As the number of Wi-Fi devices in use increases, CSMA inefficiencies in legacy Wi-Fi can lead to degradation in per user throughput. One goal of 802.11ax is to increase the efficiency of the technology and achieve 4x improvement in the average user throughput.
With the popularity of smartphones and social networking applications, users often upload their own contents to share with their peers. In today’s Wi-Fi, if these users’ devices are connected to the same Access Point (AP), they have to contend for radio resources and transmit their contents sequentially one at a time. 802.11ax introduces uplink (UL) multi-user technologies. These allow multiple devices to simultaneously transmit their own data in the same radio frequency to the same Access Point. This has the obvious benefit of improving the UL capacity and reducing latency. At the same time, it also frees up air link resources for users to download data from the same Access Point (AP). The actual capacity gain from this feature in real networks will depend on the number of antennae on the Access Point and the mix of downlink and uplink data traffic. Qualcomm Research has built an over-the-air prototype with a 4-antenna AP that demonstrates 4x downlink (DL) user throughput improvement for a given traffic scenario by supporting 4 user devices to upload data simultaneously.
It is also possible in 802.11ax for the AP to schedule different users in different sub-carriers of the same channel. This is particularly desirable in scenarios with numerous small packet transmission, resulting in reduction in medium occupancy and lower latency.
The higher-order modulation (1024-QAM) and new numerology that will be introduced in 802.11ax help achieve over 1 Gbps throughput per spatial stream.
802.11ax is also considering spatial reuse techniques like Basic Service Set (BSS) color, to improve medium access inefficiencies.
The standardization of 802.11ax is in progress in IEEE. Draft 1.0 is expected to be completed in the second half of 2016 and the final specification is expected to be published in 2019.