6 research outputs found
Two-tier Spatial Modeling of Base Stations in Cellular Networks
Poisson Point Process (PPP) has been widely adopted as an efficient model for
the spatial distribution of base stations (BSs) in cellular networks. However,
real BSs deployment are rarely completely random, due to environmental impact
on actual site planning. Particularly, for multi-tier heterogeneous cellular
networks, operators have to place different BSs according to local coverage and
capacity requirement, and the diversity of BSs' functions may result in
different spatial patterns on each networking tier. In this paper, we consider
a two-tier scenario that consists of macrocell and microcell BSs in cellular
networks. By analyzing these two tiers separately and applying both classical
statistics and network performance as evaluation metrics, we obtain accurate
spatial model of BSs deployment for each tier. Basically, we verify the
inaccuracy of using PPP in BS locations modeling for either macrocells or
microcells. Specifically, we find that the first tier with macrocell BSs is
dispersed and can be precisely modelled by Strauss point process, while Matern
cluster process captures the second tier's aggregation nature very well. These
statistical models coincide with the inherent properties of macrocell and
microcell BSs respectively, thus providing a new perspective in understanding
the relationship between spatial structure and operational functions of BSs
Characterizing Spatial Patterns of Base Stations in Cellular Networks
The topology of base stations (BSs) in cellular networks, serving as a basis
of networking performance analysis, is considered to be obviously distinctive
with the traditional hexagonal grid or square lattice model, thus stimulating a
fundamental rethinking. Recently, stochastic geometry based models, especially
the Poisson point process (PPP), attracts an ever-increasing popularity in
modeling BS deployment of cellular networks due to its merits of tractability
and capability for capturing nonuniformity. In this study, a detailed
comparison between common stochastic models and real BS locations is performed.
Results indicate that the PPP fails to precisely characterize either urban or
rural BS deployment. Furthermore, the topology of real data in both regions are
examined and distinguished by statistical methods according to the point
interaction trends they exhibit. By comparing the corresponding real data with
aggregative point process models as well as repulsive point process models, we
verify that the capacity-centric deployment in urban areas can be modeled by
typical aggregative processes such as the Matern cluster process, while the
coverage-centric deployment in rural areas can be modeled by representativ
Large-scale Spatial Distribution Identification of Base Stations in Cellular Networks
The performance of cellular system significantly depends on its network
topology, where the spatial deployment of base stations (BSs) plays a key role
in the downlink scenario. Moreover, cellular networks are undergoing a
heterogeneous evolution, which introduces unplanned deployment of smaller BSs,
thus complicating the performance evaluation even further. In this paper, based
on large amount of real BS locations data, we present a comprehensive analysis
on the spatial modeling of cellular network structure. Unlike the related
works, we divide the BSs into different subsets according to geographical
factor (e.g. urban or rural) and functional type (e.g. macrocells or
microcells), and perform detailed spatial analysis to each subset. After
examining the accuracy of Poisson point process (PPP) in BS locations modeling,
we take into account the Gibbs point processes as well as Neyman-Scott point
processes and compare their accuracy in view of large-scale modeling test.
Finally, we declare the inaccuracy of the PPP model, and reveal the general
clustering nature of BSs deployment, which distinctly violates the traditional
assumption. This paper carries out a first large-scale identification regarding
available literatures, and provides more realistic and more general results to
contribute to the performance analysis for the forthcoming heterogeneous
cellular networks
A third (booster) dose of the inactivated SARS-CoV-2 vaccine elicits immunogenicity and T follicular helper cell responses in people living with HIV
IntroductionThis study sought to explore the immunogenicity of a booster dose of an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine in people living with human immunodeficiency virus (HIV) and identify the factors affecting the magnitude of anti-SARS-CoV-2 antibody levels.Materials and methodsA total of 34 people living with HIV (PLWH) and 34 healthy donors (HD) were administered a booster dose of the same SARS-CoV-2 vaccine. Anti-SARS-CoV-2 antibody and immunoglobulin G (IgG) levels were measured using the SARS-CoV-2 S protein neutralizing antibody Enzyme-Linked Immunosorbent Assay (ELISA) and 2019-nCov IgG Chemiluminescent Immunoassay Microparticles, respectively. Spearman correlation analysis was used to measure the correlation between laboratory markers and neutralizing antibody and IgG levels. Peripheral blood mononuclear cells (PBMCs) were extracted from each subject using density gradient centrifugation and the numbers of memory T and T follicular helper (Tfh) cells were determined using flow cytometry.ResultsPLWH had a marked reduction in CD4 and B cell levels that was accompanied by a lower CD4/CD8 T cell ratio. However, those who received a supplementary dose of inactivated SARS-CoV-2 vaccines exhibited antibody positivity rates that were analogous to levels previously observed. The booster vaccine led to a reduction in IgG and neutralizing antibody levels and the amplitude of this decline was substantially higher in the PLWH than HD group. Correlation analyses revealed a strong correlation between neutralizing antibody levels and the count and proportion of CD4 cells. Anti-SARS-CoV-2 IgG antibody levels followed a similar trend. The expression of memory T and Tfh cells was considerably lower in the PLWH than in the HD group.DiscussionPLWH had an attenuated immune response to a third (booster) administration of an inactivated SARS-CoV-2 vaccine, as shown by lower neutralizing antibody and IgG levels. This could be attributed to the reduced responsiveness of CD4 cells, particularly memory T and cTfh subsets. CD4 and cTfh cells may serve as pivotal markers of enduring and protective antibody levels. Vaccination dose recalibration may be critical for HIV-positive individuals, particularly those with a lower proportion of CD4 and Tfh cells
Large-scale Spatial Distribution Identification of Base Stations in Cellular Networks
International audienceThe performance of cellular system significantlydepends on its network topology while cellular networks areundergoing a heterogeneous evolution. This promising trendintroduces unplanned deployment of smaller base stations (BSs),thus complicating the performance evaluation even further. Inthis paper, based on large amount of real BS locations data,we present a comprehensive analysis on the spatial modeling ofcellular network structure. Unlike the related works, we dividethe BSs into different subsets according to geographical factor(e.g. urban or rural) and functional type (e.g. macrocells ormicrocells), and perform detailed spatial analysis to each subset.After recovering the inaccuracy of the Poisson point process(PPP) in BS locations modeling, we take into account the Gibbspoint processes as well as Neyman-Scott point processes andcompare their performance in view of large-scale modeling test.Finally, we turn to the BS quantitative distribution analysis,and reveal the general clustering nature of BSs deployment,which distinctly violates the traditional assumption. Specifically,the -Stable distribution can most precisely reproduce the BSdensity among the popular candidate distributions. This papercarries out a first large-scale identification regarding availableliteratures, and provides more realistic and general results tocontribute to the performance analysis for the forthcomingheterogeneous cellular networks