Wireless Standards

Question 1

IEE 802.11 Standards

Answer 1

• 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

Question 2

2.4 Ghz

Answer 2

• 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

Question 3

5 GHz

Answer 3

• 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

Question 4

IEEE 802.11a

Answer 4

• Specifies use of 5GHz
• Multiplexed Carrier Scheme called OFDM (Orthogonal Frequency Division Multiplexing)
• Nominal data rate of 54 Mbps

Question 5

802.11b

Answer 5

• 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

Question 6

802.11g

Answer 6

• Upgrade from 802.11b
• Uses OFDM in 2.4 band
• Data rate of 54 Mpbs.
• Is backwards compatible with 802.11b

Question 7

802.11n

Answer 7

• 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

Question 8

802.11ac

Answer 8

• 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

Question 9

802.11ax

Answer 9

• 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

Question 10

Multiuser MIMO

Answer 10

• 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

Question 11

Cellular Radio

Answer 11

• 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

Question 12

LTE

Answer 12

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

Question 13

LTE-A

Answer 13

LTE-advanced

• intended to provide 300 mbps downlink
• Realworld is more like 90

Question 14

5g

Answer 14

• 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

Question 15

GSM

Answer 15

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

Question 16

CDMA

Answer 16

Code Division Multiple Access

• 2G Standard
• Each subscriber used a code to key the modulation of their signal
• Key is used by receiver to extract subscriber traffic from radio channel
• Handset is managed by provider, not SIM
• Largely restricted to Spring and Verizon

Question 17

HSPA+

Answer 17

Evolved High Speed Packet Access

• 3G standard
• Used on GSM networks
• Nominally supports speeds up to 168 mbs
• Marketed as 4 if data rate is better than 20 bmps

Question 18

CDMA2000/Evolution Data Optimized (EV-DO)

Answer 18

• Main 3G Standards for CDMA networks

- Supports 3.1 Mbps downlink and 1.8 mpbs uplink