The latest generation of Wi-Fi (called Wi-Fi 6) brings some significant performance improvements and is designed to address the limitations of the older generation. Although 802.11ax-certified chips provide a large number of routers and clients, Wi-Fi 6 has just begun to spread. It will become part of the IEEE formal specification in September 2020. This will usher in a wave of updated equipment, touting new wireless features, which will bring faster speeds and less congestion to next-generation networks.
Before going further, we must emphasize that 802.11ax (also known as “high-efficiency wireless”) and Wi-Fi 6 are the same thing, which is very important. But if you say it, Wi-Fi 6 is easier than 802.11ax.
This is a new naming standard established by the Wi-Fi Alliance. The previous generations are now called Wi-Fi 5 (802.11ac) and Wi-Fi 4 (802.11n). It is expected that this labeling convention will appear on the device as shown below.
Technically speaking, the single-user data rate of Wi-Fi 6 is 37% faster than 802.11ac, but more importantly, the updated specification will provide four times the throughput for each user in a crowded network environment, and has Higher power efficiency. It should extend the battery life of the device.
In order to achieve these improvements, 802.11ax has made various changes, including several multi-user technologies borrowed from the cellular industry, namely MU-MIMO and OFDMA. These technologies greatly increase the use of more simultaneous connections and spectrum throughput. Improve the capacity and performance of the network.
Home users who upgrade their hardware can look forward to these technological improvements, especially over time, as the number of devices per household increases—some estimates indicate that by 2022, there will be as many as 50 nodes per household .
Although Wi-Fi 6 is not designed to significantly increase download speeds, as the number of devices in the area increases, these new features will really come into play. It has a more nuanced approach and is expected to bring relocation benefits over time. This will ultimately lay the foundation for the expected number of nodes on the upcoming smart infrastructure (for example, IoT devices). In addition to solving the problem of overlapping coverage of a large number of devices and network deployments due to the introduction of the Internet of Things, Wi-Fi 6 can also meet the growing demand for multi-user data rates.
Overall, Wi-Fi 6 is built on 802.11ac. According to the original proposal, there will be more than 50 updates, but not all final features are included in the final specification.
The following are the main advantages of Wi-Fi 6:
- Higher total bandwidth per user for UHD and virtual reality streaming
Support more simultaneous data streams and increase throughput
More total spectrum (2.4GHz and 5GHz, the final frequency band is 1GHz and 6GHz)
The spectrum is divided into more channels to achieve more communication paths
Data packets contain more data, and the network can process different data streams at once
Improved performance within the maximum range of the access point (up to 4 times)
Better performance/robustness in outdoor and multipath (cluttered) environments
Ability to divert wireless traffic from cellular networks with poor reception
802.11n and 802.11ac and 802.11ax
802.11ac (that is, WiFi 5) was standardized in 2013. Although the specification is suitable for today’s typical home use to a large extent, it only uses the frequency band of the 5GHz spectrum and lacks the level of multi-user technology, which will support more and more devices to connect at the same time.
As a reference for the upcoming changes in Wi-Fi 6, the following is the extension of 802.11ac (Wi-Fi 5) over 802.11n (Wi-Fi 4):
- A wider channel (80MHz or 160MHz, while the maximum in the 5GHz band is 40MHz)
Eight spatial streams (spatial streams) instead of four
256-QAM and 64-QAM modulation (each QAM symbol transmits more bits)
Multi-user MIMO (MU-MIMO) on 802.11ac Wave 2 can achieve four downlink connections at a time instead of only one on single-user MIMO (uplink is still 1×1)
The specification is backward compatible with previous standards, combining 2.4GHz and 5GHz, and finally expanding the spectrum to include 1GHz and 6GHz bands when available.
Perhaps more notable than including these additional spectrum is the technology that puts this bandwidth into use. With more available spectrum, Wi-Fi 6 can divide the bandwidth into narrower (more) sub-channels, creating more communication channels for clients and access points, and supporting others on any given network equipment. In the older 802.11n, due to too much overlap, you basically can only use 3 independent channels at the same time. Since everyone’s routers are competing with each other, this makes crowded places such as apartments a mess. 802.11ac adds extra space in the 5GHz band, but 802.11ax does a better job of dealing with this problem.
Another area to consider is the performance of multiple devices on a single network. This is the so-called multiple input multiple output, which allows a single device to communicate through multiple channels at once. It’s basically like connecting multiple wireless adapters to the same network. The extension at the access point is called MU-MIMO or multi-user MIMO. As the name suggests, it allows the access point to connect to multiple users at once via MIMO.
Although MU-MIMO can enable Wi-Fi 5 to provide services to four downstream users at a time (compared to the single-user MIMO on Wi-Fi 4), this function is not necessary. Only added to new 802.11ac devices. On paper, 802.11ax can increase the number of uplink and downlink users to eight, and it is possible to deliver four simultaneous streams to a single client.
