Wireless Standards Flashcards
Which body creates and maintains wireless operationsla standards?
IEEE
What does the Wi-Fi Alliance do?
Tests for WLAN interoperability
Who produces common wireless standards in Europe
European Telecommunications Standards Institute
what are the industrial and scientific wireless bands?
900Mhz and 2.4Ghz
Which modulation technique helps to prevent eaves dropping of calls and provided a bandwidth between 14.4K to 64Kpbs.
Time Division Multiple Access
Describe the key feature of Code Division Multiple Access cellular modulation
Assigns a unique code to each transmission and spreads it across the frequency spectrum. Allowing a cellular call to make use of all frequencies.
Which is the most widely deployed standard offering 11Mbps?
802.11b
Users connecting to an AP using 802.11g complain that their speed is slow, what could be the problem?
There is someone connected using 802.11b which forces lower speed modulation
What is the word used to describe actual data throughput?
Goodput
What is the key problem with 802.11b communication?
The Data Link layer uses a CMSA/CA option called Request To Send/Clear To Send which has a lot over overhead.
When installing Wireless APs, what strategy should you employ when it comes to setting channels? Why?
Each AP should use the channel that is farthest from the channel used by the adjacent AP. This reduces interference.
Which feature of 802.11h automatically detects radar frequencies and shuts down wireless channels that are close to that frequency?
Dynamic Frequency Selection
What feature of 802.11h can save energy and reduce interference at the same time?
Transmit Power Control
What is MIMO and which wireless standard uses it?
Multiple-Input Multiple-Output sends several frames over several antennas over several paths that are recombined by several antennas. (spatial multiplexing) It allows for faster throughput
Which component of 802.11n saves overhead by allow a greater amount of packets to be send before acknowlegment?
MAC Efficiency/Block acknowledgement
How many MIMO spatial streams can 802.11n support?
4
Which wireless standard supports up to 8 antennas?
802.11ac
What is the difference between the number of antennas and spatial streams?
Spatial streams are the number of data-streams that a group of antennas can transmit/receive.
How are 802.11ac frames identified?
By 4 fields in the frame indicating VHT (Very High Throughput)
List the wireless modulation techniques in order of performance
1) OFDM (Orthogonal Frequency Division Multiplexing)
2) DSSS (Direct Sequence Spread Spectrum)
3) FHSS (Frequency Hopping Spread Spectrum)
4) IR
Which modulation type does 802.11b use?
DSSS
What modulation type does Bluetooth use?
Frequency Hopping Spread Specturm (FHSS)
List the wireless standards in the general order of performance where 1 is the lowest
1) 802.11
2) 802.11b
3) 802.11g
4) 802.11a
5) 802.11n
6) 802.11ac
Which IEEE extension allows up to 23 non-overlapping channels
802.11h
Which IEEE committee is implemented as WPA2?
802.11i
Which wireless standards use fields in frames designating them as High Throughput?
802.11a and 802.11g
If the transmitting medium is not clear when a wireless host checks to transmit, what happens?
1) The host will use the random back-off algorithm countdown timer
2) When the counter reaches zero it will check the medium. If it is clear, it will transmit
An access point sees that a frame is bound for a host on the wired LAN on a different segment. What 2 things does it do with the frame to get it to the destination?
1) It replaces the 802.11 MAC header with an ethernet header using it’s own MAC address as the source address
2) It sets the destination MAC address as the MAC address of the default gateway
Which IEEE standard is an extension to 802.11a and contains signal management features called DFS (Dynamic Frequency Selection) and PTC (Power Transmit Control)
802.11h
Why are standards using 5Ghz frequency faster than 2.4Ghz?
1) 5ghz band is immune to interference coming from a variety of equipment operating near the 2.4Ghz band
2) Allows for up to 23 non-overlapping channels
3) Higher frequencies can transmit more data in the same amount of time
What does the 2*2 mean in relation to MIMO?
2 antennas on the WAP and 2 antennas on the client are used.
Which two wireless standards support MIMO?
802.11n and 802.11ac
HPSA+ is a variation of what?
3G cellular
What is the maximum data throughput downstream and upstream for LTE/4G?
299Mbps down, 75.4Mbps up
CDMA allows simultaneous voice and data, TRUE or FALSE?
FALSE
List the 6 wireless technologies that facilititate IoT
1) Z-wave
2) Ant+
3) Bluetooth
4) NFC (near Field Commuication)
5) RFID
6) 802.11
NFC is typically used for when using the mobile phone to tap and pay - TRUE or FALSE
TRUE
NFC requires a nominal distance of what to work?
4 centimeters
What is the current version of Bluetooth, why was it created and what is the maximum distance it can communicate at?
Bluetooth 5.0.
To support IoT
800 feet
What is the max distance a passive RFID tag can be read at?
600 feet
What is the maximum speed of Bluetooth 4?
What is the max speed of bluetooth 5?
25Mpbs
100Mbps
If an IoT device has to connect to a network, what is the most common wireless technology used?
802.11
How many frequency bands does RFID use? Why?
4
Each band has a varying distance capability and so allows for tailoring of applications
Which RFID transponder can work at a greater distance, Active, or Passive?
Active. Active transponders had a built in power source.
Which wireless communication protocol is often used in home automation?
Z-wave
Which wireless protocol is often used in health and fitness equipment?
ANT+
Z-wave functions in what kind of topology?
Mesh
