Wi-Fi 6 offers the advantage of lower latency per WLAN client compared to older standards. When it comes to Wi-Fi, it is not so much about being faster: Now it is more about increasing the average throughput per Wi-Fi client, especially in high-density environments. Wi-Fi 6 is synonymous with IEEE 802.11ax and Wi-Fi 5 with IEEE 802.11ac. This nomenclature was introduced in 2018 starting with Wi-Fi 4, which stands for the IEEE 802.11n standard, by the Wi-Fi Alliance.
In the LANCOM White Paper 2x2 Wi-Fi 6 vs. 3x3 Wi-Fi 5 you can read about the advantages of a wireless LAN infrastructure based on 2x2 MIMO Wi-Fi 6 access points as opposed to an installation with 3x3 MIMO access points with Wi-Fi 5. This document can help you choose the right WLAN infrastructure according to your needs.
The weaknesses of previous standards were particularly evident in high-density environments with large numbers of Wi-Fi clients. Multiple clients trying to transmit at the same time will cause data transmissions to collide, so the aim is to reduce this. By making more efficient use of the available bandwidths and channels, Wi-Fi 6 brings more stability and reliability to intensively used wireless LANs. The advantage of Wi-Fi 6 over former standards is a reduction in latency time for each Wi-Fi client. The available bandwidths are allocated to each client much more efficiently.
The future will see increasing numbers of IoT devices coming into play, so the available bandwidths need to be managed and allocated even more efficiently. The OFDMA technology described below and the available subcarriers will make a significant contribution here. In environments with a very high density of IoT devices, such as in smart cities, high throughput and low latency have an important role to play. While the data generated by IoT sensors must be forwarded quickly, bandwidth-hungry applications should not be excluded or significantly slowed.
The progress from Wi-Fi 5 to Wi-Fi 6 results from the close interaction of some known and some new features:
- Multi-User MIMO (MU-MIMO) delivers more efficiency with large data packets now for uploads as well as downloads. Perfect for 4K video conferencing.
- OFDMA offers the parallel processing of multiple small data packets in a single stream. With subcarriers as narrow as 2 MHz, the available radio channels are utilized very efficiently to relieve the already crowded spectrum.
- QAM-1024 with Wi-Fi 6 provides 25 percent more data throughput than QAM-256 with Wi-Fi 5 due to a higher density modulation per data packet.
- Target Wake Time (TWT) extends the battery life of Wi-Fi 6 clients through intelligent wake-up mechanisms.
- Basic Service Set (BSS) Coloring maximizes network performance by reducing interference where client density is high.
Access points with MIMO technology support several independent data links, called spatial streams, for transporting data packets between the transmitter and the receiver. Depending on the number of antennas, an access point can send two, four, or even eight spatial streams at once. Wave 2 of the Wi-Fi 5 standard allowed up to four simultaneous data streams. Wi-Fi 6 now supports up to eight of these widened fast lanes.
Wave 2 of the wireless standard Wi-Fi 5 introduced the multi-user MIMO principle (MU-MIMO): By distributing the various spatial streams between several different clients at the same time, rather than serving them one after the other, the efficiency in Wi-Fi has been massively increased—but only for the downlink.
With Wi-Fi 6, MU-MIMO is now available in both directions. This is especially useful in environments with large numbers of Wi-Fi users and bandwidth-hungry real-time applications, as it also improves latency and throughput.
With MU-MIMO, the streams can be distributed to multiple clients. For example, an access point with 4x4 MIMO can divide its four spatial streams in parallel between a 2x2 MIMO client and two further 1x1 MIMO clients (such as a notebook or smartphone). This makes the most efficient use of all available spatial streams.
OFDMA offers real advantages for Wi-Fi clients with smaller data packets, e.g. IoT devices. Wi-Fi 5 came with Orthogonal Frequency Division Multiplexing (OFDM) as a method for channel management: During data transmission, the entire frequency range of a Wi-Fi channel is occupied per time interval. The introduction of OFDMA in Wi-Fi 6 brought subcarriers as narrow as 2 MHz, meaning that packets that only contain small amounts of data do not block the entire channel. Several subcarriers share a 20-, 40- or even 80-MHz channel, although if necessary they can be bundled and operated together. This allows Wi-Fi channels to be utilized far more effectively. It's comparable to carpooling: Large numbers of cars with a single occupant will cause heavy traffic, while fewer, multi-occupant cars can travel faster.
QAM increases data throughput by increasing the information density during transmission. The following applies: The higher the QAM level, the higher the data throughput. Compared to QAM-256 (8 bits / symbol) with Wi-Fi 5, Wi-Fi 6 introduces QAM-1024 (10 bits / symbol), delivering 25% more throughput than the previous standard.
BSS Coloring with Spatial Re-Use is a mechanism that maximizes network performance while reducing the interference between Wi-Fi devices. Wireless networks offer the access points a limited number of channels. If several neighboring access points use the same channel, they will inevitably interfere with one another. In previous Wi-Fi infrastructures, one device could transmit while all the other Wi-Fi devices on the channel had to wait their turn, even if they were far enough away to allow a parallel data transmission. With Wi-Fi 6, wireless devices are learning to communicate with each other more transparently. This is done with a pseudo-coloring of each SSID. Wi-Fi 6 devices can distinguish these colors, detect “different colored” radios on the same channel, and stop interfering with them.
This technology can be compared with the situation in a restaurant with different groups sitting at different tables. The group at table A is not interested in the conversations of the adjacent table B, so that the people at the next table can talk at a certain volume without the table group A feeling disturbed. Only when a certain threshold/volume is exceeded do the two tables have to discuss their compliance with this threshold; otherwise, one of the groups would have to move to another room.
Before Wi-Fi 5 arrived, smartphones, tablets and notebooks had to be ready to receive all the time. If not, arriving data packets would be missed, which was at the expense of the battery charge. With TWT (target wake time), Wi-Fi 6 cuts down on power wastage on the client side, as the access point and client now negotiate exactly when the receiver should wake up to receive the traffic intended for it. For many a smartphone, this will mean less time tied to the charger.
With the numbers of end devices growing steadily and the increasing density of IoT devices, the load on the available Wi-Fi frequencies has made communication hardly possible without collisions. For this reason and for almost 15 years of no changes within the spectrum usages, the Wi-Fi industry actively requested the National Regulatory Agencies for new frequencies. The Wi-Fi Alliance generally extends Wi-Fi 6 by the 6-GHz band, calling it “Wi-Fi 6E”. A new era for wireless LAN has begun!
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