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Overview of International guidelines concerning Human exposure to RF radiation From GSM Base Stations Eng. Nasser Al-Nasser Communications and Information Technology Commission Kingdom of Saudi Arabia . Content. Introduction Electromagnetic Waves Basics GSM Technology

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  1. Overview of International guidelines concerning Human exposure to RF radiationFrom GSM Base StationsEng. Nasser Al-NasserCommunications and Information Technology CommissionKingdom of Saudi Arabia

  2. Content • Introduction • Electromagnetic Waves Basics • GSM Technology • Effect of Radiations on Humans • International Bodies Guidelines • International bodies Findings and Recommendations

  3. Introduction • The presence of GSM electromagnetic fields in the environment due to cellular phones and base stations have become an essential part of modern society causing also an increasing public concern of possible adverse health effects. • There are some published reports in the scientific literature concerning possible biological effects resulting from human exposure to RF energy radiated from GSM base stations. • In this presentation, we will concisely present parts of GSM radio aspects in addition to briefly going over some guidelines recommended by the international bodies, concerning RF exposure.

  4. Electromagnetic Waves Basics • Electromagnetic Waves Electromagnetic (EM) waves are waves of electric and magnetic fields propagating orthogonally to each other through space. Source:http://www.stkate.edu

  5. Electromagnetic Waves Basics (cont’) • EM waves are generated by the movement of electric charges in a conductive metal object or antenna. • EM waves propagate through space at the velocity of light. • EM waves are characterized by a wavelength and frequency. • Wavelength (λ) is the distance covered by one complete cycle. It is expressed in meter. • Frequency is the number of electromagnetic waves passing a given point in one second. It is expressed in hertz (Hz).

  6. Electromagnetic Waves Basics (cont’) • Electromagnetic Spectrum Source: http://www.fcc.gov

  7. Electromagnetic Waves Basics (cont’) • Radiofrequency (RF) • Radiofrequency energy includes waves with frequencies varying from about 300 Hz up to 300 GHz. • Radiofrequency is used for radio transmission. • The most common usage of RF frequency is for telecommunications, broadcasting, wireless phones and satellite communications.

  8. Electromagnetic Waves Basics (cont’) • The power of the RF signal decreases as a function of distance between the transmitter and the receiver.

  9. Electromagnetic Waves Basics (cont’) • The higher the frequency of the signal the greater the attenuation. • The Indoor signals attenuation greatly depend on the material of the structure, i.e. concrete walls attenuates RF signals more than wood walls.

  10. Electromagnetic Waves Basics (cont’) • Units/Measurement of Electromagnetic Fields • A commonly used unit for characterizing electromagnetic fields is “ Power Density”. • Power density is defined as power per unit area. • Power density usually expressed in terms of milli watts per square centimeter (mW/cm^2).

  11. GSM Technology • The Global System for Mobile Communications GSM is a digital cellular communications system. Being able to offer higher capacities than the analogue systems and the customers ability to roam have been the main factors for GSM to be accepted worldwide. • It also offers variety of services and enhanced features.

  12. GSM Technology (cont’) • GSM Network Components The GSM network comprises of two main systems: • Switching System (SS). • Base Station System (BSS).

  13. GSM Technology (cont’) • GSM Frequency Band • GSM 900 ( including E band) • Uplink: 880 – 915 MHz • Downlink: 925-960 MHz • GSM 1800 • Uplink: 1710 – 1785 MHz • Downlink: 1805 – 1880

  14. GSM Base Stations and Air Interface GSM Technology (cont’) • Base stations communicate with mobile phones within a defined area or a “cell”. • Base stations are continuously transmitting. • GSM frequency channels have a bandwidth of 200 KHz. • GSM adopts TDMA technology therefore each channel can be used by 8 users. • The greatest radiation intensity lies within the main lobe of any given antenna.

  15. The need for introducing New GSM Base Stations GSM Technology (cont’) • Improving coverage and quality. • Increasing capacity (more frequent)-mature operators • Commonly 3 types of Base Stations are used (according to coverage and Capacity requirements): • Macro cells • Micro cells • Pico cells

  16. GSM Base Station Antennas GSM Technology (cont’) • Antenna is the Interface between the Radio Networks and the external environment. Radio frequency (RF) energy is coupled from the transmitter to the air and from the air to the receiver. • Omni-directional Antennas: Gives 360 degrees radiation pattern. • Directional Antenna: Where the energy is focused on one of the directions according to the antenna pattern. • Antenna Gain is the ratio of the radiation intensity in the main beam direction to the radiation from isotropic antenna.

  17. Omni-Directional Antenna GSM Technology (cont’)

  18. Directional Antenna GSM Technology (cont’)

  19. Types of GSM Base Stations GSM Technology (cont’) • Macro Cells • Constitute the main backbone of most cellular networks • Height above roof tops. • High output Power: from 25-40 Watts .in addition to the antenna gain (mostly 13 to 21 dBi), which yield to a range of Effective Isotropic Radiated Power EIRP mostly from 500 to 1000 Watt . • Commonly sectorized for efficient frequency utilization hence more capacity. • Coverage ranges from 500 m to 35 km.

