Cisco Wifund 200-355

Front 1

Frequency

Back 1

Number of times the signal makes a complete up and down cycle in 1 second

Front 2

Phase

Back 2

A measure of shift of a signal in time relative to the start of a cycle

Front 3

Wavelength

Back 3

Measure of the physical distance that a wave travels over one complete cycle

Front 4

Amplitude

Back 4

The height from the top peak to the bottom peak of the signals waveform

Front 5

Law of zero

Back 5

A value of 0 db means that two absolute power values are equal

Front 6

Law of 3s

Back 6

A value of 3 db means that the power value of interest is double the reference value. A value of -3 means the power value of interest is half the reference.

Front 7

Law of 10s

Back 7

A value of 10db means that the power value of interest is 10 times the reference value. A value of -10db means the power value of interest is 1/10 of the reference.

Front 8

EIRP

Back 8

Effective isotrophic radiated power - actual power level radiated from the antenna.

Front 9

RSSI

Back 9

Recieved signal strength indicator - receiving end of the signal. Receivers measure a signals power in dBm according to the RSSI scale

Front 10

Noise floor

Back 10

The average signal strength of the noise.

Front 11

SNR

Back 11

Signal to Noise ratio - the difference between the signal and the noise, measired in dB. Calculation is signal minus noise floor...20dB SNR is minimum to work.

Ex: signal is -54dBm. Noise is -90dBm

-54 - (-90) = 36dB = SNR

Front 12

Band

Back 12

A contiguous range of frequencies

Front 13

Bandwidth

Back 13

A range of frequencies used by a single channel or a single RF signal

Front 14

Barker 11 code

Back 14

An 11 bit sequence of encoded bits that represent a single data bit

Front 15

BSS

Back 15

Basic Service Set -

Wireless service provided by an AP to one or more associated clients.

Front 16

Carrier signal

Back 16

The basic, steady RF signal that is used to carry other useful information

Front 17

Channel

Back 17

An arbitrary index that points to a specific frequency in a band

Front 18

Chip

Back 18

A bit produced by a coder

Front 19

Coder

Back 19

A function that converts data bits into multiple encoded bits before transmission, to provide resilience against noise and interference.

Front 20

CCK

Back 20

Complimentary Code Keying:

An encoding method that takes either 4 or 8 data bits at a time to create a 6bit or 8bit symbol. The symbols are fed into DQPSK to modulate the carrier signal.

Front 21

dB

Back 21

Decibal:

A logarithmic function that compares one absolute measurement to another

Front 22

dBd

Back 22

The gain of an antenna, measured in dB, as compared to a simple dipole antenna.

Front 23

dBi

Back 23

The gain of an antenna, measured in dB, as compared to an isotrophic reference antenna.

Front 24

dBm

Back 24

The power level of a signal, measured in dB, as compared to a reference signal power of 1 milliwatt.

Front 25

Demodulation

Back 25

The recievers process of interpreting changes in the carrier signal to recover the original information being sent.

Front 26

DBPSK

Back 26

Differential binary phase shift keying:

A modulation method that takes 1 bit of encoded data and changes the phase of the carrier signal in one of two ways.

Front 27

DQPSK

Back 27

Differential quadrature phase shift keying:

A modulation method that takes 2 bits of encoded data and changes the phase of the carrier signal in one of four ways.

Front 28

DSSS

Back 28

Direct sequence spread spectrum:

A wireless lan method where a transmitter uses a single fixed, wide channel to send data.

Front 29

FHSS

Back 29

Frequency hopping spread spectrum:

A wireless lan method where a transmitter "hops" between frequencies all across a band.

Front 30

Hertz

Back 30

A unit of frequency equaling one cycle per second

Front 31

In phase

Back 31

The condition when the cycles of two identical signals are in sync with each other

Front 32

Isotrophic antenna

Back 32

An ideal, theoretical antenna that radiates RF equally in every direction

Front 33

Link budget

Back 33

Cumulative sum of gains and losses measured in dB over the complete RF signal path; a transmitters power level must overcome the link budget so that the signal can reach a receiver effectively.

Front 34

Modulation

Back 34

The transceivers process of altering the carrier signal according to some other information source.

Front 35

Narrow band

Back 35

RF signals that use a very narrow range of frequencies.

Front 36

Noise floor

Back 36

The average power level of noise measured at a specific frequency

Front 37

OFDM

Back 37

Orthogonal frequency-division multiplexing:

Data transmission method that sends data bits in parrallel over multiple frequencies within a single 20 mhz wide channel. Each frequency represents a single subcarrier

Front 38

Out of phase

Back 38

The condition when the cycles of one signal are shifted in time in relation to another signal

Front 39

Phase

Back 39

A measure of shift in time relative to the start of a cycle; ranges between 0 and 360 degrees

Front 40

QAM

Back 40

Quadrature amplitude modulation:

A modulation method that combines QPSK phase shifting with multiple amplitude levels to produce a greater number of unique changes to the carrier signal. The number of preceding the QAM name designates hiw many carrier signal changes are possible.

Front 41

RF

Back 41

Radio frequency:

The portion of the frequency spectrum between 3khz and 300ghz

Front 42

Sensitivity level

Back 42

The RSSI threshold (in dBm) that divides unintelligible RF signals from useful ones

Front 43

Spread spectrum

Back 43

RF signals that spread the information being sent over a wide range of frequencies.

Front 44

Symbol

Back 44

A complete group of encoded chips that represents a data bit.