Appendix A: Glossary

---

1G:

First generation wireless networks. Analog cellular mobile communication systems are referred as 1G systems.

2G:

Second generation wireless networks. The digital wireless mobile communication systems that can support data services up to 28.8kbps data rates are known as 2G systems.

2.5G:

Two and a half generation wireless networks. The digital wireless mobile communication systems that can support data services up to 144kbps data rates are known as 2.5G systems. 3G: 3G: Third generation wireless networks. The digital wireless mobile communication systems that can support data services up to 2.048 Mbps data rates are known as 3G systems.

3GPP:

3G Partnership Program. The committee set up to arrive at common standards for third generation wireless networks.

4G:

Fourth generation wireless networks. The 4G networks being planned can support very high data rates. 4G systems are still in the concept stage.

AAL:

ATM adaptation layer. This layer runs above the ATM layer to support multimedia services over ATM networks. The main function of this layer is segmentation and reassembly.

ACK:

Abbreviation for acknowledgement. ACK is sent by the receiver to inform the sender that the packet was received successfully.

ACL:

A asynchronous communication link. In Bluetooth, data services are supported on an ACL link which provides connectionless service.

ACM:

Association for Computing Machinery. An international professional body for computer engineers.

ADPCM:

Adaptive differential pulse code modulation. A technique used to code voice at 32kbps data rate. The quality will be same as that of 64kbps PCM. Used in DECT.

AMs:

Amplitude modulation. Analog modulation technique in which the carrier amplitude is varied in proportion to the amplitude of the modulating signal.

AMPS:

Advanced mobile phone system. First generation analog cellular system that was in use in North America.

API:

Application programming interface. A set of software routines provided by software tool vendors to develop applications. For example, Java Media Framework (JMF) APIs provided by Sun Microsystems are used to develop multimedia applications over IP networks.

ARP:

Address resolution protocol. ARP is used to map IP address to the physical address such as an Ethernet address.

ARPA:

Advanced Research Projects Agency. This agency of the U.S. Department of Defense, funded the ARPANet project, which evolved into the Internet.

ARPANet:

The experimental network setup in the early 1970s to interconnect a few sites using packet switching and TCP/IP protocols. This network expanded rapidly to many other sites. ARPANet evolved into the present Internet.

ARQ:

Automatic Repeat Request. When the transmission link is not reliable, ARQ protocol is used for retransmission of data. The sender sends a packet and, if the acknowledgement is not received within a specified time, the packet is retransmitted. A number of protocols such as stop-and-wait protocol and sliding window protocol belong to the ARQ family of protocols.

ASK:

Amplitude shift keying. A digital modulation technique in which binary 1 is represented by presence of carrier and binary 0 by absence of carrier. Also called on-off keying.

ASR:

Automatic speech recognition. The input speech is compared with already stored templates to make the computer recognize spoken words.

ATM:

Asynchronous Transfer Mode. A fast packet-switching network technology that supports broadband services. The packets, called cells each of 53 bytes, are used to carry the data.

Audio:

Sounds that can be heard. Voice and music are examples of audio signals. In audio broadcasting, the bandwidth of audio signals is limited to 15kHz.

Authentication:

Authentication is a process to verify the identity of parties who exchange information.

Autonomous system:

An internet, or network of networks, within the administrative control of an organization. An autonomous system can use its own protocols for routing its packets.

Bandwidth:

A measure of the highest frequency component present in a signal. For example, voice signal has a bandwidth of 4kHz. The capacity of a communication channel is also referred to as bandwidth. The capacity can be measured either in Hz or in bits per second. Example: The radio channel has a bandwidth of 25kHz. The optical fiber has a bandwidth of 1Gbps.

BER:

Bit Error Rate. A measure of the performance of a communication system. The number of bits received in error divided by the total number of bits.

BGP:

Border gateway protocol. On the Internet, BGP is used by routers to exchange routing information. When the routers belong to different autonomous systems, this protocol is used.

Bluetooth:

Standard for wireless personal area networks. Devices such as a desktop, palmtop, or laptop computer, mobile phone, fax machine, printer, headset and microphone can be Bluetooth enabled by attaching a small Bluetooth module.

