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Fragen in diesem Quiz (21)
1MIMO: multiple-input and multiple-output
OFDM:Orthogonal frequency-division multiplexing
ERP: Effective radiator power
DSSS: Direct-sequence spread spectrum
HT:
RSN: Robust security network
WEP: Wired Equivalent Privacy
WPA: [blank_start]Wi-Fi Protected Access[blank_end]- AWi-Fi Protected Access
2The unlicensed national information infrastructure U-NII unlicensed frequency has 300MHZ total bandwidth. The most in the category! In the 5 GHz range.
- ARichtig
- BFalsch
3 Industrial, Scientific, and Medical (ISM) Band
- ALicensed bands
- B900 MHz band: 902 – 928 MHz (26 MHz wide)
- C2.4 GHz band: 2.4 – 2.5 GHz (100 MHz wide)
- D5.8 GHz band: 5.725 – 5.875 GHz (150 MHz wide)
- E234.5 MHz total
- FCordless Telephone, WLANs , Wireless Public Branch Exchanges
- G2.8 GHz band: 2.8 – 2.9 GHz (100 MHz wide)
4900 MHz ISM band Internationally could interfere with Global System for Mobile Communications (GSM) mobile phones
- ARichtig
- BFalsch
52.4 GHz Industrial, Scientific, and Medical (ISM) Band
- AMost common Wi-Fi band
- BUsed by 802.11 b, g, n
- Cmicrowave ovens, cordless home telephones, baby monitors, video cameras
- DFHSS, DSSS, HR-DSSS, ERP, HT radios
65.8 GHz ISM Band
- A5.725-5.875 GHz
- BSame as UNII-3 band that spans 5.725-5.825
7Contains three 5 GHz bands Plus extended one
Defined as Lower, Middle, and Upper UNII bands UNII 1 (Lower)
UNII 2 (Middle)
UNII-2E (extended)
UNII 3 (Upper)- ARichtig
- BFalsch
8White Space White Fi. Will provide greater range because of lower frequencies
below 1 GHz. Due to lower frequencies, data rates will be less than other Wi- Fi PHYs- ARichtig
- BFalsch
9Tri-band radios will support 2.4 GHz, 5 GHZ, and 60 GHz with seamless handoff
- ARichtig
- BFalsch
10Narrowband
- Alittle bandwidth
- Bintentional jamming or unintentional interference can cause disruption in signal.
- Chigher power transmission
- Drequires licence to limit interference
- Ehigh bandwidth
11[blank_start]Hopping Sequence:[blank_end] Predefined hopping pattern or set
[blank_start]Dwell Time:[blank_end] Period of time that the transmitter stays on a channel and transmits data
[blank_start]Hop Time:[blank_end] The time it takes for the transmitter to change from one frequency to another
- AHopping Sequence:
- BDwell Time:
- CHop Time:
12Direct sequence spread spectrum
- ATransmits signal across a wide frequency range
- B2.4 GHz ISM band
- CHigh-Rate DSSS (HR-DSSS) 5.5 and 11 Mbps
- DDSSS provided 1 and 2 Mbps
- ELike a digital signal, narrow, wide
- Flike analog signal, narrow, wide
13Simple Spread Spectrum: Transmitter
- Anarrowband data signal spread by Wideband chipping sequence.
- Ba bit of data converted into a series of chips
- Cdata + spreading chip= spread signal
- Dspread signal + spreading chip --> data
Wideband received signal at receiver is desperado with Wideband chipping sequence.
14Despreading & Processing a using spread spectrum
- AThe Wideband signal of the desired user is mixed with Wideband interference from other users and thermal noise.
- BThrough process of despreading a filter is applied to this jumbled signal. A narrowband signal from the desired user is extracted
15CCK code used in HR-DSSS is faster data rate than Barker code. CCK uses a complex code that uses 8 chips to encode. Barker = 11 chips to encode.
Barker: DSSS: DBPSK
CCK: HR-DSSS: DQPSK- ARichtig
- BFalsch
16OFDM (ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING)
- Anot a SPREAD SPECTRUM TECHNOLOGY
- BDivides bandwidth into 52 subcarriers. Each 312.5KHz wide
- C48 subcarriers transmit data
4 pilot carriers (ref for phase and amplitude) - D802.11a 802.11g channels
172.4 GHz Channels
- A14 channels each 22 MHz
- Bchannel reference by centre freq
- Cdistance b/w channels is 5MHz
- DChannels don't overlap if separation is 5+channels
18In an 11 channel environment, channel 1, 6, and 11 is the only three channel plan that does not overlap. Channels need a minimum of 25 MHz separation between center frequencies to be nonoverlapping
- ARichtig
- BFalsch
19Channel 1 in 2.4 starts at 2.412 remaining centre frequency calc. Add 5. 2: = 2.417.
- ARichtig
- BFalsch
20Throughput < Bandwidth
Data rate = width
802.11 is half duplex, throughput is approx. 50% less data rate
If 54 Mbps link, 20 Mbps throughput, 5 people on channel. Each 4 Mbps data rate- ARichtig
- BFalsch
21What does Throughput not depend on:
- Afrequency bandwidth
- Bdata encoding
- Cmodulation
- Dmedium contention
- Eencryption
- Fnumber of current users
- Gthroughput filter
Informationen
- Beschreibung
- Quiz am Ohne Titel, erstellt von Upma Sharma am 06/11/2018.
- Autor
- Upma Sharma
- Sprache
- English
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- 0
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