LCS: Compressive Sensing based Device-Free
Localization for Multiple Targets in Sensor Networks
Ju Wang
1
, Dingyi Fang
1
, Xiaojiang Chen
1
, Zhe Yang
2
, Tianzhang Xing
1
, Lin Cai
2
School of Information Science and Technology, Northwest University, Xi’an, China
1
University of Victoria, Victoria, BC, Canada
2
Email: wangju.nwu@foxmail.com
1
, {dyf, xjchen, XTZ}@nwu.edu.cn
1
, yangzhe2007@gmail.com
2
, cai@ece.uvic.ca
2
Abstract—Location information is important for monitoring and
finding out the behavioral and ecological patterns of wildlife.
According to the wildlife living condition and environment,
localization for wildlife must satisfy special requirements, such as
sparse deployment, device-free, multiple targets and scalability.
Those requirements are abstracted as a device-free multiple
target localization problem under the large-scale sparse
deployment constraint. In this paper, we present a sparse
deployment scenario under which device-free localization method
is feasible. The key observation is that given a pair of nodes, the
received signal strength (RSS) will be different when a target
locates at different locations. By comprehensive modeling and
analyzing the signal propagation properties, we are able to model
the interfered dynamic signals caused by the target as a function
of the location. Taking advantage of compressive sensing in
sparse recovery to handle the sparse property of the localization
problem, (i.e., the vector which contains the number and location
information of k targets is an ideal k-sparse signal), we propose a
scalable compressive sensing based multiple target counting and
localization method (LCS) and rigorously justify the validity of
the problem formulation. We have evaluated the performance of
LCS through extensive experiments in realistic sparse
deployment and large-scale simulations. The results illustrate the
effectiveness and advantages of the LCS method.
Keywords-sensor networks; compressive sensing; device-free
localization; sparse deployment
I. INTRODUCTION
With the expanding of human activity range, wildlife is
increasingly threatened. The key issue of protecting wildlife is
how to find out their behavioral and ecological patterns [1].
The lack of effective monitoring methods is one of the biggest
obstacles [2]. Fortunately, wireless sensor network (WSN)
shows great potential for zoologists to know more about the
behavioral and ecological patterns of wildlife. Many self-
organized WSN have been applied in the real wildlife
applications, e.g., observing the zebra’s daily activities [3],
monitoring the swallow’s micro-environment [4] and finding
the European Badgers’ living habits
[5].
One of the most important information for wildlife is the
location information. However the following four challenges
exist in the wildlife localization:
1) Sparse deployment: A basic requirement for monitoring
wildlife is that the artificial equipments do not disturb the wild
environment and the living habits of wildlife, thus one should
use as less devices as possible, i.e., sparse deployment. Sparse
deployment also benefits for reducing cost, collision space, etc.
2) Device-free localization (DFL): Many localization
methods are device-based, i.e., targets need to carry some
devices (e.g., RFID tag or GPS). But it is hard to attach such
devices on some animal body and zoologists do not favor to
do so. Thus the device-free localization method (i.e., targets
do not
carry any devices) is urgent for monitoring wildlife.
3) Multiple target counting and localization: Compared
with single wildlife’s location information, population
statistical number and location information deeply attract the
interest of zoologists since it is important for zoologists to find
out changes in population size and migration trajectory. Thus
the multiple target counting and localization method is desired
for monitoring wildlife population.
4) Scalability: Wildlife, such as the golden monkey and
zebra, live in the wild environment, and move around large-
scale areas. However, most of recent localization approaches
are small-scale localization method [7]-[14] due to the specific
application environment and the restriction of transmission
range. Thus a scalable localization method is needed.
One of the key problems arises: how to count and locate
multiple targets using a DFL method under a large sparse
deployment area?
In this paper, LCS, a compressive sensing based device-
free multiple target counting and localization method in sensor
networks has been proposed. In order to achieve high accuracy,
most of recent localization approaches are dense deployment
[10] [11]. In this work, we present a sparse deployment
scenario under which LCS can also achieve high localization
accuracy. One of the most popular DFL approaches is the RSS
based DFL method since it does not need additional devices for
WSN. The RSS interference caused by targets is essential for
the RSS based DFL method [9]-[16], so finding a practical
model that can be applied in the real world for DFL is still an
open issue. We give an RSS measurement model which can
accurately estimate RSS when a target is at different locations
of a particular link. According to the model, we have
successfully extracted the RSS dynamic measurements caused
by the target. In this paper, we consider target locations as
sparse signal and propose to reconstruct the signal using the
compressive sensing (CS) [6]. Here we assume that the targets
are sparse compared with the number of grids utilized to