Mobile Communication Base Station Research Articles

Small Antennas: Miniaturization Techniques and Applications

The paper presents research results in the field of small antennas obtained at the Department of Wireless Communications, Faculty of Electrical Engineering and Computing, University of Zagreb. A study comparing the application of several miniaturization techniques on a shorted patch antenna is presented. Single and dual band shorted patch antennas with notches and/or slot are introduced. A PIFA designed for application in mobile GSM terminals is described. The application of stacked shorted patches as array elements for a mobile communication base station as well as for electromagnetic field sensor is presented. The design of single and dual band folded monopoles is described. Prototypes of the presented antennas have been manufactured and their characteristics were verified by measurements.

직렬 급전된 두 개의 다이폴 배열 안테나의 대역폭 향상

본 논문에서는 이동 통신용 기지국 안테나로 사용할 수 있는 직렬 급전된 두 개의 다이폴 배열(STDA) 안테나의 대역폭 향상에 관해 연구하였다. 제안된 STDA 안테나는 두 개의 서로 다른 길이의 스트립 다이폴 안테나가 코플래너스트립라인 급전선으로 바로 연결되어 있다. 두 다이폴 사이의 간격과 두 번째 다이폴의 길이를 조정함으로써 대역폭을 증가시킬 수 있다. 또한, 급전부를 최소화하기 위해 단락이 종단된 마이크로스트립라인과 슬롯라인으로 구성된 내장 밸런을 사용하였으며, 급전위치를 조정하여 광대역 임피던스 정합을 얻을 수 있었다. 제안된 구조로 현재 운용되는 이동 통신 주파수를 모두 포함하는 1.75-2.7 GHz 대역에서 이득이 5dBi 이상인 안테나를 설계하고 FR4 기판(비유전율 4.4, 두께 0.8 mm)상에 제작하여 특성을 실험하였다. 제작된 안테나는 VSWR<2 기준으로 임피던스 대역폭이 49%(1.7-2.8 GHz)이고 5.5 dBi 이상의 이득을 가지며, 12 dB 이상의 전후방비를 가진다. In this paper, bandwidth improvement of a series-fed two dipole array(STDA) antenna applicable for mobile communication base station antennas is studied. The proposed STDA antenna consists of two strip dipole antennas with different lengths which are connected directly trough a coplanar stripline(CPS). By adjusting the spacing between the two dipoles and the length of the second dipole, the bandwidth of the STDA can be enhanced. In addition, an integrated balun composed of a short-circuited microstrip line and a slot line is utilized to minimize the area required for a feeding part, and a broadband impedance matching is obtained by adjusting the feeding point. Based on the proposed antenna structure, an STDA antenna covering the frequency band ranging from 1.75 GHz to 2.7 GHz, which includes almost all the existing mobile communication frequency bands, with more than 5 dBi gain is designed and fabricated on an FR4 substrate with dielectric constant of 4.4 and thickness of 1.6mm, and experimentally tested. The fabricated antenna shows impedance bandwidth of 49%(1.7-2.8 GHz) for VSWR<2, a gain higher than 5.5 dBi, and a front-back ratio better than 12 dB.

