A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
| AIC | Advanced Intelligent Networks |
| Amplification: | An increase in the strength (current, voltage, or power) of a signal. |
| Amplifier: | A device that increases the strength (current, voltage, or power) of a signal fed to its inputs. |
| Amplitude: | The highest value a varying quantity (i.e. voltage or current) reaches as it passes from a reference value (zero, for example) and increases in value in one direction. |
| Amplitude Modulation (AM): | Type of modulation in which the amplitude of a carrier wave is caused to vary in accordance with the amplitude variations of the information to be transmitted. |
| Amplitude Shift Keying (ASK): | The carrier amplitude is switched between two discrete values to generate the waveform. |
| Analog Information: | Information continuously changing at unspecified increments over an unspecified interval. Human speech is an example of analog information. |
| Angle Modulation: | Type of modulation in which the angle (either frequency or phase) of a wave is varied in accordance with the amplitude variations of the information. The two forms of Angle Modulation are Frequency modulation (FM) and Phase Modulation (PM). |
| Antenna: | A conductor or system of conductors for radiating or receiving radio waves (electromagnetic energy). |
| Aperiodic: | A wave that is not a repeating function; therefore any wave, whether sinusoidal or non-sinusoidal, that occurs randomly or at irregular intervals. |
| Asynchronous: | Communication in which data characters are individually synchronized and may be sent at any time. |
| A-TDMA | Advanced Time Division Multiple Access |
| Attenuator: | A passive network that reduces the power of a signal without introducing appreciable distortion. |
| Attenuation: | The action by which the power of an electrical signal, radio wave, or sound wave is decreased. |
| AuC | Authentication Center |
| Audio Amplifier: | A device which is used to strengthen (increase in amplitude) frequencies in the audio range (20 to 20,000 Hz). |
| Audio Frequency (AF): | A frequency corresponding to a normally audible sound wave (20 to 20,000 Hz). |
| Automatic Relay: | A type of relaying in which the information being sent to the next destination is not only amplified, but also restored to the original length and form. |
| Auxiliary Radio Link: | A link that operates in conjunction with but independent of a broadband radio link for the purpose of providing service, telesignaling, and telecontrol. Also called the service channel or order wire. |
| Azimuth: | Direction (side-to-side in the horizontal plane) from a point on Earth, usually expressed in degrees. North = 0; East = 90; South = 180, West = 270. |
| Band: | A group of frequencies identified by a lower and upper limit. |
| Bandpass: | A circuit or component characteristic that permits the passage of a single band of frequencies while attenuating those frequencies above and below that frequency band. |
| Band-Reject: | A circuit or device that rejects a specified frequency band while passing those frequencies that lie above and below the rejected band (opposite of band-pass). Sometimes called band-rejection, as applied to a filter. |
| Bandwidth: | The frequency width of a circuit or component, such as a band-pass filter or tuned circuit. Usually measured at the half-power points on the response curve (-3 dB points). Also, the range of frequencies necessary to detect the effective frequency comp onents of a signal. |
| Baseband: | The range of frequencies occupied by a signal before it modulates the carrier wave. The signal in the baseband is usually at frequencies that are substantially lower than that of the carrier. On the low end, the baseband may approach or include DC (0 Hz). The high end depends on the rate at which information occurs as well as the presence of subcarriers or other special signals within the baseband and containing all frequency components of the multiplexed signal. The bandwidth of the baseband is exp ressed in Hertz (HZ). |
| Base Transceiver | The network base station that talks to the mobile. |
| Baud: | A unit of signaling speed equal to the number of discrete conditions or events per second. |
| Beamwidth: | The angular width of the main lobe of an antenna radiation pattern as measured between predetermined points on the lobe, usually the half-power (-3 dB) points. |
| Beat Frequencies: | Frequencies resulting from the combination of two or more different frequencies in a non-linear device, such as an amplifier, numerically equal to the sum and the difference of these frequencies. |
| Beat Frequency Oscillator (BFO): | An RF oscillator in a radio receiver whose output mixes with a received signal to produce a difference frequency in the AF range. The audio frequency thus produced contains the information. A BFO is made variable so that the operator may adjust the au dible (information) signal to a frequency required by terminal equipment. |
| Bi-Directional: | An antenna which radiates most of its power in two directions. A pattern whereby the radiation from a antenna is concentrated in two directions. |
| Binary: | The base-two number system, using the numerals 0 and 1. |
| Bit(s): | Short for Binary Digit. The basic element of binary information, usually represented by 0 and 1. |
| Branching Station: | A station in a microwave network that has the capability of switching signals to other networks. |
| Broadband: | A device or circuit that is broadband has the capability of being operated over a broad range of frequencies. |
| Broadband Radio Systems: | Refers to high capacity multichannel systems or more specifically, bandwidth. |
| BS | Base Station |
| BSC | Base Station Controller |
| Byte: | A group of 8 bits. |
| Cable Systems: | Communications systems employing cables to create a signal path. |
| Carrier: | A wave having at least one characteristic; amplitude, frequency, or phase; that can be varied from a known reference by modulation. That known reference is typically a steady sine wave by could be a recurring series of pulses in which no signal is pres ent between pulses. |
