NOMA is a promising way to increase spectral efficiency recently discussed in the IEEE 802.11 Working Group that develops WiFi standards. NOMA can be very beneficial in a WiFi network where the qualities of the channel between the access point and associated stations are significantly different. In such scenarios, NOMA allows the access point to transmit several data streams to various stations in parallel using one antenna and the same time-frequency resources. This article presents and evaluates the first-ever prototype of a WiFi device supporting NOMA, implemented in a software-defined radio platform. The prototype is backward compatible with legacy WiFi versions. Specifically, one of the multiplexed streams may be received by a legacy station not supporting NOMA. This feature is favorable for heterogeneous deployments with various generations of WiFi devices. This article provides a detailed description of the prototype as well as experimental results showing from 37 percent to 100 percent gain achieved by including NOMA in the future 802.11 standards.

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.

Reconfigurable Intelligent Surfaces (RISs) are a promising way to improve the performance of wireless networks. However, despite the high interest in the research community, no flexible enough simulation platform allows for studying the performance of wireless communication systems with RIS in complex scenarios. To address this issue, the paper presents an open-source channel simulation platform to study RIS in wireless communication systems. The developed open-source platform extends the QuaDRiGa channel model, which is widely used for the performance evaluation of 5G and Wi-Fi networks with multiple antennas. The paper shows how to use the platform — called QRIS — to evaluate RIS in various frequency conditions, such as indoor/outdoor scenarios and multiple-RIS deployments.

Non-Orthogonal Multiple Access (NOMA) is currently considering as a promising technology for increasing the network efficiency in heterogeneous scenarios with different types of traffic and interference conditions. In spite of numerous theoretical works, there are few experimental studies of NOMA, most of which consider cellular networks. In this short paper, we present our pioneering NOMA testbed for Wi-Fi networks. Because the Wi-Fi technology is much simpler and cheaper than the cellular ones, we expect that the testbed can be used by the research community to validate various solutions designed for NOMA in real equipment.

In order to meet the rising demands for the Internet of Things technologies, Wi-Fi community has developed Wi-Fi HaLow. It extends Wi-Fi with new functionality supporting high number of autonomous devices with various power capabilities and traffic patterns. In the paper, we study the cooperation of such new mechanisms as TIM Segmentation and Restricted Access Window. TIM Segmentation reduces energy consumption for low-power devices retrieving data from the Access Point, while Restricted Access Window reduces contention and allows the Access Point to protect stations with different capabilities from interfering each other. We consider joint usage of these mechanisms in a heterogeneous network with a high number of low-power stations with rare traffic and several powered stations with saturated traffic. Specifically, for TIM Segmentation and Restricted Access Window we develop a simple and fairly accurate mathematical method to set up the parameters of the mechanisms in order to improve performance for both types of stations, i.e. to reduce power consumption for low-power stations and to increase throughput for the other ones.