Glossary of Terms

- A -
A-Interface	The network (air) interface between a Mobile End System (M-ES) and the Cellular Digital Packet Data (CDPD)-based wireless packet data service provider network.
access control	A network function that determines whether a particular mobile device is permitted to access the network.
accounting	A network function that tallies the usage of various network resources.
accounting collector	Responsible for the storage and processing of accounting information received from accounting distributors.
accounting distributor	Responsible for receiving information from accounting meters or other distributors, and distributing that information to accounting collectors or other distributors.
accounting meter	Performs measurements and aggregates the results of those measurements (i.e., into an accounting traffic matrix).
accounting traffic matrix	A traffic matrix is a collection of information, gathered over a period of time, containing statistics on Mobile End System (M-ES) registration, de-registration, and Network Protocol Data Unit (NPDU) traffic.
acquisition	The process by which a Mobile End System (M-ES) locates a Radio Frequency (RF) channel carrying a channel stream, synchronizes to the data transmissions on that channel stream, and determines whether the channel stream is acceptable to the M-ES for network access.
adaptive retransmission algorithms	Used by self-adjusting timers to determine and dynamically set timers to effectively adjust data traffic in the event the link is slower than usual due to congestion or other network conditions.
adjacent cell	Two cells are adjacent if it is possible for a Mobile End System (M-ES) to maintain continuous service while switching from one cell to the other.
adjacent MD-IS	Two Mobile Data Intermediate Systems (MD-ISs) are adjacent if each MD-IS controls one of a pair of adjacent cells.
Administrative Domain	The subscriber administration, billing administration, and network management functions over which each network service provider has control and responsibilities.
Advanced Mobile Phone System (AMPS)	The North American analog cellular phone system. The spectrum allocated to AMPS is shared by two cellular phone companies in each area or region (geographic market). This system was deployed during the 1980s and today it and its variants represent nearly 85% of the cellular voice systems installed throughout the world.
airlink	The physical layer radio frequency channel pair used for communication between the Mobile End System (M-ES) and the Mobile Data Base Station (MDBS).
airlink interface	The Cellular Digital Packet Data (CDPD)-based wireless packet data service provider's interface for providing services over the airlink to mobile subscribers.
allocated channel	A Radio Frequency (RF) channel that is configured to allow use by Cellular Digital Packet Data (CDPD) transmissions.
AMPS	See Advanced Mobile Phone System.
analog signal	A continuously variable waveform (such as a sound wave) that can represent an infinite number of values; wireline telephone systems use analog signals to provide voice communication. The term "analog" is used to refer to telephone transmission and/or switching that is not digital. Analog signals are amplified rather than regenerated.
ANSI	American National Standards Institute. A group that certifies organizations developing US standards for the information processing industry. ANSI accredited groups participate in defining network protocol standards.
API	Application Program Interface.
Application Entity	An Application Entity provides the service desired for communication. An Application Entity may exist in an M-ES (Mobile End System) (i.e., mobile application entity) or an F-ES (Fixed End System). An Application Entity is named with an application entity title.
Application Layer	Layer 7 in the Open Systems Interconnect (OSI) 7-Layer Network Layer Reference Model. Provides protocols and services required by particular user-designed application processes. Functions pertaining to particular user requirements and application service elements that can be used by more than one application are contained in this layer.
application program interface (API)	The interface between the subscriber unit and the multiple application subsystem. Generally consists of simple commands such as "open a connection." These commands are translated by the enabling layer into commands that either control the network connection or communicate data across the network.
application services	Telecommunications services that provide value-added features not related to the provision of communications facilities.
ARDIS	A wireless packet-switched network for public data communications, jointly owned by Motorola and IBM, that allows people carrying handheld devices to send and receive short data messages.
Area Color Code	A color code that is shared by all cells controlled through a single Mobile Data Intermediate System (MD-IS). The value of the Area Color Code must be different between any two adjacent cells controlled by adjacent MD-ISs. Refer to color code.
ARN	Authentication Random Number.
ARP	Address Resolution Protocol. An Internet protocol that runs on Ethernet and all IEEE 802.X Local Area Networks (LANs), and maps Internet addresses to Medium Access Control (MAC) addresses.
ARQ	Automatic Repeat reQuest.
AS	Autonomous System. A collection of gateways (routers) under a single administrative authority using a common interior gateway protocol for routing packets.
ASCII	American Standard Code for Information Interchange.
ASN	Authentication Sequence Number.
ASN.1	Abstract Syntax Notation One. A specification language used to define interoperable interfaces, based on standard application layer protocols such as Message Handling System (MHS) or Common Management Information Protocol (CMIP).
asynchronous	Literally, not synchronous. A method of data transmission that allows characters to be sent at irregular intervals by preceding each character with a start bit, and following it with a stop bit.
Asynchronous Transfer Mode (ATM)	ATM is the technology selected by the Consultative Committee on International Telephone & Telegraph (CCITT) international standards organization in 1988 for creating a Broadband Integrated Services Digital Network (B-ISDN). It is a fast, cell-switched technology based on a fixed-length 53-byte cell.
AT Command Set	Also known as the Hayes standard AT command set. A language that enables PC communications software to control an asynchronous and "Hayes-compatible modem." Called "AT" because all the commands begin with "AT," which is short for ATtention.
authentication	The process by which a network validates that the user or address is legitimate. It is also the process whereby users of an information source prove they are who they claim to be.
authentication credentials	Information submitted by a network element to allow validation by its peer entity. In the CDPD network, authentication credentials for each NEI consists of an Authentication Sequence Number and an Authentication Random Number.
