android手机 - 关于信号强度的问题

信号强度：

信号通常以dBm作为度量单位，dBm是每毫瓦特的电磁波产生的功率。

-60dBm接近完美，-112dBm很容易掉线，-87dBm以上安卓手机会显示满格的信号强度。

从android5.0分析：

信号强度与手机信号格数的转化：

CellSignalStrengthGsm.java

private static final int GSM_SIGNAL_STRENGTH_GREAT = 12;
    private static final int GSM_SIGNAL_STRENGTH_GOOD = 8;
    private static final int GSM_SIGNAL_STRENGTH_MODERATE = 5;

@Override
    public int getLevel() {
        int level;
        // ASU ranges from 0 to 31 - TS 27.007 Sec 8.5
        // asu = 0 (-113dB or less) is very weak
        // signal, its better to show 0 bars to the user in such cases.
        // asu = 99 is a special case, where the signal strength is unknown.
        int asu = mSignalStrength;
        if (asu <= 2 || asu == 99) level = SIGNAL_STRENGTH_NONE_OR_UNKNOWN;        //无信号或无法识别
        else if (asu >= GSM_SIGNAL_STRENGTH_GREAT) level = SIGNAL_STRENGTH_GREAT;
        else if (asu >= GSM_SIGNAL_STRENGTH_GOOD)  level = SIGNAL_STRENGTH_GOOD;
        else if (asu >= GSM_SIGNAL_STRENGTH_MODERATE)  level = SIGNAL_STRENGTH_MODERATE;
        else level = SIGNAL_STRENGTH_POOR;
        if (DBG) log("getLevel=" + level);
        return level;
    }

注：asu与dBm的转化关系

        dBm = -113 + （2 * asu）