ in the following stages (From HEW group):
- TrendsÂ â€“ What are the trends that are redefining WiFi usage?
- Usage ModelsÂ â€“ Based on trends, what are the new usage models, that drive goals/directions.
- Goals of the technologyÂ â€“ Based on Usage Models, what goals are defined for 802.11ax. What is unique in 802.11ax compared to previous standards?
Understanding these, we will be able to get clarity on theÂ real world scenariosÂ from the 802.11ax perspective andÂ replicate the same in a LABÂ to verify the goals
1. Trends: There are three majorÂ trends
- Increased usage of mobile devices â€“Â mostÂ environments will involve high density of STAs and/or Access Points
- User demand for Wi-Fi anytime and anywhere has created demand in locations e.g. airports.
- Increased usage of WiFi leads to an increased density in traditional Wi-Fi environments as well e.g. apartments and enterprises
- Growing use of WiFi outdoors e.g. parks, campus, streets and events
- 2.4Ghz is congested and 5Ghz will follow soon as WiFi by design is not meant for high density
- Evolution of WiFi Applications
- per user average real-world throughput follows a regular increase (pushed by higher resolution video for instance)
- cloud services generating more Uplink traffic
- more and more peer-to-peer applications
- Advent of the Internet Of Things
- By around 2020, 50 Billion devices will hit wifi networks. They will demand smaller but regular packet transfer capabilities, again a super High-Density scenario.
2.Â Â Usage ModelsÂ â€“ Let us delve deeper and understand components, classification and requirements posed by usage models derived from the above trends.
Usage scenario can be broken into a few components as below
- Pre-conditionÂ â€“ Initial conditions before the use case begins
- Environment â€“ Vertical or location for the network
- On Desk or in cubicle (short range, line of sight)
- Conference Room (medium range, line of sight)
- High density
- Hotspot in Public Places
- Airports, Bus Stations, Train Stations
- Restaurants, Exhibitions Halls, Shopping Malls
- Outdoor Hotspots
- Stadiums, Recreational places like Parks, Theatres
- Auditoriums/lecture halls, classrooms in schools, colleges
- Remote medical assistance in hospitals
- Flights, Trains, Buses, Ships
- Traffic ConditionÂ Â â€“ Background traffic or interference that is expected during the scenario e.g. interference from bluetooth
- ApplicationsÂ â€“ A few applications to consider are Video Conferencing, Virtual Desktop Infrastructure, Progressive Streaming, Interactive Multimedia & Gaming and more
- User ActionsÂ â€“ Actions by user or device.
Usage Model predicted going forward can be categorized as follows
- High density of APs and High density of wireless clients per AP
- Ex: Shopping malls, airport, exhibition halls
- High density of clients â€“ Indoor
- Ex: Auditoriums, buses, wireless office
- High density of APs & low / medium density of clients per AP
- Ex: Dense apartment building, community WiFi
- High density of APs and high density of clients per AP â€“ Outdoor
- Ex: Dense urban street, pico-cell street deployment, Macro-cell street deployment
- Throughput demanding applications
- Ex: Healthcare, production in the stadium, smart car
3. GoalsÂ â€“ Â Here they are
- Improve Spectral Efficiency and Area throughput
- Improving real-world performance in indoor and outdoor deployments
- In the presence of interfering sources, in indoor and outdoor deployments
- In moderate to heavy user loaded wifi Access Points.
Till now, technology chased high peak throughput in ideal condition. End to that era with 11ax. The goals of 11ax areÂ efficiency,Â ability to work with interference,Â the ability to work in densityÂ and so on. There is an acceptance that the real world is far from ideal, so what can be achieved in ideal condition can at best maybe a lab test case.
The uniqueness of Goals compared to previous technologies
The uniqueness of 802.11ax compared to 11ac/b/g/n is categorized with respect to four elements as follows:
- With respect to the environment
- Hotspots for public access and cellular offload in dense areas for indoor & outdoor like street deployment use cases are unique
- With respect to applications
- 802.11ax focus on the user experience of all the clients in high dense scenarios (with a large number of clients and a large number of applications)
- With respect to objectives
- unlike 802.11ac which improved theoretical peak throughput, the target of 802.11ax will be to increase Wi-Fi efficiencyÂ by improvingÂ user experienceÂ by a fair and efficient repartition of throughput among all users/applications in real-world scenarios and to increase overallÂ capacity per area
- With respect to metrics
- The metrics that are in consideration are per user average Throughput, Area Throughput (taking MAC and PHY overheads)
Aletheaâ€™s approach to testing at scale
Alethea offers a solution,Â Distributed Device Architecture (D2A)Â to validate high-density deployments. D2A helps toÂ validateÂ theÂ WiFi infrastructure end-to-endÂ effectively. With a flexible,Â distributed & scalable architecture, ability to emulate more thanÂ 2000 stateful clients,Â real traffic generationÂ and much more, the tool is in use by WLAN equipment manufacturers, chip vendors, service providers, and enterprise users to make sure that the products and networks they offerÂ meet customer expectations.
Currently, D2A canÂ emulate 802.11 a/b/g/n/acÂ clients and supports maximum throughput up toÂ 1.3 Gbps / Radio Head.Â 802.11AX isÂ coming soonÂ and we will continue to support all theÂ latest and legacy technologyÂ standards toÂ test the scenariosÂ with a mix of different wireless devices.
Alethea strives towardsÂ Perfecting BroadbandÂ and help the WiFi Ecosystem meet end usersâ€™ expectations.