cis 310 wireless

wireless spectrum

frequency range of electromagnetic waves used for data/voice communication

fixed spectrum

in a wireless spectrum some bands have only a single frequency 

low frequency

travels long distances, passes through many obstacles

high frequency

travels short distances, few obstacles, narrow bandwidth, noise effect decreases as transmitter power increases

broad examples of wireless media

radio, microwave, and infrared

infrared

collect data through various sensors, relies on line of sight

FHSS

Frequency hopping spread spectrum, a method of transmitting radio signals by rapidly changing carrier frequency among many distinct frequencies occupying a large spectral band 

DSSS

Direct sequence spread spectrum, data signal at the sending station is combined with a high data rate bit sequence, which divides user data based on spreading ratio

How antennas work

Wireless signals originate from electrical current traveling along a conduct→travels from the transmitter to an antenna→antenna emits the signal as a series of electromagnetic waves into the atmosphere→at the destination, another antenna accepts the signal and a receiver converts it back to current

Unidirectional(directional antenna)

wireless signal single direction,signal farther with a limited coverage area

types of directional antenna

yogi, parabolic, grid, patch and panel antennas

omnidirectional antenna

wireless signal all direction,360 donut

types of omni directional antenna 

rubber duck antenna, omni antennas, antenna arrays 

rubber duck antennas

often found on access points and routers

omni antennas

found outdoors

antenna arrays

used on cellular towers

propagation

the way in which a wave travels from one point to another

LOS (line of sight)

signal travels in straight line directly from transmitter to receiver 

fading 

as signal runs into obstacles, its energy will gradually fade 

attenuation

signal weaken moving away from transmission antenna

interference

wireless signals are more vulnerable to noise

refraction

as a wave travel through object the wave’s direction, speed, and wavelength are altered (or refracted)

reflection

signal bounces back toward its source

scattering

diffusion in multiple different directions

diffraction

signal splits into secondary waves

multipath signals

wireless signals follow different paths to destination

MIMO 

multiple input multiple output, multiple access point and client device antennas may issue signal to one or more receivers

MU-MIMO

newer technology that allows multiple antennas to service multiple clients simultaneously

POE

technology that allows electrical power and data to be transmitted over cat5 ethernet cabling, can power network devices like access points, IP cameras, and VoIP phones without separate power cords 

SSID

service set identifier, unique character string identifying access points, name networks broadcasting, being sent out through beacon EX: NSUnwired 2.4 and 5 

5GHZ

stronger but goes shorter distance

2.4GHZ

weaker but goes farther distance

wifi network security

802.11 standard security, none by default, SSID only item required

authentication

process of comparing and matching a client’s credentials with the credentials in a database 

mac filtering 

prevents the AP from authenticating any device whose MAC address is not listed 

encryption 

use of an algorithm to scramble data 

WEP(1997)

designed to secure wireless networks using encryption and access restriction 

WPA (2003)

uses the temporal key integrity protocol encryption to improve key management and integrity checks

WPA2(2004)

include better administration and lower vulnerability to assaults 

WPA3(2018)

offers enhanced encryption, improved protection against dictionary brute force attacks, and simplified device configuration