used in wireless technology
cellular: Original cellular technology used in the transmission
of speech, operating as an analogue system at 900 MHz.
Device designed to radiate or receive electromagnetic energy.
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.
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.
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.
A "cell" in the context of mobile phone technology is the
area of geographical coverage from a base station.
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
Harmonics: Multiples of the fundamental frequency used
for a particular source, eg 50Hz harmonics are 100 Hz, 150 Hz, 200 Hz,
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
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
Isotropic (radiator): Having the same properties in
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.