According to some embodiments, a method for determining the first base offset, in the Action 431, may comprise fitting the sawtooth waveform from the sequences of TDOAs. Thereby the sawtooth offset Δ, the base offset, the phase and frequency of the sawtooth can be obtained. For instance, the positioning node 120, 130 may run a curve fitting algorithm or a Fourier analysis on the sequences of TDOAs to fit the sawtooth waveform. An example of the curve fitting algorithm include a least squares. However it is well known to the skilled person that there are various conventional ways, not limited to curve fitting algorithm or a Fourier analysis, to fit the sawtooth waveform. The embodiments herein are not limited to any of them.

Action A441

In order to obtain a precise relative propagation time, the positioning node 120, 130 may further determine a first delay in response D1 associated with the first sequence of TDOAs.

The first delay in response is known to the positioning node 120, 130. As shown in FIG. 5B, the first delay in response D1 may be a number of clock periods that the network node 110B waits for transmitting the reference signal RS01 for acknowledging the receipt of the reference signal RS02.

Action A451

The positioning node 120, 130 determines, based on the first sequence of TDOAs, a first relative distance d_2u?d_1u, which is a difference between distances from the wireless device 120 to each network node 110A, 110B in the first pair.