Embodiments of the invention provide for allocating spectrum in a wireless communication system that supports simultaneously at least a first mode of operation and a second mode of operation. Logic is arranged for determining a proportion of spectrum required for the wireless communication unit to operate simultaneously in both the first mode of operation and the second mode of operation. Logic for allocating spectrum allocates a temporary guard band between a first portion of spectrum for the first mode of operation and a second portion of spectrum for the second mode of operation for use while the wireless communication unit operates simultaneously in the first mode of operation and second mode of operation.