Everyone who has built, bought or at least tuned a radio receiver has probably heard such words as: sensitivity and selectivity. Sensitivity is a measure of how well your receiver can receive a signal even in the most distant areas.
And selectivity, in turn, shows how well the receiver can tune to a particular frequency without being affected by other frequencies. These “other frequencies”, i.e. those not related to the transmission of the signal from the selected radio station, in this case play the role of radio interference.
By increasing the transmitter power, we force receivers with low sensitivity to receive our signal by all means. Also important is the mutual influence of signals from different radio stations on each other, which complicates tuning, reducing the quality of radio communication.
The Wi-Fi environment uses the radio air as the medium for data transmission. So many of the things that radio engineers and radio amateurs of the past and even the century before are still relevant today. But some things have changed. The analog format has been replaced by digital broadcasting, which has led to a change in the nature of the transmitted signal.
Radio traffic load
The effect of congestion can be seen firsthand, at the time of selecting a device to connect. If the list of selected Wi-Fi networks contains more than three or four items, we can already talk about overloading the radio air. At the same time, each network is a source of interference for its neighbors. And interference affects the performance of the network, because it dramatically increases the noise level and it leads to the need to constantly resend packets. In this case, the main recommendation is to lower the transmitter power in the access point and ideally to get all the neighbors to do the same so as not to interfere with each other.
The situation resembles a school class, when the teacher is away. Each student starts talking to his or her roommate and other classmates. In the general noise, they can’t hear each other very well and start talking louder, then even louder, and finally they start shouting. The teacher quickly rushes to the classroom, takes some disciplinary measures and the normal situation is restored. If we think of the teacher as a network administrator and the students as an access point owner, we get an almost direct analogy.
Asymmetric connection
As mentioned earlier, the transmitter power of the access point is usually 2-3 times stronger than the client mobile devices: tablets, smartphones, laptops, and so on. Therefore it is very likely the emergence of “gray areas”, where the client will receive from the access point a good stable signal, but the transfer from the client to the point will work “not very”. This connection is called asymmetric.
To maintain a stable connection with good quality it is highly desirable that between the client device and the access point was a symmetrical connection where the reception and transmission in both directions work effectively. To avoid asymmetric connections, it is a good idea to avoid unreasonable increases in transmitter power.
When a power boost is required
The factors listed below require you to turn up the power to maintain a stable connection.
Interference from other types of radio devices and other electronics
Bluetooth devices such as headphones, wireless keyboards and mice operating in the 2.4 GHz frequency band may interfere with the access point and other Wi-Fi devices.
The devices listed below can also have a negative impact on signal quality:
– microwave microwave ovens;
– baby monitors;
– CRT monitors, wireless speakers, cordless phones, and other wireless devices;
– External sources of electrical voltage, such as power lines and power substations,
– electric motors;
– Cables with insufficient shielding, and coaxial cable and connectors used with some types of satellite dishes.
Long distances between Wi-Fi devices
All radio devices have a limited range. In addition to the design features of the wireless device, the maximum range can be reduced by external factors such as obstacles, radio interference, and so on.
All this leads to the formation of local “out-of-reach zones” where the signal from the access point “doesn’t reach” the client device.
Obstacles in the signal path
Various obstacles (walls, ceilings, furniture, metal doors, etc.) located between Wi-Fi devices can reflect or absorb radio signals, which leads to a deterioration or complete loss of communication.
Simple and straightforward things like reinforced concrete walls, sheet metal covering, steel frame, and even mirrors and tinted glass noticeably reduce signal intensity.
Secure wireless network edge
Neighboring access points in a parallel network not only create interference, but can also be used as a launching pad for an attack on the network.
In turn, the wireless network controller must combat this. In the arsenal of controllers NXC2500 and NXC5500 enough tools, such as standard authentication WPA / WPA2-Enterprise, various implementations of Extensible Authentication Protocol (EAP), built-in firewall.
In this way, the controller not only finds unauthorized access points, but also blocks suspicious activities on the corporate network that are likely to be malicious.
Conclusion
The scope of this short article does not allow us to talk about all of the nuances. But even a cursory overview will tell you that designing and maintaining a wireless network has some rather interesting nuances. On the one hand, you need to combat the mutual influence of signal sources, including reducing the power of access points. On the other hand, it is necessary to maintain the signal level at a high enough level for stable communication. A way around this contradiction is to use the special features of the wireless network controllers.
