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Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Access Point:
Access points are the devices which provide a connection between one or more wireless devices and a wired network.

Acknowledgement:
It is the reply from the receiver to the sender that the data was received successfully.

Adhoc network:
It's a type of network without any centralized control it is also called as basic server set or peer to peer network. In adhoc network, stations communicate directly with each other through the SSID.

AES:
Advanced Encryption standard is used to encrypt the data. It uses 128, 192 and 256 bit keys.

Authentication:
Authentication is a process of identifying the secure users. In a wireless network a station sends an authentication frame to another station if it wishes to begin secure communication.

Attenuation:
A loss of signal strength usually related to the distance the signal must travel. Radio signal attenuation may be due to atmospheric conditions, antenna design / positioning, obstacles, etc. Attenuation is measured in decibels.

Asynchronous (i.e. Not Synchronous):
A form of concurrent input and output communication transmission with no timing relationship between the two signals.

AWGN:
abbreviation for Additive White Gaussian Noise which is having uniform spectral density over a range of frequencies

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B

Bandwidth:
It is a measure of the significant spectral content.

Base station:
A transmitting/receiving station fixed at a location serving one or more subscriber stations.

Baseband signal:
A signal which is centered at DC (0 Hz) and unmodulated.

Beacon:
To keep the network synchronized access points or stations broadcast a type of packet called as Beacon.

BER:
Bit Error Rate (BER) defined as ratio of number of bits in error by the number of bits transmitted.

Bit Rate:
The speed at which bits are transmitted on a network, usually expressed in bits per second.

Bluetooth:
Bluetooth is one of the wireless personal area network standard that operates in the 2.4 GHz band and allows the portable personal devices to communicate within a short range.

BPSK:
Binary Phase shift keying abbreviated as BPSK is a modulation technique where the carrier is shifted by 180 degrees in accordance with a digital bit stream. “0” does not produce a phase transition where as “1” causes a phase transition to occur.

Broadband:
Term applied to broad bandwidth more than 1 MHz and supports data rates greater than 1.5 Mbps.

BSSID:
Basic server set identifier. A 48 bi t identifier used by all stations in a BSS in a frame header

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C

Carrier:
A high frequency signal used to modulate the message signal. Various parameters of the carrier can be modified such as phase, amplitude, frequency.

CCDF:
Complimentary cumulative distribution function.

CCITT:
Consultant Committee on International Telephone and Telegraph - An international organization which develops standards and defines interfaces for telecommunications.

CCK:
Complimentary Code Keying- A modulation scheme that transforms data blocks into complex codes and is capable of encoding several bits per block.

Chassis:
Chassis refer to the metallic body or frame which provides rugged and modular packaging for the system.

Chipset:
A group of integrated circuits (IC's) that are designed to work as a single entity.

Co channel Interference:
Undesired signals with frequency components that fall within the frequency range of the desired channel. Interference from a channel that is transmitting in the same frequency range.

Contention free period:
In a wireless network contention free period is the time when none of the stations are competing for transmission in other words when there is no conflict between stations. Once the contention free period is completed the Polled stations can transmit.

Convolution codes:
Convolutional codes are a class of codes which can detect and correct errors, where the code generated depends not only upon the present bits but also on the preceding bits in time.

CRC:
Cyclic redundancy check abbreviated as CRC is a check sum on integers (mod 2) and it's a common error checking protocol.

CSMA:
Carrier Sense Multiple Access - A listen before talk scheme used to mediate the access to a transmission resource. All stations are allowed to access the resource but are required to make sure the resource is free before transmitting.

CTS:
Clear to send (CTS) a signal from the receiving station to the transmitting station granting permission to transmit data. In a wireless network a station responds to a RTS with a CTS frame, providing clearance for the requesting station to send data.

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D

DAC (D/A converter) — DAC:
Digital to Analog Converter, An electronic device or a piece of software, often integrated , that converts a digital number or signal into a corresponding analog voltage or current

DAMA:
Demand Assigned Multiple Access - a technique for sharing satellite bandwidth among many users.

