Challenges of Wireless LAN

spatial multiplexing power saving?

power saving technology that automatically reduces the power consumed by radios when data not being transferred, done by shutting down all but one radio when not in use

define effective area

the optimal physical area in range that the antenna can operate in

802.11B max transfer rates

up to 1,2 or 11Mbps

what standard defines how Ethernet works over wireless connections

IEEE 802.11

what does beamforming allow

allows the transmitter to focus its signal on a single receiver

WiMAX cell radius

between 3-10km

an ounce of protection

application layer encryption for all communication or TCP/IP layer => IPSEC; sectors and yagis will help from signal leaking into undesired areas; don't boost signals, prevent hot spots

wireless network devices are unlicensed devices, what is a precaution of this

because of low power, range of transmitted signal is limited; causing there to be a high potential of interference with nearby devices

what is MIMO

multiple input multiple output (MIMO) is key component of 802.11N devices

wireless works best when....

there is an unobstructed, clear line of sight between the two points of operation

outdoor point-to-point

used to connect wired LANs between buildings up to 20km apart

a wireless installation consists of what

very low power radio transmitters and radio receivers

certified interoperability supplied by who?

The WiFi alliance is the organization that has certified interoperability since June 2007

WiMAX speeds

1st gen = 40Mbps, 2nd gen = 300 Mbps, user can expect 1-5Mbps, currently found in notebooks and PDAs

wireless devices operate at what two frequencies

2.4Ghz and 5.2Ghz radio frequency band -- can operate at both

IEEE 802.11 Throughput "rated"?

The rated throughput in Mbps of a wireless device can be considerable more than actual throughout at any given time

WAP advantages

WAP does better job of "managing" a network for improved throughput, WAP has ability to adjust throughput for each station

two sources of wireless network threats

accidental access, deliberate access

802.11 allows devices to operate as what two things

ad hoc or client/server infrastructure devices

spread spectrum characteristics

allows radio transmission to a series of frequencies, features abilities to function at low power and to reject random interferences

parabolic antenna characteristics

antenna uses a dish to capture extra signals and focus them onto an antenna, increases the effective area which produces very high signal gain

WIMAX characteristics

based on 802.16 standard, designed to support wireless broadband services, uses similar cell structure to cell phone system

IEEE 802.11 uses what for collision management

collision avoidance technology

give examples of where wireless interference can come from

cordless phones, aircraft, digital equipment, microwaves ovens, other wireless networks

omni directional antenna characteristics

design transmits its signal equally in all directions, most perfected design of this antenna => "theoretical isotropic antenna"

two categories of antennas

directional or omni directional

what happens when frequency is avoided

flow of data drops down to a slower rate

what happens when frequency is clear

flow of data shifts up to higher rate

if frequency repeatedly unavailable then?

frequency is avoided

directional antenna characteristics

has gain in a single direction - example: parabolic dish used for satellite reception and the Yagi Design

infrastructure arrangement allows for what

higher power external antennas which can extend the range of a network

WiFi protected access (WPA)

improvement over WEP, uses improved protocol and algorithm to improve security of keys, changes key processing and rotates keys more often, also adds function to prevent packet forgeries

what is spatial multiplexing

improvement over beamforming, transmitter receiver each have multiple antennas, ea. antenna has own radio, benefit => improvement in throughputs and mobility of clients

in the case of tuned antenna what is effective area?

inversely proportional to the frequency of operation, meaning: 2.4Ghz unit will have 2x range of a 5.2Ghz unit of same power

accidental access

is gained by a user unknowingly accessing an unsecured wireless system

deliberate access

is willful accessing of either an unsecured or secured system by an unauthorized user; is ILLEGAL

what is major advantage of spread spectrum

multiple devices can use the same frequency at the same time without interference simply by varying the frequency shift times

gain antenna characteristics

omni directional antenna that has equal gain in all horizontal directions

ad hoc mode is?

one device acts as a temporary controller to control the sequence of transmissions as part of the collision avoidance design

infrastructure arrangement is?

one machines acts as a access point server and controls the Wireless Access Point(WAP)

indoor point-to-multipoint

one or more access points for indoor use -- (WirelessLANConfigs)

what is modulation

process of adding a data stream to an operating frequency

transmit beamforming requirements

receiver has a single antenna and there are few obstructions preventing line of sight transmission, minimum radio-reflective surfaces, both transmitter receiver have fixed positions

what does beamforming rely on and outcome

relies on feedback from the receiver regarding the quality of the received signal; allows transmitter to tune itself to the receiver (feedback not avail. non-802.11N devices)

Wireless is a very cost effective, portable method of installing a .... network

residential network

a wireless network uses what type of modulation

spread spectrum modulation

802.11 N characteristics

supports upto 300Mbps, 802.11N requires interoperability

what is spread spectrum modulation

the carrier frequency moves between specific frequencies within the band, data can be easily encoded

wireless attenuation is caused by?

the inability of radio signals used with wireless technology to penetrate materials; greater the difficulty in penetration, the greater the attenuation

what does it mean when wireless networks have no exclusive claim to their bandwidth

they are both low power and unlicensed

why does a spread spectrum receiver have to be synchronized with the transmitter?

to match the frequency changing pattern

802.11 G characteristics

upto 54Mbps, backward compatible with 802.11 B, B+G can work on the same network up to max speed of each device; proprietary protocols

outdoor point-to-multipoint

used to connect wired LANs in several buildings within a 8-10km radius

how does MIMO work

uses multiple antennas in an access point to transmit a signal, signal sent out by each antenna is vastly improved over other 802.11 versions

what is multipath interference

when wireless signals are reflected off a large metal surface causing related signals to be out of phase with each other

if there is noise on particular frequency what does spread spectrum do

will rely on encoding structure to recover the data

WEP & what is it

wired equivalency privacy (WEP) - the wireless router and authorized NICs shared a common encryption key when data is transmitted; minimum level of security

MAC address filtering?

wireless router is programmed to acknowledge contact only from NICs with specific MAC addresses

WiMAX stands for?

worldwide interoperability for microwave access