Compare Wireless Networking Types Flashcards
Access Point
Device that provides a connection between wireless devices and can connect to wired networks, implementing an infrastructure mode WLAN.
Wireless technologies use radio waves as transmission media. Radio systems use transmission and reception antennas tuned to a specific frequency for the transfer of signals. Most wireless LANs (WLANs) are based on the IEEE 802.11 standards, better known by the brand name Wi-Fi.
Basic Service Set Identifier(BSSID)
MAC address of an access point supporting a basic service area.
Frequency band
Portion of the microwave radio-frequency spectrum in which wireless products operate, such as 2.4 GHz band or 5 GHz band.
2.4 GHz
The 2.4 GHz standard is better at propagating through solid surfaces, giving it the longest signal range. However, the 2.4 GHz band does not support a high number of individual channels and is often congested, with both other Wi-Fi networks and other types of wireless technology, such as Bluetooth®. Also, microwave ovens work at frequencies in the 2.4 GHz band. Consequently, with the 2.4 GHz band, there is increased risk of interference, and the maximum achievable data rates are typically lower than with 5 GHz. The nominal indoor range for Wi-Fi is 45 m (150 feet) over 2.4 GHz.
5 GHz
The 5 GHz standard is less effective at penetrating solid surfaces and so does not support the maximum ranges achieved with 2.4 GHz standards, but the band supports more individual channels and suffers less from congestion and interference, meaning it supports higher data rates at shorter ranges. The nominal(under perfect circumstances) indoor range for 5 GHz wifi is 30 m (100 feet).
channels
Subdivision of frequency bands used by Wi-Fi products into smaller channels to allow multiple networks to operate at the same location without interfering with one another.
IEEE 802.11a
The IEEE 802.11a standard uses the 5 GHz frequency band only. The data encoding method allows a maximum data rate of 54 Mbps. The 5 GHz band is subdivided into 23 non-overlapping channels, each of which is 20 MHz wide.
Devices operating in the 5 GHz band must implement dynamic frequency selection (DFS) to prevent Wi-Fi signals from interfering with nearby radar and satellite installations.
IEEE 802.11b
The IEEE 802.11b standard uses the 2.4 GHz frequency band. Support a nominal data rate of just 11 Mbps.
The 2.4 GHz band is subdivided into up to 14 channels, spaced at 5 MHz intervals from 2,412 MHz up to 2,484 MHz.
Interference is a real possibility unless widely spaced channels are chosen (1, 6, and 11, for instance).
IEEE 802.11g
uses the same encoding mechanism and 54 Mbps rate as 802.11a but in the 2.4 GHz band used by 802.11b.
This made it straightforward for vendors to design 802.11g devices that could offer backwards support for legacy 802.11b clients.
IEEE 802.11n
It can work over both 2.4 GHz and 5 GHz. Each band is implemented by a separate radio. An access point or adapter that can support simultaneous 2.4 GHz and 5 GHz operation is referred to as “dual band.”
The 802.11n standard allows two adjacent 20 MHz channels to be combined into a single 40 MHz channel, referred to as “channel bonding.”
Channel bonding is a practical option only in the 5 GHz band.
802.11n increases reliability and bandwidth by multiplexing signal streams from 2–3 separate antennas. This technology is referred to as “ multiple input multiple output” (MIMO). The antenna configuration is represented as 1x1, 2x2, or 3x3 to indicate the number of transmit and receive antennas available to the radio.
The nominal data rate for 802.11n is 72 Mbps per stream or 150 Mbps per stream for a 40 MHz bonded channel.
In recent years, Wi-Fi standards have been renamed with simpler digit numbers; 802.11n is now officially designated as Wi-Fi 4.
Wi-Fi 5
Wi-Fi 5 is designed to work only in the 5 GHz band. A dual band access point can use its 2.4 GHz radio to support clients on legacy standards (802.11g/n). A tri band access point has one 2.4 GHz radio and two 5 GHz radios. Wi-Fi 5 allows up to eight streams, though in practice, most Wi-Fi 5 access points only support 4x4 streams. A single stream over an 80 MHz channel has a nominal rate of 433 Mbps.
Multiuser MIMO
In basic 802.11 operation modes, bandwidth is shared between all stations. An AP can communicate with only one station at a time; multiple station requests go into a queue.
In Wi-Fi 5, downlink MU-MIMO (DL MU-MIMO) allows the access point to use its multiple antennas to send data to up to four clients simultaneously.
Wi-Fi 6 (802.11ax)
Wi-Fi 6 improves the per-stream data rate over an 80 MHz channel to 600 Mbps.
Wi-Fi 6 works in both the 2.4 GHz and 5 GHz bands. The Wi-Fi 6e standard adds support for a new 6 GHz frequency band. 6 GHz has less range, but more frequency space, making it easier to use 80 and 160 MHz channels.
Where Wi-Fi 5 supports up to four simultaneous clients over 5 GHz only, Wi-Fi 6 can support up to eight clients, giving it better performance in congested areas. Wi-Fi 6 also adds support for uplink MU-MIMO, which allows MU-MIMO-capable clients to send data to the access point simultaneously.
Wi-Fi 6 introduces another technology to improve simultaneous connectivity called “ orthogonal frequency division multiple access” (OFDMA). OFDMA can work alongside MU-MIMO to improve client density—sustaining high data rates when more stations are connected to the same access point.
Wireless LAN Installation Considerations
Clients identify an infrastructure WLAN through the network name or service set identifier (SSID) configured on the access point.
If you use the same SSID, the access point and client device will use a probe to select the band with the strongest signal. If you configure separate names, the user can choose which network and band to use.
If there are multiple access points whose ranges overlap, they should be configured to use nonoverlapping channels to avoid interference.
You can configure wide channels (bonding) for more bandwidth, but this has the risk of increased interference if there are multiple nearby wireless networks.
Wi-Fi Analyzers
This type of software can be installed to a laptop or smartphone. It will record statistics for the AP that the client is currently associated with and detect any other access points in the vicinity.
Wireless signal strength is measured in decibel (dB) units. Signal strength is represented as the ratio of a measurement to 1 milliwatt (mW),Because 0 dBm is 1 mW, a negative value for dBm represents a fraction of a milliwatt.
When you are measuring signal strength, dBm values closer to zero represent better performance. A value around -65 dBm represents a good signal, while anything over -80 dBm is likely to suffer packet loss or be dropped.
The comparative strength of the data signal to the background noise is called the signal-to-noise ratio (SNR). Noise is also measured in dBm, but here values closer to zero are less welcome, as they represent higher noise levels. For example, if signal is ‑65 dBm and noise is ‑90 dBm, the SNR is the difference between the two values, expressed in dB (25 dB). If noise is -80 dBm, the SNR is 15 dB and the connection will be much, much worse.
