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IEEE 802.11ax is a type of WLAN in the IEEE 802.11 set of types of WLANs. IEEE 802.11ax is designed to operate in the already existing 2.4 GHz and 5 GHz spectrums. In addition to utilizing MIMO and MU-MIMO, the new amendment introduces OFDMA to improve overall spectral efficiency, and higher order 1024 QAM modulation support for increased throughput. Though the nominal data rate is just 37% higher than IEEE 802.11ac, the new amendment is expected to achieve a 4x increase to user throughput—due to more efficient spectrum utilization.
|Data rate (in Mb/s)[b]|
|20 MHz channels||40 MHz channels||80 MHz channels||160 MHz channels|
|1600 ns GI[c]||800 ns GI||1600 ns GI||800 ns GI||1600 ns GI||800 ns GI||1600 ns GI||800 ns GI|
- MCS 9 is not applicable to all channel width/spatial stream combinations.
- A second stream doubles the theoretical data rate, a third one triples it, etc.
- GI stands for the guard interval.
The 802.11ax amendment will bring several key improvements over 802.11ac. 802.11ax addresses frequency bands between 1 GHz and 5 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 Downlink direction||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.|
|Spatial frequency reuse||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.|
On October 17, 2016, Quantenna announced the first 802.11ax silicon, the QSR10G-AX. The chipset is compliant with Draft 1.0 and supports 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. On February 13, 2017, Qualcomm announced their first 802.11ax silicon.[third-party source needed] 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. On August 15, 2017, Broadcom announced their 6th Generation of Wi-Fi products with 802.11ax support.[third-party source needed] 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. On December 11th, 2017, Marvell announced 802.11ax chipsets consisting of 88W9068, 88W9064 and 88W9064S. On February 21, 2018, Qualcomm announced the WCN3998, a 2x2 802.11ax chipset for smartphones and mobile devices. As of April 2018, Intel is working on a 802.11ax chipset for mobile devices, the Wireless-AX 22560 with Harrison Peak codename.
On August 30, 2017, Asus announced the first 802.11ax router.[third-party source needed] The RT-AX88U uses Broadcom silicon, has 4×4 MIMO in both bands and achieves a maximum of 1148 Mb/s on 2.4 GHz and 4804 Mb/s on 5 GHz. On September 12, 2017, Huawei announced their first 802.11ax access point. The AP7060DN uses 8×8 MIMO and is based on Qualcomm hardware.[third-party source needed] On January 25, 2018, Aerohive Networks announced the first family of 802.11ax access points. The AP630, AP650, and AP650X are based on Broadcom chipsets. These are expected to start shipping mid 2018.[third-party source needed]
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