BPF:

Band pass filter. A filter that passes only a band of frequencies. BPF will have a lower cutoff frequency and an upper cutoff frequency.

BREW:

Binary runtime environment for wireless. A tool to develop wireless applications on CDMA-based wireless networks. Developed by Qualcomm Corporation.

Bridge:

A bridge interconnects two LANs. If the two LANs use different protocols, the bridge does the necessary protocol conversion.

Broadcast:

To deliver information to a large number of receivers. Audio and video broadcasting facilitate distribution of audio/video programs to a large number of receivers. In a data network, it means to send the data to all the nodes on the network. A broadcast address is used for this operation.

BSC:

Base station controller. In a mobile communication system, a number of base transceiver systems (BTSs) are controlled by a BSC. The BSC assigns the radio channels and time slots to the mobile devices.

BTS:

Base transceiver subsystem. In a mobile communication system, each cell is controlled by a BTS. BTS consists of radio transmitters and receivers.

Carrier frequency:

The frequency of the carrier used to modulate a signal.

CCITT:

Comite Consultif International de Telegraphique et Telephnique, the French name of the International Consultative Committee for Telegraphy and Telephony. This organization is now called ITU-T (International Telecommunications Union-Telecommunications Sector).

CDMA:

Code division multiple access. A spread spectrum technology that provides secure communication. Frequency hopping and direct sequence are examples of CDMA.

Cell:

In cellular mobile communication systems, service area is divided into small regions called cells. Each cell contains a base station transceiver. In ATM networks, the packet is called a cell, the size of the cell being 53 bytes.

Certificate:

A digitally signed document that contains the name and public key of the other party. Public keys are distributed using certificates.

Channel:

The transmission medium (twisted pair, radio frequency band, optical fiber) is referred to as a channel.

Channel capacity:

The highest data rate that can be supported by a communication medium.

Channel coding:

A coding mechanism used to detect and correct errors.

Checksum:

The additional bits added by the sender for a packet. The one's complement sum of the bytes of the packet is calculated and added to the packet. At the receiver, the checksum is again calculated and compared with the received checksum. If the two match, the receiver is assured that the packet is received without errors.

Chipping rate:

A pseudo-random sequence of bits XORed with the data bits to implement direct sequence code division multiple access.

CIDR:

Classless inter-domain routing. A mechanism of routing in which a group of networks with contiguous class C IP addresses are considered as a single network.

Circuit switching:

Switching mechanism used in telephone networks. Circuit switching involves setting up a circuit, data transfer, and disconnection of the circuit.

CLNP:

Connectionless network protocol. Equivalent ISO protocol of IP.

Clock recovery:

The process of deriving the clock from the received serial data.

Congestion:

A state of the packet switch or router caused by buffer or memory limitation. When the switch cannot process the incoming packets, it may discard the packets. Congestion control mechanisms are used to reduce the congestion. The switch/router may discard the packet, but it informs the other switches/hosts to reduce the packet transmission rate.

CRC:

Cyclic redundancy check. A code appended to the packet at the transmitting side so that the receiver can detect if there is any error in the packet. CRC-16, CCITT-16, and CRC-32 are the standards for CRC calculation.

CSMA/CD:

Carrier sense multiple access/collision detection. Protocol used for medium access in Ethernet LAN. A node on the LAN checks whether the medium is free. If the medium is free, the packet is immediately transmitted. If it is busy, the node will wait until it becomes free and then transmit the packet. If two nodes transmit their packets simultaneously, it results in collision. When there is collision, the node will back off and retransmit the packet.

Data compression:

A technique used to reduce the data rate/storage requirement. Data compression techniques are classified as lossless compression techniques and lossy compression techniques.

Datagram:

A chunk of data. The packet in the Internet Protocol (IP) layer is referred as an IP datagram in IP Version 4. The packet of user datagram protocol (UDP) is also referred to as a datagram.

Data rate:

The rate at which data is transmitted. Measured in bits per second (bps), kilobits per second (Kbps), megabits per second (Mbps), gigabits per second (Gpbs), or terabits per second (Tbps).

Decryption:

The reverse process to encryption. Restoration of the encrypted data.

Delay-bandwidth product:

The product of round-trip delay and bandwidth. Indicates the amount of data in transit on the medium.