Authentication Random Number	A random value used in authentication procedures.
Authentication Sequence Number	A sequence count that is incremented for each change of Authentication Random Number (ARN).
available channel	In the CDPD system, a Radio Frequency (RF) channel is available if it is an allocated channel that is not currently in use for either Cellular Digital Packet Data (CDPD) or non-CDPD-based wireless packet data service.
- B -
backbone	The backbone is the part of the communications network that interconnects Local Area Networks (LANs) together inside a building or across a city or country. LANs are connected to the backbone via bridges and/or routers and the backbone serves as a communications highway for LAN-to-LAN traffic. A backbone can be a LAN, a Wide Area Network (WAN), or a combination of both dedicated to providing connectivity between subnetworks in an Enterprise-wide network.
bandwidth	The bandwidth determines the rate at which information can be sent through a channel: the greater the bandwidth, the more information can be sent in a given amount of time.
base stations	Refer to Mobile Data Base Station (MDBS).
Base-Controlled Hand-off	Cell transfers managed by and initiated from the network, typical of Advanced Mobile Phone Systems (AMPS).
BCHO	Base-Controlled Hand-Off.
BIS	Border Intermediate System.
bit stream	A continuous stream of data bits transmitted over a communications line with no breaks or separators between the characters.
bit time	The time period for the transmission of one bit by the physical layer. For the 19,200 bps CDPD airlink data channel, this is equal to 52.08333 microseconds.
blank and burst	On the AMPS telephone network, certain administrative messages are sent on the voice channel by blocking the voice signal (blanking) and sending a short high speed data message (burst). The blank and burst technique is one that causes a momentary dropout of the audio connection (and sometimes disconnection of cellular modem connections) when a power level message is transmitted to the cellular phone.
BLER	Block Error Rate.
block	In Cellular Digital Packet Data (CDPD), a block is a Reed-Solomon code block, consisting of 63 6-bit symbols, 47 of which are data symbols and 16 of which are forward error correcting parity symbols.
Block Error Rate (BLER)	An averaged estimate of the ratio of transmitted blocks that contain an uncorrectable number of symbol errors to the blocks received successfully.
bps (bits per second)	A measure of data transmission speed.
broadband personal communications standards (PCS)	Consists of 120 MHz of new spectrum available for new cellular networks. Also known as wideband PCS.
broadcast	A transmission in one or more channel streams that is intended to be processed by all Mobile End Systems (M-ES) using the channel stream.
burst	Generally refers to the reverse channel transmissions by the Mobile End System (M-ES). Each transmission is a reverse channel transmission "burst." Can also refer to a "burst error," in which several consecutive symbols are corrupted.
busy state	A channel stream is in a busy state if the Mobile Data Base Station (MDBS) signals in the busy/idle flag that a Mobile End System (M-ES) is currently transmitting on the channel.
busy/idle flag	An indicator that is transmitted by the Mobile Data Base Station (MDBS) periodically to indicate whether the reverse channel is currently in the busy state or the idle state.
- C -
CCITT	Consultative Committee for International Telegraph and Telephone. Now known as the International Telecommunications Union- Telecommunications Systems (ITU-TS).
CDMA	Code Division Multiple Access. Defines how a single channel can be allocated to support multiple users simultaneously.
CDPD	Cellular Digital Packet Data.
CDPD cell boundary	The locus of points at which a Mobile End System (M-ES) should no longer access service by using the transmissions of a particular cell.
CDPD Forum	An industry trade association supporting the development of the Cellular Digital Packet Data (CDPD) commercial marketplace.
CDPD SNDCP	Cellular Digital Packet Data (CDPD) SubNetwork Dependent Convergence Protocol.
Cell	The geographic region in which Radio Frequency (RF) transmission from one fixed transmission site can be received at acceptable levels of signal strength using an omnidirectional or a directional antenna. In a cellular network, a cell represents a geographic area within which a particular bandwidth of radio frequency channels can be received at adequate signal strength.
Cell Group Color Code	A color code assigned to a set of cells. Each member of the set is adjacent to at least one other member of the set and no two members of the set are allocated the same Radio Frequency (RF) channel for Cellular Digital Packet Data (CDPD) use. Each cell is assigned exactly one Cell Group Color Code.
cell site	The physical building that houses the cellular telephone base station or the CDPD Mobile Data Base Station (MDBS).
cell transfer	The procedure of changing the channel stream in use to a channel stream originating at a different cell.
Cellular Digital Packet Data (CDPD)	A wide-area, wireless data networking technology. CDPD is an open standard for using existing cellular networks for wireless data transmission. Packets of data are sent along channels of the cellular network.
cellular modems	A device that combines data modem and cellular telephone transceiver technologies in a single unit. This allows a user to transfer data on the cellular network without the use of a separate cellular telephone.
CGSA	Cellular Geographic Service Area.
channel	A 30 kHz cellular voice channel. A voice-grade transmission facility with defined frequency response, gain, and bandwidth. Also, a path of communication, either electrical or electromagnetic, between two or more points. Also, channel is used to describe the distribution path into the market for value-added resellers.
channel bandwidth	The frequency range of a Radio Frequency (RF) channel-in Cellular Digital Packet Data (CDPD), 30 kHz.
channel hopping	The process in CDPD of changing the Radio Frequency (RF) channel supporting a CDPD channel stream to a different RF channel on the same cell. This is typically used to avoid collisions with voice traffic use of the RF channel.
channel stream	A shared digital communications channel between a Mobile Data Base Station (MDBS) and a set of Mobile End Systems (M-ESs) considered as a logical concept, separate from the frequency of the Radio Frequency (RF) channel used to implement the channel at any given time.
circuit	The physical connection (or path) of channels, conductors and equipment between two given points through which an electric current may be established. Includes both sending and receiving capabilities.
circuit switched	The process of setting up and keeping a circuit open between two or more users, such that the users have exclusive and full use of the circuit until the connection is released.
