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[link-quality] optimize RSS calculation (#5508)

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This commit is contained in:
Simon Lin
2020-09-10 12:22:32 -07:00
committed by GitHub
parent cf1057b780
commit c9004a6f3f
1 changed files with 4 additions and 23 deletions
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src/core/thread/link_quality.cpp
+4 -23
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@@ -68,7 +68,6 @@ otError RssAverager::Add(int8_t aRss)
{
otError error = OT_ERROR_NONE;
uint16_t newValue;
uint16_t oldAverage;
VerifyOrExit(aRss != OT_RADIO_RSSI_INVALID, error = OT_ERROR_INVALID_ARGS);
@@ -83,28 +82,10 @@ otError RssAverager::Add(int8_t aRss)
newValue = static_cast<uint16_t>(-aRss);
newValue <<= kPrecisionBitShift;
oldAverage = mAverage;
if (mCount == 0)
{
mCount++;
mAverage = newValue;
}
else if (mCount < (1 << kCoeffBitShift) - 1)
{
mCount++;
// Maintain arithmetic mean.
// newAverage = newValue * (1/mCount) + oldAverage * ((mCount -1)/mCount)
mAverage = static_cast<uint16_t>(((oldAverage * (mCount - 1)) + newValue) / mCount);
}
else
{
// Maintain exponentially weighted moving average using coefficient of (1/2^kCoeffBitShift).
// newAverage = + newValue * 1/2^j + oldAverage * (1 - 1/2^j), for j = kCoeffBitShift.
mAverage = static_cast<uint16_t>(((oldAverage << kCoeffBitShift) - oldAverage + newValue) >> kCoeffBitShift);
}
mCount += (mCount < (1 << kCoeffBitShift));
// Maintain arithmetic mean.
// newAverage = newValue * (1/mCount) + oldAverage * ((mCount -1)/mCount)
mAverage = static_cast<uint16_t>(((mAverage * (mCount - 1)) + newValue) / mCount);
exit:
return error;