312 research outputs found
Correlated Blocking in mmWave Cellular Networks: Macrodiversity, Outage, and Interference
In this paper, we provide a comprehensive analysis of macrodiversity for millimeter wave (mmWave) cellular networks. The key issue with mmWave networks is that signals are prone to blocking by objects in the environment, which causes paths to go from line-of-sight (LOS) to non-LOS (NLOS). We identify macrodiversity as an important strategy for mitigating blocking, as with macrodiversity the user will attempt to connect with two or more base stations. Diversity is achieved because if the closest base station is blocked, then the next base station might still be unblocked. However, since it is possible for a single blockage to simultaneously block the paths to two base stations, the issue of correlated blocking must be taken into account by the analysis. Our analysis characterizes the macrodiverity gain in the presence of correlated random blocking and interference. To do so, we develop a framework to determine distributions for the LOS probability, Signal to Noise Ratio (SNR), and Signal to Interference and Noise Ratio (SINR) by taking into account correlated blocking. We validate our framework by comparing our analysis, which models blockages using a random point process, with an analysis that uses real-world data to account for blockage. We consider a cellular uplink with both diversity combining and selection combining schemes. We also study the impact of blockage size and blockage density along with the effect of co-channel interference arising from other cells. We show that the assumption of independent blocking can lead to an incorrect evaluation of macrodiversity gain, as the correlation tends to decrease macrodiversity gain
Exploiting Randomly-located Blockages for Large-Scale Deployment of Intelligent Surfaces
One of the promising technologies for the next generation wireless networks
is the reconfigurable intelligent surfaces (RISs). This technology provides
planar surfaces the capability to manipulate the reflected waves of impinging
signals, which leads to a more controllable wireless environment. One potential
use case of such technology is providing indirect line-of-sight (LoS) links
between mobile users and base stations (BSs) which do not have direct LoS
channels. Objects that act as blockages for the communication links, such as
buildings or trees, can be equipped with RISs to enhance the coverage
probability of the cellular network through providing extra indirect LoS-links.
In this paper, we use tools from stochastic geometry to study the effect of
large-scale deployment of RISs on the performance of cellular networks. In
particular, we model the blockages using the line Boolean model. For this
setup, we study how equipping a subset of the blockages with RISs will enhance
the performance of the cellular network. We first derive the ratio of the
blind-spots to the total area. Next, we derive the probability that a typical
mobile user associates with a BS using an RIS. Finally, we derive the
probability distribution of the path-loss between the typical user and its
associated BS. We draw multiple useful system-level insights from the proposed
analysis. For instance, we show that deployment of RISs highly improves the
coverage regions of the BSs. Furthermore, we show that to ensure that the ratio
of blind-spots to the total area is below 10^5, the required density of RISs
increases from just 6 RISs/km2 when the density of the blockages is 300
blockage/km^2 to 490 RISs/km^2 when the density of the blockages is 700
blockage/km^2.Comment: Accepted in IEEE Journal on Selected Areas in Communication
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