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


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 是最新的 Wi-Fi IEEE 无线网络标准。这一全新标准在多个方面都取得了重大进展。  它可以扩展多路输入、多路输出 (MU-MIMO) 技术,最多可以同时在 8 个流上传输数据,而在 802.11ac Wave 2 上可以同时在 4 个流上传输数据。此外,它还可以利用正交频分多址接入 (OFDMA) MU-MIMO 技术将每个 MU-MIMO 流分割成四个额外的流,进而将每个用户的有效平均吞吐量提高四倍。

通过 1024-QAM 引入全新的调制方式和编码集,允许每个数据包传输更多的数据,从而提高吞吐量。它还提高了整体物理和 MAC 层的效率,还可以改善电池的功率管理。

如果说早期的标准就像在杂货店排队等一个收银员一样,那么 MU-MIMO 现在则相当于在 802.11ac 中将其扩展为可以为 4 排顾客同时提供服务的 4 个收银员。802.11ax 则将其进一步扩展为可以为 8 排顾客提供服务的 8 个收银员。有了 OFDMA,现在收银员可以在顾客空闲时同时处理多个顾客。试想一下,如果第一个顾客决定快速跑回去取东西,收银员就可以为下一个顾客提供服务。


现如今,Wi-Fi 往往会部署在人流密集的体育场或繁忙的机场,那里会有数十万台设备争抢带宽,现在的 802.11ac 标准在支持这一点上还存在挑战。在高密度场合,802.11ax 可以将每个用户的平均吞吐量提高 4 倍。

凭借结合全新标准的 Ruckus 超高密度技术套件,您可以轻松提供最佳的最终用户体验。