Ch. 4 Wireless Networking

Question 1

WLAN

Answer 1

Wireless Local Area Network

Extension of a computer networs into the radio frequency world.

Provides increased flexibility and mobility for connecting to a network.

Increased Security issues

Question 2

IEEE 820.11 WIRELESS LAN STANDARD

Answer 2

Has a higher data rate

Defines teh physical (PHY) layer, the medium access control (MAC) layer and the media access control (MAC) management and protocols

Advantages include:

A cost effective networking media for use in areas that are difficult or too costly to wire

User mobility in the workplace

Question 3

THE PHY (PHYSICAL) LAYER DEFINES THE FOLLOWING

Answer 3

The method of transmitting the data, which can be either RF or infrared (infrared rarely used)

The MAC layer defined

The reliability of the data service

Access control to the shared wireless medium

Protecting the privacy of the transmitted data

Question 4

ACCESS POINT

Answer 4

A transceiver used to interconnect a wireless and a wired LAN

Helps improve the performance of the Basic Service Set

The access point is a transmit/receive unit (transceiver) that interconnects data from the wireless LAN to the wired network.

Provides 802.11 MAC layer functions and supports bridge protocols.

Usually uses a RJ-45 jack for connecting to the wired network.

Question 5

FHSS

FREQUENCEY HOPPING SPREAD SPECTRUM

Answer 5

• The transmit signal frequency changes based on a psudorandom sequence.
• Uses 79 channels each 1MHz wide in the ISM 2.4Ghz band.
• Requires that the transmitting and recieving units know the hopping sequence so that a communication link can be established and synced
• Typically 1mbps and 2mbps
• Not commonly used anymore for wireless LANs

Question 6

ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING

OFDM

Answer 6

• Another technique used in the 802.11 standard
• basic idea is to divide teh signal bandwith into smaller subchannels and to transmit the data over these subchannels in parrallel
• Sub channels can be overlapping, but they will not interfere with each other.
• Mathmetically orthogonal which yields uncorrelated or independent signals

Question 7

WI FI

Answer 7

• Stands for Wireless Fidelity
• Wi-Fi Alliance an organization taht tests and certifies wireless equipment for compliance with the 802.11x standards
• Most Common wireless standards: 802.11a (Wireless A), 802.11b (Wireless B), 802.11g (Wireless G) 802.11n (wireless n)

802. 11a, data transfer rates up to 54Mbps range up to75ft
803. 11b rates up to 11Mbps with ranges 100-150ft
804. 11g rates up to 54Mbps and range up to 150ft
805. 11n rates over 200+Mbps

Question 8

SSID

Answer 8

Used by a wireless 802.11 LAN device to identify what wireless data traffic is allowed to connect to the network.

*Wireless set identifier

Basically a password

Question 9

SPATIAL DIVERSITY

Answer 9

WHEN AN ACCESS POINT HAS 2 ANTENNAS IMPROVING RECEIVED SIGNALS GAIN AND PERFORMANCE

Question 10

SITE SURVEY

Answer 10

PERFORMED TO DETERMINE THE BEST LOCATION FOR PLACING THE ACCESS POINTS TO PROVIDE MAXIMUM RADIO FREQUENCIES COVERAGE FOR TEH WIRELESS CLIENTS

DONE INDOORS AND OUTDOORS

Question 11

INDOOR

SITE SURVEY

Answer 11

• ELECTRICAL POWER
• WIRE NETWORK CONNECTION POINTS
• ACCESS POINT PLACEMENT
• RF COVERAGE-USER MOBILITY
• BANDWITH SUPPORTED
• IDENTIFY AN SIGNIFICANT RF INTERFERENCE

Question 12

OUTDOOR

SITE SURVEY

Answer 12

• ELECTRICAL POWER (BASE ACCESS PT)
• CONNECTION BACK TO THE HOME NETWORK
• ANTENNA SELECTION
• BANDWITH SUPPORTED
• RF COVERAGE
• IDENTIFY ANY SIGNIFICANT RF INTERFERENCE

Question 13

LOSS OF ASSOCIATION

Answer 13

“OUT OF RANGE” WITH ACCESS POINT

Question 14

WiMAX

Answer 14

A broadband wireless system based on the IEEE 802.16e standard

Worldwide Interoperability for Microwave Access

Broadband wireless access BWA for fixed and mobile stations and can provide a wireless alternative for last mile broadband access in 2Ghz - 66Ghz frequency range

Fixed stations up to 30miles and mobile 3 - 10 miles

Internationaly the Wimax frequency standard is 2.5Ghz

USA uses both unlicensed 5.8Ghz and the licensed 2.5Ghz

Question 15

Securing Wireless LANS

Answer 15

WEP, Wireless Equivalent Privacy, used to encrypt and decrypt wireless data packets, the exchange and return verifies that the client has proper WEP Key

WPA, Wifi Protected Access and it supports the user authentication provided by 802.1x and replaces WEP as the primary way for securing wireless transfers.*Higher level of security