Today, Wi-Fi is a ubiquitous necessity of modern life – nearly a utility. It is the primary wireless communication channel for billions of users around the world as they go about their daily business at home, work, or traveling. The Institute of Electrical and Electronic Engineers (IEEE) anticipates that there will be 50 billion connected wireless devices by 2022. Gartner estimates that an average family of four will have about 50 connected devices by then.
Wi-Fi, in all of its forms, has been immensely popular and, one of the wireless industry’s biggest success stories. Wi-Fi is one of the most inexpensive wireless connection options for most of popular use cases. Eighty percent of wireless traffic goes over Wi-Fi connections, and approximately 50 percent of all Internet traffic commutes over Wi-Fi. This trend will only increase as more and more data is routed over Wi-Fi infrastructure, around the world.
However, many users do not understand that Wi-Fi comes in many flavors, with monikers such as 802.11a, b, g n, ac or ax, each with varying degrees of performance. But the impending 5G ecosystem will lay down requirements to take Wi-Fi to the next level. This article will discuss why the next generation of Wi-Fi will play a critical role in this brave new wireless world.
802.11ax – The Justification
Technology trends, markets, and user behaviors are now changing at a mind-boggling pace. User behavior, for one, is changing. Consumers used to care, mainly, about download speeds; a trend driven by popular applications such as Napster, YouTube, Gmail and more. Today, however, users upload much more data than before, using applications such as Twitter, Periscope, Facebook Live, Snapchat, and more. In fact, in contexts such as sports events or music concerts, it has been observed that upload demand is at par with download demand.
If one were at the 2017 Super Bowl in Minneapolis, or if one has ever been at a live sporting event, one knows how difficult it can be to maintain a sufficient Internet connection in such a large crowd. At last year’s game, Extreme Networks reported that 35,430 fans used the stadium Wi-Fi network throughout the game and transferred a record-breaking 11.8 TB of data – 1.68 TB more than the previous record for Wi-Fi network data transferred during a sporting event. Today’s networks, simply, are not prepared to keep up with that much demand from so many devices.
A second factor is the explosion in the number of Wi-Fi connected devices, especially Internet of Things (IoT) devices connected via Wi-Fi, such as security cameras, thermostats, and printers. These new IoT devices also upload data to the cloud, regularly, and need to be mindful of their battery power consumption.
Wi-Fi has worked tremendously well in low-density environments such as the home. But as more of us use it in high-density environments, performance degradation becomes evident. It can become extremely frustrating to try to get on a network in a crowded venue such as an airport, shopping mall, etc. This is, usually, because legacy Wi-Fi standards were not designed with density in mind; i.e., a lot of users accessing the wireless frequency channel, simultaneously.
For example, in a crowded venue such as an airport or a shopping mall, using the 2.4 GHz band, most of the airwaves are occupied by devices contending for the medium instead of communicating data. This is because Wi-Fi was designed using a protocol called “Carrier Sense Multiple Access / Collision Avoidance” (CSMA). CSMA, as a technology, emulates how humans converse in small groups. We all typically wait our turn to speak when some else is speaking. This is exactly how CSMA works. The Wi-Fi device listens to the airwaves and only transmits when the airwaves are clear.
This worked phenomenally in the early years of Wi-Fi, when there were not as many Wi-Fi devices, but today devices are not getting their turn to “speak” in crowded environments. Additionally, the unlicensed spectrum band also hosts a lot of other technologies other than Wi-Fi, which can make the connection experience feel like “best effort” instead of “guaranteed availability.”
The Wi-Fi industry has responded by designing a new, sixth Wi-Fi standard called 802.11ax to solve the density and capacity issues. While previous Wi-Fi standards were designed around maximizing “peak speeds” for a limited number of devices and users, this standard is designed for improving user experience in dense environments. This, by maximizing “average speeds” for a large number of devices, while preserving the benefits of legacy Wi-Fi technologies, such as backwards compatibility and low cost.