다중 대역용 차세대 이동통신 기지국 시스템의 전력 및 탄소배출량 절감효과 분석

본 논문은 다중 대역에서 동작하는 안테나를 장착한 차세대 이동통신 기지국 시스템의 도입 가능성 분석을 위해 종래의 기지국 시스템과 케이블 손실전력을 고려한 차세대 기지국 시스템의 전력 손실 및 탄소 절감효과를 분석하였다. 차세대 기지국 시스템은 옥외에 무선처리부를 설치하고, 옥내의 기저대역처리부는 광케이블로 연결하여 종래의 기지국에서 케이블로 인해 발생하는 전력손실을 없애는 구조이다. 본 연구 결과 종래의 기지국과 비교하여 동일한 서비스 커버리지 확보가 가능하고, 케이블 전력손실이 5 dB 줄어든 차세대 기지국 시스템을 도입할 경우 CDMA 20W, WCDMA 30W, WiBro 10W 기지국에서 소모하는 전력량은 연간 155,078 MWh에서 49,038 MWh로 감소시킬 수 있으며, 탄소배출량 또한 65,878 <TEX>$tCO_2$</TEX>에서 20,832 <TEX>$tCO_2$</TEX>로 절감됨을 확인하였다. 따라서 차세대 기지국 시스템은 그린 IT 기술로 이용 가능할 것으로 고찰되었다. In this paper, we present the analysis of the characteristics of advanced mobile communication base station with multi-band about power loss, power efficiency and carbon reduction considering cable power loss. The advanced mobile base station system is installed on the outdoor for Antenna and RF part, and then the power loss is reduced because the fiber optic cable is used between RF part and baseband part. If the cable power loss is reduced by 5 dB replacing an entire the advanced base station systems, annual power consumption is reduced total 49,038 MWh in the CDMA 20W, WCDMA 30W, WiBro 10W systems. Furthermore the advanced base station system of annual <TEX>$CO_2$</TEX> emission is 20,832 <TEX>$tCO_2$</TEX> compare to 65,878 <TEX>$tCO_2$</TEX>. Therefore the advanced base system is confirmed considering green IT technology for the advanced mobile communication base station.

Sampling Jitter Effect on a Reconfigurable Digital IF Transceiver to WiMAX and HSDPA

This paper outlines the time jitter effect of a sampling clock on a software-defined radio technology-based digital intermediate frequency (IF) transceiver for a mobile communication base station. The implemented digital IF transceiver is reconfigurable to high-speed data packet access (HSDPA) and three bandwidth profiles: 1.75 MHz, 3.5 MHz, and 7 MHz, each incorporating the IEEE 802.16d worldwide interoperability for microwave access (WiMAX) standard. This paper examines the relationship between the signal-to-noise ratio (SNR) characteristics of a digital IF transceiver with an under-sampling scheme and the sampling jitter effect on a multichannel orthogonal frequency-division multiplexing (OFDM) signal. The simulation and experimental results show that the SNR of the OFDM system with narrower band profiles is more susceptible to sampling clock jitter than systems with relatively wider band profiles. Further, for systems with a comparable bandwidth, HSDPA outperforms WiMAX, for example, a 5 dB error vector magnitude improvement at 15 picoseconds time jitter for a bandwidth of WiMAX 3.5 MHz profile.

The impact of specific information provision on base station siting preferences

When it comes to the new siting of a mobile communication base station in one’s neighbourhood, some people react with rejection because they fear health consequences from the emitted high‐frequency radiation. Most people would prefer to site base stations outside residential areas, but from a public health perspective, this may result in even more radiation for the phoning population. Therefore, authorities are interested in improving the current base station siting processes. The question arises whether specific knowledge enhancement would influence base station siting preferences or whether affective or emotional components (due to the scientific uncertainties involved) would overrule the influence of such attempts. To answer this question, an experimental study with a convenience sample of Swiss citizens (N = 228) was conducted. Participants were confronted with one of three texts: a neutral text (control group), an information booklet about mobile communication and an emotionally charged newspaper article that reported a conflict about the siting of a new base station. After reading the text, participants filled out a questionnaire about their perception of mobile communication and their base station siting preferences. Reading the information booklet increased participants’ knowledge and led to some perceptual changes of base stations and mobile phones. Importantly, participants reading the booklet were able to transfer their knowledge to a base station siting task and found locations that would emit less radiation for the phoning population. Implications and limitations of these results are discussed.

Stimulation of Haemopoetic Activity in Bone Marrow and Deformation of Red Blood Cells in Albino Mice, &lt;i&gt;Mus musculus&lt;/i&gt; Exposed to Radiations from GSM Base Stations

The levels of radiofrequency radiations around two global systems for mobile communication (GSM) base stations located around a residential quarter and workplace complex were measured. The effects of the radiofrequency radiations on albino mice placed in exposure cages and located around the base stations over a six months period were investigated. The levels of radiofrequency (RF) radiations around the base stations were found to range between 383 mV/m to 730 mV/m compared to 59 mV/m in control stations. In the exposed mice, a pattern of pancytosis was observed and significant increases were observed in the Packed Cell Volume (PCV), White Cell Count (WBC), Platelet count (PLT) and Red Cell Count (RCC) throughout the period of exposure in both stations when compared with control values. No significant (p>0.05) differences were observed in these values when both stations were compared. After 90 days of exposure, marginal increases occurred in the mean cell volume of exposed mice at station 1 and 2 (53.1±3.6fl Vs 55.9±1.8fl and 57.9±0.25fl respectively), with the mean cell haemoglobin concentration showing significant reduction after 180 days of exposure at station 2 (27.9±2.4g/dl Vs 25.7±0.29g/dl; p

