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 

Technologies sans fil générales

De quoi s’agit-il :

802.11ax est la toute dernière norme sans fil IEEE du Wi-Fi. Cette nouvelle norme apporte des améliorations considérables sur plusieurs fronts.  Elle étend les techniques MU-MIMO (entrées multiples sorties multiples multi-utilisateurs) afin de transmettre simultanément sur un maximum de huit flux, comparé aux quatre flux du 802.11ac Wave 2. En outre, elle se greffe sur MU-MIMO avec la technologie OFDMA (multiplexage d’accès par porteuses orthogonales) qui permet de diviser chaque flux MU-MIMO en quatre flux supplémentaires, quadruplant ainsi le débit par utilisateur.

L’introduction de nouveaux ensembles de modulation et codage avec 1024-QAM permet de transmettre plus de données par paquet et d’améliorer le débit. Elle améliore également l’efficacité de la couche physique et MAC et la gestion de l’alimentation des batteries.

Si la norme précédente peut être comparée à une longue queue de clients qui se forme devant la caissière d’un magasin, le MU-MIMO peut être considéré comme une technologie qui a créé quatre caissières desservant quatre files de clients avec la norme 802.11ac. La norme 802.11ax a étendu cette capacité à huit caissières desservant huit files de clients. Avec la technologie OFDMA, la caissière peut désormais gérer plusieurs clients à la fois dès qu’ils sont libres. Imaginez une caissière capable de servir le prochain client si le premier client décide qu’il a oublié quelque chose et quitte soudainement la file.

Intérêt de la solution :

Le Wi-Fi est à présent déployé dans les stades et aéroports où des centaines de milliers d’appareils se disputent des bandes passantes, ce que la norme 802.11ac actuelle a du mal à gérer. La technologie 802.11ax quadruple le débit moyen par utilisateur dans les environnements à très forte densité.

Combinée à la suite technologique pour les environnements à très forte densité de Ruckus, la toute dernière norme vous permet de fournir le meilleur en matière d’expérience utilisateur.