| Carrier Frequency: | The frequency of the original unmodulated radio frequency wave produced by a transmitter-oscillator, the center about which the information appears. |
| Carrier System: | A system permitting a number of independent communications over the same circuit. |
| CCIR: | International Radio Consultative Committee. A non-regulatory organization that establishes technical recommendations for international telecommunications networks. (see note 1) |
| CCITT: | International Telegraph and Telephone Consultative Committee. (see note 1) |
| CDMA | Code Division Multiple Access |
| Center Frequency: | The frequency assigned to the carrier, the center of the lobe or spike. |
| Channel: | The medium through which a communication signal must pass. The channel contains noise and interference that the communication must overcome in order to be properly received. |
| Channel-Band Sharing: | The utilization of two or more intelligence means within the same voice-grade channel. This is accomplished by breaking the channel into bands and utilizing one portion of the band to pass one system and the other band to pass the other system. (i.e. v oice and printer in the same VGC). |
| Channel Rate: | The number of channels per second that are transmitted in a TDM system. It is found by multiplying the number of channels in the system by the Frame Rate. Also known as Channel Repetition Frequency. |
| Chip: | A single bit in the pseudorandom code of a direct sequence system. |
| Chip Rate: | The number of chips (bits) per second of a direct sequence system. |
| Chirp: | A method that employs a carrier that is swept over a range of frequencies. This method is most common in ranging and radar systems. |
| CLIP | Caller Line Identity Presentation |
| CLIR | Caller Line Identity Restriction |
| Coaxial Cable (COAX): | A cable in which one conductor is accurately centered inside another. |
| Code Division Multiple Access (CDMA): | A multiplexing method that allows two or more direct sequence systems to be transmitted over the same nominal radio frequency. This is accomplished by assigning a different pseudorandom code to each signal. |
| Coherent: | Agrees in frequency and phase with a reference. |
| COMINT | As its name indicates, COMINT is intelligence obtained by the interception, processing, and analysis of the communications of foreign governments or groups, excluding radio and television broadcasts. The communications may take a variety of forms--voice, Morse code, radio-teletype or facsimile. The communications may be encrypted, or transmitted in the clear. |
| Commutation: | The technique of sampling a number of data inputs in time sequence by either mechanical or electronic means. |
| Compandor: | A device which compresses the volume range of speech signals by imparting more gain to the lower frequencies than to the higher frequencies prior to transmission. The signal is restored to its original values at the input to the receiver. Compandor is short for COMpressor and exPANDor. |
| Conductor: | A wire, cable, or other object capable of carrying electric current. |
| Control Channel | The channel the phone and cell base station first communicate on. |
| Converter: | A circuit used to convert one frequency to another. In a receiver, the converter stage converts the incoming signals to the Intermediate Frequency (IF). |
| Correlation: | Fundamental process in a spread spectrum system and forms a common method of receiving signals. Correlation measures how alike two signals are; that is, how similar in appearance they are to each other. The degree of likeness is often expressed as a n umber between zero (0) and one (1). A perfect match is typically indicated by a one, while no match may be indicated by a zero. Partial matches yield values between one and zero, depending upon likeness. In spread spectrum receivers, correlation is oft en used to identify a signal that has been coded with a desired PN (Pseudorandom Noise) sequence. |
| Critical Angle: | The highest angle of transmission at which a given frequency will return to Earth. |
| Critical Frequency: | The highest frequency at which waves sent vertically upward are reflected directly back to Earth. |
| Crosstalk: | Unintentional transfer of a signal from one channel to other channels. |
| Cycle: | One complete revolution of a commutator or its electronic counterpart; one occurrence of a periodic wave. |
| Decay Time: | The period of time during which the stored energy or information decays to a specified value less than its initial value. For pulses, it is the time required for the trailing edge of a pulse to fall from 90% of its maximum value to 10% of its maximum v alue. |
| Decibel (dB): | A logarithmic expression of power ratio; also used as an expression of voltage ratios, provided the voltages appear across identical values of resistance or impedance. A decibel is 1/10th of a "bell". Also, a dimensionless unit of power measurement us ed for expressing the magnitude of a change in signal levels or sound levels. |
| Decimal: | The base-ten number system, using the numerals 0 through 9. |
| Dedicated Channel: | Voice Grade Channel in a multichannel system assigned to a specific subscriber or entity. |
| Delta Modulation: | Also called "Single Bit PCM" or "Poor Man's PCM". A system or technique by which analog information is converted to binary form. An increase between two successive sampling points is assigned a binary "1" and a decrease is assigned a binary "0". Delt a Modulation does not provide information relating to exact or even approximate values of the modulating wave, but does convey information relating to its slope. |
| Demodulation: | The process of extracting the original modulating signal from a modulated wave. |
| Desense: | A problem characteristic of many radio receivers in which a strong RF signal overloads the receiver, reducing sensitivity. |
| Detector: | The stage in a receiver at which demodulation takes place. Also called the demodulator. |
| Deviation Ratio: | The ratio between the maximum frequency deviation and the highest modulating frequency. |
