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Terms used in wireless technology

Air interface: In a mobile phone network, the radio transmission path between the base station and the mobile terminal

Analogue cellular: Original cellular technology used in the transmission of speech, operating as an analogue system at 900 MHz.

AM: Amplitude modulation.

Advanced mobile phone system (AMPS): The first generation was the analog mobile phone system standard that uses FDMA transmission technology (Frequency Division Multiple Access).

Antenna: Device designed to radiate or receive electromagnetic energy.

APC: Adaptive power control. System used to control mobile phones and base stations in order to ensure that the radiated power does not exceed the minimum consistent with high quality communication. The system effectively operates to reduce average radiated powers.

Bandwidth: A term meaning both the width of a transmission channel in terms of Hertz and the maximum transmission speed in bits per second that it will support.

Basic restriction: Restrictions on exposure to electromagnetic fields that are based on established health effects and biological considerations.

Bluetooth: A low power, short range wireless technology designed to provide a replacement for the serial cable. It can connect a wide range of personal, professional and domestic devices such as laptop computers and mobile phones together wirelessly.

Base station: Facility providing transmission and reception for radio systems. For macrocells, the infrastructure comprises either roof- or mast-mounted antennas and an equipment cabinet or container. For smaller microcells and picocells, the antennas and other equipment may be housed in a single unit.

CDMA: Code division multiple access that encodes signals to a number of users, so that all of these users cab simultaneously use a single, wide frequency band. Each user's handset decodes the information for that user, but cannot access information for any other user.

Cell/cellular: A "cell" in the context of mobile phone technology is the area of geographical coverage from a base station. A cell site may sectorize its antennas to service several cells from one location cell site. The facility housing the transmitters/receivers, the antennas and associated equipment

Continuous wave (CW): Successive oscillations which are identical under steady-state conditions (an unmodulated electromagnetic wave).

Decibel (dB): A measure of the increase or decrease in power, P, at two points expressed in logarithmic form. Gain = 10 log10 (P2/P1).

DECT: Digital enhanced cordless telecommunications. A second generation digital cordless technology standardized by ETSI.

Digital cellular: Technology introduced in the 1990s as a method of transmitting speech and data. Offers increased security, and technical advantages with low powered phones.

Dosimetry: Measurement of the absorbed dose or dose rate by an object, as in a radiofrequency field.

DTX: Discontinuous transmission. System regulating mobile phones to reduce the rate at which bursts are transmitted when there is no speech. The system has the effect of reducing the time of exposure to approximately half (assuming an equal conversation.

Dual Band: The capability of cellular infrastructure elements and handsets to work across two frequency bands, usually the 900MHz and 1800MHz bands. The capability to seamlessly handover between the two bands offers operators major capacity gains.

Effective radiated power (ERP): Power supplied to the antenna multiplied by the gain of the antenna in that direction relative to a half-wave dipole.

EIRP: Equivalent isotropically radiated power. This is the power that would have to be emitted in all directions to produce a particular intensity and so takes account of the transmitter power plus the characteristics of the antenna.

Electric field:The regions surrounding an electric charge, in which the magnitude and direction of the force on a hypothetical test charge is defined at any point.

Electric field strength (E): The magnitude of a field vector at a point that represents the force (F) on a point charge (q) divided by the charge: E=F/q (unit Vm¯¹).

Electromagnetic fields: Electric and magnetic fields associated with electromagnetic radiation.

EMF: Electromagnetic field.

Far-field zone: The space beyond an imaginary boundary around an antenna. The boundary marks the beginning where the angular field distribution is essentially independent of the distance from the antenna. In this zone, the field has a predominantly plane-wave character.

FDD: Frequency Division Duplex.

Frequency Division Multiple Access (FDMA): A transmission technique where the assigned frequency band for a network is divided into sub-bands which are allocated to a subscriber for the duration of their calls

Finite-Difference Time-Domain (FDTD): An electromagnetic modeling techniques. It is implemented in software, and since it is a time-domain technique it can cover a wide frequency range with a single simulation run.

Frequency: Number of complete cycles of an electromagnetic wave in a second (unit hertz, Hz).

GSM: Global system for Mobile Communications (second generation, 2G). An international operating standard for digital cellular mobile communications. Enables mobile phones to be used across national boundaries.

