1. Introduction
Wi-Fi, a widely used wireless technology, undergoes continual advancements to meet evolving needs like high data speeds, real-time communication, dense network environments, and enhanced resource and energy efficiency. The IEEE 802.11ax standard, commonly known as Wi-Fi 6, represents a significant step forward, targeting data rates nearing 10 Gbps, reduced energy consumption, and enhanced reliability.
In this article, we aim to deliver a thorough introduction to Wi-Fi 6, examining its features to understand how it enhances network performance in comparison to preceding Wi-Fi standards. Additionally, we will explore the open challenges associated with this advanced technology.
2. Overview of Wi-Fi and Wi-Fi 6
The IEEE 802.11 standard (commonly known as Wi-Fi or Wi-Fi 0) specifically addresses the Physical (PHY) and Medium Access Control (MAC) layers. It is well-suited for applications demanding mobile connectivity and high-speed internet access, finding predominant use in both enterprise and home networks. The widespread adoption of Wi-Fi is reflected in the projected increase in public Wi-Fi hotspots, estimated to reach 628 million in 2023, as numerous infrastructures rely on the versatility of Wi-Fi technology.
The below table shows the major amendments that follow the first IEEE 802.11 standard introduced in 1997, including 802.11b, 802.11a, 802.11g, 802.11n, 802.11ac, 802.11ax, and 802.11be. They are also denoted as Wi-Fi 1 to Wi-Fi 7:
Amendment
Year released
Target
IEEE 802.11b
1999
Wi-Fi 1
IEEE 802.11a
1999
Wi-Fi 2
IEEE 802.11g
2003
Wi-Fi 3
IEEE 802.11e
2005
QoS enhancements
IEEE 802.11n
2009
Wi-Fi 4
IEEE 802.11ac
2013
Wi-Fi 5
IEEE 802.11ah
2017
Low-power WLAN, extended range
IEEE 802.11ax
2021
Wi-Fi 6
IEEE 802.11be
2021
Wi-Fi 7
The widely used Wi-Fi standard, IEEE 802.11ac (Wi-Fi 5), falls short in meeting the requirements for real-time, high-reliability demands posed by advanced multimedia applications and the energy efficiency needed for Internet of Things (IoT) networks. Its limitations include an inability to effectively support both a substantial number of users with high Quality of Service (QoS) and efficient power management, making it less than optimal for certain applications.
3. Innovations in Wi-Fi 6
The below table summarizes the novelties introduced by Wi-Fi 6:
Features
Benefits
Multi-User OFDMA
Higher throughput
Overhead reduction
High spectral efficiency
Longer OFDM symbol
Higher efficiency for indoors
Robustness for outdoors
Spatial Reuse (SR)
Spectral efficiency
Increased capacity
Target Wake Time (TWT)
Higher throughput
Reliability
Lower latency
Lesser power consumption
Reduced jitter
Multi-User MIMO
Up to 8x/2x capacity increase in up/downlink
1024-QAM
25% higher data rate
3.1. Orthogonal Frequency Division Multiple Access (OFDMA)
The use of Orthogonal Frequency Division Multiplexing (OFDM) involves spreading transmissions across multiple subcarriers, necessitating the utilization of the entire spectrum. In dense network scenarios, where numerous stations contend for medium access, there is an elevated risk of collisions, leading to decreased throughput.
Wi-Fi 6 addresses this challenge by incorporating Orthogonal Frequency Division Multiple Access (OFDMA), a technology that enhances efficiency in managing the shared medium and helps mitigate collision-related throughput reductions.
By employing OFDMA, a transmission in Wi-Fi 6 utilizes specific segments of the spectrum, enabling multiple transmissions to occur simultaneously. This targeted spectrum allocation significantly diminishes contention and overhead on the Medium Access Control (MAC) layer.
As a result, there is a notable reduction in latency, and the throughput in dense networks is improved due to the more efficient use of available resources.
While Long Term Evolution (LTE) networks have previously utilized OFDMA for downlink multi-user transmission, Wi-Fi 6 takes a step further by supporting both uplink and downlink transmissions in multi-user (MU) mode.
It’s important to note that Wi-Fi 6 hardware also maintains backward compatibility with the 802.11a/g/n/ac standards by supporting OFDM. This ensures that Wi-Fi 6 devices can seamlessly coexist with and communicate with devices using older Wi-Fi standards.
The below figure illustrates the configuration of subcarrier spacing and OFDM symbol duration in Wi-Fi 6:
3.2. Spatial Reuse (SR)
In Wi-Fi technology, there are a limited number of frequency channels available for use by neighboring Basic Service Sets (BSSs). When multiple access points are in close proximity, their BSSs overlap. This overlap poses a challenge, as a transmitting node not only interferes with other transmissions within its own BSS but also affects transmissions in other BSSs sharing the same channel, making effective frequency reuse challenging.
