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CDMA Glossary A-F

Access Attempt
A sequence of one or more access probe sequences on the Access Channel containing the same message. See also access probe and access probe sequence.

Access Channel
A Reverse CDMA Channel used by mobile stations for communicating to base stations . The Access Channel is used for short signaling message exchanges such as call originations, responses to pages, and registrations.

Access Channel Message
The information part of an access probe conssiteing of the message body, length field, and CRC.

Access Channel Preamble
A sequence of all-zero frames sent at the 4800 bps rate preceeding an Access Channel message. It aids the base station receiver in detecting and syncronizing the Access Probe.

Access Channel Request Message
An Access Channel message that is autonomously generated by a mobile station.

Access Channel Response Message
An Access Channel message that is generated to reply to a message received from a base station.

Access Channel Slot
The assigned time interval for an access probe. An access channel slot consists of an integer number of frames. The transmission of an access probe is performed within the boundaries of an Access Channel slot.

Access Probe
One Access Channel transmission consisting of a preamble and a message. The transmission is an integer number of frames in length and carries one Access Channel message.

Access Probe Sequence
A sequence of one or more access probes. The transmitted power escalates during an access probe sequence from a prescribed minimum power until acknowledged by the base station, or until a presribed maxixum power is reached. One or more repetitions of an access probe sequence constitute an access attempt.

A link layer response by a mobile station or a base station confirming that a signaling message was received correctly.

Action time
The time at which an action implied by a signaling message should take place.

Active set
The set of pilots associated with the CDMA Channels containing Forward Traffic Channels assigned to a particular mobile station.

A mechanism through which the mobile station maintains in its Neighbor Set the pilots that have been recently sent to it from the base station and the pilots whose drop timers have recently expired.

A concealed 64-bit pattern stored in the mobile station. It is used to generate and update the mobile station's shared secret data, which is used for authentication. See also authentication and shared secret data.

Analog Paging Channel
A forward analog control channel that is used to page mobile stations and send orders.

Analog Voice Channel
A channel on which a voice conversation occurs and on which brief digital messages may be sent from a base station to a mobile station or from a mobile station to a base station.

Application Layer
The application layer of the IS-95 air interface provides control of the cellular telephone system. Signaling messages originate and terminate at the application layer. See also Layering, Physical layer and Link layer.

Area Propatation Model
A propagation model in which median transmission loss calculations are based on generalized characteristics of the area surrounding the transmitter and receiver, as well as the intervening area. Features such as local environment, terrain roughness, building density are used to modify a median transmission loss equation in order to adopt it to the service area.

A procedure used by base stations to validate a mobile station identity at system access and other times, and by mobile stations to validate a base station identity when ordered to update the shared secret data.

Autonomous Registration
A method of registration in which the mobile station registers without an explicit command from the base station.

Base Station
A fixed station used for communicating with mobile stations. Depending upon the context, the term base station may refer to a cell, a sector within a cell, an MSC, or other part of the cellular system. It is sometimes used loosely in the standards to mean any land side functionality. See also Mobile Switching Center.

BCH Code
See Bose-Chaudhuri-Hocquenghem Code.

See bit error rate.

Bose-Chaudhuri-Hocquenghem Code (BCH Code)
A large class of error-correcting cyclic codes. For any positive integers m, m > 3, and t < 2m-1, there is a binary BCH code with a block length n equal to 2m - 1 and n - k < mt parity check bits, where k is the number of information bits. The BCH code has a minimum distance of at least 2t + 1.

Bit Error Rate (BER)
Numerically equal to the number of errored bits divided by the total number of bits. Care should be taken when reporting or interpreting "bit error rate" in systems that use encapsulated data or otherwise add overhead to the payload bits. It is normally not meaningful in the CDMA context because whole frames are erased, or not, according to the result of the frame quality check. See Frame Error Rate and Message Error Rate.

Blank and burst
The pre-emption of an entire Traffic Channel frame's primary traffic by signaling traffic or secondary traffic.

Failure of a telecommunication system to provide service in response to a call attempt. Blocking in a CDMA system can be due to hard causes, such as lack of a necessary resource, or to soft causes, such as excessive interference in an air interface.

Bits per second.

Calling rate
The number of originations per unit time in a designated service area. See also Erlang load.

Candidate set
The set of pilots that have been received by the mobile station with sufficient strength to be successfully demodulated, but have not been placed in the Active Set by the Base station. See also Active Set, Neighbor Set, and Remaining Set.

See Code Division Multiple Access.

CDMA Channel
The set of channels transmitted between the base station and the mobile stations within a given CDMA frequency assignment. See also Forward CDMA Channel and Reverse CDMA Channel.

CDMA Channel Number
An 11-bit number identifying the center of the CDMA frequency assignment.

