The new standard 802.11ax for Wi-Fi goes beyond 802.11ac wireless
A new standard for high speed multi-gigabit WiFi is emerging: IEEE 802.11ax. Current WiFi products use chips based on the IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11 and IEEE 802.11ac standard have really only begun rolling out, an effort to deliver an enhancement called IEEE 802.11ax that promises to deliver faster and longer range Wi-Fi networks.
The up-coming 802.11ax is as an enhancement of 802.11ac in the unlicensed 2.4 and 5GHz bands of spectrum, and should be a natural upgrade. The upgrade will offer significant speed and range improvements.
IEEE 802.11 ax is a type of WLAN in the IEEE 802.11 set of types of WLANs. It is designed to improve overall spectral efficiency especially in dense deployment scenarios. It is still in a very early stage of development, but is predicted to have a top speed of around 10 Gb/s, it works in 2.4 and/or 5 GHz, in addition to MIMO and MU-MIMO it introduces OFDMA technique to improve spectral efficiency and also higher order 1024 QAM modulation support for better throughputs. Though the nominal data rate is just 37% higher comparing with 802.11ac, the new amendment will allow achieving 4X increase of user throughput thanks to more efficient spectrum usage. It is due to be publicly released in 2019.
|Data rate (in Mb/s)|
|20 MHz channels||40 MHz channels||80 MHz channels||160 MHz channels|
|1600 ns GI||800 ns GI||1600 ns GI||800 ns GI||1600 ns GI||800 ns GI||1600 ns GI||800 ns GI|
Technical improvements in 802.11ax
The 802.11ax amendment will bring several key improvements over 802.11ac. 802.11ax addresses frequency bands between 1 GHz and 6 GHz. Therefore, unlike 802.11ac, 802.11ax will also operate in the unlicensed 2.4 GHz band. To meet the goal of supporting dense 802.11 deployments the following features have been approved.
|OFDMA||not available||Centrally controlled medium access with dynamic assignment of 26, 52, 106, 242, 484, or 996 tones per station. Each tone consist of a single subcarrier of 78.125 kHz bandwidth. Therefore, bandwidth occupied by a single OFDMA transmission is between 2.03125 MHz and ca. 80 MHz bandwidth.||OFDMA segregates the spectrum in time-frequency resource units (RUs). A central coordinating entity (the AP in 802.11ax) assigns RUs for reception or transmission to associated stations. Through the central scheduling of the RUs contention overhead can be avoided, which increases efficiency in scenarios of dense deployments.|
|Multi-user MIMO (MU-MIMO)||available in Downlinkdirection||Available in Downlink and Uplink direction||With Downlink MU MIMO a device may transmit concurrently to multiple receivers and with Uplink MU MIMO a device may simultaneously receive from multiple transmitters. Whereas OFDMA separates receivers to different RUs, with MU MIMO the devices are separated to different spatial streams. In 802.11ax, MU MIMO and OFDMA technologies can be used simultaneously. To enable uplink MU transmissions, the AP transmits a new control frame (Trigger) which contains scheduling information (RUs allocations for stations, modulation and coding scheme (MCS) that shall be used for each station). Furthermore, Trigger also provides synchronization for an uplink transmission, since the transmission starts SIFS after the end of Trigger.|
|Trigger-based Random Access||not available||Allows performing UL OFDMA transmissions by stations which are not allocated RUs directly.||In Trigger frame, the AP specifies scheduling information about subsequent UL MU transmission. However, several RUs can be assigned for random access. Stations which are not assigned RUs directly can perform transmissions within RUs assigned for random access. To reduce collision probability (i.e. situation when two or more stations select the same RU for transmission), the 802.11ax amendment specifies special OFDMA back-off procedure. Random access is favorable for transmitting buffer status reports when the AP has no information about pending UL traffic at a station.|
|not available||Coloring enables devices to differentiate transmissions in their own network from transmissions in neighboring networks.Adaptive Power and Sensitivity Thresholds allows dynamically adjusting transmit power and signal detection threshold to increase spatial reuse.||Without spatial reuse capabilities devices refuse transmitting concurrently to transmissions ongoing in other, neighboring networks. With coloring, a wireless transmission is marked at its very beginning helping surrounding devices to decide if a simultaneous use of the wireless medium is permissible or not. A station is allowed to consider the wireless medium as idle and start a new transmission even if the detected signal level from a neighboring network exceeds legacy signal detection threshold, provided that the transmit power for the new transmission is appropriately decreased.|
