While customers rivet their eyes on Wi-Fi 6, in the bowels of the IEEE 802.11 Working Group that creates Wi-Fi standards, the next generationWi-Fi is being developed. At the very first sight, the new IEEE 802.11be amendment to the Wi-Fi standard is nothing but scaled 11ax with doubled bandwidth and the increased number of spatial streams, which together provide data rates as high as 40 Gbps. A bit deeper dive into the 802.11 activities reveals that 11be will support real-time applications. In reality, 11be introduces many more revolutionary changes to Wi-Fi, which will form a basement for further Wi-Fi evolution. Although by now (May 2020), the development process is at the very early phase without any draft specification, the analysis of the discussion in the 802.11 Working Group gives insights into the main innovations of 11be. In addition to the ones above, they include native multi-link operation, channel sounding optimization that opens the door for massive MIMO, advanced PHY and MAC techniques, the cooperation of various access points. The paper analyzes hundreds of features proposed for the new technology, focusing on the open problems that can be solved by the researchers who want to contribute to the development of 802.11be.

The upcoming IEEE 802.11be standard, known as Wi-Fi 7, introduces the multi-link operation, which allows a Wi-Fi device to transmit and receive packets via several links simultaneously. However, in some cases, e.g., when the spectral distance between two channels used by the links is small, cross-link interference caused by the transmission on one link can impair the transmission on another link. 802.11be defines operation rules for this case called the non-simultaneous transmit and receive (NSTR) mode. Particularly, the specification requires simultaneous transmissions on different links to be aligned. Otherwise, the transmission shall be performed on only one link. This paper develops an analytical approach to model NSTR operation and computes the throughput in a saturated network when NSTR multi-link devices coexist with legacy devices.

Native support for multi-link operation is a key novelty of the future Wi-Fi 7 technology defined by the IEEE 802.11be standard, which is currently under development. With the 6 GHz band recently granted for Wi-Fi operation, the novel multi-link feature enables simultaneous usage of multiple wide channels. Thus, it multiplies the capacity of Wi-Fi networks well beyond the 30 Gbps target of Wi-Fi 7. However, not all stations can simultaneously transmit and receive (STR) information on several links because of cross-channel interference. That is why it is proposed to synchronize the transmissions on different channels. The presence of legacy stations not supporting the multi-link operation raises many issues related to multi-link channel access performance and fairness. This paper evaluates various channel access approaches considered in the context of the Wi-Fi 7 non-STR operation and discusses how to organize channel access in multi-link Wi-Fi 7 congested networks to be both efficient and fair, even in the presence of legacy stations.

Non-orthogonal multiple access (NOMA) is a well-accepted technology for future Wi-Fi systems to improve spectral efficiency. NOMA allows an access point (AP) to simultaneously serve multiple devices by splitting the transmit power between them. Using the superposition coding the AP combines signals of different frames with predefined power weights. However, as it is already known, the phase noise caused by hardware imperfections limits the performance of NOMA transmissions. The paper proposes a practical, easy-to-implement, and backward-compatible method to rotate the constellation of the low power signal in order to make it more robust to the phase noise. A mathematical model is developed to find such a rotation angle that minimizes the bit error rate (BER) of the low power frame. A new NOMA Wi-Fi prototype testbed is developed with the new feature of constellation rotation ability, which is used to validate the performance of our proposed method. Many experimental results show the proposed constellation rotation approach significantly decreases the BER in high signal-to-noise scenarios.

Wi-Fi is evolving to support new areas such as extended reality, Industrial Internet of Things, and environments with numerous devices. Unlike previous generations that aimed to maximize peak and user-perceived throughput, Wi-Fi 8 (also known as IEEE 802.11bn Ultra High Reliability) intends to make Wi-Fi operation more reliable, i.e., to improve performance across the full range of scenarios, particularly in worst-case conditions. Specifically, 802.11bn is striving to increase throughput at various signal to interference and noise ratio levels, diminish the 95th percentile of latency, decrease packet losses, and reduce power consumption. To attain these ambitions, Wi-Fi 8 is going to introduce a series of groundbreaking mechanisms, including distributed-tone resource units, unequal modulations, prioritized and non-primary channel access, advanced roaming features, multi-AP coordination, and so on. We present the current status of Wi-Fi 8 development with an emphasis on the targets and enabling technologies. This tutorial also discusses open research directions that require the development of new intelligent methods and algorithms.

The upcoming IEEE 802.11be standard, aka Wi-Fi 7, introduces native support for the multilink operation. It allows Wi-Fi 7 devices to use several links located at different frequency channels simultaneously. However, in some cases, e.g., when the links operate on the channels close to each other, cross-link interference prevents sensing the channel on one link while transmitting on the other one. Thus, at any moment in time, such a device shall not perform simultaneous transmission and receptions but should only do synchronous transmission or synchronous reception. However, in the presence of legacy devices that support only one link, the channel state on different links is not synchronized, reducing the probability of starting transmission on both links synchronously. Intuitively, to improve performance, the devices shall try to align their transmissions with ongoing ones, which should allow them to start simultaneous transmission on both links next time. With extensive simulation in various scenarios, this paper shows that the performance of multilink devices degrades in the presence of legacy devices and the described intuitive approach only improves the performance of legacy devices rather than multilink devices.