IET Communications
Research Article
Localisation algorithm with node selection
under power constraint in software-defined
sensor networks
ISSN 1751-8628
Received on 21st January 2017
Revised 8th April 2017
Accepted on 13th June 2017
E-First on 19th September 2017
doi: 10.1049/iet-com.2017.0077
www.ietdl.org
Yaping Zhu
1
, Song Xing
2
, Yueyue Zhang
1
, Feng Yan
1,3
, Lianfeng Shen
1
1
National Mobile Communications Research Laboratory, Southeast University, Nanjing, People's Republic of China
2
Department of Information Systems, California State University, Los Angeles, CA 90032, USA
3
State key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, Beijing, People's Republic
of China
E-mail: lfshen@seu.edu.cn
Abstract: In this study, the authors propose an improved localisation algorithm in the software-defined sensor networks
(SDSNs). This algorithm includes a node-selection strategy under the whole network power constraint, based on the software-
defined networking (SDN) technique for providing the centralised control of the network. The analogous Cramer-Rao lower
bound (A-CRLB) value is derived for each participating node, which represents a fundamental bound on the variance of the
position estimator and is used to evaluate the contribution of each node to localisation accuracy. On the basis of A-CRLB
values, the most helpful nodes for localisation are selected to maximise the sum of the nodes' contributory values to the
localisation accuracy. With the global network knowledge provided by the SDN controller in the SDSN, the node-selection
strategy is formulated into a 0-1 programming problem on the premise of power satisfaction of each node. Furthermore, the
proposed node-selection -based localisation algorithm is applied to both noncooperative and cooperative localisation scenarios.
Simulation results show that the proposed algorithms provide efficient and effective localisation schemes in SDSNs, and can
improve the performance in terms of both the selection convergence speed and the localisation accuracy.
1 Introduction
With the upsurge of sensor applications and the advancement of
sensor technologies, wireless sensor networks (WSNs) are
envisioning a rich variety of promising services in many fields
such as search-and-rescue operations, environmental monitoring,
and precision agriculture. For these applications, the wireless
sensor nodes localisation has attracted considerable attentions over
the past decades in WSNs [1, 2]. In node localisation for WSNs,
the positions of the agent nodes can be estimated through two
methods named non-cooperative localisation and cooperative
localisation. In non-cooperative localisation, the position
estimation only uses the knowledge of a few anchor nodes with
known locations. While in cooperative localisation, the inter-node
range measurements between agent nodes are also used. The
transmitted signals from the source nodes (i.e. the anchor nodes in
non-cooperative localisation scenario, the anchor nodes and agent
nodes in cooperative localisation scenario) are generally used to
provide the position-related range measurements for the target node
(i.e. the agent node). Such range-based localisation techniques can
be categorised into the time-of-arrival (TOA) [3–5], time-
difference-of-arrival [6, 7], angle-of-arrival [8], received signal
strength (RSS) [9, 10], and some hybrid schemes [11–13]. No
matter which range measurement method is adopted, the power of
transmitting signal plays a critical role in the accuracy of position
estimate. In addition, it is related to the throughput and lifetime of
the network. Owing to the energy-limited nature of WSNs,
research of power allocation algorithm for WSN localisation is of
vital importance, since it affects not only the localisation
performance but also the network lifetime [14, 15].
In recent years, various power allocation strategies to improve
the node localisation accuracy and reduce the entire network power
consumption have been investigated. For example, an optimisation
framework for robust power allocation schemes in node
localisation with imperfect knowledge of network parameters is
presented in [16], which is formulated to minimise the localisation
errors for a given power budget. A ranging energy optimisation
method for an unsynchronised positioning system is introduced in
[17], which features a robust sensor positioning in the sense that a
specific accuracy requirement is fulfilled within a prescribed
service area. In [18], a performance-driven resource allocation
scheme for multiple radar systems is proposed and it minimises the
total transmitted power for a predefined mean squares error (MSE)
of localisation estimation. The proposed scheme uses the Cramer–
Rao (CR) bound as an optimisation metric and limits the
transmitted power at each station within an acceptable range.
Another typical strategy to conserve the network power
consumption is to manage and select nodes in an optimal way
during the localisation, which can reduce the number of actively
participating nodes. However, due to the decentralised and
dynamic nature of WSN architecture, it is difficult to manage the
sensor nodes over the entire network. Although developing a
network management system (NMS) for distributed WSNs is a first
demanding task in many applications, NMS is usually scheduled as
the second phase in practical project planning. These render the
WSN prone to be less versatile in node management. To our best
knowledge, existing approaches for node selection in WSN
localisation are mostly distributed. Distributed approaches are
more favorable in implementation due to the ad hoc nature of
WSNs, nevertheless they are generally suboptimal for the lack of
entire network knowledge compared with the centralised ones.
Recently, an emerged software-defined SN (SDSN)
architecture, which introduces the fundamental idea of SD
networking (SDN) [19] into WSNs, has become more attractive for
application-specific wireless communications. In SD networks,
there are two communication planes: the physical data plane and
the abstracted control plane which has a centralised control and
view of the whole network [20, 21]. The separation of data and
control planes makes SDSN programmable and thus the structure
of network becomes dynamic. It is also worth noting that the SD
technique in SDSNs provides a chance to break the limitation in
designing node-selection strategies and seek for an optimal
solution from a global perspective [22]. To benefit from SDSN's
high adaptability nature, it is worth exploring the adaptive
localisation algorithms that take the full advantage of node
management in SDSNs. The authors in [23] investigate localisation
IET Commun., 2017, Vol. 11 Iss. 13, pp. 2035-2041
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