2.4 Wireless Standards And Tech

Question 1

GSM

Answer 1

Global System for Mobile Communication (GSM)-based phones use Time Division Multiple Access (TDMA). GSM subscribers can use a subscriber identity module (SIM) card on an unlocked handset.

Question 2

LTE/4G

Answer 2

Long Term Evolution (LTE) is a converged 4G standard supported by both the GSM and CDMA network providers, but the network providers must install a SIM card on the phone.

4G or Long Term Evolution (LTE) is theorized to have a maximum download speed of 150 Mbps but currently performs real-world at around 20 Mbps.

Question 3

CDMA

Answer 3

Code Division Multiple Access (CDMA) handsets do not use SIM cards. The providers manage the handset. CDMA requires each subscriber device to use a code to key the modulation of their signal.

Question 4

3G

Answer 4

3G is a cellular technology also known as CDMA2000/Evolution-Data Optimized (EV-DO). CDMA network providers use this, which can support a 3.1 Mbps downlink and 1.8 Mbps uplink.

Question 5

5G

Answer 5

5G real-world speeds range from about 50 Mbps to 300 Mbps currently. 5G uses different spectrum bands from low (sub-6 GHz) to medium/high (20-60 GHz).

Question 6

2G

Answer 6

2G cellular data service was capable of around 14.4 Kbps. 2G was made available with two formats during its inception: Global System for Mobile Communication (GSM)-based phones and TIA/EIA IS-95 (cdmaOne)-based handsets.

Question 7

MIMO antennas

Answer 7

Multiple Input Multiple Output (MIMO) is the use of multiple antennas to boost bandwidth and is identified by AxB:C notation. A is the number of transmit antennas, B is the number of receive antennas, and C is the number of simultaneous transmit and receive streams.

Multiple Input Multiple Output (MIMO) wireless technology is used in 802.11n/ac and 4G standards. The maximum possible is 4x4:4, but common configurations are 2x2:2 or 3x3:2.

With Multiple Input Multiple Output (MIMO), having more transmit and receive streams than spatial streams helps to improve signal reliability, rather than boosting bandwidth.

With Multiple Input Multiple Output (MIMO), both the transmitter and receiver must support the same number of streams.

Question 8

Yagi antenna

Answer 8

A Yagi (a bar with fins) antenna is a unidirectional signal that is useful for point-to-point wireless bridge connections. This is common for outdoor use and can boost radio signals across long distances.

Question 9

Torus antenna

Answer 9

“Donut”

A torus (donut) antenna is similar to those round wireless routers that businesses use to mount in an office ceiling. This is not ideal for outdoor use.

Question 10

WPA2-personal

Answer 10

Wi-Fi Protected Access version 2 (WPA2)-Personal uses a pre-shared key (PSK) that all users will use to connect to the access point (AP). WPA2, in general, uses Wi-Fi encryption with Advanced Encryption Standard (AES) and Cipher Block Chaining Message Authentication Code Protocol (CCMP).

Question 11

WPA-enterprise

Answer 11

WPA-Enterprise utilizes the first version of WPA that uses the RC4 stream cipher to encrypt traffic. Users authenticate with their account credentials. This is a lower encryption standard than WPA2.

Question 12

Internal DNS

Answer 12

Internal domain name system (DNS) zones refer to the domains used on a private network. As the site uses the same domain name as AD, an A record for ftp needs to be created internally to point to the public ftp server address.

Question 13

External DNS

Answer 13

External domain name system (DNS) zones refer to records that Internet clients must be able to access.

Question 14

DNS forwarder

Answer 14

A forwarder transmits a client query to find a host to another domain name system (DNS) server and routes the replies it gets back to the client.

Question 15

802.11g signal format

Answer 15

DSSS and OFDM

Question 16

802.11a signal format

Answer 16

OFDM

Question 17

802.11b

Answer 17

CCK
(Variation of CDMA that is based on DSSS)

Question 18

Patch antenna

Answer 18

Radio antenna with a low profile, which can be mounted on a flat surface.
-provides coverage in limited angle pattern.
-can be directional or omnidirectional, but directional antenna should be used for a connection between 2 buildings.

Question 19

Whip antenna

Answer 19

A vertical omnidirectional antenna that is usually utilized in indoor environments.
-cannot be used for directional use cases.

Question 20

Captive portal

Answer 20

-implemented using HTTP redirect, ICMP redirect, or DNS redirect usually.
-using 802.1x and a database server like Radius in the back so if user can’t authenticate, it is because of that.