Blockage-Aware Robust Beamforming in RIS-Aided Mobile Millimeter Wave MIMO Systems

Millimeter wave (mmWave) communications are sensitive to blockage over radio propagation paths. The emerging paradigm of reconfigurable intelligent surface (RIS) has the potential to overcome this issue by its ability to arbitrarily reflect the incident signals toward desired directions. This paper proposes a Neyman-Pearson (NP) criterion-based blockage-aware algorithm to improve communication resilience against blockage in mobile mmWave multiple input multiple output (MIMO) systems. By virtue of this pragmatic blockage-aware technique, we further propose an outage-constrained beamforming design for downlink mmWave MIMO transmission to achieve outage probability minimization and achievable rate maximization. To minimize the outage probability, a robust RIS beamformer with variant beamwidth is designed to combat uncertain channel state information (CSI). For the rate maximization problem, an accelerated projected gradient descent (PGD) algorithm is developed to solve the computational challenge of high-dimensional RIS phase-shift matrix (PSM) optimization. Particularly, we leverage a subspace constraint to reduce the scope of the projection operation and formulate a new Nesterov momentum acceleration scheme to speed up the convergence process of PGD. Extensive experiments confirm the effectiveness of the proposed blockage-aware approach, and the proposed accelerated PGD algorithm outperforms a number of representative baseline algorithms in terms of the achievable rate

RIS-Assisted Mobile Millimeter Wave MIMO Communications:A Blockage-Aware Robust Beamforming Approach

Millimeter wave (mmWave) communications are highly affected by blockage, whereas the emerging reconfigurable intelligent surface (RIS) has the potential to overcome this issue. This paper proposes a Neyman Pearson (N-P) criterion-based blockage-aware algorithm to improve resilience to blockage in mobile mmWave multiple input multiple output (MIMO) systems. By virtue of this pragmatic blockage-aware technique, we further propose an outage-constrained beamforming design for RIS-assisted mmWave MIMO transmission to achieve outage probability minimization and achievable rate maximization. Specifically, we propose an accelerated projected gradient descent (PGD) algorithm to solve the computational challenge of high dimensional RIS phase-shift matrix (PSM) optimization. Particularly, we formulate a new Nesterov momentum ac celeration scheme to speed up the convergence rate. Exten sive experiments confirm the effectiveness of the proposed blockage-aware approach and the proposed accelerated PGD algorithm outperforms a number of representative baseline algorithms in terms of the achievable rate performance

Cavernous Transformation of the Portal Vein Might Increase the Risk of Liver Abscess

Cavernous transformation of the portal vein (CTPV) is not quite common in adults, and cases with CTPV and acute liver abscess are lacking. We report a patient with CTPV inducing extrahepatic and intrahepatic obstruction, finally leading to acute liver abscess due to bile duct infection. We aim to find out the possible relationship between CTPV and acute liver abscess. A 45-year-old female patient was admitted to our hospital for recurrent upper abdominal pain and distension for one year, aggravated with fever for three years. A diagnosis of CTPV and liver abscess was made by 16-slice computed tomography. Effective antibiotics and drainage were used for this patients, and she was eventually cured. When treating patients with CTPV, extrahepatic and intrahepatic obstruction, one should be aware of the presence of acute liver abscess, and empirical antibiotics might be valuable