Aiman Ismail

Measurements and Analysis of Spectrum Occupancy in the Cellular and TV Bands

In this paper, we investigate spectrum occupancy focusing on cellular and TV broadcasting bands. Recently, TV band has attracted much attention due to the potential to exploit the available white space, if any, to improve spectrum utilization opportunistically. TV white space is a portion of spectrum in the UHF/VHF bands which is not utilized based on time and location. For the sake of comparison, measurements have also been conducted to investigate spectrum occupancy in cellular band, which is normally assumed to be fully utilized. The findings in this paper are important to provide insight of the actual spectrum utilization in the TV and cellular bands in Malaysia as compared to studies conducted in other countries.

Radio frequency radiation evaluation of transmitting devices in VHF/UHF band

This paper describes an evaluation of the radio frequency radiation (RFR) from transmitting devices in the VHF/UHF band. The RFR readings are then verified with the guidelines made by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) which was recommended by the International Telecommunication Union (ITU). The scope of this study is to gather and evaluate information on possible exposure of the general public at public accessible area around Klang Valley, Malaysia due to radio frequency radiation in the VHF/UHF band. The location was chosen based on highly populated areas and the distance from the TV and radio transmitters. A total of ten sites were chosen to be evaluated. Two types of measurements were conducted at each site, which are broadband and narrowband measurements. The narrowband measurements were carried out at the point where broadband measurement gives the highest reading. Data from a spectrum analyzer is then analyzed to determine the exposure level. Through analysis; it was found that the exposure level is well below the safety guidelines. Therefore, RFR in all ten sites conform to the ICNIRP guidelines.

Spectrum survey for reliable communications of cognitive radio based smart grid network

The smart grid (SG) system is expected to involve huge amount of data with different levels of priorities to different applications or users. The traditional grid which tend to deploy propriety networks with limited coverage and bandwidth, is not sufficient to support large scale SG network. Cognitive radio (CR) is a promising communication platform for SG network by utilizing potentially all available spectrum resources, subject to interference constraint. In order to develop a reliable communication framework for CR based SG network, thorough investigations on the current radio spectrum are required. This paper presents the spectrum utilization in Malaysia, specifically in the UHF/VHF bands, cellular (GSM 900, GSM 1800 and 3G), WiMAX, ISM and LTE band. The goal is to determine the potential spectrum that can be exploit by the CR users in the SG network. Measurements was conducted for 24 hours to quantify the average spectrum usage and the amount of available bandwidth. The findings in this paper are important to provide insight of actual spectrum utilization prior to developing a reliable communication platform for CR based SG network.

Electromagnetic assessment for mobile phone base stations at major cities in Malaysia

This paper describes a research carried out to study electromagnetic exposure emitted by mobile phone base stations in public areas at major cities in Malaysia, i.e. Kuala Lumpur and Johor Bahru. Two measurement methods, namely broadband and narrowband measurements were used for that purpose. The recorded power densities were then compared with the International Commission on Non-ionizing Radiation Protection (ICNIRP) guidelines. The measurements show that the electromagnetic exposures from mobile phone base stations are well below the ICNIRP limit. The highest recorded broadband measurement value was 2.17% of the worst case RF Maximum Permissible Exposure (MPE) value set by ICNIRP, which is 2 W/m2. For narrowband measurement, the highest total exposure ratio recorded was 0.3741% of the corresponding MPE.

Use of Geographic Information System (GIS) tools as network planning aid for antenna mounting in remote areas

This paper presents a network planning aid for choosing antenna mounting locations in remote area using Geographical Information System (GIS) tools. It is important to determine the right location and to decide the optimal network equipment for remote monitoring applications with challenging terrain. Prior to deploying any wireless network, this tool allows the field engineer to study the geographical condition of the target location. The result demonstrate that GIS tool can be utilized or guide the planner for deployment of antenna mountings in remote area.

Determining the inhibitor content of transformer insulating oil using UV-Vis spectroscopy

Monitoring and inspection of inhibitor content in transformer insulating oil has been a routine test for power utilities. Although new uninhibited transformer insulating oil contains naturally occurring inhibitors, these inhibitors could deplete over time during operation. Once the inhibitor depleted completely, the oil would start to deteriorate at a faster rate and eventually could lead to faults in transformer. The common method of determining the weight percentage of inhibitor in transformer oil is through Fourier Transform Infrared (FTIR) spectroscopy. However, this method is laboratory-based, which means oil sampling at site is necessary and the oil samples need to be transported to the laboratory. The necessity for oil sampling, coupled with the high cost of FTIR equipment have led to high maintenance cost. Therefore, this work investigated the possibility of using single wavelength or waveband optical detection for the determination of weight percentage of inhibitor in transformer oil using ultraviolet-visible-near infrared (UV-VIS-NIR) spectroscopy. Result of the work shows that the samples with inhibitor produced an absorbance peak at 1403nm. The peak absorbance of the spectral response is proportional to the weight percentage of inhibitor content that was measured using the conventional method, which is IEC 60666. An equation was derived to model the peak absorbance and weight percent of inhibitor content (%IC) of the oil and it was verified with additional oil sample with a known weight percent of Inhibitor content.

