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.

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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 

Tecnologie wireless generali

Cosa significa:

802.11ax è lo standard wireless IEEE Wi-Fi più recente. Questo nuovo standard porta con sé notevoli miglioramenti su più fronti: per esempio, espande le tecniche MU-MIMO a entrate e uscite multiple per consentire di trasmettere contemporaneamente fino a otto flussi rispetto ai soli quattro di 802.11ac Wave 2. Inoltre, potenzia ulteriormente MU-MIMO grazie alla tecnologia OFDMA di accesso multiplo a divisione di frequenza ortogonale che consente che ciascun flusso MU-MIMO sia suddiviso in quattro flussi aggiuntivi, quadruplicando il throughput effettivo medio per utente.

L'introduzione di nuovi set di modulazione e codifica con 1024-QAM consente la trasmissione di più dati per pacchetto, il che determina un throughput superiore. Migliora inoltre l'efficienza di strato MAC e di strato fisico complessiva, nonché la gestione della batteria.

Se lo standard precedente era come una lunga fila di clienti in attesa all'unica cassa in un supermercato, MU-MIMO ha portato il numero di cassieri a quattro per quattro diverse file di clienti in 802.11ac. 802.11ax ha ulteriormente aumentato il numero di cassieri per servire otto diverse file di clienti. Con OFDMA, il cassiere può inoltre gestire più di un cliente alla volta quando è libero. È come se il cassiere fosse in grado di servire il cliente successivo quando quello di turno decide di fare una corsa a prendere un oggetto che aveva dimenticato!

Perché è importante:

La Wi-Fi viene installata in stadi affollati o aeroporti pieni di persone e di centinaia di migliaia di dispositivi che bramano larghezza di banda. L'attuale standard 802.11ac non sempre riesce a soddisfare questa esigenza. 802.11ax aumenta il throughput medio per utente di 4 volte negli scenari ad alta densità.

Lo standard più recente, combinato alla Suite tecnologica per ambienti a elevatissima densità di Ruckus ti fornisce la possibilità di garantire le esperienze migliori possibili per i clienti finali.