2G, the Second Generation of mobile communications systems. GSM is termed a 2G technology.
3G or Third Generation, is the generic term used for the next generation of mobile communications systems. It is sometimes called UMTS in Europe. The new systems will enhance the services available today and offer multimedia and internet access and the ability to view video footage.
A metallic rod or wire for sending and receiving radio waves. There are different designs in operation.
First mobile phone technology which was phased out in favour of Second Generation digital technology.
Radio transmitter and receiver used for transmitting and receiving voice and data to and from mobile phones in a particular cell. Mobile networks consist of interconnected base station sites serving areas called cells, giving rise to the terms cellular communications
Each antenna site or base station consists of a mast or existing building to support the antennas and associated transmission and network equipment. The radio signals are transmitted by the antennas and not by the supporting structures. The number of frequencies available for use by mobile networks is small compared to the number of subscribers so the same frequencies have to be re-used. To avoid interference, base stations using the same frequency must transmit at low power and be separated by distance.
Restrictions on exposure to electromagnetic fields
that are based on established health effects and biological considerations
The blood-brain barrier (BBB) is a layer between the walls of the blood vessels and brain tissue that is impermeable to certain molecules.
Based on a low-cost, short-range radio link, Bluetooth technology
can connect many types of digital devices without a single cable in sight, giving more freedom to roam.
A structure which protects transmitters and receivers from damage. They can be in the form of large Cabins or smaller cabinets.
A substance, factor or situation that causes or induces cancer.
Case control studies are epidemiological studies in which patients who already have a certain condition are compared with people who do not. Just because there is a statistical relationship between two conditions does not mean that one condition actually caused the other.
Follow-up to a prior experiment using methods that may differ from the original study but that are expected to test for the same result.
Code Division Multiple Access. A technology used for some 2G and 3G mobile communications.
A geographic area of coverage that a Radio Base Stations
covers. Sometimes this is represented by a honeycomb pattern but in practice cell shapes are not so regular. The size of each cell depends on current and projected number of calls, the physical terrain (signals are blocked by man-made and natural obstacles such as buildings, trees and hills) and the frequency of operation.
In order to avoid congestion as the number of users grows the network operator will reconfigure the network and divide large cells into smaller sizes. As the cell size decreases, so also does the transmit power. Larger cells are called macrocells and usually cover cell sizes of more than 1 km. A city centre may have microcells with a range of a few hundred metres. Inside a building such as a shopping centre even smaller cells my be present, these are picocells with ranges of a few tens of metres. A recent development is the femtocell that provides service to an individual home or office. Macrocells may transmit up to 100 watts but picocells or femtocells transmit at levels similar to other wireless home network equipment.
Continuous Wave. An RF signal without modulation.
Deoxyribonucleic acid, the chemical name for genetic material.
Determination by measurements or calculations of the amount and distribution of radio frequency energy absorbed in a human body exposed to electromagnetic fields
The complete range of stored or propagating electric and magnetic field energies. This includes: power line frequencies, RF, infra-red (IR), visible light, UV, X-rays and gamma rays. A major distinction is made in the spectrum between ionising and non-ionising forms.
Electromagnetic energy (EME) is a natural form of energy and occurs in many different forms as shown in the electromagnetic spectrum
above. The largest natural source is the Sun and this generates energy in many parts of the EM spectrum, including radio signals. EME is composed of oscillating (changing) electric (E) and magnetic (M) fields – EM fields.
These fields are characterised
by frequency (in units of Hertz – Hz) and wavelength (in units of metre). The frequency is the number of crests or troughs that pass by a point in space in one second. The wavelength is the distance between two peaks or two troughs of an electromagnetic wave.
The frequency and wavelength are interrelated by the velocity of light in free space, which has a value of 3x108 ms-1 (metres per second). This relationship is given by the following equation: velocity = frequency x wavelength. For example the domestic microwave oven uses a frequency of 2.45 GHz (2,450,000,000 Hz), which corresponds to a wavelength of about 0.12 m (12 cm). More information on metric or SI prefixes can be found here
Fields at different frequencies within the EM spectrum behave differently in their interactions with matter. Static magnetic fields are associated with magnetic resonance imaging (MRI) machines used for certain scans. Extremely low frequency (ELF) fields are produced by electrical wiring and equipment. These primarily induce currents in the body that may stimulate nerves or muscles.
