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TVWS assisted performance anomaly mitigation exploiting spectrum heterogeneity
Shin, Kyubo,Kim, Hyoil,Chun, Se Young,Shin, Donghoon Elsevier 2018 COMPUTER NETWORKS - Vol.141 No.-
<P><B>Abstract</B></P> <P>Super Wi-Fi is a Wi-Fi-like service utilizing TV white spaces (TVWS), which has been revealed to provide higher data rates in the outskirts of Wi-Fi’s coverage, thanks to the spectrum heterogeneity between Wi-Fi bands and TVWS. Motivated by this, this paper proposes co-locating a Super Wi-Fi access point (AP) with a Wi-Fi AP aiming to mitigate the performance anomaly of the WLAN by relocating low-rate Wi-Fi stations (STAs) to Super Wi-Fi in the outskirts of Wi-Fi’s coverage. Then, the proposed strategy can enhance average per-STA throughput of both Wi-Fi STAs and relocated Super Wi-Fi STAs while also improving the data rate of Super Wi-Fi STAs, than they would achieve with the legacy Wi-Fi. To quantify such performance improvement, we model the system as a series of two-dimensional Markov chains and provide an in-depth analysis of steady-state probabilities and per-STA throughput. Numerical analysis has shown that Super Wi-Fi co-location improves <I>not only</I> average per-STA throughput <I>but also</I> spectral efficiency, compared to the legacy Wi-Fi with 20 or 20+20 MHz bandwidth for the single BSS scenario. In addition, average per-STA throughput and spectral efficiency are also enhanced in the OBSS scenario both in rural and urban environments. Hence, the co-location strategy is proven to be quite effective in enhancing WLAN’s performance.</P>
Park, Jong Min,Kim, Kyubo,Park, Jong In,Shin, Kyung Hwan,Jin, Ung Sik,Kim, Jung-in Institute of Physics in association with the Ameri 2017 Physics in medicine & biology Vol.62 No.12
<P>To investigate the dosimetric effect of the internal metallic port (IMP) in a tissue expander (TE) on the dose distribution of postmastectomy radiation therapy (PMRT). A total of 10 patients who have received PMRT with a TE were selected retrospectively. For each patient, the dose distributions of treatment plans with a 10 MV photon beam were calculated using the Monte Carlo (MC) method with CT images. The dose distributions without the TE were also calculated by designating the mass densities of the TE including the IMP as those of tissue. From the MC calculations, the dose-volumetric parameters were calculated and analyzed for several structures: the planning target volume (PTV) including the TE, the PTV excluding the TE (PTV<SUB>real</SUB>), the TE alone, heart, and lungs. For the PTV and PTV<SUB>real</SUB>, dose-volumetric parameters did not appear to depend on the IMP. Within the TE volume, the maximum dose and <I>D</I> <SUB>1%</SUB> were higher with the IMP than without the IMP (62.8 ± 1.4 Gy versus 57.9 ± 1.3 Gy with <I>p</I> < 0.001 and 58.6 ± 1.6 Gy versus 57.0 ± 1.2 Gy with <I>p</I> = 0.035). The values of <I>V</I> <SUB>100%</SUB> and <I>V</I> <SUB>95%</SUB> were lower with the IMP than without the IMP (77.9% ± 7.6% versus 87.2% ± 5.3% with <I>p</I> = 0.008 and 89.5% ± 5.6% versus 94.6% ± 2.9% with <I>p</I> = 0.027). The IMP did not affect dose-volumetric parameters of heart and lungs. Dosimetric changes due to the IMP occurred mainly within the TE, and not in the target volume, heart, and lungs.</P>