Wi-Fi 6 addresses this issue by incorporating the BSS coloring concept from IEEE 802.11ah. This involves indicating the BSS in the packet header with a specific color. Nodes can leverage this information to monitor transmissions from other BSSs. With this knowledge, a node can initiate a transmission if it anticipates that it won’t collide with ongoing transmissions in a different BSS, thereby improving the efficiency of frequency reuse.
3.3. Target Wake Time (TWT)
The IEEE 802.11 standard incorporates the Power-Saving Mode (PSM) to optimize the battery lifespan of Wi-Fi stations. However, a drawback of PSM is that stations with pending traffic to send or receive tend to contend immediately after receiving a beacon, leading to traffic peaks and collisions. Additionally, a station remains active until all its packets are either received or transmitted, resulting in extended active times for PSM devices, even when they have minimal data to exchange.
To address these issues, Wi-Fi 6 builds upon and extends Target Wake Time (TWT), a feature initially introduced in IEEE 802.11ah. TWT allows the scheduling of wake times for stations in advance, ensuring they do not overlap. This strategic scheduling minimizes the active times of stations, maximizing their sleep durations and significantly reducing overall power consumption. As a result, Wi-Fi 6 effectively mitigates the problems associated with PSM, enhancing the energy efficiency of devices.
3.4. Multi-User MIMO (MU MIMO)
Wi-Fi 6 introduces both downlink and uplink MU MIMO (Multiple-Input Multiple-Output). The concurrent use of OFDMA and MU MIMO is also a viable option. In downlink MU MIMO, an access point has the capability to transmit data simultaneously to multiple stations.
This new standard enhances Wi-Fi 5 by supporting up to eight downlink spatial streams. Even when stations have fewer antennas, such as an access point with eight antennas serving up to four stations with two antennas, the access point can effectively manage multiple connections. The access point dynamically learns the locations of target stations through channel sounding and optimizes data transmission by directly beamforming it toward the intended destinations.
Uplink MU MIMO is a notable addition to Wi-Fi 6, specifically designed to support high-bitrate applications and content streaming. Leveraging MIMO systems, this feature enables up to eight stations to transmit frames simultaneously to the same access point, enhancing the overall efficiency and capacity of the network.
3.5. 1024-QAM
Wi-Fi 6 introduces support for various modulation schemes, including BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, and the advanced 1024-QAM. Among these, the 1024-QAM modulation stands out as it allows the transmission of ten bits simultaneously, contributing to a 25% increase in data rate compared to Wi-Fi 5. However, it’s important to note that 1024-QAM is more susceptible to noise and can only be applied if the channel quality meets certain standards.
Additionally, Wi-Fi 6 benefits from an optional modulation known as Dual Carrier Modulation (DCM). This modulation is specifically designed to address interference challenges during long-distance transmissions, enhancing the reliability and performance of the network in such scenarios.
4. Open Challenges with Wi-Fi 6
4.1. Device Adoption
One of the challenges with any new Wi-Fi standard is the slow adoption of compatible devices. While newer devices are being manufactured with Wi-Fi 6 support, older devices may not be upgraded, limiting the full potential of the network.
4.2. Interoperability
As with any new technology, there can be challenges with interoperability between devices from different manufacturers. This issue tends to resolve over time as standards mature and become more widely adopted.
4.3. Infrastructure Upgrade Costs
Upgrading to Wi-Fi 6 may require infrastructure changes, including new routers and access points. For some organizations or individuals, the cost of upgrading may be a barrier to adoption.
4.4. Backward Compatibility
While Wi-Fi 6 is designed to be backward compatible with previous Wi-Fi standards, there can be challenges in ensuring seamless interoperability with older devices. In some cases, this might require adjustments in network settings.
4.5. Spectrum Crowding
As more devices and networks adopt Wi-Fi 6, there may be increased congestion in the 2.4 GHz and 5 GHz frequency bands. This can impact the overall performance of Wi-Fi networks, although Wi-Fi 6 includes features designed to mitigate this issue.
4.6. Security Concerns
As with any wireless technology, security is a concern. While Wi-Fi 6 includes security improvements, it’s important for users to implement best practices, such as strong encryption and secure password policies.
4.7. Implementation Challenges
Deploying Wi-Fi 6 effectively requires careful planning and consideration of factors such as network architecture, channel allocation, and interference. Proper configuration is crucial to realizing the benefits of the new standard.
5. Conclusion
In this article, we provided a comprehensive introduction to Wi-Fi 6, delving into its features and addressing current challenges. By exploring the newly introduced capabilities, we’ve gained insights into how Wi-Fi 6 can elevate transmission capacity, enable explicit resource assignment, foster resource sharing in densely populated networks, and enhance power-saving mechanisms—an aspect particularly pertinent to the Internet of Things.
Since its inception in the 1990s, Wireless Local Area Network (WLAN) technology has consistently expanded its market share, emerging as a crucial platform for delivering wireless data services through Wi-Fi technology. The Wi-Fi 6 standard represents a significant advancement, promising data rates of nearly 10 Gbps, enhanced energy efficiency, and improved reliability.