CLNP	Connectionless Network Protocol.
CLNS	Connectionless Network Service.
clone	A mobile device, typically a cellular telephone, that claims to possess the same address identifier as another mobile device.
CMIP	Common Management Information Protocol [CCITT-X.711].
CMIS	Common Management Information Service [CCITT-X.710].
CMISE	Common Management Information Service Element.
co-channel interference	Interference between signals transmitted in a given Radio Frequency (RF) channel in a particular cell and signals transmitted on the same RF channel in a different cell. A receiver that is in a position to receive from both cannot filter out the undesired signal, and consequently the noise level at the receiver increases.
code division multiple access (CDMA)	Defines how a single channel can be allocated to support multiple users simultaneously so that all mobile users transmit on the same frequency with different pseudo-random signals. Originally developed to support voice. One of two digital cellular standards in the US.
code word	When used in the context of the Reed-Solomon encoding, it refers to the 63 6-bit symbols (378 bits) resulting from the encoding of 47 6-bit (282 bits) information symbols. This is done by appending 16 6-bit parity symbols.
color code	A code that is assigned to the members of a set, under some definition of adjacency, in such a way that each member of the set is assigned a value for the color code that is different from those assigned to all adjacent members of the set.
Comite Consultatif International Telegraphique et Telephonique (CCITT)	Consultative Committee for International Telegraph and Telephone. A standards organization that devises and proposes recommendations for international communications. Refer also to American National Standards Institute (ANSI).
compression	The removal of redundant or unnecessary information from a set of data.
confidentiality	A security process that ensures that the content of a transmitted message cannot be determined except by the possessor of a key associated with the message, even if the transmitted bits are observed.
connectionless network protocol (CLNP)	The standard OSI connectionless network protocol.
connectionless network service (CLNS)	An International Standards Organization (ISO) internetwork service.
control channel	Within the cellular telephone system, several of the channels are assigned as `control' channels. Instead of supporting voice communications, these channels allow the base station to broadcast information to the cellular phones in its area. Cellular phones continuously monitor this broadcast information, selecting the base station that provides the best signal.
control flag	A 6-bit flag transmitted in the forward channel data stream, comprised of a 5-bit busy/idle flag and one bit of the 5-bit decode status flag.
correctable error	An error in a transmitted block that can be corrected by application of the Reed-Solomon decoding process.
COTS	Connection-Oriented Transport Service.
CRC	Cyclic Redundancy Check. These are used for the purposes of error detection.
credentials	Refer to Authentication Credentials.
CSI	Channel Stream Identifier.
CSMA/CD	Carrier Sense Multiple Access with Carrier Detection.
cyclic redundancy check (CRC)	A computational means to detect errors in frames transmitted between devices. The mathematical function is computed at the originating device before a frame is transmitted. Its numerical value is computed based on the content of the frame. This value is compared with a recomputed value of the function at the destination device. Refer also to Frame Check Sequence (FCS).
- D -
data compression	Reducing the size of a file of data by eliminating unnecessary information, such as blanks and redundant data.
data encryption	The processing of data under a secret key so that the original data can only be determined by a recipient in possession of the secret key.
Data Link Layer	Layer 2 in the Open Systems Interconnect (OSI) 7-Layer Network Layer Reference Model. Provides communication among two or more systems. The Data Link Layer performs error checking, addressing, and other functions that are required to ensure accurate data transmission between adjacent systems.
database	A collection of data structured and organized in a disciplined to provide quick access to information of interest.
datagram	A finite-length packet with sufficient information to be independently routed from source to destination.
dB	Decibels.
de-encapsulation	The process of extracting a data packet from the user data field of the encapsulating data packet.
decibel	A unit of measurement for relative signal strength. The value is expressed as 10 times the logarithm of the value taken base 10.
Decode Status Flag	A 5-bit flag used by the CDPD Mobile Data Base Station (MDBS) in the forward channel transmission to indicate the decoding status of Reed-Solomon blocks received on the reverse channel from the CDPD Mobile End System (M-ES).
decompression	The restoration of redundant data that was removed through compression.
decryption	The processing of received data by the possessor of a secret key in such a way that the intended contents of the data are restored.
decryption key	The secret key required to decrypt received data.
dedicated channel	A Radio Frequency (RF) channel that is allocated solely for the use of Cellular Digital Packet Data (CDPD).
default route	A routing table entry which is used to direct any data addressed to any network numbers not explicitly listed in the routing table.
demultiplexing	The process of distributing data received in a shared data stream to the several entities that share the data stream. Demultiplexing can occur at several layers of a protocol stack. Refer to Multiplexing.
deregistration	In the CDPD network, the process of dissociating an Network Entity Identifier (NEI) from the CDPD network.
DES	Data Encryption Standard. An encryption/decryption algorithm defined in FIPS Publication 46.
destination address	An address attached to the information of a message that imparts the intended destination of the message.
Diffie-Hellman EKE	A procedure to exchange electronic keys between communicating devices. Used in CDPD.
digital cellular technology	Refers to the cellular telephony standards that involve digitizing a voice signal, then transmitting the data serially.
