IEEE 802.11ax

What is 802.11ax Wi-Fi?

Wi-Fi experiences a seismic change approximately every five years – and 802.11ax is the latest generation of Wi-Fi that bridges the performance gap towards ten gigabit speeds. The new Wi-Fi standard will deliver faster network performance, connect more devices simultaneously and transition Wi-Fi from a ‘best-effort’ endeavor to a deterministic wireless technology that has become the de-facto medium for internet connectivity. With an expected four-fold capacity increase over its 802.11ac Wave 2 predecessor, 802.11ax deployed in dense device environments will support higher service-level agreements (SLAs) to more concurrently connected users and devices with more diverse usage profiles.

IDC Technology Spotlight Paper

Evaluating the New 802.11ax WiFi Standard and What It Will Mean for Enterprises. Read More.

802.11ax offers a range of technical enhancements to optimize spectral efficiency, increase throughput and reduce power consumption. These include:

OFDMA and MU-MIMO

Orthogonal frequency-division multiple access (OFDMA) and multi-user multiple-in multiple-out (MU-MIMO) are techniques that increase reliability and efficiency in the unlicensed Wi-Fi spectrum. In contrast to previous generations of Wi-Fi, OFDMA enables Wi-Fi to become deterministic, as devices consistently receive more attention with minimal contention. This helps stabilize Wi-Fi performance, especially in higher density environments.

Each Wi-Fi channel is divided into smaller sub-channels known as Resource Units. The AP decides how to allocate the sub-channels, as each individual RU (or sub-channel) can be addressed to different clients that are serviced simultaneously. This technique improves the average throughput (per user) by creating a narrower, albeit dedicated sub-channel. Moreover, OFDMA boosts spectral efficiency and reduces latency, while supporting heterogeneous users (i.e., IM, email or light web browsing versus large downloads).

It is important to note that OFDMA and MU-MIMO provide complementary techniques to concurrently serve multiple users. More specifically, OFDMA is best utilized when multiple connections transmit limited amounts of data. OFDMA which is effective at all ranges – close, medium and far – offers lower latency and can be used to mitigate OBSS interference issues. Meanwhile, MU-MIMO best serves multiple user with full buffer traffic and is most effective at close-to mid-range.

Uplink MU-MIMO

With 802.11ax, OFDMA and MU-MIMO are supported in downlink (from AP to stations) and uplink (from stations to AP). It should be noted that the AP schedules the transmissions in both directions. This contrasts with pre-802.11ax networks (especially in uplink direction), where resource allocation is contention-based, with individual stations making the decision to appropriate the medium and transmit data. As stations increase, so does contention.

Sub-carrier spacing and MAC/PHY enhancements

With 802.11ax, sub-carrier spacing is reduced, thereby enabling a 4X jump in the number of available data-tones and significantly increasing maximum PHY rates. Moreover, additional data tones help support multiple users in conjunction with OFDMA. 802.11ax also optimizes spectral efficiency with more tones/channel, reduces overhead, bolsters outdoor operation and facilitates a quantum jump in highest achievable PHY rates. In addition, 802.11ax APs maintains two separate network allocation vectors (NAVs) to prevent misbehavior and collisions. Last, but certainly not least, 802.11ax features a 1024-QAM constellation (in contrast to 256-QAM for 11ac), enabling a 25% physical data rate increase that in combination with other 802.11ax techniques offer up to 4x the capacity.

Target Wake Time

First introduced in the IEEE 802.11ah standard, target wake time (TWT) enables scheduled sleep and power-on (awake) times, along with pre-negotiated wake times between AP and clients to avoid on-the-air contention amongst client devices. This helps make air utilization more efficient and enhances the battery life of client devices.

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802.11ax 

Allgemeine Netzwerktechnologien

Was es bedeutet:

802.11ax ist der neueste Wi-Fi-Standard des IEEE. Dieser neue Standard bringt viele große Vorteile mit sich.  Er erweitert die MU-MIMO-Techniken (Multiple User – Multiple Input, Multiple Output), um gleichzeitig bis zu acht Streams zu übertragen. Zum Vergleich: Bei 802.11ac Wave 2 waren es nur vier Streams. Darüber hinaus optimiert der Standard MU-MIMO durch OFDMA-Technologie (Orthogonal Frequency Division Multiple Access), mit der jeder MU-MIMO-Stream in vier zusätzliche Streams aufgeteilt werden kann. So lässt sich der effektive durchschnittliche Durchsatz pro Benutzer auf das Vierfache steigern.

Und mit neuen Modulations- und Kodierungssätzen samt 1024-QAM können mehr Daten pro Paket übertragen werden, was den Durchsatz weiter steigert. Darüber hinaus verbessert der Standard den allgemeinen physischen bzw. MAC-Layer und das Batteriemanagement.

Den alten Standard können Sie sich so vorstellen: In einem Geschäft wartet eine lange Schlange von Kunden auf einen Kassierer. Bei 802.11ac und MU-MIMO waren es dann vier Kassierer mit jeweils vier Warteschlangen. Und 802.11ax erweiterte das Ganze auf acht Kassierer mit jeweils acht Warteschlangen. Mit OFDMA kann der Kassierer jetzt mehrere Kunden gleichzeitig bedienen, wenn er Zeit hat. Stellen Sie sich vor, er könnte einfach schon den nächsten Kunden bedienen, während der erste noch einmal schnell zum Kühlregal rennt, weil er etwas vergessen hat.

Warum spielt das eine Rolle:

Wi-Fi kann jetzt in prall gefüllten Stadien oder Flughäfen implementiert werden – mit Hunderten oder Tausenden von Geräten, die um die verfügbare Bandbreite kämpfen und die der aktuelle Standard 802.11ac nur mit Mühe unterstützen kann. Mit 802.11ax wird der Durchsatz pro Benutzer in ultradichten Szenarien auf das Vierfache gesteigert.

Mit der Kombination aus diesem neuesten Standard und der Ultra-High-Density Technology Suite von Ruckus gewährleisten Sie bestmögliche Benutzererlebnisse.