What is meaning of negative dbm in signal strength

Question

When we try to get nearby cells and their LAC  MNC  signal  and while using other android apps  we are getting signal as negative value  like -85dbm   How should I take this  Should I ignore  -ve sign and take absolute value or -85 is smaller strength than -60   How this will affect my location finding

User · Answer

At ms end Rx lev ranges 0 to -120 dbm Mean antenna power which received at ms end alway less than 1mW   Thats why it always -ve

User · Answer

I think it is confusing to think of it in terms of negative numbers  Since it is a logarithm think of the negative values the same way you think of powers of ten   10 3   1000 while 10 -3   0 001   With this in mind and using the formulas from S Lists s answer  and assuming our base power is 1mW in all these cases  we can build a little table    -------- -------------------    P dBm           P mW          -------- -------------------       50     100000                      40      10000                strong transmitter      30       1000                                  20        100                                10         10                                 0          1                 -10          0 1               -20          0 01              -30          0 001             -40          0 0001            -50          0 00001                         -60          0 000001                        -70          0 0000001                 v     -80          0 00000001       sensitive receiver     -90          0 000000001    -------- -------------------    When I think of it like this I find that it s easier to see that the more negative the dBm value then the farther to the right of the decimal the actual power value is    When it comes to mobile networks  it not so much that they aren t powerful enough  rather it is that they are more sensitive  When you see receivers specs with dBm far into the negative values  then what you are seeing is more sensitive equipment   Normally you would want your transmitter to be powerful  further in to the positives  and your receiver to be sensitive  further in to the negatives

User · Answer

The power in dBm is the 10 times the logarithm of the ratio of actual Power 1 milliWatt   dBm stands for  decibel milliwatts   It is a convenient way to measure power  The exact formula is   P dBm    10    log10  P W    1mW      where   P dBm    Power expressed in dBm    P W    the absolute power measured in Watts    mW   milliWatts    log10   log to base 10   From this formula  the power in dBm of 1 Watt is 30 dBm  Because the calculation is logarithmic  every increase of 3dBm is approximately equivalent to doubling the actual power of a signal   There is a conversion calculator and a comparison table here  There is also a comparison table on the Wikipedia english page  but the value it gives for mobile networks is a bit off   Your actual question was  does the - sign count    The answer is yes  it does   -85 dBm is less powerful  smaller  than -60 dBm  To understand this  you need to look at negative numbers  Alternatively  think about your bank account  If you owe the bank 85 dollars rands euros rupees  -85   you re poorer than if you only owe them 65  -65   i e  -85 is smaller than -65  Also  in temperature measurements  -85 is colder than -65 degrees   Signal strengths for mobile networks are always negative dBm values  because the transmitted network is not strong enough to give positive dBm values   How will this affect your location finding  I have no idea  because I don t know what technology you are using to estimate the location   The values you quoted correspond roughly to a 5 bar network in GSM  UMTS or LTE  so you shouldn t have be having any problems due to network strength

[android] What is meaning of negative dbm in signal strength?

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