Decibel (dB):
unit for expressing a logarithmic measure of the ratio of two signal levels. It is most commonly used for expressing power, voltage and current ratios as follows: Power Ratio dB = 10 log (P1/P2),
Voltage Ratio dB = 20 log (V1/V2),
Current Ratio dB = 20 log (I1/I2).
dBW = decibels (power level) referenced to 1 watt.
dBm = decibels (power level) referenced to 1 milli watt; often used across 50 ohm input for receivers.
dBV = decibels (voltage level) referenced to 1 volt across 50 ohms.
dBuV = decibels (voltage level) referenced to 1 microvolt across 50 ohms.
dBuV/m = decibels (voltage level) referenced to 1 microvolt per meter.

DBPSK:
Differential Binary Phase Shift Keying is the modulation technique in which the binary data is encoded as phase shift differences between successive symbol periods. It is used for 1Mbps 802.11 transmission.

Decoder:
A piece of hardware or software that decodes the encoded data into the original format.

Downlink:
The direction from the base station to the subscriber station.

DQPSK:
Differential Quadrature Phase Shift Keying. A modulation method in which bits are encoded as phase shift differences between successive symbol periods. Four phase shifts are possible for an encoding rate of two data bits per symbol.

DSSS:
Direct Sequence Spread Spectrum. A transmission technique that spreads a signal over a wide frequency band for transmission.

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E

Electro magnetic Spectrum:
Electro magnetic spectrum is a band of electromagnetic waves arranged according to the wavelength and frequency.

Encoder:
A piece of hardware or software that encodes the data i.e. accepts the message bits and adds redundancy according to a prescribed rule there by producing encoded data at a higher bit rate.

Encryption:
Encryption is a process of converting the information in a format such that it is not readable if intercepted by a third party or unintended users. This is done using key at transmitting station which intended receiving station has in order to extract the information from received encrypted data.

Equalization:
Equalization is the process to shape the received pulses so as to compensate the effects of amplitude and phase distortions caused by imperfections in the transmission characteristics of the channel. It refers to any signal processing or filtering technique used to reduce ISI.

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F

Fading:
The variation in received signal's amplitude due to interference is called as fading.

FCC:
Federal Communications commission. The regulatory agency for United States.

Fidelity:
Faithfulness, accuracy. The ability of the electronic equipment to reproduce the signal exactly at its input with full accuracy

Fragmentation:
It's a process of breaking the large higher level packets into smaller packets to fit through the wireless channel.

Frame:
The format of aggregated bits from a medium access control (MAC) sublayer that are transmitted together in time. The Frame usually consists of representation of the data to be transmitted /received, together with other bits which may be used for error detection or control.

Frequency hopping:
Frequency-hopping spread spectrum (FHSS) is a method of transmitting signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver.

Frequency Offset:
Frequency offset is defined as the difference between the ideal frequency and measured frequency.

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G

Guard band:
Unused frequency spaces between channels which prevents overlapping of spectrum.

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H

Hertz:
A unit to measure the frequency. Cycles per second of a periodic signal.

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I

IEEE:
The IEEE - Institute of Electrical and Electronics Engineers, Inc. is a non-profit, technical professional association.

IEEE 802.11a/b/g:
are IEEE standards that define wireless LAN technologies.
802.11b operates in the 2.4-GHz radio spectrum and have a maximum data rate of 11 Mbps. 802.11a operates in the 5-GHz spectrum and have a maximum data rate of 54.Mbps. 802.11g operates in the same 2.4 GHz radio spectrum as 802.11b but at a rate of 54Mbps.

IEEE 802.15.4:
This IEEE standard defines the protocol and interconnection of devices via radio communication in a Wireless Personal Area Network (WPAN). 802.15.4 Operates in 868/915/2450 MHz band at a rate of 20/40/250 kbps.

IEEE 802.16:
IEEE 802.16-2004 standard released in June 2004 specifies the air interface of fixed broadband wireless access (BWA) systems supporting multimedia services.

Infrastructure network:
A type of network where wireless stations communicate via the access point.

Inter symbol Interference:
When the signal bandwidth is close to the channel bandwidth the pulses tend to overlap on each other this overlapping of pulses is defined as Inter symbol Interference and it is measured by eye patterns.