Reliable and ubiquitous Wi-Fi connectivity is important – it can even save lives. The wildfires that burned through California last year cause more than $3 billion in damages, destroyed nearly 7,000 homes and took at least 42 lives. The chaos drove thousands of families to evacuation centers across the state. In those crowded centers, communicating with the outside world became increasingly difficult, or in many cases, nearly impossible.
When too many people attempt to connect their devices and overloaded Wi-Fi networks, like the ones in evacuation centers, the current Wi-Fi standard, 802.11ac, cannot always keep up. 802.11ax can stay lightning-fast and ultra-reliable in such critical situations when one is stranded in highly-crowded environments. It makes better use of the limited spectrum available and can handle more simultaneous devices on a single access point. It is a valuable capability that can make a world of difference under any circumstance, whether it is dire, as one is able to check in via video chat with loved ones, or in social situations when one is live-streaming their favorite concert.
Because 802.11ax is so efficient, 802.11ax-equipped devices do not need to work as hard. They can stay connected for longer periods of time and experience up to seven times less battery drain. When access to a charger is not always an option, the resulting extended battery life can bring huge peace of mind. Being displaced by a natural disaster is hard enough without the added challenge of overstretched and inefficient Wi-Fi. 802.11ax Wi-Fi promises greater access to critical services in a time of need.
This new 802.11ax technology is based on six major technological innovations:
· Orthogonal Frequency Division Multiplexing Multiple Access (OFDMA), which increases capacity
· 1024-QAM, which increases speed leaving the airwaves unoccupied for other devices by packing more information in the transmitted signal – indirectly increasing speeds for other devices
· Much increased Wi-Fi range using features such as dual-carrier modulation and Uplink-OFDMA
· Newer scheduling scheme to ensure efficiency of the airwaves
· Target Wake Time (TWT) ensuring increased battery life, especially for battery constrained IoT devices
· Basic service set coloring allowing overlapping Wi-Fi networks to co-exist and be good neighbors
It’s worth exploring each of these features individually.
OFDMA – OFDMA forms the backbone of 802.11ax and makes the 6th generation of Wi-Fi more efficient, more reliable, and more versatile than previous generations. This innovation allows 802.11ax to support many devices at the same time, and to avoid the interference that causes congested Wi-Fi today.
A major factor limiting current Wi-Fi is collisions. This is when multiple devices transmit at the same time and interfere with each other. Each device wants to use the entire available wireless channel.
With OFDMA, each wireless channel of the spectrum is separated into dozens, or even hundreds, of smaller subchannels, each with a slightly different frequency. By then turning these signals through right-angles, so that the subchannels do not interfere with one another, they can be stacked closer together. Rather than waiting in line for their turn to transmit across the whole frequency band, multiple devices can share each channel simultaneously.
OFDMA also adds flexibility to how spectrum is used, only allocating parts of the spectrum to each wireless device, proportional to its needs. This is the Wi-Fi upgrade – with vastly increased capacity – that will effortlessly power the IoT, while simultaneously downloading data, streaming 4K video, and voice.
OFDMA also allows routers to dynamically adjust signal strength to improve reception for devices further away from the router. Routers can reduce power to devices that are closer and boost power to devices that are further away while meeting regulatory power emission requirements. This 802.11ax feature is essential for consumers wanting to future-proof their connected homes.
Smart devices, such as thermostats, doorbells, refrigerators, light bulbs, and other Wi-Fi connected devices transmit small packets of data to the cloud to receive instructions or report on performance. Using OFDMA, 802.11ax efficiently combines these small packets across multiple users and delivers gains of up to 6X in uplink, or upload, performance. 802.11ax transitions Wi-Fi from a postman, delivering mail to one house at a time, to an email server, handling many messages to many users, simultaneously.
The last generation of Wi-Fi, 802.11ac, introduced peak gigabit speeds by adding the ability for devices to send traffic along wider channels – 80 MHz – of spectrum, and by simultaneously using 2.4 GHz spectrum. Now, 802.11ax devices can achieve even faster speeds, averaging up to 6X faster than the last generation of Wi-Fi.
