Analyzing Effects of Directional Deafness on mmWave Channel Access in Unlicensed Bands

Directional deafness problem is one of the most important challenges in beamforming-based channel access at mmWave frequencies, which is believed to have detrimental effects on system performance in form of excessive delays and significant packet drops. In this paper, we contribute a quantitative analysis of deafness in directional random access systems operating in unlicensed bands by relying on stochastic geometry formulations. We derive a general numerical approach that captures the behavior of deafness probability as well as provide a closed-form solution for a typical sector-shaped antenna model, which is then may be extended to a more realistic two-sector pattern. Finally, employing contemporary IEEE 802.11ad modeling numerology, we illustrate our analysis revealing the importance of deafness-related considerations and their system- level impact.