For about 100 years a range of frequencies have been used for communication, radio frequency (RF) signals. RF signals at higher frequencies are sometimes termed microwaves – a reference to their short wavelength. Radio signals primarily cause heating of the body, internal to the body at low frequencies and closer to the skin at higher frequencies.
Infrared (IR) energy may be sensed through thermal receptors in the skin and is associated with electric bar heaters. A very narrow band of frequencies can be seen as light and may induce photochemical effects, for example, photosynthesis in plants.
Ultra-violet (UV) energy triggers the tanning response in skin but about halfway through the UV part of the spectrum there is sufficient photon (or intrinsic) energy to cause ionization, that is, to break molecular bonds. If these bonds form part of genetic material, ionizing energy may be able to cause direct genetic damage, thus initiating cancer.
At higher frequencies still there are more penetrating forms of energy, such as used for medical x-rays or produced in nuclear reactions.
Another term to be defined is radiation - the transfer of energy through space. It does not indicate whether the energy is ionizing or non-ionizing. Scientists thus sometimes refer to electromagnetic radiation (EMR) or radiofrequency radiation (RFR).
It is important to note that RF signals are a form of non-ionizing energy.
. Electromagnetic waves are emitted by many natural and man-made sources and play a very important part in our lives. Electromagnetic waves are used to transmit and receive signals from mobiles phones and their base stations. The type of electromagnetic waves mobile phones use is called radio frequency (RF) waves/fields.
Study of the cause and distribution of diseases in human populations.
External electromagnetic fields
incident on a person. The quantity of an exposure depends on the duration and strengths of the fields.
The co-axial cable which connects an antenna to a base station transmitter or receiver.
The amplitude of the electric or magnetic fields. Related to the Power density
through the impedance of free space.
Frequency is the number of times per second at which an electromagnetic wave oscillates. It determines the wave's properties and usage. Frequencies are measured in hertz (Hz). 1 Hz is one oscillation per second, 1 kHz a thousand, 1 MHz is a million and 1GHz is a thousand million. Frequencies between 30 kHz and 300 GHz are widely used for telecommunication
, including broadcast radio and television, and comprise the radio frequency band. Mobile telephone systems currently operate in the 800 MHz, 900MHz, 1800MHz, 1900 MHz and 2100 MHz bands.
All exposure to electromagnetic fields
experiences by members of the general public, excluding occupational exposure or exposure during medical treatment.
All exposure to electromagnetic fields
experiences by members of the general public, excluding occupational exposure or exposure during medical treatment.
Another term for the magnetic field.
As the mobile phone user moves, the call is passed between neighbouring cells, a process called handover
. If there are gaps in the available coverage the call could be dropped. As mobile phones are low power devices the antennas need to be located near to mobile phone users. This also ensures that the mobile phone transmits at the lowest power consistent with call quality and limits interference between cells and increases talk-time.
These studies use isolated cells or similar preparations and can provide important insights into fundamental mechanisms, however, they cannot generally provide convincing evidence of adverse health consequences due to their isolated and artificial nature.
Studies using animals that are more informative for risk assessment than in vitro studies but there remain uncertainties due to biological differences with humans and aspects of RF energy absorption.
Intentional radiators are designed to radiate EMF and the levels they emit are strictly controlled by EMC and EMF guidelines.
Electromagnetic energy with sufficient photon (intrinsic) energy to break chemical bonds. This occurs partway through the UV portion of the electromagnetic spectrum, e.g. X-rays or gamma rays. Ionisation is a process in which an atom or molecule loses or gains electrons, acquiring an electric charge or changing an existing charge.
A matrix or table is developed that classfies worker exposure to an agent (such as EMF) according to job descriptions. This is then used to assess whether past exposures are related to the disease under study. It is less accurate than individual exposure assessment but this may not be possible for past exposures.
Short for kilohertz. 1 kHz = 1,000 Hz.
The maximum exposure level below which adverse health effects have been excluded by scientific research. See also Basic Restrictions and Reference Levels.
An epidemiological study comparing one group with exposure to EMF to another group without exposure to EMF and then monitoring both groups (cohorts) over time to determine if there is an increased risk of disease in the exposed group.
A macrocell provides the largest area of coverage within a mobile network. The antennas for macrocells can be mounted on ground-based masts, rooftops or other existing structures. They must be positioned at a height that is not obstructed by terrain or buildings. Macrocells provide radio coverage over varying distances depending on the frequency used, the number of calls made and the physical terrain. Macrocell base stations have a typical power output in tens of watts.
