Average dBm

avg_dbm.py

def average_dbm(dbms):
    # https://en.wikipedia.org/wiki/Decibel
    # https://en.wikipedia.org/wiki/LogSumExp

    # Less numerically stable version:
    #  10*numpy.log10(numpy.mean(numpy.power(10, (dbms-30)/10)))
    bel_np = 0.5 * numpy.log(10)  # Bel & Neper by definition
    dbel_np = bel_np / 10
    np_to_db = 1 / dbel_np

    # B = 1/2 * ln(10)
    # Lp = 1/2 * ln(P/P0) * Np
    sum_dbm = 1/2 * np_to_db * scipy.special.logsumexp(dbms / (1/2 * np_to_db))
    avg_dbm = sum_dbm - 10 * numpy.log10(len(dbms))  # linear division is log subtraction

    return avg_db