Demultiplexing:

Reverse process of multiplexing. The data that is combined during multiplexing is separated by demultiplexing.

DES:

Data Encryption Standard. An algorithm for encryption of data using a 56-bit key. Developed by the U.S. Department of Defense.

DHCP:

Dynamic host configuration protocol. A protocol used to configure the IP address of the nodes in a network.

Digital watermark:

The technique of embedding a secret message in another message (text, voice, image, or video) is called digital watermarking. The secret message is called the watermark, and the message carrying the watermark is called the host message. Digital watermarking is used to embed copyright information, the company logo, or the serial number of the software package in another image.

DS-CDMA:

Direct sequence code division multiple access. A spread spectrum multiple access technique in which ones and zeros in a bit stream are replaced by special codes unique for each transmitter.

DSL:

Digital subscriber line. DSL is used to access the Internet service provider over twisted copper pair at high data rates. A family of DSL standards known as xDSL has been developed, that include HDSL, ADSL, and VDSL.

EGP:

Exterior gateway protocol. A routing protocol used by the IP layer to route packets. EGP was replaced by BGP on the Internet.

Encapsulation:

Packet of one protocol layer embedded in the data field of the packet of the layer below it. For example, the protocol data unit (PDU) of the TCP layer is encapsulated in the IP datagram.

Encryption:

A technique wherein the bit stream is modified using a key. Only the destination that knows the key can decode the bit stream.

Entropy:

Entropy is a measure of the information content produced by an information source.

Error correction:

A mechanism by which the receiver corrects the errors introduced by the channel. Additional bits are added by the sender to facilitate error correction by the receiver.

Error detection:

A mechanism by which the receiver detects the errors introduced by the channel. The errors can be detected using parity, checksum, or CRC.

Ethernet:

The most popular local area network standard. An equivalent LAN standard is IEEE 802.3.

Fax:

Short form for facsimile. Fax facilitates transmission of documents.

FDDI:

Fiber distributed data interface. A local area network standard that uses optical fiber as the transmission medium.

FEC:

Forward error correction. Redundancy is introduced in the data bits at the transmitting side so that the receiver can correct the errors.

Filter:

A module that removes the unwanted frequency components. Low pass filters, band pass filters, and band reject filters are examples.

Firewall:

Software that runs on a server or router that provides the necessary security features to the network.

Flow control:

A mechanism used to control the flow of packets in a network. If a host/router cannot receive the packets as fast as the source is transmitting, the host/router sends a message to reduce flow.

Fragmentation:

Division of a packet into smaller units by a host/router. These smaller units have to be reassembled at the other end to form the original packet.

Frame:

The packet of data at the datalink layer is called a frame.

Frame Relay:

A network technology that provides fast packet switching by reducing the overhead at the datalink layer. Frame Relay networks are used extensively in wide area networks.

Frequency hopping:

One form of spread spectrum multiple access. In frequency hopping, a device uses different radio channels to transmit its packets. For example, in Bluetooth, a device transmits each packet in a different radio channel. Hopping is done in a pseudo-random sequence. Only the intended receiver that knows the sequence can decode the data.

FM:

Frequency modulation. Analog modulation technique in which the frequency deviation of the carrier is proportional to the amplitude of the modulating signal.

FSK:

Frequency shift keying. Digital modulation technique in which binary Ø is represented by one frequency and binary 1 by another frequency. The difference between these two frequencies is the frequency deviation.

ETSI:

European Telecommunications Standards Institute, which formulates the telecommunications standards for Europe. In India, most of the telecommunications standards are based on European standards.

FDMA:

Frequency division multiple access. An access mechanism in which different users share a pool of radio channels. A radio channel is assigned to a user when the user has data to send.

FTP:

File Transfer Protocol. Application layer protocol in TCP/IP networks for file transfer.

GSM:

Global System for Mobile Communications. The standard specified by ETSI for cellular mobile communications. This standard has been adapted by many African and Asian countries and in Europe.

H.323:

The series of protocols for multimedia communication over IP networks.

HDLC:

High level data link control. Datalink layer protocol that is the basis for many other link layer protocols such as LABP, LAPD, and LAPF.

