The embodiments herein relate to a method in a network node (103), a network node (103), a method in a user equipment (105) and a user equipment for handling base sequences in a communications network (100). The network node (103) is configured to communicate with a first user equipment (105). The network node (103) comprises information about a default base sequence and an alternative base sequence. The network node (103) determines (405, 505, 901), for the first user equipment (105), that the alternative base sequence should replace the default base sequence. The network node (103) sends (406, 506, 902) information about the determined alternative base sequence to the first user equipment (105).