29-10-2010, 03:24 PM
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RADIO TOMOGRAPHIC IMAGING
Submitted by
STEFFI KOSHY
(Reg No: 07412058)
S.H.M. ENGINEERING COLLEGE, KADAKKAL
under University of Kerala
INTRODUCTION
When an object moves into the area of a wireless network, links which pass through that object will experience shadowing losses. This paper explores in detail the use of shadowing losses on links between many pairs of nodes in a wireless network to image the attenuation of objects within the network area. We refer to this problem as radio tomographic imaging (RTI), as depicted in Fig. 1. 1
Fig. 1.1: An illustration of RTI network.
Radio tomography draws from the concepts of two well known and widely used types of imaging systems. First, radar systems transmit RF probes and receive echoes caused by the objects in an environment. A delay between transmission and reception indicates a distance to a scatterer. Phased array radars also compute an angle of bearing. Such systems image an object in space based on reflection and scattering. Second, computed tomography (CT) methods in medical and geophysical imaging systems use signal measurements along many different paths through a medium. The measurements along the paths are used to compute an estimate of the spatial field of the transmission parameters throughout the medium. RTI is also a transmission-based imaging method which measures signal strengths on many different paths through a medium, but similar to radar systems, it does so at radio frequencies.