Digital Sense Multiple Access With Collision Detection (DSMA/CD)	A technique used by Cellular Digital Packet Data (CDPD) to arbitrate access to the reverse channel stream by more than one Mobile End System (M-ES).
Directory Service	A Directory Service is like a white pages service in which the user supplies the name of an entity, and receives information about that entity such as address, title and description. The user can also search on a particular characteristic and receive one or more directory entries (entity names) that match that search. A directory user can request the address of another entity in order to establish communication. Addresses for real-time communication are Presentation, Session, Transport or Network Addresses for Application Entities in a Mobile End System or Fixed End System. Addresses for message exchange are Distinguished Names which are presented to a Message Handling Service along with a message body.
Directory System Agent (DSA)	Directory Information is distributed over Directory System Agents. Each DSA holds a fragment of the Directory Information Base (DIB). The DSA fills the requests that it can (e.g., from Directory User Agents), and refers requests that it cannot fill to other DSAs using the Directory System Protocol.
Directory System Protocol (DSP)	The protocol used between the various Directory System Agents that make up a global Directory Service.
Directory User Agent (DUA)	A process, sometimes incorporating a user interface, that is used to gain access to a Directory Service. The DUA uses the Directory Access Protocol over an OSI stack to access the Directory Service. Typically, some application process acting as a DUA would access Directory Services to obtain network addresses for entities with which it wants to communicate.
distribution frequency	The number of times in which a message of a particular type is transmitted per unit time, particularly for messages related to radio resource management.
DNS	Domain Name System.
Domain Naming System (DNS)	A mechanism used in the Internet for translating names of host computers into addresses. It is a network database system that provides translation between host names and addresses.
dotting sequence	An alternating series of 38 bits used for the purposes of symbol (bit) timing recovery at the CDPD Mobile Data Base Station (MDBS) for reverse channel transmissions by the CDPD Mobile End System (M-ES).
DS0	Data Switching class 0-a 56 Kbps data channel.
DSA	Directory System Agent. Directory Information is distributed over Directory System Agents. Each DSA holds a fragment of the Directory Information Base (DIB). The DSA fills the requests that it can (e.g., from Directory User Agents), and refers requests that it cannot fill to other DSAs using the Directory System Protocol.
DSMA/CD	Digital Sense Multiple Access with Collision Detection.
DSP	Directory System Protocol.
DTE	Data Terminal Equipment.
DUA	Directory User Agent.
duty cycle	In Cellular Digital Packet Data (CDPD), the amount of time that a Mobile Data Base Station (MDBS) or Mobile End System (M-ES) can access the channel. For an MDBS, the duty cycle is continuous. For an M-ES, it is intermittent and is controlled through the DSMA/CD protocol.
- E -
E-Interface	The network interface between the Cellular Digital Packet Data (CDPD) networks and other external networks.
EID	Equipment Identifier.
EIRP	Equivalent Isotropic Radiated Power.
EKE	Electronic key exchange.
Easter Egg	Would we really hide our names in the specifications? Well ... the devices need to be tested for conformance ... especially that Reed-Solomon coding ...
electronic key exchange	A security procedure by which two entities establish secret keys used to encrypt and decrypt data exchanged between them. The procedure used in CDPD is based on a form of public key cryptography developed by Diffie and Hellman.
encapsulation	(1) The addition of control information to a body of data, either preceding the data, following the data, or both. CDPD uses encapsulation of end-users' packets in ConnectionLess Network Protocol (CLNP) Protocol Data Units (PDUs) for redirection between home and serving MD-ISs (Mobile Data Intermediate Systems).
encryption	The processing of data under a secret key in such a way that the original data can only be determined by a recipient in possession of the secret key. The process reduces the possibility of eavesdropping.
encryption key	The secret key used to perform the encryption process.
end system (ES)	Any computer not considered to be performing routing or bridging functions. In Internet terminology, an ES is a host; ESs are the actual physical and logical end nodes that exchange information.
end-to-end communications	Data delivered between a source and destination endpoint.
end-to-end connection	Connections between the source system and the destination system.
end-to-end data confidentiality	The provision of data confidentiality between the sender and receiver of a communication.
enhanced specialized mobile radio (ESMR)	A recent enhancement to Specialized Mobile Radio (SMR). ESMR is a national network of dispatch radio systems featuring both voice and data communications. It is a circuit-switched network that replaces SMR systems with all new digital cellular technology. Based on Motorola Integrated Radio System (MIRS) technology, ESMR consolidates many smaller SMR systems into a larger network. Voice quality is inferior to current cellular networks, and data is limited to 4800 bps circuit-switched connections with gateways into the Public Switched Telephone Network (PSTN).
enhanced throughput cellular (ETC)	AT&T technology in which cellular-specific modems manage the challenges of cellular connections.
entity	An abstract representation of a device or process implementing a defined set of functions, particularly functions related to the execution of a protocol.
equalization	The process of reducing signal distortion over transmission paths by putting in compensating devices. The telephone network is equalized by the spacing and operation of amplifiers along the way.
equipment identifier (EID)	A unique electronic serial number for the CDPD subscriber device.
ERP	Effective Radiated Power.
error correction	Refer to V.42 error correction.
error rate	In data transmission, the ratio of the number of incorrect elements received to the total number of elements received.
ES	End System.
ESB	End System Bye packet. Part of CDPD Mobile End System (M-ES) registration procedures.
ESH	End System Hello packet. Part of CDPD Mobile End System (M-ES) registration sequence.
ESMR	Enhanced Specialized Mobile Radio.
ESN	Electronic Serial Number. A unique number assigned to a cellular telephone or cellular modem by the manufacturer. This number is required by the cellular carrier when applying for cellular service.
