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CIT228 Ch 5

CIT228 Wireless Networks Chapter 5 Physical Layer Stds

16-level quadrature amplitude modulation (16-QAM) A modulation technique that sends 16 different signals simultaneously.
2X mode A proprietary transmission scheme that doubles the effective rate of an 802.11a network.
64-level quadrature amplitude modulation (64-QAM) A modulation technique that can transmit 1.125 Mbps over each of 48 subchannels.
bandwidth The difference between the upper and lower frequencies.
Barker code The bit pattern used in direct sequence spread spectrum (DSSS)
channel A numeric value assigned to a frequency range.
chipping code The bit pattern used in direct sequence spread spectrum (DSSS)
colocation Sharing a frequency band between similar devices.
communication resilience Term used to describe transmissions that are less prone to interference.
complementary code keying (CCK) A coding technique used in 802.11b networks that consists of a set of 64 8-bit code words.
convolutional coding rate A type of error-correcting code.
differential binary phase shift keying (DBPSK) A two-level phase shift key used in 802.11b networks.
differential quadrature phase shift keying (DQPSK) A four-level phase change used in 802.11b networks.
direct sequence spread spectrum (DSSS) A wireless modulation technique that uses an expanded redundant code to transmit each data bit.
dwell time The amount of time that a transmission remains on a specific frequency in FHSS.
Dynamic Frequency Selection (DFS) A technology in which IEEE 802.11n WLANs using 40-MHz channels can automatically move to another channel or switch to 20-MHz operation to minimize interference.
extended rate PHYs (ERP) A mandatory mode for the faster 54 Mbps in IEEE 802.11g.
Forward Error Correction (FEC) An IEEE 802.11a error correction technique that transmits a secondary copy along with the primary information.
frequency-hopping spread spectrum (FHSS) A modulation technique that uses a range of frequencies that change during the transmission.
full-channel FHSS A FHSS technology in which the devices use a minimum of 75 hop channels.
guard interval (GI) A delay built-in into the receiver to allow for late-arriving symbols.
High-Rate DSSS (HR-DSSS) Transmission rates above 2 Mbps in IEEE 802.11b.
hopping code The sequence of changing frequencies in FHSS.
hop time The time it takes to change a frequency in FHSS.
intersymbol interference (ISI) Signal interference as a result of multipath transmission.
microseconds (μs) One millionth of a second.
milliseconds (ms) One thousandth of a second.
Modulation and Coding Scheme (MCS) A system that assigns a numeric value to each of the 77 possible transmission combinations IEEE 802.11n.
multiplexing The process of sending multiple signals simultaneously.
narrowband transmission Radio signals that are sent on only one radio frequency or a very narrow portion of the frequencies.
Open Systems Interconnection (OSI) reference model A seven-layer model that conceptually illustrates the steps of networking.
orthogonal frequency division multiplexing (OFDM) A modulation technique that splits a single high-speed digital signal into several slower signals running in parallel.
PBCC-22 (Packet Binary Convolutional Coding) An optional 802.11g technique for transmitting at 22 Mbps.
Phased Coexistence Operation (PCO) An optional IEEE 802.11n technology that alternates between using 20-MHz and 40-MHz channels.
Physical Layer Convergence Procedure (PLCP) A Physical layer sublayer that reformats the data received from the MAC layer (when transmitting)
Physical Medium Dependent (PMD) A Physical layer sublayer that defines the standards for both the characteristics of the wireless medium and the method for transmitting and receiving data through that medium.
primary channel The first channel of two bonded IEEE 802.11n channels.
quadrature phase shift keying (QPSK) An IEEE 802.11a modulation technique that increases the amount of data encoded to 250 Kbps per channel.
reduced-channel FHSS A FHSS technology in which the devices use fewer than 75 hop channels.
secondary channel The second channel of two bonded IEEE 802.11n channels.
spectral efficiency The efficiency of the radio measured in the number of bits per hertz.
spread-spectrum transmission A technique that takes a narrow, weaker signal and spreads it over a broader portion of the radio frequency band.
symbols Radio frequency signals.
transmit power control (TPC) An IEEE 802.11a technology to reduce interference.
turbo mode A proprietary transmission scheme used to double the effective rate of an 802.11a network.
variable guard interval (VGI) An IEEE 802.11n technology that uses a reduced guard
interval of 400 nanoseconds.
Created by: Leisac