Toward Multi-User Access Fairness in Reconfigurable Intelligent Surface Assisted Wireless Networks

Reconfigurable intelligent surface (RIS) provides additional physical channels to existing wireless network infrastructure and has attracted intensive research attention to enhance the communication capacity and extend additional user accommodation. Existing RIS researches mainly focus on optimizing the physical-layer channel utilization, and have yet to consider the multi-user fairness of the medium access process when involving the RIS channel. This article shows that RIS can lead to severely unbalanced access opportunities among RIS-assisted users and others from the experimental analysis. Specifically, we demonstrate that due to the capture effect and unbalanced receiving rate of management frames, RIS-assisted users can have unfair competitive priorities for normal users without RIS resources. To overcome such unfair access issues, we propose a novel anti-unfair algorithm that allows equal access opportunities for all kinds of users in a RIS-assisted network. Specifically, we optimize the management frames' modulation and coding scheme (MCS) selections to fight against unexpected bias to balance the access opportunities. We have conducted an experimental evaluation with a practical RIS system showing that the proposed anti-unfair algorithm can significantly alleviate the fairness problem without compromising the network performance.