However, uplink MU-MIMO is unlikely to be used. Currently, almost no device can benefit from the four spatial streams, because most existing MU-MIMO-equipped smartphones and laptops only have 2×2:2 or 3×3:3 MIMO radios, so there is almost no Wi-Fi 6 support Eight spatial streams.
This digital format (AxB:C) is used to demonstrate the largest transmit antenna (A), the largest receive antenna (B), and the largest spatial data stream (C) supported by the MIMO radio. Although Wi-Fi devices must support MU-MIMO to directly benefit from the technology, hardware without MU-MIMO chips should indirectly benefit from the additional broadcast time available on MU-MIMO-enabled access points.
To help you visualize these technologies, the combination of MU-MIMO and OFDMA can be equivalent to having many employees and multiple lines, and each employee can serve multiple customers at once, rather than a single employee serving a single customer. In addition, 802.11ax can more clearly notify clients when routers are available, rather than let them compete for access.
Although the overall data rate and channel width of Wi-Fi 6 are similar to Wi-Fi 5, dozens of technologies have been implemented in accordance with the updated specifications. These technologies will significantly improve the efficiency and throughput of future Wi-Fi networks. It may transmit devices at a speed of several gigabits per second on a single channel for dozens of Wi-Fi network services. We will now discuss some of them.
OFDMA: Wi-Fi 6 also introduced support for uplink and downlink “Orthogonal Frequency Division Multiple Access” (OFDMA), which is a modulation scheme equivalent to the multi-user version of OFDM (802.11ac/n specification). OFDMA reduces delay, increases capacity, and improves efficiency by allowing up to 30 users to share a channel at a time. Do not confuse this with Orthogonal Frequency Division Multiplexing (OFDM).
OFDMA allows better allocation of resource units in a given bandwidth. Integrated in Wi-Fi 6, so more clients (up to 30) can share the same channel instead of waiting, and can also improve efficiency by combining different traffic types. OFDMA is compared to the multi-user version of OFDM.
For simplicity, OFDM divides the channel into several subcarriers, allowing multiple parallel data streams. However, each user must use its complete subcarrier. On the other hand, OFDMA further subdivides it into resource units that can be allocated individually. This fine-grained allocation is the key to OFDMA’s performance advantages.
1024-QAM：
The next major performance improvement is the jump from 256-QAM to 1024-QAM. When a wireless device transmits a message, it must send out an analog signal because it cannot directly transmit binary data. The analog signal has two parts, called amplitude (the strength of the signal) and quadrature (how much the signal is offset from the reference point). By controlling quadrature and amplitude, we can effectively transmit digital data through analog signals.
The 256-QAM system used in 802.11ac divides amplitude and quadrature into 16 predefined levels. This provides a total of 256 (16 * 16) possible transfer values, and each transfer allows up to 8 bits (2^8 = 256). Since the introduction of 802.11ac, the transmitter and receiver technology has advanced significantly, so we can now assign more precise values to transmissions. 802.11ax can divide the orthogonality and amplitude of the transmission into 16 possible values instead of dividing it into up to 32 levels. This provides us with 1024 (32 * 32) possible transmission values, with a maximum of 10 bits per transmission.
Of course, as we pack more and more data into the same amount of resources, our sensitivity and accuracy must also increase. Small errors in the reception of 256-QAM signals may not cause problems, but since 1024-QAM packs symbols closer together, the same error may cause incorrect values to be decoded. The device is smart enough to know that if many transmissions are decoded incorrectly, it should be reduced to a lower scheme.
Using an 80MHz channel, 1024-QAM can generate a theoretical single-stream data rate of 600Mb/s, which is 39% higher than the theoretical 433Mb/s single-stream data rate of Wi-Fi 5.
Longer OFDM symbols: Increase the transmission time of OFDM symbols from 3.2us on Wi-Fi 5 to 12.8us on Wi-Fi 6, and support a longer cyclic prefix (CP) for each symbol.
The cyclic prefix (CP) adds a part of the end of the OFDM symbol to the front of the payload to provide a guard interval to prevent inter-symbol interference and improve robustness, because this part can be used when necessary. This number can be adjusted according to overhead requirements (a longer CP repeats more data and takes up more space in the symbol, resulting in a lower data rate).
Spatial Frequency Multiplexing/OBSS (BSS Coloring): If multiple access points are operating on the same channel, they can transmit data with a unique “color” identifier so that they can communicate through the wireless medium at the same time. No need to wait for colors to enable them to distinguish each other’s data.
Beamforming: This exists on Wi-Fi 5, although the standard supports four antennas, while Wi-Fi 6 increases it to eight. Beamforming increases the data rate and extends the range by directing the signal to a specific client rather than in each direction at the same time. This helps MU-MIMO, which is not suitable for fast-moving devices. Beamforming can be performed on Wi-Fi 4 devices, but with the realization of MU-MIMO on Wi-Fi 5 Wave 2, beamforming becomes necessary. In a new direction.