| Dial Tone: | Also referred to as a ringer or attention tone, used to set up certain telephone channels. Its position in the baseband is determined by the system being used. |
| Differential Phase Shift Keying (DPSK): | Used where it is required that there be enough stability in the transmission path to allow negligible phase change from one information pulse to the next. Information is encoded differentially in terms of phase change between two successive pulses. |
| Diffraction: | The effect produced when waves (light, sound, or radio) encounter a barrier and bend around it. |
| Diplexing: | The simultaneous transmission or reception of two signals while using a common antenna, made possible by using a device called a diplexer. Used in TV broadcasting to transmit visual and aural carriers by means of a single antenna. |
| Direct Sequence: | A means of signal spreading in which a very fast binary stream is used to shift the phase of an RF carrier. This binary sequence is designed to appear to be random (a mix of approximately equal numbers of ones and zeros), but is generated by a digital circuit. The binary sequence can be duplicated and synchronized at the transmitter and receiver. |
| Directivity: | The property of an antenna to receive or transmit more effectively in one direction than in any other. |
| Discrete Information: | Information changing at specified increments and intervals. A digital communication signal is one example of a discrete information source. |
| Dish: | An antenna reflector for use at VHF and higher frequencies that has a concave shape. For example, a part of a sphere or parabolid. |
| Distortion: | Any unwanted change in the form of a wave which occurs during transmission or amplification. |
| Diversity Reception: | A means of reducing the possibility of fading by using additional antennas or frequencies for reception. |
| Doppler: | The phenomenon evidenced by the change in the observed frequency of a wave in a transmission system caused by a time rate of change in the effective length of the path of travel between the source and the point of intercept. |
| Double Sideband Transmission: | The transmission of a modulated carrier wave accomplished by both of the sidebands resulting from modulation. The upper sideband corresponds to the sum of the carrier and modulating frequencies, whereas the lower sideband corresponds to the difference between the carrier and modulating frequencies. |
| Duplex: | Simultaneous two-way independent transmission and reception in both directions. |
| Duty Cycle: | The relationship of pulse duration to the pulse period in percent. |
| Dwell Time: | The amount of time a frequency hopping signal spends on one specific frequency before hopping to the next. |
| Dynamic Information: | Information rate of change of greater than 10 percent. |
| EIR | Equipment Identity Register |
| E Layer: | A region of the upper atmosphere about 55 to 85 miles above the Earth's surface (during daylight hours only). |
| Electromagnetic Line of Sight (EMLOS): | The direct wave path between two antennas (including the effects of atmospheric refraction and diffraction but not reflection). |
| Electromagnetic Wave: | A wave characterized by variations of electric and magnetic fields. |
| Emitter: | A controlled source from which energy is transmitted for a specific purpose; i.e., radar, communications, data transmission, etc.. |
| Encoding: | Converting a character into its equivalent combination of bits. |
| ESN | Electronic Serial Number |
| Even Parity: | Error detection technique in which an extra element is added to the transmitted character so that the overall number of ones in the transmitted character is always even. |
| Extremely High Frequency (EHF): | The range of radio frequencies from 30 to 300 Gigahertz. |
| F Region: | The region of the atmosphere extending about 90 to 250 miles above the Earth's surface. |
| Fading: | Variations in the strength of a radio signal at the point of reception. |
| FDMA | Frequency Division Multiple Access |
| Feedback: | A portion of the output voltage being fed back to the input of an amplifier. Feedback includes AC and DC voltage components which can be used separately or together, depending on the particular circuit. |
| Filter: | A circuit designed to pass a certain range of frequencies while rejecting undesired frequencies. |
| Flip-Flop: | An active circuit or device that can assume either of two stable stages at a given time, as dictated by the nature of the input signal. |
| Forward Scatter: | A method of radio wave propagation utilizing the phenomena of particle refraction and/or scattering of radio waves in either the atmosphere or stratosphere with scatter predominately in the forward direction. |
| Frame: | One revolution of the commutator rotor. In a TDM system, the equivalent of the video baseband. |
| Frame Length: | The time it takes to complete one frame, the reciprocal of the Frame Rate. |
| Frame Rate: | The rate at which each frame, including the sync and intelligence pulses is transmitted, measured in frames per second. |
| Frequency: | The number of cycles occurring in a given period of time, usually one second. It is expressed in terms of Hertz. |
| Frequency Deviation: | A peak frequency change or shift to either side of the assigned carrier frequency. |
| Frequency Diversity Reception: | Diversity reception involving the use of carrier frequencies separated 500 Hz or more and having the same modulation to take advantage of the fact that fading does not occur simultaneously on different frequencies. The receivers minimize the effects of fading by using, at each instant, the frequency having the higher signal strength. |
| Frequency Division Multiple Access(FDMA): | Multiple access being achieved through frequency band discrimination; either in the ground receiver, in the case of a side band frequency translating repeater, or in the satellite, in the case of a frequency channelized satellite. |
| Frequency Division Multiplex (FDM): | A method of sending each of the information streams over separate subcarriers, each at a different frequency. The subcarriers could be modulated in various ways, according to the nature of the information. The frequency spectrum is thus broken up into bands or channels and transmitted on a common carrier. |
