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Cellular Telecommunications Glossary [O - S]

- a glossary of terms used with cell phone or cellular telecommunications technology

Glossary pages: [ 0 - 9 ] , [ A - C ] , [ D - F ] , [ G - J ] , [ K - N ] , [ O - S ] and [ T - Z ]

OQPSK - Offset Quadrature Phase Shift Keying.
A form of quadrature phase shift keying where the quadrature (Q) component of the signal is offset from the in-phase (I) component by half a symbol period. As a result the amplitude does not cross zero, and this reduces the peak to average ratio. This has advantages for power amplifiers because it reduces the peak to average ratio and as a result it is used in the reverse link for CDMA transmissions.
Orthogonality -
This is a property of codes that can be used as spreading codes for direct sequence spread spectrum (DSSS) transmissions. Codes are said to be orthogonal if they sum to zero over a period of time. Orthogonal codes are used for DSSS transmissions because they do not interfere with one another.
Packet Switched Data -
Data transmitted from multiple users in individually addressed discrete packets. By using packet data, channels can be used for transmissions from multiple users, thereby improving efficiency.
Paging Channel -
The channel used in GSM and CDMA that is used by the base station to transmit a message to a mobile to indicate that there is an incoming message. The mobile monitors this channel while it remains "idle".
PDC - Pacific, or Personal Digital Cellular.
The TDMA system based on NA-TDMA that is used exclusively in Japan.
PDE - Position Determining Entity.
The area with in a cellular network that is used to determine the position of a mobile for applications such as 911 calls. It will be associated with techniques such as A-GPS, AFLT, etc.
Pilot Channel.
The channel used in CDMA for initial timing and BTS location.
PLMN - Public Land Mobile Network.
The wire side of a communications network.
PN Code - Pseudonoise Code.
A binary sequence that exhibits random noise-like properties. PN codes or sequences can be distinguished from random sequences because the pseudo-random sequence repeats after a given time, i.e. it exhibits periodicity.
PPP - Point-to-Point Protocol.
A protocol used to connect a computer to the Internet when using a standard dial-up telephone line. PPP is also used when transmitting data in a cellular network.
PSK - Phase Shift Keying.
A form of modulation where the phase of the signal is altered to carry the information to be transmitted.
PSTN - Public Switched Telephone Network
The land line based or wired telephone system.
QCELP - Qualcomm Code Excited Linear Prediction.
A voice encoder scheme that is used in CDMA systems and that was developed by Qualcomm.
QPSK - Quadrature Phase Shift Keying.
It may also be known as quaternary or quadriphase phase shift keying and it is a form of phase shift keying modulation that has four states, usually at 0, 90, 180, and 270 degrees.
Rake -
This is a technique used in digital signal processing where the radio receiver is given uses several base-band correlators. The technique uses the fact that a signal will propagate via several paths to a receiver. The signals arriving via different paths will reach the receiver at different times because of the different path lengths. Using the Rake process all the components can be individually processed and then combined to provide improved performance.
RAN - Radio Access Network.
The portion of a mobile phone network that relates to the transmission or radio communications between the terminal device and the network base station.
RAT - Radio Access Technology.
The technology or system used for the cellular system. GSM and UMTS are two different radio access technologies.
Reverse link -
The path from the mobile handset or terminal to the base station. This term is normally associated with cdmaOne (IS-95) and CDMA2000 (IS-2000) networks.
RLP - Radio Link Protocol.
A protocol used over the air interface.
RTT - Radio Transmission Technology.
The transmission technology used, in this context, by a cellular telecommunications system. It is used particularly in the context of CDMA2000 where 1XRTT and 3XRTT are used.
RUIM - Removable User Identity Module.
A card used in CDMA cell phones that stores the information to identify the caller to the network. It is the equivalent of the SIM card used on GSM phones.
SIM - Subscriber Identity Module.
A card commonly used in GSM phones that store data that identifies the caller to the network service provider. It also provides many other functions including the ability to store phone book numbers etc.
SMS - Short Message Service.
This is a system that enables short text messages of up to 160 characters to be sent and received via the network operator's message centre. It is also possible to send messages from the Internet, using a so-called "SMS gateway" website. It was first introduced on GSM.
Soft Handover -
A form of handover applicable to CDMA networks (including W-CDMA) where the mobile changes its PN spreading code when handing over from one base station to the next while the frequency channel remains the same.
Softer Handover -
A form of handover applicable to CDMA networks where the system hands over from one sector of a base station to another using a different spreading code. As it is less complicated than soft handover it is given the name, softer handover.
Spread Spectrum -
A method of transmitting a radio signal by spreading it over a wide range of frequencies. Direct sequence spread spectrum (DSSS) in the form of CDMA is used as a cellular telecommunications access technology. Another form of spread spectrum transmission is frequency hopping where the signal moves from one frequency to another, remaining in one place for only a short time.

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