HomeRF:

The wireless technology developed to network various devices at home.

Host:

An end system (or node) connected to a computer network.

HTML:

Hypertext Markup Language. A markup language to develop Web content. The markup specifies how the document is organized (through anchor tags) and how to present the content (through tags for bold, underline and so on).

HTTP:

Hypertext Transfer Protocol. The application layer protocol in TCP/IP networks for World Wide Web service.

ICMP:

Internet Control Message Protocol. A protocol at the same level as IP, that uses IP service. ICMP is used to send error and status messages by routers.

IEEE:

Institute of Electrical and Electronics Engineers. The largest professional body of electrical and electronics engineers.

IEEE 802 Committee:

The committee formed by IEEE to develop standards for local area networks.

IETF:

Internet Engineering Task Force is the body that coordinates and approves the technical specifications of protocols used on the Internet.

Internet:

The global network of computer networks.

IP:

Internet Protocol. The protocol responsible for addressing and routing.

IP address:

Address assigned to each host and router on the Internet. In IP Version 4, the address length is 32 bits, in IP Version 6, the address length is 128 bits.

IPng:

IP next generation. This protocol is now known as IP Version 6.

IPv6:

The new version of IP that will supersede IP Version 4.

IPN:

Interplanetary Internet. Vincent Cerf proposed the project which aims to develop Internets on different planets and spacecraft and to interconnect them.

IPSEC:

The protocol that provides the security at IP level. Used in virtual private networks.

IrDA:

Infrared Data Association. IrDA specifies the standards for low-cost infrared communication systems.

IRTF:

Internet Research Task Force. The group that coordinates the research activities of the Internet.

ISDN:

Integrated Services Digital Network. A network architecture that provides multimedia services through standard interfaces. Narrowband ISDN and broadband ISDN standards have been developed by ITU-T.

ISO:

International Organization for Standardization. An international body that develops standards for many things, from paper sizes to telecommunications.

ITU-T:

International Telecommunications Union Telecommunications Sector. The international body that develops standards for communications. The standards are referred as recommendations.

JMF:

Java Media Framework. The APIs for the Java programming language facilitate development of multimedia applications over IP networks.

JPEG:

Joint Photography Experts Group. The group that standardized the image compression technique. Using JPEG compression technique, a compression ratio of 30:1 can be achieved.

LAN:

Local area network. A network that spans an area of about 10 km radius.

Latency:

Delay.

LDAP:

Lightweight Directory Access Protocol. A protocol for accessing, updating, searching, and retrieving information from a directory. Derived from X.500 standard.

Link:

A communication path interconnecting two end points.

LLC:

Logical link control. A sublayer in the datalink layer of LANs. LLC layer runs above the MAC layer. LLC layer provides a logical link between two end points and takes care of error control and flow control.

Lossless coding:

A compression technique in which the original information is not lost. File compression utilities such as WinZip are lossless coding schemes.

Lossy coding:

A compression technique that causes information loss. The JPEG compression technique is an example of lossy coding.

LPC:

Linear prediction coding. A coding technique used for coding voice signals at low bit rates. This technique is based on the fact that a voice sample can be predicted from the previous samples. Variations of LPC coding are used in wireless communication systems.

LPF:

Low pass filter. A filter that does not allow frequency components above a certain value. An LPF with a cutoff frequency of 4kHz allows only frequency components below 4kHz to pass through it.

MAC:

Media access protocol. The sublayer of the datalink layer in LANs. MAC layer runs above the physical layer and below the LLC sublayer. The medium access by different nodes is governed by this protocol. CSMA/CD is an example of MAC.

MAN:

Metropolitan area network. A network that covers an entire city.

MIB:

Management information base. The information pertaining to a network element (host, router, switch, etc.) is stored in the MIB and can be accessed by a network manager using a network management protocol such as SNMP.

Microbrowser:

A small browser that runs in a wireless device such as a mobile phone.The microbrowser interprets the content obtained from a server. A microbrowser running on a mobile device that supports WAP can interpret the content written in WML.

MIME:

Multipurpose Internet Mail Extension. The protocol that runs above SMTP to support multimedia email.

MP3:

MPEG layer 3. A standard for coding audio signals. Defined as part of the MPEG standard for video coding.

