CDMA Glossary N-S

NAM

See Number assignment module.

Neighbor Set

The set of pilots associated with the CDMA Channels that are probable candidates for handoff. Normally the Neighbor Set consists of the pilots associated with CDMA Channels that cover geographical areas near the mobile station. See also Active Set, Candidate Set, and Remaining Set.

Network

A network is a logical subset of the base stations in a cellular system, as identified by a SID. The network is identified by a unique (SID, NID) pair. A network can be as small or as large as needed, but must be totally contained within a single system.

Non-Autonomous Registration

A registration method in which the base station initiates registration. See also Autonomous Registration.

Non-Slotted Mode

An operation mode of the mobile station in which the mobile station continuously monitors the Paging Channel.

ns

Nanosecond (10^-9 second).

Null Traffic Channel Data

One or more frames of 16 '1's followed bu eight '0's sent at the 1200 bps rate. Null traffic channel data is sent when no service option is active and no signaling message is being sent. Null traffic channel data serves to maintain the connectivity between the mobile station and the base station.

Number Assignment Module

A set of MIN-related parameters stored in the mobile station. The NAM encapsulate the mobile station's network identity. Multiple NAMs are sometimes provided in a mobile stations so that, for example, the mobile can have local identities in adjoining service areas. Use of the NAM is not specified in IS-95, beyond identifying those semi-permanent station numeric indicators that should be stored in it [IS-95, Appendix F].

OLC

See Overload class.

Ordered Registration

A registration method in which the base station orders the mobile station to send registration related parameters.

Overhead Message

A message sent by the base station on the Paging Channel to communicate base-station-specific and system-wide information to mobile stations.

Overload Class (OLC)

The means used to control system access by mobile stations, typically in emergency or other overloaded conditions. Mobile stations are assigned one (or more) of sixteen overload classes. Access to the CDMA system can then be controlled on a per class basis by persistence values transmitted by the base station.

Overload Control

A means to restrict reverse analog control channel accesses by mobile stations. Mobile stations are assigned one (or more) of sixteen control levels. Access is selectively restricted by a base station setting one or more OLC bits in the Overload Control Global Action Message.

Paging

The act of seeking a mobile station in order to deliver an incoming call.

Paging Channel

A forward communication channel used by a base station to communication to a mobile station when it is not assigned to a traffic channel.

Parameter-Change Registration

A registration method in which the mobile station registers when certain of its stored parameters change.

Parity Check Bits

Bits added to a sequence of information bits to provide error detection, correction, or both.

Persistence

A probability measure used by the mobile station to determine if it should transmit in a given Access Channel Slot.

Physical Layer

The part of the communication protocol between the mobile station and thebase station that is responsible for the transmission and reception of data. The physical layer in the transmitting station is presented a frame by the multiplex sublayer and transforms it into an over-the-air waveform. The physical layer in the receiving station transforms the waveform back into a frame and presents it to the multiplex sublayer above it.

Pilot Channel

An unmodulated, direct-sequence spread spectrum signal transmitted continuously by each CDMA base station. The Pilot Channel allows a mobile station to acquire the timing of the Forward CDMA Channel, provides a phase reference for coherent demodulation, and provides a means for signal strength comparisons between base stations for determining when to handoff.

Pilot PN Sequence

A pair of modified maximal length PN sequences with period 2¹⁵ used to spread the Forward CDMA Channel and the Reverse CDMA Channel. Different base stations are identified by different pilot PN sequence offsets.

Pilot PN Sequence Offset Index

The PN offset in units of 64 PN chips of a pilot, relative to the zero offset pilot PN sequence.

Pilot Strength

The ratio of received pilot energy to overall received energy. See also E_c/I₀.

PN Sequence.

Pseudonoise sequence. A periodic binary sequence approximating, in some sense, a Bernoulli (coin tossing) process with equiprobable outcomes.

Point to Point Propagation Model

A propagation model in which median transmission loss calculations are based on specific characteristics and terrain profile of the path along the great circle between the transmitter and receiver.

Poisson Blocking Model

Also called Lost Calls Held or Molina model. A mathematical model of telephone traffic blocking in which blocked calls persist for their normal holding time, even though unserviced. It is similar to the Erlang C blocking model, with which it is sometimes confused. The Poisson blocking probability for N resources, callinsity y Erlangs, is

Power Control Bit

A bit sent in every 1.25 ms interval on the Forward Traffic Channel to signal the mobile station to increase or decrease its transmit power.