802.11ax is capable of using up to 160 MHz wide channels – double the bandwidth – as well as faster modulations schemes, such as 1024-QAM, outperforming today’s best-in-class Wi-Fi devices. 802.11ax uses the available spectrum much more efficiently, which delivers higher average speeds to many more devices. By using uplink and downlink OFDMA technology, more data can flow simultaneously, stacked like a double-decker bus. 802.11ax also has protocol changes that pack signals closer together – longer OFDM symbols – with reduced overhead, compared to current Wi-Fi devices.
Range– 802.11ax also increase the range of Wi-Fi connections. This is because it solves a problem that exists today – asymmetrical Wi-Fi connections. Access points (APs) have more range than mobile devices. This is because APs are usually plugged into a power source, hence, battery life is of no concern. They can transmit higher power than the mobile devices. Additionally, most APs have many more antennae, typically four to eight, which increases their range.
Meanwhile, mobile phones need to optimize battery life and, therefore, transmit less power than their infrastructure counterparts and have a limited number of antennae, typically two. This limits the range of a Wi-Fi user as the phone cannot reach the AP, while the AP can reach the phone.
With 802.11ax, the phone can concentrate its energy in a narrower channel, as narrow as 2 MHz, and reach the access point by boosting the peak power transmitted, and still be compliant with spectrum regulations. This feature solves the asymmetry in legacy Wi-Fi and can significantly increase range.
Target Wake Time – TWT allows the Wi-Fi radio in battery-powered devices, such as phones, to go to sleep when not exchanging data. This lowers power consumption and saves device battery. With TWT, 802.11ax-capable routers and mobile devices can negotiate the sleep cycle, according to the data traffic, so that they only wake up when it is their turn to communicate, allowing them to preserve the battery. Also with TWT, devices can be programmed to wake up at the same time to take advantage of OFDMA so that they can communicate at the same time, and share the channel, hence boosting the capacity of the network. The result is a well-synchronized data flow that allows all devices to connect simultaneously, based on their needs. This improves the user experience as video, voice, data, and IoT traffic is proportioned and prioritized effectively.
BSS Coloring – 802.11ax also introduces a scheme to reduce interference and use the spectrum even more efficiently. This is accomplished by allowing routers, and different networks operating on the same channel, to decide, intelligently, when they can transmit simultaneously. Using this “spatial reuse” technique, each router and device on the same network transmits data with a unique identifier. Wi-Fi listens for interference before sending data and will back off if it senses data in the band.
With 802.11ax, when a router, or a device, is listening before transmitting data, they are more aggressive if they hear data from a different color since that data is going to a different router further away. The standard plans for two different operating modes. One is optimized for dense, managed networks such as stadiums and enterprises, where the siting of routers is carefully planned. The other is optimized for scenarios like a busy city block, where routers and devices are less uniformly distributed. This allows for denser deployment of APs to deliver increased Wi-Fi capacity to more users while keeping interference between different networks under control.
This is akin to a restaurant where diners at one table defer to each other but not to those occupying adjacent tables. BSS coloring can significantly increase average throughput in dense environments such as crowded apartment buildings.
Guard Interval – For outdoor devices requiring smaller amounts of data, 802.11ax allows data to be sent across a smaller sliver of the spectrum with extra protections as the data move longer distances. 802.11ax can improve outdoor Wi-Fi coverage for these devices by 50 percent. This is especially important for many cities as they work hard to increase amenities to their citizens.
Spectrum and 160 MHz-channel Width – Regulators around the world are looking to give Wi-Fi a boost by expanding the amount of available unlicensed spectrum. If 802.11ax Wi-Fi is a highly efficient new race car, you can think about spectrum as the number of lanes on a highway. Upgrading to an incredible vehicle is great, but it is even better when there are sufficient high-speed lanes for all to drive on. There is a critical need for more fast lanes (more spectrum) to make the best use of Wi-Fi technologies like 802.11ax, which can operate on, up to, 160 MHz channels.