ESQ	End System Query packet. Part of CDPD Mobile End System (M-ES) registration procedures.
Ethernet	A network standard for the hardware and data link levels. .
external F-ES	A Fixed End System (F-ES) connected to the CDPD network outside the administrative domain of the service provider.
external interface	The Cellular Digital Packet Data (CDPD)-based wireless packet data service provider's interface to existing external networks. The external application service providers communicate with CDPD subscribers through this external interface.
- F -
F-ES	Fixed End System.
fade	A temporary reduction in received signal strength.
FCC	Federal Communications Commission.
FCS	Frame Check Sequence.
FEC	Forward Error Correction.
Fascicle	A collection of documents (or a bundle of hay.) Used in CCITT standards. We needed a new name for the collections of CDPD specification Parts. The discussion went: "What shall we call these collections?" ... "I've always wanted to write a Fascicle! Let's call them Fascicles!" ... "Done!"
file transfer protocol (FTP)	Common Internet file transfer program that uses Transmission Control Protocol/Internet Protocol (TCP/IP)
firewall	A security router that filters traffic based on addresses.
Fixed End System (F-ES)	A non-mobile end system. A host system that supports or provides access to data and applications.
flow control	A procedure that allows an entity to cause a remote entity to suspend or resume the transmission of data.
FM capture	In extreme cases of co-channel interference, a receiver may experience what is referred to as "FM capture," which is a co-channel interference condition where the good signal is treated as noise and the interferer is selected. Cellular users often experience FM capture as a momentary burst of someone else's conversation.
fonts	Subject of much debate at specification meetings. Why did we end up with New Century Schoolbook anyway?!!
forced hop	A channel hop made by the Mobile Data Base Station (MDBS) because non-Cellular Digital Packet Data (CDPD) activity is detected on the channel that is currently in use.
forward channel	The transmission channel for data from the MDBS to the M-ES.
forward error correction	The addition of parity information to transmitted data that allows a receiver to correct errors that may occur during the course of transmission.
frame	A Link Protocol Data Unit.
frame check sequence (FCS)	The standard 16-bit cyclic redundancy check used for High-level Data Link Control (HDLC) and frame relay frames. The Frame Check Sequence (FCS) detects bit errors occurring in the bits of the frame between the opening flag and the FCS, and is only effective in detecting errors in frames no larger than 4096 octets. Refer to Cyclic Redundancy Check (CRC).
frame flag sequence	The unique bit pattern "01111110" used as the opening and closing delimiter for the link layer frames.
frame header	Address information required for transmission of a packet across a communications link.
frame relay	A packet-oriented Wide Area Network (WAN) connection that offers high performance. Often called a fast-packet switching network because tasks such as error checking, packet sequencing, and packet acknowledgment are handled by the end systems involved in the transmission rather than by the network itself.
frame relay access device	Required for connection into a frame relay network.
frequency modulation	A modulation technique in which the carrier frequency is shifted by an amount proportional to the value of the modulating signal. The amplitude of the carrier signals remains constant. The deviation of the carrier frequency determines the signal content of the message.
frequency-shift keying	A modulation scheme that uses different frequencies to denote a one or a zero.
FTP	File Transfer Protocol.
full-duplex	Capability of simultaneously transmitting and receiving.
- G -
gateway	A protocol conversion facility allowing connection of dissimilar communication systems.
Gaussian minimum shift keying (GMSK)	A member of the class of constant-envelope continuous-phase modulations with a Gaussian filtered phase response. Used in the airlink physical layer in Cellular Digital Packet Data (CDPD) and GSM.
GHz	GigaHertz, Hz x 109 (One million cycles per second).
Global Positioning System (GPS)	A system of satellites orbiting the earth used for navigation and location. Position on earth is determined by referencing multiple satellites in the system whose orbits are precisely known and thus provide a reference frame for measuring distances.
Global Standard For Mobile Communications (GSM)	A digital cellular standard used primarily in Europe and some other countries. Primarily a Time Division Multiple Access (TDMA) cellular voice service, though data services are offered over GSM. Formerly called Groupe Speciale Mobile.
GMSK	Gaussian Minimum Shift Keying.
GSM	Global Standard for Mobile communication.
- H -
half-duplex	Capability of transmitting or receiving, but not both simultaneously.
half-duplex M-ES	A Mobile End System (M-ES) that can either transmit or receive, but cannot do both simultaneously, for example, an M-ES that has a single transceiver (radio).
handoff	The process of passing a Radio Frequency (RF) connection to another available channel either at the originating cell site, a neighboring cell site, or in another service provider's coverage area. As the subscriber moves from one location to another, the connection is continually handed off from channel to channel and from cell site to cell site.
Hayes AT command interface	Traditional method to control a modem and begin and end data transmissions.
Hayes-compatible AT command set	Used to control a modem and to initiate a connection to the network.
HDLC	High-level Data Link Control.
header	The initial portion of a Protocol Data Unit (PDU) containing control information. Also referred to as the Protocol Control Information (PCI)
high-level data link control (HDLC)	A link-level communications protocol developed by the International Standards Organization (ISO). HDLC manages synchronous, code-transparent, serial information transfer over a link connection.
