Terms used in wireless technology

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

AM: Amplitude modulation.

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.

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.

CW: Continuous 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.

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.

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 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.

FDD: Frequency Division Duplex.

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.

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.

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. 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.

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.

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.

Radiofrequency (RF): Electromagnetic radiation used for telecommunications and found in the electromagnetic spectrum at longer wavelengths than infrared radiation (see Figure 1).

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).

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.

Wavelength (?): 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).

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