| Frequency Hopping: | A form of Spread Spectrum in which the center frequency of a conventional carrier is altered many times per second in accordance with a pseudorandom list of frequencies. |
| Frequency Modulation (FM): | Modulation in which the frequency of the carrier is caused to vary in an amount proportional to the amplitude of the modulating wave. |
| Frequency Shift: | The amount a carrier shifts between two adjacent frequencies. |
| Frequency Shift Keying (FSK): | The frequency of the carrier is shifted rapidly between two frequencies, known as the mark and space frequencies. |
| Frequency Swing (fs): | The difference between the maximum and minimum frequency limits of the carrier. |
| Full-Duplex: | Operation is simultaneous two-way signaling. Full-duplex serial communications requires two channels or frequencies. Full-duplex operation has the advantage of being able to provide communications in both directions at once. |
| Gain: | A general term used to indicate an increase in the signal power in transmission from one point to another. |
| GMSC | Gateway Mobile Switching Center |
| Ground wave: | A radio wave which reaches the receiver by propagation along the Earth's surface rather than through the Earth's upper atmosphere. |
| Group: | Four pre-groups (12 channels). |
| GSM | Global System For Mobile Communication |
| Guard Band: | A narrow band of frequencies left vacant between adjoining channels in a specific radio-frequency transmission band. |
| Half-Duplex: | Operation is similar to simplex except that the direction of transmission can be reversed. This permits two-way communications without the need for a separate channel or frequency each way. The penalty is that the channel or frequency must be shared a nd cannot provide full-time communications in both directions. |
| Half-Power Point: | The two points on a response curve that are 3 dB lower in level than the peak power. Sometimes called the 3 dB bandwidth. |
| Half-Wave Antenna: | An antenna whose length is approximately one-half the wavelength of the signal transmitted or received. It is the most basic type of antenna and consists of two one-quarter wavelength conductors placed end-to-end. The half-wave antenna is also known a s a Dipole or Hertz antenna. |
| Harmonic: | A whole number multiple of a basic or fundamental frequency. |
| Heterodyne (Non-Linear Mixing): | The action of taking two different frequencies and feeding them to a common circuit, e.g. a Non-Linear device, for the purpose of producing new frequencies corresponding to the sum and difference of the two original frequencies. |
| Hexadecimal: | The base-16 number system, using the numerals 0 through 9 and the letters A through F. |
| High-Pass Filter: | A device used to pass all frequencies above a certain frequency while rejecting all frequencies below this frequency. |
| HLR | Home Location Register |
| Horizontal Polarization: | Electromagnetic wave whose electric field is parallel to the Earth's surface. |
| Hybrid System: | A system formed by combining two or more forms of spread spectrum into a single system. The performance of a hybrid system is usually better than can be obtained with a single spread spectrum technique for the same cost. The most common hybrids combin e both frequency hopping and direct sequence techniques. |
| IEMI | International Equipment Mobile Identity |
| IMEI | The IMEI (International Mobile Equipment Identity)is a 15 digit Code used to identify the GSM/DCS/PCS phone to the network. |
| Impedance: | The total opposition offered by a component or circuit to the flow of an alternating current. |
| Independent Sideband: | The use of two Single Sideband channels, one Upper Sideband and the other Lower Sideband, modulated onto a common carrier frequency. This process gives two channels of information being transmitted on the same carrier and the same antenna. |
| Information Source: | Speech or voice, telegraphy (morse), facsimile, teleprinter, television, imagery, or data. |
| Interference: | The impairment by atmospherics, unwanted signals (not known to be deliberate), or the effects of electrical apparatus or machinery. |
| Intermediate Frequency (IF): | In a superheterodyne receiver, the frequency difference obtained when the incoming signal mixes with an internally generated signal. |
| Ionosphere: | That portion of the Earth's atmosphere, beginning about 30 miles above the Earth's surface, which consists of layers of highly ionized gases capable of bending or reflecting certain radio waves back to Earth. |
| IWF | Interworking Function (Modem) |
| Junction Station: | A station in a radio relay network that joins a link or links to the main line. |
| Ki | Individual subscriber authentication key |
| LAI | Location Area Identity |
| Leading Edge: | The major portion of the rise of a pulse. |
| Level: | An expression of relative signal strength at various points in a communication circuit. Measured in decibels (dB's). |
| Line of Sight (LOS): | The straight, unobstructed path between two points. |
| Linear Amplification: | The process by which a signal is amplified without altering the characteristics of the input waveform. Class A, AB, and B amplifiers are generally used for linear amplification. |
| Linear Mixing: | Also called adding. When two or more sinusoidal waves of different frequency are added, a non-sinusoidal or complex wave will result. The following rules apply to linear mixing: |
| 1. At any instant in time, the value of the resultant complex wave is equal to the sum of the instantaneous values of the original components only. | |
| 2. No new frequencies are produced. | |
| 3. All of the original components will still be present in the same phase relationship and proportional amplitude as they were prior to mixing. | |
| 4. None of the components undergo any distortion. | |
| 5. The original components compose the entire wave and can be extracted from the complex wave by appropriate filtering. | |