A ground-based structure that supports antennas at a height where they can satisfactorily send and receive radio waves. A typical mast is 15m high, and of steel lattice or tubular steel construction. New slimmer versions of masts are now available which can be painted to blend in with their surroundings, disguised as trees or used in conjunction with street lighting and CCTV cameras. Masts themselves play no part in the transmission of the radio waves.
A mechanism as a theoretical understanding that can be used to predict a biological effect in humans; can be described by a formula; is supported by strong evidence and is widely accepted by scientific experts. Therefore, a mechanism can be used to extrapolate from animal data to predict the likelihood of a range of exposures leading to adverse health effects in humans.
Microcells provide additional coverage and capacity where there are high numbers of users within urban and suburban macrocells. The antennas for microcells are mounted at street level, typically on the external walls of existing structures, lamp-posts and other street furniture. Microcell antennas are smaller than macrocell antennas and when mounted on existing structures can often be disguised as building features. Microcells provide radio coverage over distances, typically between 300m and 1000m and have lower output powers compared to macrocells, usually a few watts.
Modulation is the addition of information to an RF signal by changing some aspect such as the amplitude, frequency or phase.
MtCO2e - Million metric tons of carbon dioxide equivalent. This measure can aggregate different green house gases into a single measure, using global warming potentials. One unit of carbon is equivalent to 3.664 units of carbon dioxide.
The near field is the region close to an antenna, where the electric and magnetic fields are not related to each other solely by the characteristic impedance of free space.
NElectromagnetic energy with insufficient photon (intrinsic) energy to break chemical bonds.
Exposure to electromagnetic fields during work that are experiences by people having appropriate knowledge about EMF.
A chemical marker of cell proliferation or growth.
A picocell provides more localised coverage than a microcell. These are normally found inside buildings where coverage is poor or where there are a high number of users such as airport terminals, train stations or shopping centres.
When subjects experience positive reactions due to belief about exposure to an agent that is generally regarded as inert.
The energy flowing from an antenna through a unit area normal to the direction of propagation in a unit time. This is measured in Watts per square meter.
Pulses per second.
Technical term to describe energy travelling through space, equally applicable to infra-red (IR), light, RF or ultra-violet (UV).
These are generally derived from relevant basic restrictions using measurement and/or computational techniques. Compliance with the reference level will ensure compliance with the relevant basic restriction. If the measured or calculated value exceeds the reference level, it does not necessarily follow that the basic restriction will be exceeded. However, whenever a reference level is exceeded, it is necessary to test compliance with the relevant basic restriction and to determine whether additional protective measures are necessary.
The duplication of a prior experiment using methods very similar to the original study. If the method changes then it may be described as a confirmation study.
An interactive process of exchange of information and opinion among individuals, groups and institutions. It involves multiple messages about the nature of risk and other messages, not strictly about risks, that express concerns, opinions, or reactions to risk messages, or to legal and institutional arrangements for risk management. See the related GSMA information.
Risk perception is the subjective judgment that people make about the characteristics and severity of a risk. Age, gender, cultural background, family and education all influence risk perceptions. Other external factors that influence risk perception include: Familiar vs. Unfamiliar Technology; Personal Control vs. Lack of Control Over a Situation; Voluntary vs. Involuntary Exposure; Dreaded vs. Not Dreaded Outcome; Direct vs. Indirect Benefits and Fair vs. Unfair Exposure.
Radio Frequency. That portion of the electromagnetic spectrum between about 3 kHz and 300 GHz generally used for radiocommunications purposes.
SAR (Specific Absorption Rate) is a measure of the amount of RF power absorbed in any part of the human body due to the use of equipment such as mobile phones or by human exposure close to other transmitting sources. The units are Watts per kilogram (W/kg).
Click here to understand more about SAR.
- Observation: Identification of a specific idea is always the first step. This may be an original idea, the result of other background research or sometimes based on anecdotal reports but it must be properly identified and clearly defined.
- Hypothesis: The hypothesis is best described as a tentative theory or a working assumption. It is developed following research to find our what is already known about the observation. The hypothesis is then used to make predictions of probable effects that can be tested by experiment.
- Experiment: Conducting a well-designed experiment is the most important step of the process. Much effort is made at this stage to properly design or "control" the experiment so that other external factors ("confounders") cannot influence the outcome. The collected data is analysed and the hypothesis must be rejected or modified if not supported by the experimental outcome.
