For years, all we have focused on is getting people faster Wi-Fi connectivity. But as Chuck Lukaszewski, Aruba VP of wireless strategy, pointed out on Aruba Unplugged Episode 6: What You Need to Know About Wi-Fi 6,our wireless networks are changing and we are seeing more and more devices per cell.
Previous standards had a focus on speeds to get devices information as fast as possible, but they were lacking efficiency. A single device performing poorly could impact the network for all other devices within the cell. Now that we are faced with the wave of IoT and mobile devices continually growing,there is a need for devices to be able to communicate without impacting others.
Wi-Fi 6 answers several questions for us: How do we make the best use of the limited airtime we already have? How can we offset some of the efficiencies with performance to client battery life? How can we increase the throughput available to our devices?
How do we make the best use of the limited airtime we already have?
To make the best use of the spectrum, the IEEE adopted a technology that has already been tested on wireless networks: Orthogonal Frequency Divisional Multiple Access (OFDMA). This technology has been used in multiple standards, including cellular LTE and WiMAX. By bringing OFDMA into Wi-Fi 6, we can shrink the size of the subcarrier spacing from 312.5kHz in 802.11ac to 78.125kHz in 802.11ax. This will also allow us to divide the frequency space into resource units (RUs) to send data to multiple clients at the same time—up to 37 clients on an 80MHz channel.
While we are focusing on the downstream in the first release of Wi-Fi 6, the same will be true on upstream OFDMA in 802.11ax Wave 2, where multiple clients will be able to transmit data to the AP at the same time. The major benefit that stands out to me is allowing the AP to assign more transmit opportunities to voice and video applications that are very latency sensitive at the same time other devices are transmitting data.
How can we offset some of the efficiencies with performance to client battery life?
Earlier we mentioned there are more and more mobile devices joining our networks. Imagine if you have a warehouse full of barcode scanners that have to wake up on a set DTIM interval. The battery life of these devices suffers as a result of waking-up and listening to the beacons, even if there isn’t any relevant data destined to them.
802.11ax Target Wake Time (TWT), first introduced in 802.11ah, offers two different flavors: Individual and Broadcast. Individual TWT brings the ability for the client and the AP to negotiate the schedule for when the client is to wake and check in with the AP for any buffered packets. This delay could be minutes, hours or even days.
Individual TWT is negotiated per device, allowing more freedom for devices to sleep their own schedules and not wake as part of the group. Broadcast TWT is used for devices that want to connect to multicast streams; there is no negotiation and the AP controls the schedule. Devices will wake on a set schedule, receive their stream and go back to sleep.
How can we increase the throughput available to our devices?
The main goal of Wi-Fi 6 isn’t necessarily to see significant speed increases, but increasing the speed at which data is transmitted to enable you to utilize the spectrum efficiently. Wi-Fi 6 introduces a higher modulation of 1024-QAM with up to eight spatial streams on 160 MHz wide channels. All combined, we can see a theoretical limit of 9,607.8Mbps of throughput, over 3 Gbps faster than the theoretical limit of Wi-Fi 5. While we never saw 8-spatial-stream (8SS) devices in Wi-Fi 5, we have already seen the release of a Wi-Fi 6 8SS AP from Aruba, the AP-550.
For a more in-depth look at Wi-Fi 6, check out the 802.11ax white paper published by Aruba.
Blog post author: Richard McIntosh, HPE Blog Post Contributor
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