The demand for economical wireless sensor nodes have been increased due to advancement in processor, memory and wireless communication techniques. To give the on time and fast response for different actions, wireless sensor nodes work together in cooperation with each other. The most important requirement to maintain the co-ordination among different nodes during execution of an application is perfect time synchronization between them. Message packets are used for time synchronization in wireless sensor networks but transmission of these packets require significant amount of energy which is supplied by wireless sensor nodes. As these sensor nodes have limited battery capacity, usage of large number of packets has a negative impact upon their lifetime. So, to reduce the number of message packets required for the time synchronization in wireless sensor networks, we have used Optimal Performance Reference Broadcast Synchronization (OPRBS). This protocol performs synchronization with ranging i.e. select a particular range of broadcast according to transmission power of sensor nodes. With this decrease in the message packets for transmission, the convergence time among wireless sensor nodes is reduced and the lifetime of wireless sensor nodes is also extended as much as the amount of saved battery energy.

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GPS is commonly used for navigation. But Location estimation in indoor environments is not possible using GPS, as GPS signals cannot work in indoor environment. In indoor localization there is a huge impact of multipath parameters like shadowing, reflection, refraction, diffraction phenomena which have an impact on the position estimation which leads to inaccurate localization. Large number of Access Points (APs) equipped with single antenna could receive enough Receive Signal Strength (RSS) information that gives information about signal characteristics of the target area. But this results in a large cost of deployment. Various localization methods available are: TDOA, TOA, AOA, Location Finger Printing, GPS and RSSI.However in all these approaches the localization depends either on distance or on angle or on time only. In this paper the hybrid mechanism of range and angle measurements is considered. This proposed mechanism will provide an indoor positioning solution using the smart antenna architecture to increase the location estimation accuracy using mode of RSSI values followed by adaptive filtering.

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In this study, carbon black (CB) powder-loaded polyurethane (PU) composites (CB–PU composites) were prepared by melt mixing method with different volume percentages (45, 50, 55, 58 and 61 vol.%) of CB in the PU matrix. The prepared CB–PU composites had been further studied for surface morphology using the field-emission scanning electron microscopy (FESEM) technique. Dielectric properties in terms of real permittivity ([Formula: see text] and imaginary permittivity ([Formula: see text] of the fabricated composites were computed using an Agilent E8364B vector network analyzer in the frequency range of 8–12 GHz ([Formula: see text]-band). Dielectric loss factor of the prepared CB–PU composites was computed in terms of the dielectric loss tangent (tan [Formula: see text] = [Formula: see text]/[Formula: see text]. Microwave absorbing properties were appraised in terms of the reflection loss (RL) which in turn was calculated for varying thicknesses of the prepared composites from the measured real and imaginary permittivity data. The minimum RL was observed as −20.10 dB for the absorber with a thickness of 2.2 mm and the bandwidth achieved was 1.92 GHz for RL [Formula: see text]10 dB. Based on the above results these CB–PU composites have potential use as effective microwave absorbers in 8–12-GHz ([Formula: see text]-band) frequency range.