Handoff: The transfer of control of a cellular phone call in progress from one cell to another, without any discontinuity.

Harmonics: Multiples of the fundamental frequency used for a particular source, eg 50Hz harmonics are 100 Hz, 150 Hz, 200 Hz, etc.

Hertz (Hz): Unit of frequency. One cycle per second.

ICNIRP: International Commission on Non-Ionizing Radiation Protection, an independent scientific body that has produced an international set of guidelines for public and occupational exposure to radio frequencyfields.

Impedance (of free space): Ratio of electric to magnetic field strength of an electromagnetic wave. In free space the value is 377 O.

IMT-2000: International Mobile Telecommunications-2000. The family of third generation technologies approved by the ITU. IMT-DS, a direct sequence WCDMA FDD solution IMT-TC, a WCDMA TDD solution IMT-MC, a multicarrier solution developed from cdma2000 IMT-SC, a single carrier solution developed from IS-136/UWC-136 IMT-FT, a TDMA/TDD solution derived from DECT.

IMT-2000: International Mobile Telecommunications-2000. International name for UMTS.

Intensity: Power crossing unit area normal to the direction of wave propagation (unit watts per square metre, Wm?²). See also power density.

Isotropic (radiator): Having the same properties in all directions.

Megahertz (MHz): a unit of frequency equal to one million Hertz

Magnetic field: Produces a force on a charged object moving at an angle to it (unit tesla, T). (See also magnetic flux density).

Magnetic field strength (H): A field vector that is equal to the magnetic flux density divided by the permeability (µ) of the medium (unit, A m?¹).

Magnetic flux density (B): The magnitude of a field vector that is equal to the magnetic field H multiplied by the permeability (µ) of the medium (unit tesla, T): B = µH.

Microwave: Electromagnetic radiation of ultra-high frequencies between 300 MHz and 300 GHz.

Near-field zone: A volume of space generally close to an antenna in which the fields do not have a substantially plane-wave character, but vary considerably from point to point.

Occupational exposure: Exposure to electromagnetic fields during work that are experiences by people having appropriate knowledge about EMF.

PCN: Personal Communications Network. A mobile system principally directed towards the hand portable, domestic user market and operating with digital technology at 1.8 GHz.

Plane wave: A wave such that the corresponding physical quantities are uniform in any plane perpendicular to a fixed direction.

Power density: Power crossing unit area normal to the direction of wave propagation (unit watts per square metre, W m?²). (See also intensity).

Power (flux) density (S): Power crossing unit area normal to the direction of wave propagation.

Radiation (electromagnetic): The emission or transfer of energy through space in the form of electromagnetic waves.

Radiofrequency (RF): Electromagnetic radiation used for telecommunications and found in the electromagnetic spectrum at longer wavelengths than infrared radiation (see Figure 1). A frequency or rate of oscillation within the range of about 3 kHz to 300 GHz.

RF device: A device which generates and/or utilizes RF energy.

Reverberation chamber: An environment for electromagnetic compatibility (EMC) testing and other electromagnetic investigations.

Specific Absorption Rate (SAR): Specific energy absorption rate: Rate at which energy is absorbed by unit mass of tissue in an electromagnetic field (unit watts per kilogram, W kg-1).SAR is a measure of the rate at which radiofrequency (RF) energy is absorbed by the body when exposed to an RF electromagnetic field. The most common use is in relation to cellular telephones.

Third generation: Next evolution of mobile phone technology, based on UMTS and expected to result in widespread use of video phones and access to multimedia information.

TDD: Time Division Duplex.

TDMA: Time division multiple access. System that divides each frequency band into a number of time slots, each allocated to a single user. Allows several users to operate on the same frequency at the same time.

TETRA: Terrestrial Trunked Radio system.

UMTS: Universal Mobile Telecommunications System. UMTS is one of the third-generation (3G) cell phone technologies. Currently, the most common form of UMTS uses W-CDMA as the underlying air interface.

Wavelength (λ): Distance between two successive points of a periodic wave in the direction of propagation, in which the oscillation has the same phase (unit metre, m).

WCDMA: Wideband Code Division Multiple Access, a 3rd generation technology for wireless communication.

Reference: NRPB. Mobile Phones and Health 2004. Documents of the NRPB, volume 15, no.5, 2004.