OFDMA MU-MIMO in Wi-Fi Networks: Opportunities and Challenges

The exponential growth of Wi-Fi-enabled devices and the changing nature of online activities highlight the urgent need to find innovative solutions to solve the ever-growing congestion issue, especially in highly dense environments where the problem is most severe. In order to address this challenge, the 802.11ax standard breaks away from traditional approaches exploited in previous standards by introducing a combined use of Orthogonal Frequency-Division Multiple Access (OFDMA) and Multi-User Multiple-Input Multiple-Output (MU-MIMO) multiplexing techniques: OFDMA MU-MIMO. While prior research explored OFDMA and MU-MIMO individually, this thesis carries out an in-depth analysis of the functioning and the benefits arising from the joint utilization of OFDMA and MU-MIMO, such as significant enhancements in efficiency, link capacity and greater flexibility for diverse applications. Moreover, while analyzing the advantages of this combined approach, this thesis also exposes a critical security flaw within the channel estimation process carried out between the beamformer and the beamformees before the actual data transmission. Such weakness can be easily leveraged for an attack that has the potential of severely degrading the channel performance. This vulnerability, previously explored in the context of 802.11ac with MU-MIMO alone, is now examined under a new light with combined OFDMA MU-MIMO. This work therefore emphasizes the need for further research to mitigate this vulnerability and ensure the secure operation of Wi-Fi networks utilizing OFDMA MU-MIMO.