Synthesis of Star-Junction Multiplexers

This paper illustrates a general approach to the synthesis of microwave multiplexers (RF combiners) presenting a star-junction topology (with a resonating junction). The channel filters composing the multiplexer can be arbitrarily specified; in particular, the attenuation characteristic may include transmission zeros (imaginary and/or complex). The synthesis procedure, developed in a low-pass frequency domain (suitably defined), is based on an iterative algorithm which evaluates the characteristic polynomials of both the overall multiplexer and the composing filters. Using these latter polynomials, the normalized coupling matrices of the filters can be computed using one of the methods available in the literature and the dimensioning of the channel filters is carried out through the usual de-normalized parameters (coupling coefficients and external <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> ). The detailed design steps illustrating the synthesis of a triplexer for base stations of mobile communications are presented. The designed device was then built, and the comparison between measurements and simulations has validated the new synthesis approach.

A numerical coefficient for evaluation of the environmental impact of electromagnetic fields radiated by base stations for mobile communications

The aim of this study is the development of an Electromagnetic Environmental Impact Factor (EEIF). This is a global parameter that represents the level of electromagnetic impact on a specific area due to the presence of radiating systems, such as base station (BS) antennas for mobile communications. The numerical value of the EEIF depends only on the electromagnetic field intensity, a well-defined physical quantity that can easily be measured or computed. The paper describes the significant parameters of the field distribution adopted to evaluate the EEIF, and the assumptions used to develop a proper scale of values. Finally, some examples of application of the EEIF method are analyzed for real situations in a typical urban area.

Level of Radiofrequency (RF) Radiations from GSM Base Stations and its Biological Effects on Albino Mice, &lt;i&gt;Mus musculus&lt;/i&gt;

Levels of radiofrequency radiations around two global systems for mobile communication (GSM) base stations located in the vicinity of a residential quarter and workplace complex were measured. The effects of the radiofrequency radiations on albino mice placed in exposure cages and located around the base stations over a six months period were carried out. The levels of radiofrequency (RF) radiations around the base stations were found to be between 488.51mV/m to 625.49mV/m compared to 59 mV/m in control stations. The results of the weight change experiment showed that over the 180 days of observation, there was weight gain in the exposed and control mice groups. Statistical comparisons of mean weight changes between exposed mice and control mice showed that there were no significant (P>0.05) differences between the weight of the test animals. The hematological studies revealed an elevation of white blood cell (WBC) counts in mice exposed to RF radiations compared to control group. There was however no significant (P>0.05) difference between the red blood cell counts in the exposed and control mice. There was also no significant (P>0.05) difference in the hemoglobin and glucose levels in the blood of both exposed and control mice groups. The red blood cells in exposed mice were however found to contain a higher number of macrocytes, poikilocytes, polychromatic cells and fewer target cells than the control mice. Histological studies of the heart and kidney of exposed mice showed only slight tissues deformities in kidneys of exposed mice compared to control. The relevance of these findings in setting radiofrequency radiation exposure guidelines and the need for more studies with widely varying biological parameters is very necessary as Nigeria leaps further into the communication age.

이동 통신용 기지국 환경에서 전자파 강도 노출량 측정 결과 분석

This paper measured EMF strength of the duty measurement radio station(77 station) and the non-duty measurement radio station(41 station) of mobile communication base station in Jeonbuk region. As the result of measurement, it generally reveals that EMF is highly low level compare to the human protection guideline. And It is regarded as level that the national people who live close to the mobile communication base station don`t have to worry about electromagnetic wave. This paper provides comparative analyses categorized by the duty measurement station and the non-duty measurement station. The results reveals that the average value and the maximum value of the non-duty measurement station preferably was higher than all the duty measurement station. It is thought that the EMF exposure strength of the national people is caused by approach of station antenna rather than antenna power. Consequently this paper suggests that standard of the antenna power(exceed 30 W), standard of antenna height(exceed 10 m) specified by Radio Regulation Act enforcement ordinance, legal basis for mobile communication base station have to be changed.