TWT (Target Wake-up Time): Wake-up time scheduling, rather than contention-based access. The router can tell the client when to fall asleep and when to wake up, which is expected to greatly extend battery life because the device will know when to listen to the channel.
Uplink resource scheduler: Similarly, Wi-Fi 6 will not rush to upload data like on older wireless networks. Instead, it will schedule the uplink to minimize conflicts and achieve better resource management. Everyone has their own speaking space, so no one needs to shout or talk to others.
Trigger-based random access: You can also reduce data conflicts/conflicts by specifying the length of the uplink window in other attributes, which can improve resource allocation and increase efficiency.
TWO NAVs (Network Assignment Vector): When a wireless station is transmitting, it will announce the duration required for completion so that other stations can set their NAV to avoid conflicts when accessing the wireless medium. Wi-Fi 6 introduced two types of NAV: one for the network to which the site belongs, and the other for the adjacent network. This will also reduce energy consumption by minimizing the need for carrier sensing.
Improved outdoor operation: Some of these features will bring better outdoor performance, including new packet formats, longer guard intervals and modes to improve redundancy and error recovery.
Wi-Fi 6E: Extend Wi-Fi 6 to include 6GHz
Wi-Fi 6E is the name of a new extension to the existing Wi-Fi 6 standard, indicating that it can support the brand new 6 GHz frequency. This will increase spectrum, higher throughput and lower latency.
Industry leaders such as Qualcomm have determined that proper service quality on future networks will require spectrum beyond what 2.4GHz or 5GHz can provide. For a long time, the 2.4GHz band has been saturated by common electronic devices such as microwaves. Another option is 5GHz, its spectrum is not enough for wider bandwidth channels (such as 80MHz or 160MHz), and some parts of 5GHz are restricted to limit its use.
At the beginning of 2020, the Federal Communications Commission (FCC) formally approved Wi-Fi to extend its coverage to the new radio spectrum in the US 6 GHz band. Specifically, the new Wi-Fi 6E standard will have access to the 1.2 GHz or 1200 MHz radio spectrum, ranging from 5.9 GHz to 7.1 GHz (and merge all 6 GHz frequencies in between, and therefore also include a 6 GHz reference).
Standard Wi-Fi faces the problem of spectrum shortage, because if the number of devices used worldwide continues to increase and the increase of 6GHz will help alleviate this problem. Once allowed, 6GHz will promote the continued growth of Wi-Fi, as well as other advantages, such as wider channel size and less interference from traditional Wi-Fi 4 (802.11n) and Wi-Fi 5 devices. Analysts predict that approval will trigger the rapid adoption of the frequency band by equipment manufacturers.
From the perspective of the new spectrum, even the widest connection of millimeter wave 5G (the fastest existing 5G connection) is limited to 800 MHz. In other words, the frequency that the new Wi-Fi connection can access is almost 1.5 times that of the fastest 5G connection.
In theory, this means that the connection speed of Wi-Fi 6E may be significantly faster than the highest speed 5G can provide. In addition, due to the basic laws of physics and signal propagation, the coverage of Wi-Fi 6E can actually be wider than that of millimeter wave 5G.
The influence of Wi-Fi 6E will really come into play in highly congested areas. Routers will have wider channels and can accommodate more devices at higher throughput rates.
Wi-Fi 6 or 802.11ax is just one of many upcoming wireless standards developed to meet the various network requirements that different types of devices will meet. 802.11ad/ay will bring multi-gigabit speeds through the use of millimeter wave frequencies. On the contrary, 802.11ah is designed for ultra-low power consumption, which may lead to several years of battery life.
Summary: The aerial view of Wi-Fi
As the next WLAN standard to succeed 802.11n and 802.11ac, 802.11ax or Wi-Fi 6 will bring significant improvements in network efficiency and capacity in densely populated centers, and peak data rates will be moderately increased throughout the data center Will be better maintained. Add equipment at once.
As Qualcomm likes to say, “The question is not how fast Wi-Fi can go, but whether the Wi-Fi network has enough capacity to meet the growing demand for many different connected devices and services.”
Currently there are not many Wi-Fi 6 clients, so it will take time to adopt. Until more devices use the standard, you can really feel the improvement of this generation. As usual, Wi-Fi 6 is backward compatible, but older devices will not be able to take advantage of the newer features.
Considering Wi-Fi 6 from a broader perspective, as the demand for user data continues to increase, the increase in multi-user support, especially the increase in simultaneous uplink connections, has arrived. These data will be collected from IoT devices and used for machine learning, promoting the development of artificial intelligence, the future of the entire technology, and the evolving digital economy.
