There is provided a method and corresponding arrangements for scheduling users with different Guard Interval, GI, length for multi-user transmission in a wireless communication system, where each of the users is associated with a GI length. The proposed technology involves grouping at least a subset of the users into at least two groups according to GI length for transmission in allocated transmission opportunity, TXOP, resources. In this way, by dynamically scheduling at least part of the users for group-wise transmission according to GI length, the spectral efficiency can be improved. The proposed technology allows for higher scheduling flexibility when different users have different GI length requirements.