26
ECLYPSE APEX
Recommendations are provided regarding the radio signal obstructions and factors that should be
avoided to obtain the best Wi-Fi radio signal transmission and reception. Walls attenuate radio wave
propagation by an amount that varies with the construction materials used. See
for more information on wall materials that can reduce range transmission.
About the 2.4 GHz ISM Band
The 2.4 GHz ISM (Industrial, Scientific and Medical) band has been allocated worldwide for the use of
radio frequency energy by industrial, scientific, and medical purposes as part of the device’s method of
internal operation and as such may have powerful emissions that cause interference to radio commu-
nications.
For example, microwave ovens operate in the 2.4 GHz ISM band with about 1000W emitted power
and a fraction of a percent of that energy does leak from the oven. While this is not a health risk, Wi-Fi
networks operate at even lower power levels to communicate and can be overwhelmed by this source
of interference.
When setting up a 2.4 GHz band Wi-Fi network, you must take into consideration any equipment that
operates in the 2.4 GHz ISM band such as medical and laboratory equipment. Other sources of inter-
ference are other telecommunications equipment such as cell phones, GSM/DECT, cordless phones,
RFID reader, Bluetooth devices, walkie-talkies, baby monitors, and so on. Note that equipment that
transmits in other frequency bands do emit spurious emissions at low levels over a wide spectrum so
that a radio transmitter that is in close proximity to the ECLYPSE Wi-Fi adapter can cause interfer-
ence, even if its operating frequency is 1.9 GHz for example.
Frequency
P
o
w
e
r
(L
o
g
)
Transmitted
power
Center
Frequency
Occupied
Bandwidth
Spurious
Emission
Amplitude
Desired Signal Spurious Emissions
Figure 9: Typical Radio Transmitter Spurious Emissions
Distance Between the Wi-Fi Adapter and Sources of Interference
Unrelated transmitters should be more than 6.5 feet (2 m) away from the Wi-Fi Adapter to avoid possi-
ble interference.
About Wi-Fi Network Channel Numbers
Wi-Fi communications use a slice of radio spectrum or channel width for data transmission. In general
terms, the amount of channel width required is proportional to the data transmission rate. Wi-Fi net-
works operate in a number of different frequency ranges or bands such as the 2.4 GHz band. Each
band is divided into a number of industry-standard channels that represent a center frequency for data
transmission. In practice, the center frequency is the mid-point between the upper and lower cutoff fre-
quencies of the channel width.
When the channel width is larger than the channel spacing (the space between channels), overlap be-
tween the channels can occur, resulting in inter-channel interference that lowers overall network
throughput. This is shown in the diagram below. For example, in the 2.4 GHz band using 802.11g, the
channel width is 20 MHz while the channel spacing is 5 MHz. If one Wi-Fi network is using channel 1
that is in close proximity to another Wi-Fi network that is using channel 2, there will be significant inter-
channel overlap and interference. Data throughput is reduced as a result.
Connecting IP Devices to an IP Network
Содержание ECLYPSE APEX
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