CDMA Frequency Assignment
A 1.23 MHz segment of spectrum centered at a discrete frequency identified by the CDMA channel number. The allowable channels are centered on one of the 30 kHz channels of the AMPS system.

Loosely, one or more collocated base stations. They can service different angular sectors, different frequencies, or both.

Cell Site
The physical location of a cell's radio equipment and supporting systems. This term is also used to refer to the equipment located at the cell site.

See Code Excited Linear Prediction

Informal term used to refer to either a binary element of a spreading sequence, or to the time interval that it occupies, or 1/1.2288 MHz = 813.8 ns, or, at the speed of light, a distance of c/f = (0.3 m/ns)/1.2288 MHz = 244.1 meters.

Channel Coder
A device that adds redundancy to digital data before transmission for the purpose of reducing the end-to-end error rate. See also Convolutional Coder.

Channel Decoder
A device that performs error correction on coded data by exploiting the redundancy introduced by the channel coder. See also Viterbi Decoder.

A fraudulent subscriber station created by copying a MIN-ESN pair from a legitimate subscriber's over-the-air transactions.

Code Channel
One of the orthogonal subchannels of a CDMA Forward CDMA Channel. Code channel zero is the pilot channel. Code channels 1 through 7 may be assigned to either Paging Channels or Traffic Channels. Code channel 32 may be assigned to either the Sync Channel or to Traffic Channels.

Code Division Multiple Access
A technique for spread-spectrum multiple access digital communication that creates channels through the use of noise-like carrier waves.

Code Excited Linear Prediction (CELP)
A technique of voice coding that makes use of linear prediction filters excited by a stimulus looked up from a pre-stored table, based on its similarity to the residue from the LPC filter solution.

Code Symbol
A symbol from a finite alphabet that is the output of an error-correcting-code encoder. Information bits enter the encoder and code symbols leave the encoder. The alphabet may be binary, or may have larger dimensionality.

A combination of encoder and decoder, frequently used in the context of speech codec, meaning both components of the speech coding and decoding process, operating in full duplex mode.

Convolutional Code
An error-correcting code that is generated by finite-field division of the data sequence, regarded as a polynomial over a finite field, by a generator polynomial. Such a division resembles a discrete convolution.

Coverage Area
A geographical area in which a mobile will receive satisfactory signal-to-noise ratio (Eb/N0) in both forward and reverse links. Evaluation of coverage for a CDMA system must take into account the effects of soft handoff and multipath, as well as signal strength.

See Cyclic Redundancy Code.

Cyclic Redundancy Code (CRC)
A class of linear error detecting codes that generate a parity check bits as the remainder of a polynomial division of the data, regarded as a polynomial, by a generator polynomial. They are often based on a BCH code, used only for its error detection capability.

Data Burst Randomization
The pseudo-random process that determines which power control groups are transmitted by a mobile station when its transmitted bit rate is less than full rate.

The ratio, in dB, of the sideband power of a signal, measured in a given bandwidth at a given frequency offset from the same signal, to the total power of the signal. For a CDMA signal, the signal power is measured in a 1.23 MHz bandwidth.

Power measured in dB relative to one milliwatt.

Power measured in dB relative to one Watt.

The process of unpermuting the symbols that were permuted by an interleaver.

The process by which primary rate traffic is forced to a lower-than-maximum rate and transmitted together with signaling or secondary traffic in the same frame.

Distance-Based Registration
An autonomous registration method in which the mobile station registers whenever it enters a cell whose distance from the cell in which the mobile station last registered exceeds a given threshold.

Guiding of electromagnetic radiation by refraction due to index gradients in the atmosphere.

The energy of an information bit. Eb is measured in Joules, or equivalently in Watts per Hertz.

Effective Antenna Elevation (Base Station)
The height of the radiation center of the base station antenna above the average elevation of the ground midway between the base station and the mobile. Particular ranges of distance are invoked by the Federal Communications Commission to define height above average terrain (HAAT) for various services.

Effective Antenna Elevation (Mobile Station)
The height of the radiation center of the mobile station antenna above the ground.

Effective Isotropic Radiated Power (EIRP)
The transmitted power multiplied by the antenna gain referenced to an ideal isotropic radiator. EIRP is larger that ERP in the same direction by the gain of an ideal dipole relative to an isotropic radiator, which is 2.1 dB.

Effective Radiated Power (ERP)
The transmitted power multiplied by the antenna gain referenced to a half-wave dipole.

See Effective Isotropic Radiated Power.

Electronic Serial Number (ESN)
A 32-bit number assigned by the mobile station equipment manufacturer, uniquely identifying the mobile station equipment.

Encoder Tail Bits
Fixed value bits appended to a block of data in order to flush a convolutional encoder so that it is left in a known state. Leaving the encoder in a known state aids the decoding.