| Linear Recursive Sequence (LRS): | A pseudorandom binary stream which is the result of the Modulo 2 addition of two or more selected elements of a Shift Register Generator (SRG). The sequence is linear in that the output is directly related to the input, and recursive in that once the f ill length has been reached, the sequence repeats. The output is predictable and deterministic. |
| Link: | The existence of direct communication facilities between two points. |
| Lobe: | Refers to the two or three dimensional polar representation used to indicate the distribution in space of antenna field strength intensities. |
| Local Oscillator (LO): | The oscillator in a superheterodyne receiver. Its output is mixed with the incoming modulated RF carrier signal to produce the IF signal. |
| Low Pass Filter: | A device to pass all frequencies below a certain frequency while rejecting all frequencies above this same frequency. |
| Lower Sideband (LSB): | An inverted replica of the spectrum of the modulating wave. |
| Mark Impulse: | One of the two types of impulses used in teleprinter transmissions; normally, that impulse during which current flows through the teleprinter receiving magnet. The opposite of the space impulse. |
| Master Group: | Five supergroups (300 channels). |
| Maximal Length LRS (L): | Any LRS whose bit sequence equals 2 to the Nth power minus 1 bits in length, where N equals the number of tap points. |
| Meteor Scatter Propagation: | Radio communications in the 50 - 432 MHz range, where contact can be made from 500 - 1300 miles away via reflections from the ionized trails left by meteors as they travel through the ionosphere. The kinetic energy of the meteors, no larger than a pea or a grain of sand, are sufficient to ionize a column of air up to 12 miles long in the E-layer. |
| Microwave: | Radio or radio-relay communications at 1 GHz or higher. |
| Minimum Shift Keying (MSK): | An FSK signal that has a modulations index of .5, in other words its frequency shift is equal to one-half of the keying speed. |
| Mixed Modulation: | The simultaneous use of two types of modulation to increase the information carrying capacity of the carrier. |
| Mixer: | The stage in a superheterodyne receiver in which the incoming modulated RF signal is combined with the local oscillator signal to produce the IF signal. |
| Modem: | A MOdulator/DEModulator device, utilized on both sides of the transmission path, that formats the multiplexed signal for efficient transmission through the channel. |
| Modulated Wave: | A wave which varies in accordance with the amplitude variations of the intelligence. |
| Modulating Wave: | A wave which represents the information and is used to modulate a carrier. |
| Modulation: | The process by which the Amplitude, Frequency, or Phase of a carrier is made to vary according to the amplitude variations of the information. |
| Modulation Factor: | The ratio of peak amplitude variations to the maximum designed variations of the carrier. This factor varies from 0 to 1 decimally. It can never exceed 1. |
| Modulation Index: | The ratio of the frequency deviation of the modulated wave to the frequency of the modulating signal. |
| Modulator: | A circuit or device in which the carrier and modulating signal come together to produce a modulated carrier (modulated wave). |
| MO-SMS | Mobile-Originated Short Message |
| MSC | Mobile Switching Centre - The computer that places the calls, and takes and receives data from the subscriber or from PSTN (Public switched Telephone Network) |
| Multichannel System: | Properly describes a communications system having a capacity of two or more voice-grade channels. |
| Multichannel Radio Relay: | Directional communications between two or more stations, normally situated within line-of-sight distance of each other, with facilities for automatic retransmission of Multichannel Communication Systems to further similar stations. |
| Multiplexing: | Any method of simultaneously transmitting multiple channels of information. |
| Multitone: | See Voice Frequency Telegraphy System. |
| Narrow Band: | A device or circuit that can be operated only over a narrow range of frequencies. |
| Natural Sampling: | A sampling technique whereby an information pulse is generated whenever a coincidence occurs between the modulating signal amplitude level (in terms of time equivalence) and a sampling reference pulse. |
| Network carriers | Also called bearers, these can be any of the existing technologies that wireless providers use, as long as information is provided at the WDP level to interface WAP with the bearer. |
| Non-Linear Mixing: | See Heterodyning. |
| Non-Maximal Length LRS (l): | Any LRS sequence that is less than 2 to the Nth power minus 1 bits in length. |
| Nyquist Interval: | The reciprocal of the sampling rate; equal to the frame length. |
| Nyquist Rate: | In analog-to-digital conversion, the sampling rate that will result in the correct reproduction of the analog signal. This rate is twice that of the highest frequency component of the original analog signal. |
| Nyquist Theory: | For baseband signals which are bandlimited to a frequency of "fm" Hz, we must sample at a rate of "2fm" in order to preserve the information contained in the waveform. |
| Octal: | The base-eight number system, using the numerals 0 through 7. |
| Odd Parity: | Error detection technique in which an extra element is added to the transmitted character so that the overall number of ones in the transmitted character is always odd. |
| Omni-Directional: | An antenna which radiates equal power in all directions in a horizontal plane. |
| OMS | Operation and Maintenance Subsystem of the GSM network |
| Open-Wire Transmission Line: | A transmission line consisting of two spaced parallel wires. |
| Oscillator: | A frequency producing device. |
| Oscilloscope: | A test instrument for showing visually, on the screen of a cathode ray tube, the waveform of a rapidly varying electrical quantity such as an AC current or voltage; it displays an amplitude versus time presentation. |
| Parabolic Reflector: | A reflector (concave shaped parabola) which is placed behind a driven antenna element to provide increased directivity. Also known as a dish antenna. |
