SNR margin is simply calculating the difference between signal ( RSSI) and noise to get the SNR margin as a positive number expressed in db. Many DSL modems and wireless devices (notably dd-wrt open source router firmware) use SNR margin, only denoted as " SNR". SNR margin is often confused and used interchangeably with SNR. noise margin) is the ratio by which the signal exceeds the minimum acceptable amount (minimum SNR) to sustain a certain speed. Signal-to-noise ratio ( SNR) is defined as the power ratio between a signal (meaningful information) and the background noise (unwanted signal): SNR = signal / noise The more commonly used SNR margin, as described below is sometimes abbreviated as simply SNR as well. Typical environments range between -100dBm and -80dBm. The closer this value is to -120, the better, because that means there is little to no interference. This value is measured in decibels from zero to -120. Noise (dBm) in wireless communications is a combination of all unwanted interfering signal sources, such as crosstalk, radio frequency interference, distortion, etc. EIRP = Tx power (dBm) + antenna gain (dBi) - cable loss (dB). EIRP (Effective Isotropic Radiated Power) is the actual amount of signal leaving the antenna, measured in dB. Cisco can use range between 0 to -100, Atheros may use 0 to -127. Notes: RSSI values can be different depending on the chip vendor. Anything below -85dBm is generally unusable, and over -50dBm can be considered perfect. For wireless data communications, normal range is -45dBm to -87dBm.
Smaller negative numbers represent a cleaner/stronger signal. RSSI) is the usable strength of the radio waves, expressed in decibels relative to a milliwatt between 0dBm (strongest) and -120dBm (weakest).
0 kommentar(er)
