Self-Organization of Coverage of Densely Deployed WLANs Considering Outermost APs without Generating Coverage Holes

Shotaro KAMIYA  Keita NAGASHIMA  Koji YAMAMOTO  Takayuki NISHIO  Masahiro MORIKURA  Tomoyuki SUGIHARA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E99-B   No.9   pp.1980-1988
Publication Date: 2016/09/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2016SNP0020
Type of Manuscript: Special Section PAPER (Special Section on Integration Technologies of Ambient Intelligence and Sensor Networks)
Category: 
Keyword: 
coverage adaptation,  IEEE 802.11 WLAN,  transmission power control,  area coverage hole,  coverage boundary,  

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Summary: 
In densely deployed wireless local area network (WLAN) environments, the arbitrary deployment of WLAN access points (APs) can cause serious cell overlaps among APs. In such situations, the ability to realize adaptable coverage using transmission power control (TPC) is effective for improving the area spectral efficiency. Meanwhile, it should be guaranteed that no coverage holes occur and that connectivity between APs and wireless stations (STAs) is maintained. In this paper, the self-organization of coverage domains of APs using TPC is proposed. The proposed technique reduces the incidence of coverage overlaps without generating area coverage holes. To detect coverage holes, STAs and/or APs are used as sensors that inform each AP of whether or not the points at which they exist are covered by the APs. However, there is a problem with this approach in that when the density of STAs is not sufficiently large, the occurrence of area coverage holes is inevitable because the points at which the sensors do not exist are not guaranteed to be covered by APs. This paper overcomes the problem by focusing APs that belong to network's outer boundary (boundary APs) and prohibiting the APs from operating at low transmission power levels, the idea being that the coverage domains of such APs always include the region covered by only those APs. The boundary APs are determined by performing Delaunay triangulation of the set of points at which all APs exist. Simulation results confirm the effectiveness of the proposed TPC scheme in terms of its ability to reduce the total overlap area while avoiding the occurrence of area coverage holes.