| Parity Check: | The addition of special purpose elements to the data, making the number of ones in a group of elements either odd or even. |
| PE | Primary Exchange |
| Peak Amplitude: | The value of the maximum strength (voltage or current) of a wave. |
| Period: | The time required to complete one cycle. |
| Periodic: | A wave that repeats itself at constant regular intervals. |
| Phase: | A measurement of time in terms of degrees or radians; a quantity that specifies a particular stage of progress of a sinewave. Phase is often expressed as an angle in which the complete cycle of operation is equal to 360 degrees (one complete rotation). When two waves pass through corresponding values at the same time, they are said to be in phase. |
| Phase Modulation: | Form of angle modulation in which the phase of the carrier varies by an amount proportional to the amplitude of the modulating wave. |
| Phase Shift Keying (PSK): | A special type of Phase Modulation in which the phase of the carrier is instantaneously shifted between two or more discrete values in order to convey the data. |
| Pilot Tone: | A frequency that is injected onto the multiplexer and is used to control the stability of the system. It is a pure tone and is normally utilized by the receiver's Phase Lock Loop. |
| PIN | Personal Identity Number |
| Polarization: | A statement of the direction of the electric field of a radiated signal with respect to the Earth or some other reference. |
| Post-Detection (Post-D): | The process of recording or analyzing a system or signal after it has been passed through the detection stage of a receiver. |
| Power: | An expression of absolute signal strength at a specific point in a communications circuit. Measured in watts. |
| Pre-Detection (Pre-D): | The process of recording or analyzing a system or signal prior to applying it to the detection stage of a receiver. The signal is converted from RF to IF frequency, but has not been passed through any type of AM or FM detector. |
| Pre-group: | Three Channels |
| Propagation: | The traveling of a wave along a transmission path. |
| PUK | PIN Unblocking Code |
| Pulse: | A momentary sharp change in a current or voltage, followed almost immediately by a sharp return to normal. |
| Pulse Address Multiple Access (PAMA): | Time-frequency pulse patterns are generated and used for addressing. The frequency spectrum is split into bands, and pulses are transmitted in the various bands at pre-assigned times. The pulse pattern, in the time/frequency space, is determined by a pseudorandom binary sequence. |
| Pulse Amplitude Modulation (PAM): | A method of making a series of pulses carry information by causing their amplitude to vary according to the information being transmitted. |
| Pulse Code Modulation (PCM): | A form of digital pulse modulation in which the information is binary encoded and the code then serves as the modulating wave. |
| Pulse Duration (PD): | The time interval between the first and last instants at which the amplitude reaches a stated fraction of the maximum amplitude. Normally measured at 50% of the maximum amplitude. |
| Pulse Excursion: | Sometimes called Pulse Deviation. It is a measurement of the total deviation of the pulse when modulated. |
| Pulse Frequency Modulation: | A method of encoding an information wave by producing a pulse stream whose PRF varies in proportion to the amplitude of the information wave. |
| Pulse Modulation: | Modulation in which intelligence is conveyed by varying some parameter of the transmitted pulses. There are two major types of pulse modulation: Pulse Amplitude Modulation (PAM) and Pulse Time Modulation (PTM). |
| Pulse Period: | The time required to complete one cycle of a pulse, measured from the leading edge of one pulse to the leading edge of the next pulse. |
| Pulse Position Modulation (PPM): | Modulation in which the time position of the pulses making up the modulated pulse train is varied in proportion to the amplitude of the modulating signal. |
| Pulse Repetition Frequency (PRF): | The frequency at which pulses are transmitted by a given system. Usually expressed in pulses per second (pps). |
| Pulse Repetition Interval (PRI): | The time required for one complete pulse cycle or the time from the beginning of one pulse to the beginning of the next pulse. Also, the reciprocal of PRF. |
| Pulse Rate: | See PRF. |
| Pulse Time Modulation (PTM): | A general category of pulse modulation techniques encompassing all methods in which a time parameter of the pulses is varied to convey the information. |
| Pulse Train: | A sequence of pulses. |
| Pulse Width (PW): | Same as Pulse Duration (PD). |
| Pulse Width Modulation (PWM): | Modulation in which a series of pulses carry information by varying the duration of each pulse in accordance with the amplitude of the information being transmitted. Also called Pulse Duration Modulation (PDM). |
| Quadbit: | A group of 4 bits. In Phase Modulation, each quadbit translates to one of 16 specific phases or transitions. |
| Quadrature Amplitude Modulation (QAM): | The process of combining both Phase and Amplitude modulation techniques, where the phase of the carriers of the two AM signals, although having the same frequency, are always 90 degrees out of phase with each other. |
| Quantize: | To divide the range of a variable into a finite number of specific values or steps. |
| Quantizing: | Changing the amplitude levels of a sampled signal to one of several predetermined, discrete, allowable levels. Quantizing is the process by which analog-to-digital conversion is accomplished. |
| Quarter-Wave Antenna: | An antenna whose physical length is approximately one-quarter the wavelength of the signal transmitted or received. The antenna can be electrically grounded, and the ground will act as a mirror for the reflection of the energy that is radiated downward from the antenna. The quarter-wave antenna is also known as a Marconi or "grounded" antenna. |
| Radio Frequency (RF): | Any frequency at which electromagnetic radiation can be used for communications. |
| Radio Relay: | The use of repeaters (relays) as intermediate stations in transmitting communications by radio from one point to another. |