|NAV||Single NAV||Two NAVs||In dense deployment scenarios, NAV value set by a frame originated from one network may be easily reset by a frame originated from another network, which leads to misbehavior and collisions. To avoid this, each 802.11ax station will maintain two separate NAVs — one NAV is modified by frames originated from a network the station is associated with, the other NAV is modified by frames originated from overlapped networks.|
|Target Wake Time (TWT)||not available||TWT reduces power consumption and medium access contention.||TWT is a concept developed in 802.11ah. It allows devices to wake up at other periods than the beacon transmission period. Furthermore, the AP may group device to different TWT period thereby reducing the number of devices contending simultaneously for the wireless medium.|
|Dynamic fragmentation||With static fragmentation all fragments of a data packet are of equal size except for the last fragment. With dynamic fragmentation a device may fill available RUs of other opportunities to transmit up to the available maximum duration. Thus, dynamic fragmentation helps to reducing overhead.|
|Guard interval duration||0.4 µs or 0.8 µs||0.8 µs, 1.6 µs or 3.2 µs||Extended guard interval durations allow for better protection against signal delay spread as it occurs in outdoor environments.|
|Symbol duration||3.2 µs||3.2 µs, 6.4 µs, or 12.8 µs||Extended symbol durations allow for increased efficiency.|
802.11ax is currently still in draft.
Between 1 December 2016 and 8 January 2017 the IEEE 802.11 Working Group held a letter ballot on the first draft of 802.11ax. This ballot failed with only 58 % approval. Because of the large number of comments to be addressed, the TGax Chairman assumed that the approval of draft 2.0 of 802.11ax will be delayed to September 2017. Consequently, publication of the 802.11ax amendment is expected to delay until 2019.
As of August 2017, there are three major vendors who have put out silicon supporting 802.11ax. These are Quantenna with the QSR5G-AX and QSR10G-AX chipsets, Qualcomm with the QCA6290 chipset and IPQ8074 SoC and Broadcom with the BCM43684, BCM43694 and BCM4375 chips.
On October 17, 2016 Quantenna announced the first 802.11ax silicon, the QSR10G-AX. The chipset is compliant with Draft 1.0 and support eight 5 GHz streams and four 2.4 GHz streams. In January 2017 Quantenna added the QSR5G-AX to their portfolio with support for four streams in both bands. Both products are aimed at routers and access points.
Qualcomm announced their first 802.11ax silicon on February 13, 2017. The IPQ8074 is a complete SoC with four Cortex-A53 cores. There is support for eight 5 GHz streams and four 2.4 GHz streams. The QCA6290 chipset which supports two streams in both bands and aims at mobile devices.
Broadcom announced their 6th Generation of Wi-Fi products with 802.11ax support on August 15, 2017. The BCM43684 and BCM43694 are 4×4 MIMO chips with full 802.11ax support, while the BCM4375 provides 2 × 2 MIMO 802.11ax along with Bluetooth 5.0.
Other up-coming Fast WiFi standards: 802.11ay
Users should not confuse 802.11ax with 802.11ay, which will work in the 60GHz bands. The lower frequency bands 1-6GHz for 11ax will penetrate walls. 11ay will not.
What will 802.11ax be used for?
802.11ax is an upgrade for existing 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac networks, Many are enthusiastic about 802.1ax’s potential as a fixed point-to-point or point-to-multipoint outdoor backhaul technology, especially in light of scaled back fiber rollout plans by providers like Google and Verizon in the face of extraordinary costs associated with such implementations. Therefore 11ax will find applications outdoors as well as indoors.
Who is behind 802.11ax?
The IEEE task force leading the 11ax work includes representatives from major equipment and chipsets vendors.
In 2012 and 2013, IEEE 802.11 received various submissions in its Standing Committee (SC) Wireless Next Generation (WNG) looking at issues of IEEE 802.11ac and potential solutions for future WLANs. Immediately after the publication of IEEE 802.11ac in March 2013, the IEEE 802.11 Working Group (WG) established Study Group (SG) High Efficiency WLAN (HEW)
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