Wave 2 802.11ac routers will arrive sometime in 2015. These devices will also operate on the less-crowded 5GHz frequency band, but they'll take advantage of several optional elements of the 802.11ac standard: First, they'll support a feature called MU-MIMO (multi-user multiple input/multiple output), which allows them to transmit multiple spatial streams to multiple clients simultaneously.
Second, they'll bond multiple channels on the 5GHz frequency band to create a single channel that provides 160MHz of bandwidth (Wave 1 802.11ac routers can also bond 5GHz channels, but the bonded channel is only 80MHz wide). Third, where 802.11n and Wave 1 802.11ac routers support a maximum of three spatial streams, Wave 2 802.11ac routers will potentially support up to eight spatial streams.
Using some combination of wider channels or additional spatial streams (there isn't enough available bandwidth to do both), improved beamforming, and other techniques, Wave 2 802.11ac routers will deliver maximum physical link rates in the range of 7- to 10Gbps. Quantenna Communications announced its first Wave 2 802.11ac chipset last April.
The next new Wi-Fi: IEEE 802.11ax
In a recent briefing, the Wi-Fi Alliance's VP of Technology Greg Ennis said the IEEE anticipates the 802.11ac standard will be succeeded by 802.11ax. While the standards body doesn't expect to ratify it before March 2019, products based on a draft of the standard could reach the market as early as 2016 — just as we saw draft-802.11n and draft-802.11ac products before those standards were officially ratified.
One of the top objectives of 802.11ax, according to Ennis, is to quadruple wireless speed to individual network clients — not just to increase the speed of the network overall. The Chinese manufacturer Huawei, which has engineers in the IEEE 802.11ax working group, has already reported Wi-Fi connection speeds up to 10.53Gbps on the 5GHz frequency band.
Ennis said the 802.11ax standard will improve Wi-Fi performance in environments with high numbers of users, such as hotspots in public venues. This will be accomplished by using the available spectrum more efficiently, doing a better job of managing interference, and making enhancements to underlying protocols such as medium access control (MAC) data communication. This should make public Wi-Fi hotspots faster and more reliable.
The 802.11ax standard will also use orthogonal frequency-division multiple access (OFDMA) to boost the amount of data the router can transmit. Like OFDM (orthogonal frequency-division multiplexing), OFDMA encodes data on multiple sub-carrier frequencies — essentially packing more data into the same amount of air space. The "multiple access" in OFDMA describes a means of assigning subsets of those sub-carrier frequencies to individual users.
The complementary standards
While one segment of the IEEE works to define the successor to 802.11ac, other factions work on two complementary wireless-networking standards that address other needs. The IEEE 802.11ad standard uses unlicensed spectrum in the 60GHz band to build fast short-range wireless networks with peak transmission rates of around 7Gbps.
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