Site suitability analysis for landslide monitoring base station using GIS-based multicriteria evaluation technique

Landslide monitoring of power transmission towers in the rural areas is a challenging process especially if the slope is at a mountainous terrain and suspected to be insecure and risky. Identification of suitable locations for the landslide monitoring base station is one of the critical issues of network planning. Site suitability analysis has become unavoidable for delineating the appropriate site for planning initiatives, especially in the undulating terrain of the hills. It is important to determine the right location and to decide the optimal network equipment for remote monitoring applications. The study illustrates the use of geographic information system (GIS) and multicriteria evaluation (MCE) technique for selection of suitable sites for landslide monitoring base stations along the transmission tower line in Cameron Highland. Four criteria have been selected for site suitability analysis of the antenna base station (BS) which is tower distance, elevation, communication service coverage and slope. The generated thematic maps of these criteria were standardized using pairwise comparison matrix known as analytical hierarchy process (AHP). A weight for each criterion was generated by comparing them with each other according to their importance. With the help of these weights and criteria, the final site suitability map was prepared.

A new dynamic bandwidth allocation algorithm for fiber wireless network

Fiber Wireless (FiWi) provides a solution that combines gigabit passive optical network and Wi-Fi to provide huge capacity as well as mobility support. To manage the bandwidth in FiWi, a dynamic bandwidth allocation is proposed in this paper where it uses time division multiple access at the optical part and Carrier Sense Multiple Access with Collision Avoidance at the wireless part. Two methods are used for the algorithm, one using status reporting and the other is using non status reporting. It shows that both algorithms have their own advantage and disadvantage. The differences were found to be marginal though. For the status reporting, it has 4.6% higher bandwidth utilization than non status reporting and non status reporting has 5.24% lower delay compared to status reporting.

Electromagnetic spectrum survey of the environment in a locality in Kuala Lumpur, Malaysia

The electromagnetic spectrum in the environment is becoming a scarce resource with the emergence of a high number of wireless communications services Cognitive radio (CR) is viewed as a possible solution to the spectrum bottleneck which work in a premise that at an any given time and spatial region there are frequency bands that has no signal occupancy. The CR technique utilizes a temporarily unoccupied licensed band by allowing secondary users to exploit opportunistically the underutilized spectrum licensed to primary users without any harmful interference. Before investigating the technical and political implications of CR, it is necessary to know to what extent the licensed bands are temporally unoccupied. In this paper a spectrum occupancy measurements is conducted to study the utilization of RF spectrum in an environment. The measurements are performed on UHF TV, GSM900 and GSM1800 frequency bands in an urban area in Kuala Lumpur, Malaysia. The evaluation made is based on the power detection principle. From the measurements, the spectrum holes are identified. The obtained results show that the spectral usage is 7.37% for UHF TV band, 12.8% for GSM900 and 5.3% for GSM1800 band leading to the conclusion that a significant amount of spectrum is available for deployment of cognitive radio.

UV-Vis Spectroscopy: A New Approach for Assessing the Color Index of Transformer Insulating Oil

Monitoring the condition of transformer oil is considered to be one of the preventive maintenance measures and it is very critical in ensuring the safety as well as optimal performance of the equipment. Various oil properties and contents in oil can be monitored such as acidity, furanic compounds and color. The current method is used to determine the color index (CI) of transformer oil produces an error of 0.5 in measurement, has high risk of human handling error, additional expense such as sampling and transportations, and limited samples can be measured per day due to safety and health reasons. Therefore, this work proposes the determination of CI of transformer oil using ultraviolet-to-visible (UV-Vis) spectroscopy. Results show a good correlation between the CI of transformer oil and the absorbance spectral responses of oils from 300 nm to 700 nm. Modeled equations were developed to relate the CI of the oil with the cutoff wavelength and absorbance, and with the area under the curve from 360 nm to 600 nm. These equations were verified with another set of oil samples. The equation that describes the relationship between cutoff wavelength, absorbance and CI of the oil shows higher accuracy with root mean square error (RMSE) of 0.1961.