Cell phone signal Strength units db, dbm, and ASU

DB, dbm are the units of power gain, the difference is as follows:

The db is a value representing the relative value, the pure ratio, only represents the relative size relationship of two quantities, no unit, when considering a power compared to B power large or small number of DB, according to the following formula: 10log (a power/b power), if the two voltage ratio calculation, To use 20log (a voltage/b voltage).
[Example] a power greater than B power one times, then 10LG (a power/b power) =10lg2=3db. In other words, the power of A is 3 DB larger than that of B. Conversely, if the power of a is half the power of B, then the power of a is 3 DB smaller than the power of B.



dBm is a value that represents absolute power (or a ratio that is based on 1mW Power) and is calculated as: 10log (Power value/1MW).
[Example] if the power P is 1mw, converted to dbm after 0dBm.
[Example] for 40W power, the value after the conversion in dbm units should be: 10log (40W/1MW) =10log (40000) =10log4+10log10000=46dbm.
In summary, the DB is a ratio of two amounts, representing the relative size between two measurements, and dbm is a value that represents the absolute size of the power. In the DB,DBM calculation, note the basic concept, with one dbm minus the other dbm, the result is a db, such as: 30DBM–0DBM = 30dB.
The number displayed on the phone is in dBm (you can use ALT+NMLL to let the phone display the current receive signal value), the value is negative, and it is always negative, the greater the DBM value signal is better, that is, the phone will display such as -67 (dbm), that means the signal is strong. Here is also a little knowledge: China Mobile norms, mobile phone receiving level >= (city take -90dbm; village fetch -94DBM), then meet the coverage requirements, that is, the wireless signal strength here to meet the coverage requirements. -67DBM is better than the -90DBM signal more than 20 db, then it in the phone connection success rate and the voice quality of the call will be much better (of course, including Edge/gprs Internet speed).



ASU simply represents the rate at which the phone transmits its location to nearby towers. It measures the same thing as dbm, but it is expressed in a more linear way. You can use this formula to convert ASU into dbm:dbm=-113+ (2*asu)
For example: -69dbm ASU
-69DBM = 113 + (2*22)


In the past, we generally use the cell phone to determine the number of cell phone signal strength, but it is worth explaining that the mobile phone manufacturers in fact, the mobile phone signal strength and the number of grid conversion relationship does not have a unified standard, for example, Nokia's 4-cell signal may not be better than the iphone 4 5-cell signal poor. How should we judge the strength of the signal? A very important part of the recent MX2 evaluation of Wang's freedom is the contrast test of cell phone signal strength, so let's take a closer look at some of the things about cell phone signals!



In the Android phone settings, we can see the status information about the signal strength, which can be seen in dbm and ASU for signal strength. where dbm (1 MW of decibel) is a general indicator of the strength of a mobile phone signal, such as the iphone dial *3001#12345#* can enter the project mode, the upper left corner of the number is the signal strength, ASU (Alone signal unit Independent signal Unit) is a unique unit of signal that Google defines for Android phones, and the relationship between them is: DBm =-113+2*asu.



Cell phone signal Strength units db, dbm, and ASU