Intermediate Frequency:
Intermediate frequency is the difference between the incoming frequency and oscillator frequency. The output of oscillator is the intermediate frequency.

IP:
Intellectual Property - a proprietary design which companies license.

ISM band:
Abbreviated for Industrial, Scientific and Medical band. ISM band is a license free band which is set aside for Industrial, scientific and Medical equipments.

I/Q:
Abbreviated for “in-phase/quadrature-phase.” Signals that are fundamental products of individual In-phase and quadrature modulators, which are exactly 90 degrees out of phase.

Interoperability:
The ability of heterogeneous systems and networks to communicate and cooperate through specified standards.

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J

Jamming:
Jamming is defined as intentionally transmitting signals in a particular frequency band to disrupt reception of signals.

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K

None

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L

Line of sight:
In line of sight transmission the transmitting and receiving stations (antennas) can see each other. It's a clear path between transmitting and receiving stations.

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M

MAC:
Medium Access Control layer is the lower layer in OSI model prior to PHY layer. The primary functions of the MAC layer is to control and access the physical medium, and also perform fragmentation and de fragmentation of packets.

Microwaves:
The electromagnetic waves of very high frequency used for heating and communication purpose.

Modulation:
Modulation is the process by which some characteristics of the message signal are varied in accordance with the modulating wave.

Multipath:
In addition to direct path from transmitter to receiver there exist several indirect paths. The interference caused due to these indirect paths is called multipath.

Multiplexing:
Multiplexing is a technique where multiple channels are combined for transmission over a single transmission path.

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N

Node:
A connection point or a network junction, typically a computer or a station.

Noise:
Unwanted signal superimposed on a true signal.

Non line of sight:
In non line of sight transmission technique the stations/antennas (transmitting or receiving) need not see each other; the path is not clear which results in signal degradation.

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O

OFDM:
Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique in which a radio signal is divided into multiple narrow frequency bands to transmit large amounts of data. 802.11a and 802.11g use OFDM.

OFDMA:
Orthogonal Frequency Division Multiple Access. It's a logical extension of OFDM and a modulation/multiple access technique.

OQPSK:
Offset (Orthogonal) Quadrature Phase Shift Keying is an improvement over QPSK. In OQPSK technique the odd bits are delayed by half bit interval w.r.t the even bits.

OSI model:
Open Systems Interconnection Reference Model commonly known as OSI Model describes seven layers Physical Layer, Data Link Layer, Network layer, Transport layer, Session layer, Presentation layer and Application layer.

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P

Packet:
A unit of data. Each message sent between two network devices is often subdivided into packets by the underlying hardware and software. Depending on the protocol the packets have their own formats.

PBCC:
packet binary convolution coding

PCI:
Peripheral Component Interconnect abbreviated as PCI- is a high-performance expansion bus for PCs and work-stations.

PCMCIA:
Personal Computer Memory Card International association.

PER:
Packet error rate (PER) is an average fraction of transmitted packets that are not detected correctly.

Phase Offset:
Difference in reference phase of transmitted waveform and received waveform is called phase offset, expressed in degree.

PHY:
Common IEEE abbreviation for the PHYsical layer.

Pilot:
A single frequency signal which is transmitted for synchronization or reference purposes.

PLCP:
Physical Layer Convergence Procedure which maps the frames to the medium.

PN Sequence:
A Pseudorandom Noise (PN) sequence is a deterministic sequence known to both transmitter and receiver, though it's a deterministic signal it appears as a random sequence with probabilistic properties.

Point to point:
A dedicated path between two communication devices.

PPDU:
PHY protocol data units (PPDU). Complete PLCP frame, including PLCP headers, MAC headers, the MAC data field and the MAC and PLCP trailers.

Preamble:
A preliminary signal that is transmitted to control signal detection and achieve synchronization between transmitters and receivers in wired and wireless networks.

Protocol:
A set of rules and regulations for communication.

PSDU - PLCP service data unit (PSDU):
Unit which represents the contents of a PPDU.

Pulse Shaping: I
t is a process to alter the pulse shape in other words tailoring the pulse shape in a controlled manner to overcome ISI.