Home MD-IS	The CDPD network component that performs the Mobile Home Function.
hop	A change of Radio Frequency (RF) channel used to carry the Cellular Digital Packet Data (CDPD) data for a channel stream.
hop channel	A Radio Frequency (RF) channel that has been declared a candidate for carrying a Cellular Digital Packet Data (CDPD) channel stream after a channel hop.
host	The computer providing file transfer and communications services to client computers.
hybrid CDPD	Circuit-switched CDPD (Cellular Digital Packet Data), a technology known as hybrid CDPD, is the system architecture developed by the CDPD Forum for interconnecting circuit-switched data, including cellular and land-line links, with the CDPD network.
hysteresis	Mechanism to reduce unnecessary continual cell change.
- I - J -
I-interface	The network interfaces between CDPD service provider networks.
ICMP	Internet Control Message Protocol.
idle state	A channel stream is in an idle state if the Mobile Data Base Station (MDBS) signals in the busy/idle flag that no Mobile End System (M-ES) is currently transmitting on the channel.
IEEE	Institute for Electrical and Electronics Engineers.
IETF	Internet Engineering Task Force. The IETF is a large open community of network designers, operators, vendors, and researchers whose purpose is to coordinate the operation, management, and evolution of the Internet, and to resolve short- and mid-range protocol and architectural issues. It is a major source of proposed protocol standards which are submitted to the Internet Activities Board for final approval.
in-band control	Control information that is provided in the same channel as data.
Integrated Services Digital Network (ISDN)	A network interface that integrates voice, data, and video signals into a single digital telephone line. The worldwide telephony standard for digital telecommunications.
Inter-Area Cell Transfer	A cell transfer between two cells that are controlled by different serving Mobile Data Intermediate Systems (MD-ISs).
Inter-Service Provider Interface	Cellular Digital Packet Data (CDPD)-based wireless packet data service provider's interface to cooperating CDPD-based wireless packet data service provider networks.
intermediate system (IS)	A node that is connected to more than one subnetwork with a primary role of forwarding data from one subnetwork to another. In Internet terminology, ISs are known as routers that relay data packets from ESs to their intended destinations.
internal F-ES	A Fixed End System within the administrative domain of theCDPD service provider. Typically provides value-added support services such as network management, accounting, directory, and authentication services.
International Standards Organization (ISO)	Organization that determines standards for international and national data communications. The US representative to the ISO is the American National Standards Institute (ANSI).
Internet	A set of networks using a set of network-independent protocols for communication that have been defined under the aegis of the Defense Advanced Research Projects Agency.
Internet (Internetwork)	(1) The global collection of interconnected local, mid-level, and wide-area networks that use Internet Protocol (IP) as the network layer protocol. (2) Any connection of two or more local or wide-area networks.
Internet address	An assigned number that identifies a host in an Internet. It has two or three parts: network number, optional subnet number, and host number.
Internet Protocol (IP)	A connectionless protocol that requires no prior call setup between the source and destination systems.
Intra-Area Cell Transfer	A cell transfer between two cells that are controlled by the same serving Mobile Data Intermediate System (MD-IS).
IP	Internet Protocol.
IP address	Internet Protocol address.
IS	Intermediate System.
IS-95	The CDMA (Code Division Multiple Access) standard.
ISC	Mobile Data Intermediate System Confirm packet. Part of Mobile End System (M-ES) registration procedures.
ISO	International Standards Organization.
- K -
Kbps	Kilobits per second.
key	A quantity required for the execution of security algorithms that is intended to be used only by legitimate entities.
key exchange	A procedure by which the value of a key is shared between two or more parties.
key generation	The process of creating a key.
key management	The rules and procedures governing the creation, distribution, and replacement of keys.
key sequence number	An identifier associated with a key that allows one value of a key to be distinguished from an older or newer value of the key.
kHz	kiloHertz, Hz x 103.
km	kilometer.
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LAN	Local Area Network. A network that takes advantage of the proximity of computers to offer relatively efficient, higher speed communications than long-haul or wide-area networks. Electronic mail, messaging, file sharing and database access are common LAN applications.
landline	Fixed connection that uses wires, not radio transmission.
LAPD	Link Access Protocol for the D Channel. It is a Link Layer protocol defined in Consultative Committee for International Telegraph and Telephone (CCITT) specifications Q.920 and Q.921 and forming the basis of the Cellular Digital Packet Data (CDPD) Link Layer's Mobile Data Link Protocol (MDLP).
latency	The slight delay in data delivery through a network.
Layer Entity	An entity performing the functions required for a layer of protocol.
Layer Management Entity Identifier	An identifier used to select an entity concerned with a particular set of layer management functions.
Layer Service	A term that applies to the layers of the OSI Reference Model. A Layer Service represents a set of functions offered to a network user by a Layer Service Provider. A Layer Service consists of one or more primitives which are invoked by either the user or the provider.
Layer Service Provider	Each layer of the OSI Reference Model is a Layer Service Provider. Examples of layers are Presentation, Session, Transport, Network, and Link. The Layer Service is made available through Service Access Points.
LD	Location Directory.
legacy system	Refers to older equipment and systems that are doing an important job for a company, but which would not be implemented on the same platform if deployed today. Legacy systems were often developed by people other than those who are responsible for them now.
Link Access Procedure for Modems (LAPM)	LAPM is the V.42 standard determined by a consultative committee of the International Telecommunications Union-Telecommunications Systems (ITU-TS) and specifies the use of LAPM as an error-control protocol. LAPM provides somewhat better performance than Microcom Networking Protocol (MNP) 4, including improved setup and better performance over poor lines.
Link Access Protocol on the D-channel (LAPD)	A protocol that operates at the data link layer (layer 2) of the OSI architecture. LAPD is used to convey information between layer 3 entities across the frame relay network. The D-channel carries signaling information for circuit switching.