- Conference Reporting: Researchers may report preliminary findings at conferences to share knowledge and obtain feedback. The may revise the hypothesis or experiment based on this feedback. Interim results presented at conferences have not benefited from peer review and should be interpreted with caution.
- Peer Review: During peer review the study design and results are critically examined by one or more reviewers with expertise in the subject. The reviewers are selected by the journal editor and is usually conducted anonymously. Peer review is important for quality control of research claims and protects the reputation of the researcher and the journal. The reviewer may recommend acceptance, amendment or rejection of a research paper to the editor of the scientific journal. The process of submission, review, amendment and resubmission may take several months.
- Publication: Following acceptance by the journal editor, the paper will be prepared for publication and assigned to a future issue of the journal. Increasingly, accepted research papers are made available on-line before appearing in the print journal. After it appears, other scientists may comment on the results by writing to the journal and the researchers can choose whether to respond. Publication in a peer-reviewed journal provides some confidence that the study has been well conducted and many public health risk assessments use this as a threshold for considering scientific evidence. However, not all published research is without flaws and the quality of peer review varies across journals.
- Replication: Results may be further tested by independent replication. Independent replication is essential to minimising the effects of potential personal and experimental bias. The follow-up studies may try to duplicate the original study (direct replication) or try to improve some aspect of the experimental conditions (confirmation study). If the original results are confirmed then greater weight is given to the hypothesis. much greater weight is given to the original results.
- Established Knowledge: In order to arrive at a scientific consensus, the results of many experiments are compared through a weight of evidence approach. This is not simply a case of counting publications, individual peer reviewed studies are examined and their strengths and weaknesses noted. This allows overall conclusions to be formed about the strength of the evidence for the hypothesis and a consensus of what is established knowledge about a subject. However, science is not static and even established theories may be challenged by new experimental findings that have followed the scientific method.
Antenna which transmits or receives higher signal levels in a horizontal direction. The base station is split into several sectors (typically 3 or 6) to provide 360 degree coverage.
A roof-mounted mast structure which supports multiple antennas at a height where it can satisfactorily send and receive radio waves. A stub mast is typically 4m – 6m high and of steel lattice construction. Stub masts themselves play no part in the transmission of radio waves.
TErrestrial Trunked RAdio, typically used by utilities and emergency services.
The sum of the frequency exposure quotients of all the bands at a single location.
Electronic equipment that generates radio frequency electromagnetic energy and is connected to an antenna via a feeder cable.
Unintentional radiators are not designed to radiate EMF. Any EMF they do emit are controlled by EMC guidelines.
Radio signals in the frequency range from 30 MHz to 300 MHz and with wave lengths ranging from 10 to 1 m. Radio signals in this range include broadcast FM radio at 88-108 MHz and some television channels.
Wavelength is the distance in metres between any two ‘similar’ points on a radio wave. This portion of the wave is referred to as one complete cycle. The lower the frequency of a wave the longer the wavelength. For example, the wavelength of ocean waves is the distance between one crest and the next, or one trough and the next.
Wireless local area network (WLAN) is a low power radio technology which provides special zones for accessing a local area network over a short range, for instance at airports or hotels.
Wireless metropolitan area network (WMAN) is providing wireless connection for broadband or multimedia users over a medium range, for instance covering small urban areas.
A form of ionising radiation that can penetrate most matter and used for medical diagnosis.
Exposure standards are basic standards of personal protection that generally refer to maximum levels to which whole or partial body exposure is permitted from any number of EMF transmitting devices. This type of standard normally incorporates safety factors and provides the basic guide for limiting personal exposure. International standards have been developed by the International Commission on Non-Ionizing Radiation Protection
Emission standards set various specifications for electrical devices and are generally based on engineering considerations, e.g. to minimize electromagnetic interference with other equipment and/or to optimize the efficiency of the device. While emission limits are aimed at ensuring, inter alia, compliance with exposure limits, they are not explicitly based on health considerations. In general, emission standards aim to ensure that aggregate exposure to the emission from a device will be sufficiently low that use, even in proximity to other EMF emitting devices, will not cause exposure limits to be exceeded.
Compliance standards describe how compliance with exposure or emission standards may be ensured. They may provide guidance on how to assess the EMF exposure due to an installation or a product by either calculation or measurement. The international compliance standards for base stations and mobile phones are IEC62232