The IEEE 802.11p Wireless Access in Vehicular Environment (WAVE) protocol providing for vehicle-toinfrastructure and vehicle-to-vehicle radio communication is currently under standardization. We provide an NS-2 simulation study of the proposed IEEE 802.11p MAC protocol focusing on vehicle-to-infrastructure communication. We show that the specified MAC parameters for this protocol can lead to undesired throughput performance because the backoff window sizes are not adaptive to dynamics in the numbers of vehicles attempting to communicate. We propose two solutions to this problem. One is a centralized approach where exact information about the number of concurrent transmitting vehicles is used to calculate the optimal window size, and the other is a distributed approach in which vehicles use local observations to adapt the window size. We show that these schemes can provide significant improvements over the standard MAC protocol under dense and dynamic conditions.

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Background During the COVID-19 pandemic, American Society for Testing and Materials level 3 and level 2 medical face masks (MFMs) have been used for most health care workers and even for the first responders owing to a shortage of N95 respirators. However, the MFMs lack effective peripheral seal, leading to concerns about their adequacy to block aerosol exposure for proper protection. The purpose of this study was to evaluate the peripheral seal of level 3 and level 2 MFMs with a 3-dimensional (3D-) printed custom frame. Methods Level 3 and level 2 MFMs were tested on 10 participants with and without a 3D-printed custom frame; the efficiency of mask peripheral seal was determined by means of quantitative fit testing using a PortaCount Fit Tester based on ambient aerosol condensation nuclei counter protocol. Results The 3D-printed custom frame significantly improved the peripheral seal of both level 3 and level 2 MFMs compared with the masks alone ( P < .001). In addition, both level 3 and level 2 MFMs with the 3D-printed custom frame met the quantitative fit testing standard specified for N95 respirators. Practical Implications The 3D-printed custom frame over level 3 and level 2 MFMs can offer enhanced peripheral reduction of aerosols when using collapsible masks. With the shortage of N95 respirators, using the 3D-printed custom frame over a level 3 or level 2 MFM is considered a practical alternative to dental professionals.

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