CS294-1: Mobile Computing and Wireless Networking Glossary

Amateur radio service:

A radio communications service that licenses radio operators with no pecuniary interest in radio communications.

ARQ:

A link layer protocol that provide reliable data transmission by retransmits link layer frames.

Broadcasting-satellite service (BSS):

A radio communications service in which signals transmitted or retransmitted by satellites are used for direct reception by the general public.

Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA):

A multiple access scheme that is used instead of CSMA/CD when a station is incapable of listening for a collision while transmitting.

Carrier Sense Multiple Access/Collision Detection (CSMA/CD):

A multiple access scheme (used in 802.3 LANs) that relies upon a station being able to listen for a collision while transmitting.

Code Division Multiple Access (CDMA):

A multiple access scheme that uses Direct Sequence Spread Spectrum (DSSS) code sequences as traffic channels in a common radio channel.

Cell Splitting or Cell Sectorization:

A method of increasing cell capacity by reducing the size of the cell. Splitting a cell reduces the diameter of the cell, while sectorization breaks the cell into (usually 120 degree) wedges.

Cellular Digital Packet Data (CDPD):

A contention-based packet access scheme for analog cellular channels. CDPD transmits and receives digital data using idle analog cellular channels.

Co-Channel Interference:

Interference between mobile terminals on the same or adjacent frequencies. A key design factor in designing a cellular system is to avoid or minimize cochannel interference.

Cyclic Redundancy Check (CRC):

A check sequence that is designed to detect packet transmission errors. The size of the check sequence affects its ability to detect different types of errors and multiple errors.

Direct Sequence Spread Spectrum (DSSS):

A modulation scheme that uses a pseudorandom binary sequence to modulate the frequency carrier of a signal. The relative rate between user data and the pseudorandom sequence is typically between 10 and 100 for commercial systems and on the order of 10,000 for military systems.

FCC Part 15.247 regulations:

Regulations specifying the usage restrictions for operation in the unlicensed ISM bands. The restrictions include the types of modulation schemes and power levels that may be used.

Foreign Agent (FA):

The Foreign Agent in a mobile IP system is the network contact point between a mobile computer and the rest of the network. The foreign agent provides an endpoint for packets that are tunneled to the mobile computer from the Home Agent. In some systems, the mobile computer may serve as its own foreign agent.

Frequency allocation:

A band of radio frequencies identified by an upper and lower frequency limit earmarked for use by one or more of the 38 terrestrial and space radiocommunications services defined by the International Telecommunication Union under specified conditions.

Frequency allotment:

The designation of portions of an allocated frequency band to individual countries or geographical areas for a particular radiocommunication service; for a satellite service, specific orbital positions may also be alloted to individual countries.

Frequency Division Multiple Access (FDMA):

A multiple access scheme that divides an allocated spectrum (see Frequency allotment) into different radio channels.

Frequency Hoping Spread Spectrum (FHSS):

A modulation scheme where both transmitter and receiver dwell on a one channel for a period of time and then hop from that channel to another one. The time spent on each channel is called a chip. The pattern of channel usage is usually based upon a pseudorandom binary sequence. The ratio between the chipping (or hopping) rate and the user data rate differentiates the two types of FHSS schemes. Systems where the chipping rate is higher than the user data rate are known as fast frequency hopper systems, while systems where the chipping rate is lower than the user data rate are known as slow frequency hopper systems.

Half-Duplex Operation:

Operating method in which transmission is possible in both directions (usually in an automated manner), but only in one direction at a time. See also Simplex Operation.

Handoff:

A communication channel will be changed to a new communication channel (without the user's intervention) as the mobile terminal moves from from one cell to another. Handoff may involve the assignment of a new frequency, time slot, and/or spreading code depending upon the channel access method.

Home Agent:

The Home Agent in a mobile IP system keeps track of a mobile terminal's current Foreign Agent. The home agent acts as a proxy for the mobile computer in its home network, receives connectiosn and packets destined for the mobile computer, and forwards them to the mobile computer.

Home Location Register (HLR):

The Home Location Register in a mobile communication system keeps track of a mobile terminal's current location. In mobile IP systems, the resolution is the mobile computer's current Foreign Agent. In mobile telephony systems, the resolution is usually the remote system; not the mobile telephone's current base station. See also Home Agent.

IEEE 802.11 protocol:

A media access protocol for wireless network access. The protocol specifies how multiple devices share a wireless transmission medium (e.g., RF or IR).

IS-54 protocol:

A digital TDMA media access protocol for mobile telephony.

Industrial, Scientific, and Medical Bands (ISM):

Three frequency bands in the US that are reserved for unlicensed operation (902-908 MHz, 2400-2483.5 MHz, and 5275-5850 MHz). FCC Part 15.247 regulations limit the types of modulation schemes and power levels that may be used.

Local Area Network (LAN):

A network encompassing a small (office floor or building) area.

Low earth orbit (LEO):

Any orbit around the earth substantially below the geostationary satellite orbit, generally below the geostationary satellite orbit, generally within several hundred km above the earth's surface and usually inclied to the equatorial plane.

Mobile IP:

A standard for allowing mobile computers to roam from one network to another while maintaing network connections.

Mobile Cellular Systems:

A high capacity system operating at 800-900 MHz or 2Ghz using a frequency reuse scheme for mobile telephony communications.

Mobile-Satellite Service (MSS):

A service that links mobile earth stations with base stations and with one another via one or more satellites.

Mobile Terminal:

A station in mobile system intended to be used while in motion or during halts at unspecified points.

Private Branch Office (PBX):

A private telecommunications switch that provides telephone services for an office, building, or campus size area.

Radiocommunications:

Telecommunications using radio waves.

Simplex Operation:

Operating method in which transmission is made possible alternatively in one direction of a telecommunications channel, for example, by means of manual control. See also Half-Duplex Operation.

Time Division Multiple Access (TDMA):

A multiple access scheme that uses time slots as traffic channels in a common radio channel.

Transmission Control Protocol (TCP):

A packet stream transmission protocol that supports reliable transmission of data and congestion control (to prevent network overload). TCP uses retransmission timers to detect lost packets and makes the assumption that packets are lost because of network congestion (and not link errors).

Uplink:

A radio link from a mobile terminal to a base station.

Visiting Location Register (VLR):

A database that keeps track of all the visting mobile terminals within a mobile telephony system.