Power Control Group

A 1.25 ms interval on the Forward Traffic Channel and the Reverse Traffic Channel. See also Power Control Bit.

Power-Down Registration

An autonomous registration method in which the mobile station registers on power-down.

Power-Up Registration

An autonomous registration method in which the mobile station registers on power-up.

Privacy

Protection of traffic by means of encryption or other means specifically applied for that purpose.

Propagation Loss

The total reduction in radiant power density between the transmitting antenna and the receiving antenna. Propagation loss includes both spreading (free space diffraction) loss and attenuation loss. For non-line of sight situations it also includes diffraction loss around obstacles. It does not include antenna gain or feeder loss. Sometimes called isotropic propagation loss.

Rayleigh Distribution

The single-parameter probability distribution given by

or the equivalent density

Rayleigh Fading

The deep fading process characteristic of narrowband radio signals in a severe multipath propagation environment. The probability distribution of complex amplitude tends toward a bandlimited Gaussian, which has a Rayleigh distribution of amplitude. Cf. Flat Fading, Frequency Selective Fading, Ricean Fading.

Receive Objective Loudness Rating (ROLR)

A perceptually weighted transducer gain of telephone receivers relating electrical excitation from a reference generator to sound pressure at the earphone. The receive objective loudness rating is normally specified in dB relative to one Pascal per millivolt. See IEEE Standard 269-1992, IEEE Standard 661-1979, ITU-T Recommendations P.76 and P.79.

Registration

The process by which a mobile station makes its presence known to a base station to facilitate call delivery.

Registration Zone

A collection of one or more base stations treated as a unit when determining whether a mobile station should perform zone-based registration.

Release

A process that the mobile station and base station use to inform each other of call disconnect.

Reverse CDMA Channel

The CDMA Channel from the mobile station to the base station. From the base station's perspective, the Reverse CDMA Channel is the sum of all mobile station transmissions on a CDMA frequency assignment.

Reverse Traffic Channel

A Reverse CDMA Channel used to transport user and signaling traffic from a single mobile station to one or more base stations.

Rice (or Rician) Distribution

The probability distribution of the amplitude of a signal composed of a steady component plus independent IID quadrature Gaussian processes. It is applicable when a signal arrives at a receiver by both a line of sight path and by multiple indirect paths. This two-parameter distribution can be represented as

where I₀ is the modified Bessel function of the first kind and order zero and a is the amplitude of the steady component. Note that this reduces to a Rayleigh distribution for a = 0.

Rician Fading

The fading process characteristic of radio signals when there is a strong line-of-sight signal path and multiple non-direct signal paths. The probability distribution of complex amplitude tends toward a bandlimited Gaussian with a nonzero mean, which has a Rician distribution of amplitude. Cf. Rayleign Fading, Flat Fading, Frequency Selective Fading.

Roamer

A mobile station that is operating in a cellular system other than its home system.

ROLR

See Receive Objective Loudness Rating.

Sector

Normally one angular segment of the coverage area of a cell, served by one base station. Also used to denote any non-traditional partitioning of the service area, such one strand of a cable-based delivery system.

Service Option

A specific type of user traffic supported by a cellular system. The major service options are speech codecs, facsimile, and various types of data. Service options may be negotiated between base and mobile stations during call setup.

Serving MSC

The MSC which currently has the mobile station obtaining service at one of its cell sites within its coverage area.

Shared Secret Data (SSD)

A bit pattern stored in the mobile station and known by the base station. SSD is used to support the authentication procedures and voice privacy. Shared Secret Data is maintained during power off.

Signal-to-Noise Ratio (SNR)

The dimensionless ratio E_b/(N₀+I₀), or energy per bit divided by the noise-plus-interference power spectral density. It is usually stated in dB.

Signaling

The information exchanged between the mobile station and the network, or within the network, for the purposes of service provision (e.g., connection establishment).

Slot Cycle

A periodic interval at which a mobile station operating in the slotted mode monitors the Paging Channel.

Slotted Mode

An operation mode of the mobile station in which the mobile station monitors only selected time slots on the Paging Channel when in the Mobile Station Idle State. The primary purpose of slotted mode is power conservation.

SNR

See Signal to Noise Ratio.

Soft Handoff

A handoff occurring while the mobile station is in the Mobile Station Control on the Traffic Channel State. This handoff is characterized by commencing communications with a new base station on the same CDMA frequency assignment before terminating communications with the old base station. Cf. Hard Handoff.

Symbol

See Code Symbol.

System Identification (SID)

A number uniquely identifying a cellular system.

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