A model for radiofrequency electromagnetic field predictions at outdoor and indoor locations in the context of epidemiological research

We present a geospatial model to predict the radiofrequency electromagnetic field from fixed site transmitters for use in epidemiological exposure assessment. The proposed model extends an existing model toward the prediction of indoor exposure, that is, at the homes of potential study participants. The model is based on accurate operation parameters of all stationary transmitters of mobile communication base stations, and radio broadcast and television transmitters for an extended urban and suburban region in the Basel area (Switzerland). The model was evaluated by calculating Spearman rank correlations and weighted Cohen's kappa (kappa) statistics between the model predictions and measurements obtained at street level, in the homes of volunteers, and in front of the windows of these homes. The correlation coefficients of the numerical predictions with street level measurements were 0.64, with indoor measurements 0.66, and with window measurements 0.67. The kappa coefficients were 0.48 (95%-confidence interval: 0.35-0.61) for street level measurements, 0.44 (95%-CI: 0.32-0.57) for indoor measurements, and 0.53 (95%-CI: 0.42-0.65) for window measurements. Although the modeling of shielding effects by walls and roofs requires considerable simplifications of a complex environment, we found a comparable accuracy of the model for indoor and outdoor points.

Preliminary Study on the Induction of Sperm Head Abnormalities in Mice, Mus musculus, Exposed to Radiofrequency Radiations from Global System for Mobile Communication Base Stations

The exposure of male mice to radiofrequency radiations from mobile phone (GSM) base stations at a workplace complex and residential quarters caused 39.78 and 46.03%, respectively, in sperm head abnormalities compared to 2.13% in control group. Statistical analysis of sperm head abnormality score showed that there was a significant (p < 0.05) difference in occurrence of sperm head abnormalities in test animals. The major abnormalities observed were knobbed hook, pin-head and banana-shaped sperm head. The occurrence of the sperm head abnormalities was also found to be dose dependent. The implications of the observed increase occurrence of sperm head abnormalities on the reproductive health of humans living in close proximity to GSM base stations were discussed.

The generation of simple compliance boundaries for mobile communication base station antennas using formulae for SAR estimation

In this paper, a procedure is proposed for generating simple and practical compliance boundaries for mobile communication base station antennas. The procedure is based on a set of formulae for estimating the specific absorption rate (SAR) in certain directions around a class of common base station antennas. The formulae, given for both whole-body and localized SAR, require as input the frequency, the transmitted power and knowledge of antenna-related parameters such as dimensions, directivity and half-power beamwidths. With knowledge of the SAR in three key directions it is demonstrated how simple and practical compliance boundaries can be generated outside of which the exposure levels do not exceed certain limit values. The conservativeness of the proposed procedure is discussed based on results from numerical radio frequency (RF) exposure simulations with human body phantoms from the recently developed Virtual Family.

전후방비가 개선된 Cavity-Backed 마이크로스트립 다이폴 배열 안테나 설계

In this paper, a TRS band(Trunked Radio System: ) array antenna has a good front-to-back ratio characteristics for the mobile communication base station is proposed. The proposed array antenna is composed of the radiated elements which are the microstrip dipole antennas with the cavity-backed reflector. For the validity of the proposed antenna, the array antenna is designed, fabricated, and its radiation characteristics are measured. As a result of measurements, the antenna gain is over 13.3 dBi and the front-to-back ratio is over 40 dB at the useable frequency band. We confirm that the designed antenna can be used as the mobile communication base station antenna with the excellent back lobe characteristics.

