18,059 research outputs found
Node Repair for Distributed Storage Systems over Fading Channels
Distributed storage systems and associated storage codes can efficiently
store a large amount of data while ensuring that data is retrievable in case of
node failure. The study of such systems, particularly the design of storage
codes over finite fields, assumes that the physical channel through which the
nodes communicate is error-free. This is not always the case, for example, in a
wireless storage system.
We study the probability that a subpacket is repaired incorrectly during node
repair in a distributed storage system, in which the nodes communicate over an
AWGN or Rayleigh fading channels. The asymptotic probability (as SNR increases)
that a node is repaired incorrectly is shown to be completely determined by the
repair locality of the DSS and the symbol error rate of the wireless channel.
Lastly, we propose some design criteria for physical layer coding in this
scenario, and use it to compute optimally rotated QAM constellations for use in
wireless distributed storage systems.Comment: To appear in ISITA 201
Repair Scheduling in Wireless Distributed Storage with D2D Communication
We consider distributed storage (DS) for a wireless network where mobile
devices arrive and depart according to a Poisson random process. Content is
stored in a number of mobile devices, using an erasure correcting code. When
requesting a piece of content, a user retrieves the content from the mobile
devices using device-to-device communication or, if not possible, from the base
station (BS), at the expense of a higher communication cost. We consider the
repair problem when a device that stores data leaves the network. In
particular, we introduce a repair scheduling where repair is performed (from
storage devices or the BS) periodically. We derive analytical expressions for
the overall communication cost of repair and download as a function of the
repair interval. We illustrate the analysis by giving results for maximum
distance separable codes and regenerating codes. Our results indicate that DS
can reduce the overall communication cost with respect to the case where
content is only downloaded from the BS, provided that repairs are performed
frequently enough. The required repair frequency depends on the code used for
storage and the network parameters. In particular, minimum bandwidth
regenerating codes require very frequent repairs, while maximum distance
separable codes give better performance if repair is performed less frequently.
We also show that instantaneous repair is not always optimal.Comment: To be presented at IEEE Information Theory Workshop (ITW) 2015, Jeju
Island, Korea, October 201
An Outline of Security in Wireless Sensor Networks: Threats, Countermeasures and Implementations
With the expansion of wireless sensor networks (WSNs), the need for securing
the data flow through these networks is increasing. These sensor networks allow
for easy-to-apply and flexible installations which have enabled them to be used
for numerous applications. Due to these properties, they face distinct
information security threats. Security of the data flowing through across
networks provides the researchers with an interesting and intriguing potential
for research. Design of these networks to ensure the protection of data faces
the constraints of limited power and processing resources. We provide the
basics of wireless sensor network security to help the researchers and
engineers in better understanding of this applications field. In this chapter,
we will provide the basics of information security with special emphasis on
WSNs. The chapter will also give an overview of the information security
requirements in these networks. Threats to the security of data in WSNs and
some of their counter measures are also presented
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