MPEG:

Moving Picture Experts Group. The group that defined the standards for video coding. MPEG2 and MPEG7 are used for digital video transmission.

MSC:

Mobile switching center. The entity that carries out the switching operations in a cellular mobile communication system. MSC has a number of databases that store subscriber information. These databases are home location register (HLR), visitor location register (VLR), equipment identity register (EIR), and authentication center (AuC). MSC is connected to the BSCs.

Multicast address:

Address corresponding to multiple recipients.

Multiplexing:

The process of combining a number of channels for transmission over a communication link.

NSF:

National Science Foundation. The agency of U.S. government that supports advanced research.

OC:

Optical carrier. In SONET hierarchy, the hierarchy levels are represented as OC, such as OC-3, OC-12, and OC-768.

Octet:

The standards documents (ITU-T recommendations and IETF RFCs) refer to a byte (8 bits) as an octet.

OSI:

Open Systems Interconnection. The OSI model is a 7-layer protocol architecture for computer communication. Developed by International Organization for Standardization.

OSPF:

Open shortest path first. A routing protocol used within autonomous systems.

Packet:

A block of data. The information to be transmitted is divided into packets and sent over the network in a packet-switching network.

Packet switching:

Switching technology in which the information is divided into packets and transmitted from the source to the destination via packet switches. The packet switch takes the packet from an incoming channel, analyzes it, and based on the destination address of the packet, routes the packet to the appropriate outgoing channel.

PAN:

Personal area network. A PAN interconnects devices within a range of about 10 meters. PANs can be established in homes or offices.

PCM:

Pulse code modulation. In PCM, the signal is sampled at Nyquist rate, and the samples are quantized and converted into bit stream. For instance, voice signal has a bandwidth of 4kHz. The voice signal is sampled at 8000 samples per second, and each sample is coded with 8 bits (with 256 quantization levels). Using PCM, a voice signal can be digitized at 64kbps.

PCS:

Personal communication system. The cellular mobile communication system in North America.

Phoneme:

The smallest voice sound in a language. Most languages have about 40 to 60 phonemes.

Piconet:

When two or more Bluetooth-enabled devices come in the vicinity of one another, a piconet is formed. A piconent can support seven active devices.

POTS:

Plain old telephone service. The traditional fixed telephone service is referred to as POTS.

Protocol:

An established procedure for entities to communicate with each other.

PSK:

Phase shift keying. The phase of the carrier is changed based on the input bit stream. In binary PSK, binary 1 and binary 0 are represented by two phases of the carrier. In quadrature PSK, 00, 01, 10, and 11 are represented by four phases of the carrier.

Public key encryption:

An encryption mechanism in which there will be a public key and a private key. Public key is used for encryption and private key for decryption.

QoS parameters:

Quality of service parameters. The performance characteristics that define the service quality. Parameters such as delay, throughput, and packet loss can be specifed as QoS parameters.

Recommendations:

The standards of ITU-T are called recommendations.

Examples:

X.25 for packet switching network protocols, X.400 for message handling systems.

Repeater:

An entity that boosts the signal levels. For example, a GSM repeater boosts the radio signals transmitted by the BTS.

RFC:

Request for Comments. IETF specifications on various protocols are referred to as Request for Comments.

Router:

A network element in a packet-switching network that routes the packets toward the destination.

Routing:

The process of forwarding packets toward the destination.

RTCP:

Real Time Control Protocol. The protocol used above RTP for real-time communication in IP networks. Used for real-time voice and video communication over IP networks.

RTP:

Real-time Transport Protocol. The protocol used for real-time communication in IP networks. RTP is used for voice and video communication over IP networks.

Segment:

The packet at TCP layer is called a TCP segment.

SCO:

Synchronous connection oriented link. SCO links are used for connection-oriented services such as voice communication over Bluetooth links.

SDH:

Synchronous digital hierarchy. The standard proposed by ITU-T for optical transmission.

Signaling:

The information sent by the subscriber/switch for call setup, disconnection, and management, such as billing.

SMTP:

Simple Mail Transfer Protocol. Application layer for sending e-mail on TCP/IP networks.

SNA:

System network architecture. Network architecture developed by IBM.