Occupational Exposure at Mobile Communication Base Station Antenna Sites

Occupational Exposure at Mobile Communication Base Station Antenna Sites

Performance optimization of a hybrid cooler combining vapor compression and natural circulation cycles

A hybrid cooler combining vapor compression and natural circulation cycles was developed for the cooling of telecommunication equipment in the cabinet-type base station of mobile communication. This hybrid cooler normally operates in the vapor compression mode at high ambient temperatures, but works in the natural circulation mode at low ambient temperatures by the thermosiphon principle. The performance of the hybrid cooler was measured according to the refrigerant charge, outdoor temperature, heat exchanger geometry, and the vertical distance between the condenser and the evaporator. The optimum design conditions for these variables are discussed with respect to the performance of the hybrid cooler in both operating modes. The difference in the optimum refrigerant charge between the two operating modes was solved by installing a liquid receiver. The temperature difference between the indoor and ambient air was introduced as a control parameter for use when changing the operating mode.

Informing the public about information and participation strategies in the siting of mobile communication base stations: an experimental study

Informing the public and ensuring their participation are considered important characteristics for a successful siting of mobile communication base stations. However, there is only sparse empirical evidence for this presumption. In particular, nothing is known about whether informing people that a siting decision is based on public information and participation activities has any positive effects. The experimental study presented here investigated in a hypothetical evaluation situation whether being informed about different information and participation strategies will have an effect on: (1) risk perception, (2) the acceptance of a site, (3) trust in the safety of the mobile communication base station, (4) the chances for conflict resolution and for conflict avoidance, as well as (5) the transparency of the siting process and (6) the consideration of public concerns in the decision. The results indicate that being informed about information strategies exerts no influence on the variables considered here. However, being informed about participation strategies yields differentiated results. No effects were found on the variables ‘risk perception,’ ‘acceptance of the siting decision’ and ‘trust in the safety of the mobile communication base station’ as well as on ‘conflict avoidance.’ Statistically significant effects were found for the variables ‘transparency of the siting process,’ ‘consideration of the concerns of the local residents’ as well as ‘resolution of existing conflicts in the siting of mobile communication base stations.’ These results suggest that more information and participation does not automatically translate into higher quality or greater acceptance of the base station siting process.

Break-even analysis and size optimization of a PV/wind hybrid energy conversion system with battery storage – A case study

This paper aims to show an optimum sizing procedure of autonomous PV/wind hybrid energy system with battery storage and a break-even analysis of this system and extension of transmission line. We use net present value (NPV) method for the comparison of autonomous hybrid energy system and extension of transmission line cases. The case study is completed for the satisfaction of the electricity consumption of global system for mobile communication base station (GSM) at Izmir Institute of Technology Campus Area, Urla, Izmir, Turkey. First, we optimize the PV/wind energy system using response surface methodology (RSM) which is a collection of statistical and mathematical methods relying on optimization of response surface with design parameters. As a result of RSM, the optimum PV area, wind turbine rotor swept area, and battery capacity are obtained as 3.95 m 2, 29.4 m 2, 31.92 kW h, respectively. These results led to $37,033.9 hybrid energy system cost. Second, break-even analysis is done to be able to decide the optimum distance where the hybrid energy system is more economical than the extension of the transmission line. The result shows that, if the distance between national electricity network and the GSM base station location where the hybrid energy system is assumed to be installed is at a distance more than 4817 m, the installation of hybrid energy system is more economical than the electricity network.

On the Estimation of SAR and Compliance Distance Related to RF Exposure From Mobile Communication Base Station Antennas

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, maximum specific absorption rate (SAR) estimation formulas for RF main beam exposure from mobile communication base station antennas are proposed. The formulas, given for both whole-body SAR and localized SAR, are heuristic in nature and valid for a class of common base station antennas. The formulas were developed based on a number of physical observations and are supported by results from an extensive literature survey together with supplementary measurements and numerical simulations of typical exposure situations. Using exposure limits, the proposed SAR estimation formulas can be converted to formulas for estimating compliance distance. </para>

Electromagnetic Assessment on Human Safety of Mobile Communication Base Stations at University of Macau

Assessment of the electromagnetic exposure due to the mobile communication base station at University of Macau is presented by two testing scenarios. The first scenario about 20 in-situ measurements and the maximum E-field strength was 2.46 V/m that well below the threshold and compliant to the safety guideline. The second scenario investigates on the distance effect of exposure due to the base station and it is found that the field strength decays by 0.12 dB/m. Thus, low radiation level estimated at the university when compared with the measured values.