| Radio Spectrum: | The entire range of usable radio frequencies. |
| Radiotelegraphy: | Transmission of telegraphic signals by radio. |
| Radiotelephony: | Transmission of voice signals by radio. |
| Reduced Carrier: | AM method in which part of the power of the carrier is filtered off to the sidebands. |
| Reflection: | A change in direction and phase of a wave when it strikes a reflecting surface (metal, water, earth, etc.); a reversal of image. |
| Refraction: | The bending of a radio wave as it passes through ionospheric layers of different ion density. |
| Repeater: | Equipment which receives, amplifies, and retransmits signals in order to maintain adequate signal strength and intelligence characteristics. |
| Reverse Control Channel | The opposite frequency, 45 MHz lower than the control channel. Used by the mobile. |
| RF Channels: | The number of radio frequencies that may be used with a particular transmitting system. |
| RF Range: | The operating range of a particular system. |
| Ripple: | Pulsating current. Also, the gain depressions that exist in the first portion of a band-pass response curve (above the -3 dB points of the curve). |
| Rise Time: | The time required for a pulse or waveform to reach a specified value from some smaller specified value. For pulses, these values are normally 10% and 90% of the peak amplitude. |
| Sample: | The measurement of the amplitude of an information wave at discrete instants of time and at fixed, regular intervals. |
| Sample Rate: | The number of times the information is sampled in a specified period of time. |
| Saturation: | A condition that exists when a further change in the input produces no additional output (a saturated amplifier). |
| Selectivity: | A measure of the ability of a receiver to accept only a specific band of frequencies. |
| Sensitivity: | A measure of the ability of a receiver to reproduce with satisfactory volume, weak signals received by the antenna. |
| Service Channel: | A VGC modulated directly on the carrier of an FDM system for the purposes of servicing the baseband. |
| Shift Register Generator (SRG): | A series of bi-stable elements connected to Modulo-2 adders. Upon receipt of a clocking pulse, the contents of selected bi-stable elements are Modulo-2 added to provide an input to the SRG and then the contents of all the elements are shifted left or r ight. The resulting binary output will be a LRS. |
| Sideband: | The group of frequencies above or below the main carrier which contain the product of modulation. |
| Simplex: | Operation involving one-way transmissions only. |
| Sinewave: | The graph of an angle that uniformly increases with time. It is a single pure frequency. |
| Single Channel Per Carrier (SCPC): | Each individual channel is independently modulated onto a separate RF carrier. |
| Single Sideband Transmission: | An AM method of radio transmission in which one sideband containing the intelligence is transmitted, but the other sideband is effectively eliminated. The carrier may be full, reduced, or suppressed. This method of transmission is extremely efficient since most of the power in the transmitted signal is in the one sideband containing the information. |
| SMD-PP | Short Message Delivery Point-to-Point |
| SMS | Short Message Service |
| SMSC | Short Message Service Centre |
| SMS-IWMSC | SMS Interworking Mobile Switching Center |
| Space Diversity Reception: | Radio reception involving the use of two or more receiving antennas located several wavelengths apart, feeding individual receivers whose outputs are combined. This system overcomes the problems of multi-path fading because fading affects the spaced an tennas at different instants of time. |
| Space Impulse: | One of two types of impulses used in teleprinter transmission; normally, that impulse during which no current flows through the teleprinter receiving magnet. The opposite of a mark impulse. |
| Spectral Purity: | The relative freedom of an emission from harmonics, spurious signals, and noise. |
| Speech Privacy: | A technique of changing clear speech into a form that is not readily intelligible when it is received through an ordinary receiver. |
| Spreading Sequence: | The pseudorandom sequence (normally an LRS) used to spread the RF carrier in Spread Spectrum signals. For frequency hopping signals, the spreading sequence is a stream of numbers that represent the channels to which the frequency hopper will travel. I n a direct sequence system, the spreading code is a very fast bit stream generated by a digital circuit. |
| Split Channel: | A form of subcarrier modulation in which the VGC is split into two bands. Each band may be used for a different method of communication. You may see any combination of voice, teleprinter, or VFTS. |
| Spurious Frequencies: | Unintentional radiation from a radio transmitter at frequencies outside the normal bandwidth of the transmission. |
| SS7 | Signaling System 7 |
| Static (Quasi-Static): | Rate-of-change of 10 Hz or less. |
| Start/Stop System: | A teleprinter system in which certain elements are used for synchronization purpose to start and stop the receiving printer. |
| Strapping: | Connecting two or more equally spaced channels of a TDM system together to pass one higher speed input signal. Also called Supercommutation. |
| Subcarrier: | A frequency that is modulated by FM, AM, or PM and then modulated onto the RF carrier. |
| Subchannel: | Essentially, a channel within a channel. Subchanneling is the process of taking a channel of an FDM or TDM system and dividing it among several lower speed input rates of information. |
| Subcommutation: | Dividing the time for one channel in a TDM system between two or more lower rates of information. |
| Subharmonic: | A frequency that is an integral submultiple of a frequency to which it is referred. This term is misleading because subharmonic energy cannot be created along with harmonic energy. |
| Subscribers: | Individuals, units, or services to whom any number of channels of a system have been allocated for communications. |
| Supercommutation: | See Strapping. |
