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Communication Coverage
in Wireless
Passive Sensor Networks

System lifetime of wireless sensor networks (WSN) is inversely proportional to the energy consumed by critically energy-constrained sensor nodes during RF transmission.
Hence, wireless passive sensor networks (WPSN) designed to operate using MB do not have the lifetime constraints of conventional WSN.
However, the communication performance of WPSN is directly related to the RF coverage provided over the field the passive sensor nodes are deployed.

INTRODUCTION


WIRELESS sensor networks (WSN) are, in general, composed of low-cost, low-power sensor nodes which can only be equipped with a limited power source, i.e., a battery.
With MB approach, a passive sensor node transmits its data simply by modulating the incident signal from an RF source by switching its antenna impedance.
Therefore, the transmitter is basically an antenna impedance switching circuitry, and WPSN is free of the lifetime constraint of conventional WSN.
The main focus of this paper is to investigate the communication coverage problem in WPSN.
WPSN MODEL


The source of energy is an RF power source which is assumed to have unlimited power.
The source transmits RF power to run the passive nodes, and it transmits and receives information from WPSN nodes simultaneously.
A typical WPSN node hardware is represented in Fig.
In the WPSN node, however, the power generator, which is an RFto-DC converter , is an inherent part of the power unit and is the unique power source of the sensor node.
Required power is obtained from the incident RF signal inducing a voltage on the receiver WPSN node.