SNMP:

Simple Network Management Protocol. Protocol used for network management in TCP/IP networks.

Source coding:

The process of coding the signals produced by a source. Text, voice, image, and video are encoded to reduce the data rate required for transmission.

SONET:

Synchronous optical network. The optical network standard developed by American National Standards Institute (ANSI).

Source routing:

A routing mechanism in which the source decides the route to be taken by each packet. The complete route will be embedded in the packet, and each router has to forward the packet based on this routing information.

SSMA:

Spread spectrum multiple access. A channel access mechanism in which high bandwidth is used to access the channel simultaneously. Frequency hopping and direct sequence are two examples of SSMA.

SSL:

Secure Socket Layer. A layer that runs above the TCP layer to provide secure communication over TCP/IP networks.

Steganography:

A technique used to send secret information embedded in text, voice, image, or video files.

Stop-and-wait protocol:

Protocol used for flow control and request for retransmissions. The sender sends a packet and waits for the acknowledgement. Only after the acknowledgement is received the next packet sent.

Switch:

A network element that takes data from incoming lines and puts it in the outgoing lines. A packet switch takes packets from incoming ports and puts them in outgoing ports based on the address contained in the packet.

TCP:

Transmission Control Protocol. The transport protocol used in TCP/IP networks. This layer provides end-to-end reliable data transfer between end systems. It takes care of flow control and error control and provides a connection-oriented service.

TDMA:

Time division multiple access. A channel access technique in which multiple users share the channel in different time slots. Each user is allowed to transmit data in a given time slot. The slots can be assigned permanently or dynamically only when traffic is there.

TDMA-FDD:

Time division multiple access-frequency division duplex. In TDMA-FDD, a pair of frequencies is used-one frequency for uplink and one frequency for downlink.

TDMA-TDD:

Time division multiple access-time division duplex. In TDMA-TDD, only one frequency is used for both uplink and downlink. The TDMA frame is divided into uplink time slots and downlink time slots.

TE:

Terminal equipment. The equipment used by end users.

Telnet:

The protocol for remote login in TCP/IP networks.

Throughput:

The effective data rate in a communication channel.

TLS:

Transport layer security. The protocol layer that runs above the TCP layer to provide secure communication in TCP/IP networks.

Transport layer protocol:

The protocol that provides end-to-end data transfer. TCP and UDP are examples of transport layer protocols.

TTL:

Time-to-live. A field in an IP datagram. This field decides the number of routers the packet can pass through before it is discarded. The default value is 64. At each router, this value is decremented by 1, and when it reaches a router with the value 0, that router discards the packet.

TTS:

Text-to-speech conversion. The process by which the text input to the computer is converted into speech form.

UDP:

User datagram protocol. The transport layer protocol on the Internet that provides connectionless service.

URL:

Uniform Resource Locator. The resource on a server that can be accessed over the Internet. The URL http://www.iseeyes.com contains the protocol and the resource.

Virtual circuit:

A logical connection established between two end points.

VPI: Virtual path identifier.

The identification assigned to a virtual path in an ATM network. The virtual path contains a number of virtual circuits.

VPN:

Virtual private network. A logical network of an enterprise that uses the Internet infrastructure.

WAN:

Wide area network. A network that spans a large geographic area. A WAN may interconnect network elements spread over a country or the world.

WAP:

Wireless application protocol. The WAP protocol stack is used to access Internet content by mobile devices.

Watermark:

See digital watermark.

WiFi:

Wireless Fidelity. The popular name given to an IEEE 802.11b wireless local area network.

WML:

Wireless Markup Language. A markup language for developing content that can be accessed by mobile devices using wireless application protocol.

X.25:

The ITU-T recommendation for wide area packet networks. X.25 provides a connection-oriented service.

X.28:

The ITU-T recommendation for an asynchronous terminal/PC to communicate with a packet assembler disassmbler in an X.25 packet-switching network.

X.121:

ITU-T recommendation for addressing in X.25-based packet networks. The X.121 address will have 14 digits.

X.400:

The ITU-T recommendation for message handling systems. This is the application layer protocol for e-mail in the ISO/OSI protocol architecture.

X.500:

ITU-T standard for directory services.

---