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Dense deployment of access points in 60 GHz WLANs can provide always-on gigabit connectivity and robustness against blockages to mobile clients. However, this dense deployment can lead to harmful interference between the links, affecting link data rates. In this paper, we attempt to better understand the interference characteristics and effectiveness of interference mitigation techniques using 802.11ad COTS devices and 60 GHz software radio based measurements. We first find that current 802.11ad COTS devices do not consider interference in sector selection, resulting in high interference and low spatial reuse. We consider three techniques of interference mitigation - channelization, sector selection and receive beamforming. First, our results show that channelization is effective but 60 GHz channels have non-negligible adjacent and non-adjacent channel interference. Second, we show that it is possible to perform interference-aware sector selection to reduce interference but its gains can be limited in indoor environment with reflections, and such sector selection should consider fairness in medium access and avoid asymmetric interference. Third, we characterize the efficacy of receive beamforming in combating interference and quantify the related overhead involved in the search for receive sector, especially in presence of blockages. We elaborate on the insights gained through the characterization and point out important outstanding problems through the study. 

60 GHz millimeter-wave WLANs are gaining traction with their ability to provide multi-gigabit per second data rates. In spite of their potential, link outages due to human body blockage remain a challenging outstanding problem. In this work, we propose mmChoir, a novel proactive blockage mitigation technique that utilizes joint transmissions from multiple Access Points (APs) to provide blockage resilience to clients. We derive a new reliability metric based on angular spread of incoming paths to a client and their blockage probabilities. The metric can be used to intelligently select joint transmissions that can provide higher reliability. The reliability metric along with a novel interference estimation model, is used by mmChoir's scheduler to judiciously schedule joint transmissions, and increase network capacity and reliability. Our testbed and trace-driven simulations show that mmChoir can outperform existing beamswitching based blockage mitigation scheme with on an average 58% higher network throughput.