103 research outputs found
Analysis of a Cone-Based Distributed Topology Control Algorithm for Wireless Multi-hop Networks
The topology of a wireless multi-hop network can be controlled by varying the
transmission power at each node. In this paper, we give a detailed analysis of
a cone-based distributed topology control algorithm. This algorithm, introduced
in [16], does not assume that nodes have GPS information available; rather it
depends only on directional information. Roughly speaking, the basic idea of
the algorithm is that a node transmits with the minimum power
required to ensure that in every cone of degree around
, there is some node that can reach with power . We show
that taking is a necessary and sufficient condition to
guarantee that network connectivity is preserved. More precisely, if there is a
path from to when every node communicates at maximum power, then, if
, there is still a path in the smallest symmetric graph
containing all edges such that can communicate with
using power . On the other hand, if ,
connectivity is not necessarily preserved. We also propose a set of
optimizations that further reduce power consumption and prove that they retain
network connectivity. Dynamic reconfiguration in the presence of failures and
mobility is also discussed. Simulation results are presented to demonstrate the
effectiveness of the algorithm and the optimizations.Comment: 10 page
Hapi: A Robust Pseudo-3D Calibration-Free WiFi-based Indoor Localization System
In this paper, we present Hapi, a novel system that uses off-the-shelf
standard WiFi to provide pseudo-3D indoor localization. It estimates the user's
floor and her 2D location on that floor. Hapi is calibration-free, only
requiring the building's floorplans and its WiFi APs' installation location for
deployment. Our analysis shows that while a user can hear APs from nearby
floors as well as her floor, she will typically only receive signals from
spatially closer APs in distant floors, as compared to APs in her floor. This
is due to signal attenuation by floors/ceilings along with the 3D distance
between the APs and the user. Hapi leverages this observation to achieve
accurate and robust location estimates. A deep-learning based method is
proposed to identify the user's floor. Then, the identified floor along with
the user's visible APs from all floors are used to estimate her 2D location
through a novel RSS-Rank Gaussian-based method. Additionally, we present a
regression based method to predict Hapi's location estimates' quality and
employ it within a Kalman Filter to further refine the accuracy. Our evaluation
results, from deployment on various android devices over 6 months with 13
subjects in 5 different up to 9 floors multistory buildings, show that Hapi can
identify the user's exact floor up to 95.2% of the time and her 2D location
with a median accuracy of 3.5m, achieving 52.1% and 76.0% improvement over
related calibration-free state-of-the-art systems respectively.Comment: Accepted for publication in MobiQuitous 2018 - the 15th International
Conference on Mobile and Ubiquitous Systems: Computing, Networking and
Service
Wireless subnet Implementing and
deploying public-area wireless networks present a number of practical challenges, including network security, privacy, authentication, mobility management, and provisioning of key services. FUTURE WIRELESS APPLICATIONS The dawning of the 21st century has seen unprecedented growth in the number of wireless users, applications, and network access technologies. This trend is enabling the vision of pervasive ubiquitous computing where users have network access anytime, anywhere, and applications are location-sensitive and context-aware. To realize this vision, we need to extend network connectivity beyond private networks, such as corporate and university networks, into public spaces like airports, malls, hotels, parks, arenas, and so on — those places where individuals spend a considerable amount of their time outside private networks. In this article we argue that wireless LAN technologies are the ideal mechanism for extending network connectivity to these public places, and enabling location and context-aware applications in them. However, implementing and deploying public area wireless networks (PAWNs) present a number of practical challenges, including network security, privacy, authentication, mobility management, and provisioning of key services. We discuss these challenges as a general problem for PAWNs, and then describe a PAWN we have designed, implemented, and deployed called CHOICE that addresses them. We describe the architecture and components of CHOICE, the service models it supports, and the location services and context-aware applications we have implemented and deployed in it
SSCH: Slotted Seeded Channel Hopping for Capacity Improvement in IEEE 802.11 Ad-Hoc Wireless Networks
Capacity improvement is one of the principal challenges in wireless networking. We present a link-layer protocol called Slotted Seeded Channel Hopping, or SSCH, that increases the capacity of an IEEE 802.11 network by utilizing frequency diversity. SSCH can be implemented in software over an IEEE 802.11-compliant wireless card. Each node using SSCH switches across channels in such a manner that nodes desiring to communicate overlap, while disjoint communications mostly do not overlap, and hence do not interfere with each other. To achieve this, SSCH uses a novel scheme for distributed rendezvous and synchronization. Simulation results show that SSCH significantly increases network capacity in several multi-hop and single-hop wireless networking scenarios
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