A dimensionless unit of telephone traffic intensity. It is numerically equal to the calling rate times the average holding time. It is named for the Norwegian telephone engineer who first popularized the concept.

Erlang B
Also called Lost Calls Cleared model. A mathematical model of telephone traffic blocking in which blocked calls are not queued. The Erlang B blocking probability for N resources, calling intensity y Erlangs, is

Cf. Erlang C Model and Poisson Blocking Model.

Erlang C
Also called Lost Calls Delayed model. A mathematical model of telephone traffic blocking in which blocked calls are queued. It is similar to the Poisson Blocking Model, with which it is sometimes confused. The Erlang C blocking probability for N resources, calling intensity y Erlangs, is

(Need to figure out Erlang C Formula!)

See Effective Radiated Power.

See Electronic Serial Number.

Fade Timer
A timer kept by the mobile station as a measure of Forward Traffic Channel continuity. If the fade timer expires, the mobile station drops the call.

See Forward Error Correction

See Frame Error Rate

An indication sent on a CDMA Traffic Channel indicating that the user directed the mobile station to invoke special processing.

Flat Fading
Radio signal fading characteristic of a multipath environment where the delay spread is less than the reciprocal bandwidth of the signal. Under these circumstances the fading is uniform across the bandwidth of the signal, and thus is essentially just an amplitude change. Also known as frequency-independent fading. Cf. Frequency Selective Fading, Rayleigh Fading, Ricean Fading.

Foreign NID Roamer
A mobile station operating in the same system (SID) but a different network (NID) from the one in which service was subscribed. See also Foreign SID roamer.

Foreign SID Roamer
A mobile station operating in a system (SID) other than the one in which service was subscribed. See also Foreign NID roamer.

Forward CDMA Channel
A CDMA Channel from a base station to mobile stations. The Forward CDMA Channel comprises one or more code channels that are transmitted on a CDMA frequency assignment using a particular pilot PN offset. The code channels are associated with the Pilot Channel, Sync Channel, Paging Channels, and Traffic Channels. The Forward CDMA Channel always includes a Pilot Channel and may include a Sync Channel, up to seven Paging Channels, and up to 63 Traffic Channels. The total number of code channels, including the Pilot Channel, cannot exceed 64.

Forward Error Correction (FEC)
A technique for improving performance of a digital communication channel that applies an error-correcting code in the transmitter and performs correction in the receiver without feedback to the transmitter. "Forward" here refers to the lack of feedback, not the transmission direction.

Forward Traffic Channel
A code channel used to transport service option (usually voice) and signaling traffic from the base station to the mobile station.

A basic timing interval in a CDMA system. For the Access Channel, Paging Channel, and Traffic Channels, a frame is 20 ms in duration. For the Sync Channel a frame is 80/3 = 26.666 ms in duration.

Frame Category
A classification of a received Traffic Channel frame based upon transmission data rate, the frame contents (primary traffic, secondary traffic, or signaling traffic), and whether there are detected errors in the frame.

Frame Erasure Rate
Ratio of erased frames to total frames. Care should be used to distinguish between frame erasure rate and frame error rate. They are similar, but not identical. Erased frames usually are counted as errored frames, but not all errored frames are erased, that is, some may be undetected by the receiver.

Frame Error Rate (FER)
Ratio of errored frames to total frames. For purposes of this calculation, erased frames count as errored.

Frame Offset
A time skewing of Traffic Channel frames from System Time in integer multiples of 1.25 ms. The maximum frame offset is 18.75 ms.

Frame Quality Indicator
The CRC check applied to 9600 bps and 4800 bps Traffic Channel frames.

Frequency Selective Fading
Radio signal fading characteristic of a multipath environment where the delay spread is greater than the reciprocal bandwidth of the signal. Under these circumstances the fading is non-uniform across the bandwidth of the signal. The multipath produces deep notches in the spectrum, and thus strong distortion of the time-domain signal shape. Cf. Flat Fading, Rayleigh Fading, Ricean Fading.

Fresnel Radius
The radius r of the circle formed by the intersection of the first Fresnel zone with a plane perpendicular to the line of sight between the transmitting and receiving antennas. In meters it is given by

Fresnel Zone
1. The region in space between successive ellipsoids of revolution whose foci are the transmitting and receiving antennas. The ellipsoids are defined as the locus of points such that the sum of distances to the transmitting and receiving antennas differs from the line-of-sight distance by an interger number of half-wavelengths.

2. The area formed by the intersection of the regions of definition 1 with a plane perpendicular to the line of sight between the transmitting and receiving antennas.

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Copyright © 1996-1999 Arthur H. M. Ross, Ph.D., Limited