Wireless Standards Flashcards
1
Q
IEE 802.11 Standards
A
- Wifi
- Defines the physical layer media by which data is encoded into readio signal using a modulation scheme
- Uses different carrier methods to provide resistance to interference from noise
- Uses CSMA/CA to cope with contention
- Half duplex
2
Q
2.4 Ghz
A
- One of the frequency bands in 802.11
- Better at penetrating solid surfaces and longer range than 5.
- More congested by other Wifi networks and bluetooth
- Max data rate is typically lower
3
Q
5 GHz
A
- Frequency band of 802.11
- Shorter max range
- Supports more channels and suffers from less congestion
- Overall higher data rate
- 23 non-overlapping channels, each 20 MHz wide
4
Q
IEEE 802.11a
A
- Specifies use of 5GHz
- Multiplexed Carrier Scheme called OFDM (Orthogonal Frequency Division Multiplexing)
- Nominal data rate of 54 Mbps
5
Q
802.11b
A
- Uses 2.4 and released at same time as 802.11a
- Inferior data rate of 11Mbps, but better established than 802.11a
- Subdivided into 14 channels
- Overlap ins considerable
- Only widely spaced channels are used 1,6,11
6
Q
802.11g
A
- Upgrade from 802.11b
- Uses OFDM in 2.4 band
- Data rate of 54 Mpbs.
- Is backwards compatible with 802.11b
7
Q
802.11n
A
- Increases bandwidth by multiplexing signals from 2-4 antennas using MIMO( Multiple input multiple Output)
- Can also be used to improve signal reliability.
- Can use 2.4 or 5 bands.
- Also allows 2 channels to be combined with Channel bonding
- 72 Mpbs, but up to 600 mbps for a bonded channel in optimal conditions
- Can operate in Highthroughput/Greenfield mode for maximum performance which can cause interference with legacy WLANs operating
- Renamed as Wi-fi 4
8
Q
802.11ac
A
- Only works in 5ghz band
- Can use 2.4 in mixed mode
- Wifi 5
- Goal is Gigabit ethernet throughput
- Supports more channel bonding, up to 80 or 160 MHZ channels and up to 8 spatial streams
- Use of radio spectrum is VHT (very high throughput)
- Marketing using AC values AC 5300 = 1000 mbps over a 40 Mhz. 2.4 Ghz band channel and 2 2167 mbps over 80 Mhz 5 Ghz channels
9
Q
802.11ax
A
- Wifi 6
- Uses more complex modulation and encoding to improve data sent by about about 40%
- Reinstates 2.4 band for IoT connectivity
- Goal was 10G speeds (AX11000), which can only be achieved through 6 Ghz Frequency band
10
Q
Multiuser MIMO
A
- Beamforming
- Solves issue of online one station being about to access AP at a time
- Wifi 5 and 6
- Allows MIMO to connect to multiple stations on beam path
11
Q
Cellular Radio
A
- Establishes connection to nearby cell or base station
- Operated by telecom companies
- Effective range of 5miles
- Work in 850 to and 1900 Mhz frequency bands in US
12
Q
LTE
A
Long Term Evolution
- 4G
- Converged Standard supported by GSM and CDMA network providers
- Must have SIM card used by network provider
- Max downlink of 150, 20 more realistic
13
Q
LTE-A
A
LTE-advanced
- intended to provide 300 mbps downlink
- Realworld is more like 90
14
Q
5g
A
- Uses different spectrum bands from low to and high
- Involves installing hundreds of smaller antennas
- Known as massive MIMO
- Real world range is 50 to 300 Mbps
15
Q
GSM
A
Global System for Mobile Communications
- 2G Standard
- Used Time division multiple access (TDMA)
- Each subscriber gets access to radio channel with a time slot
- Allows subscribers to use Subscriber identity module (SIM) and unlocked handset with chosen provider
- International and used by AT&T and T-mobile in US