A broad range of technology companies – from major semiconductor OEMs to mobile operating system vendors to content providers to enterprise Wi-Fi vendors support this effort. The reason is that there are not enough contiguous 160 MHz channels to take advantage of 802.11ax devices’ ability to double up on speed. Regulators have also stepped up and are looking at opening up the 6 GHz mid-band spectrum for the use of unlicensed services such as Wi-Fi while taking adequate steps to protect incumbent users in those frequency bands.
Making 802.11ax a Reality
One of the major factors in the success of Wi-Fi technologies is due to interoperability. Every device that bears the Wi-Fi certified logo works with another that bears the same logo. A lot of this magic is done at the Wi-Fi Alliance (WFA). While standards such as 802.11ax are developed by the IEEE, the nitty-gritty work of ensuring that the devices in the market work as expected is performed at WFA. For a device to be branded as “Wi-Fi Certified”, at least five infrastructure vendors, five mobile vendors, and three chipset vendors have to pass a stringent test plan to ensure that there are no interoperability problems in the field.
5G and 802.11ax– 802.11ax will help telecom carriers manage the cost of the rollout of 5G services. 5G is driven by three factors required by IMT-2020: Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC), and Ultra Reliable and Low Latency Connections (URLLC).
eMBB aims to increase the data rate for the average user, mMTC aims to provide scalable network services to serve the anticipated IoT market, and URLLC aims to serve mission-critical services by providing low latency connection for applications such as self-driving cars, remote-surgery, etc. All these requirements require network densification, i.e., packing a lot of infrastructure equipment in a dense manner so that a lot of users can be served with the metrics imposed by eMBB, mMTC, and URLLC – the building blocks of 5G.
However, this is very expensive. Each of these network nodes needs to be connected to power and a fiber connection, often leading to complex work projects involving digging of streets. That makes the rollout expensive, even if worthwhile. This is where 802.11ax comes to the rescue. Wi-Fi is ubiquitous and with the lowest cost of wireless connection when measured on a cost/bit basis.
Cellular service providers use Wi-Fi today to offload cellular traffic on to Wi-Fi networks. This helps to keep the overall performance and cost of their network under control, and affordable to end users, as traffic demands rise. This strategy has enabled the rollout of 4G services across the world in a cost-effective manner. When more users are on Wi-Fi networks, cellular networks are less stressed, leading to lower capital expenditure, and downstream savings for users. This same trend is likely to be repeated during the installation of 5G networks in the future, 802.11ax will augment the capacity needs, in a low-cost manner, to profit both service providers and their customers.
802.11ax Across Use Cases
802.11ax will bring myriad benefits to consumers, service providers such as telecommunication companies, multiple service operators, and business owners alike. These benefits include better network performance, up to 6X faster in average speeds in a dense Wi-Fi network deployment; the ability to reliably connect more devices; and a better user experience where one can more easily share videos, photos, or memories without friction.
802.11ax is the first Wi-Fi generation to be optimized, specifically, for live streaming applications and emerging virtual and augmented reality activities that generate high volumes of upload traffic, particularly when that traffic is created simultaneously. MU-MIMO (Multi-user – multiple-input and multiple-output) technology brings further gains in capacity by allowing multiple devices to transmit, simultaneously, over the entire channel, using smart antennas to separate and receive the signals. MU-MIMO is the great enabler for higher quality video streaming and faster uploads.
OFDMA and MU-MIMO complement each other to make 802.11ax highly efficient. This permits the latest generation of Wi-Fi to be optimized for both networks with a very large number of devices, as well as networks where the highest per-user throughput is most important.
802.11ax and Enterprise
The high performance of 802.11ax is also important in the modern enterprise, where collaboration often occurs among large, distributed teams with real-time applications like Skype, FaceTime, or WebEx. Enterprises are also increasingly using data-intensive, cloud-based tools for file sharing, backup and enterprise resource management. 802.11ax is the first Wi-Fi designed with these uses in mind. With 802.11ax enterprises see an upgraded network with multiple features to improve the range, robustness, and reliability of Wi-Fi connections.
