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Wifi Inteference

Created: Oct 27, 2021 01:54:07Latest reply: Oct 27, 2021 08:57:48 334 5 10 0 0
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Dear All,

 

I would like to understand about WiFi interference, what is the root cause of interference and how it impact to subscriber? In case we use 3 devices with the same model -same frequency, put near each other, how is the possibility of interference?


Thanks.


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jason_hu
Admin Created Oct 27, 2021 02:00:56

Hi friend!

Two frequency bands are available on WLANs: 2.4 GHz and 5 GHz.


The 2.4 GHz frequency band is the Industrial, Scientific, and Medical (ISM) open frequency band. Interference sources in the 2.4 GHz frequency band include cordless phones, baby monitors, microwave ovens, wireless cameras, bluetooth devices, infrared sensors, and fluorescent light ballasts.


Compared with 2.4 GHz frequency band, 5 GHz frequency band has fewer interference sources and more devices begin to use the 5 GHz frequency band, such as cordless phones, radars, wireless sensors, and digital satellites.


In most cases, microwave ovens work at the frequency band ranging from 2.4 to 2.5 GHz, which overlaps the 2.4 GHz frequency band used by WLAN devices. In addition, the power of microwave ovens ranges between 800 W and 2000 W, which is much higher than the transmit power of APs and STAs. Even if interference shielding is performed, microwave ovens still have severe interference on WLAN devices. Microwave ovens greatly reduce the throughput of WLAN devices if they are within a distance shorter than 8 meters around WLAN devices.


The power of cordless phones is about 3 W, which is higher than the AP's transmit power. According to the test analysis on the interference caused by cordless phones on WLAN devices, when the distance between cordless phones and APs (or STAs) is within 1 meter, interference increases significantly. When the distance is shorter than 0.5 meter, WLAN devices are even offline and the cordless phone voice is not clear. Therefore, you are advised to deploy cordless phones more than 2 meters away from APs or STAs.


The transmit power of wireless cameras ranges from 500 mW to 1000 mW. In indoor scenarios, wireless cameras may affect the WLAN network but have lighter interference than microwave ovens and cordless phones. Therefore, you are advised to deploy wireless cameras far away from WLAN devices during WLAN planning.


Bluetooth devices use the frequency hopping spread spectrum (FHSS) technology and 1 MHz channel bandwidth. If a bluetooth device is sending data at the frequency band overlapping with a WLAN channel that is being monitored by a WLAN device, the WLAN device selects a random backoff period. During this period, the bluetooth device changes to work at a non-overlapping channel, allowing the WLAN device to send data. Therefore, bluetooth devices have small interference on WLAN devices. This interference can be ignored during WLAN planning.


This can happen when a signal is using the same channel. Co-channel interference may also result when access points are placed too close together and are configured with too high of output power. In this situation, the configured Wi-Fi network can actually interfere with itself.  strengths. So don’t put the equipment too close.

Hope to help you!

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user_4397771
user_4397771 Created Oct 31, 2021 04:08:30 (0) (0)
Good thank  
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Hello,
We're working on your problem. Please be patient.
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Hi user_4397771,
bro, Wireless interference is real. If we have a large number of wireless devices in the same environment, there will be channel interference, which will reduce our signal strength and our wireless experience. Therefore, a recommended distance is involved in wireless planning. For example, the safe distance between two APs is 2 m.
If your XUAN doesn't have secure APs or haven't planned channels, my advice is not to get too close. This will degrade the wireless quality.
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Hi friend!

Two frequency bands are available on WLANs: 2.4 GHz and 5 GHz.


The 2.4 GHz frequency band is the Industrial, Scientific, and Medical (ISM) open frequency band. Interference sources in the 2.4 GHz frequency band include cordless phones, baby monitors, microwave ovens, wireless cameras, bluetooth devices, infrared sensors, and fluorescent light ballasts.


Compared with 2.4 GHz frequency band, 5 GHz frequency band has fewer interference sources and more devices begin to use the 5 GHz frequency band, such as cordless phones, radars, wireless sensors, and digital satellites.


In most cases, microwave ovens work at the frequency band ranging from 2.4 to 2.5 GHz, which overlaps the 2.4 GHz frequency band used by WLAN devices. In addition, the power of microwave ovens ranges between 800 W and 2000 W, which is much higher than the transmit power of APs and STAs. Even if interference shielding is performed, microwave ovens still have severe interference on WLAN devices. Microwave ovens greatly reduce the throughput of WLAN devices if they are within a distance shorter than 8 meters around WLAN devices.


The power of cordless phones is about 3 W, which is higher than the AP's transmit power. According to the test analysis on the interference caused by cordless phones on WLAN devices, when the distance between cordless phones and APs (or STAs) is within 1 meter, interference increases significantly. When the distance is shorter than 0.5 meter, WLAN devices are even offline and the cordless phone voice is not clear. Therefore, you are advised to deploy cordless phones more than 2 meters away from APs or STAs.


The transmit power of wireless cameras ranges from 500 mW to 1000 mW. In indoor scenarios, wireless cameras may affect the WLAN network but have lighter interference than microwave ovens and cordless phones. Therefore, you are advised to deploy wireless cameras far away from WLAN devices during WLAN planning.


Bluetooth devices use the frequency hopping spread spectrum (FHSS) technology and 1 MHz channel bandwidth. If a bluetooth device is sending data at the frequency band overlapping with a WLAN channel that is being monitored by a WLAN device, the WLAN device selects a random backoff period. During this period, the bluetooth device changes to work at a non-overlapping channel, allowing the WLAN device to send data. Therefore, bluetooth devices have small interference on WLAN devices. This interference can be ignored during WLAN planning.


This can happen when a signal is using the same channel. Co-channel interference may also result when access points are placed too close together and are configured with too high of output power. In this situation, the configured Wi-Fi network can actually interfere with itself.  strengths. So don’t put the equipment too close.

Hope to help you!

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user_4397771
user_4397771 Created Oct 31, 2021 04:08:30 (0) (0)
Good thank  
Posted by jason_hu at 2021-10-27 02:00 Hi friend!Two frequency bands are available on WLANs: 2.4 GHz and 5 GHz.The 2.4 GHz frequency band i ...
Great! thanks you very much
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