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CIT228 Ch 5
CIT228 Wireless Networks Chapter 5 Physical Layer Stds
| Term | Definition |
|---|---|
| 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. |
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