Nik Noordini Nik Abd Malik

Intelligent optimization of node coordination in Wireless Sensor Network

This paper presents a method which intelligently determines the optimum node coordination of sensor nodes topology. The topology is in linear array, aimed for beamforming in Wireless Sensor Networks (WSNs). The array is constructed in random sensor node deployment. The selected nodes should align similar to a uniform linear array (ULA) to minimize the position errors which will improve the beamforming performance (gain, transmission range and characteristics). Instead of utilizing random beamforming which needs a large number of sensor nodes to interact with each other and form a narrow radiation beam, the proposed approach is emphasized to only a number of sensor nodes which can construct a linear array. Beamforming technologies can increase the system performance, increase the transmission range and control the directionality of the reception or transmission of a signal. The proposed work utilizes beamforming technique by using ULA to establish a communication link in a WSN.

Circular Collaborative Beamforming for Improved Radiation Beampattern in WSN

This paper presents a novel collaborative beamforming (CB) method of wireless sensor network (WSN) by organizing sensor node location in a circular arrangement. Appropriate selection of active CB nodes and cluster is needed each time to perform CB. The nodes are modeled in circular array location in order to consider it as a circular antenna array (CAA). This newly proposed circular collaborative beamforming (CCB) is further presented to solve two different objectives, that is, sidelobe level (SLL) suppression and first null beamwidth (FNBW). Analyses obtained are compared to those from previous work. The findings demonstrate a better CB performance of intelligent capability, and the difference is shown in normalized power characteristic.

Performance Analysis of Bootstrap Transimpedance Amplifier For Large Windows Optical Wireless Receiver

Due to optical wireless link power budget considerations, the receiver is required to have a large collection area. One of the main noise mechanisms in wideband preamplifiers employing large area detectors is the noise due to the low pass filter formed by the detector capacitance and the input impedance to the preamplifier. Typical large photodetection area commercial detectors has capacitance are around 100-300 pF compared to 50pF in fiber link. Hence, techniques to reduce the effective detector capacitance are required in order to achieve a low noise and wide bandwidth design. In this paper analysis on the bootstrap transimpedance amplifier (BTA) for input capacitance reduction is reported. This technique offers the usual advantages of the transimpedance amplifier together with an effective capacitance reduction technique for optical wireless detector

Reconfigurable harmonic suppressed fractal dipole antenna

A small active frequency reconfigurable Koch dipole antenna is presented with harmonic suppression capability. Open circuit stub is coupled to the antennas terminal and the tapered balun. Three pairs of diodes are used for tuning purposes. The first prototype can be tuned at 722.7 MHz, 809 MHz, 1050.5 MHz, and 2361.5 MHz, respectively. At the same time the antenna can suppress undesired harmful harmonic frequencies of 2.4 GHz, 2.75 GHz, and 2.85 GHz. Simulation and measurement results obtained are in good agreement, which have confirmed the design concept.

Optimization of adaptive linear sensor node array in Wireless Sensor Network

This paper presents a method of optimizing sensor node coordination in order to reassign the nodes in linear array arrangement to form a linear antenna array. This linear sensor node array (LSNA) is constructed within random sensor node deployment. The LSNA should be optimized as closely comparable as a conventional uniform linear array (ULA) to minimize the beamforming performance errors. Beamforming has been introduced in Wireless Sensor Networks (WSNs) in order to increase the transmission range of individual sensor nodes. The performance of the two methods: LSNA and ULA are compared in adaptive manner. The results of the constructed adaptive LSNA demonstrated an excellent agreement compared to the conventional ULA.

Peak to Average Power Ratio (PAPR) Reduction in OFDM System

Orthogonal frequency division multiplexing (OFDM) is a special form of multi-carrier modulation which is robust against the multipath effect, intersymbol interference (ISI) and high spectral efficiency. However, peak to average power ratio (PAPR) is a major drawback in the system since this leads to the distortion problem in the linear devices such as the power amplifier (PA). Thus, the PAs require a backoff which is approximately equal to the PAPR for distortionless transmission. This decreases the efficiency for amplifiers. Hence, reducing the PAPR is the main focus of this paper. One of the available PAPR solutions is clipping. In the technique, the efficiency does not depend on the number of carriers. This paper investigates the effectiveness of the clipping technique by focusing on the performance of PAPR value with different values of clipping ratios (CRs) and the relationship between PAPR value and bit error rate (BER)

Conceptual implementation to access the extend of influence of lightning electromagnetic radiation on mobile radio communication

In this paper, the research of interference to the private mobile radio (PMR) due to lightning electromagnetic field has been done. The conceptual implementation to access the extend of influence of lightning electromagnetic radiation (LEMR) on mobile radio communication. Wireless data has been transmitted through a pair of Motorola Talkabout T5420 walkie-talkie with 14 channels and 38 codes and operates on 14 UHF FRS frequencies. Two types of induced interference has been arranged which are high voltage and high current experiments using impulse voltage generator (IVG) and recloser test set (RTS) in high voltage laboratory, Institute of High Voltage and High Current, UTM.

Performance comparison of AODV and HWMP routing protocols in wireless mesh networks

Wireless mesh networks (WMNs) have gain attention from researchers in telecommunication engineering field due to its potential to provide low cost internet broadband access, wireless local area network coverage and network connectivity for stationary or mobile host. This network consists of multiple wireless routers that are used to relay each others packet in multi-hop fashion. Hence, routing protocol plays an important part in maintaining the connectivity of WMNs. In this paper, two routing protocols, Ad hoc On-demand Distance Vector (AODV) and Hybrid Wireless Mesh Routing Protocol (HWMP) are compared in terms of their performance in WMNs. A random wireless mesh topology with router nodes is modelled in Network Simulator 3 by assuming that the router nodes are connected to its client nodes. The simulations are performed in two different topologies with varied number of nodes. Three merits are taken into account when making the comparisons which are packet delivery fraction, throughput, and end-to-end delay. The simulation results demonstrate that HWMP is more suitable to be applied in WMNs compared to AODV.

Broadband microstrip-to-parallel strip transition balun with reduced size

A tapered balun of broadband microstrip-to-parallel strip transition using triangular structure with linear transition for a dipole antenna is proposed. The original balun consists of linear profile with the size of one quarter wavelength for both the height and width. By studying the current distributions at balun surface, it can be reduced to 25%, 50%, and 75% from the original size. Measured results based on return loss and insertion loss for all baluns were found to be better than -10 dB and -3 dB, respectively, from 400 MHz to 3.5 GHz.

A survey of clustering algorithms for cognitive radio ad hoc networks

The dynamic spectrum nature of cognitive radio challenges the connectivity and the stability of cognitive radio ad hoc networks (CRAHNs). Clustering is considered as an appropriate technique to overcome these issues. Various algorithms for clustering formation in CRAHN have been proposed, in which different system models and metrics are considered. This paper introduces an extensive survey of the most important published algorithms. This survey classifies the proposed algorithms based on their objectives. Moreover, it presents a detailed description of their techniques, evaluations of their performance, and discussion of the features and shortcomings of each algorithm. Furthermore, it provides and discusses the open issues for future research.