Noise in wireless communication systems is any unwanted fluctuation, instability or disruption that induces itself within the transmitted data signal via different mediums and interfering objects. This abrupt fluctuation is also a basic characteristic of data signals, which are modulated electromagnetic waves that travel through the air from electronic communication devices and circuits. Noise in wireless communication systems can be categorised into many types and has origins ranging from electronic devices to external environmental factors. Scientists and researchers have taken significant steps to quantify and remove noise from data signals in order to facilitate wireless communication.
Major noise sources in wireless communication systems include electronic circuit malfunctioning, temperature (including communication device temperature), disruption in the power supply of a communication device and frequency interference between wireless data signals. Note that all these sources of noise lie within necessary elements that support the process of communication and for this reason, avoiding induction of noise within a transmitted signal is almost impossible.
Noise can be categorised into five major types: thermal noise, shot noise, 1/f noise, burst noise and avalanche noise. Thermal, or white, noise is caused by the unexpected movement of electrons within circuits of thermally-affected electronic circuits; shot noise is caused by abrupt fluctuations in flow of current within devices or their wires; 1/f, or pink, noise is caused by impurities contained within the conducting material of communication devices; burst noise results from variation in the amplitude of transmitted signals; and avalanche noise is usually produced by the semiconductor diodes integrated within electronic communication devices in a wireless network.
Noise is a measurable variation that can be calculated within a wireless data signal as a ratio. The most common calculation method is called SNR (signal-to-noise ratio); it calculates the ratio of noise and data within an electromagnetic signal and is formulated as SP/NP, where SP is signal power and NP is noise power, both measured in watts. Advanced techniques of noise measurement include SQNR (signal-to-quantisation-noise ratio), CNR (career-to-noise ratio), PSNR (peak-signal-to-noise ratio) and SNIR (signal-to-noise plus interference ratio).
Noise can never be completely eliminated from an electronic or electromagnetic signal in a wireless or wired communication system. However, it can be reduced to levels at which its impact on transmitted data signals is minimal. Such noise reduction procedures employ sophisticated electronic circuits that are usually integrated within data communication devices. In wireless networking applications like soft switches, programmable routers and repeaters, reduction of noise is carried out by employing additional programmed instructions, or algorithms, that perform the task of identifying, evaluating and reducing noise.
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