  20. Types of GSM Base Stations (cont’) GSM Technology (cont’) • Micro Cells • Height below rooftops. • Low output power, generally 2 W in addition to antenna gain (Mostly 13 to 18 dBi) which yields EIRP up to 40 Watt. • Usually deployed for capacity (in the hot spots)hence spectrum efficiency • Coverage up to few hundred meters.

  21. GSM Technology (cont’) • Types of GSM Base Stations (cont’) • Pico Cells • Mostly Indoors. • Operators usually adjust the power levels to low output due to proximity to humans (usually the antennas are fixed on ceilings or wall mounted) • Customary used to improve indoor coverage and provide additional capacity.

  22. Source: http://radsafe.berkeley.edu Effect of Radiations on Humans • Non-Ionizing Radiation: • Are radiations that do not have sufficient energy to break the chemical Bonds in the body. • The main effect is the heating of the body tissues.

  23. Source: http://radsafe.berkeley.edu Effect of Radiations on Humans (cont’) • Ionizing Radiation: • High-energy radiation, such as X-Ray radiation, where the electromagnetic photons have sufficient energy to break chemical bonds. This energy can remove electrons from the atoms( ionization), which will recombine with other atoms and thereby might cause some damage to biological tissue potentially leading to serious diseases.

  24. Effect of Radiations on Humans (cont’) • Specific Absorption Rate (SAR) • The rate of energy absorption is called Specific Absorption Rate (SAR). It is measured in Watts/Kilograms (W/Kg). • SAR is directly proportional to the conductivity and inversely proportional to the density of tissue. • SAR=σ* E^2/ρ

  25. International Bodies Guidelines • The most widely adopted guidelinesare those developed by: • American National Standards Institute (ANSI) • The Institute of Electrical and Electronics Engineers (IEEE) • International Commission on Non-Ionizing Radiation Protection (ICNIRP) • National Radiological Protection Board (NRPB) • These International bodies are satisfied that below the recommended levels there is no scientific evidence that the exposure poses any health risk.

  26. International Bodies Guidelines (cont’) • The ICNIRP guidelines are less than NRPB (National Radiological Protection Board) guidelines and ANSI/IEEE guidelines. • The ICNIRP guidelines for the public have been incorporated in European Council Recommendations (1999) which have been agreed In principle by all countries in European Union (EU). • Some European countries have incorporated the ICNIRP guidelines into statute.

  27. Exposure levels set by ICNIRP International Bodies Guidelines (cont’) • ICNIRP (International commission on Non-Ionizing Radiation Protection) restriction on exposure for general public: • SAR (Specific Absorption Rate) limit is 0.08 W/kg (average over 6 minutes period). • Power density in GSM 900 MHZ is 4.5 W/square meter. • Power density in GSM 1800 MHZ is 9 W/square meter.

  28. International bodies Findings and Recommendations • Operators can adjust the network settings hence demonstrate compliance with the recommended levels set by ICNIRP. • FCC require specific site environmental assessments for roof top base station Antennas with total power greater than 1000W ERP for cellular (800-900 MHz) . • Power of Indoor antennas must be adjusted to low levels due to the proximity of humans.

  29. International bodies Findings and Recommendations (cont’) • Where the guidelines levels may be exceeded (e.g. next to base stations antenna at a roof top), physical exclusion zones has to be established around the antennas. • Each exclusion zone should be defined by a physical barrier and prominent signs with logos. • Example1: below are “ the estimated worst case horizontaldistances that should be maintained from a single sectorised, cellular base station antenna to meet FCC RF exposure guidelines”* *Source: http://wireless.fcc.gov

  30. * Source: http://wireless.fcc.gov International bodies Findings and Recommendations(cont’) • Example2: the “estimated worst case horizontal distances that should be maintained from a single sectorised PCS base station antenna to meet FCC RF exposure guidelines”*

  31. Source:http://www.mcw.edu International bodies Findings and Recommendations(cont’) • “ The relationship between the RF power density levels required to produce known biological effect, The RF power density levels specified in the safety guidelines , and the RF power density levels actually measured around Mobile Base Stations”

  32. International bodies Findings and Recommendations(cont) • UK NPRB has conducted spot checks in England on the average intensities at some publicly accessible sites around some Base Stations, the maximum was far below the ICNIRP public exposure guidelines. Note: The results might differ if measured in other areas with different circumstances, e.g. different EIRP or number of antennas/operators. Source: http://www.mcw.edu

  33. References • U.S. Federal Communications Commission (FCC),“A Local Government Official’s Guide to Transmitting Antenna RF Emission Safety: Rules, Procedures, and Practical Guidance.”27-29:June 2,2000.http://wireless.fcc.gov/siting/FCC_LSGAC_RF_Guide.pdf. • Stewart Report

  34. Questions?

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