Link Layer	That layer of a distributed communications system concerned with the operation of a data link between two or more entities. Provides services such as data encryption, data compression, and flow control.
Link Protocol Data Unit (LPDU)	The Protocol Data Unit (PDU) exchanged between Link Layer entities. Also known as a frame.
LMEI	Layer Management Entity Identifier.
Location Directory (LD)	The repository of information specifying the current Forwarding Address of a collection of mobile hosts to be accessed by the redirectors. For Cellular Digital Packet Data (CDPD), refer to Mobile Network Location Protocol And Home Mobile Data Intermediate System.
LPDU	Refer to Link Protocol Data Unit.
LSDU	Link Layer Service Data Unit.
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M-ES	Mobile End System. An M-ES is a wireless communications device that conforms to Cellular Digital Packet Data (CDPD) standards. The end system that provides remote access to theCDPD network via the airlink. In the majority of cases, the M-ES is a laptop equipped with a Radio Frequency (RF) modem. In the CDPD network, the M-ES is a unique network node and has a unique network address.
MAC	Medium Access Control.
MAC Layer	That layer of a distributed communications system concerned with the control of access to a medium that is shared between two or more entities.
MAC protocol	The procedures used to control access to a medium that is shared between two or more entities.
management	Protocols and procedures concerned with configuration, administration, and similar functions.
management entity	An entity concerned with supporting management.
management information base (MIB)	The database used by network management systems and contains technical information about each device on the network.
market	A geographical area of demand and responsibility for cellular service.
MAS	Mobile Application Subsystem. An MAS is application software that is independent of the Cellular Digital Packet Data (CDPD) Network.
maximum power level	Maximum power output limit for Mobile End System (M-ES).
MCHO	Mobile Controlled Hand-off.
MD-IS	Mobile Data Intermediate System.
MD-IS serving area	The set of cells controlled by a single serving Mobile Data Intermediate System (MD-IS).
MDBS	Mobile Data Base Station.
MDLP	Mobile Data Link Protocol. The Link Layer protocol defined in CDPD networks.
medium access control (MAC)	The function of controlling access to a medium that is shared between two or more entities.
Medium Access Control (MAC) Layer	Refer to Medium Access Control.
message	A meaningful unit of information. A Protocol Data Unit (PDU) of defined format and purpose. Refers to the basic unit of data being transmitted.
Message Handling System (MHS)	A supplementary service that implements Message Store and Forward Message Handling. MHS is used within the Cellular Digital Packet Data (CDPD) network. MHS provides for distribution lists, return receipts and allows for gateways to proprietary message systems, including alternative delivery mechanisms such as telex or fax.
Message Store (MS)	Acts as a mailbox for storing messages coming from a Message Transfer Agent and destined for a User Agent.
message transfer agent (MTA)	Performs Message Routing (e.g., to other MTAs) and message delivery to User Agents and Message Stores.
messaging API (MAPI)	An application protocol.
MHF	Mobile Home Function.
MHS	Message Handling System.
MHz	MegaHertz (Hz x 106).
MIB	Management Information Database.
microslot	The time between two consecutive busy/idle flags (60 bits, or 3.125 milliseconds at 19.2 kbps). It is used in CDPD only.
middleware	Software that isolates applications from the protocol requirements, hardware, and actual operations of a particular network. May perform protocol conversions between disparate systems. Refers to any software that resides between a client program and a server program. Middleware includes protocol stacks, network operating systems, and messaging systems.
MME	Mobility Management Entity.
MNLP	Mobile Network Location Protocol.
MNP-10	Microcom Networking Protocol Ten. MNP-10 provides a proprietary error-correcting and data compression protocol for dial-up modems from 2.4 to 14.4 Kbps. MNP-10 consists of Adverse Channel Enhancements that optimize performance in environments with poor or varying line quality, such as cellular telephones, international telephone calls, and rural telephone service.
MNRP	Mobile Network Registration Protocol.
Mobile Application Subsystem (MAS)	That portion of a Mobile End System (M-ES) concerned with the provision of application services. The MAS contains the application software that is independent of the CDPD network. In most cases, this includes network software.
Mobile Data Base Station (MDBS)	Component of the CDPD network that provides data link relay functions for a set of radio channels serving a cell. An MDBS is located in each cell site, and its primary role is to relay data between Mobile End System (M-ES) and the Mobile Data Intermediate System (MD-IS). It is the stationary network component responsible for managing interactions across the airlink interface.
Mobile Data Intermediate System (MD-IS)	The CDPD network element that performs routing functions based on knowledge of the current location of the M-ES. Responsible for CDPD mobility management. It operates a Cellular Digital Packet Data (CDPD)-specific Mobile Network Location Protocol (MNLP) to exchange location information.
Mobile Data Link Protocol (MDLP)	The Link Layer protocol used in Cellular Digital Packet Data (CDPD). Provides Temporary Equipment Identifier (TEI) management, multiple frame operation, unitdata transfers, exception condition detection with selective reject recovery, etc.
Mobile End System (M-ES)	An end system that accesses the CDPD network through the airlink interface. The device that allows mobile users to work in an untethered fashion while remaining connected to a data network. The system's physical position may change during data transmission.
mobile home function	A Mobile Data Intermediate System (MD-IS) mobility function that (1) maintains an information database of the current serving area of each of its homed Mobile End Systems (M-ESs), and (2) operates a packet forwarding service for its homed M-ESs.
Mobile Identification Number	When the "SEND" key is pressed, a cellular phone transmits an origination message to the base station. This message includes the dialed digits and the identity of the calling cellular phone. The calling cellular phone is identified by its Mobile Identification Number (MIN), which is usually the same as its ten-digit phone number.