The Problem Solver: 802.11ax
802.11ax also addresses a problem with today’s Wi-Fi that has plagued engineers and consumers alike – the “sticky client problem.” A given Wi-Fi device “sticks” to a certain access point even as it moves out of range and closer to another access point. This impacts Wi-Fi speed and quality for that device and for other devices trying to use a now-overcrowded access point. Luckily, the latest Wi-Fi standard, 802.11ax can adeptly tackle this challenge in conjunction with other Wi-Fi features such as “Agile Multiband” (multiband optimization – MBO) and “optimized connectivity experience” (OCE) technology.
Leveraging its greater bandwidth access and capacity to distribute data traffic more efficiently along and across spectrum bands and other devices, 802.11ax access points better communicate network congestion metrics such as channel utilization and estimated airtime fraction the user’s device. This information helps mobile devices select the right access point, band, and channel during initial join or while one roams within or across networks.
802.11ax enabled Wi-Fi access points have more capacity in general and can send a clearer picture to devices on the network of their expected performance at the moment. These attributes help a multitude of wireless devices to figure out where to connect and experience better performance when they are connected.
There has been a push at the WFA to optimize Wi-Fi for service providers such as telecom companies, cable companies, etc. that need to optimize the technology as a managed service. This means that various attributes that Wi-Fi has historically lacked needed attention and upgrading. In response, the WFA designed a program called Vantage. It is a grouping of several certification programs such as MBO, OCE, and Passpoint. MBO or “Wi-Fi Certified Agile Multiband” ensures that a device can join the network on a channel, or band that is the least cluttered and can provide great Internet experience. OCE or “Wi-Fi Certified Optimized Connectivity Experience”, ensures that when one experiences a slow connection, the device can, intelligently, switch to another network or even to cellular connection, to ensure uninterrupted services. Passpoint aims to reduce the friction of authentication entering passwords every time one roams to connect to a Wi-Fi network. These technologies, along with 802.11ax, will go a long way in addressing operator and cable companies concerns.
Additionally, the WFA has mandated that WPA3 security be a prerequisite for a device to be 802.11ax certified. WPA3 is an improvement over WPA2 with new features such as 192-bit encryption, “Shared Authentication of Equals” (SAE), and “Opportunistic Wireless Encryption” (OWE). These upgrades will ensure that Wi-Fi’s security protocols are up to date with user’s needs and expectations.
When one talks about Wi-Fi development, there is, essentially, two sides to the story – the technical evolution and revolution. 802.11ax represents a revolution; a generational upgrade that will be noticed by consumers, businesses, and service provider’s alike.
Along with complementary technologies such as MBO, OCE, Passpoint, and WPA3, our Wi-Fi experience is about to change for the better, providing reliable and inexpensive connectivity to billions around the globe. This technology will be a game changer for dense, developing countries, such as China and India that have overcrowded Wi-Fi networks, and will prove to be beneficial for the world as a whole.
Vijay Nagarajan is a Senior Director, Product Marketing for Broadcom Limited’s Wireless Communications and Connectivity Business Unit. He is responsible for Broadcom’s Wi-Fi, Bluetooth & GNSS products for mobile devices. Prior to his role at Broadcom, he was with Atheros Communications, and Tensorcomm Incorporated, working on various wireless technologies including CDMA-based 3G networks, Wi-Fi and Bluetooth. He is also a well-cited wireless industry analyst whose opinions and analysis of the mobile phone market and value chain have been referenced in several online publications including Forbes, EETimes, and thestreet.com. He has over 40 patents on mobile receiver architecture and design techniques for 3G and 4G networks. HE also has multiple peer-reviewed international technical papers, including IEEE publications, in coding technique for wireless and storage systems. He holds an MS in Electrical Engineering from the University of Colorado, Boulder and a BS degree from the College of Engineering, Guindy, (Anna University) India.