Deck 1 Flashcards
802.11ac Wave 1
Channel Width 80 MHz
Spacial streams 3
no Mu-MIMO
Data Speed 1.3 Gbps
802.11ac Wave 2
Channel Width 160 MHz
4 Spacial Streams
Has Mu-MIMO
Data Speed 2.6 Gbps
802.11ac Wave 3
Channel Width 160 MHz
8 Spacial Streams
Has Mu-MIMO
Data Speed 4.5 Gbps
Effective Isotropic Radiated Power (EIRP)
The actual power radiated from and antenna connected to a transmitter.
dBm
The power ratio of decibels (dB) of measured power referenced to one Milliwatt (mW)
Wavelength
The length of a single cycle of a wave, as distance measured between one peak or trough of a wave and the next.
5 gHz frequency bands
- 150 - 5.250
- 250 - 5.350
- 470 - 5.725
- 725 - 5.825
2.4 gHz frequency band
2.400 - 2.4835
14 channels
Amplitude
Amount of energy of the wave; size of the wave
Frequency
How often you see a wave over one second; cycles per second
Co-channel interferrence
interference caused by two more transmitters using the same channel. signals overlapping with each other. Only a problem if two networks transmit at the same time. Common on 2.4 GHz on channels 1, 6, &11. To solve move one of them to a different channel. Can be used if 19 dBm difference between receiving deceiving devices because they can tell signals apart.
neighboring channel interference
two different networks overlapping with each other and transmitting at the same time. can cause data corruption. common on 2.4 gHz. Acceptable if large difference in signal strength.
Non 802.11 interference
other devices out there have the ability to use 2.4 gHz w/o using 802.11 standards. Example: microwave oven, cordless phones, baby monitors.
Free Space path loss
As a signal expands in one direction, it will decrease in strength. Higher the frequency and greater the distance = more loss.
Dynamic Rate Shifting (DRS)
The dynamic changing of modulation method by 802.11 devices based on current received signal strength (RSSI) and signal to noise ration (SNR) conditions. Device automatically adjusts modulation as you get farther away . To fix this you must increase transmitters in clusters
Reflection
causes the wave to bounce off in a different direction. Use MIMO to solve. Receiver will receive multiple copies of the transmission and combines.
Absorption
Concrete and other walls/materials absorb the signal
Scattering
Caused by rough materials. when going through concrete walls for example the waves bounce of when coming out and go in different directions.
Refraction
coming out in another direction, bending
Diffraction
signals bend around
Fresnel Zone
Problems with Point to Point; when objects get into the Fresnel zone, they can have an affect on the waves to arrive out of phase. Need to keep Fresnel zone clear. curvature of the earth can cause a problem about 2 miles away, or mountains as transmitters cannot see each other anymore.
Hertz
Measure of frequency or cycles per second
Band
a range of continuous frequencies.multiple frequencies that are continuous and can be grouped together for the same purpose, such as wireless Networks or Radio-stations.
channels
Each band is divided into what’s called distinct channels. Each channel is usually given a specific channel-number and is also assigned to a specific Frequency within the Band
Gain
the measure of how effectively an antenna can focus radio waves in a certain direction. greater the gain = more directional. 0 dBi means no direction. it is a sphere. emitting in all directions
4 dBi= omidirectional
12 dBi very directional s
Polarization
The orientation of the electrical fields wave in comparison to the horizon.
Basic Service Set (BSS)
Single access point operating in infrastructure mode, offering 802.11 services
WLAN
wireless local area network (home, office)
WMAN
Wireless-metropolitan area network
WMAN
Wireless-metropolitan area network large business
WWAN
wireless wide area network (country, global)
Infrastructure Mode
mode used by an access point to offer wireless services to form wireless infrastructure
Basic Service Area (BSA)
The bounded usable area of RF waves emitted from an access point. the outer range
BSS Identifier (BSSID)
Unique identifier based on MAC address of an access point.
Service Set Identifier (SSID)
The logical name of a wireless network defined as a text string Example: chosen name of network “Netgear62”
Distribution system
The upstream wired connection from and access point to an existing network
Extended Service Set (ESS)
Multiple access points operating in infrastructure mode, offering same SSID
Independent Basic Service Set (IBSS)
Network created ad-hoc between two wireless clients, no connection to any existing wireless networks
Repeater
Access point w/o a wired up-link and configured to repeat received RF waves. Used for extending WLAN to areas unreachable by wired links
wireless mesh
repeaters repeaters repeaters