| Supergroup: | Five groups (60 channels). |
| Super High Frequency (SHF): | The range of radio frequencies from 3 to 30 GHz. |
| Supermastergroup: | Three Mastergroups (900 channels). |
| Suppressed Carrier: | An AM method of radio transmission wherein the carrier is almost completely filtered off and its power diverted to the sidebands. |
| Synchronization: | The method by which communication systems are made to work or operate at the same rate and exactly together. |
| Synchronous: | A method of synchronization in which data is sent as a continuous, exactly timed stream, with special synchronization information sent only at the beginning of long data blocks. |
| TAP | Telocator Alphanumeric Protocol |
| TCAP | Transaction Capabilities Application Part |
| TDMA | Time Division Multiple Access |
| Terminal Equipment: | Equipment required to receive and reproduce or transmit in usable form, one radio signal. |
| Terminal Station: | A station at the end of a link or network. |
| Time Division Multiplexing (TDM): | The process of transmitting two or more signals over a common path by using time intervals for different signals. |
| Time Division Multiple Access (TDMA): | Accomplished as a time-gating function which correctly locates each terminal transmission burst relative to those of the other terminals. Each terminal is assigned exclusive use of the transponder during specific time slots and the transmissions do not overlap. |
| Time hopping: | The carrier is on-off keyed by a pseudorandom sequence, resulting in a very low duty cycle. The speed of keying determines the amount of signal spreading. |
| Tone Channel Spacing (TCS): | The spacing between center frequencies of the tone channels within a multitone. |
| Traffic Channels: | Voice Grade Channels in a multichannel system. |
| Trailing Edge: | The major portion of the decay of a pulse. |
| Transceiver: | A combined radio transmitter and receiver made as a single unit, generally used for portable or mobile applications. |
| Translation: | The process accomplished by Heterodyning in which a signal at one frequency is moved to a more usable frequency. |
| Transmitter: | The equipment used to generate and amplify an RF signal, add the information to the signal, and then send it out as an RF wave. |
| Tropospheric Scatter: | The process of bouncing signals off of the troposphere, approximately 6 miles above the Earth's surface, for transmissions of up to 500 miles. In practice, only 100-150 mile transmissions are used due to distortion and fading. |
| Ultra-High Frequency (UHF): | The range of frequencies from 300 to 3,000 MHz. |
| Uni-Directional Antenna: | An antenna which radiates or receives in one primary direction. |
| Uniform Sampling: | A sampling technique whereby an information pulse is generated every time a reference pulse is generated. |
| Unmodulated Carrier: | A carrier frequency containing no information. |
| Upper Sideband (USB): | An exact replica of the spectrum of the modulating wave. |
| Vertical Polarization: | Electromagnetic waves whose electric field is perpendicular to the Earth's surface or some other reference. |
| Very High Frequency (VHF): | The range of radio frequencies from 30 to 300 MHz. |
| Vestigal Sideband: | One sideband is attenuated much more than the other with some saving in the bandwidth and transmitted power, normally used in commercial TV. |
| VLR | Visitor Location Register |
| Voice channel | The channel you are assigned by the switch to commence the call on after the exchange of subscriber data. |
| Voice Frequency: | Audio frequencies in the range essential for the transmission of speech of commercial quality, from about 300 to 3400 Hertz. |
| Voice Frequency Telegraphy System (VFTS): | A telegraph system that permits the transmission of several printer signals over one VGC. Also known as multitones of stacked printers. |
| Voice Grade Channel (VGC): | The standard channel referred to in all text or discussions of FDM systems, it extends from 0 to 4000 Hz (4 KHz). This range is sufficient to pass normal voice frequencies plus upper and lower guard bands. |
| WAE | The Wireless Application Environment holds the tools that wireless Internet content developers use. These include WML and WMLScript, which is a scripting language used in conjunction with WML. It functions much like Javascript. |
| Watt: | The unit of electrical power. |
| Wavelength: | The distance traveled in one period or cycle by a wave. It is equal to a constant (the speed of light) divided by the frequency of the wave measured in Hertz. Wavelength is designated by the Greek character Lambda. |
| WDP | The Wireless Datagram Protocol works in conjunction with the network carrier layer (see below). WDP makes it easy to adapt WAP to a variety of bearers because all that needs to change is the information maintained at this level. |
| WSP | The Wireless Session Protocol determines whether a session between the device and the network will be connection-oriented or connectionless. What this is basically talking about is whether or not the device needs to talk back and forth with the network during a session. In a connection-oriented session, data is passed both ways between the device and the network; WSP then sends the packet to the Wireless Transaction Protocol layer. If the session is connectionless, commonly used when information is being broadcast or streamed from the network to the device, then WSP redirects the packet to the Wireless Datagram Protocol layer. |
| WTLS | Wireless Transport Layer Security provides many of the same security features found in the Transport Layer Security (TLS) part of TCP/IP. It checks data integrity, provides encryption and performs client and server authentication. |
| WTP | The Wireless Transaction Protocol acts like a traffic cop, keeping the data flowing in a logical and smooth manner. It also determines how to classify each transaction request: |
| NOTE 1: | The CCITT & CCIR meet periodically to review new FDM, TDM, and modulation techniques and systems and for consultation on designs and suggestions on how they can be improved. |
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