Mobile Network Location Protocol (MNLP)	In the CDPD network, protocol used between the Home Mobile Data Intermediate System (MD-IS) and the Serving MD-IS to keep the Home MD-IS updated on the location of a Mobile End System (M-ES).
Mobile Network Registration Protocol (MNRP)	In the CDPD network, protocol used between the Mobile End System (M-ES) and the Serving Mobile Data Intermediate System (MD-IS) to announce the M-ES's Network Entity Identifier (NEI) and to confirm the service provider's willingness to provide service.
Mobile Serving Function (MSF)	A Mobile Data Intermediate System (MD-IS) function that (1) maintains an information database of the Mobile End Systems (M-ES) currently registered in the serving area, and (2) de-encapsulates forwarded packets from the MHF and routes them to the correct channel stream in a cell where the destined M-ES is located. Refer to Serving Mobile Data Intermediate System.
mobile switching center (MSC)	The location of the Digital Access and Cross-connect System (DACS) in a cellular telephone network.
mobile-controlled handoff	The decision to initiate a transfer or handoff from one cell to another cell is under the control of the mobile device. Used in CDPD.
mobility management	A service provided by the Network Layer. Mobility is primarily a routing issue in that Network Protocol Data Units (NPDUs) that are destined for a Mobile End System (M-ES) must be routed toward that Mobile End System. In the CDPD network, the home Mobile Data Intermediate System (MD-IS) forwards NPDUs to the serving Mobile Data Intermediate System for a Mobile End System.
Mobitex Asynchronous Communications Protocol (MASC)	The layer that communicates with the Mobitex radio modem. Used in the RAM mobile data network.
Mobitex Packet (MPAK)	The RAM Mobile Data Network Layer protocol.
Mobitex Transport Protocol (MTP1)	The RAM Mobile Data Transport Layer protocol.
modem	MOdulator-DEModulator. A device that translates computer information for transmission on both cellular and regular telephone lines.
modem pool	A device that provides the equivalent of multiple data modems. Typically deployed by cellular carriers to provide circuit switched data services.
modulation	The analog waveform of a transmitted digital signal.
Motorola Integrated Radio System (MIRS)	Technology developed by Motorola. ESMR is based on this technology. Nextel is the largest company deploying ESMR. (Now called iDEN).
MS	Message Store or More Segments.
MSC	Mobile Switching Center.
MSF	Mobile Serving Function.
MTA	Message Transfer Agent.
MTS	Message Transfer System.
multicast	A one-way point to multi-point routing and relaying service that allows a message to be addressed and delivered to all members of a group, regardless of their current location.
multipath fading	The singal degradation that occurs when multiple copies of the same radio signal arrives at the receiver through different reflected paths. The interference of these signals, each having traveled a different distance, result in phase and amplitude variations. The radio signal processing in both the base station and mobile units have to be designed to tolerate a certain level of multipath fading.
multiplexing	The process of mixing data originating from several entities into a single shared data stream. Multiplexing can occur at several layers of a protocol stack.
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N=7 frequency plan	The feature of the cellular system that distinguishes it from earlier technology is the allocation of channels within geographic areas called cells. By using only a fraction of the total allocation of channels in each cell, and coordinating the frequency assignments in neighboring cells, the set of available channels can be reused in non-adjacent cells. The complete set of available channels is divided into seven groups. This frequency plan is known as the "N=7" frequency plan.
NAM	Number Assignment Module. Cellular phones are configured with NAM parameters, which include the Mobile Identification Number (MIN) and various other data about radio channels. To use any cellular phone over a cellular network the NAM must be configured correctly. The MIN is usually the same as the phone number and is assigned by the cellular carrier. The other parameters in the MIN ensure that the cellular phone will be able to access the cellular system correctly, and are usually provided by the carrier or dealer. To verify the user's identity, the cellular phone also transmits an Electronic Serial Number (ESN) when it communicates with the MTSO. This ESN is permanently assigned to the phone, and is entered by the carrier in the MTSO database when a user signs up for service.
Narrowband Personal Communications Standards (PCS)	Refers to a new spectrum available for paging services, including two-way paging. Unlicensed Personal Communications Services (PCS) refers to spectrum from 1910 MHz to 1930 MHz available for cellular PBXs and cellular LANs. Broadband (or wideband) PCS is the service of most interest to wide area cellular data users. Broadband PCS consists of 120 MHz of new spectrum available for cellular networks.
NDIS	Network Driver Interface Specification.
NEI	Network Entity Identifier.
network	A collection of computers or other similar devices linked for communication.
Network Driver Interface Specification (NDIS)	Application programming interface standard for attaching to data communications devices.
Network Entity Identifier (NEI)	An Internet protocol address, or ConnectionLess Networking Protocol (CLNP) address, or any other protocol addressing utilized by the provider in transmission and receipt of Cellular Digital Packet Data (CDPD) services. The address that identifies that a user is authorized to use the service.
Network Information Center (NIC)	Any organization that is responsible for providing network users with information about services provided by any network.
Network Layer	Layer 3 in the Open Systems Interconnect (OSI) 7-Layer Network Layer Reference Model. Internet Protocol (IP) and ConnectionLess Network Protocol (CLNP) reside at this layer. Provides packet routing and relaying between end systems on the same network or on interconnected networks and is independent of the transport protocol used.
Network Layer Protocol Identifier (NLPI)	An identifier allowing entities providing different Network Layer protocols to be distinguished from each other.
network management	The process of managing the various functions of the network.