Mastering Wireless Network Administration

An isotropic radiator is a point source that radiates signal equally in all directions.

Electric and Magnetic fields are perpendicular to one another, moving into space away from the source.

Antennas convert electrical current into RF waves.

The electrical current is carried by a conductive RF cable.

The distance from the strongest point to the half power points, measured in degrees

dBi measures gain relative to an isotropic radiator, while dBd measures gain relative to a half-wave dipole

Radiation patterns of a particular model of antenna

Omnidirectional

The gain of the new antenna must be the same or lower, and the new antenna must be of the same type with similar characteristics.

1.1:1 to 1.5:1

To detect incoming over-voltages induced by nearby lightning strikes and shunt the current to earth ground.

The use of non-certified equipment with an intentional radiator must follow specific guidelines.

Parabolic Dish and Grid antennas

Static beamforming

Libraries and warehouses with long aisles of shelves

The orientation of the RF waves

$72.2 \times \left[ \frac{N \times d1 \times d2}{F \times D} \right]$

$H = \frac{D^2}{8}$

Minimize the negative effects of multipath by using multiple antennas and receivers functioning together

50 ohms

True

False

False

True

False

True

True

True

True

True

False

False

False

True

False

False

True

True

False

False

directions

source

waves

cable

sun

logarithmic

Beamwidth is the measurement of how broad or narrow the focus of an antenna is— and is measured both horizontally and vertically.

signal

Parabolic Dish and Grid

Static

high density

libraries and warehouses

switched

installation

less

H = \frac{D^2}{8}

VSWR

Voltage standing wave ratio (VSWR)

50, 75

Lightning Arrestors

VSWR = Measurement of impedance mismatch in an RF communications system Lightning Arrestors = Detect incoming over-voltages induced by nearby lightning strikes and shunt the current to earth ground FCC Certified System = Regulators require wireless systems to be authorized as a system and allow use of non-certified equipment with specific guidelines Antenna Diversity = Minimizes negative effects of multipath by using multiple antennas and receivers functioning together

dBi = Decibels relative to an isotropic radiator dBd = Decibels relative to a half-wave dipole Azimuth = Top-down view represented in an azimuth chart Elevation = Side view represented in an elevation chart

Omnidirectional = Radiates in all directions, providing general coverage Semidirectional = Provides wide directional focus Highly directional = Offers narrow directional focus Dipole antenna = Typical coverage pattern is bagel-shaped

Beamwidth = Measurement of how broad or narrow the focus of an antenna is Polar charts = Also known as radiation patterns, created in controlled environments Antenna diversity = Utilized to minimize the negative effects of multipath VSWR = Ratio measurement of an impedance mismatch in RF communications systems

Logarithmic scale = Used in azimuth and elevation charts, representing signal strength Half-wave dipole antenna = Equivalency of 0 dBd to 2.14 dBi Radiation patterns = Represent the signal pattern radiated by a particular model of antenna Outer ring of azimuth or elevation chart = Usually represents the strongest signal strength

Isotropic Radiator = A point source that radiates signal equally in all directions Electric Field = Perpendicular to the magnetic field, moving into space away from the source Antenna Diversity = Minimizes the negative effects of multipath by using multiple antennas and receivers together VSWR = Measurement of the change in impedances to an AC signal

Azimuth and Elevation Charts = Represent the radiation pattern of an antenna in the horizontal and vertical planes Earth Bulge = Factor to consider when determining the Fresnel zone radius for wireless links greater than 7 miles Antenna Accessories = Essential for proper antenna connection and installation, including cables, connectors, and lightning arrestors Beamwidth = Measurement from the center of the antenna signal to each of the points along the horizontal and vertical axes, where the signal decreases by half power (-3 dB)

RF Cable = Carries the electrical current for antenna radios and introduces signal loss into a communications link Antenna Arrays = Perform beamforming, concentrating RF energy using static, dynamic, and transmit beamforming Lightning Arrestors = Protect against over-voltages induced by nearby lightning strikes and shunt the current to earth ground Antenna Polarization = Refers to the orientation of the electric field in relation to the Earth's surface

True = Dynamic beamforming involves utilizing adaptive antenna arrays to provide a fixed radiation pattern False = FCC allows the use of third-party antennas with no restrictions

Static = Provides a fixed radiation pattern, also known as sectorized array Dynamic = Focuses RF energy in a specific direction and shape, utilizing adaptive antenna arrays Transmit = Involves transmitting phase-shifted signals to arrive in-phase at the receiver's location Beamforming = Concentrating RF energy with three types: Static, Dynamic, and Transmit

Semidirectional antennas = Used for short to medium distance communications Highly directional antennas = Used for strictly point-to-point communications Sector antennas = Provide high-gain, semidirectional coverage with a pie-shaped pattern and narrow vertical beamwidth MIMO patch antennas = Used in environments like libraries and warehouses with long aisles of shelves

Yagi antennas = Used for building-to-building WLAN communications Grid antennas = Used for strictly point-to-point communications Parabolic Dish antennas = Provide high-gain, semidirectional coverage with a pie-shaped pattern and narrow vertical beamwidth Sector antennas = Provide high-gain, semidirectional coverage with a pie-shaped pattern and narrow vertical beamwidth

Visual Line of Sight (LOS) = The perceived straight line that light travels along, with no bearing on successful RF transmission Antenna polarization = Refers to the orientation of the RF waves, which should match between transmitting and receiving antennas Isotropic radiator = Radiates signal equally in all directions, similar to the sun Beamwidth = The measurement of the change in impedances to an AC signal

Switched diversity = Legacy APs use this method to choose the signal with the best amplitude and ignore others MIMO = A more sophisticated form used by 802.11n and 802.11ac radios, enhancing reliability, range, and throughput Antenna diversity = Exists when a wireless device has two antennas and receivers functioning together to minimize the negative effects of multipath Dynamic beamforming = Involves utilizing adaptive antenna arrays to provide a fixed radiation pattern

VSWR = A ratio measurement of an impedance mismatch, with typical values ranging from 1.1:1 to as much as 1.5:1 Impedance = Must match when connecting RF equipment such as access point connectors, cabling, connectors, and antennas Signal loss = Introduced into a communications link, with the higher grade of cable resulting in less loss Antenna accessories = Essential for proper installation, including cables, connectors, splitters, amplifiers, attenuators, lightning arrestors, grounding rods, and wires

Fresnel zone = The area around the point source where the waves are in phase with the signal, and the radius is calculated using the formula $72.2 imes \left[\frac{(N \times d1 \times d2)}{(F \times D)}\right]$ Earth curvature = Must be considered if the link is greater than 7 miles, with the formula for the height of the earth bulge being $H = \frac{D^2}{8}$ in feet Antenna connection = Considers VSWR, signal loss, mounting, orientation, alignment, safety, and maintenance Antenna polarization = Refers to the orientation of the electric field in the radiated RF signal, affecting signal propagation and multipath

Omnidirectional = Radiates RF in a bagel-shaped pattern and is typically used for point-to-multipoint networks Semidirectional = Suitable for medium-distance communications, offering a compromise between highly directional and omnidirectional antennas Highly directional = Used for strictly point-to-point communications and includes parabolic antennas Isotropic radiator = Radiates signal equally in all directions, similar to the sun, and is a theoretical reference point for antenna measurements