Wi-Fi 6

High-efficiency wireless for high-density environments

The old credo of “higher, farther, faster!” no longer applies to the sixth generation. 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.

Inquiry

What is Wi-Fi 6?

Wi-Fi 6 offers the advantage of lower latency per WLAN client compared to older standards. 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 from the Wi-Fi Alliance.

Applications

Scenarios with large numbers of users

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.

More and more IoT devices

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 above 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.

What has changed over the previous standard Wi-Fi 5

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.

In the following we will outline some of the technologies that are used in Wi-Fi 6.

8x8 MIMO

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.

Wi-Fi 5, 80 MHz, QAM-256 with up to 4x4 MIMO
1x1	2x2	3x3	4x4
433.3 Mbps	866.7 Mbps	1300 Mbps	1733.3 Mbps

Tab. 1: Possible download speeds for different transmitter-receiver pairs with Wi-Fi 5

Wi-Fi 6, 80 MHz, QAM-1024 with up to 8x8 MIMO
1x1	2x2	3x3	4x4	8x8
600 Mbps	1.2 Gbps	1.8 Gbps	2.4 Gbps	4.8 Gbps

Tab. 2: Possible download speeds for different transmitter-receiver pairs with Wi-Fi 6

**Fig. 1: MU-MIMO (Down- & Uplink)**

MU-MIMO for downloads and uploads

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.

Explanation

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.

Transmitter x receiver = number of transmitting x receiving antennas
8x8 MIMO = 8 transmitting x receiving antennas
8 streams	8 1x1 smartphones
8 streams	4 2x2 tablets or 2x2 notebooks
8 streams	4 1x1 smartphones + 1 2x2 tablet + 1 2x2 notebook

Tab. 3: Assignment of streams between transmitter and receiver(s)

Orthogonal Frequency Division Multiple Access (OFDMA)

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.

**Fig. 2: Comparison of OFDM vs. OFDMA technology**

Quadrature Amplitude Modulation (QAM)

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.

**Fig. 3: QAM-256 compared to QAM-1024**

Modulation	Bit per symbol	Symbol rate
QAM-16	4	4 bit / rate
QAM-32	5	5 bit / rate
QAM-64	6	6 bit / rate
QAM-256	8	8 bit / rate
QAM-1024	10	10 bit / rate

Tab. 4: Transmitted bits per symbol at different QAM levels

Longer battery life thanks to Target Wake Time (TWT)

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.

Basic Service Set Coloring (BSS Coloring) and Spatial Reuse

The theory:
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.

**Fig. 4: without and with BSS Coloring and Spatial Re-Use**

Here is an example from everyday life:

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.

Outlook

New frequencies in sight

There is little space left in the Wi-Fi spectrum. One way forward would be to end this shortage of channels. In the USA, the authorities recently decided to release the 6-GHz band between 5925 and 7125 MHz for license-free usage. This is an extra 1,200 MHz available to Wi-Fi. In the EU, too, discussions about the 6-GHz band are ongoing and the European Commission is considering the release of the band for license-free usage. However, only the 5925 to 6425 MHz range is to be made available, which would at least give radio technologies such as Wi-Fi 6 a 500 MHz larger frequency range, i.e. 1038.5 MHz instead of the current 538.5 MHz. Of course this will require new access points and clients.

The LANCOM Wi-Fi 6 product range

Our first Wi-Fi 6 access point

This fall LANCOM will launch its first Wi-Fi 6 product.

A few key facts:

Dual concurrent Wi-Fi – parallel operation at 2.4 GHz and 5 GHz with Wi-Fi 6 for up to 3600 Mbps (combined transmission rate)
4x4 MU-MIMO with internal antennas
1x 2.5-Gigabit Ethernet (PoE port, IEEE 802.3at for up to 30 Watt PoE)
1x Gigabit Ethernet
Bluetooth Low Energy radio module (version 5.0) for innovative beaconing applications
USB 3.0 port for connecting various IoT wireless systems
Operates stand-alone with the aid of the intuitive WEBconfig, or via the LANCOM Management Cloud

Further products will follow

The device is part of a new Wi-Fi 6 product range, which is soon to grow yet further with an Access Point equipped with external antennas. Further models are also in planning, e.g. for applications based on Wi-Fi 6 and 8x8 MU-MIMO for extremely high user densities.

Whitepaper

White Paper: The new Wi-Fi standard Wi-Fi 6