A networks node generates an inter-frequency neighbor list of neighbor cells intended to be measured including neighbor cells satisfying an alignment condition and a sufficient measurement time. The alignment condition is satisfied when subframes of a first signal having a first frequency transmitted via a reference cell associated with the user equipment are synchronized with, have a known offset relative to or have a random offset smaller than one half of a sub frame relative to corresponding subframes of a second signal having a second frequency transmitted via a neighboring cells. The sufficient measurement time is determined by an overlap of measurement gaps and positioning subframes in the second signal. The user equipment performs the inter-frequency Reference Signal Time Difference (RSTD) measurements during measurement gaps.