Smart and Reconfigurable Antenna Applications in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are a prominent technology with diverse applications. Considerable amount of research effort has been devoted to energy minimization of limited power resources and reliable communication between the nodes and the gateway. Most of these studies rely on the software/algorithm improvement of WSNs, but there is definitely lack of hardware devoted research and its implementation on the network. This special issue aims to bridge this gap by exploiting application of proven technologies to WSNs to overcome the disadvantages of WSNs.

The smart antenna system (SAS) is one of the critical technologies where traditional communication systems such as cellular, personal communication systems have experienced great benefits. For the application of SAS in WSNs, adaptive and/or reconfigurable antenna structures play a key role in the radiation pattern and polarization of the node antenna. One paper addresses a novel node antenna where the polarization of the antenna can be reconfigured among all principal polarizations (LP, VP, RHCP, and LHCP) by means of control switches whose states can be controlled by a microcontroller. Such adaptive antenna systems are crucial in multipath fading environments.

Another paper studies the field performance of seismic sensors for intruder detection. Seismic sensors were integrated into a WSN where the critical data such as alarm conditions were transferred to the wireless network. Field performance of such applications is important for recognizing the shortcomings of the WSN in a real operating environment.

One of the papers addresses a memory efficient algorithm for intruder detection application of WSNs. Because the system operated in real time, the efficiency, accuracy, and reliability of the detection and classification algorithm played a vital role and the capabilities of the proposed algorithm were tested to full extent.

There is a paper that addresses the capabilities of reconfigurable antennas that can be used to devise an intrusion detection scheme which operates at the physical layer. The performance of the proposed scheme was quantified through field measurements taken in an indoor environment at the 802.11 frequency band.

One paper discusses the hardware issues such as noise, matched filtering, and amplification of small signals that were obtained through seismic sensors. Such sensors are abundantly used for outdoor intruder detection but there is little information in open literature about the design and realization of practical sensors in a limited power application of WSNs.

Another paper presents a novel collaborative beamforming (CB) method for WSNs by organizing sensor node location in a circular arrangement. The nodes were modeled in circular array location to consider it as a circular antenna array. This newly proposed circular collaborative beamforming was further investigated to solve two different objectives: sidelobe level suppression and first null beamwidth improvement.

One of the papers discusses the design of a reconfigurable antenna that can be fine-tuned to address future communication systems. The design consisted of a capacitively loaded patch antenna for smartphone platforms. It was shown that a narrowband antenna could be fine-tuned over the range of 700 MHz–960 MHz. Distribution of the tuning capacitance was also investigated and improvement in the antenna radiation efficiency was observed.