Measurement Report is triggered by whether the measured value crosses (goes higher or goes lower) a certain target value. The target value can be set by one of two methods. One is to use threshold which is a kind of absolute value and the other one is to use Offsef value which is a kind relative value with a reference to 'something' like serving cell value. However, in reality the measured value can fluctuate pretty frequently sometimes by measurement error by UE modem and sometimes by the fluctuation of Radio channel itself. In most case, the network would not be interested in such a small fluctuation and does not want to get too many measurement reports triggered by such a small fluctuation. To prevent this kind of unnecessarily frequent measurement report caused by small range of fluctuation, the parameter called 'Hysterisis' is introduced.
The hysteresis can be configured with a value between 0 and 30 dB.