PXI:
PXI (PCI eXtensions for Instrumentation) is a rugged PC-based platform for measurement and automation systems. It is the open, multivendor standard.

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Q

QAM:
Quadrature Amplitude Modulation is a modulation technique which uses different phases such as 16, 32, 64, and 256 and each state is defined by a specific amplitude and phase.

QOS:
Quality of Service (QoS) refers to the capability of a network to provide better service

QPSK:
Quadrature Phase Shift keying. A modulation method that encodes bits as phase shifts. One of four phase shifts can be selected to encode two bits.

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R

Randomization:
Randomization is a process to systematically or randomly reorder (shuffle) the data. Randomization starts with the original data and calculates the appropriate test statistic on each reordering.

Receiver Sensitivity:
The ability of the receiver to pick up the weakest signal.

RF:
Abbreviated for Radio Frequency.

Root Mean Square (RMS):
The square root of the average value of the square of the instantaneous signal amplitude; a measure of signal amplitude.

Roaming:
Roaming is the term used to define the ability of a station to move from one access point to another without being interrupted.

RSSI:
Receiver Signal Strength Indication

RTS:
Request to send (RTS) a signal from the transmission station to the receiving station requesting permission to transmit data. In wireless networks a station sends a RTS frame to another station as the first phase of a two-way handshake necessary before sending the data

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S

Sampling rate:
Sampling rate defines the no of samples taken from a continuous signal

Shot noise:
Noise introduced in a communication system due to random fluctuations in the electrons.

SSID:
SSID is Service Set Identifier, it's a unique name shared among all clients and nodes in a wireless network. The SSID address is identical for each clients and nodes in the wireless network.

Synchronous:
A form of communication transmission with a direct timing relationship between input and output signals. The transmitter and receiver are in sync and signals are sent at a fixed rate.

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T

TCP/IP:
Transmission control protocol (TCP)/Internet protocol (IP). TCP guarantees delivery of data and also guarantees the order in which they were sent while IP takes care of the addressing.

TDMA:
Time Division Multiple Access (TDMA) - A method of digital wireless communications transmission allowing a large number of users to access a single radio-frequency channel without interference. Each user is given a unique time slot within each channel.

Thermal noise:
Noise introduced in a communication system due to movement of electrons.

Topology:
Geometrical arrangement of nodes in a network. There are various kinds of topologies like star, mesh and ring.

Turnaround time:
The time required to transmit a message and receive its acknowledgement.

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U

Uplink:
it's the transmission path from base station to a satellite

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V

Viterbi decoder:
Viterbi decoder is FEC (Forward error correction) Device, which will decode the convolutional encoded data, and correct random single bit errors.

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W

WEP:
Short for Wired Equivalent Privacy, a security protocol for wireless local area networks (WLANs) defined in the 802.11b standard.

WiMAX:
WiMAX is an acronym for Worldwide interoperability for Microwave Access a standards-based wireless technology which provides broadband connections over long distances.

WLAN:
Wireless Local Area Network. A Wireless LAN (WLAN) is a flexible data communication system implemented as an extension to or as an alternative for a wired LAN. With WLANs, users can access shared information without looking for a place to plug in. Wireless LAN systems provide WLAN users access to real-time information anywhere in their organization at work, at home and on road. WLANs combine data connectivity with user mobility through simplified configuration.

WLL:
Wireless Local loop - is a system that connects subscribers to the public switched telephone network (PSTN) using radio signals.

WPAN:
Wireless Personal Area Network. Wireless personal area networks (WPANs) are short range wireless networks that can be used to exchange information between devices in the reach of a person and his personal space within 10-20 meters.

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X

None

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Y

None

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Z

ZigBee:
The best example representing WPANs is the recent industry standard: ZigBee. The ZigBee Alliance is an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard. The goal of the ZigBee Alliance is to provide the consumer with ultimate flexibility, mobility, and ease of use by building wireless intelligence and capabilities into every day devices. ZigBee and the underlying IEEE 802.15.4 promise to give the market a cost-effective standards-based wireless network that supports low data rates, low power consumption, security, and reliability.

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